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Continental TurboProp crash inbound for Buffalo

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Continental TurboProp crash inbound for Buffalo

Old 27th Mar 2009, 20:37
  #941 (permalink)  
 
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chuks - friends on the 777 say they have AOA displayed.
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Old 27th Mar 2009, 21:09
  #942 (permalink)  
 
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flipster

published reports say that bombardier states that the Q400 is not susceptible to tailplane stalls. that is all I have. if the pilots were told that prior to the crash, their mindset might not predsipose them to tailplane stall recovery procedures.

I"VE seen many pilots, in turbulence, hall back on the yoke to reestablish the sense of positive G. Just wondering if the g loading went negative for a second.

AS to angle of attack indicators...I would like to have one. My favorite plane had a fast slow needle opposite the glide slope and ir really helped during an approach.

BUT, maintaining an AOA indicator might be tough in the real world and the FAA didn't want people to have to mess with the mx.

Wilbur and Orville tied a piece of yarn to the flyer and got AOA info.
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Old 27th Mar 2009, 22:16
  #943 (permalink)  
 
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The Dornier 328 fed AoA to the stall redline on the ASI tape in real time. You could watch the redline bob up and down in response to gusts. Direct display of AoA was there none on that type.
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Old 27th Mar 2009, 22:42
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PTH

Any chance of further info on those reports - it is not something I've heard. Having said that, I've not seen anything to the contrary either! If you have a link to the Bombardier stuff I'd be most grateful. They must be slightly worried about this happening in the Q400 as our manual says that, in severe icing, we should disconnect the AP - I've taken this to mean "watch out for tail-plane icing and the controls (in pitch) going a bit wonky" - however, I don't think there is any guidance about what to do if said controls do "go wonky", let alone if there there is a pitch down/tail stall nor what to do if the stall warner/pusher then kicks in!

I agree that it is important to find out if there is any such advice (or not) and if there is, did the Colgan pilots have the up-to-date info. As I say, any official advice would be greatfully rec'd.

Flipster
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Old 27th Mar 2009, 22:44
  #945 (permalink)  
 
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Hopefully this accident will show how important it is to monitor attitude in stall recovery. It doesn't matter much what caused the upset but maintaining the right attitude is what will recover the aircraft safely. Wing stall or tailplane stall requires holding the attitude to recover. Full up trim with a wing stall requires agressive forward yoke to not let the plane pitch up with aggresive power increases. If it is a tailplane stall holding attitude will require back pressure and reducing flaps. The A320 off France had severe pitch changes causing the crash of the Air New Zealand airplane probably because of a lot of nose up trim followed by max power. Neither of these accident may have occured if hand flown. The autopilot is wonderful but it can leave the pilot not entirely in the loop.
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Old 27th Mar 2009, 23:41
  #946 (permalink)  
 
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flipster and bubbers 44

flipster...I learned about the no tailplane stall from bombardier by reading the whole thread ...start at the number one post....it is eye opening. I wouldn't make it up.

bubbers44...attitude! I agree with you and while in cruise flight I always set my flight director ( in my primitive douglas jet) to an attitude that would be safe for virtually any problem...sort of as a cursor to go for if things went to hell.

so, while in cruise on autopilot ( a relativey simple one), I would have a recovery attitude target already set in case things went to hell in a handbasket.

I learned to fly near some significant mountain ranges and learned early on that any plane could LOSE a battle with mountain wave. Level wings and a modest nose up attitude would be safe even if losing altitude due to wave or other problems. (see riding the waves in the AIM...but I know you already know bubbers)
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Old 27th Mar 2009, 23:44
  #947 (permalink)  
 
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The Dornier 328 fed AoA to the stall redline on the ASI tape in real time. You could watch the redline bob up and down in response to gusts. Direct display of AoA was there none on that type.
Ditto the Q400.

I used to fly early A320 (s/n in mid-200s) with analogue electro-mechanical AoA indicators set outboard of PFDs but the only thing they provided was some poor inflight entertainment. Also there's major difference between fast/slow indicators that are indexed to selected speed and AoA index lights (green doughnut, red and yellow Vs), found on some military aeroplanes.

Bombardier's AOM regarding latest NTSB findings has somehow found its way to my mailbox, but there was nothing in it that wasn't already posted on the PPRuNe.

If you really want to know what exactly happened and why, please come back in a year or two, when the final report is published. By the time final report is out, most of the PPRuNers discussing the accident tend to be knowledgable professionals.

Regarding the Perpignan, prelim report is out. Please anyone wishing to refer to the said accident, do acquaint yourself with it. It might spare us the incorrect notions similar to:"it wouldn't have happened if it was hand flown".
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Old 28th Mar 2009, 00:33
  #948 (permalink)  
 
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By hand flying you are monitoring and feeling all changes to the airplane. When the autopilot disconects you are not. The autopilot is great for reducing workload but must be monitored closely. Letting airspeed get too low started this event in the first place because the crew let it happen. Then the pitch up maneuver caused the crash.
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Old 28th Mar 2009, 02:21
  #949 (permalink)  
 
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I used to fly early A320 (s/n in mid-200s) with analogue electro-mechanical AoA indicators set outboard of PFDs but the only thing they provided was some poor inflight entertainment.
AoA indicators provide almost no usable info at cruise airspeeds. The AoA/airspeed curve shows a very small AoA change for a given change of airspeed at cruise. On the other hand, AoA at approach speeds provides a very precise indication of where you are on the lift curve.

