B-2 Accident Info Released

[JFReservist]

Public site version. The text analysis and statement of opinion for the go/no go decision is interesting and should spark some good 'hangar fly' discussions. Not to divulge anything, but is it normal for that airframe to have a 42 knot split between a reject decision and rotate speed?!? I know the crew got out, does anyone know how they're doing?

http://www.acc.af.mil/accspecialreports/b-2accidentinvestigationboard.asp

 

[SIG600]

The cost of the lost aircraft is about $1.4 billion

Ouch. That's like 1/2 an aircraft carrier.

 

[erj-145mech]

I know the crew got out, does anyone know how they're doing?

http://www.acc.af.mil/accspecialreports/b-2accidentinvestigationboard.asp

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.

 

[Lilah]

The video is pretty amazing.....

http://www.acc.af.mil/shared/media/document/AFD-080605-049.wmv

Lilah

PS> The accident flight starts about halfway through...

 

[mudkow60]

Not to arm-chair, but what happened to pilot feel and sensory perceptions? Were they both IFR and under the hood? That looked like a pretty sever take-off angle.

Just my observation....

 

[satpak77]

Not to arm-chair, but what happened to pilot feel and sensory perceptions? Were they both IFR and under the hood? That looked like a pretty sever take-off angle.

Just my observation....

I doubt their is much of that in that type of airplane, with everything fly-by-wire and computer controlled, etc, along with that engine noise. I doubt much visual perception exists looking out of those little cockpit windows either.

 

[414Flyer]

Not to arm-chair, but what happened to pilot feel and sensory perceptions? Were they both IFR and under the hood? That looked like a pretty sever take-off angle.

Just my observation....

""uncommanded 30 degree nose-high pitch-up on takeoff,"

Met some of your fellow 60 drivers in AK other day, we used their facility in Cordova AK as a fueling stop for paracargo missions to a glacier research station

 

[mudkow60]

satpak77,

I disagree with you. While I don't know if there was a computer glitch or something of that nature, I am sure that the pilots and all on-board realized they were fu*ked when the nose pitched up that high on the take off roll. And, I would have to disagree with visual perception not playing a big part on take-off and landing. While I am just a helo bubba, my buddies fly the 747 and they have to fly that giant all the way to the ground.

How is Alaska, and do we know each other?

 

[414Flyer]

We dont know each other, just seen your posts about being a CG pilot. Alaska is fun, the paracargo mission was in support of National Science Foundation I think, 6 drops at a glacier. We had permission to get fuel from Cordava, it was being manned by a detail out of Kodiak.

 

[erj-145mech]

satpak77,

I disagree with you. While I don't know if there was a computer glitch or something of that nature, I am sure that the pilots and all on-board realized they were fu*ked when the nose pitched up that high on the take off roll. And, I would have to disagree with visual perception not playing a big part on take-off and landing.

The official cause, by the accident board:

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.

 

[SIG600]

satpak77,

I disagree with you. While I don't know if there was a computer glitch or something of that nature, I am sure that the pilots and all on-board realized they were fu*ked when the nose pitched up that high on the take off roll. And, I would have to disagree with visual perception not playing a big part on take-off and landing. While I am just a helo bubba, my buddies fly the 747 and they have to fly that giant all the way to the ground.

How is Alaska, and do we know each other?

The 747 is not a fly-by wire aircraft. Every flight control surface moves completely different to what you would think when control inputs are given. You tell the computer what to do, it manipulates the controls to make it happen. It's what allows me to be in complete control of the Hornet at > 35 AOA, fully stalled, and still point the nose where I want. The caveat to this is that if the info going to the magic boxes is erroneous, then so are the outputs to the control surfaces. Garbage in, garbage out. As far as that B-2 was concerned, it was doing everything right, with the f_cked up info going to the computers.

 

[mudkow60]

Well shoot me if there is not an override feature (as when the Airbus plowed into the trees in France), but even in the Dolphin, you can overpower or kick off the computer when it goes tits up. All I am saying is that it would appear, early in the take off, at the point of rotation, that something was going very wrong.

 

[MountainFreak]

Pure speculation here, but flying wing designs are inherently unstable. There is a pretty good chance that the B-2 requires operating flight control computers to fly at all. I believe the F-16 is similar in that respect.

Anyway, this report raises even more questions in my mind. For example, isn't the pitot heat automatically turned on, like in many modern aircraft, especially those with FCC's?
And doesn't the plane have reduntants ADC's? Did they all fail in the same manner? Maybe a B-2 insider can give us the unclassified info.

 

[Colonel Savage]

It appears that after the initial over rotation the pilot manages to reduce the pitch attitude (2+00 sec) and regain some control (w/some ocilations 2+10 sec), but then seems to lose directional control and yaw with a slight roll to the left (2+13 sec). At 2+15 sec the wingtip strikes and the ejection sequence begins, followed by the crash.

It appears to me to be the loss of yaw and roll control and subsequent wing tip strike is what causes the accident, so the question becomes what caused the loss of yaw and roll control.

One theory that comes to mind is that engines, when subjected to extremely high angles of attack, can become starved of inlet air due to disturbed or blocked air flow. The B-2, being designed as a bomber, and having the engine inlets placed several feet aft of the leading edge, could have been subjected to this effect.

 

[Huggyu2]

Not to divulge anything, but...

YGBFSM.


And the price tag is about $2.2B, not $1.4B

 

[MJG]

Wow! I had no idea the actual accident was caught on video. Pretty wild to see.

 

[scoreboardII]

Good for the pilots getting out, they almost waited to long.

Now, I sure hope my USAF submits the bill directly to the manufacture for 2.2B.

 

[SIG600]

Good for the pilots getting out, they almost waited to long.

They were probably waiting for the computer to let them eject.

That whole joke about pulling the handle and HAL just saying, "try harder."