The Lockheed SR-71 Blackbird
by Micro Brat
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The Lockheed SR-71 Blackbird
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Perhaps one of the most ellegant aircraft of recent times is the
Lockheed SR- 71A Blackbird. It's unique shape means that it is easily
identifiable, if it is seen that is. With altitude records of 85,000
ft, and a top speed of Mach 3.17 means that people rarely have the
chance to see it.
It should be noted however that the Blackbird is far from a new plane,
the initial contract was awarded to Lockheed in 1954, as a successor
to the ageing U-2. The project was financed greater after the need
for a replacement was emphasized by the shooting down of Francis Gary
Powers on Mayday 1960 over central Russia. The design team headed by
Kelly Johnson knew that conventional aluminium couldn't be used for
this plane as it wouldn't withstand the stresses and temperatures
envolved with sustained Mach 3 flight. Indeed over the engine fins,
the temperature can rise to an amazing 1050 degrees Fahrenheit. It
was decided to use titanium, which at the time was very difficult to
extract and very expensive. However this didn't discourage the design
team. Firstly the plane was designed as an interceptor, but on
further design work it was found improbable to carry weapons with the
amount of fuel required for long fast flights. Power is supplied to
the Blackbird by the innovative J-58 Pratt & Whitney continous bleed
turbojet engines. These in themselves were an engineering feat.
Specially designed nacelles and highly complex fuel system lead to
these engines developing an incredible 32,500 lbs thrust with full
afterburn, which is used on the majority of flights. However this
doesn't come cheap and the Blackbird eats 8,000 gallons an hour of
special JP-7 high temperature fuel. The Blackbird is effectively a
flying fuel tank with the most sophisticated spying computers in
existence. As it flys by at Mach 3+ it certainly isn't difficult to
spot the Blackbird.
On account of its capabilities the Blackbird is said to have been used
on many of the worlds flare points including Greek/Turkish conflict,
and Vietnam. These planes will continue to prove very useful to the
U.S.A.F, even if it is just in its capacity as a showpiece. It
doesn't blend in with the rest at airshows. Certainly the Blackbird
is a technical achievement perhaps unmatched in military aircraft
since the Spitfire. Also it is relatively hidden to enemy radar, at
its top speed of Mach 3.17, it only occasionally occurs on a radar
screen as a fast moving dot, or maybe it is identified by the
occasional sonic boom. However with the introduction of infra-red
radar and very high speed missiles, the Blackbird is under greater
threat, but these systems are so expensive and relatively useless that
the Blackbird will certainly be around for a few years to come. The
'stealth' project in development at the moment is unlikely to knock
the SR- 71 out of service in the near future, because the technology
it needs to use is still somewhat in the future and completely
untested.
Some of the more interesting facts about the plane have occured from
the Mach 3 flight that it endures:
The pilots are all volunteers, and have to wear space suits similar to
those worn by space shuttle crews and valued at around $100,000. They
are internally refrigerated. The length of the Blackbird increases by
1 foot when in flight at Mach 3+.
The engines are removed and cleaned after every 200 hours flying. The
fuel tanks are cleaned and re-sealed after 200 hours, and despite this
they still leak when they are cold. The oil used to lubricate the
engine, is solid for a good deal of the early flight, and only becomes
liquid after the temperature reaches 84 F. Also the cockpit window
gets so hot, that the crew can heat tubes of food against the window
by holding it there, the temperature can reach 400 F. The tyres are
inflated to 400 psi with nitrogen to avoid bursting due to the heat
changes. While at sustained Mach 3 flight, the end of the fuesalage
glows red hot continuously.
The Blackbirds operate on occasion from Kadena, Okinawa, U.S.A and
Mildenhall, Suffolk, England, and they have an individual hangar at
Beale Airforce base in California, where they are all based. The
number of Blackbirds isn't known exactly, but is thought to be about
24. This'll certainly give a new meaning to the saying:
'Four and twenty Blackbirds.......'
An insight into one of the wonders of Aerospace, written by Micro Brat© 1987.
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