Question: what’s the reason why the F-4 Phantom has engines that are mounted at an angle so that the thrust isn’t aligned with the planes body? Also wouldn’t doesn’t this cause a torque to be applied to the aircraft that would push its nose down?

Posted by Owen_Wilkinson_2004@reddit | aviation | View on Reddit | 12 comments

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hhmb8k@reddit

There was a documentary I saw decades ago about the evolution fighter jet design. One thing that has always stayed with me was their critique of the F4. It particularly bothered me because I think it is a very cool looking plane, but the narrator kept referring to how ugly it was. But the point they were making was that this plane had an abnormal number of asymmetrical "adjustments" to its shape, wings, tail, nose, engine placement, etc. all in an effort to compensate for unwanted handling characteristics. If I ever remember the name of the documentary, I'll post it. They did go into detail about each of the tweeks to the shape of the plane and why.

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killermonkeez1@reddit

Did you find the documentary yet?

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ephesusa@reddit

Seems not

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deleted_by_reddit@reddit

The engines are below the CG, which would cause a huge nose up when power is applied. To counteract this, you rotate the engines so the thrust vector points at the CG, as to not induce a torque.

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Earthbender32@reddit

The same thing applies to the MiG-29, which has the engines flared out, and also to JATO rockets, which are usually aimed away from the aircraft.

I know this comment section is 3 years old, but someone might find this one day.

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D1ssapointment@reddit

I've found this comment the same day

I hope someone finds my comment some day as well

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Earthbender32@reddit

Glad I could be of assistance, if you wanted to, you could consider this me finding your comment lol

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Aviation-liker1244@reddit

I hope someone finds this one

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OkGlass4801@reddit

The Phantom‘s engine installation is a solution to 3 problems: The jet wash/exhaust had to clear the tailplane The engine thrust vector had to point towards the CG to avoid additional pitching moments when changing power settings The engine’s front (inlet) had to clear the wing box and that required a 5.25° upward and 0.25° outward tilt for the J-79. The 5.25° tilt raised the J-79’s first compressor stage by approximately 18 inches compared to the exhaust nozzle. BRITISH F-4K/M: The RR Spey engine centerline was tilted upward by 5.75° due to the larger fan diameter and 0.55° outward due to the lager engine and nozzle diameter.

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