Late war fighter competition

[J.A.W.]

Seriously? You think +25lbs boost sans ADI is "derated"?
That boost level was as good as it got, & those late mark Merlins were significantly 'uprated' mechanically to hack it..

Are you sure you are not thinking of post-war service, where engines usually had to make do with 100/130 juice
(& really needed the 150 grade - to pump that hard), were 'derated' accordingly?

 

[J.A.W.]

D-w, is it possible you are confusing R-R test cell outputs - with the actual service clearance - 'rating'?

See here: http://www.flightglobal.com/pdfarchive/view/1946/1946 - 0165.html

 

[wuzak]

Seriously? You think +25lbs boost sans ADI is "derated"?
That boost level was as good as it got, & those late mark Merlins were significantly 'uprated' mechanically to hack it..

Are you sure you are not thinking of post-war service, where engines usually had to make do with 100/130 juice
(& really needed the 150 grade - to pump that hard), were 'derated' accordingly?

Did they operate at +25psi post war, or did they use +18psi?

 

[J.A.W.]

Did they operate at +25psi post war, or did they use +18psi?

Exactly..

 

[wuzak]

Exactly..

I assumed that they used +18psi post war because the need for the extra power was limited.

Maybe in the Malayan Emergency.

 

[wuzak]

On the British side that was probably because the first jet to take to the air was substantially faster than the RAFs front line fighter, it did 350MPH on its first proper flight tests in 1941 and a fastest of 505MPH in 1943. Other nations made exactly the same judgement, the era of props was over, they would fill in niches and still do.

Actually, if you read the RAF's appraisal of the early Meteor's combat capability,
'damned by faint praise' - just about sums it up (while carefully phrased in 'must please the boss' terms)..

I believe pbehn may have been talking about the Gloster E28/39. The Meteor didn't fly until 1943.

 

[J.A.W.]

Well ok, but that Gloster was only a research aircraft, not a service fighter,
& the AFDU had tested one of the latter, in Sept/Oct `41, to over 400mph, - the Typhoon..

 

[pbehn]

I believe pbehn may have been talking about the Gloster E28/39. The Meteor didn't fly until 1943.

I was, it flew with a variety of engines, since it was the first it was the equivalent of the Wright flyer, but still did 505 MHP.

 

[J.A.W.]

Was that "505mph" the wee Gloster's 'Flying Limitation Speed' - by any chance, pbehn?

AFAIR, wartime Meteors had a similar 'Pilot's Notes' advisement, whereas Gloster
also built thousands of Typhoons - which were good for '525mph' - by the book..

 

[pbehn]

Was that "505mph" the wee Gloster's 'Flying Limitation Speed' - by any chance, pbehn?

AFAIR, wartime Meteors had a similar 'Pilot's Notes' advisement, whereas Gloster
also built thousands of Typhoons - which were good for '525mph' - by the book..

I think you are deliberately missing the point, the fact that it achieved a speed and height that was beyond the best piston engine planes in its first version meant piston engines were obsolete as soon as they could be sorted and put in service.

 

[J.A.W.]

I think you are deliberately missing the point, the fact that it achieved a speed and height that was beyond the best piston engine planes in its first version meant piston engines were obsolete as soon as they could be sorted and put in service.

Actually IMO, its you who is "missing the point"..
Sure, turbine-power was the future for fighters..
but none of the operational wartime jets made fully practicable warplanes..
& 2nd TAF Tempests hacked down every type of LW turbojet flying, something no Gloster jet did..

 

[pbehn]

Actually IMO, its you who is "missing the point"..
Sure, turbine-power was the future for fighters..
but none of the operational wartime jets made fully practicable warplanes..
& 2nd TAF Tempests hacked down every type of LW turbojet flying, something no Gloster jet did..

In 1944, that is 3 years after the first UK jet flew. The Tempest was developed from the Typhoon, the design of the Typhoon started in 1937 the same year that the Sabre first ran, and decades after the first internal combustion engine.

 

[J.A.W.]

& going by the thread topic..

None of the "late war fighter" jets were practicable warplanes - by comparison to the top piston-jobs.

The RAF & USAAF would not have sanctioned operational use of the 162/234/262 either, frankly.

 

[drewwizard]

But the me-262 was the inspiration which created the F-86 swept wing. First flight of the F-86 was 1947. P-80 acceptance was the end of 1945. Everyone knew jets of this caliber were already on the drawing board before the end of WWII. No piston fighter would compete in a fighter role. The only advantage was the ability to carry a small bomb load and staffing capability for a long distance. Fighter bomber. That's why the hornet and similar piston machines survived for a few years more. Plus like the P-51 and others they had life as an attack plane.

 

[J.A.W.]

No it wasn't.. The FJ Fury straight-wing was the 1st jet fighter from North American Aviation,
& the Me 262 was only a defacto swept-wing design - due to CoG issues, not as a high-Mach measure..

Swept-wing studies had been in the aviation science literature for a good period..
before the F-86 & MiG 15, proved it to be effective in combat, even versus much higher thrust Meteors..

