Structural failure due to harmonic vibration

On Thu, 8 Nov 2007 11:01:14 -0600, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote:

Steven P. McNicoll wrote:
I think most people would agree with you. I'd say a "trans-
continental" flight that started in Spokane and proceeded east failed
to transit about 400 miles worth of continent.

Would you count KSEA to KJFK as Trans-continental? If so the difference in
the distance of a great circle route flight would only be 193 miles.

That 192 miles includes a major mountain range (the Cascades)....

Ron Wanttaja

Jay Honeck wrote in
oups.com:

A coast-to-coast flight originating from Spokane? Spokane is in
eastern Washington, not far from the Idaho border. Must be nearly
400 miles from the Pacific coast.

My mistake. The author called the flight "trans-continental" and
"across America" -- which my brain translated into "coast-to-coast"
for some reason...

Oven cleaner is my bet


Bertie

Jay

After the two crashes they found the problem and fixed it but then
they didn't sell good to airlines due to crash history.

Navy bought a large number (with MAD gear) after fix, that are now
configured to the P-3C Orion (ASW) configuration and many P-3's were
sold around the world in ASW confguration. Navy is still using them
while waiting for a new bird. There is a request out to industry for a
new bird???

Big John

****************************************


On Thu, 08 Nov 2007 06:09:52 -0800, Jay Honeck
wrote:

I've just finished reading the tale of the first round trip coast-to-
coast flight (which was accomplished by mid-air refueling,
occasionally from milk cans) from Spokane, WA to the east coast and
back, way back in 1929. They flew a distance of 10,000 miles (they
circled over airports whilst refueling) without landing. A
fascinating story, printed in a terrific magazine, "Aviation History".

One of the pilots, Nick Mamer, went on to a career with Northwest Air
Lines. The author of the article states that he was killed in 1938
flying a Lockheed 14 Super Electra over Montana when the plane crashed
after suffering structural failure due to harmonic vibration. All
passengers and crew were killed.

This is something I've never heard much about. I understand harmonic
vibration can destroy any structure, given enough time and amplitude
-- but wouldn't a pilot be aware of such an event occurring in
flight? I picture something similar to flying a twin without synching
the props -- the noise and vibration will just about drive you crazy.

I don't have any further information on this crash, so I suppose the
vibration could have destroyed the engine mounts, causing the engines
to depart the airframe. This would probably be impossible to detect
from the cockpit before disaster struck.

Does anyone have any more information on this phenomenon, and this
crash specifically? Also, are there any Super Electras still flying
and, if so, how did they solve this problem?

Big John wrote:

Jay

After the two crashes they found the problem and fixed it but then
they didn't sell good to airlines due to crash history.

Navy bought a large number (with MAD gear) after fix, that are now
configured to the P-3C Orion (ASW) configuration and many P-3's were
sold around the world in ASW confguration. Navy is still using them
while waiting for a new bird. There is a request out to industry for a
new bird???

That was a different airplane, and a different problem. The one Jay is
referring to were the orignal Electras, similar to what Amelia Earhart
flew. The Northwest flight was an L-14 Super Electra, a larger, more
powerful version of Amelia's L-10E.

http://en.wikipedia.org/wiki/Northwe...lines_Flight_2

What you are describing are the L-188 accidents in 1959/60. The were a
result of what was called the "whirl mode" failure.

The aircraft would perhaps have a hard landing, which would weaken or
break one of the struts in an engine mount. The engine would then be
able to move around slightly on the remaining mounts. When the aircraft
subsequently encountered moderate turbulence, the mounts would not be
able to restrain the engine from acting like a gyroscope, resulting in
the hub of the prop rotating in a circle. In one of the accidents, it
looked like the engine had moved up to 35 degrees out of line.

Unfortunately, when the crew reduced engine power because of the onset of
whirl mode, the frequency of the whirl mode would reduce, and eventually
would match that of the wing. The sympathetic vibration would grow in
magnitude until the wing structure failed.

Big John wrote in
:

Jay

After the two crashes they found the problem and fixed it but then
they didn't sell good to airlines due to crash history.

Navy bought a large number (with MAD gear) after fix, that are now
configured to the P-3C Orion (ASW) configuration and many P-3's were
sold around the world in ASW confguration. Navy is still using them
while waiting for a new bird. There is a request out to industry for a
new bird???


Hey, why get a new airplane when you can just sit in a lawn chair with your
Wii and hunt virtual subs?

The Orion name was another they re-used, of course.
Why they did this is beyond me, it's not like they were ever going to run
out of constellations. Pity they never made a Cygnus, always been my
favorite.



Bertie

Bertie the Bunyip wrote:

Why they did this is beyond me, it's not like they were ever going to run
out of constellations.

Lockheed ran out of Constellations in 1958. :-))))))


John Galban=====N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums...ation/200711/1

"JGalban via AviationKB.com" u32749@uwe wrote in
news:7aec9d9cbf3fa@uwe:

Bertie the Bunyip wrote:

Why they did this is beyond me, it's not like they were ever going to
run out of constellations.

Lockheed ran out of Constellations in 1958. :-))))))


Groan!



Bertie

Jay Honeck wrote:
I've just finished reading the tale of the first round trip coast-to-
coast flight (which was accomplished by mid-air refueling,
occasionally from milk cans) from Spokane, WA to the east coast and
back, way back in 1929. They flew a distance of 10,000 miles (they
circled over airports whilst refueling) without landing. A
fascinating story, printed in a terrific magazine, "Aviation History".

One of the pilots, Nick Mamer, went on to a career with Northwest Air
Lines. The author of the article states that he was killed in 1938
flying a Lockheed 14 Super Electra over Montana when the plane crashed
after suffering structural failure due to harmonic vibration. All
passengers and crew were killed.

This is something I've never heard much about. I understand harmonic
vibration can destroy any structure, given enough time and amplitude
-- but wouldn't a pilot be aware of such an event occurring in
flight?

If the Q is high enough, the amplitude of the vibration might ramp very
quickly to failure. Think control surface flutter. There isn't always
time to react.

Matt