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Qantas747300
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B737NG And A320 Control Protections

Sun Sep 27, 2015 3:15 am

I am fascinated to read the differences between the B737NG and the A320 family of aircraft. While in essence they do the same job, the way they go about it is somewhat different. What I am interested to know more about are the differences between the two aircraft from the role of the pilot. In particular flight envelope protections. I understand the B777 series has some protections, but as far I can see the 737NG does not (only warnings). Is that correct?
 
barney captain
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RE: B737NG And A320 Control Protections

Sun Sep 27, 2015 4:35 am

Quoting Qantas747300 (Thread starter):
but as far I can see the 737NG does not (only warnings). Is that correct?

Correct.

The AB will protect you from failures to the point of catastrophe, while the Boeing will allow you to commit failures - to the point of catastrophe.

This is a can-o-worms and you will hear arguments on both sides claiming superiority.
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77west
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RE: B737NG And A320 Control Protections

Sun Sep 27, 2015 6:00 am

Quoting Qantas747300 (Thread starter):
I understand the B777 series has some protections, but as far I can see the 737NG does not (only warnings). Is that correct?

True flight envelope protection requires fly by wire (FBW) which the 737 does not have.
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AA737-823
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RE: B737NG And A320 Control Protections

Mon Sep 28, 2015 3:51 am

Quoting barney captain (Reply 1):
The AB will protect you from failures to the point of catastrophe,

Depends on the type of catastrophe.
Ask Germanwings.
I had to explain to my un-aviation family members that EVEN the Airbus won't prevent a loony tune from flying a plane into a mountain. He just can't put the aircraft in a stall to do it.
 
Max Q
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RE: B737NG And A320 Control Protections

Mon Sep 28, 2015 7:40 am

The only true flight envelope protection is a competent Pilot.
The best contribution to safety is a competent Pilot.


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apfpilot
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RE: B737NG And A320 Control Protections

Mon Sep 28, 2015 4:31 pm

Quoting Max Q (Reply 4):
The only true flight envelope protection is a competent Pilot.

Truer words were never spoken...

I might add a competent pilot who has final authority over the controls.
Opinions are my own and do not reflect an endorsement or position of my employer.
 
PGNCS
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RE: B737NG And A320 Control Protections

Sat Oct 24, 2015 6:57 pm

Quoting AA737-823 (Reply 3):

Depends on the type of catastrophe.
Ask Germanwings.

Least relevant reply ever. Look, we get you like Boeing, OK? The poster asked about FLIGHT CONTROL PROTECTION differences between the A-320 and B-737.


Barney Captain was most succinct, but I will elaborate slightly. The B-737 will allow you to maneuver it to any attitude possible and will alert you that you have maneuvered inappropriately in some cases (e.g. "Bank Angle"). It is very old school in this regard and shares this philosophy with many other aircraft. The A-320 series (and other Airbus FBW aircraft) places hard limits on the aircraft that it will not allow the pilot to maneuver beyond predefined flight envelope restrictions (e.g. it will enforce a maximum 67-degree bank angle provided you are in Normal Law). The idea is that there are places in the flight envelope that are inherently unsafe to be in and it precludes pilots from going there. I have flown thousands of hours in both aircraft and prefer the Airbus, but some people prefer Boeing. My biggest issues with the B-737 have nothing to do with the lack of FBW or hard envelope protections.
 
LSZH34
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RE: B737NG And A320 Control Protections

Sat Oct 24, 2015 9:24 pm

Quoting apfpilot (Reply 5):


I might add a competent pilot who has final authority over the controls.


I prefer Max Q's version.
 
PGNCS
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RE: B737NG And A320 Control Protections

Sat Oct 24, 2015 11:13 pm

Quoting LSZH34 (Reply 7):

Quoting apfpilot (Reply 5):


I might add a competent pilot who has final authority over the controls.


I prefer Max Q's version.

Neither of which helps the original poster answer his question.
 
Woodreau
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RE: B737NG And A320 Control Protections

Sun Oct 25, 2015 3:10 am

Even with the envelope protections in an Airbus, it is still possible to roll an Airbus inverted (past 67 degrees bank angle.)

You will have to force the aircraft out of Normal Law first. Once it's out of Normal Law you'll be able to roll it inverted.
However, you cannot command the autopilot to do it, you have to do the deed yourself via the side stick.
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Starlionblue
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RE: B737NG And A320 Control Protections

Sun Oct 25, 2015 7:15 am

Quoting PGNCS (Reply 6):
The idea is that there are places in the flight envelope that are inherently unsafe to be in and it precludes pilots from going there

It goes deeper than that. The philosophy behind Airbus flight control is that it allow higher efficiency and safety by aiding the pilot with very accurately trajectory control. It is a more refined tool when it comes to doing the same job. And no wonder. It was developed many years after the 737.

Modern airliners are complex beasts that require a good understanding of their systems to fly. The assumption is that the pilots know the systems and know the procedures, thus ensuring a safe outcome regardless of the equipment. Pilots lacking in the proper training can screw up in a FBW Airbus just as well as they can in a Boeing.

To paraphrase an American fighter pilot who flew the Mig-29 on an exchange program: The Mig-29 can do more or less the same things as an F-15, but it takes more work from the pilot to make it do those things. You might say that 737 can do more or less the same things as a 320, and commercially they are both successes so apparently airlines thing so too. I just think the 320 might have the edge in helping the pilots do the job well.

Quoting Woodreau (Reply 9):

Even with the envelope protections in an Airbus, it is still possible to roll an Airbus inverted (past 67 degrees bank angle.)

You will have to force the aircraft out of Normal Law first. Once it's out of Normal Law you'll be able to roll it inverted.
However, you cannot command the autopilot to do it, you have to do the deed yourself via the side stick.

Barring turning off the PRIM computers, how would you force it out of Normal Law?

[Edited 2015-10-25 00:24:52]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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RE: B737NG And A320 Control Protections

Sun Oct 25, 2015 8:40 am

Quoting Starlionblue (Reply 10):
It goes deeper than that. The philosophy behind Airbus flight control is that it allow higher efficiency and safety by aiding the pilot with very accurately trajectory control.

How does the Airbus flight control provide more accurate 'trajectory' control ?

Quoting Starlionblue (Reply 10):
It is a more refined tool when it comes to doing the same job

More refined, or just different ?
The best contribution to safety is a competent Pilot.


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zeke
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RE: B737NG And A320 Control Protections

Sun Oct 25, 2015 10:00 am

From a pilots perspective it should be next to zero Inconveinence for normal operations on the line. No pilot should ever need to get close to the limits.
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BoeingGuy
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RE: B737NG And A320 Control Protections

Sun Oct 25, 2015 4:14 pm

Quoting Woodreau (Reply 9):
However, you cannot command the autopilot to do it, you have to do the deed yourself via the side stick.

You can't command the autopilot on any Boeing airplane either to exceed 30 degrees bank; Overspeed the airplane; or Stall the airplane (the V/S mode is sort of an exception, but only if you command it do something unrealistic, and it will fail the mode and alert it can't maintain a safe airspeed).
 
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Starlionblue
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RE: B737NG And A320 Control Protections

Mon Oct 26, 2015 6:07 am

Quoting Max Q (Reply 11):
Quoting Starlionblue (Reply 10):
It is a more refined tool when it comes to doing the same job

More refined, or just different ?

If we're comparing 737 to 320, Airbus is definitely more refined. But we're talking two decades of difference in age so it's apples and oranges. For a fairer comparison, you'd have to look at something like 350 vs 787. I don't have much knowledge of either but I bet they're both pretty darned refined. 
Quoting Max Q (Reply 11):

Quoting Starlionblue (Reply 10):
It goes deeper than that. The philosophy behind Airbus flight control is that it allow higher efficiency and safety by aiding the pilot with very accurately trajectory control.

How does the Airbus flight control provide more accurate 'trajectory' control ?

I was talking specifically 320 vs 737. Should have been more clear on that. A computerized FBW aircraft vs a mechanically controlled aircraft that was designed in the 60s at a time when FBW was bleeding edge tech installed only in things like the Apollo CSM and LM.

As I said with the fighter pilot paraphrase, I think you can be just as accurate with a Boeing 737, in theory. However the 320 makes accurate trajectory control easier for the pilot. No need to trim for example. The entire Airbus flight control system in Normal Law is based on accurate trajectory control. The pilot or autopilot commands a roll rate or a load factor. The aircraft then figures out how to achieve it. The pilot does not need to worry about speed differences since the same sidestick command gives the same result every time. Even in manual flight, the "bird" makes life very easy. If you want straight and level you just place the bird level on the horizon.

In extreme cases such as collision avoidance, Airbus definitely makes life easier. Just pull all the way back and you get a maximum performance trajectory change. On a Boeing 737 I'm assuming getting exactly 2.5G load factor immediately on pulling takes much more practice, and is hard to do consistently.

[Edited 2015-10-25 23:15:28]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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zeke
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RE: B737NG And A320 Control Protections

Mon Oct 26, 2015 7:33 am

Quoting Max Q (Reply 11):
How does the Airbus flight control provide more accurate 'trajectory' control ?

