Engine power and RPM

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Gums

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Unread post25 Aug 2008, 22:37

Salute!

1) The original Viper with the F100 motor could pull 9 gees at about 360 IAS. At low altitude, it could maintain that 9 gees using full AB until you ran outta gas!!!

2) A good way to see a rough number for turn performance is radius = velocity squared/gee. All in feet or feet per second or feet per second squared. Also assume bank angle is almost 90 degrees.

So Viper could turn with a 1300 foot radius at 360 knots pulling 9 gees. Neat, huh? To maintain level flight, bank angle had to be less than 90 deg, so actual turn radius was greater than 1300 feet. The equation assumes gee toward the center of the turn.

At high altitude, the true speed was higher for 360 indicated, but you could pull 9 gees right off the bat. Turn radius was greater and motor wasn't cranking out as many thrusties. So you couldn't maintain the bat turn very long. I did see 9 gees for a full 360 turn one day at about 15,000 feet (Joe Baggodonuts student studly was built like a NFL linebacker and after one turn I suggested he climb versus maintaining the high gee turn while level.)

The Allison TF-41 in the A-7D had a TOP gauge (turbine outlet pressure). Supposedly, it was a direct indication of thrust. Sucker was calibrated in inches of mercury or PSI or something, heh heh. Biggest thing we used it for was noting that TOP increased an inch or two when we turned off the air conditioning before rolling.

later,

Gums sends ....

P.S. Listen to TEG. We had a pilot exceed limits in a dive and his motor did, in fact, come unglued at a bit over 800 KIAS. He paid the price, as did his wife and family.
Gums
Viper pilot '79
"God in your guts, good men at your back, wings that stay on - and Tally Ho!"
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oldsstroker

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Unread post20 Mar 2017, 03:09

Gums wrote:Salute!



The Allison TF-41 in the A-7D had a TOP gauge (turbine outlet pressure). Supposedly, it was a direct indication of thrust. Sucker was calibrated in inches of mercury or PSI or something, heh heh. Biggest thing we used it for was noting that TOP increased an inch or two when we turned off the air conditioning before rolling.

later,

Gums sends ....



About the first thing an A-7 IP learned when chasing a student who was using MIL power for takeoff, was turning off the A/C to have a little power advantage. No Family model back then. Murphy's Law says the student got the bird with the most power.

Yeah, it was inches of mercury. Sometimes an extra inch is very useful!

Cheers.
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