Machinbird

Let me agree with this particularly with regard to the aircraft pitch trim system.
An aircraft that keeps trimming the force off the stick/wheel as you slow might be convenient, but it loses natural speed stability and requires increased attentiveness/awareness in manual flight-or an automatic speed control system.

Any aircraft that keeps automatically trimming nose up after the stall AOA is reached has a fouled up design.

HazelNuts39

Maybe so, BUT ... would the sidestick input alone not have kept the airplane in the stall?

Machinbird

Another weakness of the design. A large transport aircraft should need two hands to hold it in a stall, not a crooked pinky finger.

Granted, there are other transports that do not meet this force criteria as well.

VGCM66

Not so fast.

The Automation was built to ASSIST mankind not to second guess him. The Automation was in Alternate Law (NOT in Normal Law) but still allowing it to ASSIST the pilots as in "YOU WANT TO GO UP?. My God you shall go up with all the might of this airplane (THS full up)". But the instruction from the pilot was and still is WRONG cause a High Altitude STALL will be imminent and guarantied, as it did. Machines in full automation do one (and that one might be composed of many, mind you) thing only. And if that one thing can't be performed at its fullest, it must relinquish control back to humans immediately. And in the AF447, that is exactly what the Automation DID as per DESIGN.


But the way, speaking of Automation in those less than 4 minutes of the tragedy, none of the three guys had the smart idea of trying to bring the Auto Pilot back on line and then if successful the Auto-throttle later. Someone should set an A330 simulator and emulate conditions as in the AF447 at level flight100 and throw the AP back on and if successful throw the Auto-Throttle just as well. See what happens. You know what would be funny but not really that so, don't you? Just in case, I am presuming that deploying the spoilers was a great idea of course.






Cheers,

MurphyWasRight

Uhmm I hope a bit better than that.

I allways cringe when I hear something discounted as "that's a 1 in a million scenario". If you do the math on departures per year one in a million is a bit on the low side...

glad rag

Folks, was there a diagram posted on here of the sidestick mechanical layout/operation?

I remember seeing it but what with all the moding/editing have lost track of it...

Machinbird

Let us not confuse automation, basic irreversible hydraulic controls, and the benefits of good aerodynamic design.
What told the THS to go up was not the high level of automation that the 'Bus can deliver, but a flawed version of basic aerodynamic common sense that used to be designed into the basic airframe, but now resides in a black box.

In days of yore when flying 'big iron', you would have to trim up next to the stall either manually or with the trim button, and then give a firm heave on the controls for a prolonged period of time to get well into a stall (Think something like the DC-6)
Then along came the jets with their higher control forces and hydraulic boosted, then completely irreversible controls followed causing our control forces to be generated artificially.
Then we had the T-tailed aircraft with their pitch up in the stall that need protective devices to certify the airframe and we became used to flying aircraft with bad aerodynamic characteristics as long as we were protected from the consequences.
Now we have fly by wire aircraft with their C* (attitude stable) and C*U (speed stable) control laws that have permitted straight forward implementation of flight management systems, but what have we lost? Could it be that the smarts that used to be built into the basic airframe design that limited control authority to that which was necessary for the worst condition, (full flaps and forward cg in the case of nose up authority) didn't make the migration into a little black box because it was too hard to do so? That is what I think happened in the A330 Alt 2 law THS limits.

Glad Rag, look over in the Tech AF447 thread for the sidestick diagram.

lomapaseo

depends on the consequences

It it were to be a 100% probability that the consequences would result in an inability to complete a safe flight and landing (somewhere) I would agree with you.

Typically the 1 in a million failure category still has other systems available to get you back on the ground 9 out of 10 times.

In the long run it's easier to work this 9 out of 10 back up redundancy than to try to make a ten fold improvement in the original malfunction causes

HazelNuts39

Glad rag,
You'll find it at AF447 thread no.7 page 27 post 523.

bubbers44

I think there is a 100% probability that if 100 airliners lost airspeed at 35,000 ft all of them would end up the same way if you pulled full back and held it for over 3 minutes. All pilots but one would have held attitude and power and survived.

One pulled full back and crashed. The others aviated as trained. Seems simple to me. We don't need better automation, we need better pilots. How are the new hires today doing? Can they hand fly or is that not required any more?

infrequentflyer789

I gave a list of stalls (off top of my head) that were mostly not sidestick and not FBW but all (I think) involved pilots pulling back in reponse to stall warning.

I quote an investigation report of inappropriate response to stall warning that states that pilots were not trained in stall recovery and that this was a "minor safety issue".

I say it'll carry on until it's acknowledged that pilots pulling back in a stall is a major problem, and you come back with "it's a FBW problem".

Meanwhile others post stuff like "None of us in any Boeing would have stalled". [ yeah and the Ethiopian guys were shot down ].

Q.E.D.


You can open your eyes and mind to the real problem, or carry on believing the engineers have screwed up between the stick and the surfaces and there's no problem between the stick and the chair, carry on stalling, carry on pulling back, carry on dying. Gotta keep the accident investigtors in a job...

bubbers44

I think it is the most basic thing a pilot learns is stall recovery. It is so simple, release back pressure and if necessary push forward. If a pilot doesn't know that he isn't a pilot, he is a robot. Unfortunately some Airbus pilots have become robots that can't fly any more without a computer to do what they ask it to do.. SAD

CONF iture

No auto trim up trap and a much better chance to improve things, intentionally or not :

iceman50

MACHINBIRD

That is where you are totally wrong. Tried it in the sim and it takes great effort on the sidestick and and effort that has to be maintained!!

Wrong again it makes it more stable.

glad rag

Thanks Hazel, thanks very much!

CONF iture

I did here.

No effort at all on the sidestick to hold in the stall ... the almost full NU trim was taking care of it.
Apparently, same thing happened for AF447, THS was already at 13 degrees up when full back stick was maintained.
That undesirable auto trim operation has played a crucial role in the outcome of AF447.

stepwilk

A good friend of mine, president of our local Tuskegee Airmen chapter, is a check airman for Continental on 737-800s. He told me the other day that he encourages pilots to hand-fly an entire arrival and approach whenever possible.

VGCM66

Report: Cobham B712 at Kalgoorlie on Oct 13th 2010, stick shaker on two approaches

Now what? Redesign the B717-200? Expend gazillions of $ so the FMC/FMS warns the pilots when they introduce/punch the wrong/bogus data?

The buck has to stop somewhere and the sooner the better.

Cheers,

mm43

Which was supported by Owain Glyndwr's theoretical analysis - in part...

Machinbird

Iceman.
My first impression was that you had done your sim evaluation in a Boeing type sim, but I see you list yourself as a 'Bus pilot, seat 0A, so will give you the benefit of the doubt.

It takes effort to hold the stick back in the 'Bus to get the nose up, but once it is there sufficiently high, and the trim runs up, it takes little effort as Confiture describes.

Do not confuse the ease of holding an airspeed in your 'Bus due to the attitude stability with possession of natural speed stability. Your 'Bus is a C* aircraft and is attitude stable, not speed stable. That got AF447 into trouble in Alt 2 law. Once the nose got pointed well up into the sky that aircraft was going to decelerate, even with no further stick input, and the trim was going to run up to the limits in blind obedience-no protections.

If you don't believe me, try flying the 'Bus sim at 12-15 degrees nose up in Alt2 law at altitude. Once there, it won't make a difference what you do with the power. As long as you keep your hands off the pitch input, that aircraft will decel to the stall and keep on decelerating, and the trim will run as far up as it can.