BAe Super Lightning

[rickshaw]

Why would you want to replace the Avons? They're more powerful than the J-57 or the J-79.........

I'm guessing these are very different than the early RR Avons developed in the late 1940's...

Of course they were.  They were an evolutionary development and essentially remained the same design throughout its service life.  There were tweaks, in order to rectify problems with surging, compressors, fan blades and so on.  However, that sort of thing was quite common in engines of the period.

[PR19_Kit]

They were as different as the J-57s and J-79s were different to their early versions.

Replacing an early Avon by a J-57 or J-79 would not make much sense as a later Avon would have all the connections and mounting points in the right place to start with.

The RAF and FAA have direct experience of doing silly things that when they had the British Phantoms re-engined with R-R Speys. That cost a FORTUNE, took an age to do and arguably produced a worse result than if we'd have stayed with the J-79s in the first place. Certainly the 74 Sqdn. crews who flew the later J-79 engined F-4J-UKs reckoned they were far better than the Spey engined FG1s and FGR2s.

[Gondor]

The RAF and FAA have direct experience of doing silly things that when they had the British Phantoms re-engined with R-R Speys. That cost a FORTUNE, took an age to do and arguably produced a worse result than if we'd have stayed with the J-79s in the first place. Certainly the 74 Sqdn. crews who flew the later J-79 engined F-4J-UKs reckoned they were far better than the Spey engined FG1s and FGR2s.

I heard that the Spay engined Phantom was the most powerful engined Phantom, but also the slowest 

Gondor

[eatthis]

The RAF and FAA have direct experience of doing silly things that when they had the British Phantoms re-engined with R-R Speys. That cost a FORTUNE, took an age to do and arguably produced a worse result than if we'd have stayed with the J-79s in the first place. Certainly the 74 Sqdn. crews who flew the later J-79 engined F-4J-UKs reckoned they were far better than the Spey engined FG1s and FGR2s.

I heard that the Spay engined Phantom was the most powerful engined Phantom, but also the slowest 

Gondor

i heard that too i can only assume the big bulge needed to stuff them in buggered the aerodynamics up

[Pellson]

I heard that the Spay engined Phantom was the most powerful engined Phantom, but also the slowest 

Gondor

Power vs aerodynamics for you. The aerodynamics in the supersonic speed regime got so much worse that it more than conuteracted the increased engine output. However, and this actually is interesting, the increased t/o power available with the RR Speys made the FG1 safer to operate from the relatively small carrier used in the RN than its J79 powered US sibling. The conversion was arguably dead expensive, that's true. But it actually improved performance in a very essential situation..  

[KJ_Lesnick]

How about 2 RR Conways...

[rickshaw]

While the Spey engined Phantoms were reputed to be the slowest, they were as noted the most powerful,  particularly in the lower speed regime, with plenty of extra air for the blown flaps.  They were also the most economical and so the RN/RAF Phantoms were the longest legged, another not inconsequential consideration, particularly in a naval aircraft.  Straight-line dash speed is useful to get to the dogfight but sustained turn and high thrust are what wins it.  Dogfighting doesn't occur at supersonic speeds.

[eatthis]

While the Spey engined Phantoms were reputed to be the slowest, they were as noted the most powerful,  particularly in the lower speed regime, with plenty of extra air for the blown flaps.  They were also the most economical and so the RN/RAF Phantoms were the longest legged, another not inconsequential consideration, particularly in a naval aircraft.  Straight-line dash speed is useful to get to the dogfight but sustained turn and high thrust are what wins it.  Dogfighting doesn't occur at supersonic speeds.

i didnt know phantoms had blown flaps?

[rickshaw]

While the Spey engined Phantoms were reputed to be the slowest, they were as noted the most powerful,  particularly in the lower speed regime, with plenty of extra air for the blown flaps.  They were also the most economical and so the RN/RAF Phantoms were the longest legged, another not inconsequential consideration, particularly in a naval aircraft.  Straight-line dash speed is useful to get to the dogfight but sustained turn and high thrust are what wins it.  Dogfighting doesn't occur at supersonic speeds.

i didnt know phantoms had blown flaps?

All Phantoms had IIRC blown flaps:

F-4A (F4H-1F) changes were a leading edge flap boundary layer air control system first used on the 5th preproduction aircraft and blown flaps introduced on the 7th preproduction aircraft.11 The wing leading edges and trailing edge flaps were blown by high-pressure bleed air from the engine compressors, which produced a thin layer of air which helped keep airflow attached at high angles of attack.

[Source]

[Weaver]

The other thing wrong with that side-intake job in the first post is that the engines are not only stacked vertically, they're also staggered horizontally with the lower one being further forward: those side intakes are several feet behind the lower engine's compressor face.....

If you look at the real side-intake Lightnings proposed by BAC, the intakes are under the cockpit.

[eatthis]

The other thing wrong with that side-intake job in the first post is that the engines are not only stacked vertically, they're also staggered horizontally with the lower one being further forward: those side intakes are several feet behind the lower engine's compressor face.....

If you look at the real side-intake Lightnings proposed by BAC, the intakes are under the cockpit.

didnt realise they were that far forward lol
i think mine has some semblance of plausability about it

[Weaver]

Well one of them is - what Petter did was start with the "impossible ideal" of having one engine behind the other, and them offset them just enough for each engine's intake and exhaust ducts to pass each other.

[eatthis]

doesnt vertical stacking mean they clear anyway?

[The Wooksta!]

You still need space for fuel tanks, cockpit, wing spars, etc.  Staggering the engines gives you that.

[kitnut617]

I heard that the Spay engined Phantom was the most powerful engined Phantom, but also the slowest 

Gondor

i heard that too i can only assume the big bulge needed to stuff them in buggered the aerodynamics up

I read that the Spey would accelerate quicker, but top speed was down compared to the J-79