National Air Cargo 747-400 Crash

[stekeller]

In Bagram, Afghanistan...

http://avherald.com/h?article=46183bb4&opt=0

Unfortunately it sounds as if all souls on board have been lost.

- Stekeller
KORD

[Jeroen Hoppenbrouwers]

I'm nearly certain this was "one of ours". It hurts to see a tiny bit of myself join the unfortunate souls that perished in this awful crash.


Hoppie

[frumpy]

There's a video available.

http://www.youtube.com/watch?v=vo51Be2jL8c

Poor souls aboard, poor families.

[stekeller]

I just saw that frumpy. Pretty horrific.

It seems clear that the aircraft stalled on takeoff - the question will be "why."  

RIP to all those on board and my thoughts go to all affected by this disaster. Sorry for your loss Hoppie. I have a friend who knew many pilots who went to work for National, but none of those on board. Small consolation.

- Stekeller
KORD

[Jeroen Hoppenbrouwers]

Affirmative on the equipment. We had a quick access flight recorder on that one. Not a chance.


Hoppie

[Balt]

That is one of the most gut wrenching videos I've ever seen. Throughout my piloting life, insufficient pitch authority for whatever reason has always been my worst nightmare.

Awful, just plain awful.

- Balt

[delcom]

[Jeroen D]

That is one of the most gut wrenching videos I've ever seen.
Awful, just plain awful.

Could not agree more.

Jeroen

[Balt]

this was "one of ours".

Hoppie, what does "one of ours" mean?

- Balt

[Jeroen Hoppenbrouwers]

The company I work for builds avionics equipment. We had at least a miniQAR and possibly a satLINK on that ship.


Hoppie

[Flying Mick]

Sorry to see the plane tumble!
Gear was still "down" and looked like the pilots
were trying to stablelize the Boeing - to low...

Take care !

Michael
EDDT

[Joe Clark]

This is by NO means official, but here is a"preliminary report" article written by an aviation site I frequent: http://www.nycaviation.com/2013/05/national-air-flight-102-a-preliminary-report/

[Balt]

An interesting piece of deductive logic. The last conclusion about the nose not dropping enough though might simply be due to stall recovery technique used rather than aft CG: fly attitude and firewall throttles, i.e. don't let the nose drop. That's particularly important when close to the ground as you want to minimise altitude loss for obvious reasons. At some point it will recommence to fly. An unsuccessful variant of this technique (with far too much pitch up) resulted in the AF deep stall-ish descent.

Just out of pure technical interest, using a few assumptions, it would be interesting to try and recreate the results in PS 1.3. Is there a way to inject a CG shift?

Cheers

- Balt

[IefCooreman]

The last conclusion about the nose not dropping enough though might simply be due to stall recovery technique used rather than aft CG: fly attitude and firewall throttles, i.e. don't let the nose drop.

"Thanks to" crashes like the AF330, and especially the Turkish 737 crash at Amsterdam Boeing has realised the nose needs to come down before you set power. They had to change recovery procedures.

737's have always had the problem of limited elevator authority, and the engines under the wings basically push the aircraft further in the stall with the nose up momentum they create in and aft trimmed aircraft (low speed). Without simultaneous pitch down, you will never get out of the stall. It was known, but the Turkish pilots didn't remember.

All Boeing fcoms now show very clear: step 1: nose down, since all Boeings are underwing mounted engines. Fly-by-wire or not.

[Eldrarak82]

So sad to see this on the news. The video was shocking to watch. Definitely a stall condition, and I too thought that maybe the CG had shifted too far aft. I just read the preliminary report (unofficial), but it does confirm my initial suspicions. My condolences to the friends and family.

-Eldrarak

[Aidan]

For what it's worth the Airbus stall recovery procedure (at least on the A320) is:



A soon as any stall indication (could be aural warning or buffet) is recognised; apply the immediate actions:

NOSE DOWN PITCH CONTROL APPLY

This will reduce the angle of attack

Note: in case of lack of pitch down authority: reducing thrust may be necessary

BANK:                               WINGS LEVEL

When out of stall (stall indications no longer apply) :

THRUST:          INCREASE SMOOTHLY AS NEEDED

Note: In the case of one engine inoperative, progressively compensate the thrust asymmetry with rudder

SPEEDBRAKES:             CHECK RETRACTED

FLIGHT PATH:               RECOVER SMOOTHLY

If in clean configuration and below 20,000

FLAP 1:                               SELECT

Note: If a risk of ground contact exists, once clearly out of the stall (no longer stall indications), establish smoothly a positive gradient.

In fact, in any jet aircraft with underslung engines 'firewalling' will never be part of the stall recovery procedure, to be clear this is the opposite of light aircraft where 'firewalling' does not cause a dramatic pitch up motion and in fact usually assists in producing airflow over the wings, therefore sending the separation point further back.

