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Recollections
1.
Alex Dow
Fife, Scotland |
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Alex Dow reply to Alastair Adams'
Recollections 15 about steam catapults.
Alex wrote: |
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Steam Catapults
"If you take a look at this
Navy
History site, you'll see that Steam
Catapults were basically a post-WW2 innovation, involving Brown
Brothers, etc."
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Steam Catapults
"Alistair's
father was probably working on the earlier Hydraulic Catapults; and
I think that there were not many of those in the Flight Deck.
He could also be confused with the short-ramp
variety used from WW1 and eventually epitomized by the use with
Hurricats - Hurricanes modified for ramp
take-off from the Merchant Aircraft
Carriers, where there was only one plane aboard, one take-off ramp
and NO Landing Deck. So, the
plane was normally ditched unless close to land."
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Brown Brothers
"Brown
Brothers had a model of the earlier inter-war version, complete with
a model Walrus Amphibian. I helped to demonstrate this and their
Hydraulic Steering Gear at the 1949 Parish Industries Exhibition at
McDonald Road Church."
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Prop-driven Aircraft
"Prop-driven
aircraft create a fair amount of lift when stationary in windless
conditions, just by the air flow created by the prop/s over the
wings.
If you ever flew in such a plane, you
would notice that even on a calm day, the
aircraft would lift and fall in its own airstream, when
revving up at the start of the runway. In part it is also the reason
for the ground crew member sitting on the
tail plane when taxiing over the airfield,
or clinging on to the wing tips."
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Jet Aircraft
"The air
streams from jet aircraft go nowhere near the wings, whether inboard
like the Comet or outboard like most modern airliners. Hence it was
the introduction of pure jets to naval flying that forced the
development of the steam catapult."
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Hydraulic Catapults
"The earlier
hydraulic versions required totally separate plumbing, compressors,
hydraulic reservoirs and had limited travel from the need to fully
contain the pressurised hydraulic oil, to minimise/avoid the loss of
the oil, particularly on to the deck and deck crew. It also took
some time to 're-arm'
the system for the next take-off, one plane at a time.
The oil, like
most fluids, is virtually incompressible,
so that you are dependent upon a small
pressure vessel to achieve the drive."
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Steam Catapults
"The later
steam catapult could be plumbed in to the existing large capacity
on-board boilers, using superheated water. When this is released in
to the launch piston, it expands up to 800 times the volume, so
maintaining a positiverive to the piston
and aircraft, through the full stroke length.
Any losses from the system rapidly pass
through the water vapour phase to water, cooling simultaneously, so
much less of a menace on the deck and for the deck crew.
Some of the USA Nuclear-powered
Carriers with four catapults can launch an aircraft every 20
seconds. The superheated water comes from the cooling system for the
nuclear reactors."
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Alex Dow, Fife, Scotland: May 23,
2011 |