It's a C star flight control system, essentially similar to the F/A-18 with gear up. The F/A-18 and. FBW Airbus the pilots sets the trajectory and the aircraft will maintain that. For the Aitbus it means when configuring it can maintain the trajectory (track/FPA) very accurately which gives better flight control performance especially when conducting non precision approaches.
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Max Q
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RE: B737NG And A320 Control Protections

Mon Oct 26, 2015 10:08 am

Quoting Starlionblue (Reply 14):
I think you can be just as accurate with a Boeing 737

Have to agree with that.

Quoting zeke (Reply 15):
It's a C star flight control system, essentially similar to the F/A-18 with gear up. The F/A-18 and. FBW Airbus the pilots sets the trajectory and the aircraft will maintain that

Not discussing F18's.

Quoting zeke (Reply 15):
The F/A-18 and. FBW Airbus the pilots sets the trajectory and the aircraft will maintain that

Any competent Pilot can do the same on a Boeing, manually or with the autopilot.

Quoting zeke (Reply 15):
which gives better flight control performance

What does that mean ?




Better 'flight control performance' seriously ?



How exactly do you measure that ?
The best contribution to safety is a competent Pilot.


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Woodreau
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RE: B737NG And A320 Control Protections

Mon Oct 26, 2015 1:12 pm

Quoting Starlionblue (Reply 10):

Barring turning off the PRIM computers, how would you force it out of Normal Law?

Follow the Airbus provided guidance to disable Normal Law?

The procedure we have been provided is to turn off 2 ADRs. After that point it's all on the pilot and his internal protections on what is acceptable to him or her.

I wouldn't disable the PRIMS/FAC/SEC/ELACS, I consider them pretty vital in being able to hand fly the aircraft.
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zeke
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RE: B737NG And A320 Control Protections

Mon Oct 26, 2015 1:51 pm

Quoting Max Q (Reply 16):
Better 'flight control performance' seriously ?

Yes, it can be shown mathematically/scientifically. When Boeing does replace the 737 is will not feature a mechanical control system, just like the 757/767 replacement.

Quoting Max Q (Reply 16):
How exactly do you measure that ?

Have a look at MIL–STD–1797A, that will give you an idea after you read the 700 odd pages.
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Starlionblue
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RE: B737NG And A320 Control Protections

Mon Oct 26, 2015 3:03 pm

Quoting Woodreau (Reply 17):
Quoting Starlionblue (Reply 10):

Barring turning off the PRIM computers, how would you force it out of Normal Law?

Follow the Airbus provided guidance to disable Normal Law?

The procedure we have been provided is to turn off 2 ADRs. After that point it's all on the pilot and his internal protections on what is acceptable to him or her.

Oops, I forgot about the inputs to the computers. Myopia...

Quoting Woodreau (Reply 17):
I wouldn't disable the PRIMS/FAC/SEC/ELACS, I consider them pretty vital in being able to hand fly the aircraft.

Quite.  Flying on mechanical backup is... challenging to say the least.

[Edited 2015-10-26 08:21:47]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Max Q
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RE: B737NG And A320 Control Protections

Tue Oct 27, 2015 6:54 am

Quoting zeke (Reply 18):
Yes, it can be shown mathematically/scientifically. When Boeing does replace the 737 is will not feature a mechanical control system, just like the 757/767 replacement.
Quoting zeke (Reply 18):
Have a look at MIL–STD–1797A, that will give you an idea after you read the 700 odd pages.

You stated the AB has better 'flight control performance' but you don't seem to be able
to explain that statement.



I would say that 'better' is subjective but you have not clarified what you meant, it can't be that
difficult for you can it ?
The best contribution to safety is a competent Pilot.


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zeke
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RE: B737NG And A320 Control Protections

Tue Oct 27, 2015 10:26 am

Quoting Max Q (Reply 20):
You stated the AB has better 'flight control performance' but you don't seem to be able to explain that statement.

I would say that 'better' is subjective but you have not clarified what you meant, it can't be that
difficult for you can it ?

It is not a one line answer, if you read the 700 pages of that MIL-STD you will understand why. Every aircraft control system be it mechanical or FBW can be represented as a control system diagram, with transfer functions that can see the response of the aircraft (such as a root locus plot) given an input such as a gust or control input. From that the control system engineer can qualify control system performance, and you can measure the margins you have in normal and non normal situations.

The C* (C Star) flight control system originated from the requirements in the Tactical Fighter Experimental (TFX), it was specifically designed for short term maneuvering. Boeing has test flown the control system on the 367-80, 707, and 757. C* variations can be found on the F-16, F/A-18, Concorde, Space Shuttle, Airbus FBW, 777, 787, C series, and many business jets. Adding C* variation to FBW allows the control system engineer also to add variations to the control system which would not be possible or very difficult with a mechanical control system. Examples of this would be the automatic reconfiguration of the flight control system with abnormalities, automatic engine failure detection and control input, secondary functions of the flight control system for variable camber, variable lift distribution, dual use of flight control surfaces, spoilers, and high lift devices, and aeroelastic dampening.

FBW also allows system gains to be modified so that the feel and response of the aircraft is consistent across models, thrust, and weights. This is not something one would associate with the differences between the 737-100 and the 737MAX, significantly different piloting techniques would be employed as the feel and response of the two vary so much with the difference in weights and thrust. In contrast the 787 and 777 even though they could be 4-5 times an empty 737 weight difference have similar handling characteristics by design.

The A320 flight control system is better than the 737, it is the modern standard found on most large aircraft certified these days, it is C* based ( i.e. specifically designed for short term maneuvering). Many people who are misguided by control systems only see limits and protections in FBW as being a problem.

Most pilots will never come close to needing to fly an airliner to control system limits in their entire career. When experiments have been conducted with pilots such as the IFALPA GPWS terrain avoidance (and the experiment was known in advance to the pilots), aircraft with control system protections still provided more consistent response in an escape than unprotected aircraft. I would suggest with the addition of a startle factor in a real lift unknown even it could be a life saver.

Another factor that many people are not willing to acknowledge is that even mechanical flight control systems have limiters (eg rudder travel limiters) and control surface lockouts (eg ailerons) in them, yet they think they still have full authority over the aircraft despite having control systems being locked out or limited. If a control surface is locked out by the mechanical control system, no pilot can control it.

For day to day operations control protections/ lockouts/ limiters are not noticeable by line pilots.
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Max Q
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 6:00 am

Quoting zeke (Reply 21):
When experiments have been conducted with pilots such as the IFALPA GPWS terrain avoidance (and the experiment was known in advance to the pilots), aircraft with control system protections still provided more consistent response in an escape than unprotected aircraft

And that's the major problem with the AB 'protections' and hard limits.



Pilots assume these 'safety nets' will always work and will always be there but as systems fail or degrade
and you are left with a basic aircraft its easy to forget that you have to go back to using basic airmanship
again.


In other words, be a Pilot, in the AF 447 case a momentary iced over pitot system led to a number of degradations
in the flight control system and those 'protections' were all lost.



The Pilots simply could not comprehend that however and, for the most part just kept pulling back on the stick
despite being in a fully developed stall they could not understand that AB 'magic' was gone and they needed
to just fly a regular stall recovery.



With an AB you need to learn how differently the aircraft flies in three different laws, Normal, Alternate and Direct.
In effect, an aircraft with three personalities.


No such issue on a Boeing, what you see is what you get.



Better 'flight control peformance ?' I don't think so, needlessly complicated certainly.
The best contribution to safety is a competent Pilot.


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zeke
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 7:54 am

Quoting Max Q (Reply 22):
In other words, be a Pilot, in the AF 447 case a momentary iced over pitot system led to a number of degradations in the flight control system and those 'protections' were all lost.

That is a false statement. There is significant difference between a GPWS escape maneuver and mishandling an aircraft in cruise. There are no protections that will prevent a pilot from mishandling an airliner, Boeing or Airbus.

Before you start preaching to everyone about control systems, readers should be aware that you only operate antediluvian platforms without FBW. The same control inputs applied to an antediluvian platform as AF447 would have resulted in a in flight breakup.

Quoting Max Q (Reply 22):
The Pilots simply could not comprehend that however and, for the most part just kept pulling back on the stick despite being in a fully developed stall they could not understand that AB 'magic' was gone and they needed to just fly a regular stall recovery.

Again that is a false statement, all the pilots needed to do is to maintain the same/similar pitch attitude and thrust setting and the aircraft would have maintained close to level. That is the written procedure in the QRH. There is no requirement ever to apply full back-stick in cruise at altitude, even for a TCAS avoidance maneuver.

Quoting Max Q (Reply 22):
With an AB you need to learn how differently the aircraft flies in three different laws, Normal, Alternate and Direct. In effect, an aircraft with three personalities.

Boeing has the same, just with different names, e.g. normal and secondary. As I mentioned above every aircraft be it mechanical or FBW control system can be represented with transfer functions, how the aircraft behaves with control inputs with full/partial flight control system (laws) are given names by those engineers. Even the antediluvian platform you operate has different laws following different failures, however your manuals do not make you aware of those changes. The A350 has the autopilot available even in direct law, even with the total air data. The flight control system will operate from the engine FADEC providing air data to the flight control system.

