Last & Best of the Piston Engine Fighter Aircraft.

[J.A.W.]

Yeah, going way off-topic there t-t, bringing in C-130s. (& as well, I'd suggest a more apropos
comparison for the Lockheed machine, & one which in turn makes a C-130 look like a fat slug,
is the Tupolev Tu-114, with its cruise speed of 770 km/h & max of 870 km/h, since at least they
are both turboprops, & of true 1950s tech)...

Ok, the Bristol Centaurus was too late for WW2, but it did give a good account of itself later,
& even if as a hard-flying fighter mill it had to give 2nd best to the Sabre, it still beat the R/R
Griffon in hauling about the big Hawker Tempest/Fury. (Oddly, the Griffon got the Avro Shackleton
maritime patrol gig as compensation, although seemingly less suitable than the Centaurus in this role).

I'd also suggest your linked anecdotes sell the ol' Centaurus a bit short too, as this article shows:

https://fredstarr.com/wp-content/upload ... assell.pdf

[tok-tokkie]

J.A.W. I had previously read that paper because my father was in the SAAF where part of his squadron flew Beauforts while his section flew Martin Marylands. They were stationed in Madagascar fighting the Vichy French in 1942. He kept a diary throughout the war. I have posted two long extracts on a local adventure biking site but, stupidly, only the ride reports are open to non members so, to read the thread you need to sign up. Thread: http://www.wilddog.za.net/forum/index.php?topic=9958.20

In post #23 he discusses the Bristol Taurus engine because many of them had crashed due to engine failures while on coastal patrol. Beauforts simply disappeared with the loss of his friends. He was very bitter about it. Here is an extract:
'-------------
The main trouble seems to be in the Taurus engine, but even so, if fully feathering propellers were fitted she would still be able to fly on one engine. But what have we?

The Goddam plane is manufactured and sold with patents & manufacturing rights & yards & miles of red tape covering up & binding down everything. No matter what defect or fault one discovers in the plane, nothing may be done about it without getting permission from the Air Ministry, who have to get it from the manufacturers. So, in spite of the fact that everybody knows that fully feathering props, which, when feathered would offer no wind resistance, would make the Beaufort a more or less safe plane to fly, nothing is, or can be done about it, & in the meantime some patriotic capitalist way back in England is turning them out by the hundreds & thousands & with the proceeds is adding more plush to his already well upholstered bottom & has acquired for himself a title or two for his good work, while the fellows who have joined up to fight for what they have been told is their Freedom? (makes me laugh) have to fly these deathtraps, these flying crashboats, & get killed in them miles & miles from enemy action, & write the planes off into the bargain so that Lord Sir Bloody Hell can sell the RAF another one to take its place to provide another flying coffin for another crew.

That’s what we’re fighting for – freedom of mankind, democracy etc. etc. & all the other political catch phrases. I can now see how bolshevism & revolutions start – no matter what form of government one has, it is inevitably proved to be (if it doesn’t prove itself) rotten to the core in at least one respect, so the man in the street or the bloody fool in the front reckons it’s time for some other form of government, & hey Presto, we have a revolution, but the next government proves just as rotten as the previous one, in other ways.
'--------------
On page 123 & 124 of your link the cause of the problem is detailed.
'---------------
But the oil consumption of the Centaurus would have been a huge problem if they had been fitted to aircraft such as the Shackelton. That was the point of my previous post.

[J.A.W.]

To be sure t-t, the problem of flying a twin-prop plane - with a marginal reserve of power/control
to stay airborne on one engine is bad enough - so the lack of a prop-feathering facility is 'criminal'.

As for your assertion of oil-consumption - do you have any official spec's - which compare Griffon
to the Centaurus? Hawker test pilot Neville Duke flying a Fury from Britain to Baghdad sped 1stly
to Rome in a record time (which beat that set by a De Havilland Vampire), back in the late 1940s,
& much more recently, an ex-Iraqi Fury was flown across the Tasman from NZ to Australia,
so oil consumption in well-kept examples cannot have been all that bad...

Not that apocryphal stories about big radials & oil use profligacy are anything but legion:

https://www.pprune.org/tech-log/364553- ... tions.html

Anyhow, back on subject, here's a classic dissertation by Harry Ricardo himself:

https://engineersatwarww2imeche.files.w ... ngines.pdf

[tok-tokkie]

I have no documentation to back what I wrote. Certainly Neville Duke's flight to Baghdad indicates otherwise.

