maynardGkeynes

Definitely not intended to bait anyone, and I appreciate the reply!

misd-agin

suninmye - you stated - "If available thrust reduces, the 777 autopilot will fly the ILS glideslope until the speed reduces to just above the stall. It will then ignore the glideslope, lower the nose and descend just above stall speed. If the 038 had hit the ground in this configuration everyone would not have walked away. That statement is based on having seen it a few times in the simulator. Full up elevator, (unheard of in a 777 landing) had been applied at the appropriate time just before impact to cushion it so that many of the occupants thought on touchdown that it was just a hard landing."
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Do you have an official statement that supports your position? The FDR data released by the AAIB doens't show enough data to support your statements, which is why I ask.

There is evidence of an increase in pitch attitude, and a slight decrease in speed, just prior to impact but slight changes in pitch and speed were present just prior to the last FDR data.

Also, if the a/c is being governed by low speed protection, what effect would moving the yoke, to increase AOA, have?

S.F.L.Y

@ WojtekSz
The ILS does not lead the aircraft to the begining of the runway but to the touchdown zone abeam which the glide path antennas are located. On the ILS you usually cross the threshold at 50 ft AGL and touch down some 300 m further.

Keeping the AP on probably means that the crew was expecting thrust to be recovered without deviating from the ILS. Disconnecting the AP and flying below GP to maintain some energy to reach the threshold at a decent Vz is most probably feasible (as in the sim) but would require immediate identification of the loss of thrust.

The OCH on an ILS is decreasing with the distance from the threshold, but gives some room to follow a "flatter" path. I was basically saying that since the acft had enough total energy to reach its actual touchdown point (in the grass) it could probably have reduced its impact Vz by saving energy in not following the GP, which seems to have been demonstrated in the simulator.

Mmmayday38

Hindsight is great isn't it!

I have been told by a couple of sim instructors ‘in the sandpit’ that with a few months of 'hindsight' and accumulated knowledge about this accident, a fair number of crews were 'surprised' with this scenario in the sim; and some of those that claimed to know the method to achieve the actual outcome or 'better', suddenly 'froze' in the sim. Others followed the method I had used on the day, but with hindsight were able to change the flaps earlier, and they still only achieved the same distance or worse! The majority of crews faced with this problem, crashed well short of the perimeter fence; so the people who claim to have done any better; have more forethought than me or less headwind!

It would be interesting to know if those that have “made the r/w” in the sim have used timings based from when we officially had rollback at 720ft or when we, on the day, actually realised we had a problem at 480ft. At 480ft in the sim, are pilots actually then taking the time to decide if this is a ‘fuel’ problem, an EEC problem, a windshear scenario, a double engine failure with EICAS failure…. the list is endless… or..jumping straight to the conclusion that it must be ‘rollback’, which of course was an unknown event on Jan 17th 2008!

Unfortunately for any crew, if this ever happens again (for whatever reason, but it shouldn't now anyway) will be that it is now an emergency procedure with a memory C/L, so would have to be carried out to adhere to SOPs. Will they… close the thrust levers for 10 secs to warm the FOHE or will they change the flaps or both. Two of those will be wrong according to any new SOPs…a big grey area. Pilots will naturally take some seconds to correctly identify the failure as ‘rollback’ and even then might not believe it; so to carry out this drill at low altitude will be scary. Not many pilots I know would like to close thrust levers for at least 10 secs below 400ft on an approach. The spool-up time would be too late. Please also bear in mind another real life rollback event where the crew knew of the event on the BA38; but in a relaxed state of mind in the cruise, they still took some time (in minutes) to realise this was a rollback before they reacted.

I accept that the r/w has been achieved in some sim sessions, but I am not in possession of the sim inputs for my scenario. I appreciate that some posts that make reference to making the r/w are backed up with “with the benefit of hindsight”, however, I don’t know what the settings were set to, or if the drill was only ever practiced with a “complete knowledge that there is a rollback at 480ft and what can you do to get the aircraft down” – as opposed to treating it like an unknown emergency situation ... but would you actually have wanted to take the risk of landing on the tarmac, with massive potential for a fire?