Quoting Max Q (Reply 22):
No such issue on a Boeing, what you see is what you get.

That is not true. Any pilot on a Boeing will acknowledge that Boeings do not handle exactly the same following failures. That is the whole reason for type rating training to expose pilots to different handling techniques following failures.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
Max Q
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 9:35 am

Quoting zeke (Reply 23):
That is a false statement. There is significant difference between a GPWS escape maneuver and mishandling an aircraft in cruise. There are no protections that will prevent a pilot from mishandling an airliner, Boeing or Airbus.

Exactly my point.

Quoting zeke (Reply 23):
Before you start preaching to everyone about control systems, readers should be aware that you only operate antediluvian platforms without FBW. The same control inputs applied to an antediluvian platform as AF447 would have resulted in a in flight breakup.

No preaching, just highlighting some salient facts, one of those is that Pilots would never have made the same mistakes in an 'antediluvian' Boeing aircraft as it would have been patently obvious the aircraft had stalled.


BOTH control yokes would have been in the full aft position making the aircraft energy state instantly obvious, there would have been no doubt as to what was happening and the recovery procedure to follow.

Quoting zeke (Reply 23):
Again that is a false statement, all the pilots needed to do is to maintain the same/similar pitch attitude and thrust setting and the aircraft would have maintained close to level.

Yes, but that's not what this crew did.

Quoting zeke (Reply 23):
There is no requirement ever to apply full back-stick in cruise at altitude, even for a TCAS avoidance maneuver.

Then why did they do that ? You are highlighting my point. if they did not realize they were no longer in normal law
they would have no reason to think they couldn't apply full back stick without stalling the aircraft.



In a Boeing, no matter how old or new that mentality simply doesn't exist as, even with FBW you can still override soft protections and can stall the aircraft. You have no reason to think the aircraft will 'protect' you.

Quoting zeke (Reply 23):
Boeing has the same, just with different names, e.g. normal and secondary. As I mentioned above every aircraft be it mechanical or FBW control system can be represented with transfer functions, how the aircraft behaves with control inputs with full/partial flight control system (laws) are given names by those engineers. Even the antediluvian platform you operate has different laws following different failures, however your manuals do not make you aware of those changes

No, its simply not the same as the AB with its hard limits and completely different behaviour depending on what law you are in. An aircraft that truly has different personalities.

Quoting zeke (Reply 23):
That is not true. Any pilot on a Boeing will acknowledge that Boeings do not handle exactly the same following failures. That is the whole reason for type rating training to expose pilots to different handling techniques following failures.

I've had several different failures over the years on my Boeing, none resulted in radically different handling, flight control characteristics or needing to think completely differently about the way I flew the aircraft as we were now operating in a different 'law'


And that's going back to the B727, another superb Boeing , on that aircraft you could lose all hydraulics and still control the aircraft with manual reversion, it was VERY heavy on the controls and often took two Pilots on the controls but it still did what you told it to, no extra 'interpretation' required.



Not something you would value of course, no keyboards or even more alarming, no hard limits..
The best contribution to safety is a competent Pilot.


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airmagnac
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 10:27 am

Max, I just can't reconcile these 2 statements :

Quoting Max Q (Reply 4):
The only true flight envelope protection is a competent Pilot.
Quoting Max Q (Reply 22):
Pilots assume these 'safety nets' will always work and will always be there but as systems fail or degrade and you are left with a basic aircraft its easy to forget that you have to go back to using basic airmanship
again.

On the one hand you're implying that human pilots have the ability to handle the highly dynamic, highly unusual, second-by-second decision making involved in flying near the edge of the envelope without losing control. Which is saying that pilots have abilities way beyond those of normal human beings.
On the other hand you are saying that (qualified) pilots are not able to remember the rather very simple idea that "alternate law = normal law without envelope protections". That's basically saying that human pilots are irretrievably stupid idiots....

You can't have it both ways

Quoting Max Q (Reply 22):
The Pilots simply could not comprehend that however and, for the most part just kept pulling back on the stick despite being in a fully developed stall they could not understand that AB 'magic' was gone and they needed to just fly a regular stall recovery.


If I'm getting this right, your explanation is that an Airbus somehow induces extreme stupidity in the pilots sitting in its cockpit ?!?

I'm afraid the obvious bias in your "explanation" of AF447 is as pathetically ridiculous as a post by NAV20/30...


Quoting Max Q (Reply 22):
With an AB you need to learn how differently the aircraft flies in three different laws, Normal, Alternate and Direct. In effect, an aircraft with three personalities.

That would be uncertifiable. Yet it has been accepted on 4 different Airbus aircraft development programs by authorities and airlines all around the world. Go figure...


However, your insistence on having competent pilots is not so contradictory to FBW as you seem to think. The best way to get out of trouble is to avoid getting into trouble in the first place. The best way to do that is to plan ahead and make long-term decisions which will keep you clear of situations which might bring you near the edge. That's a job for human pilots, who have the capability of long-term planning taking into account a myriad of "what ifs ?".
However it happens ever so often that even with the best of intentions, pilots find themselves near the edge. As I said above, in such a dynamic, stressful situation requiring accurate control in the very short-term, a computer is much better suited for the task.
So let me correct your statement to "The only true flight envelope protection is a combination of competent pilots and automatic envelope protection".



Quoting Max Q (Reply 16):

What does that mean ? Better 'flight control performance' seriously ? How exactly do you measure that ?

As a transport pilot your main interest is to control the trajectory that will get you from A to B. However, the airplane does not know what a trajectory is, it only responds to a distribution of forces which will make it move. The aim is therefore to modify the distribution of forces around the airplane to achieve a movement along the desired trajectory, and this is what is done by moving control surfaces. IOW you have to "translate" a trajectory target into a set of coordinated surface deflection commands.

The problem is that in contrast to bikes, cars or other ground vehicles, this translation depends on many things : aircraft geometry, number and location of control surfaces, aircraft natural aerodynamic modes, aircraft structural modes, current air flow conditions (IAS + AOA + sideslip), current attitude, etc...All of which will also evolve during the maneuvering, making the calculations even more complicated.
It actually all boils down to repeatedly solving a set of equations every few fractions of a second, using fixed constants (geometry) or measured feedback (speed for example)
Historically this is indeed managed well enough by human pilots, but using a number of simplifications in the design of the machine (limit number of surfaces, limit structural flexibility...) and in the training of pilots. I did not learn to solve all the relevant equations during flight training, I just learned how to properly turn in a veriety of sub-cases : flying low & slow, low & fast, high, climbing, etc...
Pilots can learn to take wind effects into account, and with experience get a feel for their aircraft's behavior. But for all the other factors, we need to simplify and add margins. Which in the end comes to costs.

In contrast, a bunch of computers with models of the aerodynamics & structure, direct measurements of the variable factors, and a a feedback loop, can just solve the equations in real-time.
No big simplifications, margins can be reduced => lower costs. And the pilot can concentrate on managing his trajectory, which is his main job after all.

That's really all there is to it. Unless of course you really want to argue that each time your moving that yoke, you are thinking about the combination of phugoid and spiral mode effects + structural deformation you are about to create, how those affect your planned trajectory change and how you can compensate the effects...
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David L
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 10:45 am

Quoting Max Q (Reply 24):
BOTH control yokes would have been in the full aft position making the aircraft energy state instantly obvious, there would have been no doubt as to what was happening and the recovery procedure to follow.

   It's only in the internet version that the stick was "held fully back". The accident report indicates otherwise but, after all this time, you still seem to favour the internet version.

Quoting Max Q (Reply 24):
if they did not realize they were no longer in normal law
they would have no reason to think they couldn't apply full back stick without stalling the aircraft.

One of the first things spoken after the loss of reliable airspeed data was that they were in Alternate Law and, therefore, "no protections".

Quoting Max Q (Reply 24):
Then why did they do that ?

A multitude of possible reasons is covered in the accident report. There was a whole lot more to it than simply how the controls were manipulated.

Airbus FBW has been in airline service for 27-odd years now with similar numbers entering service as Boeing over the same time. Where's the evidence that Airbus is less safe? "I would imagine that..." doesn't count.

Quoting airmagnac (Reply 25):

   Different class.  
 
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Starlionblue
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 2:47 pm

Quoting Max Q (Reply 24):
Quoting zeke (Reply 23):
Again that is a false statement, all the pilots needed to do is to maintain the same/similar pitch attitude and thrust setting and the aircraft would have maintained close to level.

Yes, but that's not what this crew did.

Quoting zeke (Reply 23):
There is no requirement ever to apply full back-stick in cruise at altitude, even for a TCAS avoidance maneuver.

Then why did they do that ? You are highlighting my point. if they did not realize they were no longer in normal law
they would have no reason to think they couldn't apply full back stick without stalling the aircraft.

Crews without proper training, or reacting wrongly even with the proper training, are a problem regardless of type. Modern airliners are complex and it takes time and dedication to remain abreast even when qualified on type. Pilots often experience tunnel vision with just normal handflying, let alone emergencies.

