F-15 crash and split afterburner use

Cold war, Korea, Vietnam, and Desert Storm - up to and including for example the A-10, F-15, Mirage 200, MiG-29, and F-18.
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eagle3000

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Unread post15 Mar 2020, 00:52

Nicely illustrated in this video: https://vimeo.com/40935850 (No longer on youtube it seems).
At around the 7:30 mark.
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outlaw162

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Unread post15 Mar 2020, 02:20

Who would begrudge an experienced, college-educated fighter pilot a bit of spontaneous creativity?

I've seen folks pull stab aug circuit breakers for 'expanded' control authority, now there's an idea....

depart the aircraft intentionally, now there's an idea....

enter a fight with one engine in min burner and one in idle, now there's an idea....

'tinker' with the normal maneuvering flaps schedule by delaying normal extension with the NWS (hold retracted) button, now there's an idea....

use a hydraulic isolation system to get variable flap extension, now there's an idea....

use an electrical pilot recovery only flap system for slow speed pitch authority, now there's an idea....

fly in Cat 3, not creative, but noble, now there's an idea.

Occasionally, these 'creative' (or noble) inspirations didn't necessarily work out so well for performance purposes....particularly down low.
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Meteor

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Unread post15 Mar 2020, 02:32

Back in F-4 days, we'd occasionally have to use one in AB, the other below AB, while refueling. A heavily loaded F-4 was on the backside of the power curve while approaching full fuel load. MIL on both wouldn't keep you on the boom for the last 3-4000 lbs. I'd usually refuel without any AB until MIL wasn't enough, then disconnect and drop back to pre-contact. Select one engine to min AB (I preferred the left engine) and then modulate the right engine with thumb and index finger to get back on the boom and stay there.

Unfortunately it took a long time to take aboard the last 3-4000 lbs, because you were burning fuel at almost the same rate as you were taking it aboard.
F-4C/D, F-16A/B/C/D, 727, DC-10, MD-80, A321
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alfakilo

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Unread post15 Mar 2020, 04:36

Meteor wrote:Back in F-4 days, we'd occasionally have to use one in AB, the other below AB, while refueling.


I recall that being common place when tanking off KC-97s.
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optimist

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Unread post15 Mar 2020, 05:51

alfakilo wrote:
Meteor wrote:Back in F-4 days, we'd occasionally have to use one in AB, the other below AB, while refueling.


I recall that being common place when tanking off KC-97s.

Good to see you around, I'm a bit of a fan. Salute and to Meteor et al
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outlaw162

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Unread post15 Mar 2020, 17:15

I find it interesting and curious that it was used during combat maneuvers.


I would bet the guy involved thought of it as poor man's vectored thrust. In many older aircraft you can generate some pretty high yaw rates and the accompanying rapid roll rates at high angles of attack using aerodynamic rudder alone. In a couple of older aircraft you could even cautiously use aileron adverse yaw effects to supplement the rudder. Nothing in place to prevent it.

It may be that in newer(?) aircraft like the F-15, SAS/ARI attempts to "take care of" the pilot at the higher AOAs and limits some of the rudder yaw authority and this is why this guy felt he needed to supplement it with differential thrust. One would think it would not be too much of a problem in moderation, but you walk a fine line at extreme AOAs and high yaw rates....attempting to keep it just short of auto-rotation (stall/spin like this guy).

Occasionally, we would be able to talk an F-15 driver into a 'battle-damage' BFM engagement....one in idle and one in AB.
Never saw a guy have any controllability problems, but I'm sure they were cognizant of the risks.

