Limiting factor for the Six was the EGT. In the left(?) MWW it had what
was called a "635 clock" that tracked both the consecutive and
cumulative number of seconds that the engine operated above 635 degrees
F in EGT. Don't remember the T.O. limits anymore, but if either counter
read too high, then the engine was pulled and sent into the shop for
teardown and inspection.

The F-111 (I can only speak for the E's) had a Total Temperature gauge
in the upper left quadrant of the pilot's front instrument panel. It
measured the temperature of the windscreen and counted down the number
of seconds (Sec To Go) before it would lose structural integrity. The
face of the gauge had two tick marks on it: the first one started the
clock; the second one basically said "Too late, Charley - I'm melting
right now." I don't recall the actual temperature limits, but they
weren't anywhere near as high as the legends suggest. IIRC the first
tick mark was around 200 degrees F and the second around 240. I think
that the total time allowed at the lower limit was on the order of five
minutes - much less as the upper limit was approached.

I've got an old GD engineering drawing in a box around here somewhere
that shows the instrument panels in 1/4 scale with all of the gauge face
marks on them. If I can find the thing, I'll update this post. In one of
the flights that I took we hit 2.01M at 43k ft and the windscreen felt
warm enough on my bare hand to get a cup of coffee to a drinkable
temperature.

Vygg

John S. Shinal wrote:

(WaltBJ) wrote:

I also had a long phone conversation with an old squadron mate. He
mentioned he used to FCF F111s - and had one out to 2.7 in a shallow
dive from 50 grand. And I believe him - know him well. Don't bother
telling me it's past the red line; that's just a mark on a gauge.


I read a diary of a flight (Airpower ?) that said the F-111
had a timer that assisted with avoiding over-temperature on the
canopy, did older aircraft like the F-106 have anything similar, or
was it all seat-of-the-pants ?



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