Could Spey Phantom reach mach 2?
 

During my research for for a current project I came across a report by the RAF which claimed that in trials the spey-engined F-4 could reach, in trial conditions, a maximum speed of 1.9 mach at altitude. The F-4J, its closest J79 engined comparison didn't set the heather of fire either, about 2.04 mach. However, I'm sure at least one ppruner could throw some personal light on such blunt figures.

FB:)

Sounds about right.
Spey Phantom had a slightly lower max at alt, but quicker accel down low compared to J79 equipped F-4.
At height, the J79 could attain a higher Mach than the Spey.
Spey - having a wider ar5e wouldn’t have helped the aerodynamics much.

I did hear of an RAF F4 on airtest with no tanks or external stores which managed to get 'on the step' of ram effect and easily exceeded M2.0 and accelerating, but it is apocryphal - and I don't know which engines. Similar J79 spam tale here

Does it matter, since I have the impression that you reach the max mach number and bingo fuel at about the same time.

A friend that flew Phantoms, 15C and E commented that the Phantom was faster. In fact he was very complementary about it in a number of areas over the F-15. Didn’t get into much detail, and not sure of the fits that he was comparing. His experience was F-4 in Vietnam and then F-15 through the 70’s and 80’s.

The operations manual for the USAF F-4C/D/E is on the internet if you look for it. Maximum sustained speed for the J79 powered Phantom (clean or with 4 AIM-7) was listed as Mach 2 / (IAS over 700 knots) above 30.000 ft or Compressor Inlet Temperature of around 121 Degrees C (which ever was reached first). However these limits were allowed to be breached for 5 minutes in any one flight and the aircraft could be taken to Mach 2.4 for a very limited period. I did read somewhere that the CIT limits on the Spey were lower than the J79 and that was one of the reasons that the UK engine powered Phantoms were slower. Airspeed limits with the wing tanks fitted was Mach 1.9.

mainjafad,

Presumably mach 2 was possible when in clean configuration?

FB

Salute!

Good grief. The speed at various altitudes was supposed to be whatever the government specified in the contract. If not, then maybe it had better performance a thousand feet higher or lower. Big deal. 0.10 M is not a big deal when supersonic. Few fights in combat to this day have involved 1.8 M or 2.x M.

The speed is to get to the fight or the intercept.
====================
I flew the non "reheat" ( have to honor the primary posters here) version Spey in the A-7D. It was called the TF-41 and licensed to Allison for U.S. production. Is.that the same motor?

Someone mentioned acceleration, but sounds more like the plane more than the motor. The TF-41 was sluggish compared to the J-79 , or most GE motors. My P&W motors could not accelerate nearly a quickly as the GE ones.

Anyway, a few knots here and there is only important making up the E-M chart, and only plane I know of that flew up at the top of that chart was the SR-71.

Gums sends...

Hey gums, in its day the A-5 Vigilante was certainly capable of M2+!

Over 60 years ago, Cdr Heath and Lt. Monroe accelerated to M2.1, then climbed the jet to over 90000 ft, establishing a new world record (and double flame out!).

Operating the RA-5C off carriers in the Viet Nam war must have been pretty demanding....

When discussing maximum speeds it needs to be made clear whether it is the maximum in level flight or in a dive. I am sure that a Spey engined F4 could not achieve 2.0M in level flight but I did manage to in a dive. The configuration was clean except for one Sparrow on a front station to keep the cg clear of the aft limit. The profile was a max reheat climb to 48,000 ft at the optimum subsonic climb Mach number (0.95M from memory) then a shallow dive (about 5 deg) to the tropopause. I managed to get 2.05M although the first time that I tried I only reached 1.95M because I started the dive from only 45,000 ft.

The really impressive speed aspect of the F4K/M was at low level. The reheat light-up time was slow but then it would reach the IAS limit of 750kts at sea level easily and with less than max reheat even in ‘C’ fit with 2 underwing tanks.

I agree with LOMCEVAKS numbers but would add that if approaching the Trop too quickly it was possible to make a second climb once above M1.03 (Ramps travelled) back up to 45,000ft and then a 5 deg dive would achieve M2.0+.

Also agree that the F4K/M would easily reach 750kts at low level. I have to admit accidentally reaching 795kts chasing some USAF F111s over the North Sea before noticing the speed. Fortunately the tanks stayed on and there was no damage. Any way, as a Flying Officer my "top cover" was my Flt Cdr in the RCP.

LOMCEVAK,a question if I may,in the event you have described,you say that you carried one sparrow to keep within c of g limits.What would happen in a wartime situation,if you had fired all missiles and dropped the tanks.Would you then be flying outside those limits ? would that be possible for very long ?

