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"My question is: could the output of
the two pumps combine and overwhelm the return line causing pressure and thus
fuel flow to go out of limits?"
Just to restate the report of the Bonanza crash, with a
TSIO-520 engine. A Beech test pilot found that taking off with the boost
pump on high resulted in a smooth running engine, but a perceptible loss of
power. He flew above the airport at full power at a
safe altitude and with the boost pump on high. He slowly reduced manifold
pressure. The engine became rough at 35" and suffered a complete loss of
power at 31". Moving the throttle back in did not restart the engine and
he recovered by turning off the boost pump. The NTSB report said that the
engine would quit at 24" manifold pressure with the boost pump on
high.
The pilots who have recently reported their findings on the
LML support the first half of the above claim, that high boost at full power
does not kill the engine. But those findings don't contradict the second
part of the claim, that high boost will kill the engine below either 31" MAP
(Beech test pilot) or 24" (NTSB). I'm not planning to test it in my
airplane; I'll stay on the ground and have a beer
instead.
Source: Flying magazine's Aftermath
article September 2004.
Best,
Dennis Johnson
Legacy
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