SUIT INLET TEMPERATURES IN DESCENT

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP75B00285R000400130020-2
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 2
• Document Creation Date: December 12, 2016
• Document Release Date: February 28, 2002
• Sequence Number: 20
• Publication Date: April 6, 1966
• Content Type: MEMO

Approved For Rase 2002/06/24: CIA-RDP75B00285MOO0400130020-2
O5A - 1666- 66
6 April 1966
To: John Parangosky
Subject: SUIT INLET TEMPERATURES IN DESCENT
c~~ 2 rza d V
We note repeated statements that low remaining fuel at end of cruise
would be a flight safety hazard due to causing the pilot to overheat in
descent. This theory disregards all Flight Test evidence to the con-
trary. We believe it is probably based on our own early claims that
we would have to descend at full idle power, which as you know is
wrong.
If descent actually was made at idle power, the relation to suit inlet
temperatures would be as follows-
A. Extremely low bleed pressure at engine idle causes
loss in expansion turbine's cooling ability, regardless
of heat sink temperature.
B. Engine fuel flow is so small compared to heat sink
flow that smart valve would be returning all hot fuel
to tank during the descent.
C. This continuous mass return would heat up tank fuel,
the rise being more with a low remaining fuel load.
D. Total result of full idle descent would therefore be
high cockpit and suit inlet temperatures; probably
uncomfortable.
Instead of the above obsolete prediction, we see typically in actual
Flight Test data enough engine fuel flow to maintain zero tank return
during descent, except during first two to three minutes of deceleration.
Even there, only part of the hot fuel returns to tank, with minor affect
regardless of tank load. The remainder passes thru smart valve and
causes temporary temperature rise, 50?F. typical, at the heat sink
loop inlet only. Earlier, with eroded turbines, some of this always
appeared as temporary suit inlet rise; with good turbines - zero effect
is seen. As for engine bleed pressure to the expansion turb nes, the
data shows fairly high values during most descents, and never the
extreme lows of full idle until seconds before touchdown.
Approved For Release 2002/06/24: CIA-RDP75B00285R000400130020-2
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Approved For Rase 2002/06/24: CIA-RDP75B00285RN0400130020-2
6 April 1966
Typical suit inlet temperatures in descent are seen to be on the order
of 200 to 30?F. , except that below 30, 000 feet on the final descent a
rise occurs to final 45?F. at touchdown. The latter shift has no
relation to heat sink, but is instead the effect of low altitude cockpit
pressure on expansion turbine performance. Best cooling can be
obtained at any point in descent by maintaining highest possible engine
power at all times, regardless of heat sink conditions.
Sensed increase in discomfort during long cruise has also been related
by the pilots to decreasing fuel load. This is possibly an offshoot of
the early descent theory defined above, which is in no way applicable
to cruise. The real reason for discomfort increasing toward the end of
a long cruise is the greater heat soak of windows, suit and. faceplate
with elapsed time. The fact. that fuel load happens to be decreasing
during the same elapsed time does not make it responsible for cockpit
radiation problems.
Witness Silver Javelin Flight 130, SIN 129, where with 6, 000 lbs. fuel
remaining at end of 1. 25 hour high speed cruise the cockpit discharge
was still only 50?F., yet pilot comfort level was acceptable on y
because of special window radiation shields and glove covers.
Best regards,
25X1A
Approved For Release 2002/06/24: CIA-RDP75B00285R000400130020-2