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Aircellist
Posts: 1579
Joined: Fri Oct 08, 2004 8:43 am

RE: A380 Load Alleviation Function

 Quoting Max Q (Reply 47):Limiting the range of a flight control surface does not place a hard limit of the flight path of a non AB aircraft, its not the same thing.

Maybe it's my command of English as a second language, maybe it's about me being a musician, not a pilot nor an engineer, maybe it's about me being plain ignorant or stupid, but honestly I can't figure how physically limiting the movement of a surface does not constitute a "hard" limit. Please enlighten me, if you've got a moment.

 Quoting Max Q (Reply 47):Those limits can be exceeded in all respects, airspeed, angle of bank, pitch, g, etc if necessary in all types but AB, a real advantage for Pilots that value having full control of their aircraft.

So, I understand from Zeke (you've not contradicted this part of what he says) that the limits set by AB, which follow certification limits, are there to protect the integrality of the aircraft's cell. I deduct from what you've written that you value the full control of the pilot over the aircraft to the point of being able to bend it or even break it apart, is that correct?

If so, what would be the case(s) where such an ability would be useful?

… I'm curious, but, on the other hand… Maybe I should know better than to intervene between you, guys…
"When I find out I was wrong, I change my mind. What do you do?" -attributed to John Maynard Keynes

Max Q
Posts: 8452
Joined: Wed May 09, 2001 12:40 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 48):If it were "desirable", it would be a certification requirement.

Certification requirements and desirable attributes in transport aircraft are two different things, there are Pilots that desire
full control of their aircraft value and having no hard limits in the aircraft flight path.

And there are Pilots who are less enthusiastic and confident about flying the aircraft manually and value automation highly that prefer hard limits, this is a desirable design for them.

 Quoting zeke (Reply 48):No pilot can override the hard limits in the Airbus, Boeing, Douglas, or Lockheed flight control sys

I realize English is probably not your first language so I'll reiterate, simply reaching the mechanical stop on a flight control surface is not the same as the flight path hard limits in the AB design, in a Boeing if you turn the yoke to the mechanical stop you will initiate a roll and you will continue that roll until you remove the input, in an AB you will reach the maximum bank angle allowed by the flight control system and thats as far as you can go, that is a hard limit.

Perhaps you can't understand this so i've given you a very simple example, a mechanical limit on a flight control surface is NOT a flight path hard limit as in the AB aircraft.

 Quoting zeke (Reply 48):It does, you are way out of your depth here. Moving the flight control to the hard limit results a control response commensurate with the conditions at the time. Maximum control input may in fact produce undesired or unintentional control response. Pilots are taught this early in the flying training when the are shown the effect of using aileron with an impending stall. No control response is unlimited.

Irrelevant to my point and yours.

 Quoting zeke (Reply 48):IFAPLA did tests on GPWS escape maneuvers and found that pilots are unable to control the aircraft flight path as effectively in non Airbus FBW aircraft, and resulted in less the optimum flight path as the pilots overshot the desired path to gain the maximum ground clearance. That was a canned exercise with pilots prepared for the upcoming test. Add the startle factor into the play, the results will be worse.

I'd like to see the report on that.

You mention startle factor, this was a huge issue in the AF447 crash, the Pilots, used to having all these 'protections' in place on their AB did a disastrous job handling what was a pretty minor problem with pitot icing, problem is when you're use to having training wheels on all the time and they're suddenly taken away its easy to overbalance.

AB has done their best to 'pilot proof' their aircraft and it can't be done, worse they have taken Pilots so far out of the loop with their non intuitive design, non linked sidesticks, non moving autothrottles and hard limits that when things fail and Pilots are needed to do some old fashioned flying those skills can be atrophied to the point where they simply can't cope.

 Quoting zeke (Reply 48):What part of the flight control system failed ?

The AB software prevented the ground spoilers and reverse from being activated until it was too late. They certainly did not attempt to deploy spoilers or reverse in flight.

 Quoting zeke (Reply 48):So are you suggesting there have never been a fatal overrun in a Boeing ?

Kindly show us where I said that. You stated :

 Quoting zeke (Reply 44):There has never been an accident that has stated that the certification limits in the flight control system contributed to an accident on an Airbus aircraft.

I merely corrected you by providing an example.

 Quoting zeke (Reply 48):What airliners dont use a air/ground logic in some form ? What does your light twin have the AIR/GND SYS EICAS ? What reverse and spoilers will you get with the AIR/GND SYS inop ?

Irrelevant, in the Warsaw fatal overrun, the NORMAL, operative design of the air ground sensing switch did not allow the crew to select spoilers or reverse.
The best contribution to safety is a competent Pilot.