The analysis by the guys at NYC aviation is more or less the same as what people around these parts are saying, one of the interesting questions to be asked:

How did these items come loose, particularly if the file photo above is any indication of how well the freight is strapped down?

I move self loading freight so our cyclic matrix does not include weight shift after take off (at least not yet anyway) we used containerised loading though so it is possible we could have the same problem, although on the 'light twin I fly' I would be surprised if the shift could be as dramatic as this was.  

[Hardy Heinlin]

As soon as any stall indication (could be aural warning or buffet) is recognised; apply the immediate actions:
[...]
[...]
BANK:                               WINGS LEVEL

Re wings level: As written in this instruction, I assume the focus lies on "as soon as any stall ...".

I wonder if an Airbus pilot would set wings level in a stall with the ailerons or rather with the rudders.

As we know, the stall process never affects the entire wing all of a sudden. The laminar profile is twisted along the wing. The inboard part has a high angle of incident, the outboard part has a low one. Normally, the inboard section stalls first, so that the outboard aileron remains effective.

Also, with the outboard section stalling later, on a swept wing aircraft where the outboard section is behind the CG, the nose will automatically drop when the stall is just beginning in the inboard section (brilliant design, isn't it?).

In this critical partial stall phase, one could say the outboard aileron is still effective, but one could also say, any aileron deflection could worsen the situation: The aileron-down side would increase the angle of incident causing a stall in an outer wing section where there was no stall before; and the aileron-up side might extend some spoilers on the good wing.

I think, only when the stall progresses further and the entire wings are in stall, with nose down in the brown, all ailerons are of use again as they now steer a falling brick in the wind. However, if the ailerons are applied in the flight phase before, shortly before the full stall, how would you set your wings level on an Airbus? With the ailerons or with the rudders? I would use the rudders. In single-prop Cessnas I always used rudders anyway :-)

On the other hand, with swept wings, the asymmetric lift could be worsen with the rudders as well.

My temporary conclusion: Set wings level only at the very first moment of the stall warning and if the speed is not decreasing; if the aircraft is already vibrating, don't try to set wings level, increase the speed first.


Cheers,

|-|ardy

[IefCooreman]

We had this discussion during training as well. The thing to remember is that stall recovery needs to be initiated at the very first sign of it. Airbus seems to use almost the exact same wording. This implies the aircraft is actually NOT stalled at that moment of first indications, and the recovery is actually a "stall prevention" maneuver, not a full stall recovery. The philosophy behind it is that due to the design characteristics, they claim their jets to have enough "room" between first indication of stall, and the actual occurance. This is also what nobody understands about the AF 330 crash. The pilots had plenty of room for recovery, but where so mislead they went a long way to create the actual stall, and keep it going on.

[Aidan]

Hardy,

I hear what you are saying, however the 320, at least while in the normal weight range and at low altitude (where we practice it in the sim) is very forgiving and manoeuvrable. While the ailerons (and spoilers, as you say) may well exacerbate the stall were the aircraft to be right at the critical angle, or worse still, on the wrong side of the curve, the following should be remembered:

In an Airbus we have indications on the low end speed tape to indicate the lowest selectable speed, VLS; alpha prot. : indicated where the amber line becomes a dashed amber line and the solid red line (stall speed or VSW) keeping in mind that, at least in theory the aircraft cannot be stalled unless it is in alternate or direct law. Alpha prot is where TOGA thrust automatically kicks in during normal law, well before the stall.

If the aircraft is in alternate or direct law then alpa prot. is of little relevance as the aircraft cannot go in to alpha floor so this amber dashed line will not be indicated.

All of the above indications are dynamically indicated, that is to say, their position on the speed tape accounts for flap setting, speedbrake and flight control position and load factor.

I say all this because if the crew are watching the PFD, the far greater likelihood in the event of low energy is that the crew will first hear "SPEED, SPEED" then see the amber rolling upward, both of these things occur well before the stall  and the crew can act accordingly.

Taking in to account the above, in terms of threat and error management, Airbus I believe has decided to play the numbers and assume that even if the aircraft is fully stalled it will most likely be in the early stages, at which point the aircraft is still docile enough to recover with ailerons rather than rudder (at least in the sim anyway) this is therefore the way they teach it.

Should the aircraft be stalled like the guys were at Bagram, then all bets are off and usual airmanship must kick in and rudder at this stage would potentially be a great option.

Remember in a light aircraft (even a twin) increasing power, as you would in a light aircraft will assist in increasing rudder effectiveness.

[Hardy Heinlin]

Interesting.

Aidan, thanks!


Cheers,

|-|ardy