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How would an Airbus have reacted in SFO crash?  
User currently onlineeaa3 From United States of America, joined Sep 2007, 1021 posts, RR: 0
Posted (1 year 3 months 2 weeks 5 days 19 hours ago) and read 11398 times:

I realize that this is a question without an answer and I'm not advocating Airbus above Boeing. I'm just wondering how the different flight envelope protection systems would have reacted on Boeing and Airbus aircraft.

We know that the crashed Asiana B777 at SFO was very close to stall speed on final. Given that Airbus aircraft have a different flight envelope protection system that doesn't allow the aircraft to be stalled would an Airbus aircraft have reacted differently to the mistakes that the pilot made on the Asiana B777 at SFO and maintained a higher speed on final.

How slow would the Airbus flight envelope protection system have allowed the aircraft to get on final or is there no difference up until the aircraft stalls.

50 replies: All unread, showing first 25:
 
User currently offlineKarelXWB From Netherlands, joined Jul 2012, 12145 posts, RR: 34
Reply 1, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11314 times:

I don't think anyone can give you a real answer to this. The pilots of the Tripoli A330 crash were able to crash their jet during final approach so it is not impossible to do despite the flight envelope protections.

Quoting eaa3 (Thread starter):
up until the aircraft stalls

During cruise, the stall warning will trigger even before the plane actually stalls but it looks like the warning is different in landing configuration.



Only two things are infinite, the universe and human stupidity. And I'm not sure about the universe.
User currently offlinePHX787 From Japan, joined Mar 2012, 7757 posts, RR: 18
Reply 2, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11173 times:

I don't like the wording of this question at all. I'm not an av expert but I mean, if this was pilot error regarding the air speed, then any plane would have had such an accident.


我思うゆえに我あり。(Jap. 'I think, therefore I am.')
User currently offlineIndianicWorld From Australia, joined Jun 2001, 2992 posts, RR: 0
Reply 3, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11144 times:

Quoting PHX787 (Reply 2):
if this was pilot error regarding the air speed, then any plane would have had such an accident.

I agree. No airplane is foolproof unfortunately.


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5873 posts, RR: 11
Reply 4, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11146 times:

I'm of the opinion that this is NOT a question "without an answer."
The answer is: yes, if the pilots of an Airbus allowed the aircraft speed to deteriorate that closely to the ground, the plane would have crashed.
There's precedent for an Airbus crashing by landing where a runway wasn't, mind you.... waaaaay back in the day. Granted, those were different conditions, but these guys yesterday didn't have time to execute corrective action before they hit.

We like to think that increased automation prevents bad things from happening, and in some cases, it does. But, just as with AF447, which was completely pilot error, the laws are the laws: if you fly a plane into the ground, it will crash.


User currently offlineXT6Wagon From United States of America, joined Feb 2007, 3417 posts, RR: 4
Reply 5, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11143 times:

Yes, no computer can negate the laws of physics. You get ANYTHING low, slow, and idle power like this and its done.

The famous A320 that played lumberjack in the woods instead of flying is a well known example of energy management being important.


User currently offlineAF185 From Hong Kong, joined Sep 2012, 260 posts, RR: 0
Reply 6, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11030 times:

Quoting XT6Wagon (Reply 5):
The famous A320 that played lumberjack in the woods instead of flying

OK, I did laugh to that one 


User currently offlinegarpd From UK - Scotland, joined Aug 2005, 2686 posts, RR: 4
Reply 7, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11007 times:

After several Airbus crashes where the pilots got it too low and/or too slow (A300, A310, A320, A330), I would have thought this question to be entirely irrelevant.
No plane is fool proof. A bad pilot will crash a plane regardless what protections are it place as it is the pilot (contrary to popular belief) that is ultimately in control.


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User currently offlineAirbusA370 From Germany, joined Dec 2008, 253 posts, RR: 0
Reply 8, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 11007 times:

Quoting XT6Wagon (Reply 5):

Exactly. This is similar to the Habsheim A320 crash. Too low, too slow and engines spool up to slow...


User currently offlineseahawk From Germany, joined May 2005, 1134 posts, RR: 0
Reply 9, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 10702 times:

Engines at idle, low and slow - the Airbus engines would not spool up any faster.

User currently offlinebongodog1964 From United Kingdom, joined Oct 2006, 3638 posts, RR: 3
Reply 10, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 10636 times:

In a way protection systems have an adverse effect, people trust and rely on them to the point where the systems cannot cope with the users incompetence. If a pilot can crash a seemingly fully functional 777, I'm sure the protection systems on an A330 wouldn't help either.

User currently offlinemoo From Falkland Islands, joined May 2007, 4021 posts, RR: 4
Reply 11, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 10607 times:

Why were the engines at idle? I always thought that you had a decent amount of power selected precisely because it takes the engines so long to spool back up - you controlled the speed using other aerodynamic devices during approach, but kept the power on incase you do infact need it at a moments notice.

User currently offlinegarpd From UK - Scotland, joined Aug 2005, 2686 posts, RR: 4
Reply 12, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 10506 times:

Quoting moo (Reply 11):
Why were the engines at idle?