If it was always treated as an emergency situation, then, for those of you who made the r/w, I am sorry for my explanation above, but I am sure you can understand why I felt the need to explain to those non flyers the information needed when coming to a conclusion that the engines are suffering ‘rollback’ as opposed to any other emergency.

Boeing have tested this to the limits in their sim; as you might expect, so you will be able to read their results in due course when the AAIB final report is issued this year.

I, and my family, await its’ release eagerly.

bearfoil

Had the a/c made it to the concrete, 10,000 pounds of fuel was waiting to ignite in the ensuing spark fest. I don't see how the a/c could have made the strip had one practiced the profile for weeks. Given they made it over the fence, missed the hard stuff and no one croaked, what's to complain? Good grief. The Fuel, the fuel, boss.

bear

Green-dot

Question remains, would it be recorded the moment the spars moved from their open position or would a record be made only if the spars reached their closed position? In other words, if an uncommanded partial closing of the spars had occurred which rectified itself before they reached the fully closed position, would that have been recorded? If only recorded when reaching closed position: spars take up to 15 seconds to fully close so if an anomaly lasted anything less than 15 seconds and the spars moved back to their open position, they could have restricted fuel flow considerably without having a record of it and, as reported, the spars would be found in the open postion.

S.F.L.Y

The question isn't to know if it was or not technically possible to make the runway. Before being limited by any technical factor the aircraft was limited by its crew's situation awareness. Appropriate actions cannot be taken before the crew realize and identify the problem The pilots were obviously very confused as they let the AP flying the aircraft at a dangerously low airspeed without taking manual control, most probably because they didn't have time to realize they should give-up on the ILS trajectory.

As a pure coincidence, the flap retraction probably caused the AP to disconnect seconds earlier than with full flaps, which gave the crew enough height to recover from the subsequent 8 degrees pitch reduction and high Vz (100 ft lost in 2.5 sec --> 2.400 fpm).

WojtekSz

@Mmmayday38
whatever you did at the time has worked out fine. With the hindsight i cannot find better way of doing this. I believe many should be grateful for your instinct reaction to the problem. Because i think that it was instinct flying more than anything else - even reading through the desription takes longer time than you had to make decisions.
The sim test as described by M.Mouse show clearly that to reach positive results they had to start corrective immediately at 700ft. It is nice to know what would happen
Would the new breed of low hours pilots know how to react in such demanding situation? Would they have enough flying instincts developed?

@suitcaseman + S.F.L.Y
thanks for correcting on the ILS

WojtekSz

@ S.F.L.Y
i believe you are right that appropriate situation awareness has significant influence on security of the flying. I do not know if the pilots may/should have turned the AP earlier but i assume the rules were not broken as this would be clearly stated in the post accident report.

do you really believe that retraction of flaps was a coincidence? Commended 17 sec before impact while the AP disconnected some 7 sec before impact?

Are you trying to prove it was human error?

S.F.L.Y

@ WojtekSz

I don't know what is so unclear in my statement but I never said the flap retraction was a coincidence (how could it be?!). What I meant is that by coincidence (as it wasn't the crew's intention) this flap retraction accelerated the occurrence of the pitch down movement at AP disconnect. Should the aircraft had few more knots to loose before reaching its lowest speed this AP disconnect and pitch down movement would have happened later, closer to the ground, with no more room to reduce the high Vz. Few seconds before the impact the Vz was way too high as the aircraft initiated a lazy stall.

You are talking about the low hour pilots and flying instinct. Where is the flying instinct when you are VMC, approaching stall speed with no available thrust and that nobody stops the AP to increase the attitude? The most basic flying instinct would command to take over manually just like in a trim overrun. Luckily the aircraft did it by itself and disconnected the AP as it reached unsafe limits. Is it really the aircraft's job to disconnect the AP when speed gets so low?

