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Continental TurboProp crash inbound for Buffalo

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Continental TurboProp crash inbound for Buffalo

Old 14th Feb 2009, 10:42
  #181 (permalink)  
 
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Wangowango

You are right - the stick shaker will activate 20 knots higher than normal. The aircraft does not necessarily stall.

However, you might get the stick pusher as well, if the speed gets low enough and both stall systems senses a stall (both stich shakers on).

If you fly on autopilot and get a stick push, the autopilot will come off (the autopilot will also disconnect at stick shaker), and the pusher will put the aircraft in a 20-30 degrees nose down attitude, if unarrested. This could catch somebody by surprise.

Cheers

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Old 14th Feb 2009, 11:50
  #182 (permalink)  
 
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The Q400 autopilot is not a great system. It almost always leaves the a/c in an out of trim condition upon disconnecting, with a noticable 'jerk' of the control column, indicating that it does not re-trim the a/c as it should.
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Old 14th Feb 2009, 12:51
  #183 (permalink)  
 
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The switch simply adds a stall margin to the reference speeds,
WingoWango, the switch itself does nothing.
It is only a switch that will stop a light flashing in your face after you select propeller de-icing on.
It is a kind of a reminder that you have switched on the propeller de-icing timer and subsequently have to raise you V1,VR and V2 by 5, 7, and 10 kts. VFTO is raised by 15 kts. (These speeds with the Dash-8 315)
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Old 14th Feb 2009, 12:51
  #184 (permalink)  
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Agreed Grizz...

Though I do not disagree with:
It hits (and sticks) more on one side than the other due to prop slipstreaming. That asymmetry is insidious.
as being a possible circumstance, I would wonder about the degree of the affect when the aircraft is descending with probably a lower power setting.

Quote:
The posted photo of the Q400 tail shows the fairing, which projects forward of the intersection of the H and V stab leading edges, and it is not apparently deiced.

Forgive my ignorance but how can you tell whether it was de-iced or not, given that it had flown all the way from EWR?
Based upon the visible presence of three deicing boots on the stab's leading edges, and the absence of any visible electric pad on the fairing, I am presuming it not to be deiced. This was the case on the C303, which later got a heated pad in the similar area. Perhaps I stand to be corrected...

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Old 14th Feb 2009, 13:08
  #185 (permalink)  
 
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The only parts of a Dash-8 that are protected by inflatable boots are:
  • Wings
  • Horizontal Stabilizer
  • Vertical Stabilizer
  • Engine nacelle intakes

Electrically:
  • Winshields
  • Elevator Horns
  • Propeller blades
  • Plus a bundle of valves pitot tubes static ports atc. etc.

And no the fairing is not de-iced. I wouldn't know also why it is neccesary. It is only an aerodynamic shape to allow the air to move more easily so less drag is created.
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Old 14th Feb 2009, 13:21
  #186 (permalink)  
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Thanks for the clarification D-OCHO...

It is only an aerodynamic shape to allow the air to move more easily so less drag is created.
Similar to a spinner, but not turning, and I've seen lots of ice accumulate on spinners. If a fairing designed to reduce drag is changed in shape, drag is probably increased agian. If drag has been increased, disrupted airflow has occurred. At some extreme, disrupted airflow upsets the way a tail works.

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Old 14th Feb 2009, 13:32
  #187 (permalink)  
 
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The NASA video may have clues to contributary factors of this accident, we will have to wait and see.

Having flown the Q400 for several years at the start of my flying career, I found it interesting that the company I worked for didn't teach us the recovery procedure for a tailplane stall - It being the opposite of a wing stall. I fly jets now, so do turbo-prop operators teach this recovery manouvre in the US? Do ANY Q400 Operators teach this manouvre?

From a flight safety point of view, if it isn't taught to crews, why not? I know this type occurance is rare, and icing conditions may well have to be extremely severe, but the advantages of training far outweigh the outcome of not.
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Old 14th Feb 2009, 13:35
  #188 (permalink)  
 
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For the ice bridging sake!

Ice bridging is not a myth - it really existed in the age of DC-3. That's why modern t-props have boots with multiple chambers that inflate alternately. Ice bridging is not a factor on modern equipment. Do not, i'm saying again: do not listen to old hands who retired before first multiple chamber goodrich was test flown and absolutely do not try to emulate Dakota procedures on Dash or ATR. If it says turn on boots immediately after you start picking up the ice - do so, there's a good reason behind every procedure that you don't understand or appreciate.

And please do not, I'm saying again: do not mention ice bridging in relation to this accident.

Originally Posted by Pilot DAR
At some extreme, disrupted airflow upsets the way a tail works
You're talking C303 here aren't you?