GGg

zeke
Posts: 15112
Joined: Thu Dec 14, 2006 1:42 pm

RE: A380 Load Alleviation Function

 Quoting Max Q (Reply 51):there are Pilots that desire full control of their aircraft value and having no hard limits in the aircraft flight path.

There is no such aircraft, pilots who think there are lack critical knowledge. Every aircraft has a long list of limits in the AFM and FCOM. They include the certification category, g limits, flight control limits, and airspeed limits.

 Quoting Max Q (Reply 51): in a Boeing if you turn the yoke to the mechanical stop you will initiate a roll

So every time you do a flight control check to the mechanical stop on the ground you roll ?

You have never been in conditions that exceeded the aircraft's performance ?

 Quoting Max Q (Reply 51):in an AB you will reach the maximum bank angle allowed by the flight control system

That limit is the certification limit for any transport category aircraft, every Boeing airliner that I am aware of has the same limit.

 Quoting Max Q (Reply 51):a mechanical limit on a flight control surface is NOT a flight path hard limit

It does, this is where you lack of knowledge on flight control systems is very apparent.

The certification requirement is that at maneuver speed a full deflection of the stick/yoke allows to achieve a roll rate, lets call that rate “pA”. By certification, pA must also be achieved at the design cruise speed.

As controls are more effective at higher speeds, may have undesirable trans-sonic effects, and may results in design loads being exceeded, by certification the manufacturer are permitted to reduce the deflection of the ailerons/spoilers accordingly to achieve that rate (hence the reason why outer spoilers are permitted to be locked out).

As the aircraft speed in increased further, certification only required 1/3 of the pA rate to be achieved.

No airliner permits a pilot to use full control deflections throughout the flight envelope. Some pilots with inferior knowledge may think they do have such control, when in fact there are limited by the control system to ensure that deign loads are not exceeded in normal circumstances.

It is always possible for a pilot to grossly mishandle any aircraft and to exceed certification requirements.

 Quoting Max Q (Reply 51):Irrelevant to my point and yours.

No it was not.

 Quoting Max Q (Reply 51):startle factor, this was a huge issue in the AF447 crash, the Pilots, used to having all these 'protections' in place on their AB did a disastrous job handling what was a pretty minor problem with pitot icing

So why have more aircraft with conventional controls crashed ? Even when normalized by the number of sectors/hours flown ?

 Quoting Max Q (Reply 51):AB has done their best to 'pilot proof' their aircraft and it can't be done, worse they have taken Pilots so far out of the loop with their non intuitive design, non linked sidesticks, non moving autothrottles and hard limits that when things fail and Pilots are needed to do some old fashioned flying those skills can be atrophied to the point where they simply can't cope.

Lots of personal opinion and zero facts. This comes from a person with no type rating on any FBW aircraft, and no Airbus experience.

If it was even remotely close to what you are describing the accident statistics over the last 30 odd years since the A320 has been flying would have showed a measurable trend.

The facts do not match your opinions.

 Quoting Max Q (Reply 51):The AB software prevented the ground spoilers and reverse from being activated until it was too late. They certainly did not attempt to deploy spoilers or reverse in flight.

That is the NORMAL function of the air/ground logic. On your light twin, if the back wheels alone are only in contact with the runway, you will not get ground spoilers or reverse as the air/ground logic requires the correct tilt before they will activate. If that system failed on your aircraft, the aircraft will still think you are in the air.

They did command spoilers and reverse whilst the aircraft was "in flight". The air/ground logic requirements had not been met.

 Quoting Max Q (Reply 51):I merely corrected you by providing an example.

You didn't, there was no failure of the flight control system. It performed as designed/certified.

If the aircraft at Moscow had been a 737, it also would not have been "on ground". Instead of measuring a mass, the 737 uses gear compression for the air/ground logic, which requires sufficient weight on wheels to transition from air to ground. Both types use weight on wheels to transition from air to ground. The reason why the spoilers and reverse did not deploy was there was insufficient weight on wheels.

During the hearing of the AA420 accident, Boeing said they were aware of 9 previous times spoilers failed to activate on the same type during landing.

 Quoting Max Q (Reply 51):Irrelevant, in the Warsaw fatal overrun, the NORMAL, operative design of the air ground sensing switch did not allow the crew to select spoilers or reverse.

That is where you are wrong, The crew did select reverse and spoilers, they were not prevented from selecting them.

The air/ground logic NORMAL safeguards prevented their deployment as designed. There are many examples of failure of air/ground logic in airliners resulting in aircraft accidents, whilst airborne and on the ground. The majority of which are on Boeing airliners e.g. 737 crash on approach in AMS, Jackson Hole B-757 runway overrun.