Some would say pilot error. But despite the facts being there, apparently it's too soon to say that.

I know what I believe.



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User currently offlineQatarA340 From Qatar, joined May 2006, 1868 posts, RR: 10
Reply 13, posted (1 year 3 months 2 weeks 5 days 18 hours ago) and read 10368 times:

I dont get why planes dont have some sort of sensor to know that the plane is actually TOO low and they have to abort landing. Each plane should have the elevation of the runway, and their own elevation and the geographical coordinates of the runway and then they could tell if the airplane is actually too far, too low, too close to the runway threshold.


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User currently onlineeaa3 From United States of America, joined Sep 2007, 1021 posts, RR: 0
Reply 14, posted (1 year 3 months 2 weeks 5 days 17 hours ago) and read 10210 times:

I realize that you can crash an Airbus plane just as any other. The crash in the forest was, if I remember correctly, because the plane entered flare mode.

However, my question is the following: What would the flight envelope protection system on an Airbus have done if the aircraft slowed down as much as was the case here.


User currently offlineoly720man From United Kingdom, joined May 2004, 6817 posts, RR: 11
Reply 15, posted (1 year 3 months 2 weeks 5 days 17 hours ago) and read 10196 times:

Quoting QatarA340 (Reply 13):

There are enough sensors on an aircraft to say where it is and the crew should be aware of that. And there is the GPWS that will shout "terrain" at the crew if the plane is too low, e.g.

http://www51.honeywell.com/aero/Prod.../Egpws-Home3/Products4/Mark-V.html

but I would expect that wouldn't be turned on for a landing over the sea, because there wouldn't, ideally, be any ground to be worrying about since the crew could see what they were doing and where they were going.

Having the sensors is one thing, but it would appear that the crew got the plane into a flight situation it couldn't get out of (too low, too slow after being too high, too fast. Allegedly) and all the sensors in the world won't solve that.



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User currently offlineKarelXWB From Netherlands, joined Jul 2012, 12145 posts, RR: 34
Reply 16, posted (1 year 3 months 2 weeks 5 days 17 hours ago) and read 10130 times:

Quoting oly720man (Reply 15):
There are enough sensors on an aircraft to say where it is and the crew should be aware of that. And there is the GPWS that will shout "terrain" at the crew if the plane is too low, e.g.

Correct me if I'm wrong, but I thought the GPWS does not work with the landing gear down and flaps deployed.

[Edited 2013-07-08 03:14:38]


Only two things are infinite, the universe and human stupidity. And I'm not sure about the universe.
User currently offlinebongodog1964 From United Kingdom, joined Oct 2006, 3638 posts, RR: 3
Reply 17, posted (1 year 3 months 2 weeks 5 days 17 hours ago) and read 10108 times:

There is a train of thought which suggests that the flightcrews biggest problem was that the unavailability of the ILS left them with a manual approach which they failed to cope with. To me the answer isn't flight protection systems or any other technology. If they can't balance airspeed, engine power and the sink rate satisfactorily on a calm sunny day with good visibility, they probably can't handle the advice given by any warning system. Look at how the crew of AF447 managed to ignore all the Airbus technology, they couldn't even work out that the best way out of a stall is to dive rather than pull up sharply.

User currently offlinescbriml From United Kingdom, joined Jul 2003, 12640 posts, RR: 46
Reply 18, posted (1 year 3 months 2 weeks 5 days 17 hours ago) and read 9866 times:
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Quoting bongodog1964 (Reply 17):
Look at how the crew of AF447 managed to ignore all the Airbus technology, they couldn't even work out that the best way out of a stall is to dive rather than pull up sharply.

Mainly because they totally failed to follow SOP when they lost airspeed indication and then showed appalling lack of airman-ship in not recognising and dealing correctly with a stall.



Time flies like an arrow, but fruit flies like a banana!
User currently offlineairbazar From United States of America, joined Sep 2003, 8493 posts, RR: 10
Reply 19, posted (1 year 3 months 2 weeks 5 days 16 hours ago) and read 9682 times:

Quoting AA737-823 (Reply 4):
We like to think that increased automation prevents bad things from happening, and in some cases, it does. But, just as with AF447, which was completely pilot error, the laws are the laws: if you fly a plane into the ground, it will crash.

Well, but automation would not fly the plane too low, or too slow in the first place. It's humans overriding automation that tends to cause problems   Time to get rid of the pilots  I'm kidding of course but if this was an ILS approach, my suspicion is that there would have been no crash.

Quoting QatarA340 (Reply 13):
I dont get why planes dont have some sort of sensor to know that the plane is actually TOO low and they have to abort landing.

They do, but you're landing so you ignore the "too low, pull up" warnings  


User currently offlineC680 From United States of America, joined Apr 2005, 588 posts, RR: 0
Reply 20, posted (1 year 3 months 2 weeks 5 days 16 hours ago) and read 9631 times:

Quoting moo (Reply 11):
Why were the engines at idle?

