Another one down
- Thread starter A.J.
- Start date
A.J.
I am very familiar with the crash site, it is about 1000 feet from my former business and less than 200 feet from our local fire department. Witnesses say it "sputtered" and "fell from the sky".
It was a DeHavillind less than one year old. Everyone around here will be doing the "six degrees" thing once the list is released....this is not a huge metro area and everybody knows everybody/is related, etc.
A real tradgedy.
I am very familiar with the crash site, it is about 1000 feet from my former business and less than 200 feet from our local fire department. Witnesses say it "sputtered" and "fell from the sky".
It was a DeHavillind less than one year old. Everyone around here will be doing the "six degrees" thing once the list is released....this is not a huge metro area and everybody knows everybody/is related, etc.
A real tradgedy.
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icing perhaps...looking at the conditions.
Paul Thompson 'Hooligan'
Admin
Can someone explain icing properly - I've seen them de-ice wings on the ground etc and I know some aircraft have de-ice circuits.
Does the icing affect the instruments? - eg pitot tubes? add weight? affect control surfaces? affect aerodynamics? would be interesting to hear a proper explanation from a forum pilot as opposed to some half-wit on Sky Tv who claims to know what he's talking about...
Pete McCluskey.
Lifetime Supporter
Everything you need to know Paul is here. http://www.caa.govt.nz/safety_info/GAPs/Aircraft_Icing_Handbook.pdf
Looks like another one in Heathrow? Crash landing? Anyone have details?
Paul, re. icing, you hit them all, as in all of the above. Todays news casts did refer to the pilots complaining about icing. Instrument icing has happened, moreso in the past when "pitot heat" wasn't as reliable (our annual recurrent training in the B727 simulator usually had at least one event where the airspeed would very subtly go bad and the check pilot would see if he could 'trick' you into not noticing by dong something distracting, the old pitot heat circuit breaker trick
) ).
Icing is always bad news, and everybody tries to avoid it. Modern jets can 'tolerate' up to moderate icing for a short period, but nothing is designed to operate continuously in icing conditions. Note that it's not just instruments but the engines as well that can be affected, as the engine controllers have their own 'pitot' sensors in the intakes.
Paul, re. icing, you hit them all, as in all of the above. Todays news casts did refer to the pilots complaining about icing. Instrument icing has happened, moreso in the past when "pitot heat" wasn't as reliable (our annual recurrent training in the B727 simulator usually had at least one event where the airspeed would very subtly go bad and the check pilot would see if he could 'trick' you into not noticing by dong something distracting, the old pitot heat circuit breaker trick
) ).Icing is always bad news, and everybody tries to avoid it. Modern jets can 'tolerate' up to moderate icing for a short period, but nothing is designed to operate continuously in icing conditions. Note that it's not just instruments but the engines as well that can be affected, as the engine controllers have their own 'pitot' sensors in the intakes.
Paul Thompson 'Hooligan'
Admin
Cheers Pete - Quite a bedtime read that one - all 108 pages..
The opening chapter makes grim reading if you're a passenger travelling somewhere cold..
Thanks Mike :
http://news.sky.com/skynews/Home/UK...ted-Safely-From-Plane/Article/200902215222891
The opening chapter makes grim reading if you're a passenger travelling somewhere cold..
Thanks Mike :
http://news.sky.com/skynews/Home/UK...ted-Safely-From-Plane/Article/200902215222891
icing quick and dirty - adds weight and destroys lift by changing the flow of air over the surfaces of the wings/tail/prop/etc.
Deicing equipment - there are several different types. Some take a while to work, some are best deployed prior to entering icing conditions, and some/most can't keep up with severe ice buildup (depends on build up rate). Some planes use a combination of types. The most common type you will recognize is the black pnuematic "boots" on the leading edges of the wings and tail surfaces. Air is pumped in to expand the pneumatic boot to crack the ice and seperate it from the surface.
There are situations where the black pneumatic boots you see on the leading edges of the wings/tail/etc can be operated and won't clear the ice buildup.
Keep in mind this is from a low time pilot who avoids any possibility of icing conditions....FWIW.