[Edited 2016-02-07 00:18:15]
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

Max Q
Posts: 8452
Joined: Wed May 09, 2001 12:40 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 52):There is no such aircraft, pilots who think there are lack critical knowledge. Every aircraft has a long list of limits in the AFM and FCOM. They include the certification category, g limits, flight control limits, and airspeed limits.

That is not the same as the hard limits on aircraft flight path built into the AB aircraft, not knowing this is a lack of critical knowledge on your part.

 Quoting zeke (Reply 52):So every time you do a flight control check to the mechanical stop on the ground you roll ?

Do you seriously believe this ?

Once again, goes to a lack of knowledge.

 Quoting zeke (Reply 52):That limit is the certification limit for any transport category aircraft, every Boeing airliner that I am aware of has the same limit.

Its only a limit in an AB, a Boeing will allow the Pilot to exceed this if the Pilot deems necessary, a much better philosophy,
leaving the Pilot with no hard limits.

 Quoting zeke (Reply 52):It does, this is where you lack of knowledge on flight control systems is very apparent. The certification requirement is that at maneuver speed a full deflection of the stick/yoke allows to achieve a roll rate, lets call that rate “pA”. By certification, pA must also be achieved at the design cruise speed. As controls are more effective at higher speeds, may have undesirable trans-sonic effects, and may results in design loads being exceeded, by certification the manufacturer are permitted to reduce the deflection of the ailerons/spoilers accordingly to achieve that rate (hence the reason why outer spoilers are permitted to be locked out). As the aircraft speed in increased further, certification only required 1/3 of the pA rate to be achieved. No airliner permits a pilot to use full control deflections throughout the flight envelope. Some pilots with inferior knowledge may think they do have such control, when in fact there are limited by the control system to ensure that deign loads are not exceeded in normal circumstances. It is always possible for a pilot to grossly mishandle any aircraft and to exceed certification requirements.

None of that long speech changes my point, you are being disingenuous and attempting to mislead by suggesting a hard limit or restriction in a flight control surface is the same as the hard limits imposed on the aircraft flight path by the AB flight control system.

A mechanical limit on a flight control surface is just that, if you put in a roll input on a Boeing, whether it be a moderate or maximum input that roll will continue until the input is stopped by the PILOT, that is not a hard limit on the aircraft or its flight path, completely different from an AB. On an AB the roll will stop at the hard limit imposed by the flight control system. Pretty simple for most people to understand.

 Quoting zeke (Reply 52):So why have more aircraft with conventional controls crashed ? Even when normalized by the number of sectors/hours flown ?

Goes back to my point that you can't understand or accept, you cannot Pilot proof an aircraft.

 Quoting zeke (Reply 52):Lots of personal opinion and zero facts. This comes from a person with no type rating on any FBW aircraft, and no Airbus experience. If it was even remotely close to what you are describing the accident statistics over the last 30 odd years since the A320 has been flying would have showed a measurable trend. The facts do not match your opinions.

Opinions aside the weaknesses in the AB philosophy of isolating the Pilot from the aircraft and encouraging maximum automation at the expense of Piloting skills are coming back to haunt them, as in AF447 and most likely the recent Air Asia crash amongst others.

When things go wrong, you still need a pilot, if you've turned him or her into a keyboard operator with minimal skill cosseted by protections you're in big trouble.

 Quoting zeke (Reply 52):That is the NORMAL function of the air/ground logic

Exactly my point, the NORMAL function of the air / ground logic did not allow the Pilots to activate their reverse or spoilers.
There was no excuse, once again what is considered normal on an AB prevented the pilots from making critical inputs, a lack of control that in that case cost lives.

Incidentally you seem to have some unusual sense of grandeur about the size of aircraft you fly, could you, perhaps be compensating for something else ?
The best contribution to safety is a competent Pilot.

GGg

WIederling
Posts: 9312
Joined: Sun Sep 13, 2015 2:15 pm

RE: A380 Load Alleviation Function

 Quoting Max Q (Reply 51):AB has done their best to 'pilot proof' their aircraft and it can't be done, worse they have taken Pilots so far out of the loop with their non intuitive design, non linked sidesticks, non moving autothrottles and hard limits that when things fail and Pilots are needed to do some old fashioned flying those skills can be atrophied to the point where they simply can't cope.

Today airplanes are designed to be as save as possible as often as possible.

Pandering to cowboy pilots is not a design objective.

From my first statement you can extract a requirement of retraining those pilots
or disqualifying them for the job.

Similar thing to people being unable to accept another UI design deviating from the
one they had initial contact with. Even if this new design is more effective than the
previous one. this is a user education problem and not a UI design problem.
Murphy is an optimist

zeke
Posts: 15112
Joined: Thu Dec 14, 2006 1:42 pm

RE: A380 Load Alleviation Function

 Quoting Max Q (Reply 53):Do you seriously believe this ?