The indicators that show you are in Alternate and Direct Laws are drilled in from day one, and are shown right on the PFD. Why was the crew of AF447 apparently not aware of the implications of problem? We might never know.

Quoting Max Q (Reply 22):
With an AB you need to learn how differently the aircraft flies in three different laws, Normal, Alternate and Direct.
In effect, an aircraft with three personalities.

Not really. These "personalities" are not apparent to me. Normal Law makes things easier, but in Direct Law the aircraft still behaves like the same aircraft. It is more sensitive and has no protections, but left stick still rolls left. Certainly the pilot workload increases, but it also does so when going from autoflight to manual flight.

Aerodynamically, the aircraft is still the same.

Quoting Max Q (Reply 24):

In a Boeing, no matter how old or new that mentality simply doesn't exist as, even with FBW you can still override soft protections and can stall the aircraft. You have no reason to think the aircraft will 'protect' you.

This a training issue, not an aircraft issue. Good initial training nowadays has a big focus on highlighting manual handling and law/protection awareness.

[Edited 2015-10-28 08:02:53]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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zeke
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RE: B737NG And A320 Control Protections

Wed Oct 28, 2015 9:28 pm

Quoting Max Q (Reply 24):
Pilots would never have made the same mistakes in an 'antediluvian' Boeing aircraft as it would have been patently obvious the aircraft had stalled.

BOTH control yokes would have been in the full aft position making the aircraft energy state instantly obvious, there would have been no doubt as to what was happening and the recovery procedure to follow.

No pilot should have a certificate if their knowledge is such that they believe the position of the control column correlates to an aircraft energy state. Fact is control columns and moving thrust levers did not save people lives who died in the 737 accident in AMS, or the 777 accident in SFO.

Quoting Max Q (Reply 24):
Yes, but that's not what this crew did.

Same can be said for every human factors accident, i.e. what the pilots in AMS and SFO should have done, and what they did are very different.

Quoting Max Q (Reply 24):
In a Boeing, no matter how old or new that mentality simply doesn't exist as, even with FBW you can still override soft protections and can stall the aircraft. You have no reason to think the aircraft will 'protect' you.

The mentality, or if I may say, the ability to rely on a man-machine interface that can fail is very prevalent on Boeing. There have been fare more accidents on Boeing Aircraft than any other western manufacturer.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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crimsonchin
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RE: B737NG And A320 Control Protections

Thu Oct 29, 2015 1:38 am

Thanks to the usual suspects who are always in threads like this to correct the uninformed nonsense users like the one being replied to are always spouting off in similarly themed threads.

I've been reading this forum for a while before I joined, and almost every thread regarding Airbus flight control philosophies always have the usual kind of people trying to post fictional BS. I can only imagine how much crap would have gone uncorrected over the years, if there weren't people who fly/are knowledgeable about the planes to call out the rubbish.

[Edited 2015-10-28 18:39:51]
 
Max Q
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RE: B737NG And A320 Control Protections

Thu Oct 29, 2015 9:35 am

Quoting airmagnac (Reply 25):
On the one hand you're implying that human pilots have the ability to handle the highly dynamic, highly unusual, second-by-second decision making involved in flying near the edge of the envelope without losing control. Which is saying that pilots have abilities way beyond those of normal human beings.
On the other hand you are saying that (qualified) pilots are not able to remember the rather very simple idea that "alternate law = normal law without envelope protections". That's basically saying that human pilots are irretrievably stupid idiots....

You can't have it both ways

A competent Pilot will ALWAYS be the last line of defense for operating an Aircraft safely, there are no amount of computers or software programs that can compensate for poor piloting.



As an engineer yourself I can see how you fail to understand that Pilots 'in extremis' can resort to habit patterns that are appropriate to an aircraft operating under a different set of control laws, after all that was what they were used to 'all you have to do is pull the stick back, you can't stall' says AB.


They needed to remember they were now flying a conventional aircraft and they didn't, as a result they paid the ultimate price.

Quoting airmagnac (Reply 25):
If I'm getting this right, your explanation is that an Airbus somehow induces extreme stupidity in the pilots sitting in its cockpit ?!?

It's unfortunate and unfair you would characterize these Pilots that way, it certainly wasn't my contention.
My point is that a design that offers countless safety nets and hard limits that are supposed to protect you
at all times can and has induced a false 'sense of security'



When these protections fail you are left with a regular aircraft that can be stalled actions that could not get you in trouble
with the pre-existing 'hard limits' can now kill you and they did.

Quoting airmagnac (Reply 25):
That would be uncertifiable. Yet it has been accepted on 4 different Airbus aircraft development programs by authorities and airlines all around the world. Go figure...

Its never to late to learn from mistakes.

Quoting airmagnac (Reply 25):
However, your insistence on having competent pilots is not so contradictory to FBW as you seem to think. The best way to get out of trouble is to avoid getting into trouble in the first place. The best way to do that is to plan ahead and make long-term decisions which will keep you clear of situations which might bring you near the edge. That's a job for human pilots, who have the capability of long-term planning taking into account a myriad of "what ifs ?".

Completely agree with you to the end of that sentence.

Quoting airmagnac (Reply 25):
However it happens ever so often that even with the best of intentions, pilots find themselves near the edge. As I said above, in such a dynamic, stressful situation requiring accurate control in the very short-term, a computer is much better suited for the task.



That thinking certainly didn't help the AF447 Pilots did it ?


I completely disagree with you there, no computer should limit the authority of the Pilot over his aircraft, no matter what the situation.


The best solution is Boeings utilizing FBW but with 'soft' limits, this still leaves the final authority of aircraft operation with the Pilots.

Quoting airmagnac (Reply 25):
As a transport pilot your main interest is to control the trajectory that will get you from A to B. However, the airplane does not know what a trajectory is, it only responds to a distribution of forces which will make it move. The aim is therefore to modify the distribution of forces around the airplane to achieve a movement along the desired trajectory, and this is what is done by moving control surfaces. IOW you have to "translate" a trajectory target into a set of coordinated surface deflection commands.

The problem is that in contrast to bikes, cars or other ground vehicles, this translation depends on many things : aircraft geometry, number and location of control surfaces, aircraft natural aerodynamic modes, aircraft structural modes, current air flow conditions (IAS + AOA + sideslip), current attitude, etc...All of which will also evolve during the maneuvering, making the calculations even more complicated.
It actually all boils down to repeatedly solving a set of equations every few fractions of a second, using fixed constants (geometry) or measured feedback (speed for example)
Historically this is indeed managed well enough by human pilots, but using a number of simplifications in the design of the machine (limit number of surfaces, limit structural flexibility...) and in the training of pilots. I did not learn to solve all the relevant equations during flight training, I just learned how to properly turn in a veriety of sub-cases : flying low & slow, low & fast, high, climbing, etc...
Pilots can learn to take wind effects into account, and with experience get a feel for their aircraft's behavior. But for all the other factors, we need to simplify and add margins. Which in the end comes to costs.

In contrast, a bunch of computers with models of the aerodynamics & structure, direct measurements of the variable factors, and a a feedback loop, can just solve the equations in real-time.
No big simplifications, margins can be reduced => lower costs. And the pilot can concentrate on managing his trajectory, which is his main job after all.

That's really all there is to it. Unless of course you really want to argue that each time your moving that yoke, you are thinking about the combination of phugoid and spiral mode effects + structural deformation you are about to create, how those affect your planned trajectory change and how you can compensate the effects...

Ok, great speech, is there a point there ?


Here's mine:



The only true envelope protection is a competent Pilot

[Edited 2015-10-29 03:08:05]
The best contribution to safety is a competent Pilot.


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Max Q
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RE: B737NG And A320 Control Protections

Thu Oct 29, 2015 10:03 am

Quoting zeke (Reply 28):
No pilot should have a certificate if their knowledge is such that they believe the position of the control column correlates to an aircraft energy state

True, you should take into account all information and cues, instrument indications primarily but in a situation
like this AF447 crew experienced where there is no doubt they were confused as to the energy state of their
aircraft, linked control columns in the full aft position would have been an additional unmistakable tactile indication
that they were in a stall.



Instead they had two sidesticks that didn't move together and not nearly as instantly visible, this crew, as a result
and in conjunction with their confusion over why the aircraft did not follow their commands as it normally did never
realized they were in a fully developed stall.

Quoting zeke (Reply 28):
Fact is control columns and moving thrust levers did not save people lives who died in the 737 accident in AMS, or the 777 accident in SF

Goes back to having competent Pilots, you can't pilot proof an aircraft.

Quoting zeke (Reply 28):
Same can be said for every human factors accident, i.e. what the pilots in AMS and SFO should have done, and what they did are very different.

Well that's my point, there were significant human factors in the AF447 accident but they were strongly influenced by the design.

Quoting zeke (Reply 28):
The mentality, or if I may say, the ability to rely on a man-machine interface that can fail is very prevalent on Boeing. There have been fare more accidents on Boeing Aircraft than any other western manufacturer.

