Ask The Pilot

[jb747]

Report: Air France A320 at Tel Aviv on Apr 3rd 2012, approach to stall on turning final results in Alpha Floor and flaps overspeed

Does the Airbus design contribute to this particular incident or is it a training problem ?

It's an interesting incident, but it caused me to look at another 320 accident from a few years ago, Gulf Air at Bahrain, which is even more eye watering.

Anyway ...this is the AVHerald report:

An Air France Airbus A320-200, registration F-HEPE performing flight AF-1620 from Paris Charles de Gaulle (France) to Tel Aviv (Israel) with 149 passengers and 6 crew, was on a RNAV Visual approach to Tel Aviv Ben Gurion Airport's runway 26. According to the standard instrument arrival procedure via waypoints DOVER and KEREN the crew had been instructed about 10nm prior to DOVER to reduce to minimum clean speed, shortly before overflying DOVER the crew was cleared to descend to 3000 feet and reduce to 180 knots, which the crew complied with utilizing automation in LNAV and open descent. The aircraft overflew KEREN at 3280 feet and 180 KIAS, the pilot flying however felt they were high on the approach but did not share his concern with the pilot monitoring.​

How about actually doing something about it! According to the approach chart (available on the avherald site), he should have been AT 3000' overhead KEREN. Certainly fixable, but already not in accordance with the procedure. From that point he has 10.5 miles to run, so energy-wise there is no particular issue.
​

While on downwind the crew changed to managed speed, selected 1000 feet into the altitude window and activated open descent, the engines reduced to idle thrust. Full configuration is being selected, the Vapp of 138 KIAS is selected into the speed window.

The downwind leg has a descent profile of 2.7º, which is less than the normal 3º of a glideslope. Starting slightly high, if he'd selected 'flight path angle' and about -3.3º he would have arrived at the next way point pretty well exactly on profile (and as its actually a visual approach at this point, there is a lot of flexibility here). Doing it that way, the autothrust would have controlled the speed (and managed means it will go to the 'green dot' speed for each selected flap stage), so as flap is selected the aircraft pitch would be looking after the profile, and the autothrust would have handled the speed. What he has actually done has forced the aircraft to idle, and pitch control is handling speed. Selecting anything into the window means that it isn't managed speed, as that 'closes' if managed (i.e. FMC controlled) (at least in the AB that I know).
​

Still in the decent through about 1540 feet the autopilot gets disconnected, flight director and autothrust remain engaged. The aircraft turned final and was about to align with the extended runway centerline, still at 20 degrees of bank, the pilot flying applies nose up inputs for about 10 seconds while the flight director commands nose down inputs to maintain the target speed, the airspeed reduces from 135 KIAS to 122 KIAS with the pitch increasing from 0.7 to 10 degrees nose up, the pilot monitoring later provided testimony that he was monitoring the alignment with the runway.

The system expects you to obey the flight director. In this case, it's giving commands to handle the speed, and the autothrust is still at idle because of the 'open descent' selection. If he had turned off the flight director (which he obviously isn't following anyway) the autothrust would have reverted to 'speed'.
​

An automatic "Speed, Speed, Speed" call activated at Vapp-16 knots. The pilot flying decided to go around but did not call out the go-around.

As it is designed to do...There is a standard call for this...'Go around, flaps'. Obviously you need the other guy to understand what is happening, but you also need him to do a bunch of things...this call starts that procedure.
​

The pilot flying moved the throttle levers into the TOGA detent and applied nose up inputs, the pilot monitoring applied nose down inputs for about 2 seconds (dual input).

Pilot flying is now well out of his depth, isn't he. The pilot monitoring (who is the captain) probably should have taken over. His input looks to me to be in response to the speed...the dual input would have the effect of reducing or even cancelling the other's nose up input, as the system averages dual inputs. Of course, if the levers where physically interconnected, opposite inputs couldn't happen.
​

At that point Alpha Floor protection activated applying TOGA thrust and TOGA Lock, 3000 feet is being selected into the altitude window, open climb mode is being engaged, the speed returns into normal range, the pilots do not detect the "TOGA LOCK" status however.

