Peter wrote:
Neither of them tried to do the right thing, which would have been setting power+pitch and letting the plane get on with it.
Well, the PF failed at that. There might be two of them but only one at any given moment flies (PS: well, is supposed to). He set power, but I think too much, and pitched up too much for some reason. PNF told him at least once (I think it was several times) to watch the speed (not sure if he mentioned altitude as well) and he did try the correct recovery himself, but IIRC he didn’t take control the proper way and his colleague was interfering with his attempts probably without him realizing it (since he made no comment about it). So PF failed at a procedure they never trained in these circumstances (they would probably have to open up the manual to find out the right settings as I think they depend on altitude and mass), perhaps a bit ham-fisted, and PNF failed at properly taking command and failed to notice warnings of conflicting inputs. I don’t recall them discussing the situation (beyond I don’t know what’s going on, I lost control, etc.). It was a CRM failure. One confused pilot managed to confuse the second pilot. Who knows how PNF would have handled the pitch and power problem. He never got the chance. But both he and the captain wanted to do the right thing as far as recovery from the stall goes.
This is off topic. Anyone interested can read the BEA report.
From William Langwiesche’s Vanity Fair article.
http://www.vanityfair.com/news/business/2014/10/air-france-flight-447-crash
This is not the time for a dissertation on the Airbus flight-control system, which is criticized by Boeing, but to the extent that it embodies a mistake in design, it is that the pilot’s and co-pilot’s side-sticks are not linked and do not move in unison. This means that when the Pilot Flying deflects his stick, the other stick remains stationary, in the neutral position. If both pilots deflect their sticks at the same time, a DUAL INPUT warning sounds, and the airplane responds by splitting the difference. To keep this from causing a problem in the case of a side-stick jam, each stick has a priority button that cuts out the other one and allows for full control. The arrangement relies on clear communication and good teamwork to function as intended. Indeed, it represents an extreme case of empowering the co-pilot and accepting C.R.M. into a design. More immediately, the lack of linkage did not allow Robert to feel Bonin’s flailing.
Yes I meant airspeed data.
Neither of them tried to do the right thing, which would have been setting power+pitch and letting the plane get on with it.
I am sure this is a good feature but I don’t think it will reduce the number of accidents because most Cirrus chute pulls were not simple stalls.
My understanding is the system is disabled within 200ft agl (stand to be corrected on height) to allow for landing but essentially after the base to final turn risk
There isn’t an unclassified terrain database that’s accurate to 200ft in 3D. There may be for the USA but many countries objected to the release of the more accurate SRTM data.
Peter wrote:
AF447 happened due to a loss of airspeed
They were in alternate law, it was a stall held pretty much until they hit the water. Big chunk of the time attitude was so crazy computer couldn’t believe it, quite literally IIRC (meaning computer considered some inputs invalid), which resulted in stall warning activating whenever the right input was provided and shutting off when the wrong one was provided.
But you might mean loss of airspeed data. The actual loss due to icing was brief. I don’t recall the numbers off the top of my head but I think it was less than a minute. PFD was IIRC still indicating, I think even speed which was unreliable some of the time. They normally have AoA protection but not in alternate law and the low speed stability function (which would push the nose down to recover speed) which is still there is overridable by stick (but I don’t know the differences between different Airbus models). The icing episode didn’t cause the stall, it just took away the protection that would prevent it. So much for your “no plausible scenario”.
SR22 manual (PS: I mean G1000 manual for SR22) IIRC says it uses stall warning system for underspeed protection. But I don’t know how exactly it’s done. Obviously, if the pilot overpowers or overrides it (and this is not a FBW machine where just providing input overrides the system), it won’t help him.
Peter wrote:
two pilots who didn’t understand the aircraft systems
I think you’re underestimating the psychological element and CRM failure. One of them tried to do the right thing but they were working againts each other at that point.
Peter wrote:
Even the Airbus would not, upon getting unreliable airspeed, apply 2.5 degrees up pitch and 80% N1 (or whatever).
Well, it wouldn’t since autothrust signs off along with a host of other systems.
I had this engage on me twice whilst hand flying tight maneuvers (once in pitch exceeded >X and once because bank >45). It first applies a stick force and if you continue to exceed the envelope, you get an aural message ‘autopilot engaging’. It then reverts to straight and level and you must disengage the AP button to resume flying. Augmented stability is a ground breaking technology that will materially reduce the accident rate – it will take a generation or two to become acceptable (like the chute). No autothrottles are required in a stall because you don’t stall, the pitch servo reduces your pitch and points you towards the ground – gently but in the full flying envelope (1.2vso – I think). My understanding is the system is disabled within 200ft agl (stand to be corrected on height) to allow for landing but essentially after the base to final turn risk. Therefore, I suspect it relies on a terrain database and GPS signal, but again, this is an assumption that may be incorrect.
For every pilot it doesn’t save from LOC, it will save 99 others – therefore, it will enhance safety and make flying more acceptable. Now, if only our engines weren’t always too rich or too lean!
Aviathor wrote:
Is there any other way or flying? 400ft A/P ON
you leave it that long to switch the AP on? Rotate, confirm climb, CWS on 
(just joking for those who think I do fly like that 
)
You don’t but the system can see where throttle / thrust is and if the throttle didn’t move and the attitude was steady I guess it should be able to diagnose zero airspeed as a fluke indication.
True, but you don’t have auto throttle here so no control over power. Even the Airbus would not, upon getting unreliable airspeed, apply 2.5 degrees up pitch and 80% N1 (or whatever).
Peter wrote:
The SR22 envelope protection will have the same problem if you lose airspeed
Not necessarily. It shouldn’t be too hard to have the system revert to flying fixed pitch and power if the airspeed suddenly packs up and GPS speed remains constant. After all if pitot speed suddenly goes to zero with constant attitude what chances are there for it to be a valid indication other than hitting a very solid obstacle.
AF447 happened due to a loss of airspeed coupled with two pilots who didn’t understand the aircraft systems (they were just button pushers). The SR22 envelope protection will have the same problem if you lose airspeed (e.g. simply forgot to turn on pitot heat) and the pilot is not, shall we say, performing sensible actions.
It’s a good thing for sure, but the statement
a stall should be relegated to the history books due to ESP and Underspeed Protection. ‘Pros’ will put down these technologies but they are the future (and wonderful).
is over-selling it, IMHO. And I am not a “pro”
