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Continental TurboProp crash inbound for Buffalo

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Continental TurboProp crash inbound for Buffalo

Old 14th Feb 2009, 21:46
  #221 (permalink)  
 
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c of g

Having flown many times in the UK on a Q400 the cabin crew have been very alert to loading and counting the passengers seated in each bay. The chance of moving fore and aft has always been refused due loading restrictions.
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Old 14th Feb 2009, 21:48
  #222 (permalink)  
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The Q400 isn't difficult to load correctly it just has a pretty narrow CofG (despite what the Bombardier website says) and is trim sensitive due to it's length. If you're hand flying it you can feel the cabin crew walking up and down the cabin. The CofG limits are well within the aircraft capabilities otherwise it wouldn't be certified. It would be easy to exceed these limits, depending on where the actual MACTOW is, if, for example, you had a bundle of passengers move from one end to the other but that is probably true of most types.

I can't compare it to the baby models as I've never flown them but general handling wise it's not too bad. The biggest problems come from the limited flare available because it's so long and you WILL get a tail strike at 9 degrees pitch. Also the stiff landing gear doesn't give ego stroking touch downs like the 146. It doesn't have any major snags that don't befall any straight wing turbo prop. But I digress.

It does not have a variable incidence tailplane.
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Old 14th Feb 2009, 21:51
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Nearly Full Plane

Since this plane was nearly full, passenger loading would probably not greatly affect center of gravity. Baggage loading would be a different matter.
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Old 14th Feb 2009, 21:55
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Assymetrical Flaps?

Not an expert here but if the aircraft is alleged to have made a steep spin after setting flap 15 is there a possibility that one flap came down and one stayed stowed? The crew tried to retract flap/gears right after.
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Old 14th Feb 2009, 22:07
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Not an expert here but if the aircraft is alleged to have made a steep spin after setting flap 15 is there a possibility that one flap came down and one stayed stowed? The crew tried to retract flap/gears right after.
I believe every certified aircraft has a system to prevent asymmetrical flap deployment. Of course even such a system can malfunction, but the probability seems quite remote. I know of one such event, which actually took place close to my home airport, but it involved a light twin. The cause was a badly maintained flap jackscrew on an old airplane. In contrast this Q400 was quite new.
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Old 14th Feb 2009, 22:25
  #226 (permalink)  
 
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An update on the impact:

NTSB: Plane didn't dive, but landed flat on house

52 minutes ago

CLARENCE, N.Y. (AP) — An investigator says the plane that crashed on a house in New York state landed flat on it and was pointed away from the airport where it was supposed to land.

Steve Chealander (CHEE-lan-duhr) said Saturday that Continental Connection Flight 3407 did not dive into the house, as initially thought.

Chealander says the New Jersey-to-Buffalo flight was cleared to land on a runway pointing to the southwest. But the plane crashed with its nose pointed to the northeast...
The Associated Press: NTSB: Plane didn't dive, but landed flat on house
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Old 14th Feb 2009, 22:41
  #227 (permalink)  
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NTSB: Plane didn't dive, but landed flat on house
That is consistent with the eyewitness report (which was considered very reasonable) posted on page 1 or 2 of this thread. The gear was up, the airplane was in a very slight left bank, and not steeply nose down, (vertical).
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Old 14th Feb 2009, 23:41
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Unlike everyone else, I am not so sure the tail stalled.

Help me out here..... If a tail stalls on any aircraft, the nose will drop, but the wings do not stall. The aircraft will continue to have considerable forward movement. I suppose it might even continue to nose over until inverted.

But the FDR, the accident scene, and eyewitness accounts, suggest a classic stall/spin scenario.

Who's with me on this?
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Old 14th Feb 2009, 23:44
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Iomapaeso (and Interpreter)- The voices on the CVR are analyzed in various ways, such as frequency.. Off the top of my head the radio transmissions of the 'Grand Canyon' midair were 'tonally' investigated and the report commented on the 'stress' of the speakers (pilots).. Also the 737 at Colorado Springs. There are many more - but I've just got home after a 7 hour sector so can't be bothered to look them up..

DC-ATE. Why surprised that the C5 doesn't have hot wings? In several years of flying big 'Buses (in winter ice and snow) I've yet to fire up the wing anti-ice. However, turboprops are a different thing entirely.. If you get ice on those you keep your speed up. The ATR 42/72 has 'red bug' or 'white bug' speeds. To me this accident sounds like 'tailplane stall' - nasty and sudden..
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Old 14th Feb 2009, 23:53
  #230 (permalink)  
 
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NTSB Safety Alert

December 2008 Safety Alert SA-014 warning about aircraft inflight icing is the first linked item at the top of the NTSB website.


