Last & Best of the Piston Engine Fighter Aircraft.

[J.A.W.]

Did the Vulture pass an 'official type test' at 2500hp? Or was it a 'in-house' R/R claim?

It was not a type test, but a Rolls-Royce test.

Lumsden, British Piston Aero-engines and Their Aircraft, claimed that the Vulture had been run to 3,000hp, but Rolls-Royce Heritage Trust could only confirm 2,500hp.

Certainly R/R was unable to successfully de-rate their big R-type V12 in an attempt to establish a practicable TBO, largely due to crankshaft big-end problems, & went back to a fork 'n' blade arrangement for the later Griffon.

I don't know hoe successful derating the R was, considering there was no particular demand for it at the time while there was for Rolls-Royce's PV-12, which would become the Merlin.

I do not know if the Griffon I, as it was called, had master and slave or fork and blade rods. Possibly the former, as it was based on the 1931 version of the R.

The 1929 Rolls-Royce R and the Buzzard, on which it was based, used fork and blade rods.

Big end bearing failures during development for the 1931 Schneider Trophy led to the fork and blade rods being replaced with a master and slave arrangement.

But bearing technology was improving, with the steel backed bearing having been developed in the '20s and was likely available for the Griffon I (and PV-12), but not the R.

If R/R had actually managed to de-bug their problematic Vulture, then production orders for the Hawker Tornado would've been realised - rather than obsolescent Hurricanes built in their thousands - through to mid 1944.

Rolls-Royce were, indeed, systematically de-bugging the Vulture. But there comes a point where using resources to fix the Vulture would cost their other programs - the Merlin and Griffon.

One proposal was to use pairs of fork and blade rods on each crank pin, meaning that two banks would be offset from the others. The advantage of this was that Rolls-Royce would be using proven technology. The disadvantage would be the amount of time and money required to re-engineer the engine and get it into production.

(The Vulture likewise could have also powered the proposed 'Super Mosquito', for which the Griffon was offered, but deemed inadequate).

There were two "super Mosquitoes" proposed - one with twin Sabres, which did not go ahead due to engine supply issues, and one with twin Griffons, which was not thought to offer sufficient performance improvement over the original Mosquito (2 stage Merlins having been introduced and the bulged bomb bay to carry the 4,000lb HC bomb well underway) to warrant development.

As it was, the Napier Sabre was the only British wartime (& world's sole liquid-cooled inline)
fighter plane engine in the 2500+ hp class to see production/service( if, at only ~5000 units,
there were 'never enough to go around').

Of course the 2,500hp+ versions didn't appear until very late in the war.

On another forum (AoWW2) member here 'snowygrouch' has cited/presented evidence
that the UK Air Min requested/required R/R to run production suitability tests on their
R-type, it failed the endurance evaluation, even when de-rated to run on regular fuel.
(During the`30s the early Merlin was proving very problematic, per 'ramp-head' dramas).

Perhaps this was a prompt for R/R to licence-build the GM-Allison steel shell-bearing,
yet the Napier Lion (designed by Rowledge, the same bloke who changed the R-type
to master/slave conrods - per his Lion) seemed to manage well enough, when it was
developed from a 450hp low-comp up through 10-1 & 800+hp (both N/A) to ~1400hp
blown to take the Land-Speed Record for the Cobb/Railton from the R-type holder.

(Maybe this was due to the Lion having crank-end feed lubrication, a feature which
'snowygrouch' credits the Junkers Jumo 213 with, as rationale for hacking power upgrades?)

Whatever production-related issues the Napier Sabre had, crankshaft/conrod design
didn't seem to be one of them (albeit later marks adopted Vandervell steel-shell types,
as a production expedient, as well as deletion of full crankshaft counter-weighting as
needless in a 24 cylinder engine - while ironically enough, Allison duly adopted it, along
with heavy-duty conrods as a durability measure).

Seems a tad odd surely, R/R cancelling their Vulture (esp' when reportedly nearly 'cured')
yet then put an inordinate effort into a 'too big, & too late' Sabre clone - instead?

Sabre boost levels were progressively increased, with commensurate power output,
& even the final service production units were cleared for +15lb boost on 100/130 avgas,
for well over 2500hp (more on ADI), & importantly, over 2000hp for extended periods.

Reading through period 'Flight/The Aeroplane' ads from 1944/46 it is interesting to
see how Bristol's claim to have the most powerful type-tested sleeve valve engine
didn't last long - with Napier's response that their Sabre was type tested at "3000hp+"!

@ tok-tokkie, I can duly report that Bristol ads claimed Centaurus oil consumption as
being "4 pints per hour" for most economical cruise, & double that for hard running...