That was a rhetorical question, you said "in a Boeing if you turn the yoke to the mechanical stop you will initiate a roll".

 Quoting Max Q (Reply 53):Its only a limit in an AB, a Boeing will allow the Pilot to exceed this if the Pilot deems necessary, a much better philosophy, leaving the Pilot with no hard limits.

It is a hard limit on any transport category aircraft. Have a look at your AFM Sec.1 page 5 for the limits. Also have a look at the OM where it says to avoid large movements of the controls as it can cause structural failure even below Va.

 Quoting Max Q (Reply 53):disingenuous and attempting to mislead by suggesting a hard limit or restriction in a flight control surface is the same as the hard limits imposed on the aircraft

There is no flight path limit within the certified envelope. If you want to talk about outside the certified envelope, that is nothing any transport pilot is trained or licenced for as it is outside the certification parameters of the aircraft.

 Quoting Max Q (Reply 53):Opinions aside the weaknesses in the AB philosophy of isolating the Pilot from the aircraft and encouraging maximum automation at the expense of Piloting skills are coming back to haunt them, as in AF447 and most likely the recent Air Asia crash amongst others.

Zero facts, just opinion for someone who has an apparent FBW phobia.

How many automation accidents and incidents have there been on Boeing aircraft ?

 Quoting Max Q (Reply 53):Exactly my point, the NORMAL function of the air / ground logic did not allow the Pilots to activate their reverse or spoilers.

That is the NORMAL function of the air/ground logic on any airliner, even a 767. The reason why spoilers and revers did not extend was there was insufficient weight on the wheels.

If the pilots were too fast, with a tailwind, had no spoiler and reverse, the correct procedure is to discontinue the landing and perform a rejected landing.

 Quoting Max Q (Reply 53):There was no excuse, once again what is considered normal on an AB prevented the pilots from making critical inputs, a lack of control that in that case cost lives.

The pilots were not prevented from selecting spoilers or reverse. The air/ground logic works like that on any airliner.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380 Load Alleviation Function

Max,
You are getting deeper and deeper into your bias and prejudice.
For the last two hundred or so exchanges you've had with Zeke, I decided not to intervene, hopingt that you'd find some sort of common grounds ,on which you'd agree.
That hope is now dead and I'd like to pitch.
My turn.

The first thing I'd have to say is that, unfortunately you have absolutely no experience on FBW-equipped aircraft and your bias has prevented you from trying to learn -if only a small bit- about what they've brought to us as professionals. The main aspect is called SAFETY and I'm at a loss to wonder what is wrong with that.
May I just suggest that, although we might enjoy / love / adore the equipment we're using, their main pupose is not to fulfill whatever macho Hollywood trip we coiuld envision, but to carry , safely passengers between two points on the surface of the Earth.

I have been an instructor for 31 years, seen hundreds of pilots at all stages of their careers and I've" never found one - repeat never found one - who overpowered his flight controls... on the other hand I'd seen hundreds I had to teach not to be too shy, but virile and assertive with their control inputs... So that idea of pushing the aircraft envelope is at least erroneous, but very much a rodeo cowboy myth.

 Quoting Max Q (Reply 51):Quoting zeke (Reply 48): IFAPLA did tests on GPWS escape maneuvers and found that pilots are unable to control the aircraft flight path as effectively in non Airbus FBW aircraft, and resulted in less the optimum flight path as the pilots overshot the desired path to gain the maximum ground clearance. That was a canned exercise with pilots prepared for the upcoming test. Add the startle factor into the play, the results will be worse. I'd like to see the report on that.

So here it is :
CFIT avoidance maneuvers on FBW transport aircraft
From the conclusions, page 18 : "From the data gathered in the evaluation, there was not a distinct advantage of the B777 soft limits vs the A320/330 hard limits for CFIT recovery open loop performance.
However, closed loop evaluations showed that the pilots could achieve more consistent performance results as well as achieve target pull out parameters more quickly in the A320/330 than the B777.
"
Even the US ALPA with all their bias recognise the A better set up.
Funny, 24 years later there still are the diehards who've never understood anything and miss the Timotor era.

This is now an FAA paper comparing CFIT avoidance procedures for aircraft with FBW and with conventional flight controls
Don't worry, your beloved Boeings are not there ; it is just a comparison of test results between A319, 20, 21 A330, 340 vs A300s and A310 family. these could have been replaced with 76, 75 and very much the 73 families.
Now if you asked me what I'd prefer...I'd go for modernity.

