SIM Experiences
I wanted to make it a little easier to see each of the SIM experiences, so I put them all together in this post. Each experience is followed by answers to questions by other posters. I didn't post the questions (saving some space) but they should be evident from the answers. Hope this helps....
From CONF iture:
As we got little extra time in the sim today, we did experience a full stall from FL350.
Here is what I can report from the experience :
From the STALL warning we kept a light aft pressure on the sidestick
It was not long before we got a negative vertical speed of 15000ft/min
THS went to 12 deg UP under STALL warning
As we decided to exit the stall, full fwd pressure on the sidestick was applied
But we were unable to lower the nose
THS did not move
THS was then manually rolled fwd
Nose came down
Exit was then possible
I can't remember all the details, too much stuff to look at.
Thrust was kept at idle all the time.
Early fwd pressure on the sidestick at initial STALL warning should prevent a stall to develop.
From DozyWannabe:
What we had was an A320 sim rather than an A330, which comes with some key differences - the most obvious of which is the lack of Alternate 2, the nearest equivalent being Alternate without speed stability, and a different underlying architecture past a certain point.
The first experiment involved setting the conditions to night IMC with CBs in the vicinity, having set the autoflight to take us to 35,000ft and hold us there. We had a friend of his who is a TRE sitting in the LHS to provide guidance and monitor what we were doing. He then failed the ADCs, leading to autopilot disconnect and a drop to Alternate (without speed stability) and we tried to follow through and maintain a 15 degree pitch angle. Things we noted:
I'd suspected it would involve considerable effort to hold the sidestick there for a significant amount of time, but I was genuinely surprised at just how much.
The zoom climb occurred exactly the way we expected
The Alternate Law (no speed stability) on the A320 seems to have a hard trim limit of 3 degrees nose up
It was definitely possible to hold the aircraft in the stall with 3 degrees of nose-up trim and full back stick, but it required effort
The aircraft wanted to nose down and recover itself, and with about 10 degrees of nose-down maintained with the sidestick at the moment we passed about 30,000ft, we managed to effect a recovery with the speed coming back up to a point where we could level out safely at about 20-25,000ft judging by the standby altimeter.
The second experiment was the same as the first, but as my pal had noted, the A320 has a hard limit of 3 degrees NU trim available via autotrim in the secondary Alternate Law. We tried again, this time winding in full nose-up trim manually just prior to the point of stall. This time:
The aircraft seemed more willing to hold pitch with the trim at full-up, but to hold it at 15 degrees still required considerable effort
We had to add a touch of rudder (on the TRE's advice) to control the roll.
Despite full nose-up trim, we elected to start a recovery as we came down through about 35,000ft this time, just to see if it was possible using sidestick only
Following the same 10 degree nose-down sidestick demand as before, the trim rolled forward with the sidestick demand, returning to around neutral within about 5-8 seconds, and we came out of the stall as before.
Based on this, as far as the A320 is concerned at least, recovery is possible using autotrim via sidestick only even when the trim has been manually wound fully nose-up. Given more time we'd have liked to see what happened attempting recovery at lower altitudes, but the general take-away seems to be that with sufficient forward sidestick demand it is possible to recover from stall even with trim forced to where it's not supposed to be.
Further details I've just been reminded of - the stall stabilised at approx 180kts IAS on the sim control with the nose-up trim at 3 degrees (the A320 hard limit). With full nose-up trim the stall was similar, but stabilised at approx. 160kts IAS. The Stall Warning was not only clear, but so loud that the TRE had to cancel it with the Emergency Cancel button in order for us to hear each other. On the second (full nose-up trim) experiment, all I had to do was briefly glance down to my left to see the trim roll forward - smoothly and *very* quickly - following recovery via sidestick pitch down.
Some questions answered:
Having conferred, we loaded extra fuel so that the FMGC showed MAX ALT FL379. C of G was 32% MAC. The ROD in our experiments maxed at approx 6,000ft per minute, with the VSI needle turning amber in the PFD. One of the reasons I hope someone will perform a later experiment will be to see how leaving the recovery till later in the sequence will affect the ROD, and hopefully also find out how a 40% MAC CoG will affect things. The caveat here is that the later you leave it, the further outside the tested flight envelope you go, and the more divergent the sim's performance from the real thing will become.
After the initial NU pitch increase (induced with approximately half back-stick, as in the DFDR traces), we triggered a very short "G" induced stall warning as we climbed, then when the real warning sounded continuously (as happened in the AF447 scenario) we applied TOGA and held 10 to 15 degs pitch on the sidestick - during which full deflection was required in order to come close to maintaining it - as I said, the nose wanted to come down naturally if I released pressure for even a split-second.
Initially, autothrust dropped to Thrust Lock. We pulled the thrust levers back to match the thrust, but as we moved them the thrust increased slightly. The TRE then deliberately staggered the TLs slightly to induce a roll to the right which we trimmed out with rudder and the slightest touch of aileron.
