I believe 14,000 ft is the highest that any manufacturer flight-tests stall characteristics nowadays.

Couple that with the low-speed limitations of Computational Fluid Dynamics, and we have a whole flight regime for which wide-ranging reliable data doesn't appear to exist.

And plenty of posters on here seem to agree e.g. adding technology to solve every problem?

I would disagree with the underlined statements:
A: I do not believe it "unclear" how to resolve situations, but people have either failed to follow the manual / their training, or they have done something completely unpredictable.
B: It is not essential, IMO, to (completely) "understand" what is going on under the hood. Not even what law the aircraft is in. Yes - a level of knowledge is required, and will help in exceptional circumstances. But if you fly the aircraft sensibly, remember it is still an aircraft and not a computer, and apply basic flying skills, then the finer points of FBW are (as designed) usually invisible to you.

I do agree with the basics of this - initially the benefits of FBW showed up as "protections" prevented some accidents (albeit there was also a learning curve), but there was still basic airmanship and flying skills about.

Now we have a new influx of pilots, who only know FBW, rarely handle the aircraft, the industry relies on the automation. When the automation lets them down, they have nothing to fall back on. Even the older generation pilots have been "deskilled" as well.

GPS on corners
 

Isn't this used on some fighters to sense attitude? Phase lock, phase differences? Maybe on the mil band only?

I would have thought the logic behind stopping the aural stall WARNING when aoa becomes untrustworthy makes sense EXCEPT when an approach to stall has just been sensed. If the warning is blaring away seems more prudent to let it continue. Think the software is missing a IF....THEN branch on this one. Also, if high THS is a very unusual state for normal ops, is there a warning to draw attention to it?

Inquisitor

..out of the profession for many years now but don't necessarily
agree CFD is limited to low speed aerodynamics or altitudes.
no doubt even faster computerd are required and different
mesh/models but think it is a very advanced technology now.

..unless you know different.

HarryMann,

Not sure, as I have no expertise in the field myself. I was referring to what somebody far cleverer than I told me when visiting a wind tunnel test facility. He seemed to be saying that in the low-speed, high-alpha regime particularly, there were simply too many variables to produce a solid deterministic model, as opposed to computers running out of steam.

Apparently they have it pretty much nailed for high-speed stuff, though.

Inquisitor

Sorry I misread...

However I know a bit more about that regime and disagree still :)

separated flow is complex and agree demands lots of computing power

it's a matter of filling in the gaps with real w/t models studies.

I doubt there's a lot not known.

I don't believe these are the issues here:

isn't this about the cockpit, training, operational procedures human
response etc,

It's about a lot of things in my mind HM.

I currently work in the unmanned arena, and am desperately fighting those who think that more computers and more automation is the answer to everything.

My own view is that that we have simply replaced one failure mode with another.

I'd be interested to know what's out there in terms of real-world collected data, particularly wrt high-alt, high-mach, high-alpha, low-IAS scenarios? My current belief is that a wide dataset here is absent, save for that collected from real-world accidents?

TheInquistor;
For those carriers doing FOQA/FDM from engine-start to engine-stop and who retain their deidentified data for some period of time, there is a wealth of information for the period and for the "events" you specify.

Sharing such data is another matter. A number of projects have attempted to do this but so far nothing has emerged as a distributed archive of common types. How data is handled, confidentiality, legal implications and legitimate concerns as to data-use impede data sharing. But it's out there.

Interesting idea.
In fact GPS is amazingly accurate when used differentially to calculate attitude down to sub mm accuracy. The timing pulses in the GPS satellite data packets are used to generate relative attitude information instead of the spacial reference data. This has been demonstrated successfully in many small civilian aviation devices.
The problem here is that the wings have tremendous flex especially at the ends. Even the fuselage has a significant movement at the ends. This would have to be compensated for - maybe with laser level.

What is new here ?

What do you think you would be gaining that you don't already have from the INS's ?

Why is this gps attitude capability seen by some as a new fix ?

The existing 3-axis ring laser gyros already pump out all the spatial data you could ever need, with all rates included.

The point is that when an Airbus goes into alternate law, it has less stall warning and alleviation devices than a 1960s Trident. That is not an advancement in safety.