Activate Leading Edge Deice Boots As Soon as Airplane Enters Icing Conditions

Thin amounts of ice, as little as 1/4 inch, can be deadly

The problem

• As little as 1/4 inch of leading-edge ice can increase the stall speed 25 to 40 knots.
The danger is that some 1/4-inch accumulations have minimum impact and pilots
become over confident.

• Sudden departure from controlled flight is possible with only 1/4 inch of leading-edge ice accumulation at normal approach speeds.

• For 60 years, pilots have been taught to wait for a prescribed accumulation of
leading-edge ice before activating the deice boots because of the believed threat of
ice bridging.

• In theory, ice bridging could occur if the expanding boot pushes the ice into a frozen shape around the expanded boot, thus rendering the boot ineffective at removing ice.

• The Safety Board has no known cases where ice bridging has caused an incident or accident, and has investigated numerous incidents and accidents involving a delayed activation of deice boots.

• Ice bridging is extremely rare, if it exists at all.

• Early activation of the deice boots limits the effects of leading-edge ice and improves the operating safety margin.

• Using the autopilot can hide changes in the handling qualities of the airplane that may be a precursor to premature stall or loss of control.

• Many airplanes still require pilots to visually identify ice on the wings and its thickness, which can be difficult to see from the cockpit.

• Many pneumatic deice boot systems only provide a means to manually cycle the
system and have no provision for continuous operation.


What should pilots do when they encounter leading edge ice?

• Leading-edge deice boots should be activated as soon as icing is encountered, unless the aircraft flight manual or the pilot’s operating handbook specifically directs not to activate them.

• If the aircraft flight manual or the pilot’s operating handbook specifies to wait for an accumulation of ice before activating the deice boots, maintain extremely careful
vigilance of airspeed and any unusual handling qualities.

• While icing conditions exist, continue to manually cycle the deice system unless the
system has a provision for continuous operation.

• Turn off or limit the use of the autopilot in order to better “feel” changes in the handling qualities of the airplane.

• Be aware that some aircraft manufacturers maintain that waiting for the accumulation of ice is still the most effective means of shedding ice.
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Old 15th Feb 2009, 00:00
  #231 (permalink)  
 
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But the FDR, the accident scene, and eyewitness accounts, suggest a classic stall/spin scenario.

Who's with me on this?
When I read about the crash happening in a flat attitude I thought "flat spin". But I'm just an unqualified spam-can driving observer.

Beech
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Old 15th Feb 2009, 00:11
  #232 (permalink)  
 
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Unlike everyone else, I am not so sure the tail stalled.

Help me out here..... If a tail stalls on any aircraft, the nose will drop, but the wings do not stall. The aircraft will continue to have considerable forward movement. I suppose it might even continue to nose over until inverted.

But the FDR, the accident scene, and eyewitness accounts, suggest a classic stall/spin scenario.

Who's with me on this?
A "normal" tail stall will result in a loss of negative lift, causing the aircraft to nose over.
The stated attitude of the aircraft does suggest more of a flat-ish spin at impact.
I guess if the aircraft approached close enough to the stall that the stick pusher activated, as indicated in the Flight Global link posted above, maybe it's feasible that the elevator, which is optimized for producing a downforce, stalled "conventionally" while attempting to produce an upforce that exceeded the tailplane/elevators' ability to produce, in its iced up state (if it was in an iced up state, and the evidence indicates it was likely to be carrying some ice.)
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Old 15th Feb 2009, 00:26
  #233 (permalink)  
 
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what if?

what if the pitot / static system was compromised giving eroneous air speed readings, and the tailplane stalled followed in a unique situation by a main wing stall?

So, let's not blame the pilots. One must look at the training, the evaulation department, and the training information which is approved by the FAA.
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Old 15th Feb 2009, 00:54
  #234 (permalink)  
 
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According to the NTSB, there were pitch and roll excursions at about the time flaps 15 were selected, whereupon the crew selected flaps and gear up.

A popular scenario is a tailplane stall triggered by increased downforce [ or upforce? ] demand from a section moment change as the flaps came down.

The impact attitude and the fact that only one house is affected is consistent with a flat spin as others have observed.

