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Author Topic: Now that the BUF thread has been locked...  (Read 19015 times)
joeyb747
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« Reply #30 on: February 22, 2009, 09:41:57 AM »

I didn't think the -8 had autothrottle. Most turbo prop aircraft do not. So that makes sense to me then. The airplane was on autopilot, with "approach" selected. The glideslope deviated, the airplane tried to go to it. The pilots never added power as the airplane pitched up 31 degreees and lost airspeed, and stalled the wings. Before the pilots realized what was happening, it was too late.
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joeyb747
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« Reply #31 on: February 22, 2009, 09:46:11 AM »

But it was the wrong side...

"The problem comes when joining from the right (or west) side when the plane captures the G/S prior to the LOC. Colgan was joining from the left side and like many planes,..."

This is bizzar. All the right symptoms, wrong side...very strange.
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iskyfly
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« Reply #32 on: February 22, 2009, 11:56:02 AM »

I didn't think the -8 had autothrottle. Most turbo prop aircraft do not. So that makes sense to me then. The airplane was on autopilot, with "approach" selected. The glideslope deviated, the airplane tried to go to it. The pilots never added power as the airplane pitched up 31 degreees and lost airspeed, and stalled the wings. Before the pilots realized what was happening, it was too late.
Well, you forgot this part;
Quote
Colgan was joining from the left side and like many planes, the automation is such that the G/S cannot be captured prior to the LOC being captured.


I don't think pursuing this "lead" will yield results.

It is time to wait for more facts.
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mhawke
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« Reply #33 on: February 22, 2009, 12:32:15 PM »

The glideslope deviated, the airplane tried to go to it. The pilots never added power as the airplane pitched up 31 degreees and lost airspeed, and stalled the wings. Before the pilots realized what was happening, it was too late.

Only problem with this theroy is that according to the NTSB, the autopilot was off and the 31 degree up was pilot commanded.  He overrode the stick pusher for some reason and pulled back when the stall warning came on.  That ws before the up angle.
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badger634
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« Reply #34 on: February 22, 2009, 01:20:06 PM »

From what I understand, the captain had recently been flying Saab340's, which have the potential for tail stalls.  In a tail stall, you need to pull UP (among other things).

Dash 8's are not susceptible to a tail stall, but this pilot might have been relying on his Saab 340 days.  Instead, the stick shaker just indicated a run-of-the-mill wing stall, and his action of pulling up doomed the plane.

Does that seem reasonable?
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cessna157
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« Reply #35 on: February 22, 2009, 01:44:38 PM »

You are correct in suspecting this is not the case.  When in approach mode, the autopilot follows the glideslope as a secondary case.  Pitch has greater control over the autopilot (it is more complicated than that, but let's just go with this as the baseline).  If the glideslope goes full scale deflection high, the autopilot will pitch the aircraft up to correct only to a certain point.  To use an extreme example:  If the glideslope remains at full up, the autopilot will not perform a loop trying to get to it.

It is part of training that in an extreme ice encounter, the autopilot may hide what is truely going on with the aircraft.  That is true to a certain extent.  Along with a strong elevator force, there will also be a lot of trim indicated.  So that will be the first hint that something is awry. 

Also, another level of protection is a caution of such a condition.  I'm not sure exactly what the Q400 has for an avionics/autopilot suite, but the CRJ has a Collins package.  Something that we'd see on the older (let's use the phrase "well broken in" if you catch the hint) planes is, upon rotation at takeoff, the aircraft immediately wants to roll.  This is considered normal (1 wing is twisted, normal wear/tear) and can be easily fixed with aileron trim.  If this rolling tendency is not trimmed out (let's say the aircraft wants to roll right, so constant left input is required) and the autopilot is engaged, it will fly the aircraft just fine.  But if the autopilot tries to make a left turn, it feels that it is using a larger than normal force so it will generate a Master Caution, the pilots hear "Ding", and in this case we'd get a yellow caution message that says "AP trim is LWD".  This means the autopilot has sensed an out of trim position, and it is holding the left wing down.

