Continental TurboProp crash inbound for Buffalo
Is this 134kts value from the pitot static system and ADCs or from the GPS/FMS?
The red snake coming up the PFD should have been pretty obvious if the ADC data was telling the flight deck the correct IAS.
New aircraft, so should have the modified pitot system installed from factory which should have prevented icing in the pitot static system.
Possibly pitot probe failure (and mis-selection of ADCs?) or pitot probes not switched on?
Not sure ATC would be too suprised to see a Dash back at 135 kts at that distance out
The red snake coming up the PFD should have been pretty obvious if the ADC data was telling the flight deck the correct IAS.
New aircraft, so should have the modified pitot system installed from factory which should have prevented icing in the pitot static system.
Possibly pitot probe failure (and mis-selection of ADCs?) or pitot probes not switched on?
Not sure ATC would be too suprised to see a Dash back at 135 kts at that distance out
Gender Faculty Specialist
Regarding the 134kt IAS. If you look at the speeds posted a couple of pages back you will see that Vref Flap 0 is 143kts for the weight of 24,000kgs. Now if you factor in the increased ref speed of plus 20 kts you obvioulsy get 163kts.
IIRC the Dash Vref is calculated by Vs multiplied by 1.23.
So working in reverse 163kts Vref Flap 0 (Icing) divided by 1.23 = 132.5kts Vs. Scarily close to the 134kts IAS which apparently they had been flying at.
If this was the case then the low speed cue should have been glaringly obvious.
IIRC the Dash Vref is calculated by Vs multiplied by 1.23.
So working in reverse 163kts Vref Flap 0 (Icing) divided by 1.23 = 132.5kts Vs. Scarily close to the 134kts IAS which apparently they had been flying at.
If this was the case then the low speed cue should have been glaringly obvious.
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iompaseo
I imagine if I got a stick pusher that wasn't really required for stall protection, I would pull back...that would cause a pitch oscillation if the pusher was as strong as I was.
ALL I am saying is this. We have a pilot smart enough to turn on the wing ice protection 11 minutes after takeoff...to note ''significant ice'' on the CVR and he isn't keeping up extra speed? something ain't right here. did he have an incorrect air speed readout/display?
Was he just out of winter school and took a stick pusher to be a tailplane stall?
Or is there something else out there. Would he have heard from Bombardier that the 400 wouldn't tailplane stall?
So much information overload and then to raise the gear...that doesn't make sense to me.
I imagine if I got a stick pusher that wasn't really required for stall protection, I would pull back...that would cause a pitch oscillation if the pusher was as strong as I was.
ALL I am saying is this. We have a pilot smart enough to turn on the wing ice protection 11 minutes after takeoff...to note ''significant ice'' on the CVR and he isn't keeping up extra speed? something ain't right here. did he have an incorrect air speed readout/display?
Was he just out of winter school and took a stick pusher to be a tailplane stall?
Or is there something else out there. Would he have heard from Bombardier that the 400 wouldn't tailplane stall?
So much information overload and then to raise the gear...that doesn't make sense to me.
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I believe the NTSC briefing spoke of calibrated speed of 134 knots
I asked before, what is the chance that whilst 134 CAS was the true speed, that the indicated airspeed was substantially higher (and therefore giving the crew a false sense of security)?
Any opinions?
The reason I ask is that it must be quite exceptional if both pilots fail to notice this low speed
I asked before, what is the chance that whilst 134 CAS was the true speed, that the indicated airspeed was substantially higher (and therefore giving the crew a false sense of security)?
Any opinions?
The reason I ask is that it must be quite exceptional if both pilots fail to notice this low speed
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vanHorck,
The difference between IAS and CAS on commercial aircraft is small and not a factor you consider in daily operations - so no chance!
A small difference between left and right indications is allowed, and limitations are found in the limitations section of the Flight Manual.
A small difference between left and right indications is allowed, and limitations are found in the limitations section of the Flight Manual.
Gender Faculty Specialist
Fireflybob, the difference would be noticeable but I can't give you any hard figures because I can't remember. You can even notice the difference between 210 and 190kts clean. However, you would never ever consider getting that slow in a clean config. even on a good day.
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Robert Campbell
I agree with your viewpoints in #555 and #570.
One important factor is the TIME - for how long time did CO3407 fly at this low speed?
Only the flight recorder can give us an answer!
bgrds
One important factor is the TIME - for how long time did CO3407 fly at this low speed?
Only the flight recorder can give us an answer!
bgrds
You'd be looking at a high nose attitude going from 0-3 degrees pitch @190 to something far higher at low speeds. If you're looking back over your shoulder at the wings perhaps you wouldn't get the feeling of increasing pitch. Can't work out what the increasing pitch would feel like, possibly a rolling motion, possibly offset by the aircraft slowing down. A level off at low power would give a pretty quick deceleration
It'd be interesting to see the data from the FDR, may have been a level off with no increase in power. Going along with the looking out at the wings line of thought you'd get no indication of the impending stall until the stick shaker. Doesn't explain the selection of gear/flap without looking at the PFD.
