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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 1st Jan 2015, 23:50
  #881 (permalink)  
 
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Skycatcher pilot

I just watched a tv special on AF 447.

In my plane I have a Garmin 696 that will display GPS derived flight instruments. Ground speed, Altitude, Vertical speed, Heading, and Turn.
I have it in case my no backup instruments (G 300) fail. It seems such data might have have helped with the confusion created when the pitot tubes iced.

Is such data available in an airbus?
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Old 2nd Jan 2015, 00:23
  #882 (permalink)  
 
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Hi Qantas_A380,

I think what happens is this: The ice buildup rates temporarily exceed the capability of the anti-icing pitot heater. The entrance to the pitot tube is blocked, but the pitot probe drain hole remains open. The sensed Pt drops quickly towards static pressure (Ps). The IAS drops quickly towards stall speed (or stick shaker if one is present), hence the stall warning. The IAS remains affected, usually for a short period, until the heater catches up once again and the blockage is cleared.

I don't know exactly why nose up occurs in some situations, each one may be different depending on what the crew observes and decides to do. For instance, if the crew decides they need more power to overcome a perceived stall, they may apply TOGA thrust which will cause a pitch-up in aircraft where the engines are mounted under the wings. Anyhow, I hope this explanation helps…
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Old 2nd Jan 2015, 02:39
  #883 (permalink)  
 
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Stall Warning

I was of the understanding that Stall Warning is based on AOA rather than IAS?
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Old 2nd Jan 2015, 09:36
  #884 (permalink)  
 
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@Q_A380

True but there is MACH involved to set the AoA SW limits.
Now a lower MACH will increase the AoA SW limit but it's the suddenly returning MACH (some overshoot)
which will trigger a complete "STALL STALL" or incomplete "STALL ST" SW.
Whether it was a false (UNDUE) or actual STALL WARNING (Hi AOA) is not mentioned in the table.
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Old 2nd Jan 2015, 13:31
  #885 (permalink)  
 
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As stated previously, the stall warning system shuts down below a certain IAS... cannot recall exactly, but 80kts or so. So one factor which I believe contributed to the confusion in that cockpit was that when they made the moves to reduce AoA and increase airspeed, the stall warnings would activate as the plane accelerated past 80kts (or whatever the stall system cutoff is). They then reasoned that whatever they had just done put them into a stall, and reversed their control inputs to make the situation worse.

Early to speculate, but let's keep our eye on this stall warning inactivation/activation speed as a potential factor in Air Asia.
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Old 2nd Jan 2015, 22:22
  #886 (permalink)  
 
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Originally Posted by RobertS975
As stated previously, the stall warning system shuts down below a certain IAS... cannot recall exactly, but 80kts or so.
The AoA vanes are only certified to produce valid information above 60kts IAS. As I said earlier:
Originally Posted by DozyWannabe
No Computed Data - i.e. the value is invalid and cannot be used for further processing.

That was a secondary consequence (or "side effect" in engineering-speak) of the systems design as a whole. The SW ceased because it was no longer receiving valid data from upstream - there was no design intent to "shut off" the SW directly.
...
We've been over this many times in earlier threads, and the fact is that if you latch stall warning for one scenario, it runs the risk of giving false information in several other scenarios. It's a very difficult system to make completely failsafe across the board - and as I repeated above, the silence from other airframers does tend to suggest that their systems would have behaved in a similar manner.
...They then reasoned that whatever they had just done put them into a stall, and reversed their control inputs to make the situation worse.
I also stated in that post that a bit of thought on that point should have indicated a problem with the SW system rather than the ND input causing a stall, because lowering the nose reduces AoA, and basic aerodynamic knowledge (which pilots should have) of the facts states that it is effectively impossible to go from an unstalled state to a stalled state by reducing AoA.

Put in more basic terms, there is no way that lowering the nose (and reducing AoA) should stall the aircraft. It may have added to the confusion, but I'd be surprised if they thought they'd put the aircraft in a stall by commanding Nose-Down.

If we're going to speculate on the AirAsia front, I reckon this thread should go a bit quieter now...
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Old 4th Jan 2015, 15:49
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Details here for this AD 2014-0267-E and 2014-0266-E
Airplane Flight Manual – Undue Activation of Alpha Protection – Emergency Procedure
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Old 10th Jan 2015, 20:16
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Gliders Might Improve Pilots Upset flying skills-Maybe not

Having flown gliders, fast jets, (and the boxes they came in ) I believe I'm able to comment.
Personally, I don't think glider flying would help that much. Bonin, for example was alleged to be a glider pilot, but when the chips were down, he became another Whac-A-Mole pilot, responding to roll deviations with great speed but ignoring pitch deviations and losing the big picture.