Originally Posted by CAT1 REVERSION
but do turbo-prop operators teach this recovery manouevre?
I was taught it before first putting my nether region into RH seat of ATR. Never did it in sim - at the time, tailplane stall was not supported by sim software.
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Old 14th Feb 2009, 13:38
  #189 (permalink)  
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You're talking C303 here aren't you?
I know that I'm talking about a C303, I wonder if I'm also talking about a Dash 8, though I give great credit to certification testing...

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Old 14th Feb 2009, 14:26
  #190 (permalink)  
 
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Hi D-OCHO

You are a little bit wrong about the "increase ref" switch.

The increase ref switch will increase the stall floor by 20 knots. The stick shaker will come on at a higher speed, regardless that the aircraft is far from an aerodynamical stall.

In my company, we had some incidents, where pilots had the increase ref switch on during descend, but bugged normal speeds because of non icing conditions on the ground. They then forgot to select increase ref off and encountered stick shaker on approach.

Selecting increase ref on will change the colour of the ice detection caution on the engine display from yellow to white.

Regarding prop de ice, selecting this on will increase the minimum oil pressure on the ED from 55 degrees to 65 degrees. The yellow band will extend a bit.

Cheers

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Old 14th Feb 2009, 14:37
  #191 (permalink)  
 
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'Sqwak7700' wrote in Post #175:

"That is why wipers, window frames, temp probes are all good indicators, and that is why really really large planes like the C5 galaxy don't have wing anti-ice."

I find that very hard to believe. I would classify the 747 and A380 as "really, really" large planes and their wings are protected. What is Lockheeds secret with the C5 ?!
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Old 14th Feb 2009, 14:59
  #192 (permalink)  
 
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elevator trim question

Re. switching off A/P to get "the feel". Have any of you turbo prop guys ever tried taking a note of the elevator trim position when you enter icing? I flew (and occasionally still fly) jets, and icing in the hold, while a major concern, never developed beyond just that...a concern. I would note the elevator trim when we entered the hold and of course it moved (SLF and F/As etc) But never significantly. I wonder if in your world, where empenage icing is now apparently of great concern, if unusual forward elevator trim could be a precursor of doom? And if so would this be an idea for an SOP? Please be gentle with your flames!
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Old 14th Feb 2009, 15:15
  #193 (permalink)  
 
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Having flown the DC 3, later F 50 and ATP, I can say that until you experience very very severe icing its easy to speculate. The bird wants to fly but there comes a moment when excess weight and induced drag overcomes all possible margins built in by engineers.
Then you become a test pilot in no mans land with no recourse but to get the hell out, which usually is too late, before the aircraft literally gives up any notion of known aerodynamics.
Then its just a question of boring a hole in the ground....ref: ATR in Illinois: I was in the area on my way to Ypsilanti, MI....the hole left appears just like the one in Buffalo....
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Old 14th Feb 2009, 15:32
  #194 (permalink)  
 
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Even if the icing was severe, there is something missing in the puzzle. Dash's operate in pretty bad conditions around the world and I find it hard to guess that this one just build up ice and tailplane stalled into a house...
Of course you are correct in questioning this further.

We do need to evaluate all the possible holes that may have lined up.

There is a always possibility of a system failure and even a possibility that the pilot response/training for this operator did not accomodate this level of buildup.

and there is the possibility that it wasn't tailplane ice.

I'm keen to keep reading the NTSB releases, They are quite interested in preventing the next icing accident (this year, this month) and I'm sure that they will be working this issue.
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Old 14th Feb 2009, 15:41
  #195 (permalink)  
 
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Anybody have copies of the sigmets/notams/pireps during this time period?
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Old 14th Feb 2009, 15:47
  #196 (permalink)  
 
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There is a lot of talk about tailplane stall recovery going on, I have never received training on this. Ok so I understand recovery is to pull not push but how does one recognise a tail stall in the first place? maybe a sudden uncommanded pitch down ?
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Old 14th Feb 2009, 15:50
  #197 (permalink)  

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That Nasa video is a real eye-opener. One of the best presentations I have ever seen.
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Old 14th Feb 2009, 15:53
  #198 (permalink)  
 
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It would be nice if everyone on this thread would watch the icing video in the link earlier on in this thread, then we wouldn't have so many questions that have already been answered!
The nasa video is very good, check it out!
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Old 14th Feb 2009, 15:53
  #199 (permalink)  
 
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Squealing Pig
Suggest yoou read my ealier post or much better stilll take the time to watch the NASA video that someone here has posted a link to. Should be compulsory viewing for any pilot.
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Old 14th Feb 2009, 16:05
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Thanks for replys, going to watch it, must have missed the post didnt know it was there
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