Sustaining High Gs at High Airspeeds

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by delta2014 » 10 Dec 2018, 16:18

Is the reason why the F-16 and other jet fighters can sustain high Gs at high airspeeds, but cannot sustain those same high Gs at lower airspeeds because:

1) AOA is lower at higher airspeeds

2) A jet fighter produces higher thrust at high airspeeds and lower thrust at low airspeeds

Is it because of both?

Thanks,

Delta


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by saberrider » 10 Dec 2018, 16:42

Surfaces areas and deflection is small but enough for optimum ALTITUDE AND AIR DENSITY . So at high alt you need more speed to get max. performance BUT MAYBE NOT 9 G JUST LOWER ONES . With FBW systems and negative stability of the aircraft the deflection of the stab. for 9 G IS NOT THE SAME FOR THE ENTIRE SPECTRUM OF SPEEDS AND ALTITUDES . 9G is sometimes obtained at 15 AOA and 450 KNOTS , but over 1. 4 Mach the 9 G is at 6 AOA.and lower alt. were air density is bigger .But there is more , CONTROL SURFACES DON'T STOP IN PLACE AFTER GETTING 15 AOA AND an max.9 G BECAUSE aircraft will overshoot 9 G , SO THEY MUST DUMP THE INITIAL DEFLECTION IN A SECOND TO A LOWER ANGLE OF DEFLECTION AND THEN COME BACK maybe with more deflection IF NEEDED BECAUSE OF LOST OF THE SPEED AT HIGHER G NUMBER .THESE WAY YOU MAINTAIN A LOWER INDUCED DRAG and keeping allowed G MORE TIME THEN NO FLY BY WIRE AIRPLANES .At slow speed F16 STABILATOR go down until mechanical stop (25 DEGREES),FOR 25 AOA then go up TO THE NEGATIVE 3 DEGREES DEFLECTION to not overshoot 23 OR 25 AOA and only 1 G.THESE WAY FBW WORKS ,in my understanding .Hope this is easy to understand for you .


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by saberrider » 24 Apr 2019, 10:03

In my opinion is number 1.



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