BTW, my comment on AoA earlier was just an aside. My real point was the crew in this accident weren't watching their airspeed. However, AoA is the premier way to avoid a stall. Stall recovery using an AoA readout gives you the simplest means of getting to L/D max.
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Old 28th Mar 2009, 05:20
  #950 (permalink)  
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Hornet...

Ref your post regarding your favorite A/C and the AOA (i.e.-"Fast/Slow Indicator)...

It must have been a Boeing as in 727 or 737...Steam gauge style....and BTW, I loved the little circle on the right of the AI...

Fly the airplane...don't let it fly you...
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Old 28th Mar 2009, 08:06
  #951 (permalink)  
 
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downin3green

downin3green

nope...a dc9...but probably the same flight director/attitude gyro.

I can't help but wonder if the Q400 and the Turkish 737 that crashed in Amsterdam had steam gauges if the crash would have been avoided.

I like looking at a big airspeed indicator...it is important as I am sure you know.
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Old 28th Mar 2009, 09:15
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Exactly.

And a couple of points..

Why are there multiple references in this thread to the autopilot trimming to "full nose up", and then when it disconnected the aircraft pitching up radically (uncommanded) as a result.....? (This is all prior to any possible application of power and acceleration). This makes no sense.

The trim may well have been full nose up, but there is no way the autopilot will trim the aircraft to an out-of-trim position. I think a lot of people here are getting confused.

In cases where there is aircraft/flight control (yoke) reaction that occurs at AP disconnect, it is because the AP either cannot trim at the rate required, or cannot provide the amount of trim needed. ie: it is trying to trim but can't... through no fault of it's own.

And one more question....has anyone here, or anyone they know, ever experienced a tail stall (in a modern aircraft, within the past 15 years).....I seriously doubt it.

The NASA tail icing/stall research was very enlightening, and definitely required viewing for all turboprop pilots (and maybe all pilots), but I truly feel that there has been an over-emphasis in the airline training world on this phenomenon, at least in the US.
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Old 28th Mar 2009, 12:59
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And one more question....has anyone here, or anyone they know, ever experienced a tail stall (in a modern aircraft, within the past 15 years).....
I understand they are no longer here to tell the story...
(except for one I believe)
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Old 28th Mar 2009, 13:37
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When the first DC9 Super 80's came out we bought a few for our airline. One of our crews forgot to push the tail deice button before one approach in icing conditions and with full flap extention the nose pitched down. They brought the flaps back up to recover. Ice obviously was the cause but did the horizontal stabilizer actually stall or became inefficient?
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Old 28th Mar 2009, 13:48
  #955 (permalink)  
 
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Why are there multiple references in this thread to the autopilot trimming to "full nose up", and then when it disconnected the aircraft pitching up radically (uncommanded) as a result.....? (This is all prior to any possible application of power and acceleration). This makes no sense.
I don't think anyone who has read the entire thread is saying that the pitch-up could have happened before the application of power. I've tried to explain this many times now, but people don't seem to get the reasoning. So I will try one more time.

- As the speed decays, the autopilot trims nose-up to maintain altitude.
- Eventually the speed decays to the point where the stick-shaker activates.
- The autopilot automatically disengages when the stick-shaker activates leaving the plane in lot's of nose-up trim.
- This alone would not cause the plane to pitch up...in fact, further speed decay would cause it to pitch down....

However!!! A very likely scenario is that one or both pilots realized the low-speed situation at or just before stick-shaker activation and applied FIREWALL thrust as an instinctive stall recovery. With LOTS of power coming on rapidly (and the autopilot off), the aircraft would want to pitch up rapidly to maintain it's trimmed airspeed. If the pilots did not actively push against the pitch up then the plane would soon be in a very unusual attitude and eventually the stick-pusher would activate just before the stall.

Let me know if any of this scenario doesn't make sense and I will try to dig up old posts that might explain it better.
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Old 28th Mar 2009, 15:51
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Makes sense except for the fact that while lots of power coming on quickly with a simultaneous A/P disconnect would result in a nose up pitch attitude because of the trim situation, it wouldn't exert a 25lb pull on the stick.
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Old 28th Mar 2009, 16:35
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Also it would be rather daft of the NTSB not to mention it, if the pitch-up would have occurred at the same time as any power increase.
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Old 28th Mar 2009, 18:24
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I guess we are all saying the same thing here, but my point really was....it has nothing to do with the AP. The aircraft would be in the same trimmed condition as it would be if one were hand flying prior to the stick shaker/stick pusher sequence. (assuming that most of us don't fly around out-of-trim)

Of course had they been hand flying, then the onset of the airspeed loss would probably have been recognized, and we wouldn't be here discussing any of this.
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Old 28th Mar 2009, 19:58
  #959 (permalink)  
 
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Watch That Autopilot

Of course had they been hand flying, then the onset of the airspeed loss would probably have been recognized, and we wouldn't be here discussing any of this.
...or simply monitoring closely what the autopilot was doing...
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Old 28th Mar 2009, 20:38
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In the 737's case it's the lack of an adequate deceleratory alerting system
I think you'll find that's what we call the ASI.

I like looking at a big airspeed indicator...it is important as I am sure you know.
Absolutely right - and it works really well with along with that Altimeter thingy when you're landing.
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