Re: 737 musings

From:         vac@air16.larc.nasa.gov (Victor A. Carreno)
Organization: NASA Langley Research Center
Date:         14 Oct 94 02:23:34 
References:   1 2 3
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In article <airliners.1994.1609@ohare.Chicago.COM>, kls@ohare.Chicago.COM (Karl Swartz) writes:
|> 
|> On the other hand, the 737-300 (-400 and -500 too) have a completely
|> different pylon design and I've never heard of them losing an engine.
|> 
|> Finally, several instances of 727s losing #1 or #3 come to mind -- AA
|> from DFW to SAN near the AZ/NM border and NW over northern Florida.
|> In both cases, the foreign object damage (FOD) to the engine caused
|> the separation -- the pylon design prefers detachment of a suddenly
|> unbalanced engine to destruction of the fuselage.
|> 
I thought this will be of interest:
The Washington Post 18JUN93
Breakaway Jet Engine Abandoned
Boeing Announces Design Change in 747

The Boeing Co., abandoning a 25-year design theory that letting engines
break free under severe stress is safer, yesterday announced major wing
modifications to prevent engines from falling off the 747 jumbo jet in
flight. 
The changes, which would take four to five years to implement on the
948-plane fleet, are the latest step in an engineering investigation
prompted by the crash last Oct. 4 of an El Al cargo jet into an apartment
complex in Amsterdam.
[suff deleted]
The company essentially acknowledged that it had built the world's most
popular jumbo jet for 25 years under the misconception that the planes
could always fly after losing engines and that having an engine break away
after a catastrophic failure sometimes was safer.
"We thought an engine could come off safely," said Dick Johnson, Boeing's
director of engineering for the company's 747/767 program. "We've had two
accidents since that proved that to be wrong."
[more stuff deleted]
The modifications follow two paths: strengthening the entire strut assembly
including fuse pins, and adding a redundant backup structure that could
hold the engine to the wing even if the new fuse pins fail.
"We've decided that safe separation isn't the way to go," Johnson said. "So
we are going to make sure they don't fall off."
Johnson said the new design essentially is the same one used in the newer
Boeing 767 and 757 twin-jets.
Johnson said the new design would allow the engine to break free if it
comes in contact with the ground in a belly landing.
Fuse pins now are to be made of stainless steel to prevent corrosion and
have a simple straight-bore hole through the middle rather than internal
notches. A Cray supercomputer determined that the nothches would cause the
pins to undergo stress eight to 10 times greater than expected under load.
[end deleted]