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Continental TurboProp crash inbound for Buffalo

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Continental TurboProp crash inbound for Buffalo

Old 16th Feb 2009, 21:41
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grebleww123 thanks regarding saab340

thanks for the information

regards
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Old 16th Feb 2009, 21:41
  #482 (permalink)  
 
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Jim ..

Thank you.. interesting reading.
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Old 16th Feb 2009, 21:43
  #483 (permalink)  
 
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Originally Posted by Teddy Robinson
"Several posts states - NTSB is cited as the source - that the crew of CO3407 flew ONLY 134 knots when selecting gear and initial flaps."

What I was trying to get at a few pages back with a question re the static ports .. their position and ice protection was this

A static blockage at altitude will lead to an IAS higher than the TAS .. because the environmental dynamic & static pressure is being measured against a (lower) static pressure that existed at a higher level, that at which the blockage occurred.

On my type we have 3 static sources for the ADC, which are well protected and a comparator warning to back it up, BUT failure of any of the ice protection systems will only generate an amber caution.

So, whats the score with the Dash 8 ?

TR
The problem with the scenario of false IAS indication is this:

Any fault in (say) deicing of the statics or pitots which leads to the ADCs overreading and the crew not realising how slow they are will also cause the FDR to record the same erroneously high speeds. It's a pound to a penny that the speeds the NTSB is quoting based on the FDR are from the same source(s) as the crew relied on.

I believe the static system on the dash is pretty well protected - and if it were in fact in error it would have been obvious to the NTSB because all the altitude data they've been releasing - 1800ft to 1000ft in 5 secs, etc., would have also been compromised by the static error. So if there were a static source problem I'm sure (1) they'd know and (2) they'd have already said something to that effect. Nothing released to date indicates a static source, or airspeed system of any kind, error.
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Old 16th Feb 2009, 21:52
  #484 (permalink)  
 
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Oval 3, if an approach is made in icing conditions, it is assumed that the aerodynamic surfaces are contaminated by a degree of ice. This remains the case unless it is visually confirmed that such contamination does not exist.

To give a margin of protection against the degraded performance of these contaminated surfaces, the incresed ref switch is activated. This increases the speed at which the aircraft stall protection system operates - ie the stick shaker and stick pusher. If this switch is used for approach and landing, the pilots must increase the speeds they fly at so as to maintain the same margin above stall protection system activation.

For a flap 15 landing, this increment is 20 knots.

The Embraer 145 has a similar system. It activates automatically with an ice encounter. Even if you subsequently fly an approach in non icing conditions in a hot climate a thousand miles from where you had your ice encounter, it cannot be reset, and you need to increase your landing speeds.
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Old 16th Feb 2009, 21:59
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Some of you have ask about Tailplane icing. Here is a link for a video, 23 minutes but worth watching.
http://video.google.com/videoplay?docid=2238323060735779946
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Old 16th Feb 2009, 22:02
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Thanks, TSF. I love how the media call it an "anti-stall device."

Oval 3...
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Old 16th Feb 2009, 22:10
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The Shop Floor

The minimum clean speed of 190 kts you mention in post #493 - is that speed required by Flight Manual or by SOP?

And what is the max. speed for flaps 15 extension?

thks
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Old 16th Feb 2009, 22:35
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I missed today's NTSB briefing, but Flight Global has an article summarizing some of the statements made.

NTSB aims to shift Colgan Q400 wreckage within two days
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Old 16th Feb 2009, 22:35
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Just looked at the manual again, and that 190kt speed is min speed clean in the hold with icing conditions.

The table below shows the increments to vref when in icing conditions.


Flaps VAPP VGA VREF HOLDING
0 +25kts +20kts +25kts 190kts MIN
5 +20kts +20kts +20kts
10 +20kts +20kts +20kts
15 +20kts +20kts +20kts
35 +15kts

Vref flap zero at 24 tonnes is somewhere near 150 kts, so min speed with the increased ref clean should be 175 kts.

VFE flap 15 is 172 kts.
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Old 16th Feb 2009, 22:40
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The Shop Floor

Just to clarify, from my company Ops manual, 190kts is MINIMUM speed in severe icing.
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Old 16th Feb 2009, 22:45
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Correct, plus min in any ice in the hold. So max flap 5 in severe icing by default.
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Old 16th Feb 2009, 22:57
  #492 (permalink)  
 
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Airspeed data?

The NTSB has released quite a bit of data regarding load factor and pitch / roll excursions during the last portion of the flight. Has any airspeed data been released? I would imagine with the wide ranges of attitudes and normal accelerations experienced, airspeed must have swung over a wide range as well.
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Old 16th Feb 2009, 23:02
  #493 (permalink)  
 