Without the Sparrow you were still always forward of the aft cg limit but handling was degraded. What I should have said above is that we carried a Sparrow to improve the flying qualities in pitch from those at close to the full aft cg limit. Flying without the Sparrow and using the published full back stick take-off technique I did once scrape the tips of the horizontal stab on take-off.

LOMCEVAK .
I believe that the recommended technique was Full Aft Stick until the nose started to rise and then move the stick forward to hold the takeoff pitch attitude 8-12deg. The aircraft "should" then fly off the ground smoothly. This would even allow a wingman to stay in position during a formation takeoff!

Even with the correct calculations there was a lot of variation due to such factors as nose oleo pressure and C of G.

Your advice about the Forward Sparrow and C of G is correct and was introduced as part of the "dulling down" process. As the ac became ever more G limited and fatigue became an issue, HQ 11Gp looked for anything to reduce over stresses. Yes, without the Fwd Sparrow the ac was even more pitchy, however, once practiced it was a joy to fly. The Ballast Sparrow just made it heavier and less responsive.

interesting that when I look at the numbers the Sparrow is about 1% of the weight of the aircraft (230 kg vs ~25,000). Was the difference just c of g or aerodynamic?

Thanks for the answer LOMCEVICK.I had one experience at flying outside of limits,and it wasn't very pleasant Decided to take my uncle for a quick flip in a Jodel.The a/c was full of fuel,and John was a big chap,and as a very low-houred PPl,I stupldly didn't think of W+B,and set off.Once airborne,despite full nose trim,I had to use a lot of forward stick just to maintain level flight.I didn't like it and went round and landed from a very flat approach.Never made that mistake again !

ex82watcher, Your story reminded me of a trip I did while doing my PPL at a flying club on the South Coast near Brighton. One day I had gone to Biggin with my Instructor in a Cessna 150 for some Flying Club business. While there a chap asked if we could give him a lift to Gatwick.

I reminded my Instructor that we were in the 150 but he said that it would be OK. The Cessna 150 is a 2 seater with an allowance for a 30lb bag behind the seats!

The takeoff took nearly the whole length of Biggins runway and then our rate of climb was almost non existent.

When we arrived at Gatwick we were twice told to orbit due to airliners on approach. Each time we turned we entered light buffet with 30 deg AOB!!! It was only later having a chat with a fellow student with a beer in hand I realised how close we had been to stalling a number of times very close to the ground.

Dom2,

The stab scrape occurred on my fourth Phantom sortie, the other three having been in ‘C’ fit. I was trying to fly the technique that you describe but I was too slow in moving the stick forward to arrest the nose up pitch rate so overshot 12 deg pitch attitude. Lesson learnt!

212man,

I believe that it was just cg related as there was quite a long moment arm to the front station.

I had a conversation with a former USAF Phantom pilot who had done an exchange with the RAF and he commented that the Spey version reached mach 2 very quickly but wouldn't go any faster while the J79 version although not having the same acceleration was the faster aircraft.

I'm highly envious of the speed limits some are quoting on this thread! By the time I flew the F-4 (usually in 'C' fit) in the late '70s, we were limited to around 500KIAS, but I think that in 'B' fit it was 600? We also had a g limit of around +4 and spent most of the time at 350KIAS or less due to the fuel 'moriarty'. Then once a year the tanks came off and we were allowed a bit more speed and g at Deci', but that could come as quite a shock when you've had to potter about at such pedestrian limits for most of the year.

I recall a 527th Aggressor pilot asking why I hadn't tried to defeat his tracking with a 'guns jink' - when I told him of our restrictions, he asked what the heck the RAF was playing at by limiting us in such ways.....

Salute!

Great to hear stuff about something other than Hunters or Bucs or .....

As Lomcevak mentioned, then Beagle, many folks do not appreciate the supersonic climb schedules we had in those old, over-powered beasts. They were slick, low drag designs and most could not turn worth a damn. We still had work to do with all the aero to help "dogfighting", and that was reflected in later birds like the Eagle, Viper, Tiffie, etc. And then the Raptor and new kid on the block - Stubbie.

Most folks do not realize that the father of the Phantom could get to 35,000 feet in about 2 minutes from a standing start at the end of RWY 35. My Voodoo at Grand Forks on a cold day with basic combat loadout, no external tanks, used about 2,000 feet until gear up. Then climb at 30 degrees pitch until 0.9 M, but rarely got there ( the mach) before pushing over and slipping thru the mach. Started back up at 1.3 M to 45,000 feet plus a little. Figure about 5 minutes from brake release. Who hoo for this 22 year old troop, and they were paying me to do it.