I did come across this:
“On long flights the engines consumed more oil than was in their 29-gallon oil tanks, so there were two large extra tanks of 59 gallons each in the space behind the navigator’s station and between the main spars. Access was through a hatch for the engineer to select each individual engine tank and replenish the contents using a hand-pump. It took about 64 strokes on this pump, I think, and at 8,000ft that tested one’s lungs.”
https://www.key.aero/article/no-other-aircraft

Thanks for the Ricardo link.

[Tommy Cookers]

NASA shows ....
neither the intended benefits of laminar airfoils nor their 'planned inferiority' in high Cl 'turning matches' happened
https://history.nasa.gov/SP-468/ch5-2.htm

... As for the actual/useful characteristics of low drag 'laminar flow' wing profiles,
you need only refer back up the page to the 'Tactical Comparison' linked in an
earlier post, & check the difference between the (otherwise similar) Typhoon
& Tempest.. (or, given that the Tempest had gained in wing area - a comparison
between Spitfire & Spiteful - where the 'laminar flow' wing was smaller in area).

the Typhoon wing was too thick for best speed - nobody has since 1940 said otherwise
(it was good for climb or weight lifting - like the Hurricane's)
the Tempest wing was far thinner

there is no such thing as 'the drag' of a wing for all conditions of flight
the drag coefficient will be highest at the lowest flight speed .... where the wing will be very inefficient
and lowest at the highest speed - where the wing will also be very inefficient
at zero lift coefficient the efficiency will be zero .... but the drag coefficient then will be the lowest
meaninglessly/delusionally so

of course the Typhoon wing has more drag than the Tempest's at (or near) zero lift
the thinner wing would have less drag in this case - the aerofoil (as NASA shows) is unimportant


the last Beverley has recently been bought for £21000 but the buyer has to collect it - it will never fly again
it's the prototype aka G.A.L 65 - and nowadays it would be classified as a tactical transport
ie it was operable from short low-grade airstrips (like the Hercules and most unlike the Tu-114)
23 ton load with 408 metres takeoff and 277 metres landing (having reverse-pitch props)
(the only dual tactical/strategic transport is the C-17 Globemaster - strategic ie carries a 60 ton main battle tank)
nearby Beverleys and (Hercules) Hastings were a constant sight in our youth

the Merlin and the Griffon are c.30% smaller displacement than the Hercules and the Centaurus respectively
so always gave more range and endurance (because eg operable at lower powers) in the same planes
no-one would want a Centaurus Shackleton - yes the Napier Nomad was seriously considered

[J.A.W.]

...the Merlin and the Griffon are c.30% smaller displacement than the Hercules and the Centaurus respectively
so always gave more range and endurance (because eg operable at lower powers) in the same planes
no-one would want a Centaurus Shackleton - yes the Napier Nomad was seriously considered.

An attempt was made to improve the performance of the Avro Tudor by replacing the Merlin engines
with Hercules radials (the H-P Hermes was so powered), but not with the Griffon per the Shackleton.


T-C, for a contemporary view of Griffon versus Centaurus flight characteristics in Seafire/Sea Fury,
(which are contrary to opinions mooted in your quote) scroll down the page in the site linked below:

https://theaviationgeekclub.com/flying- ... -sea-fury/

[J.A.W.]

Bristol Centaurus

This thread has been mainly about the Napier Sabre but it also discusses the Bristol Centaurus. It was used in the Hawker Sea Fury which came with the Centaurus engine usually but there was one with the Sabre...

Actually t-t, 2 Sabre-Fury aircraft were built, the 1st - LA 610 - originally flew with an R/R Griffon,
with a semi-annular radiator/contra-prop set-up similar to that used by the Shackleton, but once
re-powered by a Sabre with the Hawker wing-LE radiator arrangement, performance was improved.

The 2nd Sabre-Fury - VP 207 - was constructed by Hawker with a higher-spec 'tropical clearance' type
radiator set-up, able to accommodate the most powerful Sabre VII (with ADI) to fly, & being test-flown
at Hawker Langley up through 1948*, while also presented in a special livery for airshow appearances.

Sadly, although kept on hand by Hawkers through to the mid `50s, VP 207 was then scrapped,
just as every other Sabre-powered Hawker in British hands was, thoughtlessly enough...