An excellent question for the flight crew of OZ 214. I'm sure the NTSB will have that question on their list.

Quoting moo (Reply 11):
I always thought that you had a decent amount of power selected precisely because it takes the engines so long to spool back up - you controlled the speed using other aerodynamic devices during approach, but kept the power on incase you do infact need it at a moments notice.

You are correct.

A key comment from the NTSB briefing "a few seconds before impact, the throttles were advanced and the engines reacted normally" so the throttles worked, the engines worked, all that remains in question is the human who is responsible for the position of the throttle (either by monitoring automation or manipulating the throttle by hand.)

An Airbus would have reacted exactly the same as a Boeing or a Cessna.

Think about it. How does a plane land? Power back to idle, Flare (below "target speed" or Vref) and wheels make contact with the runway. That's exactly what happened here if you substitute the words "sea wall" for "runway" None of Airbus systems prevent a plane for landing in the wrong spot.

[Edited 2013-07-08 04:04:22]


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User currently offlineoly720man From United Kingdom, joined May 2004, 6817 posts, RR: 11
Reply 21, posted (1 year 3 months 2 weeks 5 days 16 hours ago) and read 9578 times:

Quoting KarelXWB (Reply 16):
Correct me if I'm wrong, but I thought the GPWS does not work with the landing gear down and flaps deployed.

I'd expect it will depend on the system. It may make sense to not have it operational with the gear down, but there may be situations where the aircraft is not landing and the gear is down (hydraulic failure, or failure to retract) and the system is live. It may be a manual intervention to turn it off rather than have it automatically turn off when in a landing configuration, for example.



wheat and dairy can screw up your brain
User currently onlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 22, posted (1 year 3 months 2 weeks 5 days 16 hours ago) and read 9376 times:

Quoting QatarA340 (Reply 13):
I dont get why planes dont have some sort of sensor to know that the plane is actually TOO low and they have to abort landing. Each plane should have the elevation of the runway, and their own elevation and the geographical coordinates of the runway and then they could tell if the airplane is actually too far, too low, too close to the runway threshold.

They sorta do in parts of EGPWS. However this sort of sensing is very very hard to design without getting zillions of spurious results. Enhanced GPS systems that can really give the needed data are pretty bleeding edge AFAIK.

[Edited 2013-07-08 05:08:40]


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently onlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 23, posted (1 year 3 months 2 weeks 5 days 15 hours ago) and read 8519 times:

Quoting eaa3 (Reply 14):

I realize that you can crash an Airbus plane just as any other. The crash in the forest was, if I remember correctly, because the plane entered flare mode.

Flare mode had nothing to do with the crash. It happened because the pilot had let the airspeed and altitude decay while at flight idle at a very low altitude. No way the power available was going to make that plane climb again in the vertical distance available.

The envelope protection system kept the wings nicely level while avoiding the stall, probably saving many lives.

There were many contributing errors, such as a last minute change of runway, demonstration flying below legal altitude, demonstration flying with passengers on board, lack of briefing, "watch this" attitude.

Quoting eaa3 (Reply 14):
However, my question is the following: What would the flight envelope protection system on an Airbus have done if the aircraft slowed down as much as was the case here.

AFAIK it would have kept increasing angle of attack until the wing was just below the critical angle of attack, then increased thrust.

Quoting KarelXWB (Reply 16):
Correct me if I'm wrong, but I thought the GPWS does not work with the landing gear down and flaps deployed.

You'd get a "glideslope" warning but only if you were following an ILS.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineBoeing77w From United Kingdom, joined May 2007, 206 posts, RR: 0
Reply 24, posted (1 year 3 months 2 weeks 5 days 15 hours ago) and read 8500 times:

Quoting QatarA340 (Reply 13):

EGPWS systems use a database of airfields to know when an aircraft is on an approach to a runway. Mode 4 provides warnings of "Too Low Gear" "Too Low Flaps" and "Too Low Terrain". These alerts are triggered by certain conditions which ultimately prevent an aircraft from making an approach incorrectly configured.

There is also a "SINKRATE" warning as a part of EGPWS Mode 1 which alerts crew to excessive rates of descent and is activated prior to a "PULL UP" warning. Below 1000ft any descent rate in excess of approximately 2000ft per minute will activate the warning.

There is also a glide slope call which alerts crew to excessive deviation below the GS on approach. Obviously this is only operational on an ILS approach though.

Quoting oly720man (Reply 15):
but I would expect that wouldn't be turned on for a landing over the sea

The systems are always active in normal operations. If a non-normal situation occurs then procedures can direct crew to disable certain aspects of the system to prevent spurious warnings

The warning systems are there.

Quoting moo (Reply 11):
Why were the engines at idle?

Depending on circumstances it may necessary to significantly reduce thrust, even to idle, however this is usually only really needed in the later stages of the approach. If the airspeed starts increasing significantly when the aircraft is in the landing configuration then the only way to reduce speed is to reduce thrust. Sudden changes in headwinds/tailwinds can dictate this in order to maintain the approach speed. The 5.5 glide slope into London City is obviously fairly 'non standard' but I know of guys who have had to reduce thrust to idle as high as 80-100ft and maintain this until touchdown.