Possibly the tailplane unstalled as the flaps came back up and the stall protection got behind the configuration change. It's hard to criticise the stall protection given the dynamics of the situation and the icing.
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Old 15th Feb 2009, 01:11
  #235 (permalink)  

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A plane that crashed onto a house in New York state, killing 50 people, fell flat rather than diving as initially thought, investigators have said.

The Continental Airlines Bombardier Dash 8 was also pointing away from the airport it was meant to land at, investigator Steve Chealander said.

Mr Chealander, a spokesman for the National Transportation Safety Board (NTSB), said the flight was cleared to land on a runway pointing to the south-west, but the plane was pointing to the north-east when it crashed.

He said the plane landed flat on the house in Clarence Center, a suburb of Buffalo.

bbc on-line
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Old 15th Feb 2009, 01:26
  #236 (permalink)  
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I would have thought the observed* turn of about 180 was not commensurate with some of the simpler theories. I've not noticed much comment about this.


The NASA video begs the question as to whether there is a case for trimming a T-tailed aircraft differently when expecting icing conditions. Has anyone ever followed such a practice?


* I can't recall the source of the comment.
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Old 15th Feb 2009, 03:02
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What If?

what if the pitot / static system was compromised giving eroneous air speed readings, and the tailplane stalled followed in a unique situation by a main wing stall?
Hard to imagine the crew missing a pitot/static issue. Don't know the Dash-8 or Colgan Ops manual, but I would think that with known ice buildup, pitot heat and alt air would have already been selected. Would have at least noticed AS and ALT anomalies on the descent. But wait for the FDR data to confirm.
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Old 15th Feb 2009, 03:43
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In over 20,000 hrs of flying I have never had any training in tailplane stall. We had some MD80 aircraft that we were required to push the tail deice button before selecting landing flaps but never emphasized. We had an MD80 go to landing flaps and and it pitched over into a dive and they brought the flaps back up to control it so that must have been the tailplane stall. The MD80 was a pos airplane so thought it was because of the tiny elevator that wasn't adequate for the size of the aircraft.

Every pilot should read the post relating to this because Nobody teaches it that I know.
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Old 15th Feb 2009, 04:00
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Bubbers44, I would be very grateful if you could PM me with more details. In the icing accident data that I maintain, I am aware of one ASRS report describing an MD80 tailplane event, and one DC-9 event at my former employer. Any additional information would be very welcome, as I believe this is a greater threat to the MD80 series than any operator is aware of.

Many of you have reviewed the NASA tailplane icing work. I had the opportunity to fly the Twin Otter with ice shapes on the tail, and I flew a demostration series of tailplane events. The Colgan case has none of the signatures of a tailplane stall, so far as I can tell. Tailplane events generally require full or near full flaps, and exhibit no wing rock. The shaker and pusher would not be associated with a tailplane event, and the flat impact is also not consistent with ICTS accident history.

However, there have been a large number of icing events associated with the drag rise resulting from an increase in angle of attack. The first that I know of was Northwest 5 at Moorhead, Minnesota in 1940. The pattern continues through Comair 3272 at Monroe in 1997 and probably N41WE in Wyoming in 2005 at Rawlins, Wyoming. It may well have played a role in the ATR crash at Lubbock a couple of weeks ago.

Gray and Von Glahn reported this phenomona during the 1950’s, and it is supported by considerable research. Basically, if an airplane accretes ice at an angle of attack of, say, 4 degrees, the drag rise from that ice accretion when the AoA is increased to 8 degrees is considerably larger than the drag incurred when the ice is accreted after the AoA is increased to 8 degrees. This explains why everything looks good until the AoA is increased (as at Monroe).

In many cases of general aviation twins up to King Air size, the addition of flaps or gear has been the pivotal "straw that breaks the camel's back". In one of my favorite events, a fellow extended the gear, began to decelerate uncontrollably into a stall, and actually elected to retract the gear on short final and belly land under control.

I put that out more for general awareness rather than speculation on this event. The airplane was equipped with a very complete set of recorders, and if we are patient, a lot of information will likely be forthcoming soon.

I would recommend for those interested a review of the papers presented at the 2007 SAE Aircraft and Engine Icing Conference at Seville, Spain. This can be sen at SAE Aircraft & Engine Icing International Conference: 2007 Session Presentations. Lot of very good papers there.
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Old 15th Feb 2009, 04:11
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Pointing in the wrong direction and with a flat angle. Maybe a flat spin?

It is a gigantic tail, could be a little aft loaded or maybe CG went aftwards with the ICE accumalation chaging the center of pressure.

Flat spin maybe.

Easy to develop, fast and corresponds with the end result?
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