Pressure testing gone bad

a@aa

Had forgotten the comets (either age or 'booze berries). Tnx.

Big John


21 Nov 2003 13:51:50 -0800, wrote:

In article , Big John says...

Fred

One more.

Scuba tanks have to be pressure tested every few years. This is done
in a tank of water in case they fail.

So under water testing is a common thing (except for KC-135's BG)

Big John

It's been done. Remember the Comets that blew up back in the 50's? This is the
way they figured out the failure mode...

"The Ministry of Civil Aviation decided upon a unique test to find out. They
built a tank large enough to hold one of the grounded Comets. The wings
protruded from water-tight slots in the sides of the tank. Then the tank and
cabin were flooded with water. The water pressure inside the cabin would be
raised to eight and a quarter pounds per square inch to simulate the pressure
encountered by a Comet at 35,000 feet. It would be held there for three minutes
and then lowered while the wings were moved up and down by hydraulic jacks. The
hydraulic jacks would simulate the flexing that naturally occurs in aircraft
wings during flight. This process continued non-stop, 24 hours a day. This
torture test continued until the cabin in the tank had been subjected to the
stresses equivalent to 9,000 hours of actual flying. Suddenly, the pressure
dropped. The water was drained and the fuselage examined. The investigators were
horrified to find a split in the fuselage. It began with a small fracture in the
corner of an escape hatch window and extended for eight feet. Metal fatigue! Had
the Comet not been under water, the cabin would have exploded like a bomb.