Not so good news about flight 3407

[Captzaahlie]

But the left wing wasn't. That sentence right there should tell you all you need to know about the average reporter when dealing with aviation.

Thats easy, it proves the wings musta come apart

too..... (sarcasm implied)

somebody email the NTSB and let them know about

the oversight!

 

[Captzaahlie]

NTSB already released preliminary airspeed data.


Chealander says the crew's intended landing configuration was with 15° of flap, and that initial calculations put the Q400's weight at 55,000lb (24,950kg) with a reference speed of 119kt - this rose by 20kt, to 139kt, as a result of the precautionary activation of a switch to increase stall margins. Preliminary flight-data evidence puts the aircraft's calibrated airspeed at 134kt, but Chealander warns against reading too much into the early figures.


Calibrated airspeed (CAS) is the speed shown by a conventional airspeed indicator after correction for instrument error and position error.

From what I gather they were at 134kts "before" the a/c was configured @ flaps 15. Right?

 

[Captzaahlie]

I hope for the crews memory that it was a freak accident and not pilot error.

I hope the same thing.

 

[Captzaahlie]

Um, yeah. Maybe the NTSB will rule this one:

FREAK ACCIDENT

I think you are miss the point of empathy for the crew. Deserved or not....

 

[dmspilot00]

The commuter plane slowed to an unsafe speed as it approached the airport, causing an automatic stall warning, these people said. The pilot pulled back sharply on the plane's controls and added power instead of following the proper procedure

IF this is true then it would be the second accident in recent memory in which the pilots misused the autopilot, stalled, and then recovered inappropriately.

 

[Newf Dog]

"From what I gather they were at 134kts "before" the a/c was configured @ flaps 15. Right?"

Correct. From what I read in NTSB data (someone please correct me if I'm incorrect):

Gear down was selected at 134 knots

20 seconds later flaps 15 was selected

14 seconds later shaker activates as flaps transition from 5 to 15 (about 10 degrees...seems like a long time for that)

As I said earlier, we get only "snippets" of "selected" data and naturally as pilots we try to put this together. They've listened to the CVR. They know damn well what happened. As someone else said however they will cover all their bases. If you read the Comair 5191 final report they even have information on what time and how frequently each crewmember used their hotel room key cards (that should scare some folks!)

I know they have to pander to the media but they (NTSB) really shouldn't be releasing bits and pieces of information until they have at least the basis for a theory.

I apologize if any of the above is incorrect information but that's the way I read the NTSB data.

 

[777forever]

As far as the 31 degrees of pitch up I want to know where the AP left the trim when it was disconnected...

 

[ultrarunner]

By all accounts, the stick shaker disconnected the autopilot. Stab trip would have been at whatever IAS was at that point...likely 100 kias or so...

Ok, so the stick shaker activates approaching the stall.

The aircraft was doing 134 before being configured. The adjusted Vref was 139. So, 139 represents 1.3Vso. Stall speed would then be "approximately 99 kias or so, depending naturally upon the amount of ice, bank angle, etc...

So, the plane likely slowed a hundred knots or so...

..stick shaker activated...
..AP disconnects...

Trim would have had the plane trimmed for 100 kts or what ever speed was indicated when the shaker disconnect the AP.

...speed likely continued to decay for another second or two during the "OH $HIT" phase...

...pusher fired
...Cpt yanked the control column to his chest...
...the resulting excessive ANU resulted in either an additional airframe stall, or an excessively slow IAS to make recovery impossible from the low altitude.

 

[LJ45]

The aircraft was doing 134 before being configured. The adjusted Vref was 139. So, 139 represents 1.3Vso. Stall speed would then be "approximately 99 kias or so, depending naturally upon the amount of ice, bank angle, etc...

.

Not right, there is a switch which moves the stall warning up to a higher speed when in icing conditions in this aircraft.

 

[ultrarunner]

Not right, there is a switch which moves the stall warning up to a higher speed when in icing conditions in this aircraft.

You're correct about the switch. I believe the computed Vref was 119 for their landing weight. The switch adjusted that to 139. So I accounted for that in my math. Or did I miss something?

Earlier in the thread:

NTSB already released preliminary airspeed data.


Chealander says the crew's intended landing configuration was with 15° of flap, and that initial calculations put the Q400's weight at 55,000lb (24,950kg) with a reference speed of 119kt - this rose by 20kt, to 139kt, as a result of the precautionary activation of a switch to increase stall margins.....