F4 engines - angled down - why

[nzhills]

Hi, does anyone know why the motors on the F4 phantom seem to be angled down? Is this for the thrust line to go through the C.o.G. or to account for particularly short ground crew that needed to service the burner? Regards Mark

[DaveReidUK]

The engine is installed along the longitudinal axis of the airframe, it's only the exhaust nozzle that's canted. Presumably a feature of the aircraft's original carrier-borne role.

[Rhino power]

Not true Dave, the engine and nozzle are all installed with a down angle of a few degrees, not just the nozzle. It was a combination of reasons iirc, one being the need for the compressor end of the engine to clear the wingbox structure and another being for the jet eflux to clear the stabilators at the nozzle end and also to balance the thrust line with aircraft's c of g, as already noted by the OP. My memory on the subject is fuzzy however and there may be more pertinent reasons for the downward cant that I've forgotten...

[DaveReidUK]

Thanks, I stand corrected, you live and learn ...

The thrust line appears to be at about 5° incidence (a couple of degrees higher on the Spey-engined variants), which would put the J79's first stage about 18" higher than the nozzle.

[Machinbird]

Due to the engine angle, there was a not insignificant pitch down effect when plugging in full afterburner.
Very visible when flying someone's wing and then accelerating away.

Concur with Rhino Power's analysis. We were constantly monitoring the stabilators for loose fasteners from the acoustic vibration.

The compressor section of the engine had to travel a considerable distance forward over the wing structure during installation. The front end of each engine was supported at the 12 o'clock position by a roller skate mount that rode in a permanently installed track since there was no way to support that end of the engine otherwise. After unusually violent events, you would occasionally find that the front end of an engine had broken free and settled.:uhoh:

[garyscott]

I would have thought that, at least one of the reasons for the downward line of the engines, is that, as a predominantly Naval aircraft (as designed), the downward vector would aid in providing a degree of lift (once set with stab trim, flap and slat) to help with lowering the approach speed.

[DaveReidUK]

Well I got that bit right, at least. :O

Presumably a feature of the aircraft's original carrier-borne role.

[Uplinker]

Hmm, interesting.

You seemed quite dismissive when others asked about the angle of Viscount engines.........

[mustafagander]

You could try looking up the "Pod Nod Mod" on B744s.

[CharlieJuliet]

Remember operating out of RoNAF Andoya in March '70 and having to be cleared for take-off before taxi as, if we stopped, the downward pointing engines melted everything under them which then turned into sheet ice. If we kept moving the surface wasn't affected quite so much, but there was still a need to keep putting down sand to maintain traction.

[fantom]

To elevate the pilot to his correct status.

No wimmin were hurt in the making of this post.

[JER1]

C-J

Remember it well - a challenging and fun detachment. Guess we were on the Can-Openers at the same time??

[Gen. Anaesthetic]

Clearly it was an OH&S thing so that the shorter folks didn't have to stand on their tippy toes to roast their hot dogs!:O