At the appropriate time FADEC will place the engines into Approach Idle. This means a higher N1 and N2 for the same airspeed and altitude compared to Flight Idle (cruise), as a result engine spool up times are reduced and provides quicker acceleration in the event of thrust application/go around.


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 25, posted (1 year 3 months 2 weeks 5 days 14 hours ago) and read 8973 times:

A summary of my response to the OP which was deleted when the thread was moved.

Short answer - the B777 remained largely in one large piece because the video and other information show that the main pressure vessel was not subject to any hard impact forces on just one part of the vessel (other than the empennage shattering and fracturing the rear pressure bulkhead.

It didn't slam down nose first onto the runway. It floated which allowed the spin to occur. There was never any significant forces upon the wings - they did not break off, and did not break the cabin open in doing so.

There is no reason to believe any composite or other metal based passenger transport aircraft would have had significantly more damage to the passenger cabin.

But every crash is different - trying to compare one crash to another is always a leap of logic into the realm of fantasy.


User currently offlineKlaus From Germany, joined Jul 2001, 21488 posts, RR: 53
Reply 26, posted (1 year 3 months 2 weeks 5 days 14 hours ago) and read 8952 times:

Quoting PHX787 (Reply 2):
I don't like the wording of this question at all. I'm not an av expert but I mean, if this was pilot error regarding the air speed, then any plane would have had such an accident.

The question may in fact be somewhat relevant how the Boeing and Airbus autothrottle / autothrust systems work in a manual approach such as this one. Their operation modes do differ.

The whole point of automation well done is to automatically remove as many traps as possible people would fall into normally.

As long as people are in control, you can't eliminate human error, but you can make it less likely to have catastrophic consequences.

That is what safety automation is all about.


User currently offline77West From New Zealand, joined Jun 2009, 136 posts, RR: 0
Reply 27, posted (1 year 3 months 2 weeks 5 days 14 hours ago) and read 9197 times:

I would rather put this here than in the general thread on OZ214, I loaded up this situation in a 737 simulator (biggest I have access too) and let the speed drop off on purpose with a flaps 30 landing onto 28L with a high approach, and surprise, after letting VREF fall 20kt below intended, bang I hit the bay (didnt even make the seawall) So in an Airbus, which I don't have access to, I would assume that if they manually flew it and let the speed bleed away then yes the same thing would happen. Something I was always taught was be ahead of the airplane, especially with bigger aircraft. Low, slow and idle is a recipe for disaster. I now have a horrid aversion to engines at idle below 1000ft. It usual means something is not right. And that's in a much smaller plane. We still need to find out what mode they had the autothrottles in, this will provide a better comparison to an Airbus in this situation.


77West
User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 28, posted (1 year 3 months 2 weeks 5 days 12 hours ago) and read 9129 times:

Quoting C680 (Reply 20):
An Airbus would have reacted exactly the same as a Boeing or a Cessna.

The main difference with the Airbus would have been two fold, GS mini looking at the actual wind where the aircraft is compared to the tower reported wind and adjusting the Vapp for a constant ground speed. So the approach speed can possibly change all during the approach. If the wind changes enough, it could trigger a windshear warning.

They would more than have likely have got a low energy warning, "SPEED SPEED SPEED", and possibly also %u03B1-Floor protection. The low speed protection uses the configuration, airspeed deceleration rate and flight path angle to work out if the aircraft energy has become too low and that thrust needs to be added to recover the flight path. (this does not activate under 100').

The actual reaction will depend on if the autothrust was being used or not.

Airbus are "trajectory/flight path stable", they are good at flying constant tracks and flight path angles (constant ground speed) regardless of what the wind is doing (within reason), for even a simple visual approach, they have a doughnut on the PFD that will give the pilots a pseudo 3 deg slope. The 777 is more "speed stable", it is very good at maintaining an indicated speed, however wind profiles change as aircraft get closer to the runway, so some adjustment is required by the pilot to maintain the correct flight path.

In any case the main cause of all tail strikes and runway overruns are "unstable approaches". Airbus also now has a runway overrun protection system that looks at the runway length and aircraft energy to see if the aircraft will stop in time for the given conditions. They have tried to look at the too little, and too much energy cases.

Each philosophy has positive and negatives, it is difficult in hindsight to say this or that would/could have happened. Obviously lots of 777s have landed on that runway before, so the issue combination of factors, and that is for the NTSB to determine.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinevikkyvik From United States of America, joined Jul 2003, 10109 posts, RR: 26
Reply 29, posted (1 year 3 months 2 weeks 5 days 9 hours ago) and read 8762 times:
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Quoting Starlionblue (Reply 23):
AFAIK it would have kept increasing angle of attack until the wing was just below the critical angle of attack, then increased thrust.

Suppose that depends on the flight mode, no? I'm remembering the Indian Airlines 605 crash in Bangalore, where the aircraft was in Open/Idle Descent mode (for no good reason).