The point I am making is in today's aircraft, there are protections to out of trim conditions by the autopilot.  This is not to say that they are absolutely perfect (the CRJ autopilot likes to hold up elevator for some reason at slower airspeeds instead of trimming it out, so a technique pilots use to disengage the autopilot is not to use the disengage button, but to use the up trim button).
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joeyb747
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« Reply #36 on: February 22, 2009, 02:36:26 PM »

OK...I was not sure if the autopilot was engaged or not. I hadn't heard for sure...I know Colgans Company Policy is for the pilot to fly the airplane in icing conditions...that dosn't mean they always do. So it sounds more like pilot error then pretty much anything else.

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iskyfly
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« Reply #37 on: February 22, 2009, 03:30:38 PM »

OK...I was not sure if the autopilot was engaged or not. I hadn't heard for sure...I know Colgans Company Policy is for the pilot to fly the airplane in icing conditions...that dosn't mean they always do. So it sounds more like pilot error then pretty much anything else.


Dont confuse an autopilot in alt / hdg hold mode with an autopilot capturing and flying the G/S and loc. They very well could of had the autopilot on, holding altitude / heading.
 
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joeyb747
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« Reply #38 on: February 23, 2009, 07:35:30 PM »




[/quote]
Dont confuse an autopilot in alt / hdg hold mode with an autopilot capturing and flying the G/S and loc. They very well could of had the autopilot on, holding altitude / heading.
 
[/quote]

It's all technically "autopilot" if you will. HDG and ALT mode would be engaged with APPR selected. Once the airplane begins to capture the LOC and GLD the HDG and ALT holds will automatically turn off, and join the airplane on the glideslope/localizer.

But Colgan should have been all hand flying per company policy. They were in known icing conditions.
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cessna157
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« Reply #39 on: February 23, 2009, 08:07:10 PM »


But Colgan should have been all hand flying per company policy. They were in known icing conditions.

Yeah yeah, and when you're driving you should never exceed the speed limit and always keep your hands at 10 and 2.   grin
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KSYR-pjr
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« Reply #40 on: February 23, 2009, 08:38:07 PM »

But Colgan should have been all hand flying per company policy. They were in known icing conditions.

Do you know their policy first-hand or are you just restating what the media is reporting?   Are you certain that this hand-flying policy covers all levels of icing, including light and moderate?
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joeyb747
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« Reply #41 on: February 23, 2009, 10:42:26 PM »

KSYR-prj: To answer your question:
Most airlines do require pilots to hand fly in icing. No I dont know their policy first hand. But i do know when i was a dispatcher with Zantop, that WAS a requirement. Hand fly the airplane in icing conditions. PERIOD. And further more, an friend of mine who is a Captain with Northwest on the A330 agrees with me. Hand flying in icing is a requirement.
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joeyb747
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« Reply #42 on: February 23, 2009, 10:55:50 PM »

Let me re-phrase that-It is required to hand fly the airplane on approach only in icing conditions. On climb-out, you can engage the autopilot when the aircraft is stable.   
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KSYR-pjr
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« Reply #43 on: February 23, 2009, 11:45:27 PM »

KSYR-prj: To answer your question:
Most airlines do require pilots to hand fly in icing. No I dont know their policy first hand. But i do know when i was a dispatcher with Zantop, that WAS a requirement. Hand fly the airplane in icing conditions. PERIOD.

Even ILS CAT III C?  Hmmm.

edit:  I still question this "policy" with regards to the level of icing it references.  Cessna, did your company specify a level of icing where the AP must be disengaged on approach or was it any ice *period*?
« Last Edit: February 23, 2009, 11:57:59 PM by KSYR-pjr » Logged

Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
joeyb747
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« Reply #44 on: February 24, 2009, 06:53:49 AM »

I will have to check on the CAT III requirement. Thats a good point.  smiley

Correct me if I'm wrong but I dont think KBUF has CAT III, does it? I think It's just simple ILS. 5/23 have ILS on each end, and 14/32 does not.
 

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