I expect that when the AB was designed, it was not expected that so many aircraft would degrade from normal law to alternate law. But here we are, yet again. It would seem clear that the degraded systems need a stick-shaker/pusher to back up the aural warnings (or a thrust reducer, to lower the nose).

As to Nigel, who says a pusher or thrust reducer would not be good on take off ( :{ ), this never stopped the Trident having pushers, and not having any problems with them. Besides, AB could easily limit the action to greater than 2,000 ft. And as far as I can see, this would not add weight or cost to a standard AB. I am sure that both stick push and thrust reductions, for approaching the stall in alternate law, could be made as a simple software change.

Absolutely! What accident are you trying to prevent by suggesting sticking GPS's all over the ship? All these accidents had perfectly functional attitude indicators right in front of the noses of the pilots.

It was obvious in the case of AF that neither pilot took any notice of their attitude indicators. Attitude is everything - something that is trained from the first minute of basic IFR training.

If that is being de-trainined in Airbus types then that is the heart of the problem. Forget the more/less automation arguments - if you are hand flying an aircraft, your eyes are on the attitude indicator, with a brief and frequent scan to other instruments such as airspeed and altitude. If you are monitoring an autopilot, not much changes.

In the case of air data problems such as unreliable airspeed including simultaneous stall/overspeed warnings, you are not distracted by the warnings, you simply change your scan from attitude/airspeed/altitude to attitude/thrust until it's sorted.

It just ain't that hard.

Air Asia Indonesia Lost Contact from Surabaya to Singapore
 

Silverstrata,

Exactly HOW does your stick pusher know it is approaching the stall, perhaps it will use the AOA probes. Perhaps it was the ice on the AOA probes that generated the reversionary mode in the first place. Or perhaps it will take it's info from a failed sensor and just push anyway.

That's not actually true in most circumstances. There have been experiments with highly specialised GPS receivers tracking L2 Phase for aircraft attitude purposes that worked well, however general GPS is simply not good enough.

Modern drones have experimented with thermal horizon detectors which work quite well in flat terrain, but have problems in hilly terrain.

The current alternative to INS is a combination of GPS and 3D accelerometers / rotation sensors that provide quite accurate attitude and location information. They do not meet full INS accuracy but at under $100 a sensor unit they are extremely good value.

ASRAAM answers the point I have been trying to make... Alternate Law is, by definition, a Reversionary Mode. It is Reversionary for a good reason, and hence why Stall Protection is degraded.

If the system integrity in Alternate Law was high enough to justify stick pushing, then it would be called Normal Law ;)

Look at the latest OEB - the effects of a "Stick Pusher" in Normal Law :ugh: A320 uncontrollably diving to 4000'/m. If there are hidden flaws in Normal Law, how could you write a Safety Case for such a Pusher in Alternate Law?

What a contrast.

One thread intent on denigrating automation in the cockpit, and another bashing the humans who (possibly) shut down the wrong engine.

In either case a flyable Aircraft has crashed. - I don't know how my computer works, but I can operate it until it goes wrong. Where's the weak link?

<<<I don't know how my computer works, but I can operate it until it goes wrong. Where's the weak link?>>>

I do know how my pencil works and I can balance my checkbook without problem.

Where is the weak link?

IT IS SIMPLE, the weak pilot is the weak link. The pilot must be able to do it all, until the plane is safely on the ground.

Automation can reduce stress and strain in normal ops and assist in emergency ops. This will reduce the need for rest after the flight. BUT a pilot who takes his plane to MAA (max authorized altitude) and can't hand fly it there is fooling himself!

skyhigh:

Can you elaborate a bit on that one?

elaboration


for aterpster:


What I am trying to get at is the ability of some pilots to command their autopilot to climb to the maximum authorized altitude of the plane (service ceiling so the ancients like me liked to say) and would be unable to hand fly the plane at that altitude.

So too, taking your plane into any condition that required the use of autopilot and could not be flown ''by hand''.

to be sure, if regulations require the autopilot to be used (rvsm or Catii apch) you use the autopilot, but you must be able to actually hand fly the plane there in case the autopilot quits.