Finally, LH2904 in Warsaw :
To think that in the same conditions, there exists an aircraft which could have ended differently is pure BS.
The original A320 spoilers and reverse logic is so close to the Tristar's as to be a copy.
-There was a windshear at the landing time : they landed with some 25 kt extra IAS, hence nearly 50 kt GS over the computed LDR.
- The touch-down was nearly 800 m beyond the threshold ( 500m beyond TDZ)
- Due to right Xwind, the pilot countered the drifting tendency with right bank ( end of a forward slip approach)
- As a consequence, the left gear only touched down 1500 m fro the threshold with a GS = 155 kt
- Due to some aquaplaning, the spin-off sensors didn't register any ground speed, delaying the braking for another 4 seconds or some 300 m.
- Unfortunately, there was an embankment at the end of the runway with which they collided, which destroyed the left wing / left gear, caused a fire that killed a pilot and a passenger.
In all my contacts with aviation, I don't knowx of any aircrfat which could have had usage of spoilers and reverse in the same conditions. To say otherwise is tendencious libel.
Contrail designer

Max Q
Posts: 8452
Joined: Wed May 09, 2001 12:40 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 55):That was a rhetorical question, you said "in a Boeing if you turn the yoke to the mechanical stop you will initiate a roll".

That is correct.

 Quoting zeke (Reply 55):t is a hard limit on any transport category aircraft. Have a look at your AFM Sec.1 page 5 for the limits. Also have a look at the OM where it says to avoid large movements of the controls as it can cause structural failure even below Va.

Not the same thing as the flight control imposed hard limits on AB.

 Quoting zeke (Reply 55):There is no flight path limit within the certified envelope

There are times, albeit rare you may need to go outside that envelope.

 Quoting zeke (Reply 55):If you want to talk about outside the certified envelope, that is nothing any transport pilot is trained or licenced for as it is outside the certification parameters of the aircraft.

Pilots over the years have had to operate outside the certified envelope , it can happen.

 Quoting zeke (Reply 55):Zero facts, just opinion for someone who has an apparent FBW phobia.

I think FBW is an excellent system and a real improvement, the way it was introduced on The Concorde and the manner in which it operates on the 777 and 787 is an example of the best in aviation advances, no hard limits allows the Pilots full control, they may never need to go beyond the 'soft limits' but they can if necessary.

 Quoting zeke (Reply 55):How many automation accidents and incidents have there been on Boeing aircraft ?

There have been accidents and incidents on all types, that doesn't change my point.

 Quoting zeke (Reply 55):The pilots were not prevented from selecting spoilers or reverse. The air/ground logic works like that on any airliner.

You can select anything you want, if the system prevents you from activating spoilers and reverse you have a real problem.

Anyway Zeke, you and I are never going to agree on this, we have a fundamental difference of opinion.
The best contribution to safety is a competent Pilot.

GGg

Max Q
Posts: 8452
Joined: Wed May 09, 2001 12:40 pm

RE: A380 Load Alleviation Function

Bias, yes, prejudice no, I have some very firm beliefs about no limits being placed on a Pilots control of their
aircraft, simple as that.
The best contribution to safety is a competent Pilot.

GGg

Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380 Load Alleviation Function

I am all with Zeke on this subject.
The last aircraft where a pilot had complete control over was for me the Nord 262, just after the DC-4.
As soon as the manufacturers added :
- a yaw damper
- an anti-skid
- hydraulics
- locked low speed ailerons
- a rudder travel limiter...
a pilot only had the choice of what's left to him by the engineers.,

To say that you have complete control of an aircraft in which you have hydraulics / feel system / Mach trim / yaw damper / rudder limiter / auto retracting flaps / auto brakes / anti-skid /.... is the closest you'd come to complete dishonesty, both intellectual and professional.

I notice that you've completely ignored my post (' although you've quoted it iun full )... doesn't it reveal not only bias - which you've acknowledged - but also prejudice ( ignoring all the factors of an accident for just one aspect is prejudice ).
Have a look at the 787 stall protection, and hence the windshear-escape maneuver : it really does look like an Airbus and certainly not a 757,767,727,737, and even not a 777.

As I have been on record for the past 20 years to have said that for any manufacturer not to use the Airbus stall protection was criminal, I applaud the change and so should you.

Our profession is about promoting a safe transport vector, not one's own idea of yet another macho trip ( btw, AF's first A380 commercial JFK was captained by a woman )...

