Broken wing

No, the Lockheed Electra (turboprop, Allison engines) started falling out of
the skies shortly after their introduction. I believe the first one was
over Wink, TX and there were a couple more shortly thereafter. All sorts of
goofy reasons were tossed around, all the way from wrong rivet sizes to the
biffy leaking effluent onto the spar. The root cause was a peculiar
vibration of the engines called "whirl mode". THe fix was neither trivial
nor inexpensive. We had four of them at PSA and those damned things just
would NOT quit on you. They were also the easiest to work on transport
class aircraft I ever encountered.

Jim


"George Patterson" wrote in message
news:U7Jqf.50934$CL.50059@trnddc04...
Stubby wrote:
Way back, I believe the first jet passenger jet was the Lockheed Electra.
The plane mysteriously fell out of the air and very thorough search for a
cause was instituted.

Sounds like you're confusing it with the DeHaviland Comet. The cause was
eventually determined to be the rapid formation of stress cracks around
the corners of the rectangular cabin windows.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

"Jim Macklin" wrote in message
news:jsJqf.30375$QW2.4649@dukeread08...
They also used a high pressure sea level cabin,

I had never heard that. How did you dear about that?

I would imagine that a higher cabin would have slowed the cracks, but they
still would have formed.
--
Jim in NC

It was something I read many years ago, maybe during my A&P
course at Spartan, but I remember that the issues cited were
design of the windows and the quality of the joints and
rivets. The metal was an alloy that was prone to cracking,
but was strong. The extra pressure cause the metal to
expand and contract into the fatigue range of the alloy. It
all came together or should I have said apart on several
airplanes.


--
Merry Christmas
Have a Safe and Happy New Year
Live Long and Prosper
Jim Macklin
"Morgans" wrote in message
...
|
| "Jim Macklin" wrote
in message
| news:jsJqf.30375$QW2.4649@dukeread08...
| They also used a high pressure sea level cabin,
|
| I had never heard that. How did you dear about that?
|
| I would imagine that a higher cabin would have slowed the
cracks, but they
| still would have formed.
| --
| Jim in NC
|

Jim Macklin wrote:

It was something I read many years ago, maybe during my A&P
course at Spartan, but I remember that the issues cited were
design of the windows and the quality of the joints and
rivets. The metal was an alloy that was prone to cracking,
but was strong. The extra pressure cause the metal to
expand and contract into the fatigue range of the alloy. It
all came together or should I have said apart on several
airplanes.


Bit worse than that, in order:

The name - de Havilland aircraft had a habit of structural failure
The glue - Redux wasn't that good (note this was also a factor in the
convertible 737)
Fatigue - A mysterious new ailment for primitive people to blame the failure
of their "world beating" aircraft on. Strange that a novelist had written a
best seller on the subject 3 years earlier, stranger that Neville Shute had
worked for de Havilland 30 years before, had initially employed many of the
design staff after he founded Airspeed and presumably knew a lot that
wasn't didn't make the inquiry.



--

regards

jc

LEGAL - I don't believe what I wrote and neither should you. Sobriety and/or
sanity of the author is not guaranteed

EMAIL - and are not valid email
addresses. news2x at perentie is valid for a while.

"Jim Macklin" wrote in message
news:%xQqf.30408$QW2.23629@dukeread08...

It was something I read many years ago, maybe during my A&P
course at Spartan, but I remember that the issues cited were
design of the windows and the quality of the joints and
rivets. The metal was an alloy that was prone to cracking,
but was strong. The extra pressure cause the metal to
expand and contract into the fatigue range of the alloy. It
all came together or should I have said apart on several
airplanes.


The metal was quite thin. The skin of the 707 was about four times as thick
and Boeing employed ripstops as well.

Morgans wrote:

"Jim Macklin" wrote in message
news:jsJqf.30375$QW2.4649@dukeread08...
They also used a high pressure sea level cabin,

I had never heard that. How did you dear about that?

I would imagine that a higher cabin would have slowed the cracks, but they
still would have formed.
--
Jim in NC


From what I recall from my younger Engr days:

Low cycle fatigue of metals is affected by:

1) Cyclic loading
2) Tensile mean stress
3) Local stress exceeding the material's yield stress

The bigger the values, the faster the crack initiation
or crack propagation...

Howdy!

In article ,
RST Engineering wrote:
No, the Lockheed Electra (turboprop, Allison engines) started falling out of
the skies shortly after their introduction. I believe the first one was
over Wink, TX and there were a couple more shortly thereafter. All sorts of
goofy reasons were tossed around, all the way from wrong rivet sizes to the
biffy leaking effluent onto the spar. The root cause was a peculiar
vibration of the engines called "whirl mode". THe fix was neither trivial
nor inexpensive. We had four of them at PSA and those damned things just
would NOT quit on you. They were also the easiest to work on transport
class aircraft I ever encountered.

....where the engine wobbles in a conical sort of motion. IIRC, the
turboprops had enough horsepower to get into that sort of vibration where
the classic round engines didn't. New turf with extra wrinkles, as it were.

yours,
Michael


--
Michael and MJ Houghton | Herveus d'Ormonde and Megan O'Donnelly
| White Wolf and the Phoenix narrowwares
Bowie, MD, USA | http://whitewolfandphoenix.com
Proud member of the SCA Internet Whitewash Squad

Bob Moore wrote:

Matt Whiting wrote

Gee, Bob, you should know the difference between a turbine
engine used as a propjet from one used as a pure jet. :-)

Hey! Eastern Airlines called them "Prop Jets".

The airline marketing departments purposely blurred the definitions in the
1950s. American called Electras "Jet Powered Flagships". Braniff called
them "Jet Power Electras". I seem to remember one airline declaring that
they had an all-jet fleet when they phased out their last piston aircraft,
but still flew turboprops.