From PJ2:
With weights, CG, SAT mirroring AF447 and a bit of turbulence, following loss of airspeed (all 3 ADRs out), the sim was pitched up at FL350 and held in the climb until stalled, (THS reached 13.6deg). Shortly after the stall we returned the ADRs for use during the balance of the exercise, (to see the FPV during the stall).
Post-apogee (approx FL360), full forward stick was applied and held.
At FL330 the pitch was 8deg ND.
At FL310 the AoA (using FPV) was approx 40deg and the VSI was 18000fpm +. Pitch was about 14deg ND which was all the pitch that could be obtained.
Pitch slowly reduced to about 10degND still with full forward stick. As it was held the THS unwound and returned to normal settings.
We could watch the AoA reducing as the FPV slowly climbed "up" the PFD from past the red ND warning arrows below 30deg pitch marks.
Thirty seconds after the first Stall Warning passing through FL270 the AoA had reduced to 30deg, descent rate was 16000fpm.
Ten seconds later at FL255 the AoA was 12deg, CAS was 250kts, VSI was 7400fpm.
At FL245 the stall warning stopped 40 seconds after it began, the AoA was 10degND, M0.658, VSI 7000fpm down, CAS 278kts.
From an AoA of 40deg to 10deg took 24 seconds and about 6000ft. This exercise took about 22000ft; some were less.
Overspeed was never a problem nor was a secondary stall if one was gentle, (took about another 6000ft IIRC)
Some questions answered:
Normal cruise pitch attitude is between 2.3 and 3deg depending mostly upon weight. A pitch up to 5deg pitch attitude (+2.5deg) results in about an 800 to 1500fpm climb and a gradual loss of energy if held long enough. The UAS QRH checklist and the FCTM cautions strongly against holding such pitch attitudes for long and advises to get the QRH out quickly and set pitch and power. The FCTM also states that the Memory Items are not to be done if the immediate safety of the aircraft is not impacted.
For the purposes of the exercise there was no "judging" of how much to pitch up. We pitched up high enough to stall the aircraft. Fifteen degrees would do it, sometimes we were higher.
The overriding impression of these sessions was how quickly things occurred and how fast was the altitude loss.
My comment about "how quickly things unfold" is an observation on the amount of time it took to lose control. Time is always "relative to perception and familiarity". When a pilot is highly trained, highly experienced and very familiar with his/her airplane, the flow of even huge amounts of information and lots of events flow much more slowly, perceptually, because the mind anticipates much more effectively and easily, (depending upon other factors such as distraction, fatigue) than if one is relatively inexperienced in such circumstances.
In terms of this loss of control, while it unfolded literally over a period of about 40 seconds, oddly that is tons of time to do something, but it is not a lot of time for assessment, discussion, action.
In re the sim exercise, power was at various settings (though never TOGA). Also, there were variations in altitude needed for recovery. In one exercise we "did nothing" and the aircraft happily remained in stable flight at FL350 as power remained in "TOGA LOCK" (last setting before disconnect) and the pitch at 2.5deg, approximately.
gums, you're right about the sim not really being able to teach this kind of thing - you can't feel "the mush"...the slight delay in responsiveness in both changes in attitude and flight path even though the subtle indications may be accurately simulated.
The exercise was a worst-case - fully developed stall, late recovery attempt, thrust was not idle. As I mention to HN39, a smart recovery, (as in brisk forward stick at the first stall warning blip, held fully forward without variation, thrust at idle), can be made which reduces the altitude required. It's still going to take a lot of altitude to a) regain the AoA and b) regain the energy, (due low availability of excess thrust, so its height for energy, initially).
Thanks HN39...the FPV symbol was 10deg below the line dividing blue and brown on the PFD, which to me indicated an AoA of roughy +10deg while the aircraft was still descending rapidly, so it was my clumsy writing even though I think the meaning came through for most others. On the stall warning, in fact the first exercise there was no such warning because we had all the ADRs off, then on for the FPV later - we did it again using a different failure method to get the sim into Alt 2...these are details behind the larger exercise but technically correct - my posts are almost always too long as it is.
In my non-engineering view, the sim "behaved" as I expected the airplane might. I don't have experience with the Cooper-Harper scale although I am familiar with it and my own characterizations of the airplane were probably generous. The warning and cautions which accompanied the CAS and ADR failures were less distracting than I had anticipated.
I gathered from the session that it's difficult to simulate the loss of pitot/static information and get the exact same failures/ECAM messages and the method that got closest was failing ADRs and then re-instituting them to some degree. It didn't affect sim behaviour but it does affect available indications. This is a long way of explaining that I can't answer your question with any meaningful information. On one stall we had no warning which was because all ADRs were still failed and on others we had full FPV indications...a bit ad hoc in this area.