For a liquid-cooled comparison - Wilkinson lists the oil consumption (in cruise) for the
final "3500hp" Sabre VII as "6 g/hp/hr & the "2300hp" Griffon 69 as "7 g/hp/hr" - FWIW.

[tok-tokkie]

@ J.A.W
"For a liquid-cooled comparison - Wilkinson lists the oil consumption (in cruise) for the
final "3500hp" Sabre VII as "6 g/hp/hr & the "2300hp" Griffon 69 as "7 g/hp/hr" - FWIW."
what is a g? Gallon?? 3500*6=21 000. Gram?

I came across my reference to the oil consumption. It is in this YouTube:
It starts at 7m00 & at 7m32 he says
"This aircraft used to burn a lot of oil."
It carried 108 gallons of top up oil. It had a range of 2000km. Cruising speed 280 KPH so 7 hours flight time. At 4 pints per hour that is just 3.6 gallons per engine. It seems that after a bit of service the engines used a lot more oil than when they left the factory.

To me the Beverly was a gorgeous aircraft. A first principles response to a demand. But it was totally eclipsed by the Hercules.

[Billzilla]

Every now and then I find an article on the Ford GAA 18 litre all-alloy tank engine.
I have wondered how it would have been as an aeroplane engine - Perhaps too tall but built very strongly and from what I've seen the combustion chambers were much better than the Merlin's. And yes down on capacity as well, but with the better chambers (more resistant to detonation) and more boost it might have been a reasonable thing for bombers & the like.

[J.A.W.]

@ J.A.W
"For a liquid-cooled comparison - Wilkinson lists the oil consumption (in cruise) for the
final "3500hp" Sabre VII as "6 g/hp/hr & the "2300hp" Griffon 69 as "7 g/hp/hr" - FWIW."
what is a g? Gallon?? 3500*6=21 000. Gram?

I came across my reference to the oil consumption. It is in this YouTube:
It starts at 7m00 & at 7m32 he says
"This aircraft used to burn a lot of oil."
It carried 108 gallons of top up oil. It had a range of 2000km. Cruising speed 280 KPH so 7 hours flight time. At 4 pints per hour that is just 3.6 gallons per engine. It seems that after a bit of service the engines used a lot more oil than when they left the factory.

To me the Beverly was a gorgeous aircraft. A first principles response to a demand. But it was totally eclipsed by the Hercules.

Dunno about "gorgeous" t-t, more of an ugly egg-bound duck, no doubt it was worked hard though.

As for oil consumption, the R/R Griffon 69 made "1305hp @ 2400rpm" in cruise at 12250 ft.
That would be ~9 kg per hour, at 7 g/hp/hr, so it seems likely the Shackleton would've also had to
carry an auxiliary oil supply on long patrol flights.

[J.A.W.]

Every now and then I find an article on the Ford GAA 18 litre all-alloy tank engine.
I have wondered how it would have been as an aeroplane engine - Perhaps too tall but built very strongly and from what I've seen the combustion chambers were much better than the Merlin's. And yes down on capacity as well, but with the better chambers (more resistant to detonation) and more boost it might have been a reasonable thing for bombers & the like.

Check this link: https://thunderboats.ning.com/profiles/ ... rice-olley

The V8 tank mill was a cut down V12, which shared bore & stroke dimensions with the Merlin, for 27lt,
but was otherwise redesigned to Ford engineering practice - albeit a DOHC 4V - not an iron flat head.

(Ironically, the Merlin also went into service as an N/A tank mill, but still with wear-prone valve gear).

General Motors Allison had the US Army V12 contracts, & Packard was willing to build the Merlin, so
the US Ford V12 aero-engine 'never got off the ground', & while UK Ford did build the Merlin,
US Ford factories produced big P & W R-2800 radials.

[wuzak]

General Motors Allison had the US Army V12 contracts, & Packard was willing to build the Merlin, so
the US Ford V12 aero-engine 'never got off the ground', & while UK Ford did build the Merlin,
US Ford factories produced big P & W R-2800 radials.

Henry Ford was willing to make Merlins, but only for supply to the USA.

Which totally defeated the purpose of seeking a manufacturer for licence production of the Merlin.

