http://www.liveleak.com/view?i=f6d_1212714828

Has the accident report been completed?

CG problem or over-rotation?

 

USAF Says 'Distorted Data' To Blame For Guam B-2 Accident

Fri, 06 Jun '08
Moisture In Transducers Led To Flight Control Errors

The US Air Force says distorted data introduced by a B-2 Spirit's air data system skewed information entering the bomber's flight control computers, ultimately causing the crash of the aircraft on takeoff at Andersen Air Force Base, Guam, February 23. That's the conclusion reached in an Air Combat Command accident investigation report released Thursday.

Moisture in the aircraft's Port Transducer Units during air data calibration distorted the information in the bomber's air data system, causing the flight control computers to calculate an inaccurate airspeed and a negative angle of attack upon takeoff.
According to the report, this caused an, "uncommanded 30 degree nose-high pitch-up on takeoff, causing the aircraft to stall and its subsequent crash."
Earlier reports stating a fire onboard may have contributed to the crash were apparently erroneous. Instead, the USAF says, moisture in the PTUs, inaccurate airspeed, a negative AOA calculation and low altitude/low airspeed were substantially contributing factors in the mishap.
Another substantially contributing factor was the ineffective communication of critical information regarding a suggested technique of turning on pitot heat in order to remove moisture from the PTUs prior to performing an air data calibration.
The pilot received minor injuries, and the co-pilot received a spinal compression fracture during ejection. He was treated at Tripler Army Medical Center, Hawaii, and released. The aircraft was assigned to the 509th Bomb Wing at Whiteman Air Force Base, MO.

...there is also a thread at FI.
...and video (2nd plane). http://www.acc.af.mil/shared/media/d...080605-049.wmv

 

Technique of turning on pitot heat?!!! Nearly $ 2B lost and we're talking pitot heat? Jeez. At least the guys made it out.

 

You know how the military works... you hand down techniques and "techcedures" from guy to guy and everyone knows them. Then some dudes get in a rush, forget to turn the pitot heat off after a ADC calibration and after destroying a pitot static system get crucified. If they had turned the pitot heat on and it doesn't say to do it in the TO, some AIB weenie would crush them for not following procedures when they damage the jet. Don't turn it on and you crash the jet. I think we should be more concerned that a B-2 can be brought down by a squirt gun .

 

Agreed. My take was from the perspective of someone whose experience required turning on pitot heat for each aircraft I've flown. I took for granted the B-2 likely required such a procedure.

 

Guess I'll subtract 1 billion dollars from my checking account.

 

It says "turn on pitot heat for Air Data Calibration....."

This means theay are suggesting when the ADC is calibrated (and I'm making an assumption here), they are trying to dry-out the system. I am assuming ADC calibration is a maintenance function.

This is not an Air Florida "Whoops; forgot to turn on the pitot-heat" accident.

 

Well, I don't know how much effect pitot heat would have during a preflight and takeoff in Guam. I know that people are suggesting it was just moisture built up but I don't know if it would be so little that it could just be burned off by pitot heat. I won't pretend to know anything about the B-2 systems but I know i have had totally unreliable AOA and told maintenance , they told me it was moisture and they would fix it. I watched them take off the probe cover and pour water out of the probe. Not the kind of moisture that the heat would burn off. Again I don't want to say this was the same type of situation but if turning the heat on was that important I think it would be mandatory not suggested. I'm also sure like faipsrule said the AF will take any opportunity to place the blame on the crew that they can.

 

There have been several posts on this...the pitot was not used during CALIBRATION of the ADC. Nobody said that crew did not use it for takeoff. Since the ADC was calibrated incorrectly, it misinterpreted it's air data inputs and cause the airplane to initiate an uncommanded pitch up, which led to stall.

Nothing to do with the flight crew.

 

Ok, but my point still is that even during calibration I'm not sure that turning the pitot heat on would get rid of the moisture. And I'm not saying I'm right just a thought generated from past experience.