I don't know how many years you've got left before you retire. It would be a shame not to have a go at modern equipments.
Contrail designer

hivue
Posts: 2078
Joined: Tue Feb 26, 2013 2:26 am

RE: A380 Load Alleviation Function

 Quoting Max Q (Reply 57):no hard limits allows the Pilots full control,

As a passenger I would claim that, in this day and age, the question before the house should be whether or not this is a good idea. In the cases of AF447 and QZ8501 the aircraft dropped into a degraded law allowing the crew, if not "full control" at least a great deal more control than they normally (no pun intended) have on AB products. That didn't work out too well.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.

Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380 Load Alleviation Function

Instead of providing another Airbus mishap, it is very interesting to note that airplanes without *hard* limits, as loosely defined by Max are not that efficient in preventiung crashes :

Witness the SwiftAir / Air Algérie MD-83 which crashed in Mali / Burkina Fasso inJuly 2014 :

- Pitots iced -up ( apparently no anti-ice selected )
- Sensors send wrong pressure info to the engines (no FADEC, but the old ECU, hence more *control*)
- reduced engines output
- Stall
- Extreme bank
- Dive
- irrecoverable...
- Impact...

That aircraft had all the elements required by Max, even more so as there is basically no hydraulics on the flight controls ( the system is the old trim tab)...
Now tell me the difference in the endings between that macho airplane and an Airbus ?
I would say a great deal of SA and a very assertive piloting would have saved their respective days.
Contrail designer

michi
Posts: 266
Joined: Thu Jul 15, 2004 9:18 pm

RE: A380 Load Alleviation Function

 Quoting hivue (Reply 60): ...the aircraft dropped into a degraded law allowing the crew, if not "full control" at least a great deal more control than they normally (no pun intended) have on AB products.

Some normal protections on Airbus FBW aircraft:

Load factor: +2.5g to -1g (slats retracted; clean aircraft) - +2g to 0g (slats extended)

Bank angle: 67° (60° in high lift config)

Pitch: +30° nose up and -15° nose down

Exceeding those protections is still possible with degraded flight control laws.

hivue
Posts: 2078
Joined: Tue Feb 26, 2013 2:26 am

RE: A380 Load Alleviation Function

 Quoting michi (Reply 62):Exceeding those protections is still possible with degraded flight control laws.

That's precisely my point. More "control" (i.e., ability to do what you want) in a degraded mode.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.

A320FlyGuy
Posts: 283
Joined: Wed May 16, 2012 8:31 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 19):I will give you a simplistic explanation which is not 100% technically correct of how Airbus implemented Load Alleviation Function in the the FBW, however it should provide you with the underlying concept. In this diagram you can see a simplistic 2D spanwise lift distribution in dashed lines, and the lift distribution with LAF activated with the solid line. In response to a simplistic symmetrical gust, both ailerons move in the same direction to reduce the amount of lift being generated in the outboard part of the wing. This reduces the load (bending moment) at the wing root, hence a reduction of load.

For starters, that image is from an article that I wrote for airlinereporter.com - citing your source would be appreciated.

Airbus would have likely applied almost all of the same concepts in their aircraft but the execution would have been a lot easier, since it was essentially code being integrated into the aircraft systems and not a system being added on to an existing design.
My other car is an A320-200

Pihero
Posts: 4318
Joined: Mon Jan 31, 2005 5:11 am

RE: A380 Load Alleviation Function

 Quoting A320FlyGuy (Reply 64): The L-1011-500 was the first aircraft to employ an active control system to improve ride quality and reduce structural loads on the aircraft.

Wrong.
The Mercure ( by Dassault ) was so equipped in 1971. The system was called DARD.
Contrail designer

apfpilot
Posts: 742
Joined: Wed Jun 05, 2013 4:19 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 46):Moog
 Quoting Pihero (Reply 59):The last aircraft where a pilot had complete control over was for me the Nord 262, just after the DC-4. As soon as the manufacturers added : - a yaw damper - an anti-skid - hydraulics - locked low speed ailerons - a rudder travel limiter... a pilot only had the choice of what's left to him by the engineers.,

I think the disconnect in logic between Max Q and Zeke lie in what those limits mean. Do limits exist on almost every aircraft? Yes, however even with those limits there aren't any that can't be overridden to achieve wherever you want to be in the envelope in the application of those limits in the Boeing philosophy. While (and I fully admit I am not as familiar with the Airbus CONOPS) Airbus won't allow you to put the aircraft anywhere in the flight envelope the operators wants.

I heard an analogy once that I think applies here:

Boeing is like an American cowboy. You try to roll the airplane and it will yell at you, tell you that you shouldn't do that (and maybe even break) but it will still let you rip the wings off. Airbus is like the fine polished European professor. It will say you shouldn't try to roll it, it's not a good idea, YOU REALLY SHOULDN"T DO THIS, and then ultimately smack your hand away at a certain limit.