[Tommy Cookers]

... yet the Napier Lion (designed by Rowledge, the same bloke who changed the R-type
to master/slave conrods - per his Lion) seemed to manage well enough, when it was
developed from a 450hp low-comp up through 10-1 & 800+hp (both N/A) to ~1400hp
blown to take the Land-Speed Record for the Cobb/Railton from the R-type holder....

the Lion had poor heat transfer to coolant from the steel combustion chambers (this deteriorating with time)
the problem was avoided in 1920s racing by running very rich on 'benzole' fuel (enabling a very high compression ratio)
benzole (from coking of coal) being a mix of benzene,toluene,and xylene(s) giving .....
very high Octane number at rich mixtures due to the low flame temperature
the Lion was for normal purposes made obsolescent by emerging engines c 1926 with.....
open-top cylinder liners with dedicated valve seats fixed into the Aluminium alloy combustion chambers
the gasoline quality improvements in the 1930s would not have saved it
(by the LSR time methanol was combined with benzole for charge cooling eg the RR-powered1931 air speed record)

re the Junkers 3700 or 4500 rpm ....
piston acceleration ie stress is the issue - and ring design for proper behaviour at such high acceleration
high piston speed isn't a crucial problem - if good mep can be be maintained by good cylinder filling
better to have high piston speed for higher power from a given size engine (than going to higher displacement)
because there's little point in high power if the price is proportionately high weight (and high cost etc)

re another post ....
the Henry Ford 'Merlin' was disadvantageously longer and had a thicker heavier crankshaft so more friction and heat
RR made such an engine - they called it the Griffon

yes there's arguments for (and against) quicker/cheaper production - and possible effects on aircraft roles
there was nothing wrong with a 1650 hp Merlin Hurricane - in the right role

the Vulture wasn't '2 Peregrines' ....
it was in cylinder pitch '2 Merlins' - and we have been told that one ran with Merlin-sized bores
an X engine can be as good as the meeting of 4 rods on 1 crankpin ie the rpm it can allow

[wuzak]

the Vulture wasn't '2 Peregrines' ....
it was in cylinder pitch '2 Merlins' - and we have been told that one ran with Merlin-sized bores
an X engine can be as good as the meeting of 4 rods on 1 crankpin ie the rpm it can allow

Not exactly the same Tommy.

Bore spacings (per RRHT) for the main Rolls-Royce piston aero engines of the WW2 era:

Vulture – 6.1in
Kestrel/Peregrine – 5.625in
Merlin – 6.075in
Griffon – 6.9in

The Vulture was originally rated for 3,200rpm (Peregrine 3,000rpm) and the later Pennine, with short stroke (and Merlin bore) was rate to 3,500rpm.

[J.A.W.]

... yet the Napier Lion (designed by Rowledge, the same bloke who changed the R-type
to master/slave conrods - per his Lion) seemed to manage well enough, when it was
developed from a 450hp low-comp up through 10-1 & 800+hp (both N/A) to ~1400hp
blown to take the Land-Speed Record for the Cobb/Railton from the R-type holder....

the Lion had poor heat transfer to coolant from the steel combustion chambers (this deteriorating with time)
the problem was avoided in 1920s racing by running very rich on 'benzole' fuel (enabling a very high compression ratio)
benzole (from coking of coal) being a mix of benzene,toluene,and xylene(s) giving .....
very high Octane number at rich mixtures due to the low flame temperature
the Lion was for normal purposes made obsolescent by emerging engines c 1926 with.....
open-top cylinder liners with dedicated valve seats fixed into the Aluminium alloy combustion chambers
the gasoline quality improvements in the 1930s would not have saved it
(by the LSR time methanol was combined with benzole for charge cooling eg the RR-powered1931 air speed record)

re the Junkers 3700 or 4500 rpm ....
piston acceleration ie stress is the issue - and ring design for proper behaviour at such high acceleration
high piston speed isn't a crucial problem - if good mep can be be maintained by good cylinder filling
better to have high piston speed for higher power from a given size engine (than going to higher displacement)
because there's little point in high power if the price is proportionately high weight (and high cost etc)

re another post ....
the Henry Ford 'Merlin' was disadvantageously longer and had a thicker heavier crankshaft so more friction and heat
RR made such an engine - they called it the Griffon

yes there's arguments for (and against) quicker/cheaper production - and possible effects on aircraft roles
there was nothing wrong with a 1650 hp Merlin Hurricane - in the right role...

T-C, I was referring to the Napier Lion bottom-end construction/lubrication (inc' oil jets to pistons)
being robustly capable of allowing 'type-test' longevity - running as a service engine on regular fuel
(which the R/R R-type was unable to emulate) - as well as a useful high-power tuned 'sprint' engine.

The Ford V12 aero-engine - although sharing the same bore/stroke dimensions as the Merlin - had
a cast crankshaft with twin rods on each crankpin/offset cylinder banks - like their car engines (&
no fork 'n' blade or master-slave arrangement) it'd be interesting to see if it ever passed a 'type-test'.