I have no doubt the RA-5 was a speed merchant, but never figured it for a good climb. The Viper was really clean, and at 40,000 feet in the A2A loadout we could barely maintain 1.1 M in mil once there and in a slight descent. As Lomcevak pointed out, just a slight bunt to unload really helped. Between 45 and 50,000 feet in the Voodoo, we could hold 1.15 M using min burner on one engine and mil power on the other. God how I miss those days.

Gums sends...

Gums
May I say how much I for one enjoy your posts. Interesting, knowledgeable and authoritative, but at the same time so passionate and evocative that it feels like we’re in the cockpit with you. Much respect.

LOMCEVAK, My comments were slightly tongue in cheek. Yes , a clean F4 did accelerate quite well in Full A/B and may catch the unwary! I seem to recall that we could be airborne in 2500ft and land in 2000ft using slightly different techniques.

On an acceleration to M2.0 if the Trop was reached too early a second climb at above M1.3 (Ramp Schedule) and a 3-5 unit pushover would achieve M2.0.

BEagle, A shame that for the short time you flew the F4 it was so limited in was was allowed.

At the same time (1981-1986) in the USAF on 1964 built D Models and 1975 built E Models we operated to the makers limits. Yes, we could still pull 8g with a very low fuel weight. Those of us who were lucky enough to fly the F4 Phantom (all Models) to their limits were the luckiest people alive. The aircraft, in its time, was one of the all time greats.

Having flown a few different Models, IMHO, the F4M (FGR2) was overall the most capable F4 Phantom. The minor limitations of the Spey were more than overcome by the weapons and weapons system. Lookdown Shootdown in RAFG in the 70s was a unique capability. Until the mid 70s Strike, LL Night All Weather Attack and Recce were all the order of the day. A Slotted Stab, Drooped Ailerons and Rapid Reheat would have been nice additions at a minor cost.

Video Mixdown, I totally agree with you comments concerning gums posts

Flew a clean F4K on a test flight out of Yeovilton. Part of it was to check the movements of the ramps. So having followed the profile and at about 38,000ft or thereabouts in full burner, continued to accelerate to see how it would go. Managed 2.2M. The next problem was slowing down as there had been a couple of flameouts coming out of burner. Therefore, somewhere just west of Chivenor, laid in about a 3 G turn to starboard, and gently eased both engines back to min burner. Follow by easing them individually back in to military power. This turn appeared to take up most of the Bristol Channel.

As I imagined speed range etc is always dependent on various factors. The figures I've come across I believe relate to a specific series of tests to establish a guaranteed level of performance, if that makes sense. It doesn't surprise me that twothree managed to significantly out do the higher altitude figure which I came across, hence I thought I'd bandy this about some folk who'd know.:ok:

FB

So, Twothree, whereabouts and on what heading did you undertake your supersonic run - turning stbd just west of Chivenor?

Dominator2,

The YF-4M XT 852 did indeed have drooped ailerons and the slotted stab (I am not sure whether or not the other YF-4M, XT 853, did or did not). Therefore, it would be interesting to know why the production F-4Ms did not. 852 died on the scrap heap at West Freugh having flown relatively few hours (probably less than 1000); it was a great airframe when it was still flying and we used to borrow it at Boscombe from BAe from time to time. Very happy days!

What do you think!!!!

Salute!

For some reason I always thot the Spey would have better gas mileage than the J-79. Amongst the colonists, the F-4 was well known as a gas guzzler, especially from about 1966 to 1973. That was during that miserable fracas where many of us made our bones.

Funniest story we had in the SLUF community was a radio call at Udorn when one of our flights had to land there and refuel. Bear in mind we were flying the Spey motor, minus reheat. About 14,500 lb thrust at mil, and awesome TSFC. So the guys get to the rwy and hold. After 5 or 6 minutes the tower asks about their fuel abort time. Huh? Seems the F-4 J-79's were so bad it could not even get to first refueling point for the mission. So our naive flight leader asks what that was all about. Because we had over 9,000 lb internal and two 300 gal tanks, the calculation was tough, LOL. From Udorn to Korat took about 2,500 pounds, maybe 3,000. Burning about 500 pounds per hour on the ramp, our flight lead told the tower we could hold for maybe another 8 or 9 hours. If I had been him, I woulda ordered pizza!

The only time we had to refuel at the outset of a mission was during the Christmas blitz when they took away our drops and increased the number of MK-82's. So we hit the tank on the way to Hanoi, but came home at 40K, burning about 1,500 pounds per hour. That was in your modified Spey that Allison built for us. We still had two Winders and two ALQ ECM pods, plus the drag from the MER's. Always comfortable in that plane WRT fuel.

Gums sends...