All man-machine interfaces can fail, its disingenuous to suggest otherwise but failures on a Boeing do not leave with an aircraft that flies completely differently under a whole different set of 'rules'



As to your second, 'statement'



Boeing has been around a hell of a lot longer, since 1916 producing commercial aircraft and the first really successful Jet transport the B707 and all the other superb products since, they were one of the pioneers of the jet age.



Airbus has been around since what 1970 ? they haven't produced nearly the number of aircraft and never had to take those first, perilous steps into jet technology, it was already mature when they appeared on the scene and they didn't
have to take the risks or pay the price of a steep learning curve as Boeing did. If AB had been first and the positions reversed they would have had more accidents.



So your statement is highly misleading, disingenuous and, of course biased towards AB.

[Edited 2015-10-29 03:04:20]

[Edited 2015-10-29 03:06:05]
The best contribution to safety is a competent Pilot.


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BoeingGuy
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RE: B737NG And A320 Control Protections

Thu Oct 29, 2015 2:58 pm

Quoting zeke (Reply 28):
No pilot should have a certificate if their knowledge is such that they believe the position of the control column correlates to an aircraft energy state. Fact is control columns and moving thrust levers did not save people lives who died in the 737 accident in AMS, or the 777 accident in SFO.

This is a an apples to oranges comparison. Moving thrust levers was not the factor in either accident. It was complete loss of situational awareness and lack of airmanship. This is a poor example. It's like saying you you died of diabetes rather than lung cancer, so smoking must not be the cause of deaths.

Quoting zeke (Reply 28):

The mentality, or if I may say, the ability to rely on a man-machine interface that can fail is very prevalent on Boeing. There have been fare more accidents on Boeing Aircraft than any other western manufacturer.

First of all, you can't spell. Secondly, your statement is completely irrelevant. You know there have been far more Boeing airplanes in service, right? How many Airbus airplanes were there flying in the 1960s?
 
Pihero
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RE: B737NG And A320 Control Protections

Thu Oct 29, 2015 8:29 pm

Very interest(ing thread on a longt dead beaten horse !

Quoting BoeingGuy (Reply 32):

This is a an apples to oranges comparison. Moving thrust levers was not the factor in either accident.

You are talking pure rubbish as the general idea against the 'Bus is that moving throttles will keep the crew abreast of the aircraft behaviour and energy state.
They were not *factors* in the accidents... they should hjave prevented them... or did they ?
You can add dozen of other examples which would include a chinese 747 in a spiral dive, a BA 777 at LHR... etc..

Quoting BoeingGuy (Reply 32):
First of all, you can't spell.

Funny remark in an international forum... which makes me wonder whether you could write one single word of Zeke's tongue... Typical arrogance ?

Quoting Max Q (Reply 31):
Quoting zeke (Reply 28):
Fact is control columns and moving thrust levers did not save people lives who died in the 737 accident in AMS, or the 777 accident in AF Airlines (Argentina)">SF

Goes back to having competent Pilots, you can't pilot proof an aircraft.

Quoting zeke (Reply 28):
Same can be said for every human factors accident, i.e. what the pilots in AMS and SFO should have done, and what they did are very different.

Well that's my point, there were significant human factors in the AF447 accident but they were strongly influenced by the design.

That is a very accurate extract of your argument, Max.
Either you respond to Zeke's comments or you just have to let go, because you're not bringing anything to the thread, except some rather hard feeleings about A and B products that cannot be compared.
Secondly, I notice that your only main argument is about AF 447, which is probably the heaviest-posted subject on A.net ana which I have studied at length and to a great detail.
And, of course, you are trying to force your argument. And you fail because you do noy see that that this accident is very exactly what Lutat and Ryan Swah have described in their book : "Automation Airmanship" as the sixth principle : "Situational and Mode awareness", and no longer simple SA.
It wouldn't take very long to see similar erroneous mindsets in a lot of accidents / incidents involving non A types.
The bigger problem is now that quite a lot of people have got their noses twisted in a big way just because the A320 family is now the most numerous in airlines' services and very soon to overtake the number of sold 737s of all types , this with a 20-year shorter period.
I easily understand that could rank.

On the other hand, B products are - in your view, at least - totally blameless, the mishaps being due to non-*competent pilots* : The 727 which you rate so high was such a death trap that they had to change the final flap setting... was rejected by the British certification authority without a stick pusher...
I find it very hard to agree with you.

Quoting crimsonchin (Reply 29):
The best solution is Boeings utilizing FBW but with 'soft' limits, this still leaves the final authority of aircraft operation with the Pilots.

On this subject,you could profit a great deal on the 787 windshear / ground avoidance procedure. Quite interestring. You could learn a bit.
Contrail designer
 
BoeingGuy
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RE: B737NG And A320 Control Protections

Fri Oct 30, 2015 3:45 am

Quoting Pihero (Reply 33):

Quoting BoeingGuy (Reply 32):

This is a an apples to oranges comparison. Moving thrust levers was not the factor in either accident.

You are talking pure rubbish as the general idea against the 'Bus is that moving throttles will keep the crew abreast of the aircraft behaviour and energy state.

First of all, I wasn't talking rubbish. I was responding to what I felt was the other poster talking rubbish. Nowhere did I say something like Airbus' non-moving throttles didn't prevent an accident or anything like that.

Quoting Pihero (Reply 33):
Quoting BoeingGuy (Reply 32):
First of all, you can't spell.

Funny remark in an international forum... which makes me wonder whether you could write one single word of Zeke's tongue... Typical arrogance ?

Actually I was a bit offended by his posting and don't feel I was the one being arrogant. Was my comment appropriate? No, probably not. But I was a bit annoyed.

I can't speak more than a few words of his native tongue, but my girlfriend is a native Chinese speaker, so I bet she could.

Quoting Pihero (Reply 33):
The 727 which you rate so high was such a death trap that they had to change the final flap setting... was rejected by the British certification authority without a stick pusher...
I find it very hard to agree with you.

The 727 was hardly a death trap. The Electra had a shaky beginning but ended up being a very safe reliable airplanes. How many airplanes had Airbus rolled out by 1963? There was a still a big learning curve in safety back then.

In fact, I just looked at the statistics as of 12/31/2013. The 727 has a lower accident rate than the A330, and much lower than the A310.

Quoting Pihero (Reply 33):
On this subject,you could profit a great deal on the 787 windshear / ground avoidance procedure. Quite interestring. You could learn a bit.

I'm familiar with the Non-Normal Maneuver section of Boeing FCOMs. I'm not aware that the procedures for a Windshear warning or Pull Up warning are any different for the 787 as any other Boeing model. It's not rocket science.
 
Max Q
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RE: B737NG And A320 Control Protections

Fri Oct 30, 2015 5:04 am

Quoting Pihero (Reply 33):
That is a very accurate extract of your argument, Max.
Either you respond to Zeke's comments or you just have to let go, because you're not bringing anything to the thread, except some rather hard feeleings about A and B products that cannot be compared.
Secondly, I notice that your only main argument is about AF 447, which is probably the heaviest-posted subject on A.net ana which I have studied at length and to a great detail.
And, of course, you are trying to force your argument. And you fail because you do noy see that that this accident is very exactly what Lutat and Ryan Swah have described in their book : "Automation Airmanship" as the sixth principle : "Situational and Mode awareness", and no longer simple SA.

No shortage of people attempting to force their argument on this forum Ph.



Not my intention though, I have responded to Zeke's comments, though not in a manner he cares for.
We have fundamental differences that are not likely to change regarding automation and human factors
between A and B.


C'est la vie.

Quoting Pihero (Reply 33):
On the other hand, B products are - in your view, at least - totally blameless, the mishaps being due to non-*competent pilots* : The 727 which you rate so high was such a death trap that they had to change the final flap setting... was rejected by the British certification authority without a stick pusher..

That is an exaggeration you know not to be true, every aircraft has its faults the 727 included although I certainly
wouldn't call it a 'death trap' It was very unforgiving at low altitude with a high sink rate, especially for Pilots coming off
piston transports used to immediate engine response.



The final flap setting, was changed to 30 from 40 degrees for most operators due to this but it wasn't mandated, we used flaps 40 on the 727 for years in the Air Micronesia operation and other operators did as well.


No death trap, you just had to be aware of the aircraft's characteristics, like all types.


No other aviation authority in the world insisted on a stick pusher for the B727, it wasn't necessary as proven by flight testing but BEA had experienced a deep stall in a trident resulting in a fatal crash, along with a deep stall during 1-11 testing also resulting in a crash, as you know these were both T-Tail types and after these two accidents the CAA were very leery of this design and insisted on a stick pusher for the similar design of the 727.



It was an early design, as was the 707 and there were a lot of accidents, as there were with all the early generation jet transports, it took quite a bit of experience to get to the level of safety we have today, Dehavilland, Boeing and Douglas were true pioneers in that respect and suffered many more accidents as a result, its disingenuous and misleading to suggest that Boeing has a worse accident record than Airbus because of this, they started making aircraft fifty four years before Airbus !
The best contribution to safety is a competent Pilot.


