Humbling sim experience

[misd-agin]

You can't hope or will the airplane to fly. If it's not flying it needs less AOA. Period.

You can't say "I don't like the nose that low'. If the wing needs AOA reducing AOA is the driving force, not some desire for a 'normal' pitch attitude.

Did loss of airspeed in the sim. During recovery we had 10 degrees nose low at max power(actually restricted to 75% N1 due to EEC failure resulting from loss on data input!). CKA said "don't put the nose that low." Silly boy, AOA gauge demanded it. Pitch attitude was being driven by the AOA gauge.

If you've done acro or fighter flying you've probably seen amazingly slow airspeeds. Less than 1G, and low AOA, is what allows that. I've seen the airspeed indicator pegged against the stop (<60 kts), when the actual stall speed was 120+ kts, without being stalled. But not for long.

[aguadalte]

Airbus Drivers,
Next time you go for a sim check, just ask your check air man to freeze all of your pitots during a climb (lets say passing 30.000'). Everything functioning normally, with AP ON...
Since pitots were frozen at the same time (no significant speed differences between ADR's), your ECAM will stay silent until high speed protection actuates and takes your aircraft into a deep stall...
You will have to force your aircraft status to change to Alternate Law, in order to be able to push your nose down...
That experience will tell you a lot about the aircraft you're flying...

[A-FLOOR]

Originally Posted by flyburg

Nope, sorry, can't tell you how they simulated it. Will see if I can't find out.

Greetings.

The headwind/tailwind scenario as a result of the erroneous TAS computations with changing altitude with blocked pitots is absolutely realistic. (I work for the company that built your 747-400 simulators) The actual winds set the simulation were probably either calm or stable.

I urge any airline pilot who has never seen this effect firsthand to give it a try the next time you're in the sim. As flyburg has said, it is a real eye-opener with regards to AF447.

[Lyman]

AFLOOR, Is there any reason to include ICED probes? Not to? What do you think of the possibility 447 may have lost her reads via airmass volatility alone?

[AlphaZuluRomeo]

Originally Posted by aguadalte

Since pitots were frozen at the same time (no significant speed differences between ADR's), your ECAM will stay silent until high speed protection actuates and takes your aircraft into a deep stall...

Uh?
Doesn't high AoA protection have a greater priority than overspeed protection

BTW, I also was under the impression that getting 3 pitots freezing at exactly the same time is... let's say extremely unlikely. Wrong?

[Lyman]

AZR

Hi. I recall from the "Another 447 avoided" that overspeed warning is primary over STALL warn...

Lyman

Fwiw: if the probes are blocked for the sim ride, simultaneously then it is not a true 447 profile....as above, freezing all three at exactly the same time is virtually impossible. I believe that is why BEA will not say ICE blockage caused UAS. If airmass/turbulence, or ICE, it happened concurrently, and frankly, IMHO, for all three to ice at all via micro granulae is far fetched. Any transition from 100 knots on the nose to 100 knots on the tail would cause extreme disruption at the nose, and the pitot probes, ( to a lesser extent, the statics).

[bubbers44]

We know unqualified pilots flying together is unsafe so if the regulators don't fix it maybe the press will have to. We will just have to be patient for another couple of AF type crashes. Sad, isn't it?

[Machinbird]

Bubbers

We know unqualified pilots flying together is unsafe so if the regulators don't fix it maybe the press will have to. We will just have to be patient for another couple of AF type crashes.

I'm not trying to cause great mischief with this question, but how will we tell the qualified from the unqualified pilots? Both types will be wearing the uniform, sitting in the seats with the forward view, and carrying the ATP certificate in their wallet. Just what criterion will we be using?

I'll bet there guys&gals out there who fully believe they are qualified but would not fit either my or your definition of qualified.

So how do we get them properly qualified?

[bubbers44]

My airline, 30 years ago, had me take a check ride in a 4 engine turboprop I had never flown and do ILS's to a single engine approach to get hired. That is how you can find the pilots you want. We hand flew all approaches so the computer monitors would not be accepted for my job. That is how you hire a real pilot.

[bubbers44]

Yes, the airlines are hiring the monitor pilots because they are cheap. Maybe we can raise the standards to what we had 30 years ago. Maybe we need to see if the pilots now flying can handfly before we let them fly together. Automation is great but it should just help you fly, not be your only way to fly.