*Those test-flight reports would make interesting reading, if they could be found, since Sabre-Fury
performance figures already published only relate to the earlier tests made by LA 610.

[Tommy Cookers]

...the Merlin and the Griffon are c.30% smaller displacement than the Hercules and the Centaurus respectively
so always gave more range and endurance (because eg operable at lower powers) in the same plane

An attempt was made to improve the performance of the Avro Tudor by replacing the Merlin engines
with Hercules radials (the H-P Hermes was so powered), but not with the Griffon per the Shackleton.
T-C, for a contemporary view of Griffon versus Centaurus flight characteristics in Seafire/Sea Fury,
(which are contrary to opinions mooted in your quote) scroll down the page in the site linked below:
https://theaviationgeekclub.com/flying- ... -sea-fury/

the only Hercules Tudor ever made was presumably quieter (at the expense of having much less exhaust jet thrust)
even the Hercules 763/773 seems to have 14 exhaust pipes going into a 'collector ring' manifold
North Stars (Merlin DC4s) got so-called 'quieter' crossover exhaust systems - the 2nd version claiming good jet thrust

btw and 'just saying'
Bristol advertised in 1948 Hercules 600 hr TBO - and Hercules Halifaxes had 5' more span than 'existing' Merlin ones

pilots manuals say 60 series Merlins run at 1800 rpm with -4 lb boost (RAF) and 1700 rpm with 20" MAP (USAAF)
(though the lavish Simmonds boost control isn't always claimed to work quite this low ?)
equivalent to 1500/1600 rpm for Griffon or Centaurus - don't know about Shackletons
re Griffon Seafire vibration - most planes have a 'rpm avoid' band at some low rpm
ok 18 cylinders might be better than 12 in this respect
but in the Tempest II the Centaurus had bad vibration below 2000 rpm (so the Sea Fury use anti-vibration mounts ?)
the argument against the big engine is most strongly the bigger energy loss to coolant at low powers


and re the aviationgeekclub link ....
the auto power control eg Tempest II and Sea Fury holds rpm down in eg and iirc takeoff roll and 'low & slow'
probably to give itself an easier job (holding rpm down greatly reduces boost to be regulated - as did fixed pitch)
'auto' (interconnected power&prop) control doesn't get full rpm or full power (CFE Tempest II tactical trials 5.5.45)
maybe 2500 rpm (92% rpm) in takeoff auto gives 96% of max thrust available (wrt manual override to 2700 100% rpm)
(btw even full manual typically doesn't always give 100% rpm until late in the takeoff roll)
by intent or accident auto control reduces the control downside of full manual - with little penalty
a bit like today's traction control of cars etc

[J.A.W.]

Bristol Hercules with "collector ring" exhaust manifold, T-C?

Not on post-war Freighter/Hastings, they seemed to have emulated BMW's 801, as per Do 217
set-up - with multiple pipes arranged 'about the clock' - & 'blowing' to 'vacuum' out cowling air.

[J.A.W.]

Member here 'snowygrouch' in his recent book (mentioned a couple of times before in this thread),
appears to view the Junkers Jumo 213 as the best engineered aero-piston engine, primarily based
it seems - on the 'paper tiger' claims of the 213J - which with 4V heads was expected to rev out
to 3700 rpm, on a 165mm stroke! (Which Bristol designer Roy Fedden thought was a real big ask).

The Junkers Jumo SOHC V12 gear-train makes the British sleeve valve drives appear fairly efficient.

[Tommy Cookers]

Bristol Hercules with "collector ring" exhaust manifold, T-C?
Not on post-war Freighter/Hastings, they seemed to have emulated BMW's 801, as per Do 217
set-up - with multiple pipes arranged 'about the clock' - & 'blowing' to 'vacuum' out cowling air.

ok agreed (about postwar rear exhaust approach)

eg Hermes Ia (WW2 designed) with Hercules 101s had 'front exhaust' and Hermes Ib had 'rear exhaust' Hercules 733s
though not all rear exhaust tailpipes are the same - some less 'round the clock' than others ?

