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Air Force: B-52 crash caused by equipment position

erj-145mech

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A deadly B-52 bomber crash off Guam last year was caused by part of the plane's tail assembly being set in the wrong position, a U.S. Air Force investigation report released Friday said.
The plane's stabilizer trim was improperly set between 4.5 and 5.0 degrees nose-down at impact, indicating the aircraft had been in a nose-down descent at low altitude, according to a report by the Air Combat Command in Langley, Va. The stabilizer trim is used in conjunction with the aircraft's elevator to control the pitch of the aircraft.
The unarmed bomber was on a training mission that included a flyby in support of the Guam Liberation Day celebration when it crashed in July off Guam, a U.S. territory located 3,700 miles southwest of Hawaii. All six crew members on board were killed.
The report said the reason why the stabilizer trim was improperly set could not be determined because there were no survivors or emergency radio calls from the plane. Only a minimal amount of aircraft control systems or instruments were recovered.
The investigation also determined that the combination of a low altitude and a descending left turn, and the crew recognizing too late the severity of the situation, contributed to the crash.
But the board said any experienced crew could have found it difficult to recognize, assess and recover from the rapidly developing situation involving the stabilizer trim setting.
The B-52 was assigned to the 20th Bomb Squadron at Barksdale Air Force Base in Louisiana.
 

PlaneStupid

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There have been several trim related accidents. Including: Pilot induced, runaway trim, and trim motor hooked up backwards.
 

hindsight2020

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There have been several trim related accidents. Including: Pilot induced, runaway trim, and trim motor hooked up backwards.

Runaway trim? in the H model? I'd like to see your source... The one before was brought down by an idiot and before that there have been the low level incident, the one where the aft tank blew up (not an H model), the one where the engines flamed out due to things we shall not discuss here(not an H model either) ...no runaway trim fatality to my knowledge. If you know of instances where H models have been keeling over full stop, from my perspective as an operator, I welcome you to provide me with insightful sources.

--break break-- Huggyu et al

In a nutshell, NO, the Buff is not a historical offender in the runaway stab trim arena. Everybody reach their own conclusion as to why the thing crashed with stab set halfway down the DN stop. I can tell you this much. The AIB sure as hell couldn't say conclusively why; I couldn't even find the phrase runaway stab (which is a boldface) in the whole thing, which is why it left it up to generalities the way it did.

No maintenance witch-hunt for faulty stab trim around these parts of the world as of late either....so conclude/speculate as required.....
 

talondriver

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There have been several trim related accidents. Including: Pilot induced, runaway trim, and trim motor hooked up backwards.

We checked the trim before taxi to include trim cutout switch and opposite yoke pressure to counter a runaway situation.
 

PlaneStupid

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HindSight, the question was about the B52 in general not the H model. If you look at your Strategic Air Command Aircraft Lessons Learned book (might say Air Combat Command now) you will see several accidents related to stabilizer trim. It's a boldface item for a reason. Bottom line with that big tail you better fly it properly trimmed at all times.
 

SpeedBird

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Hindsight, the B-52 that has its tail blown off by an explosion in the aft body tank was indeed an H model and belonged to the 410 BW at K.I. Sawyer AFB. I remember it well since I was sitting on alert that night and the airplane came within an RCH of landing on top of the alert facility. BTW, the name of the airplane was the "Black Widow"
 
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SpeedBird

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HindSight, the question was about the B52 in general not the H model. If you look at your Strategic Air Command Aircraft Lessons Learned book (might say Air Combat Command now) you will see several accidents related to stabilizer trim. It's a boldface item for a reason. Bottom line with that big tail you better fly it properly trimmed at all times.

The more critical issue with flying the B-52 in a trimmed state was the fact that the aircraft had a very short elevator chord (only 10%) connected to a THS that could easily overcome the available elevator control authority of the pilots' yokes if the trim was improperly used, or ran away on its own.
 

hindsight2020

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Hindsight, the B-52 that has its tail blown off by an explosion in the aft body tank was indeed an H model and belonged to the 410 BW at K.I. Sawyer AFB. I remember it well since I was sitting on alert that night and the airplane came within an RCH of landing on top of the alert facility. BTW, the name of the airplane was the "Black Widow"

I never argued the aft tank tail break did not occur in an H model. My point was to ask to be pointed at a documented stab runaway trim mishap in the H model. I've been unable to find one in my research and I suspect there is none. For an aircraft with the service history of the Buff, that says a LOT, most aircraft in inventory wouldn't even have that kind of service life to begin with to even be able to calculate such statistic, so that's strike two against the stab trim witch hunt.
 

hindsight2020

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The more critical issue with flying the B-52 in a trimmed state was the fact that the aircraft had a very short elevator chord (only 10%) connected to a THS that could easily overcome the available elevator control authority of the pilots' yokes if the trim was improperly used, or ran away on its own.

Correct. Our elevators are rather small, and our stab is huge, hence the importance of flying the thing within trim set adequately and trimming often in between configuration changes and/or attitude/airspeed changes.

As to the bolded above, it touches on the crux of the question the AIB and everybody is dancing around. The AIB couldn't conclusively determine the cause of the crash, so that document and $1.20 gets me a cup of coffee. I know this much, my job in peacetime, and my only interest on this matter, is to bring back my crew alive, not to appease political sensitivities. Ironically as it is, I won't comment further than that.
 

SpeedBird

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... The one before was brought down by an idiot and before that there have been the low level incident, the one where the aft tank blew up (not an H model).....

Fair enough Hindsight with regard to your response to my post. I just read your post and focused on your parenthetical statement (see quote excerpt above) and interpreted it differently and just wanted to set the record straight since I had first-hand experience with that mishap.

It sounds like you're doing your research and making sure you have the best information possible in order to perform your job better and keep your crewmembers as safe as possible when you all strap on that big beast to your backs.

While its' been almost 20 years since my last flight in the BUFF I can still remember having those same concerns as a young aircraft commander in what I thought was an old, tired weapons system at the time, but one that had a tremendous track record of accomplishment (and came with a -11 with over 35 changes to it that were often added because of the blood spilt by some unfortunate crewmember(s) that came before me and my peers).

My hat's off to you and everyone else who still carry on in flying and maintaining the B-52Hs today and which are fast approaching 50 years of age.

SB
 
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