As for 1944/5 Junkers Jumo 213 piston/ring tech being able to effectively function as scaled-up F1
(N/A) units at equivalent piston speeds (let alone flame-travel combustion aspects) for reliable flight,
even if for limited 'WEP' periods - well, it basically beggars belief - IMO.

Hurricanes had no useful role in assaulting Festung Europa & the post-invasion push into the Reich, &
Clostermann writes poignantly of Hurricanes having to be withdrawn from ops there, after they'd
suffered withering losses from being pressed into A2G sorties against the Nazi V1 launch sites.

Even in Burma/India by 1943, it was needful to send the 'last & best' Merlin Spitfires (Mk VIII) to wrest
air superiority from Nippon fighter units - which were inflicting grinding attrition on the haplessly
outmoded Hurricanes there - too.

[wuzak]

Hurricanes had no useful role in assaulting Festung Europa & the post-invasion push into the Reich, &
Clostermann writes poignantly of Hurricanes having to be withdrawn from ops there, after they'd
suffered withering losses from being pressed into A2G sorties against the Nazi V1 launch sites.

Really?

With the availability of Spitfire Vs, IX/XVIs and XIVs, Mosquito FB.VI, B.IV, B.IX and B.XVI, and Typhoons and Tempests, the RAF had to use Hurricane fighter-bombers against V1 sites?

I am seriously doubting that story.

[wuzak]

T-C, I was referring to the Napier Lion bottom-end construction/lubrication (inc' oil jets to pistons)
being robustly capable of allowing 'type-test' longevity - running as a service engine on regular fuel
(which the R/R R-type was unable to emulate) - as well as a useful high-power tuned 'sprint' engine.

I am unsure as to whether the Buzzard/R/Griffon I had oil jets to the underside of pistons.

I am also unaware as to whether the detuned R/Griffon I ever attempted a type test, let alone passed or failed a type test.

I would also point out that the Buzzard was type tested at 800hp, which I suspect was similar power to a detuned racing Lion that passed a type test. If there ever was such a thing.

The Buzzard was heavier, but not significantly heavier, than the Lion.

[J.A.W.]

Hurricanes had no useful role in assaulting Festung Europa & the post-invasion push into the Reich, &
Clostermann writes poignantly of Hurricanes having to be withdrawn from ops there, after they'd
suffered withering losses from being pressed into A2G sorties against the Nazi V1 launch sites.

Really?

With the availability of Spitfire Vs, IX/XVIs and XIVs, Mosquito FB.VI, B.IV, B.IX and B.XVI, and Typhoons and Tempests, the RAF had to use Hurricane fighter-bombers against V1 sites?

I am seriously doubting that story.

According to P. Clostermann, on escort duties in his Spitfire, in 'The Big Show - C & W 1951'; P.77:

'Discovery of the V1 - December 1943'

"Gradually every every type of aircraft was mobilised & thrown against the 'rocket coast' as the
coast from Boulogne to Cherbourg came to be called. 184 Squadron with its old Hurricanes was
soon sent into the fray. With their four 60lb rockets the miserable machines dragged along at 200mph.
Exceptional courage was needed to go & try conclusions with the German flak at ground level & at
that speed.

With childish levity & spite we poked fun at the pilots & their misgivings. These were all the more
comprehensible as they were beginning to receive their new Typhoons, & it was a really a bit hard
for them to be shot down just as their dreams were about to be realised.

We didn't laugh long at their expense, anyway. On the 4th of December, 8 Hurricanes had just crossed
the French coast when 10 Me 109 G's attacked them... 184 Sq... defended themselves tooth & nail...
the Hurricanes didn't have much hope of coming through. 6 were brought down & the other 2 crashed
on landing... & we laughed on the other side of our faces when it was decided that in future the
Hurricanes would be escorted by Spitfires at ground level."

On '20th December P.81':

"Out of the corner of my eye I watched the Hurricanes about to launch their attack..."

( Clostermann goes on to describe the 'suicidal' attack, with a sole Hurricane surviving the flak,
albeit hit, then being aghast at being sent in to attack in turn):

"There was no question of attack...
I felt I was going to be hit any second & be shot down like the Hurricanes..."

FYI, Spit V's were next to be withdrawn, as also being too vulnerable... similarly, even the
fast twins such as the Mosquito - & P-38 in 9th TAF - (let alone slower Beaufighters) proved
far too large/vulnerable, for dedicated daylight A2G ops against light flak in Festung Europa'.

[J.A.W.]