The response to the speed call should have been the go around, but what he seems to have done is robotically selected the normal steep go around attitude. Given that he's almost at the stall, a much lower attitude would be appropriate until the aircraft gets back to the normal speed. So, TOGA...hold the attitude (with the FBW will do anyway unless you interfere), and then pitch up once the speed is back around 138 knots. ALPHA FLOOR activation is the stall protection in normal law. It is alway accompanied by the aircraft selecting TOGA (irrespective of the thrust lever position). As he's already selected TOGA there is no noticeable change to the power. I'd expect that they never noticed the FLOOR activation.
​

The aircraft climbs through 2000 feet, the crew recognizes difficulties in reducing the thrust.

Presumably at about 1,500 feet they've pulled the levers to CLB, and nothing has happened. So the auto throttle isn't being allowed to engage again. But, guess what, if you press the A/T disconnect, and simply pull the levers back a bit more, you have manual thrust control. To get rid of TOGA LOCK, you must disconnect the auto throttle, but even if you haven't recognised why the A/T hasn't got control, taking the system back manually fixes the issue. So, why does it behave like this? In the ALPHA FLOOR case, TOGA will be automatically selected even though the thrust levers are totally closed. As part of this, moving the levers has no effect and you MUST disconnect the A/T to regain thrust control. You can put them where you want, press the A/T engage, and then push to the CLB gate, and it goes back to normal. Of course, if the levers were actually servo driven, then this behaviour wouldn't be necessary.

The flaps are selected to 1, the speed increases to 208 KIAS and still continues to increase, the gear is being extended in order to counter the speed increase, 2000 feet and 188 KIAS are being selected into the MCP, the aircraft climbs to 2500 feet before starting to descend again, the speed increased to 223 KIAS (flaps limit 215 KIAS), an overspeed alarm activated. In response to the overspeed alarm the pilot flying reduced the thrust levers to idle, which removed the "TOGA LOCK" mode and disengaged autothrottle, the engines spooled down. The pilot flying stabilized the aircraft, positioned for a second approach and landed safely.

Overall, it is a combination of training and design. Sadly, AB keep inventing more and more complex procedures which are in many cases necessary to overcome the poor man/machine interface. Their response to incidents is generally to invent a new procedure, or to try to make the aircraft even more automatic. And, it's interesting that whilst I'm being critical of Airbus here, it's actually two Boeings that have recently had autothrust related accidents (777 SFO and 737 AMS).​

 

[Chief Wiggum]

A rather bland question in relation to many of the uber technical postings here...

Was just reading this article in todays The Age about "passengers-gone-bad" that cause Capt to turn back or divert.
In regards to the example they used where a LHR - SYD flight turned back last week after just 1 hour...

What would be the estimated cost to the airline to do something like this ?
Must cost them a MASSIVE amount of money ?

I presume to land safely they will need to dump large part of the fuel load after only one hour ?
And then land, park plane, kick off passenger (and their luggage), file report and then refuel and resume (after likely waiting around for gates/slots to open up).
Problems/costs associated with connections & forward equipment schedule at the other end.
Dumped fuel.
New fuel.
Second set of service costs at the departing airport.
Possibility of the FC then going over their hours.

And typically who pays for all this ?

 

[jb747]

And typically who pays for all this ?

Sadly...the airline.

The cost is, as you suggest, huge. Probably 100 tonnes of fuel...even if it was fuel for your car that would still be in the order of $200,000. Running costs for a 380 for about 3 hours...$30k or so. The entire delay would have taken 4-5 hours, so the aircraft is late in Australia, and that could then impact on its next flight, which would be to the USA. It can take a couple of days for the ongoing effects to settle down.

I would love it if these costs were placed upon the person causing the issue in the first place. Failing that....pillories and stocks at the airports would probably work as a reasonable deterrent.

 

[anat0l]

I would love it if these costs were placed upon the person causing the issue in the first place. Failing that....pillories and stocks at the airports would probably work as a reasonable deterrent.

I'd like this too, except of course most people probably couldn't afford those costs, even if you were to harshly garnish their earnings until they die and possibly over to their next of kin. They'd likely declare bankruptcy if that happens.

Mandatory imprisonment in lieu of payment may work, but except for terrorism I have not heard too many - if any at all - passengers who have caused diversions, hurt anyone or anything etc. etc. who has ever, ever been imprisoned. Most get away with court costs and not even a conviction.

The last one I knew of was that woman who forced a QF Trans-Tasman flight back to MEL - I think the charge was assault. She was forced to pay for the costs for diversion. Of course, like all the rest of them, she plead out of character in court.