M.Mouse

The autopilot disconnect was caused by a control input. From the report found here:

S.F.L.Y

M.Mouse, you're right about this control input which is hardly reflected in the data report (no pitch decrease before AP disconnect). Anyway this happened 6.5 sec after speed dropped below 110 kts. At that point there was nothing else to do than lowering the nose to save speed (by increasing Vz). It's not only a matter of trading Vz to save speed to fly above Vs, extra speed is subsequently required to absorb some of the Vz prior to impact. Maintaining a speed just over 100 Kts couldn't reduce the Vz below 1400 fpm.

WojtekSz

@S.F.L.Y
what i read from your comments is the overall idea that if the PF would have done something (lowering the nose) earlier the plane could have landed as usual. Is
that right?
What i do see from the accident report is that PF has reacted (increased thrust) about 5 sec after the speed got below 135kt, and this would be about anyone would take to wait for the AT to correct the speed. At that time i would not expect ANY pilot to start lowering the nose - would you believe otherwise?

S.F.L.Y

We shouldn't have the same report since in mine the X axis is graduated in 2 sec increments. My reading shows that after the speed got below 130 kts you have 13 units before AP disconnect, meaning 26 seconds... How many Kts of deviation are tolerated on approach during a JAA IR test flight? The same graph shows 7 seconds below 110 Kts before AP disconnection. With no offense to the crew this seems to be a lot of time, especially when Vref was lost for over 20 secs.

maynardGkeynes

The report uses the term "movement," which would seem to cover that:

WojtekSz

we have the same report
the difference is that you seem to believe that the first crew action was commanding nose down while i seem to follow the report thinking that 'the autothrottle and the flight crew commanded full thrust' and this has happened much earlier - just after the speed got below 135kt or latest
And to me it is fully understandable as adding more thrust is what most pilots do to add speed while landing . And since B777 is a jet hence it took a while to acknowledge no speed increase. And all this is the time AP was constantly increasing pitch.
I would not consider take this time as no action.

WojtekSz

suitcaseman: i am fully with you on this

S.F.L.Y

At least two guys are having fun. I don't care about criticizing the crew, I'm just interested in understanding how they reacted or not and why. I just observe a certain lack of action while speed decayed and I want to learn from it. If it happened to them it might well happen to me as it would probably happen to most of us. We very often act far from the most logical strategy and analyzing this is certainly a good step in improving flight safety, at least better than randomly distributing safety medals. Now if this also amuse people then it's even better.

Thanks god my personal experience of emergencies is limited to a single good ending event. Not because I'm a sky god but because I had good support from the ground.

WojtekSz

@S.F.L.Y
could you pls elaborate on what would be the most most logical strategy in this case? This might help the me (possibly also others) to understand your point.

S.F.L.Y

Again, this is not the point. Some found out that different tests in the sims could lead to different results. Fact is that in real life crew's reactions are what they are, and not always appropriate since the human brain needs to update its situational awareness and subsequently its strategy. This is why we are trained to perform some reflex actions to some alarms. A normal reaction to speed deviation from Vref is thrust correction, which was attempted by the crew in this particular case. Of course it takes some time for the crew to realize the action is ineffective. At this point the speed keeps going down and the crew naturally focus on sorting out the thrust issue as its difficult to admit you are now flying a glider. This particular point is the most critical as this is when the have to accept the problem and look for a different strategy. It is very interesting to me to see that actions were taken on the flaps (drag reduction strategy) prior to taking manual pitch control. It's probably a much easier mental process to give up on the initial flap setting than on the AP ILS approach. Taking over manual control of a critically low speed and powerless aircraft is a natural decision for any pilot. Why did it happen so late? My point is not to criticize the pilots, but to understand why they didn't take the actions we could expect in such situations.

In other words I don't want to know if I would do better than them, I want to understand why I might be doing the same thing. Hope this time my point is clear.