This crash seems a lot like that one in some ways, among them too late of a realization and attempt at recovery, and the roof of the aircraft burning off.



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User currently offlineroseflyer From United States of America, joined Feb 2004, 9666 posts, RR: 52
Reply 30, posted (1 year 3 months 2 weeks 4 days 22 hours ago) and read 8224 times:

Honest question. With the autopilot disconnected, what would the envelope protections have done? Does the A330 automatically kick the auto throttle back on and add thrust when approaching a stall? That sounds like a very scary thing to have happen when in landing configuration and the radio altimeter showing under 100 ft. Zeke, how would the system detect at such a low altitude that there was too little thrust at such a low altitude and if I remember correctly a temporary displaced threshold.

I honestly wonder if any envelope protections can help a pilot on a visual approach that is far too low at the last second. After all it is pretty hard to ignore four red lights of the PAPI even for the reserve crew in the jump seat.



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User currently onlineStarlionblue From Greenland, joined Feb 2004, 17068 posts, RR: 66
Reply 31, posted (1 year 3 months 2 weeks 4 days 22 hours ago) and read 8218 times:

Quoting roseflyer (Reply 30):
With the autopilot disconnected, what would the envelope protections have done?

Prevented a stall. Look at the famous 320 crash at Mulhouse. Rock steady right to the ground.

"SPEED, SPEED, SPEED" warning as mentioned above.

Quoting roseflyer (Reply 30):
I honestly wonder if any envelope protections can help a pilot on a visual approach that is far too low at the last second.

I think history has shown that it only helps in a limited way by preventing a stall. Envelope protection can't break the laws of physics by negating gravity (though I'm sure Airbus is working on it).

The displaced threshold has no impact. The airplane doesn't know where the threshold is unless it is following an ILS/MLS.

As I understand it, the plane doesn't care at what altitude the speed is too low. It just cares that it is too low.

And then there is Flare mode under 50 feet.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinePPVRA From Brazil, joined Nov 2004, 8969 posts, RR: 39
Reply 32, posted (1 year 3 months 2 weeks 4 days 12 hours ago) and read 7845 times:

Quoting moo (Reply 11):
Why were the engines at idle? I always thought that you had a decent amount of power selected precisely because it takes the engines so long to spool back up - you controlled the speed using other aerodynamic devices during approach, but kept the power on incase you do infact need it at a moments notice.

I've seen reports of an unusually steep approach. If you're coming in steep you need to reduce throttle as necessary otherwise you get too fast. This allows you to pitch down to get back down on the glide slope while maintaining a certain speed.

[Edited 2013-07-09 08:53:41]


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User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 33, posted (1 year 3 months 2 weeks 4 days 11 hours ago) and read 7838 times:

Quoting roseflyer (Reply 30):

They would have got the low speed warning "SPEED" a couple hundred feet up, it would have gone off at around Vref-4 kts given the flight path angle that has been computed so far. The other auto thrust mode would have kicked in soon there after.

Some of the information I have seen suggests they were 20-30 kts below Vref, this is yet to be confirmed by the NTSB. If that is correct, they were too slow well before 100'. Reconstruction of the flight path on final suggests the last time they were in the correct energy state for the approach was around 500 ft, around 1.5 nm from the runway.

Under 100 ft nothing would be different.

Still need to see the NTSB data read outs to know for sure.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently onlineeaa3 From United States of America, joined Sep 2007, 1021 posts, RR: 0
Reply 34, posted (1 year 3 months 2 weeks 4 days 10 hours ago) and read 7778 times:

Quoting zeke (Reply 33):
They would have got the low speed warning "SPEED" a couple hundred feet up, it would have gone off at around Vref-4 kts given the flight path angle that has been computed so far. The other auto thrust mode would have kicked in soon there after.

Some of the information I have seen suggests they were 20-30 kts below Vref, this is yet to be confirmed by the NTSB. If that is correct, they were too slow well before 100'. Reconstruction of the flight path on final suggests the last time they were in the correct energy state for the approach was around 500 ft, around 1.5 nm from the runway.

That's very interesting. It suggests that the Airbus flight envelope protection system would not have let them get anywhere close to this slow and it would have reacted much earlier with a warning.


User currently offlineroseflyer From United States of America, joined Feb 2004, 9666 posts, RR: 52
Reply 35, posted (1 year 3 months 2 weeks 4 days 9 hours ago) and read 7757 times:

Quoting eaa3 (Reply 34):

That's very interesting. It suggests that the Airbus flight envelope protection system would not have let them get anywhere close to this slow and it would have reacted much earlier with a warning.

That is not necessarily true. The 777 has the same automatic speed mode protection built into the autothrottles as Airbus does if I understand correctly. If above 100ft, and approaching stall, the 777 will command thrust if the autothrottle is armed. All the logic is inhibited below 100ft, so like Zeke said, the Airbus Envelope protection may not have acted differently. Also, the stick shaker activated only seconds before impact, so we don't know how close they were to Vmin on approach when above 100ft. While they may have had a high sink rate and been close to a stall, it doesn’t necessarily mean that they did stall.