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TheRedBaron
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RE: B737NG And A320 Control Protections

Fri Oct 30, 2015 7:37 am

Quoting Pihero (Reply 33):
Very interest(ing thread on a longt dead beaten horse !

Nice to see you ! This thread reminds me of auto forums, what is better BMW or AUDI....

BTW one of my friends (who is now a F/O on the A380) told me a few weeks ago he would give anything to fly the 722, guess some old timers like me who like analog era stuff, have a hard time letting go....

Regards

TRB
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zeke
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RE: B737NG And A320 Control Protections

Sat Oct 31, 2015 8:56 am

Quoting Max Q (Reply 35):
I have responded to Zeke's comments, though not in a manner he cares for.

You have not responded to my comments at all.

To summarize your posts above when it is an Airbus accident, your posts say it is the Airbus technology that is at fault (which you have no experience with). When it is an Boeing accident it is a fault with the pilots.

You state that pilots only get confused on Airbus aircraft, that is false.
You state that only competent pilots are relevant, that is false. On a daily basis pilots often with years or even decades of experience mishandle aircraft regardless of who makes them.

You clearly do not know the what is involved in obtaining an Airbus type rating or systems when you make comments like "'all you have to do is pull the stick back, you can't stall' says AB" and "not the same as the AB with its hard limits and completely different behaviour depending on what law you are in. An aircraft that truly has different personalities". Airbus goes to great lengths to tell new pilots onto the types of the golden rules, the key being it is just another aircraft, you can stall it, you can crash it, you can run off the end of the runway, it can fail.



Your theoretical knowledge of flight control systems and human factors displayed in this thread is very simplistic (well below the standard required by other states), which is common for people with FAA certificates. All aircraft (that includes Boeing's) do fly under a "different set of 'rules'", and this can be expressed mathematically with transfer functions to model the aircraft with the failures. Aircraft actually fly with a different set of rules following any configuration or flight control change, and control system engineers actually do model and measure that behavior.

I have gone to some length to describe the C* flight control systems history and why it is better, and provided the MIL-STD on how that can be measured/quantified. I have also described how every flight control system, regardless of it is mechanical or FBW can be represented mathematically. The system performance can be measured.

Airbus flight control protections and autothrust modes were never designed to prevent a pilot mishandling an aircraft, it always amazes me when we have topics that can go one for over for 10 plus parts that simply do not understand that. I mentioned above most pilots should go through their entire career never getting close to the protections unless its in the simulator.

Airbus control protections are totally transparent for normal line flying, just like control system limiters and lockouts are transparent on mechanical Boeing types. The flight control protections do not alter the aerodynamics of the airframe which are fundamentally very sound.

The A330 is very stable in cruise, no pilot rated on the A330 will deny that if the pilots of AF447 had done nothing, or just sent close to a normal pitch attitude, with the same cruise thrust setting nothing would have happened (as per the QRH). The aircraft did not fail, it did exactly what the pilots asked of it. After entering the pilot induced upset, again if the pilots had just let go the aircraft natural longitudinal stability would have let the aircraft unstall. Instead the pilots further commanded the remain in the upset to a point where it was no longer recoverable.

There is no statistical basis even with the larger sample size to indicate that "Boeing philosophy" provides any flight safety benefit. If there was a measurable safety benefit, it would show up in the accident statistics.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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airmagnac
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RE: B737NG And A320 Control Protections

Sat Oct 31, 2015 11:41 am

Quoting Max Q (Reply 30):
there are no amount of computers or software programs that can compensate for poor piloting.

No, indeed it cannot undo bad decisions that brought an aircraft in a delicate situation. However it can help prevent said delicate situation from becoming catastrophic.

Look, Airbus flight control automation is not some exceptional unique device.
The idea is that the human operator controls the parameters which actually interest him (in this case, the trajectory), and the machine figures out how to move all the pistons, pumps, fans, valves or whatever control means at its disposal to achieve that target. And as any machine has physical limits, these are programmed into the control software to avoid overstressing the machine.

Take a jet engine : controlling an engine involves adjusting lots of vanes, valves, fuel pumps and what not, with a precise timing, depending on a huge variety of things like atmospheric conditions, aircraft Mach, internal conditions...Are you interested in controlling all that ? No, you just want to turn the things on and get the thrust level appropriate for your needs. So you delegate the local control tasks to a computer (aka FADEC). And I say "you", because you're doing that on your Boeing !
Other example : cabin temperature control. What are you interested in ? The ambient temperature itself, say about 70°F. How is that (generally) achieved ? By adapting a myriad of valves in the packs and the trim air system, maybe also adjusting some electric heaters. And the settings of all these components depend on current temperature level, number of pax, outside temperature, sun radiation exposure and whatever. Do you want to do that complicated job yourself ? Nope, you delegate it to dedicated computers. Again, on Boeings as on any other airliner.

Actually the same principles (including hard limits) are used on all systems of every single airliner developed in the past 30 years. Engines, air conditioning, nose wheel steering, braking, cabin pressure...

Boeing just didn't apply the principle to flight controls, but THAT is the exception.

And beyond airliners, you'll find the same digital-control systems in many every day applications. Ever checked the gas pedal or the brake pedal of your car lately ?


Quoting Max Q (Reply 30):
As an engineer yourself I can see how you fail to understand [...]

Oh because only pilots (sorry, Pilots with a capital 'P') get to hold such knowledge, eh ?  
.

Quoting Max Q (Reply 30):
that was what they were used to 'all you have to do is pull the stick back, you can't stall' says AB.

Aerodynamics 101 : a wing with a given shape will stall at a certain point. An Airbus has wings, therefore it stalls. I'd expect any "competent" pilot (as you call them) to make such a simple reasoning, regardless of what they may be told. And please provide the link to the Airbus training docs that state "you can't stall".

Quoting Max Q (Reply 30):
it certainly wasn't my contention.

Probably not, yet that is the logical conclusion to your arguments.
What you're saying is that Pilots are some kind of all-knowing, all-capable Skygods, reigning on top of the Mount Olympus of "Competence", but that some times accidents happen because some Pilots fall from their perch into the Darkness below.
This happens because
a/ the Pilot chose to fly an Airbus, which is an Evil device created by an engineer Serpent to snare the Pilots from their Kingdom
b/ the Pilot was flying a Boeing, which is The Perfect Steed destined to serve the perfect Pilots, so any Boeing Pilot that falls into the Darkness below must have been unworthy in the first place.

It makes an interesting chapter of a Holy Book of Pilots, but doesn't reflect reality all that well

Quoting Max Q (Reply 30):
That thinking certainly didn't help the AF447 Pilots did it ?

Nobody ever said that envelope limiting was the ultimate solution to end all accidents. What it does do is help in cases on Loss of Contol In flight (and some cases of CFIT), which as per the Boeing graph here
http://icatee.org/wp-content/uploads...CAST-July2010-LOCI-Perspective.jpg

is one of the most frequent type of accidents, and by far the least survivable type.
You can see that AF447 is far from an isolated accident, and cherry-picking it and misrepresenting it will not get you very far. Note that the graph represents the 2000-2009 period, in which all LOC-I cases were on "traditionally controlled" aircraft ; AF447 and QZ8501 happened afterwards.
BTW, as those 2 events demonstrate, hard limits don't even eradicate the problem by themselves. Again, nobody ever claimed they would.

Quoting Max Q (Reply 30):
no computer should limit the authority of the Pilot over his aircraft, no matter what the situation.

Engineers don't insert limits just for fun or because we are all jealous, frustrated wannabe pilots. The limit on authority is due to natural, physical effects. Airliners are meant to be flown straight & level, not upside down, sideways or at high angles of attack. Out of that envelope, they don't fly as well, they don't fly the same, or they don't fly at all.

Quoting Max Q (Reply 30):
Ok, great speech, is there a point there ?

It means that piloting an aircraft is quite complex in reality. And that we have achieved it for a long time by compromising the aircraft designs, and dumbing down the training on how aircraft work, in order to adapt to the natural limitations of a human brain. Good enough for most applications, but when we start flying tens of thousand of trips per day at high speed/high altitude, it starts costing a lot.

Let's use a parallel with the representation of the shape of the Earth.
If you're building a small shed in your garden, or travelling locally within a small town, you can consider the Earth to be flat. It's a good approximation because the involved distances are small compared to the curvature of the planet, and it enables you to use simple navigation or construction tools like a ruler, a plumb line, maybe even just your eyes.

Now if you want to travel of hundreds or thousands of miles, or build an office building, that flat earth approximation becomes increasingly false. You can still use your simple tools, but you're likely to cover more ground or get lost, or you will have to overbuild your building to compensate for the unbalanced forces. If you move to a spherical Earth model, and build more sophisticated instruments adapted to that model (good clocks, sextant, theodolite), the trajectory or buildings can become more adapted, with corresponding savings of ressources.

The model can be refined further to an ellipsoid, which can be useful for applications requiring extreme precision (like building large particule colliders, probably).