The attached article is interesting. I don't think increasing the powers of the Captain or crew are of any use if there is no jurisdiction who will allow the effective prosecution of those who behave errantly or violently on an aircraft.

I think some of the comments on the article are fascinating: airlines, through their continual cost cutting and attitude towards not serving passengers well, have brought all these problems unto themselves and they deserve the inappropriate behaviour they have cultivated.

It's unfortunate that airlines have to front the full cost of passengers behaving like oafs or breaking the law in the air in a similar way they would if they were on the ground, of which the airline is really afforded no opportunity of redress. Airlines also foot the full bill if a passenger which they have carried to another country is deported for whatever reason.

Hmmmmm... probably a thread split in there or soon....

 

[mannej]

Talking about costs, what are the typical costs behind a positioning flight? There have been some lengthy position flights lately such as OEH doing DFW-BNE for example. Would the cost of fuel be lower compared to normal making it worthwhile to ferry the aircraft back?

 

[jb747]

Talking about costs, what are the typical costs behind a positioning flight? There have been some lengthy position flights lately such as OEH doing DFW-BNE for example. Would the cost of fuel be lower compared to normal making it worthwhile to ferry the aircraft back?

I don't know the exact costs. But they are certainly considerable. Basically the people who decide these things will balance the various alternatives on a costing basis. Sometimes the obvious solution is actually more costly than another answer.

In that instance though, if you use OEH for the next planned DFW-BNE, what happens to the aircraft that comes from Oz?

 

[Melburnian1]

Sadly...the airline.

The cost is, as you suggest, huge. Probably 100 tonnes of fuel...even if it was fuel for your car that would still be in the order of $200,000. Running costs for a 380 for about 3 hours...$30k or so. The entire delay would have taken 4-5 hours, so the aircraft is late in Australia, and that could then impact on its next flight, which would be to the USA. It can take a couple of days for the ongoing effects to settle down.

I would love it if these costs were placed upon the person causing the issue in the first place. Failing that....pillories and stocks at the airports would probably work as a reasonable deterrent.

There was this recent case in Oz:

Drunk Qantas Passenger Jailed, Must Pay Costs — Civil Aviation Forum | Airliners.net

One difficulty may be that if it is a (to coin a term) 'bogan' who misbehaves, he or she may have few if any material assets and hence any costs ordered payable may never be received by the airline.

 

[Flyboy78]

Hi JB. Long time lurker, first time poster. Sincere thanks for your time and effort in answering these questions, and giving me hours of interesting reading. Hands down the best read on the net

My question comes from a recent flight, departing Perth, as we were turning onto the rwy I looked out the window and the sky was as black and ominous as I've seen. I thought "surely we're not going yet", but we did, and after some dodging and weaving (very roughly) we were soon above the weather.

I'm curious at what point you get a picture of the sky with your radar, I'm guessing this doesn't happen until on the rwy? How then do you decide a path through any nearby storms? Or is this something you sort out once airborne in coordination with ATC? Do you also ever rely on what you can visually see out the window to avoid bad weather?

 

[mjt57]

When the time comes to disconnect, the Boeings' controls will always be in the right place, so just disconnect and hold them wherever they happen to be, and the transition will be smooth.

Autothrust is different, and it is a gotcha.

[chomp...]

First, you must always pull the levers out of the gate, to match the power with what you're actually using...and then you press the buttons.

How do you match thrust lever position to current thrust before disengaging? ie. what indication/instrumentation do you have to ensure that it's a bumpless transfer?

 

[NM]

[Modhat]
Please note the rules for this thread. It is for questions being asked of pilots and answers to those questions by pilots and aviation professionals. Please keep other comments and banter for other threads.
[/Modhat]

 

[jb747]

How do you match thrust lever position to current thrust before disengaging? ie. what indication/instrumentation do you have to ensure that it's a bumpless transfer?

On each engines' thrust display, there is a small donut on the outside. That shows commanded power, and on the inside of the 'dial' it shows actual power. So, just before disconnecting, pull the levers back until the donuts and the actual power are roughly equal.

 

[jb747]

My question comes from a recent flight, departing Perth, as we were turning onto the rwy I looked out the window and the sky was as black and ominous as I've seen. I thought "surely we're not going yet", but we did, and after some dodging and weaving (very roughly) we were soon above the weather.