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Max speeds:
gear extension 200kts
flap 5 200kts
flap 10 181kts
flap 15 172kts
flap 35 158kts
out of interest 24,000kg landing mass gives:
clear of ice / suspected ice or icing conditions
Vref flap 0 143kts / 163kts
flap5 132kts / 152kts
flap 10 122kts / 142kts
flap 15 117ts / 137kts
flap 35 112kts / 127kts
flap 35 incrament is + 15kts
normal procedure is flap 5, then gear down, normaly flap 15 condition levers max, then if required flap 35. flap 35 is normal with short feild length and when using increased ref speeds. flap 15 for cat2 and longer runways.
certainly company sop to hold at 190 in icing conditions.
There is no aerodynamic stall detection device (as on c152) the system relies on inputs from various sources inc aoa etc and works it out. then activates stick shake - if that does not grab your attention then stick push - earlier posts give the parameters. The increse ref switch alters the criteria (again as outlined earlier) and raises the red band by about 20kts.
The saab340 did not have an increased ref switch one had to add 20 odd kts to the minimum manover speeds to compensate for ice and obviously increase the vrefs.
there was a sf 340 case in aus where the a/c descended through ice leveled and slowed for the aproach. The speed decayed and the a/c physicaly stalled long before the stick shake/push. if memory serves they recovered with not many feet of air underneath them.
IF the 134kts speed is correct as reported earlier they would probably be in the region for stick shake even with flap 10 (asuming inc ref switch on).
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Old 16th Feb 2009, 23:05
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Other Dash 8 following accident airplane

It would sure be interesting to know some more about the experience of the other Dash 8 that followed the accident airplane. Below are some questions that I would want to ask that crew:

1. How much of the approach was flown with autopilot vs. manually?

2. When during the flight were de-icing boots activated?

3. What flap setting was used for the landing?

4. If Flaps 15 was selected, when? Was the autopilot engaged at that point? Was there anything remarkable about the handling when the final flap setting was selected?

5. What was the aircraft weight during approach and what speeds were flown at the various flap settings used?

6. How did the flight path (track and altitude) compare between these two airplanes during their flights?

Always looking for more info.
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Old 16th Feb 2009, 23:14
  #495 (permalink)  
 
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Pitot Heat

Reminded me of the Flybe incident where the IAS and altitide indications became erroneous due to the pilots forgetting to activate the pitot/static probe heat.
The first planes I flew were 1940s technology and they all had pitot heat switches which had to be turned on by hand. All planes with 1950s (and later) technology had automatic pitot heat, i.e., it was ALWAYS ON.

Why the change? Why go back to manually operated pitot heat?
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Old 17th Feb 2009, 01:58
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AVweb reporting today

The crew of the Bombardier Q400 that crashed in Buffalo on Thursday got a stall warning and the stick pusher engaged but still the aircraft pitched upward 31 degrees before turning almost 180 degrees and dropping onto a house in the Buffalo suburb of Clarence Center, near the outer marker for Buffalo Niagara International Airport. The sequence of events, which included a 45-degree dive with a 106-degree right bank ended 26 seconds later in the fireball on the ground, killing 49 people on the plane and one on the ground, the owner of the house. Although icing continues as a theme in the investigation, reporters were told at an NTSB press briefing on Sunday that the aircraft's anti-icing system had been on for most of the flight and, while both pilots discussed the "significant" icing their aircraft was experiencing, at no time did they use the "severe icing" descriptor that is the official notification of flight-threatening buildup. "We don't know that it was severe icing," NTSB member Steve Chealander told reporters. "They [the crew] didn't say that it was severe icing....The weatherman didn't say that it was severe icing."

Initial reports suggested the aircraft, flying as Continental Connection Flight 3407 dove on the house but later reports said it crashed in a flat attitude. According to data released at the press conference, the last radar hit showed the aircraft with a forward speed of only 100 knots and it lost 800 feet in five seconds. The autopilot was on for part of the sequence and the engines were set to full power just before impact.
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Old 17th Feb 2009, 02:31
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I heard on a local radio show moments ago, that an eyewitness (or three actually) is claiming they saw fire from an engine prior to impact. Take this, of course, with a grain of salt.
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Old 17th Feb 2009, 03:12
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I heard on a local radio show moments ago, that an eyewitness (or three actually) is claiming they saw fire from an engine prior to impact. Take this, of course, with a grain of salt.
not significant when there is an aircraft upset, the engines often get starved of air and surge.

Although in this case it's just as likely that the flash was from a nav light.

The factual which trumps all eye witnesses is the statement by the NTSB that the engines were at full power as the pilots tried to pull out of the stall.
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Old 17th Feb 2009, 07:28
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Originally Posted by lomapaseo
And how is the flight crew able to see and interpret this for the specific aircraft?
Originally Posted by me
They read their flight manual.
Originally Posted by lomapaseo
a rather dismissive post, but I intend to pursue this issue anyhow.
Ok. The baby Dash 8 flight manual I have gives clear guidance on what indications you'll have for severe icing (ice build up on pilot's side window and build up of ice on prop spinner aft of the spinner nose toward the blades.) I assume that all aircraft have similar guidance. The answer to how a flight crew is supposed to see and interpret whether severe icing conditions exist is that they become familiar with the aircraft flight manual and when what they see matches what is described, they are to consider themselves to be in severe icing. It does not require a knowledge of the AIP description of severe icing or the ability to interpret it.
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Old 17th Feb 2009, 08:57
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An CAA incident report documents 2 Dash-8-100 pilots letting the speed drop from 170 to 104 kts climing after departure, while they was picking up ice at the same time.

Then the stick shaker activated, the autopilot turned off, they fell 4,200 feet. they stalled 3 separate times and finally recovered. They continued to their destination where they reported a "turbulence event."
Oops.

Looks like they might have been using VS in the climb instead of IAS.
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