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User currently offlineKlaus From Germany, joined Jul 2001, 21488 posts, RR: 53
Reply 36, posted (1 year 3 months 2 weeks 4 days 6 hours ago) and read 7579 times:

Quoting roseflyer (Reply 35):
All the logic is inhibited below 100ft, so like Zeke said, the Airbus Envelope protection may not have acted differently.

A slow decay of airspeed right down to stall speed without any countermeasures kicking in? I have a hard time believing that normal or flare laws on an Airbus would allow that to happen.


User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 37, posted (1 year 3 months 2 weeks 4 days 5 hours ago) and read 7543 times:

Quoting roseflyer (Reply 35):
The 777 has the same automatic speed mode protection built into the autothrottles as Airbus does if I understand correctly.

Not sure about that, it is 400' for one of them on the 777. The 777 as far as I am aware does not have the trajectory computation to know to call "SPEED SPEED SPEED", that would have been triggered before the autothrust mode (angle of attack). The higher the flight path angle (rate of descent for a given ground speed) the sooner that call gets generated. Also the 777 does not use ground speed computation, the Airbus will change the Vapp based upon the actual wind to maintain a constant ground speed. Thus if part of the reason for the drop of indicated airspeed was a wind shift from headwind to tailwind, the Airbus system would have picked that up also. When the autothrust is in a speed mode, it will not let the aircraft speed decay below what is known as Vls, which is around Vapp-5 normally.

The two low speed protections on the Airbus work off different triggers, one with the computed energy state and the trajectory, the other is based upon angle of attack.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinemandala499 From Indonesia, joined Aug 2001, 6927 posts, RR: 76
Reply 38, posted (1 year 3 months 2 weeks 4 days 5 hours ago) and read 7519 times:

Quoting Klaus (Reply 36):
A slow decay of airspeed right down to stall speed without any countermeasures kicking in? I have a hard time believing that normal or flare laws on an Airbus would allow that to happen.

We do not know if autothrust was on, off but armed, or unarmed.

If it was on, then this shouldn't have happened on an Airbus or a Boeing unless preceded by a very steep descent resulting in idle thrust until too low, with the exception of if the aircraft autothrust had detected an altitude low enough to commence the autothrust to idle (A/T flare mode)... which is there on Boeings (kicks in at 27' RA ?). Then a go-around would need the Go-Around switches to be pressed, simply slapping the thrust levers to foward full stop would just result in lever retardation once you take your hands off (remember the TK crash in Amsterdam?). On a Bus, slap the levers forward and you activate Go-Around mode regardless if A/T was on or off.

If it was off and unarmed, then the same thing would have happened. The alpha floor protection wouldn't kick in, the stall protection would not have the thrust function working, pitch only. Again, go-around would need the throttles moved forward and the go around button pressed otherwise you won't have flight director guidance in go-around mode for the aircraft. On a Bus, slap the throttles forward and you have G/A thrust and flight director in go-around mode. However, whether they had time to escape the wall? No one knows.

If it was off but armed, the likely answer would be, unless flare law has been activated, it shouldn't have happened (can't be bothered to open the protection modes available in flare).... and the rest is the same as the above 2 other alternatives.

For the Bus... unless you're on autoland, the autothrust shouldn't have commanded a retardation of thrust as long as you haven't pulled the thrust levers back to idle (retard), and the autothrust would command thrust according to the selected speed or FMGC selected speed... even down to touchdown.

However, caveat emptor... the above reply was made without looking at the FCOMs so there's bound to be mistakes in there....



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineKlaus From Germany, joined Jul 2001, 21488 posts, RR: 53
Reply 39, posted (1 year 3 months 2 weeks 4 days 3 hours ago) and read 7421 times:

Quoting mandala499 (Reply 38):
We do not know if autothrust was on, off but armed, or unarmed.

Thank you for your input.

According to today's NTSB briefing (as far as I've caught most of the live run – I'm yet to re-watch the recording from the start):
http://www.c-span.org/Events/NTSB-Br...a-Airline-Plane-Crash/10737440372/

• the NTSB investigators found the auto-throttle switches in the "armed" position on their first inspection of the cockpit

• according to the first interviews of the active pilots (PF/FO: trainee; PNF/PIC: trainer), they "relied on the autothrottle" to maintain thrust

Hensman didn't want to speculate whether the "armed" position of the switches was consistent with FDR data and which exact consequences the "armed" position would have, exactly, in the available modes.

I must admit I'm still not quite clear on that after reading your post. Assuming the switch position reflects the actual state during the approach, which possibilities would remain there, as far as you can recollect?

Quoting mandala499 (Reply 38):
with the exception of if the aircraft autothrust had detected an altitude low enough to commence the autothrust to idle (A/T flare mode)... which is there on Boeings (kicks in at 27' RA ?).

Would it actually allow airspeed to decay down to and below stall velocity? Even or especially during flare, this appears hazardous. And would that be allowed to happen on both aircraft series?

