Re: Engine noise question

Date:         05 Dec 96 02:27:20 
From:         vkn@post.gsfc.nasa.gov (nkjjb )
Organization: NASA Goddard Space Flight Center -- Greenbelt, Maryland USA
References:   1
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Jeff To answer both posts

Turnaround Maintenence Usally Include Thru-Flight Inspection. This
involves Checking the Fluids- Hydrulic,  Engine oils, Fuel (a refuel base
on next destination and payload, You don't just top it off It would cost
money to fly the extra fuel around). Inspect the engine intakes and first
stage Compressor blades for impact damage. Check the landing gear tires
and brakes ( in case the landing was hard and damaged anything. Flaps and
Slats(leading edge flaps) for proper deployment and security (not falling
off) . A general "Walk Around" is performed Looking for visable damage.
Most of these Tasks can be performed while the passengers are exiting and
the cabin is being restocked.

The sound you here as the jet approaches is the harmonic vibration of the
compressor blades spinning, much like an electric fan produces its own
tone while spinning (much lower frequency and volume). As the jet passing
you here the engine thrust.  This is produced from the combustion of the
compressed fuel -air mixture igniting in the cumbustion chamber passing
thru the turbine blade and exiting the exhust nozzle. during take-off and
climb to altitude you might notice a sharper crackle or popping of the
exhust sound, this is caused by the fact that the exhust gases are leaving
the engine at super-sonic speeds and the miniture sonic booms produce by
these exhust gases

--
NASA/Goddard Space Flight Center

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