Minimum and maximum speed for 9G in A-A configuration inF16A

Operating an F-16 on the ground or in the air - from the engine start sequence, over replacing a wing, to aerial refueling procedures
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johnwill

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Unread post24 Oct 2016, 21:03

I don't doubt your statements. Possibly, the tanks we used in the original flight test weren't gauged, but that capability was added for production tanks.
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basher54321

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Unread post25 Oct 2016, 12:48

johnwill wrote: The best way to try is to start from max mach at 50k and split-S down to 40k hoping to get 9g, 2.0, and 40k at the same time.


So it couldn't be done as a near level turn but I like this idea - accelerate to maybe over M2.0 in a low G split S then pull for 9G between 30 - 40Kft briefly 8) - I suppose you might then need to throttle back to idle to stop over speeding the engine and deploy the brakes to not end up in another article on not stretching the limits. (PS don't try this at home 35_aoa :P )
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sferrin

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Unread post25 Oct 2016, 13:13

basher54321 wrote:
johnwill wrote: The best way to try is to start from max mach at 50k and split-S down to 40k hoping to get 9g, 2.0, and 40k at the same time.


So it couldn't be done as a near level turn but I like this idea - accelerate to maybe over M2.0 in a low G split S then pull for 9G between 30 - 40Kft briefly 8) - I suppose you might then need to throttle back to idle to stop over speeding the engine and deploy the brakes to not end up in another article on not stretching the limits. (PS don't try this at home 35_aoa :P )


As "jbgator" said a few posts ago:

"I have tried it on FCF, not at Mach 2 but up close to it. First, the idea of doing 9G at Mach 2 is unobtainable because as soon as you start to apply some back pressure to turn you are no longer at Mach 2. It takes a long time, lots of airspace, and gas to get to Mach 2. I only tried to get there once on an FCF and from then on I only usually went out to about 1.95 or so. Usually you do the 9G limiter test later in the flight at lower altitude but I once tried to do it at 40K at the end of the Mach run so it was close to Mach 2. As I posted earlier the jet is very sluggish at that speed and the G-onset was quite unimpressive compared to a limiter pull at 20K and 450+ KCAS where that test point is usually performed. The jet did not get to 9G until it went subsonic, which happened fairly quickly as I recall. I do not recall what G it peaked at while supersonic but it wasn't 9."
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sprstdlyscottsmn

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Unread post25 Oct 2016, 13:22

The manual reflects that as well. At 40k max G available is under 9 for most the envelope, front and back ends.
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basher54321

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Unread post25 Oct 2016, 13:31

sferrin wrote:
As "jbgator" said a few posts ago:

As I posted earlier the jet is very sluggish at that speed and the G-onset was quite unimpressive compared to a limiter pull at 20K and 450+ KCAS where that test point is usually performed. The jet did not get to 9G until it went subsonic, which happened fairly quickly as I recall. I do not recall what G it peaked at while supersonic but it wasn't 9."


Yes - but this to me reads near (or near as) level turn. Being in a dive (nose at the deck) as John suggested at over M2 your speed wont bleed off in the same manner - though this seems a lot more risky to me based on previous disasters considering it has pretty much no value.
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jbgator

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Unread post25 Oct 2016, 20:04

As I recall it was a bit of a slice back. I also took it out of AB at the point at which I realized it wasn't going to get to 9G which increased the rate of deceleration. I would defer to the aerodynamically smart folks to decide why but I think the rarified air, the increased static stability above the mach, and the high negative Ps at that altitude makes it unlikely. But again I say, WHOGAS? Why would you be running away, or chasing someone down, at Mach 2 (which requires you to be high to achieve it) and suddenly need 9G? As to the whole "haven't been there so why not try it?" I refer back to the old/bold pilot adage. The standard line was to watch out when someone said "hold my beer..." and "watch this...." I certainly took interest in pushing the envelope as a youngster, especially on FCFs when you were alone and free to press, but I quickly realized there were no trophies or long term recognition for those who exceeded the limits and more likely there was some bad stuff witness the guy who exceeded the engine speed limits, shredding the motor, at Eglin and ejected above the Mach, severely injured by flailing but died from drowning unable to deploy LPUs with broken arms. I remember meeting General Fogelman (not for the first time but first as CSAF) at Daytona 500 for flyby we did when he commented that in cases of displaying your a$$, the best you could do was break even....
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basher54321

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Unread post25 Oct 2016, 21:27

jbgator wrote:As I recall it was a bit of a slice back. I also took it out of AB at the point at which I realized it wasn't going to get to 9G which increased the rate of deceleration. I would defer to the aerodynamically smart folks to decide why but I think the rarified air, the increased static stability above the mach, and the high negative Ps at that altitude makes it unlikely.



Thanks JB - would defer to others also. To me the charts make out you would be hitting the AoA limiter before you could get to 9G at 40,000ft / M2.0 in a level turn. A slice should be better than a level turn, but starting nose level wonder if it still generates a significant AoA to hit the limiter there as well.


WHOGAS? - probably someone comparing behaviour to a simulator.
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sprstdlyscottsmn

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Unread post26 Oct 2016, 03:53

So I'm looking at the GE-129 chart no. Even clean and at 22,000lb the conditions for FL400 and 2.0M show by 3G the plane is at -300fps Ps. Full aft stick indicates less than 7.5G and -2400fps Ps. So as jbgator says from experience, it's not going to get to 9G and you will slow WAY down in the process.
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Unread post26 Oct 2016, 09:50

sprstdlyscottsmn wrote:So I'm looking at the GE-129 chart no. Even clean and at 22,000lb the conditions for FL400 and 2.0M show by 3G the plane is at -300fps Ps. Full aft stick indicates less than 7.5G and -2400fps Ps. So as jbgator says from experience, it's not going to get to 9G and you will slow WAY down in the process.


Thanks - appreciate that. I didn't think a slice was a constant altitude turn (should be nose down n degrees?) and I can see the charts show over -2800 fps for 9G at M2.0 at a constant 35Kft (if you start the initial pull there) so was more interested (for the hell of it 8) ) in whether it is being stopped from hitting 9G (for a second near say M1.9 ) at 40,000ft by just the AoA limiter at the initial pull and not just the energy loss rate with a say 30-45 degree nose down attitude. (but don't spend any time on it :D )
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