[elrey_b_jepp]

AOA

I doubt the Attitude indicator and FPV can show you the AOA.
The FPV has a trend vector with power inputs, therefore your nose may be level but FPV down like on an approach. That doesn't give you the AOA, am I right?

[HazelNuts39]

Originally Posted by AZR

I also was under the impression that getting 3 pitots freezing at exactly the same time is... let's say extremely unlikely. Wrong?

In this case they don't have to freeze at the same time, but they have to freeze in the same manner. If a pitot is blocked at the intake and at the drains simultaneously, you wouldn't notice anything until you change altitude.

[Young Paul]

1) I'm not convinced that this is simply a question of more/better flying experience. I agree about insufficiently qualified second officers, but the belief that there is something fundamentally missing in airline/type-rating flying training to me ranks with me alongside the idea that fly-by-wire is somehow "less safe". For the one-in-a-million event which led to this, there are the one-in-a-hundred events where overbearing, arrogant captains ended up effectively flying airliners "solo" because they had no confidence in their first officers (ie. were unable to operate an airliner as a crew, as the aircraft had been designed to).

2) Even if it is, I don't know how people expect to change this. There is much less military flying now - should tax rates be put up by 2% to pay for increased defence expenditure? Should pilot qualifications be increased in cost by £10000 to provide a greater diversity of experience? Who is prepared to pay for this? And how could anyone measure whether the extra training provided suitable economic benefit? And what extra experience should be provided? How would you know that you had provided all the training that would be needed to convert an "unsurvivable" event into not only "survivable" but "recoverable"?

3) The idea that thirty years ago we were in some kind of golden era where pilots were real pilots, men were real men and blahblahblah, is simply not borne out by the facts. The absolute rate of accidents has fallen and is falling - see the graphs on this page - whilst the number of commercial flights has increased. The argument that "we need pilots with somehow 'better' experience" is not statistically supportable.

To my mind, the approach of identifying a threat, then providing training to deal with it - steered by regulators and airlines - is entirely appropriate. The process that is happening now will ensure that professional pilots worldwide will have a greater appreciation of this combination of threats - it provides the extra experience that people say is missing.

[HazelNuts39]

Originally Posted by Lyman

I recall from the "Another 447 avoided" that overspeed warning is primary over STALL warn...

Perhaps you misread. Overspeed warning took priority over A/P disconnect warning. There was no stall warning because the airplane remained in normal law.

Any transition from 100 knots on the nose to 100 knots on the tail would cause extreme disruption at the nose, and the pitot probes, ( to a lesser extent, the statics).

It wouldn't cause disruption of pitot or static, but it would immediately deprive the airplane of almost all lift and drag. IOW in AF447 you wouldn't be able to pull 1.6 g at stall warning.

[Meikleour]

ray.boeing: No. The FPV will give you AOA indirectly. It is the difference between the aircraft attitude and the FPV angle. However I am under the impression that the FPV is not entirely inertially driven so may have errors added when the pitots/statics are obstructed.

[Microburst2002]

Which brings to mind is question:

Can static ports become frozen in flight? I know pitot tubes can, but static probes?

And are the chances that pitot tubes will freeze much eqrlier than static ports? i would say 99%. I deem that icing related unreliable speed situations in cruise flight will always be pitot related. So you will be able to rely on Altitude indications and FPV. Angle of attack can be derived from the difference between body angle and FPV.

Aguadalte

That scenario of the false oversped triggering undue high speed protection, when you are actually flying very slow, is dreadfull. But I believe you can still use manual pitch trim to achieve pitch down.

By way, what will happen in a Boeing in the same circumstances?

As I always say, the most difficult partof an unrliable speed scenario is becoming aware that speed is unreliable, in the first place. If you don't come to that conclusion timely, you are fu*ked.

Then, My opinion is that the procedure needs more refining. It is too "take off oriented". You can be at high level with "safe conduct of the fligh" absolutely "impacted". Then what do you do?

[AlphaZuluRomeo]

Originally Posted by Lyman

AZR
Hi. I recall from the "Another 447 avoided" that overspeed warning is primary over STALL warn...

Hi Lyman.
I'm sorry, you recall wrong here.
High AoA (Stall) protection has priority over other protections (IIRC, I stand to be corrected and hope I will not on that topic).
Stall warning has priority over other warnings.
Why? Because stall was deemed more dangerous.