Perhaps fixation on the icing issue is going to be the straw that broke the camels back
It'd be interesting to see the data from the FDR, may have been a level off with no increase in power. Going along with the looking out at the wings line of thought you'd get no indication of the impending stall until the stick shaker. Doesn't explain the selection of gear/flap without looking at the PFD.
Perhaps fixation on the icing issue is going to be the straw that broke the camels back
Gender Faculty Specialist
Cosmos it may not be the actual stall speed but it is now the speed at which the stall protection will activate whether you're covered in ice or not.
There have been many occasions during an approach on a nice day that the stick shaker has activated becasue the increased ref switch has been left on after an icing encounter.
There have been many occasions during an approach on a nice day that the stick shaker has activated becasue the increased ref switch has been left on after an icing encounter.
Well Bernd, I think your question and points are valid. I always understood that "the" deep stall was specific to T-tail jet transports and fighter designs like the 101 and the 104, which, I am informed, is one pulled too hard on in a turn, the aircraft (101 anyway) would pitch up violently as it stalled.
I got this understanding from D.P. Davies' superb "Handling the Big Jets", (1rst, 2nd and 3rd eds.) which I absorbed as a kid and in which the diagram and text describing the "deep" stall shows a DC6-type and B727-type design and the obvious tailplane blanking by the wings, absent the "prop-wash", (almost exactly like the graphic a few pages back on this thread). The diagram showed the '6's tailfeathers in undisturbed slipstream "below" the slipstream of the wings at high angles of attack.
An aft CG stall does not specifically constitute a "deep stall" because the term referred to the propensity of a design to enter same, and not to those circumstances which may stall any design. By such definition, any falling piece of metal is in a "deep stall" and the term is rendered useless in terms of applying to one design vice another.
Just some idle thoughts...
PJ2
I got this understanding from D.P. Davies' superb "Handling the Big Jets", (1rst, 2nd and 3rd eds.) which I absorbed as a kid and in which the diagram and text describing the "deep" stall shows a DC6-type and B727-type design and the obvious tailplane blanking by the wings, absent the "prop-wash", (almost exactly like the graphic a few pages back on this thread). The diagram showed the '6's tailfeathers in undisturbed slipstream "below" the slipstream of the wings at high angles of attack.
An aft CG stall does not specifically constitute a "deep stall" because the term referred to the propensity of a design to enter same, and not to those circumstances which may stall any design. By such definition, any falling piece of metal is in a "deep stall" and the term is rendered useless in terms of applying to one design vice another.
Just some idle thoughts...
PJ2
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Considering the very low approach speed of the aircraft “134 / 137 knots”?
Shouldn’t the A.T.C. have picked up on this and informed the crew?
Shouldn’t the A.T.C. have picked up on this and informed the crew?
Should probably add a gear down data link, and maybe a breath and blood test data link, and flap position, and heck, let's throw in an icing data link. Of course, we don't have a concrete way (yet) to measure ice.
Heck, let's kick out the pilots and have the ATC folks just fly it. It'll save all that data link cost.
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Thanks for the kind words, PJ2. As I said I also got the use of the phrase from the same book.
Since that is quite old already, maybe usage has changed with time.
The detailed descriptions of the deep stall mode for t-tail jets was very interesting anyway. I started reading it only after the recent MD80 accident in Madrid, although there is no way for me tell if that went into "deep stall". Some people said it couldn't have from that low height.
--
Back to Colgan 3407, given the very low speed, it now starts looking like a normal stall? (not deep, not tail-)?
As far as I understand, the 134kts, if they turn out to be right, was too slow even in non-icing conditions for clean configuration?
Bernd
Since that is quite old already, maybe usage has changed with time.
The detailed descriptions of the deep stall mode for t-tail jets was very interesting anyway. I started reading it only after the recent MD80 accident in Madrid, although there is no way for me tell if that went into "deep stall". Some people said it couldn't have from that low height.
--
Back to Colgan 3407, given the very low speed, it now starts looking like a normal stall? (not deep, not tail-)?
As far as I understand, the 134kts, if they turn out to be right, was too slow even in non-icing conditions for clean configuration?
Bernd
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"Handling the Big Jets"
When I first joined this forum about a year ago, I had no idea about handling jets - all my large AC time being in DC-3s and 4s. OK, Semi-large.
D.P. Davies, "Handling the Big Jets" November 2006 edition now resides in its proper place next to the left throne.
D.P. Davies, "Handling the Big Jets" November 2006 edition now resides in its proper place next to the left throne.
Last edited by Robert Campbell; 17th Feb 2009 at 22:45. Reason: spelling
Gender Faculty Specialist
Does an ex-Q400 driver count DC?!
It does stand out fairly well against the black background of the boots. Certainly the kind of ice I've seen on it anyway. You can definitely see it breaking off when the boots were working. The inspection lights work pretty well at night too.
Of course in thick cloud, at night and with the landing lights on there can be quite a bit of light reflecting going on it and that would make it quite hard to see.
It does stand out fairly well against the black background of the boots. Certainly the kind of ice I've seen on it anyway. You can definitely see it breaking off when the boots were working. The inspection lights work pretty well at night too.
Of course in thick cloud, at night and with the landing lights on there can be quite a bit of light reflecting going on it and that would make it quite hard to see.