The general idea is that there is a trade-off between a combination of simple models + simple tools + simple products, which will cost less upfront but have less operating performance, or more complex models & tools leading to more complex products, which cost more to create but perform better in the long run.
In this case, the representation of how the aircraft interacts with airflows can be made much more sophisticated by implementing them in sophisticated digital software programs rather than a human brain, with resulting improvements in efficiency.

Other point : for a long time, some people clung to their idea of a flat Earth, and dismissed the spherical model...some even rejecting it as heresy. Same old, same old  
My goal as an engineer is to fill my soul with coffee and become immortal
 
Max Q
Posts: 8438
Joined: Wed May 09, 2001 12:40 pm

RE: B737NG And A320 Control Protections

Sat Oct 31, 2015 11:45 am

Quoting zeke (Reply 37):
You have not responded to my comments at all.

To summarize your posts above when it is an Airbus accident, your posts say it is the Airbus technology that is at fault (which you have no experience with). When it is an Boeing accident it is a fault with the pilots.

I have, you just don't like the answers Zeke.



Perhaps you could show me where I said that ?



Your 'summary' is incorrect. Accidents happen with aircraft of all manufacturers, there are design features of certain manufacturers that are better or worse than others. I believe the AB design has some very serious pitfalls that can confuse Pilots leading to fatal consequences as in AF447.

Quoting zeke (Reply 37):
You state that pilots only get confused on Airbus aircraft, that is false.

Once again, kindly show me where I said that ?

Quoting zeke (Reply 37):
You state that only competent pilots are relevant, that is false

No, I said:

Quoting Max Q (Reply 30):
The only true envelope protection is a competent Pilot
Quoting zeke (Reply 37):
On a daily basis pilots often with years or even decades of experience mishandle aircraft regardless of who makes them.

That is the first factual statement you have made in this reply.

Quoting zeke (Reply 37):
You clearly do not know the what is involved in obtaining an Airbus type rating or systems when you make comments like "'all you have to do is pull the stick back, you can't stall' says AB"

Please describe how, in normal law how you can stall the AB when you pull back on the stick ?

Quoting zeke (Reply 37):
and "not the same as the AB with its hard limits and completely different behaviour depending on what law you are in. An aircraft that truly has different personalities".

Once again, enlighten me on how this is an inaccurate statement ?



The most misleading statement of all you put out with your mini AB 'advertisement' is
'the aircraft can be flown like any other aircraft'



Simply not true is it ?


Boeing, Douglas, Lockheed aircraft leave the final control for operation in all phases of flight with the PILOT, no artificial 'hard limit' restrictions limiting their authority were or are built into their flight control and automation systems (excluding your usual argument of yaw dampers etc)


This is NOT the case with the AB so its not really a 'normal' aircraft at all. It would only be considered 'normal' if all other aircraft of all types had the same hard limits.


AB sells these hard limits as a form of 'protection' to pilots with some very dubious outcomes as a result, one of the major major issues being what happens when all these 'protections' this 'cotton wool' around the pilots fails ?


Then you are left with a 'regular' aircraft, one that really does fly like any other and its a bewildering and confusing situation for some AB pilots to be left in, especially in a situation where your primary instrumentation has failed and you are totally unsure what energy state your aircraft is in. Very easy and perhaps even natural to revert back to old habits where you knew you were 'protected' no matter what you did with the stick.

Quoting zeke (Reply 37):
Your theoretical knowledge of flight control systems and human factors displayed in this thread is very simplistic (well below the standard required by other states), which is common for people with FAA certificates.

Sometimes the simple answers are the most accurate and the ones we find hardest to accept.



I can't help you with your xenophobic attitude towards other aviation regulatory authorities than your own, sounds a lot like your attitude towards older aircraft  
Quoting zeke (Reply 37):
I have gone to some length to describe the C* flight control systems history and why it is better, and provided the MIL-STD on how that can be measured/quantified. I have also described how every flight control system, regardless of it is mechanical or FBW can be represented mathematically. The system performance can be measured.

You have not, in any manner described how AB flight control systems are 'better'

Quoting zeke (Reply 37):
Airbus flight control protections and autothrust modes were never designed to prevent a pilot mishandling an aircraft

I could not disagree with you more, , that is EXACTLY what the AB flight control protections were designed to do.



I remember watching an A340-600 do a very low speed fly by at Farnborough a few years ago, the point was made that the Pilot could pull back as hard as he wanted on the stick and it couldn't stall.


I remember thinking at the time 'great, until it doesn't work'



We have all seen now what happens when it doesn't.

Quoting zeke (Reply 37):
it always amazes me when we have topics that can go one for over for 10 plus parts that simply do not understand that. I mentioned above most pilots should go through their entire career never getting close to the protections unless its in the simulator.

I don't doubt that, they do know those limits are there however.
There's a 'safety net' if they push the limits.

Quoting zeke (Reply 37):
Airbus control protections are totally transparent for normal line flying,

Unless landing in gusty winds where you may have to go to the control stops to get close to the response required, just one example where that statement isn't true.

Quoting zeke (Reply 37):
just like control system limiters and lockouts are transparent on mechanical Boeing types.

As you know, that is misleading, control system limiters and lockouts exist on all jet transports, not just Boeing, they do not form part of an all encompassing flight control system with hard limits in all phases of flight.

Quoting zeke (Reply 37):
The A330 is very stable in cruise, no pilot rated on the A330 will deny that if the pilots of AF447 had done nothing, or just sent close to a normal pitch attitude, with the same cruise thrust setting nothing would have happened (as per the QRH).

Agree.

Quoting zeke (Reply 37):
The aircraft did not fail,

Not precisely true, the pitot system iced up providing erroneous airspeed indications to the Pilots, that part of the aircraft did 'fail' that is why all the pitot systems on this model type had to be replaced with systems from a different manufacturer.

Quoting zeke (Reply 37):
it did exactly what the pilots asked of it.

That is correct.

Quoting zeke (Reply 37):
After entering the pilot induced upset, again if the pilots had just let go the aircraft natural longitudinal stability would have let the aircraft unstall. Instead the pilots further commanded the remain in the upset to a point where it was no longer recoverable.

Correct, they did not understand what had happened to their aircraft and despite being in direct law with no protections, flying like you said 'a normal aircraft' they made inputs to the stick that assumed those protections still existed.


All the way down to the Atlantic, simply tragic.


Not altogether incomprehensible however when dealing with an aircraft of multiple 'personalities'

Quoting zeke (Reply 37):
There is no statistical basis even with the larger sample size to indicate that "Boeing philosophy" provides any flight safety benefit. If there was a measurable safety benefit, it would show up in the accident statistics.

There certainly isn't one to show that AB is safer !



I know a lot of Pilots that have flown both and the vast majority prefer Boeing, they like having full control.
Most Pilots value this very highly.
The best contribution to safety is a competent Pilot.


GGg
 
bueb0g
Posts: 656
Joined: Fri Jul 02, 2010 5:57 pm

RE: B737NG And A320 Control Protections

Sat Oct 31, 2015 2:44 pm

Quoting Max Q (Reply 11):
How does the Airbus flight control provide more accurate 'trajectory' control ?

Because that's the whole point of it? FBW allows the pilot to directly control the flightpath/trajectory, as opposed to a cable driven airliner where you indirectly control the flightpath through direct control of the control surfaces.

Quoting BoeingGuy (Reply 32):
This is a an apples to oranges comparison. Moving thrust levers was not the factor in either accident. It was complete loss of situational awareness and lack of airmanship. This is a poor example. It's like saying you you died of diabetes rather than lung cancer, so smoking must not be the cause of deaths.

Nobody ever said moving throttles were a factor. Rather it was a response to the oft-posited theory that moving throttles and controls helps keep Boeing pilots 'in the loop', thus mitigating certain types of accidents.

Quoting Pihero (Reply 33):
You can add dozen of other examples which would include a chinese 747 in a spiral dive, a BA 777 at LHR... etc..

I think I've made this point before but you can't really lump the BA 777 at LHR in there. That is one situation where moving throttles did actually help - the crew only realised the problem as early as they did when they saw the AT continually demanding more power but didn't feel any acceleration and saw the engines weren't responding.

Quoting BoeingGuy (Reply 34):
I can't speak more than a few words of his native tongue, but my girlfriend is a native Chinese speaker, so I bet she could.

Great?

Quoting Max Q (Reply 35):
I have responded to Zeke's comments, though not in a manner he cares for.

You haven't really. Very rarely do you respond directly, you mostly talk around him.

Quoting Max Q (Reply 39):
Please describe how, in normal law how you can stall the AB when you pull back on the stick ?

You can't (theoretically), but that doesn't mean that Airbus goes round telling their crews that low energy states are safe!

Quoting Max Q (Reply 39):
The most misleading statement of all you put out with your mini AB 'advertisement' is
'the aircraft can be flown like any other aircraft'



Simply not true is it ?


Boeing, Douglas, Lockheed aircraft leave the final control for operation in all phases of flight with the PILOT, no artificial 'hard limit' restrictions limiting their authority were or are built into their flight control and automation systems (excluding your usual argument of yaw dampers etc)

It can be flown like any other aircraft, because in *none* of the aircraft you mention here would a line pilot ever want to fly outside the hard limits that Airbus sets. Guess what - the crew has final authority in an Airbus too. Because when a crew is inverted, disoriented, and spiralling at night towards the ground, do you think they want to be there? Which crew *actually* has more flight authority - the crew that is out of control with nothing to help them, or the crew in the aircraft that stopped banking at 67 degrees? Which out of the two has a better chance at completing the flight?