Originally Posted by HazelNuts39

In this case they don't have to freeze at the same time, but they have to freeze in the same manner. If a pitot is blocked at the intake and at the drains simultaneously, you wouldn't notice anything until you change altitude.

Hi HN39.
AFAIK, they have to freeze at the same time and in the same manner if to fool failure detection mechanisms (comparing in real time values from 3 probes).
My point was: such an event in real conditions is extremely unlikely, that's why detection are based on that assumption. Don't you agree?

[HazelNuts39]

AZR,

If the drain of a single pitot is blocked, and the intake of same pitot almost at same instant, then the total pressure inside the pitot is 'frozen', no change to detect. Same for a second and third pitot some time later. The IAS changes when the static pressure changes, i.e. the altitude. IAS increases with increasing altitude, and vice versa. The IAS from all frozen pitots change in the same manner, no differences to detect.

What IMO makes this scenario somewhat unlikely is the absence of turbulence in the simulation. Turbulence was present in all UAS incidents studied by BEA, and would cause altitude variations causing airspeed anomalies that would trigger detection unless several pitots froze simultaneously.

[Meikleour]

Microburst2002: Yes, static ports can get iced over in flight. In the `70s there was an incident invovling a Trident operated by BEA/BA which experienced freezing rain runback on the fuselage which blocked the static ports. It was in the BNN hold at the time. When the stick push operated it promptly dived through several levels of the hold missing other aircraft. My neighbour at the time was the F/O.

Regarding manual use of the THS to control pitch - yes it is always available and in some situations may be needed to overcome the ineffectiveness of the small elevators. This in my opinion is one of the great untaught "gotchas" of the FBW Airbus`s. The THS is NEVER NORMALLY moved by the crew in flight but as AF447 found out it may have helped. The same goes for the A320 loss at Perpignon.

[A-FLOOR]

Originally Posted by HazelNuts39

AZR,

If the drain of a single pitot is blocked, and the intake of same pitot almost at same instant, then the total pressure inside the pitot is 'frozen', no change to detect. Same for a second and third pitot some time later. The IAS changes when the static pressure changes, i.e. the altitude. IAS increases with increasing altitude, and vice versa. The IAS from all frozen pitots change in the same manner, no differences to detect.

What IMO makes this scenario somewhat unlikely is the absence of turbulence in the simulation. Turbulence was present in all UAS incidents studied by BEA, and would cause altitude variations causing airspeed anomalies that would trigger detection unless several pitots froze simultaneously.

The total pressure will freeze, but remember that the static ports were available and working 100% all the time in the AF447 scenario. IAS is still equal to Pdynamic, which is derived by substracting Pstatic from Ptotal.

The pressure variations in the turbulent air will still find their way to the IAS via the static ports, and this is of course also the reason why climbing will give you the impression aircraft is accelerating. What was also significant in the AF447 case is that the turbulence will cover up any other cues that the aircraft has stalled (stall buffet), and the FBW will mask any change in roll response of the flight controls due to the extreme AOA, as I recall that the roll rate response vs. stick deflection is linear in alternate law. FBW being FBW, it will always try to give you what you are asking of it. So the aircraft will appear to respond normally around the longitudinal axis, and the only thing telling you otherwise will be the compass heading turning in the opposite direction. But trying to figure that one out when you are descending at 10000fpm through a CB at night with a nose-up attitude with your aircraft telling you to pull up even more is an exercise of futility.

With regards to Airbus vs. Boeing: the Airbus overspeed mode was commanding an increase in pitch through the flight directors, which was followed religiously at least until the aircraft reached its apogee at 38000ft. This continuous backpressure on the stick caused the THS to trim all the way up, leading to the deep stall. I doubt they even realised that the THS was at the position it was in at any point as you are not supposed to fiddle with it yourself but let the automatics handle this, even though the captain correctly remarked on his return to the FD that the aircraft was stalled. It has been argued that if they just let go of the controls it would have allowed the aircraft to recover itself, and this is probably correct. This tells you how a Boeing would have fared in the same situation: the lack of autotrim on Boeings leaves the THS in the same position unless you conciously tell it to do something else using the trim switches, and this leaves open your avenue of sensing that the aircraft is stalled as you are unable to maintain a nose-up attitude as the aircraft loses airspeed. It's become pretty clear that in the same situation, a Boeing would not have deep-stalled. Not unless the crew trimmed up by themselves while not looking at the stab trim indicators.