I'm curious at what point you get a picture of the sky with your radar, I'm guessing this doesn't happen until on the rwy? How then do you decide a path through any nearby storms? Or is this something you sort out once airborne in coordination with ATC? Do you also ever rely on what you can visually see out the window to avoid bad weather?

You start your assessment when doing the preflight. A good look around, even though there's still a bit of time to go, gives you an idea of what to expect.

We turn the radar on as soon as we start to taxi. Sometimes a taxiway leg will be in the approximate direction that we'll be departing, otherwise we'll just have to wait until we line up to get a good look with the radar. It gives us a very good idea of what to expect. Just looking outside is often very deceptive. Something that looks a bit nasty might have very little return on the radar, and conversely something that the eyeball says you could fly into might show some nasty motion.

Because our departure tracks are shown on the ND (nav display) and the radar is also overlaid onto that, we know exactly where the weather is relative to the track. If more than a few miles from the airport, we'll most likely wait until airborne and sort out any tracking requirements with departures. If we'll need a turn in close, we get the tower to coordinate it before take off.

Occasionally, I've entered the runway, had a good look at the radar, and decided that discretion is the better part of valour, and elected to wait until the weather passes (or at least moderates). Each time I've done that, I've watched the 'usual suspects' just blast off into it....

 

[mjt57]

On each engines' thrust display, there is a small donut on the outside. That shows commanded power, and on the inside of the 'dial' it shows actual power. So, just before disconnecting, pull the levers back until the donuts and the actual power are roughly equal.

OK, sounds similar to the 737's display (when I did that Flight Experience thing I got for Father's Day).

Speaking of thrust and indications, what information is shown for engine performance? ie. N1, N2 etc. speed or thrust, etc.?

And overall, what information is shown to you how the engines are running? Do you see stuff like bearing temps and vibes, that sort of thing?

 

[jb747]

OK, sounds similar to the 737's display (when I did that Flight Experience thing I got for Father's Day).

Speaking of thrust and indications, what information is shown for engine performance? ie. N1, N2 etc. speed or thrust, etc.?

% thrust. Though that disappears in degraded mode and you use N1 instead.

And overall, what information is shown to you how the engines are running? Do you see stuff like bearing temps and vibes, that sort of thing?

% thrust, N1, N2, N3, fuel flow, temperature, oil pressure/temperature/quantity, vibration.

 

[Flying Fox]

Occasionally, I've entered the runway, had a good look at the radar, and decided that discretion is the better part of valour, and elected to wait until the weather passes (or at least moderates). Each time I've done that, I've watched the 'usual suspects' just blast off into it....

Does this imply that you simply sit at the end of the runway and wait (blocking it - no offence meant) or do you exit the runway and let the 'usual suspects' overtake you and then you go when you are happy with the weather?

 

[michaelidau]

Sorry, I've been reading this thread for a while but what is N1, N2 and N3?

 

[docjames]

.

. . Each time I've done that, I've watched the 'usual suspects' just blast off into it....

Is there any way to work out the "usual suspects" list (so I know whom to avoid)?

 

[mjt57]

Sorry, I've been reading this thread for a while but what is N1, N2 and N3?

I can answer this, having driven them in the past.

N1 is what is refered to as the low pressure turbine (compressor and driving turbine in the combustion chamber) in a jet engine. N2 is the high pressure turbine/compressor. N3 is usually a third turbine in the exhaust which drives the big fan at the front. In my involvement with this gear it drove an electrical generator.

Some jet engines use N1 or N2 to drive the fan (I forget exactly which one).

 

[Skyhigh777]

Jb, how much technical knowledge does an airline pilot have to have? Are you expected to understand inside and out how every system on the plane works? Do you learn engineering in flight school?

Thanks

 

[Tortuga]

Morning JB, my question also relates to pilot training. I am reading a book by a famous investor who talks about the lack of multidisciplinary models being used by professionals to solve problems (eg. A man with a hammer only sees nails). He goes on to say that colleges should take a leaf out of the way pilots are trained to look at problems by using a variety of mental models (eg. engineering (backup systems), psychology (cognitive biases), mathematics (eg calculating fuel loads, fuel burned in x time in an emergency), biology (reward systems)) as well as using a thing like a check-list that can help remove bias. Can you please give a run-down on how these models were taught to yourself and how someone who is not training to be a pilot but would love to learn about the approach to training and problem solving can go about it? Thanks