The best training I have encountered for aircraft handling at the edge of the envelope is ACM (Air Combat Maneuvering against another aircraft of similar performance). To do good ACM requires an AOA gage of some sort. Unfortunately the required equipment is not available to most pilots who could benefit from that type of training.

By comparison, thermaling competitively against another glider in the same thermal is a pale imitation.

Maybe what pilots need is solid skill at flying the aircraft manually so that when Hal no longer computes, you can take over successfully and avoid having to demonstrate superior maneuvering skills.
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Old 10th Jan 2015, 20:35
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Indeed, Machinbird

If glider is certainly a good step in early pilot curriculum, I do not see his benefit for kind of recurrent training (same idea for light aircraft recurrent training)

How a glider, a Cessna, whatsoever, could be helpful to restitute pilot feeling when this pilot will probably fly an aircraft with autotrim, without real effort restitution on joystick, without moving thrust levers and different flight controls laws...

Illusion..
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Old 10th Jan 2015, 23:39
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Cedric Bonin, the PF on AF 447, was a qualified glider pilot.
So the flying experience gained in gliders does not automatically translate into superior airmanship when facing turbulence at night with unreliable instruments.
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Old 11th Jan 2015, 19:24
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A/P was not responsible for lowering the nose, either to increase airspeed or otherwise.
Winnerhofer, are you planning on recreating the AF447 discussions?
Every aspect of this accident was dissected in fine detail in the voluminous threads on the subject. Just read through them and understand them, painful though that may be.

For myself, I'm always willing to listen to new evidence, but a rehash just turns my stomach.
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Old 12th Jan 2015, 10:02
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Concur .. if a need to look back is considered necessary, please just link to the old post of note and add any new data/thoughts.
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Old 12th Jan 2015, 19:32
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Hi,

VNAV PATH
How a glider, a Cessna, whatsoever, could be helpful to restitute pilot feeling when this pilot will probably fly an aircraft with autotrim, without real effort restitution on joystick, without moving thrust levers and different flight controls laws...
It's like learn and train in this .....



For drive this ....

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Old 13th Jan 2015, 03:21
  #894 (permalink)  
 
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"Qualified Glider Pilot"

Unfortunately, we don't know much, if anything, about his glider qualifications. We don't know if he took a weekend glider transition course or had 1000 hours.

As a glider pilot myself (and A330 Capt), I was surprised when I first learned that Bonin was a glider pilot yet failed to push the nose down in reaction to a stall warning that persisted for over 50 seconds! Obviously, in the glider, there is no other recovery available. We fly on the edge of a stall routinely, recognizing the impending stall condition by feel - as there is no audible warning system.

I remain a strong advocate of hand flying aircraft such as gliders to counteract a case of flight director addiction ( which I will go out on a limb and accuse Bonin and Robert of having).

In 1986 we could assume that anybody that showed up in an airline course already had thousands of hours of round-dial instrument flying. Checking out in an advanced aircraft (757 at the time) was a matter of teaching the automation. Now, the assumption of those skills is a poor bet. Throwing a guy out of flight school into the right seat of an A320, then A330/340 and rarely if ever practicing those FD off skills is like asking an adult to perform the piano song he learned as a child - on stage, under pressure, with no notice.

Yeah, I DO think my glider time has helped me keep some skills. But only because I put some effort into it. I try to think about the aerodynamics, the micro-meteorology, and such things because they are key to success in a glider.

It's easy to sit back, do whatever the FD says (it's never been wrong yet...), punch on the AP, and type my way to the destination. That does take knowledge and skill, but its a different knowledge and skill than hand flying the machine with out any automation, in alternate law, at altitude, in a storm at night. The later requires some practice. Practice few long haul guys get much of.
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Old 13th Jan 2015, 15:13
  #895 (permalink)  
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Capt. Palmer;

Even as late as the A320/A330/A340 Airbus types, I still recall the value of "looking through" the FDs to the real picture / situation behind.

If I recall correctly, the Japan Airlines DC8-62 accident, (report) resulted from the captain not understanding the FD and followed it taking the aircraft below the glide slope.

Those of us now retired or about to retire may still recall the elementary FDs of Douglas and Boeing aircraft, (the L1011s was a bit more sophisticated at the time) and quietly developed the habit of looking through the directors to the actual information on the HSI, (for others, Horizontal Situation Indicator).

The value of this subtle, psychological "work-around", (evolving as it did through lack of sophistication of the FDs at the time, and a mistrust and a lack of training/knowledge of the FD) remained a useful (and for situations like AF447, and indispensible) "tool" as it was always the "sober second opinion" when more sophisticated FDs such as the Airbus' FDs were incorporated with the autoflight system.

Not saying ignore the FDs...just bear in mind what's actually going on "behind" them - one is for real, the other tells you what the autoflight is going to do, not necessarily what it's doing!

When it came time for manually flying a raw-data, (no FDs) ILS approach, the view of the actual aircraft situation without the FDs and other symbols was "normal"... even as the standards people might frown on such methods.

