Sunday, August 30, 2009

Now that's a big "Oops!"

An e-mail was circulated today to a list of which I'm a member. Dan B. sent us a Powerpoint presentation of a rather nasty accident involving a US Air Force KC-135 Stratotanker aircraft. It was so graphic that I thought other aviation enthusiasts might enjoy seeing it too.

The indented text below was included with the photographs in the presentation. Click each picture for a larger view.

This is an example of what happens when we do not pay attention to detail, and do not follow instructions and checklists!

A KC-135 aircraft was being pressurized at ground level. The outflow valves which are used to regulate the pressure of the aircraft were capped off during a 5 year overhaul and never opened back up. The post-investigation revealed that a civilian depot technician, who "had always done it that way", was using a homemade gauge, and no procedure.

The technician's gauge didn't even have a max 'peg' for the needle, and so it was no surprise he missed it when the needle went around the gauge for the first time. As the technician continued to pressurize the aircraft, and as the needle was on its second trip around the gauge, the aircraft went 'boom' - the rear hatch was blown over 70 yards away, behind a blast fence!

An incident like this is never funny and is further regrettable when we consider that this mistake is one that we (the taxpayers) will end up paying for. Fortunately, no one was reported as being injured.

This was a good 'Lessons Learned' for making sure we have trained people, who have the right tools, and who are following detailed procedures. And it should serve as a reminder that just because you've always done it that way, it does not make it the 'right' way!

Now that's an impressive amount of damage! I hadn't realized that explosive decompression could occur like that at ground level . . . but I guess the blocked outflow valves, referred to above, must have allowed the pressure to build up far past the point at which it would normally have been safely vented.

I guess that's one KC-135 that won't be flying again!



Thomas A said...

I worked with those civilian techs (US Gov employees, hard working types) a year or so after this happened (this was years ago) and they didn't want to talk about it.....

And the airplane was certainly not in modification for 5 years! The whole program to work on all of the 135s might have taken 5 years.

Anonymous said...

i work at that depot, they made supervisors out of at least 1 of the people responsable for the accident, believe it or not.

Anonymous said...

Outflow value has to be capped for the pressurization check. Running engines to do the check was the mistake, especially since they were the new engines, not J57s.
Tech order libraries were consolidated years before to save money, a major made General for saving money, the lack of tech order available for all is a small part how saving money comes back to bit you. Normal pressure check uses an air-cart, not engines, and the outflow values have to be capped to do the check, that is correct tech order, the engines running are not normal for the check; that was the short cut, running engines.

James said...

Were they running cabin press or proof press. I used to run proof press on them at Pemco Aeroplex in Birmingham Alabama. We had a MO to go by which required a insp to stamp off that outflow valves were reconnected.