Quoting Max Q (Reply 39):
AB sells these hard limits as a form of 'protection' to pilots with some very dubious outcomes as a result, one of the major major issues being what happens when all these 'protections' this 'cotton wool' around the pilots fails ?

That's a training/pilot problem. Not an aircraft problem. Airbus pilots should not fly around as if they are within a magic safety box at all times, obviously. Nobody says they should. Just like when you're flying your Boeing, you don't go to sleep as soon as you put the AP on, do you? You are right that the best way of maintaining a safe flight path is a competent pilot. That means that no matter what technology you have on board, a safe crew maintains a safe flight path, without relying on that tech.

Quoting Max Q (Reply 39):
I know a lot of Pilots that have flown both and the vast majority prefer Boeing, they like having full control.
Most Pilots value this very highly.

You're absolutely right. Most transport pilots value the ability to roll their aircraft all the way around in cruise, and to conduct a few practice stalls during a line flight very much indeed.
Roger roger, what's our vector, victor?
 
airtechy
Posts: 763
Joined: Sun Dec 24, 2006 7:35 am

RE: B737NG And A320 Control Protections

Sat Oct 31, 2015 10:15 pm

I think the Airbus FBW flight control system is as good as the Boeing FBW system.....until the red lights start flashing.

AF447 had an initial failure with a subsequent recovery that was totally mishandled by the crew leading to a non-recoverable stall. They were partly confused by the stall warning, but nothing will convince me that part of the blame doesn't fall to the Airbus uncoupled control sticks. Either coupled sticks or a coupled yoke provide instant feedback about what the other pilot is doing. This is mentioned in the accident report, but when I pointed out the section I was accused of "cherry picking" the report so you will have to look it up yourself.

AirAsia Flight 8501 had a similar upset in equally bad weather. This is from Wiki so take it for what it's worth....

"A malfunction of the Flight Augmentation Computer (FAC) was persistent enough to cause the captain to take the "very unusual" initiative to pull the circuit breaker for the FAC, cutting power to it a few minutes before the end of the flight. The captain left his seat to access the breaker panel behind the copilot, who was in control of the aircraft at the time.[115] The FAC is the part of the fly-by-wire system in A320 aircraft responsible for rudder control. It had been the subject of maintenance problems on previous flights of this aircraft.[116] The sudden nose-up climbing condition occurred at this time, possibly because of failure of the copilot to respond to the sudden change in control characteristics due to FAC shutdown, which eliminated protection against control inputs that exceed aerodynamic limits.[115]"

The accident report is not out yet, but I think the last sentence speaks to Max's comments.

Since the time they were first installed on aircraft, "autopilots" have been installed in such a way that if they go berserk. ...there is a one button disconnect. It would seem that Airbus is lacking such a feature. One might think it would be handy to return flight control to the pilot in case of a system failure.

They have already recovered the recorders on today's A321 crash so maybe we will know soon if something similar happened.
 
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Starlionblue
Posts: 20034
Joined: Fri Feb 27, 2004 9:54 pm

RE: B737NG And A320 Control Protections

Sun Nov 01, 2015 12:30 pm

Quoting bueb0g (Reply 40):
Quoting Pihero (Reply 33):
You can add dozen of other examples which would include a chinese 747 in a spiral dive, a BA 777 at LHR... etc..

I think I've made this point before but you can't really lump the BA 777 at LHR in there. That is one situation where moving throttles did actually help - the crew only realised the problem as early as they did when they saw the AT continually demanding more power but didn't feel any acceleration and saw the engines weren't responding.

A simple look at the Engine Warning Display display on an Airbus will tell you if supply equals demand.

[Edited 2015-11-01 04:38:00]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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flyingturtle
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RE: B737NG And A320 Control Protections

Sun Nov 01, 2015 1:40 pm

Quoting airmagnac (Reply 38):
Look, Airbus flight control automation is not some exceptional unique device.
The idea is that the human operator controls the parameters which actually interest him (in this case, the trajectory),

I fail to see how this should be bad, for any pilot, on any airplane. An abstraction layer removes details from the pilot's view, allowing him or her to focus on the things that matter. We have this abstraction layers inherent in everything we do. When running, our legs are in Normal Law, but when we kick the ball in soccer, they are in Direct Law. When writing, our hands form the letters in Normal Law, but when drawing minute details, they're in Direct.

David
Reading accident reports is what calms me down
 
WIederling
Posts: 9311
Joined: Sun Sep 13, 2015 2:15 pm

RE: B737NG And A320 Control Protections

Sun Nov 01, 2015 6:48 pm

Quoting Max Q (Reply 31):
Airbus has been around since what 1970

You are aware of the fact that Airbus pedigree goes a tad further back than Boeing?
( i.e. at least as far back as Hugo Junkers initial engine and aerodynamic activities,
not to forget all the other european aircraft manufacturers that finally all met
under the Airbus umbrella.)
.. and that Boeing's step into swept wing jet aircraft was majorly facilitated by
a rich set of research data acquired via operation paperclip and some british
gifts too afaiu ). To note: Boeing Corp. actually had someone at hand who
understood the implications of information gained! )
Murphy is an optimist
 
Max Q
Posts: 8438
Joined: Wed May 09, 2001 12:40 pm

RE: B737NG And A320 Control Protections

Mon Nov 02, 2015 9:34 am

Quoting WIederling (Reply 44):
You are aware of the fact that Airbus pedigree goes a tad further back than Boeing?

Airbus 'pedigree' eh ?


Any European aircraft manufacturer building something with wings before 1970 ?


What nonsense, Airbus was started then as an exclusive multi government sponsored program (unlike Boeing) to compete with what were then the big three American Civilian aircraft manufacturers, Boeing, Mcdonnell Douglas and Lockheed.


It was NOT a merger of all existing European civilian manufacturers despite using resources from various of these companies.


Boeing started as an independent company under that name in 1916, two world wars and fifty four years before Airbus started, they have decades more experience than AB.

Quoting WIederling (Reply 44):
and that Boeing's step into swept wing jet aircraft was majorly facilitated by
a rich set of research data acquired via operation paperclip and some british
gifts too afaiu ). To note: Boeing Corp. actually had someone at hand who
understood the implications of information gained! )

No argument, there, no one comes by knowledge through osmosis but Boeing took that hard won knowledge (after all we fought world war two for it) and developed it into the finest civilian jet transports ever made.
The best contribution to safety is a competent Pilot.


GGg
 
WIederling
Posts: 9311
Joined: Sun Sep 13, 2015 2:15 pm

RE: B737NG And A320 Control Protections

Mon Nov 02, 2015 3:16 pm

Quoting Max Q (Reply 45):
What nonsense, Airbus was started then as an exclusive multi government sponsored program (unlike Boeing) to

And you obviously seem to think that the capabilities associated with that virgin birth condensed from thin air, right?

The idea of Airbus as first a cooperation of independent european entities was born from realising that the rather fragmented landscape in Europe was not able to compete against the advantaged US manufacturers individually.

A path of cooperations, ownership changes, renamings and mergers can be shown for most of the early manufacturers
Now under the umbrellas of EADS/Airbus BAE, Finmechanica .. .

Probably more efficient continuity than McDAC that now names itself Boeing.  
Murphy is an optimist
 
mmo
Posts: 2059
Joined: Thu Apr 18, 2013 3:04 pm

RE: B737NG And A320 Control Protections

Mon Nov 02, 2015 3:49 pm

How much longer is this idiotic thread going to go on?

This is like arguing about apples and oranges. The 320 family is FBW. The 737 is not. There are NO protections on the 737! End of story. We don't need to know the history of FBW, the advantages of trajectory and ad nauseum.

I have flown both Airbus and Boeing 777/787. They are very different approaches to FBW. Neither is better than the other. It's just a different way of doing things.

Let's move on!!!
If we weren't all crazy we'd all go insane!
 
apfpilot
Posts: 742
Joined: Wed Jun 05, 2013 4:19 pm

RE: B737NG And A320 Control Protections

Mon Nov 02, 2015 3:51 pm

Quoting barney captain (Reply 1):
This is a can-o-worms and you will hear arguments on both sides claiming superiority.

Can I borrow your crystal ball one day?
Opinions are my own and do not reflect an endorsement or position of my employer.
 
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crimsonchin
Posts: 565
Joined: Fri Feb 07, 2014 8:16 pm

RE: B737NG And A320 Control Protections

Mon Nov 02, 2015 11:54 pm

Quoting apfpilot (Reply 48):
Can I borrow your crystal ball one day?

It didn't require a crystal ball to predict that. If you've been reading or lurking on this forum long enough, you'd have seen enough of these threads to know how they always end up. And tbf, no one is really claiming superiority here, except one misinformed American poster, which weirdly has always been the norm.

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