However, when you're looking back over your shoulder at an F-22 with real vectored thrust, while low and slow and at high AOA, it is probably not the time to get super-aggressive and 'creative' in training.

sidebar: The DC-10 at Sioux City is a premier example of what can be done on the positive side to control the aircraft with differential thrust. Airline guys generally have a pretty good handle on differential thrust usage considerations.
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quicksilver

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Unread post15 Mar 2020, 18:34

“In many older aircraft you can generate some pretty high yaw rates and the accompanying rapid roll rates at high angles of attack using aerodynamic rudder alone.“

TA-4 very good at that. Was taught by an IP who demo’d the difference between doing so at buffet onset (just before the slats would come out), and doing so at ‘optimum aoa’ after the slats came out. Rudder usage a sacrilege for many A-4 guys, but were highly effective in a roller.
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Unread post15 Mar 2020, 21:58

quicksilver wrote:“In many older aircraft you can generate some pretty high yaw rates and the accompanying rapid roll rates at high angles of attack using aerodynamic rudder alone.“

TA-4 very good at that. Was taught by an IP who demo’d the difference between doing so at buffet onset (just before the slats would come out), and doing so at ‘optimum aoa’ after the slats came out. Rudder usage a sacrilege for many A-4 guys, but were highly effective in a roller.

:crazypilot: :shock: HEHEH and a good time was had by all. :mrgreen: Yes our SOP was keep 'on the burble/slight buffet' but of course one could miss the buffet & get dem slats out (hopefully NOT differentially - that REALLY got the roll rate going; but don't do it with the bogey near YOUR SIX). :roll: Dem 'twere daze. TA4G compared to A4G was a DOG, especially moving danose. 8)
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outlaw162

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Unread post16 Mar 2020, 22:39

Old guy's Rudder/Asymmetric Thrust diatribe:

You know the F-15 is really essentially a centerline thrust aircraft, as were for example the F-4, B-727 or DC-9/MD-90 and I imagine, the F-18, Tornado, VC-10, Blinder, MiG-19 or TU-128, etc., etc. as well. For this type, it was generally recommend to use the rudder to counter the small amount of asymmetric thrust resulting from an engine failure, not used to enhance asymmetric thrust. Was a discussion of enhancing rudder inputs with asymmetric thrust left out of the books (MP's original idea or Eagle fleet standard?).

The F-22, though certainly not needing any cheap tricks like asymmetric thrust usage, may however be somewhat squirrelly with one out just because of the humongous amount of thrust produced by one engine even with the small lateral moment arm. However, they probably have software with some sort of magic lateral stability thrust scheduling if one quits, like the B-777 with the GE-90s, or they might have some auto-flight inputs for yaw stability like the A-330, or both. I recall there was a discussion recently about single-engine AB go-around potential in the F-14, possibly overly analyzed, but people have died on asymmetric (AB or not) thrust go-arounds.

The rudder sacrilege mantra, "Just keep your feet on the floor", (replacing "Keep the stick centered"), didn't just apply to the more docile brothers (T-38, F-105, etc.) of the squirrelly old 50s & 60s jets, it is now a basic rule of flying. "Stick and Rudder" is now just "Stick". (No more cheating, tapping a little rudder on a strafe pass, or 'egg-beater' on a dart pass?) :mrgreen: Far, far better world, with fewer options to clutter the playbook.

If one wants real asymmetric poor man's 'thrust vectoring' (the SR-71 was already mentioned), try the B-58, B-707 or A-340 with two out on one side or I imagine the B-47 or B-70 with three out or B-52 with four out. :shock:

In contrast, a single-engine driver doesn't have all these annoying multi-engine concerns to distract him. Single-seat, single-engine....a simple life. :D
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Unread post17 Mar 2020, 04:34

[diatribe for de tribe of 2 or plus more engyns then...] "...In contrast, a single-engine driver doesn't have all these annoying multi-engine concerns to distract him. Single-seat, single-engine....a simple life." :D

And a simple decision IF dat engine quits. EJECT - IF the airfield suitable is close by then one may have the single most enjoyable landing EVA. Just practising it was the most fun. At Nowra the runway was not long enough for the real deal but practice gave us a reason to be hoons with no touch downs just single engine full power wave offs during the flare. 8)
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