 

[drewwizard]

I looked up the merlin info. A 2,640HP version of the merlin was available, but the 130/131 was more aerodynamic (lower frontal area) and the higher power was not needed. lower boost and more reliability. The griffin 2,00 hp to 2400 hp (I was surprised that the Griffin was even close in HP to the later versions of the Merlin which is considerably smaller)
Production engines
The Merlin II and III series were the first main production versions of the engine. The Merlin III was the first version to incorporate a "universal" propeller shaft, allowing either de Havilland or Rotol manufactured propellers to be used.[22]

The first major version to incorporate changes brought about through experience in operational service was the XX, which was designed to run on 100 octane fuel.[nb 2] This fuel allowed higher manifold pressures, which were achieved by increasing the boost from the centrifugal supercharger. The Merlin XX also utilised the two-speed superchargers designed by Rolls-Royce, resulting in increased power at higher altitudes than previous versions. Another improvement, introduced with the Merlin X, was the use of a 70%–30% water-glycol coolant mix rather than the 100% glycol of the earlier versions. This substantially improved engine life and reliability, removed the fire hazard of the flammable ethylene glycol, and reduced the oil leaks that had been a problem with the early Merlin I, II and III series.[24]

The process of improvement continued, with later versions running on higher octane ratings, delivering more power. Fundamental design changes were also made to all key components, again increasing the engine's life and reliability. By the end of the war the "little" engine was delivering over 1,600 horsepower (1,200 kW) in common versions, and as much as 2,030 horsepower (1,540 kW) in the Merlin 130/131 versions specifically designed for the de Havilland Hornet.[25] Ultimately, during tests conducted by Rolls-Royce at Derby, an RM.17.SM (the high altitude version of the Merlin 100-Series) achieved 2,640 horsepower (1,969 kW) at 36 lb boost (103"Hg) on 150 octane fuel with water injection.[26]

With the end of the war, work on improving Merlin power output was halted and the development effort was concentrated on civil derivatives of the Merlin.[27] Development of what became the "Transport Merlin" (TML)[28] commenced with the Merlin 102 (the first Merlin to complete the new civil type-test requirements) and was aimed at improving reliability and service overhaul periods for airline operators using airliner and transport aircraft such as the Avro Lancastrian, Avro York (Merlin 500-series), Avro Tudor II & IV (Merlin 621), Tudor IVB & V (Merlin 623), TCA Canadair North Star (Merlin 724) and BOAC Argonaut (Merlin 724-IC).[29] By 1951 time between overhaul (TBO) was typically 650–800 hours depending on use.[30][31] By then single-stage engines had accumulated 2,615,000 engine hours in civil operation, and two-stage engines 1,169,000.[32]

In addition, an exhaust system to reduce noise levels to below those from ejector exhausts was devised for the North Star/Argonaut. This "cross-over" system took the exhaust flow from the inboard bank of cylinders up-and-over the engine before discharging the exhaust stream on the outboard side of the UPP nacelle. As a result, sound levels were reduced by between 5 and 8 decibels. The modified exhaust also conferred an increase in horsepower over the unmodified system of 38 hp (28 kW), resulting in a 5 knot improvement in true air speed. Still-air range of the aircraft was also improved by around 4 per cent.[28] The modified engine was designated the "TMO" and the modified exhaust system was supplied as kit that could be installed on existing engines either by the operator or by Rolls-Royce.[28]

Power ratings for the civil Merlin 600, 620, and 621-series was 1,160 hp (870 kW) continuous cruising at 23,500 feet (7,200 m), and 1,725 hp (1,286 kW) for take-off. Merlins 622–626 were rated at 1,420 hp (1,060 kW) continuous cruising at 18,700 feet (5,700 m), and 1,760 hp (1,310 kW) for take-off. Engines were available with single-stage, two-speed supercharging (500-series), two-stage, two-speed supercharging (600-series), and with full intercooling, or with half intercooling/charge heating, charge heating being employed for cold area use such as in Canada.[29] Civil Merlin engines in airline service flew 7,818,000 air miles in 1946, 17,455,000 in 1947, and 24,850,000 miles in 1948.[33]

 

[drewwizard]

Yes the swept wing of the ME-262 was a very fortunate accident, but the results were obvious in speed improvement. The designers of the F-86 made a straight wing prototype and realized they were never going to get the speed they required and turned to the ME-262 swept wings. Yes there were a lot of research available on swept wings, and real test data on the ME 163 to prove out the swept wing to both the Americans and the Russians.

 

[J.A.W.]

Ah, no.. the "2,640hp version of the Merlin" was a test unit, & was not "available" for service use..

The +25lb boost power-setting was - as has been noted - dependant on the use of 150 grade av-gas..

 

[wuzak]

Ah, no.. the "2,640hp version of the Merlin" was a test unit, & was not "available" for service use..

The +25lb boost power-setting was - as has been noted - dependant on the use of 150 grade av-gas..

+25psi boost may have been available had Rolls-Royce decided to use ADI.

The 2,640hp RM.17SM Merlin ran +36psi boost, PN150 fuel (maybe with extra TEL) and ADI. The RM.17SM also recorded 2,380hp (@ 3,300rpm, +30psi boost, IIRC) for at least 15 minutes continuously during other tests. This was in 1944.

The RM.17SM was to be rated at 2,200hp in MS gear (not sure of altitude) and 2,100hp in FS gear (~15,000ft).

The RM.17SM had larger supercharger impellers. 1st stage was 12.7" vs 12.0" of regular Merlin, 2nd stage was 10.7" vs 10.25".

 

[J.A.W.]

R-R did add ADI to its Griffon, for Shackleton patrol bomber - max take-off boost, but AFAIR,
Packard with the P-51H,(& P-82?) - was the only R-R V12 powered fighter to use it..

Griffon-Spits being somewhat 'over-powered' weren't cleared to use max-boost for take off anyhow, unlike Tempests..