Deicing equipment - there are several different types. Some take a while to work, some are best deployed prior to entering icing conditions, and some/most can't keep up with severe ice buildup (depends on build up rate). Some planes use a combination of types. The most common type you will recognize is the black pnuematic "boots" on the leading edges of the wings and tail surfaces. Air is pumped in to expand the pneumatic boot to crack the ice and seperate it from the surface.
There are situations where the black pneumatic boots you see on the leading edges of the wings/tail/etc can be operated and won't clear the ice buildup.
Keep in mind this is from a low time pilot who avoids any possibility of icing conditions....FWIW.
They were coming in for landing and probably already had flaps deployed and gear down, all drag items, icing on the wings affected lift and probably unknowingly modified stall speed
Someone mentioned that the plan impacted almost vertically which could be explained by an unexpected low speed stall at low altitude
Anything that we say at this point is total conjecture anyway, the follow up investigation using the data recorder info will clarify what really happened
It's still after the fact and a lot of good people died
If we learn from mistakes, let's hope that we learn something good from this one
Dennis
Someone mentioned that the plan impacted almost vertically which could be explained by an unexpected low speed stall at low altitude
Anything that we say at this point is total conjecture anyway, the follow up investigation using the data recorder info will clarify what really happened
It's still after the fact and a lot of good people died
If we learn from mistakes, let's hope that we learn something good from this one
Dennis
Ian Anderson
Lifetime Supporter
And another at London City airport (not Heathrow)
Said to be on landing from Amsterdam and the front wheel collapsed.
Everybody on this survived with only 2 minor injuries (per BBC)
Ian
Said to be on landing from Amsterdam and the front wheel collapsed.
Everybody on this survived with only 2 minor injuries (per BBC)
Ian
Information as to what the [US crash] flight recorder 'saw' has been released and indicates the plane went into a series of violent pitch and roll axis movements.That would be consistent with a stall and efforts to recover.No commo from flight crew to alert anyone to problems.Probably too busy trying to keep the plane in the air.
Not looking good, guys...(are there any ladies on this forum?). Last reports on the news and the internet say a)they got the stick shaker, b) they got the stick pusher and c) the autopilot was on. Given that 99% of the stuff the news puts out immediately after an accident is BS and you can't realistically come to any conclusions or even informed guesses, the above 3 points if true are difficult to reconcile. There are very clearly defined and practiced pilot responses to any/all of the above (some inn fact contrary to good 'piloting' vs. driving by the FAA book in IMHO - geared to the lowest common denominator - maybe some of our other professional airplane drivers would care to comment on this).
It will be interesting to see how this unfolds.
Alohas,
Mike
It will be interesting to see how this unfolds.
Alohas,
Mike
Mike,
What news organization reported that?
Good point about being difficult to reconcile, generally speaking, either the shaker or the pusher would disconnect the selected/coupled autopilot.
Regards,
S
What news organization reported that?
Good point about being difficult to reconcile, generally speaking, either the shaker or the pusher would disconnect the selected/coupled autopilot.
Regards,
S
A horizontal stab stall would need the different reactions of the wing stall, no?
My understanding is the tail stall causes buffeting/porposing up to and then sharp nose down after stall with real heavy pitch control.
From what I have read, recovery - in generic terms not specific to that plane - is reduce flaps, reduce power and load the stab.
So not knowing which surface stalled they could have acted inappopriately. Given they were so close to the ground....
My understanding is the tail stall causes buffeting/porposing up to and then sharp nose down after stall with real heavy pitch control.
From what I have read, recovery - in generic terms not specific to that plane - is reduce flaps, reduce power and load the stab.
So not knowing which surface stalled they could have acted inappopriately. Given they were so close to the ground....
I agree that it would be interesting if they figured out that the tail-feathers were the ones that were iced up and the horizontal stabilizer were the one that actually stalled..
I think that the control inputs would be the same for either Wing stall or the Horizontal Stab stalled..
If the wing stalls - you push the yoke in to gain airspeed and break the stall..
If the HS were to stall - the nose would probably pitch up - leading you to push the yoke in to regain control of the aircraft..
I think that the control inputs would be the same for either Wing stall or the Horizontal Stab stalled..
If the wing stalls - you push the yoke in to gain airspeed and break the stall..