Note this isn't to comment on the superiority of either method, or which one I think is better (although I do have an opinion it is irrelevant to this discussion.)
Opinions are my own and do not reflect an endorsement or position of my employer.

zeke
Posts: 15112
Joined: Thu Dec 14, 2006 1:42 pm

RE: A380 Load Alleviation Function

 Quoting A320FlyGuy (Reply 64):For starters, that image is from an article that I wrote for airlinereporter.com - citing your source would be appreciated.

Unfortunately I was not aware of that. The image came up in a google search directing me to this blog. As you can see there is no copyright information on that page.

https://vamfun.wordpress.com/2012/12/29/l-1011-active-control-system-remembered/active-control-system-lift-distribution/

 Quoting A320FlyGuy (Reply 64):The L-1011-500 was the first aircraft to employ an active control system to improve ride quality and reduce structural loads on the aircraft.

It was by no means the first, Lockheed had it already installed on the C-5. You maybe interested in these papers from 1969, 1975, and 1976
Burris, P. M., & Bender, M. A. (1969). Aircraft Load Alleviation and Mode Stabilization (LAMS) - B-52 System Analysis, Synthesis, and Design. AFFDL-TR-68-161.
Disney, T. E. (1975). “The C-5A Active Load Alleviation System.” AIAA Paper No. 75-991.
Hargrove, W. J. (1976). “The C-5A Active Lift Distribution Control System.”

 Quoting apfpilot (Reply 66): Do limits exist on almost every aircraft? Yes, however even with those limits there aren't any that can't be overridden to achieve wherever you want to be in the envelope in the application of those limits in the Boeing philosophy

The flight envelopes on an Airbus FBW are the same as a Boeing, they are certified to the same regulations. Misinformed pilots think that going beyond the envelope is permitted, it is not. There is no maneuver Boeing has published that would require a pilot to exceed the flight envelope in normal operations.

Any aircraft can be grossly mishandled to result in structural failure, FBW does not prevent that.

 Quoting apfpilot (Reply 66): You try to roll the airplane and it will yell at you, tell you that you shouldn't do that (and maybe even break) but it will still let you rip the wings off. Airbus is like the fine polished European professor. It will say you shouldn't try to roll it, it's not a good idea, YOU REALLY SHOULDN"T DO THIS, and then ultimately smack your hand away at a certain limit.

Misinformed people think that you can roll and airliner and you will do a barrel roll. Sure at lower altitude the performance is different to the cruise. This diagram below explains why you will never be able to perform such a maneuver in normal operations, the aerodynamic capability of the airframe will be reached before the structural limit.

Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

Pihero
Posts: 4318
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RE: A380 Load Alleviation Function

 Quoting apfpilot (Reply 66): I think the disconnect in logic between Max Q and Zeke lie in what those limits mean.

There are no two definitions of those limits. They are inserted in the flight envelope dagrams. They define exactly the values of the maximum load factors ( G limits) depending on speeds / gusts values....
... and of course, we are back to the macho Hollywood cowboy flying a mean macho aircraft vs polished / effeminate professor and student, right ?

Your explanation isn't worth a lot... and the analogy is seriously flawed.

See Michi's post #62.
Contrail designer

apfpilot
Posts: 742
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RE: A380 Load Alleviation Function

 Quoting zeke (Reply 67):The flight envelopes on an Airbus FBW are the same as a Boeing, they are certified to the same regulations. Misinformed pilots think that going beyond the envelope is permitted, it is not. There is no maneuver Boeing has published that would require a pilot to exceed the flight envelope in normal operations. Any aircraft can be grossly mishandled to result in structural failure, FBW does not prevent that.

I'm not talking about certificated limits, I'm talking about what the aircraft can physically do.

 Quoting zeke (Reply 67):Misinformed people think that you can roll and airliner and you will do a barrel roll. Sure at lower altitude the performance is different to the cruise. This diagram below explains why you will never be able to perform such a maneuver in normal operations, the aerodynamic capability of the airframe will be reached before the structural limit.

Again, I'm not talking about legal, certified or even things that would ever happen in real life.

 Quoting Pihero (Reply 68):... and of course, we are back to the macho Hollywood cowboy flying a mean macho aircraft vs polished / effeminate professor and student, right ?

Did you miss the part where I wasn't commenting on one being better than the other? Your assumption is sorely mistaken as I think the Airbus philosophy is preferable in almost every conceivable case. In a past life I worked for an avionics company that made the first Autopilot Certified for general aviation aircraft with Flight Envelope protection. I was a sales guy so I spent many hours trying to convince people that this was a good thing and that the Autopilot wouldn't take over and not let you do a maximum performance decent or turn the aircraft at high bank angles.
Opinions are my own and do not reflect an endorsement or position of my employer.

zeke
Posts: 15112
Joined: Thu Dec 14, 2006 1:42 pm

RE: A380 Load Alleviation Function

 Quoting apfpilot (Reply 69):I'm not talking about certificated limits, I'm talking about what the aircraft can physically do.