Quoting mandala499 (Reply 38):
Then a go-around would need the Go-Around switches to be pressed, simply slapping the thrust levers to foward full stop would just result in lever retardation once you take your hands off (remember the TK crash in Amsterdam?). On a Bus, slap the levers forward and you activate Go-Around mode regardless if A/T was on or off.

If I got that correctly from yesterday's presentation, TOGA was commanded only about 1.5s before impact. Thrust increase was commanded before that around 7s before impact (with about 50% thrust achieved at impact).

Quoting mandala499 (Reply 38):
If it was off and unarmed, then the same thing would have happened. The alpha floor protection wouldn't kick in, the stall protection would not have the thrust function working, pitch only.

Isn't that dangerous? Stalling even right in flare still seems plenty problematic.


User currently offlineKlaus From Germany, joined Jul 2001, 21488 posts, RR: 53
Reply 40, posted (1 year 3 months 2 weeks 4 days 3 hours ago) and read 7384 times:

Further information from the NTSB press briefing:
http://www.c-span.org/Events/NTSB-Br...a-Airline-Plane-Crash/10737440372/


Further post-crash cockpit observations by the NTSB:

• autothrottle switches in the ARMED position

• Flight Director ON for the right seat

• Flight Director OFF for the left seat

• All 3 fire handles were EXTENDED (detached right engine had a fire due to a ruptured oil tank apparently spilling on hot surfaces - no statement yet whether any of the fire bottles were actually discharged; both engines and the APU detached from the fuselage)

• Flaps set to 30

• Speedbrake lever was DOWN


Preliminary information from pilot interviews according to the NTSB:

• PF/FO/trainee: left seat (10 legs on the 777, about 30 hours on type; Rated on: 737, 747, A320 (captain and instructor), 777)

• PNF/PIC/instructor: right seat (3000h 777, 1000h PIC, prior 10y korean air force experience)

• both active pilots flew together for the first time

• Relief FO was in a cockpit jumpseat

• Relief captain was seated in the cabin


PNF recollection of events as reported by the NTSB:

• were somewhat high at 4000'

• set vertical speed mode 1500'/min

• realized at about 500' that they were low

• saw 3 red 1 white PAPI

• told PF to pull back

• had set speed at 137kn

• assumed that autothrottle maintained speed

• between 500' and 200' they had some lateral deviation

• trying to correct

• at 200': 4 red PAPI, airspeed in the hatched area on the speed tape

• recognized the autothrottle was not maintaining speed

• established go-around attitude

• went to push the throttles forward but the PF had already done that at this point

• after impact the aircraft "ballooned" and yawed left

• went into 360° spin

• FO received hospital treatment due to a cracked rib

• other pilots apparently not injured

[Edited 2013-07-09 17:55:12]

User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 41, posted (1 year 3 months 2 weeks 3 days 20 hours ago) and read 7129 times:

Quoting Klaus (Reply 40):
• Flight Director ON for the right seat

• Flight Director OFF for the left seat

I said in the CivAv thread, Airbus recommends either both FD on or off, one on, one off is asking for trouble.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineKlaus From Germany, joined Jul 2001, 21488 posts, RR: 53
Reply 42, posted (1 year 3 months 2 weeks 3 days 20 hours ago) and read 7088 times:

Quoting zeke (Reply 41):
I said in the CivAv thread, Airbus recommends either both FD on or off, one on, one off is asking for trouble.

Yes, thank you.

But why are there even two separate units, then, if it isn't for sheer redundancy?


User currently offlinemandala499 From Indonesia, joined Aug 2001, 6927 posts, RR: 76
Reply 43, posted (1 year 3 months 2 weeks 3 days 18 hours ago) and read 7076 times:

Quoting Klaus (Reply 39):
Would it actually allow airspeed to decay down to and below stall velocity? Even or especially during flare, this appears hazardous. And would that be allowed to happen on both aircraft series?

For the Boeings, A/T in the flare would, retard at 27' RA (at least on 737s).
For the Airbus FBW, A/T would maintain speed (Selected, or Managed), until thrust levers are retarded. This is why we hear the 'retard, retard' call.

Quoting Klaus (Reply 39):
Isn't that dangerous? Stalling even right in flare still seems plenty problematic.

Yes and no. On the Boeings, you have the moving thrust levers under A/T, so if you don't like it retarding, just hold it. On the Bus FBW, you don't have the moving thrust levers under A/T, so it doesn't idle itself on flare, it asks you to idle it by moving the T/L to idle (hence d/c the A/T too), when you want to.

Dangerous? Yes, if you don't know what you're doing AND what it's doing. Otherwise, it's safe enough.  
Quoting Klaus (Reply 42):
But why are there even two separate units, then, if it isn't for sheer redundancy?

Well, U got 2 pilots, and 2 FDs and 2 APs.
Pilot 1 uses FD1 and AP1 if he's PF.
Pilot 2 uses FD2 and AP2 if he's PF.
Yes, it's for redundancy, and also one can select the display source to left or right. If Pilot 1 flies using data sources from the pilot 2 side, you don't want to have AP and FD sourced to the left side.