The simulator can, and today should, be used for such basic skills training and examination.

Try the following exercise next time there are a few moments spare time, (rare, I know) in the sim:

Establish level flight at 10,000ft, 250kts. With no FDs, no heading bugs and no autopilot or autothrust, begin a coordinated climb to 15,000ft while turning 90deg to the left and when reaching that heading, turning back to the original heading, all at 250kts, capturing the target altitude smoothly, (ie, most "passengers", (this IS the sim!), would not know you've leveled off. Then immediately begin a descent to return to 10,000ft, maintaining 250kts, while turning to the right 90deg and then when reaching that heading, turning back to the original heading, leveling off at 10,000ft. Remember, no autothrust! - you've got to know the power settings, attitudes, control-column/stick pressures to do it all well and your scan has to be near-flawless, whether steam or glass.

Variations while doing these climbing/descending S-turns would be to start the exercise at 10,000ft with the first or second flap selection made, then begin the climbing S turn while cleaning up, accel to 250kts, level off, then reverse the process ending up at the flap selection/speed one began with.

These weren't standard in the sim but they weren't rare either. They test one's abilities far better than the standard V1 cuts and should be in the syllabus for every sim session, (takes about a half hour of time).

Enjoying your book...many thanks for writing it.
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Old 13th Jan 2015, 15:48
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PJ2
For a long time now Airbus has introduced Entrée level training for non jet experienced pilots. The type rating starts with 8 sessions of Flight and Navigation Procedure Training out of which first four sessions consists of raw data flying without any automation whatsoever including climbing and descending S turns as you mentioned. It goes on to execute departures, arrivals and ILS approaches with introductions to some abnormal conditions with aim to develop control and multi crew cooperation. This is to be conducted in a flight training device may be in SIM without motion. Procedures are taught at later stage. However to save cost airlines opt for a shorter course which is mostly conducted in a procedure trainer instead of FTD. That requires trainees who have better hand eye coordination than average.
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Old 13th Jan 2015, 19:49
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Try the following exercise next time there are a few moments spare time

We used this as the standard endorsement introduction on the 737 albeit with an accel/decel requirement to push the scan rate. Once the student demonstrated competence on this basic exercise, we threw in a few more demanding exercises for polish.

Gentle encouragement and patter (where useful) saw rapid progress for the great majority of pilots. Conversely, the exercises even more rapidly identified the few who were way out of their depth.

Likewise, throughout the endorsement, we took advantage of 5 minute vignettes here and there to run the close in part of a raw data, hand flown ILS to progressively decreasing minima .. worked a treat with most achieving a good 0/0 landing by the end of the endorsement program ... great confidence builder.
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Old 13th Jan 2015, 21:14
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...great confidence builder.

Indeed it is, John, interesting to know you've seen it in action too. I agree completely with the approach taken...gentle encouragement and patter.

I think there is far less to the differences between small, single/no engine types and large transports than may be generally assumed. Most can quickly learn the need for staying ahead of the aircraft , whether it is a half-mile or six miles - the learning of the "art" comes together in all-of-a-sudden ways by plateaus so to speak, doesn't it?

In fact I will go out on a limb and say that this approach can make a 250hr pilot an able and keen learner who goes on to become a very competent aviator.

I don't think there's more to the automation "problem" than the re-introduction of such basic manoeuvres. Automation is then relegated to serving the pilot, and when it goes pear-shaped taking over becomes a non-event.

And, it would accomplish that second purpose as well - identifying those who were (currently) way out of their depth so that they could either benefit from further training or help identify that subtle place that may say, "this isn't for me".
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Old 13th Jan 2015, 22:32
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I will go out on a limb and say that this approach can make a 250hr pilot an able and keen learner who goes on to become a very competent aviator.

Indeed.

Having trained numerous cadet pilots in that experience bracket I have seen it work well .. a lack of depth, naturally enough, which comes with subsequent line exposure ..

One of my favourite students from quite a few years ago was a young Chinese cadet pilot with Xiamen .. keen as mustard, a very quick learner, and good stick and rudder technique. Last I heard he was a left seater in a widebody and doing quite nicely in his career.
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Old 14th Jan 2015, 21:28
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Originally Posted by Bpalmer
Unfortunately, we don't know much, if anything, about his glider qualifications. We don't know if he took a weekend glider transition course or had 1000 hours.
The AF447 final report notes that he qualified as a glider pilot in 2001. Alas, I can no longer find the specific details, but I do recall there was once an article online which enumerated F/O Bonin's gliding experience and qualifications. Based on what I remember (caveat emptor, as usual), he had dedicated significant time and effort to the practice with a couple of advanced qualifications to his name. I don't know how that translates to specific hours logged, but the implication was that he'd had significant time and was very competent at one stage.
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