No one knows the answer to that, if its outside of the certified limits, good chance it has never been tested.

 Quoting apfpilot (Reply 69):Again, I'm not talking about legal, certified or even things that would ever happen in real life.

Unfortunately there have been a number of contributions on this thread making claims on what aircraft will do, without actually considering if it is aerodynamically possible. No aircraft has unlimited control or performance, every aircraft is limited. Aircraft are not flight tested to maximum aerodynamic or control capability, they are tested for the certification limits. This the initial phase of any flight testing program, establishing the flight envelope. Once its established, further flight testing remains in that envelope.

 Quoting apfpilot (Reply 69):In a past life I worked for an avionics company that made the first Autopilot Certified for general aviation aircraft with Flight Envelope protection.

Was that the DFC90, was thinking of installing it in one of my aircraft ? Looked like a nice piece of kit, waiting on the STC list to be expanded.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

apfpilot
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Joined: Wed Jun 05, 2013 4:19 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 70):Was that the DFC90, was thinking of installing it in one of my aircraft ? Looked like a nice piece of kit, waiting on the STC list to be expanded.

Sure is. I was one of the sales guys when it was launched.

Obviously a bit different from this discussion but as part of the testing we inverted an SR22 to simulate disorientation. Pressed the Straight and Level button and the aircraft nicely and smoothly rolled from inverted into a nose level/wings level attitude.
Opinions are my own and do not reflect an endorsement or position of my employer.

zeke
Posts: 15112
Joined: Thu Dec 14, 2006 1:42 pm

RE: A380 Load Alleviation Function

 Quoting apfpilot (Reply 71):Obviously a bit different from this discussion but as part of the testing we inverted an SR22 to simulate disorientation.

Must have been experimental category at the time. Being certified as a normal category aircraft, it would not have been legal.

 Quoting apfpilot (Reply 71):Pressed the Straight and Level button and the aircraft nicely and smoothly rolled from inverted into a nose level/wings level attitude.

That was one of the features I liked, also the airspeed hold function which is lacking on most GA autopilots but would have saved a number of climb related accidents where aircraft were in pitch hold and in a single pilot operation were momentarily distracted .
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

Jetlagged
Posts: 2564
Joined: Sun Jan 23, 2005 3:00 pm

RE: A380 Load Alleviation Function

 Quoting Max Q (Reply 57):Not the same thing as the flight control imposed hard limits on AB.

Calling them hard limits is rather misleading. It makes it sound like the aircraft hits a physical limit the pilot can't overcome. You can dynamically exceed the limits. I'm sure you aren't suggesting a Boeing pilot would want to exceed envelope limits for any length of time?

For example in roll, normal law will limit an A320's bank angle to 33 deg, but if the pilot holds in a roll demand a bank of 67 deg can be achieved and held. Pitch attitude limits can't be exceeded in steady state, but will be exceeded dynamically if the pilot pulls or pushes hard enough into them.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

Starlionblue
Posts: 20037
Joined: Fri Feb 27, 2004 9:54 pm

RE: A380 Load Alleviation Function

 Quoting Jetlagged (Reply 73):For example in roll, normal law will limit an A320's bank angle to 33 deg, but if the pilot holds in a roll demand a bank of 67 deg can be achieved and held. Pitch attitude limits can't be exceeded in steady state, but will be exceeded dynamically if the pilot pulls or pushes hard enough into them.

The roll limit of 67 degrees is tricky to exceed. IIRC roll rate will automatically decrease as the limit is approached.

However, gusts can do unexpected stuff.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo

apfpilot
Posts: 742
Joined: Wed Jun 05, 2013 4:19 pm

RE: A380 Load Alleviation Function

 Quoting zeke (Reply 72):Must have been experimental category at the time. Being certified as a normal category aircraft, it would not have been legal.

Correct. It was also flown by a trained test pilot. We went public with Cirrus at that time as well to warn off anyone thinking about trying it just because they (think) they can.

 Quoting zeke (Reply 72):That was one of the features I liked, also the airspeed hold function which is lacking on most GA autopilots but would have saved a number of climb related accidents where aircraft were in pitch hold and in a single pilot operation were momentarily distracted .

That was a big thing that spawned the development of that technology (and a number of other things at Avidyne.) We studied GA accidents in depth and tried to create solutions to remedy the causes. That also goes to the traffic systems, and the lightening detection devices.
Opinions are my own and do not reflect an endorsement or position of my employer.
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