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 44, posted (1 year 3 months 2 weeks 3 days 18 hours ago) and read 7051 times:

Quoting Klaus (Reply 42):

On the airbus they are driven by the associated fmc/ap. in the case of a fm failure, both fds are driven from the same source. I assume the 777 would be similar.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineMax Q From United States of America, joined May 2001, 4669 posts, RR: 19
Reply 45, posted (1 year 3 months 2 weeks 3 days 17 hours ago) and read 7034 times:

Tragic, tragic, tragic, there is a real cultural issue here.


It's incomprehensible to the Western mind that Professional Pilots of this experience could have completely lost
all situational awareness on a calm, sunny day in one of the best Aircraft ever made and do absolutely nothing until it was far too late.


All you have to do is look back at the accident and incident record of the two major Korean carriers to confirm this.



The best contribution to safety is a competent Pilot.
User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 46, posted (1 year 3 months 2 weeks 3 days 14 hours ago) and read 6884 times:

Quoting Max Q (Reply 45):
It's incomprehensible to the Western mind that Professional Pilots of this experience could have completely lost all situational awareness on a calm, sunny day in one of the best Aircraft ever made and do absolutely nothing until it was far too late.

I would disagree with some of your statement.

I believe the lack of speed issue was a gradually increasing situation. The lower they got the more unlikely it was that the low energy situation could be corrected. It wasn't something that stood out and cried for attention until it was a BIG problem.

Rather than focusing on manually lining up with the runway, the crew would have had to give lining up a lower priority in their minds and focus on speed as a greater priority.

Since they have likely never flown a Cessna or similar small trainer for decades - that type coordination is only a distant memory.

I also do not think this accident could not have happened the same same way in most US or European airlines.

The accountants today force pilots to focus so much on using things like autothrottle to save a couple gallons of fuel. Saving fuel is major requirement for today's pilots.

These guys got into a situation which broke the routine, which the airlines (oriental AND western) discourage, and apparently relied on one part of the system to take care of the speed while they focused on getting lined up with the runway. Likely misunderstanding exactly how the system worked.

As mentioned above - automation can be extremely useful and safe. Misunderstanding automation can be fatal


User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 47, posted (1 year 3 months 2 weeks 3 days 12 hours ago) and read 6847 times:

Quoting Max Q (Reply 45):
All you have to do is look back at the accident and incident record of the two major Korean carriers to confirm this.

The record for KE and OZ is not that bad, especially in the last 20 years. My reading of the OZ 744F crash as a result of a cargo fire two years ago did not indicate any problems with the crews performance that I could recall.

Quoting rfields5421 (Reply 46):
The accountants today force pilots to focus so much on using things like autothrottle to save a couple gallons of fuel. Saving fuel is major requirement for today's pilots.

It is not just the accountants, Boeing recommends on the 777 for the autothrottle to be used even with the autopilot disconnected. The 777 trim is no longer a conventional trim, the aircraft being FBW auto trims as the configuration changes. The auto trim, and auto throttle work hand in hand.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinePPVRA From Brazil, joined Nov 2004, 8969 posts, RR: 39
Reply 48, posted (1 year 3 months 2 weeks 3 days 12 hours ago) and read 6815 times:

Do we know what aircraft the PF was flying just prior to being trained on the 777? If it was the A320, I wonder if he could have mixed up Airbus and Boeing systems.

Quoting rfields5421 (Reply 46):
Rather than focusing on manually lining up with the runway, the crew would have had to give lining up a lower priority in their minds and focus on speed as a greater priority.

Since they have likely never flown a Cessna or similar small trainer for decades - that type coordination is only a distant memory.

That's basic cross-checking of instruments. Shouldn't be a problem for pilots with that many hours.



"If goods do not cross borders, soldiers will" - Frederic Bastiat
User currently offlineKlaus From Germany, joined Jul 2001, 21488 posts, RR: 53
Reply 49, posted (1 year 3 months 2 weeks 3 days 12 hours ago) and read 6813 times:

Quoting PPVRA (Reply 48):
Do we know what aircraft the PF was flying just prior to being trained on the 777? If it was the A320, I wonder if he could have mixed up Airbus and Boeing systems.

Yes, it was the A320 for several years according to the preliminary NTSB information.


User currently offlinezeke From Hong Kong, joined Dec 2006, 9159 posts, RR: 76
Reply 50, posted (1 year 3 months 2 weeks 23 hours ago) and read 6052 times:

Quoting rfields5421 (Reply 46):

I believe the lack of speed issue was a gradually increasing situation. The lower they got the more unlikely it was that the low energy situation could be corrected. It wasn't something that stood out and cried for attention until it was a BIG problem.

I should add while hand flying pilots ignore the flight directors and get low and slow, at around 7 kts below their target speed (130 kts in this case) the flight directors would disengage and the auto thrust mode would change to add thrust to maintain the minimum speed. This is to take into account pilots getting task saturated during a visual or circling approach allowing the speed to wash off.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
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