734s (don't know if they have a fan) might have made 1980 hp on 87 grade fuel - but Viking 634 1690 hp
216s on Hastings 264s on Varsities
763s (for 115 fuel) and 773s (same but derated for 100 fuel) had fans - various powers c.2100 - 2300 hp

the Hercules is 6" greater dia than the Taurus - and the Centaurus is 4" greater dia than the Hercules
V12 frontal area is less sensitive to upstroking

btw
the Convair 240 ? had a lavish exhaust thrust etc arrangement

high power via big engine or small ? - Tresilian's design studies (for RR ?) showed much smaller engines as better

[J.A.W.]

Well T-C, sure seems like R/R 'hard-head' Hives didn't buy Tresilian's hype any more
than he did any of the other X-crank R/R engines he'd serially stymied/cancelled...

As Harry Ricardo pointed out in his article (which I linked a few posts back), R/R stuck
to ultra-development of their 'old school' V12 poppet valve mills, so turning out Merlins
like the proverbial 'hot cakes' at a good profit, for many airframes good/bad/mediocre.
(Yet few Griffons, ~1500 for late Spit-Seafires & rest for FAA/Shackleton, prototypes, etc)

But to be fair - by 1945 only the NAA Mustang (as P-51H/P-82) & D-H Hornet - can be
regarded as Merlin-powered contenders for this thread topic, & only at forbidding
boost-levels for somewhat ephemeral* usage periods for high output, at that.

*As per air-cooled radials, as H. Ricardo also duly noted.

[wuzak]

high power via big engine or small ? - Tresilian's design studies (for RR ?) showed much smaller engines as better

Well T-C, sure seems like R/R 'hard-head' Hives didn't buy Tresilian's hype any more
than he did any of the other X-crank R/R engines he'd serially stymied/cancelled...

Tresilian was proposing a X-16 2-stroke, based on Crecy principles, utilizing the Griffon supercharger and an exhaust gas recovery turbine as an alternative to the AP25 gas turbine Rolls-Royce was developing at the time. Both were to deliver 2,500hp.

The Tresilian design was never developed beyond some calculations, and the AP25 was ditched in favour of pure jet engines.

I wouldn't read too much into the Tresilian design being cancelled/not developed. They dumped the Crecy pretty soon after the war as well*.

Of the other Rolls-Royce X engines:
The Eagle XVI was developed by Henry Royce as his preferred alternative to Curtiss D-12. It was developed in parallel, with fewer resources, to the F, which became the Kestrel. Airframe manufacturers preferred the narrower V-12 F. The Eagle XVI was 19.8L vs F/Kestrel's 21.2L.

The Vulture, the only X-type engine of Rolls-Royce's to make production. Reliability issues slowed development, and it was probably deployed too early. Development was suspended, along with most other RR engines, at the time of the Battle of Britain, so that resources could be spent improving the performance of the Merlin. Development freeze also affected the Griffon, btw. In 1941 several programs were cancelled, including the Vulture. It had, however, been successfully run at 2,500hp prior to cancellation. The big problem for the future of the Vulture was the lack of airframes that would use it in the meantime. The Griffon offered more, basically because it could be made to fit in a Spitfire.

The Exe was an X-24 sleeve valve, air cooled 4 stroke of 22L. It was also heavier than the equivalent Merlin (not including radiator), and the power potential was limited by its size.

The Pennine was an X-24 sleeve valve, air cooled 4 stroke of 46L. Designed for post war transport use it demonstrated power of 2,800hp. It was not developed further as Rolls-Royce had turned their attention, for the most part, to gas turbines. The Pennine negated one of the Vulture's failings by using a single piece master rod and a built up crank - somewhat common practice in big radials.


* The Crecy would have been dumped in 1941 had Hives had his way. But Rolls-Royce were required to proceed with development by the Air Ministry, though not a lot of resources were thrown at it.

[J.A.W.]

Ta for that informative post, wuzak.

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

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.

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

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').

T-C, I can confirm you were correct about post-war Bristol radials powering civil passenger
aircraft, as I've recently seen diagram/drawings of a ring-type exhaust manifold fitted to them,
albeit of a rear multi-exit type, rather than the basic wartime single-exit front mounted type.

Furthermore, regarding member 'snowygrouch' holding the Junkers Jumo 213J in high esteem,
I've also seen him make a (seemingly extraordinary) claim - that 4500 rpm would've been within
the mechanical capabilities of that engine - which would have it matching the piston speeds
of the ultra-high rpm N/A F1 engines of just a few years ago!

[wuzak]

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.