If the HS were to stall - the nose would probably pitch up - leading you to push the yoke in to regain control of the aircraft..
actually, the tail stall causes rapid pitch down and it is a different recovery...if you have time - check this video out:
Tailplane Icing
Tailplane Icing
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The reports were on CNN, quoting the NTSB findings from the tapes.
Re. a 'tail' stall, several problems with that.
a) The stick shaker/pusher is activated by an AOA (angle of attack) probe predicated on wing AOA.
b) With the exception of the F-16 in supersonic flight (it's essentially neutral to positive subsonic), all conventional aircraft have positive stability, where the center of gravity (CG) lies ahead of the center of lift, pulling the nose 'down. This 'nose down' bias is countered by the 'tail down' force of the horiz. stab., keeping everything in balance and giving the pilot pitch (and AOA) control. If the stab. stalled (not sure I've ever heard of this happening), it would 'help' to unstall/unload the wing by lowering the nose (same thing the stick pusher is trying to do).
c) The autopilot 'would' dis-engage at some point.
d) The response is "firewall the throttles" and never mind EPR limits (auto EEC/DEEC systems will not allow you to blow it up). If you're falling out of the sky/stalling, you want all the power you can get to break the stall (reduce AOA) and get all the flying speed you can. My earlier reference to FAA checkride responses was that they grade you on 'minimum altitude loss' during recovery. My approach to this crisis is the grading should be not to hit the ground. In a simulator, with zero viz., that's all the objective criteria they can obtain, since you could argue altimeter error and whether you actually hit the ground, I guess. Personally, I would use all the altitude I had available to ensure I broke the stall.
A stall, by the way, is caused by exceeding the max AOA, not airspeed. We talk speed because we assume 1 g flight. If the AOA is below max, you're not stalled, regardless of airspeed.
Say you have 100 knot "stall speed", 1 g level flight. You could pull the nose up as in the start of a loop, wait till you approached 100 knots while still very nose high, then begin to unload/reduce g. You could get the airspeed down to small numbers, roll left and right, do anything except increase the g/AOA. The airplane is not stalled, just a little 'ballistic'. You still control pitch, roll and yaw. As you nose over and gain speed, you can increase the g/AOA, and eventually regain 1 g as you reach 100 knots. No magic here.
Sorry, guys, got a little carried away)
Re. a 'tail' stall, several problems with that.
a) The stick shaker/pusher is activated by an AOA (angle of attack) probe predicated on wing AOA.
b) With the exception of the F-16 in supersonic flight (it's essentially neutral to positive subsonic), all conventional aircraft have positive stability, where the center of gravity (CG) lies ahead of the center of lift, pulling the nose 'down. This 'nose down' bias is countered by the 'tail down' force of the horiz. stab., keeping everything in balance and giving the pilot pitch (and AOA) control. If the stab. stalled (not sure I've ever heard of this happening), it would 'help' to unstall/unload the wing by lowering the nose (same thing the stick pusher is trying to do).
c) The autopilot 'would' dis-engage at some point.
d) The response is "firewall the throttles" and never mind EPR limits (auto EEC/DEEC systems will not allow you to blow it up). If you're falling out of the sky/stalling, you want all the power you can get to break the stall (reduce AOA) and get all the flying speed you can. My earlier reference to FAA checkride responses was that they grade you on 'minimum altitude loss' during recovery. My approach to this crisis is the grading should be not to hit the ground. In a simulator, with zero viz., that's all the objective criteria they can obtain, since you could argue altimeter error and whether you actually hit the ground, I guess. Personally, I would use all the altitude I had available to ensure I broke the stall.
A stall, by the way, is caused by exceeding the max AOA, not airspeed. We talk speed because we assume 1 g flight. If the AOA is below max, you're not stalled, regardless of airspeed.
Say you have 100 knot "stall speed", 1 g level flight. You could pull the nose up as in the start of a loop, wait till you approached 100 knots while still very nose high, then begin to unload/reduce g. You could get the airspeed down to small numbers, roll left and right, do anything except increase the g/AOA. The airplane is not stalled, just a little 'ballistic'. You still control pitch, roll and yaw. As you nose over and gain speed, you can increase the g/AOA, and eventually regain 1 g as you reach 100 knots. No magic here.
Sorry, guys, got a little carried away
)