T-C, I was referring to the Napier Lion bottom-end construction/lubrication (inc' oil jets to pistons)
being robustly capable of allowing 'type-test' longevity - running as a service engine on regular fuel
(which the R/R R-type was unable to emulate) - as well as a useful high-power tuned 'sprint' engine.

I am unsure as to whether the Buzzard/R/Griffon I had oil jets to the underside of pistons.

I am also unaware as to whether the detuned R/Griffon I ever attempted a type test, let alone passed or failed a type test.

I would also point out that the Buzzard was type tested at 800hp, which I suspect was similar power to a detuned racing Lion that passed a type test. If there ever was such a thing.

The Buzzard was heavier, but not significantly heavier, than the Lion.

If you read Harry Ricardo's article (which I've linked a bit earlier in this thread), you'll
learn that prior to available fuels which enabled high pressures to be developed via either
N/A comp-ratios, &/or mechanical supercharging, many large capacity engines were 'lightly'
built, architectural/structural robusticity-wise, (such as the HIspano & the Buzzard?) certainly
the big R/R design required quite a 'make-over' to reach R-type specs, but IF you check the
period data listed by 'snowygrouch' you'll see for yourself, that the R/R R-type failed an Air Min
directed de-rating attempt, & R/R themselves later noted that their mid `40s Griffon could do
power output for hundreds of hours at levels that the Type-R would for maybe a couple...

Rowledge's Lion incorporated a number of outstanding features over a century ago, & which
still do strike the eye accustomed to viewing piston aero-engines as 'modern' not least items
like oil-jets to cool the over-square slipper pistons, 4V DOHC & crank-end feed oil pumping.

[Tommy Cookers]

where to start ?!! ....

200 mph on Closterman's ASI was presumably 250 or more true air speed
ok once airborne the (slower) Hurricane (lower wing loading) might lower thrust efficiency - swings and roundabouts
ok a big-engined ground-attack plane might have made more sense (than a big-engined air-superiority plane)

the Hurricane became a ground-attack aircraft without a ground-attack engine (though the Tempest had such)
ground-attack engine meaning an engine with maximum power ie full throttle height being at very low altitude
such a ground-attack engine needs only a small single-speed supercharger (as Fleet Air Arm & Desert Air Force specs)

Hurricane IIs (Merlin XX engines) were produced from late 1940 - had c.1300 hp @ sea level
Hurricane IIIs were similar via early Packard built engines
(the XX and later twenties-numbered were heavier/longer (2 speed) 'bomber engines' not ideally suiting Hurricanes)

Hurricane IVs introduced a universal ie ground-attack wing - and nominally Merlin 24s or 27s with 1620 hp @ sl ... but
(strongly said on Wiki) - these withheld for Mosquitos & Lancs etc - so production Hurricane IVs all had Merlin XXs
my guess is the Ford GB Merlin factory was 'efficiently' making lots and lots of Merlin XXs that needed homes
how long would they have taken before 'efficiently' making the Vulture ?

Hurricane Vs (1943) had proper 'ground-attack' Merlin 32s of 1700 hp - but no production Hurricane 5s were made

when rocket attacks on tanks became made from vertical dives - Hurricanes would have been the best plane for this


over-square and dohc were Lion features driven by the choice of W12 layout - they would make no sense in a V12
Napier chose W12 to avoid casting difficulties of a V12 (later they rejected the job of 'emulating' the Curtiss V12)

[J.A.W.]

where to start ?!! ....

over-square and dohc were Lion features driven by the choice of W12 layout - they would make no sense in a V12
Napier chose W12 to avoid casting difficulties of a V12 (later they rejected the job of 'emulating' the Curtiss V12)

T-C, both French & Italian W/'broad arrow' contemporaries of the Lion were typically under-square,
& the WW2 era V12s by Ford (USA) & Mikulin (USSR) were DOHC designs - as for Napier's finding any
"difficulties" with casting, somehow their next aero-engine was an X-crankshaft 16 cylinder!

(Nor did Frank Halford's later 16 & 24 cyl' designs, appear to give Napier major "casting difficulties").


Per the obsolescent Hurricane, although the RAF had rightly rejected the US-supplied P-39 & P-40
as unsuited to use in Blighty for cross-channel fighter ops, the USSR gladly took the P-39 (Stalin
told Churchill, send no more Hurricanes) & the P-40 was preferred over the Hurricane in Nth Africa,
where the Allison-powered 'hawks outperformed it on the deck, & the Merlin 'hawks did so 'upstairs'.

Even the FAA complained that their convoy escort-carrier Sea Hurricanes lacked the speed needed to
catch the Luftwaffe's Do 217 maritime recce-bombers in a tail-chase - at any altitude - much to the
chagrin of the fighter pilots involved.