MOST UNDERRATED AIRCRAFT OF WWII?

J.A.W. said:

Indeed, Wilkinson notes that the fuel spec for the final Sabre - rated at 3,500hp for take off, was regular 100/130..

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And it needs to be reemphasised, the peak power settings on a Sabre could be sustained for hours. This was not a break-the-wire-and-rebuild-the-engine setting.

KiwiBiggles said:

So the mainstream use of sleeve valves during the war proved normally reliable, but the urgent development of the next generation of engine was problematical. Sounds pretty standard for engine development worldwide.

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Well, there were basically 5 sleeve valve engines.
The 9 cylinder Perseus which may have been a fine engine but it was just too small to power front line combat aircraft.

The 14 cylinder Taurus which fell on it's face coming out of the gate. The Air Ministry was all set to replace it with the poppet valve R-1830 until the ship carrying the first 200 engines was sunk by a U-Boat. Air Ministry decided planes powered by a less than ideal engine were better than planes sitting outside the factory waiting for engines.

The 14 Cylinder Hercules using Perseus cylinders (another reason the Perseus faded from sight), In 1940 there were as host of problems with the Hercules which lead to Merlin powered Beaufighters and Merlin powered Wellingtons. Basically production problems with the sleeves (sound familiar?) which Bristol solved literally in the nick of time. Went on to become a very good engine but never really lead the way in HP per pound or HP per cu in.

The Sabre which we have been debating for pages and pages and.........

The 18 Cylinder Centaurus, while first run in 1938, was put on hold for a number of reasons and not really brought out again until 1943? at any rate the only wartime aircraft to use were some Vickers Warwicks (a lot built but few issued?) The Hawker Tempest II (but did not enter squadron service until after WW II ended, the The Bristol trio.....The Buckingham/Brigand/Buckmaster. Engine may have been much less to blame than the airframe/s.
the Blackburn Firebrand was another late war lashup that did nothing to prove or disprove the Centaurus engine during the war.
The Centaurus was, for all practical purposes a post war engine and it's reliability/engine life and power ratings should be compared to other post war engines.

Shortround6 said:

I do like the car comparisons though. Like the US was incapable of build powerful cars. Picking one of the cheapest US cars of the time and comparing it Blower Bentleys and Mercedes SSKs to try to prove a point about aircraft engines is ludicrous.
Yes the US 2 valve radials were cheaper but not the 10 to 1 ratio (or more) that these cars were. and comparing a 4.5liter supercharged engine to a 3.3 liter unsupercharged car sure doesn't tell you anything new, let alone bringing in the 7 liter supercharged SSK.
Maybe we should bring in the 1928 Stutz? The one that lead Le Mons for over q/w the race before the Gear box broke (and lets remember that the Bentleys often failed to finish 100% of their starters)

We are getting a bit far afield.
The Sleeve valve engines were developed, as I have said before, into high powered, reliable
and long lasting engines. It is just that they didn't offer that much of an improvement over the poppet valve engines of the same time. The millions of pounds invested in the sleeve valve never really paid off despite the gee whiz numbers posted by the last of the engines.

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Duesenberg/ AFAIR, never attempted to win Le Mans, but in the late `20s when Bentley & Benz were
going 'hammer & tongs' - Chrysler & Stutz gave it a red-hot go, getting right up there, fighting for the win, & full credit to 'em..

Ok, you asked for it!

Here's ol' Len Setright getting more'n a tad lurid - about the Sabre..

The Greatest Engines of All Time by LJK Setright

( To be fair, Lenny did have full access to the Napier technical archive, before R-R 'lost' it..)

& re: wartime Centaurus use, 1stly - it didn't have many airframes to go into (as SR6 notes),
2ndly, it had not yet had its 'bugs ironed out', due to Bristol keeping busy..
- with developing & producing ~55,000 Hercules units..

KiwiBiggles said:

Retrospectroscope, much? Poppet valves for high-performance engines were saved by the development of high octane fuels. At the time when sleeve valves were being developed - the Hercules started development in 1936, I think - high octane fuels didn't exist. Sleeve valves were a pretty good way to get high performance from 87 octane fuel.

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Retrospectroscope only a little;
"On September 13, 1935, Hughes piloted the H-1 to a new speed record of 352 miles per hour (566 kilometers per hour) at Martin Field, near Santa Ana, California."
Hughes was using 100 octane fuel. Granted at the time it cost about 10 times what normal av-gas did. At the 1938 Paris air show RR was quoting power figures for 100 octane gas. Everybody knew it was coming, the question was when.

I would also note that the Hercules never went over a 7.0 compression ratio.

P & W R-1830s, R-1535s and even R-1690s (9 cylinder Hornets) used compression ratios of 6.0 on 80 octane fuel and 6.5 to 6.75 (but usually 6.7) when rated on 87 octane.
Sorry, a higher compression of 0.3 points (4.4%?)doesn't seem like that big of an advantage.
Back in the mid 20s when gas was under 70 octane a fair amount of the time the ability to use 6.0 compression vs 5.0 may have been a significant advantage. but that advantage seemed to disappear well before 100 octane showed up. In part because with sodium filled exhaust valves and better heat paths from the valve through the valve guides and into better finning the exhaust valve was no longer the glowing hot spot it had been in the 20s.
No retrospectroscope needed for that one.

KiwiBiggles said:

And it needs to be reemphasised, the peak power settings on a Sabre could be sustained for hours. This was not a break-the-wire-and-rebuild-the-engine setting.

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And it has to be noted that the 3500hp figure was post war, it was take-off only, 5 minutes max and used ADI.

J.A.W. said:

Duesenberg/ AFAIR, never attempted to win Le Mans, but in the late `20s when Bentley & Benz were
going 'hammer & tongs' - Chrysler & Stutz gave it a red-hot go, getting right up there, fighting for the win, & full credit to 'em..

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STUTZ AT LE MANS

Well, if not attempting to win they sure put in a lot laps sightseeing. Not as successful as Bentley (but then they didn't enter 3-5 cars at a time) a few finishes in the top 5 for cars built at over a 1000 a year doesn't seem too bad.

wuzak said:

And it has to be noted that the 3500hp figure was post war, it was take-off only, 5 minutes max and used ADI.

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Sure & that'd likely be a limitation of the Tempest/Fury coolant complex,
however the Sabre had service clearance for an hour's running,
at its considerable 'climb rating' power-setting..
- which is more than R-R's V12s, & the ( as Len Setright put it - "lazybones") US radials - could bear.

Shortround6 said:

STUTZ AT LE MANS

Well, if not attempting to win they sure put in a lot laps sightseeing. Not as successful as Bentley (but then they didn't enter 3-5 cars at a time) a few finishes in the top 5 for cars built at over a 1000 a year doesn't seem too bad.

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Yeah, apologies SR 6, mea culpa, I stuffed up that post,
( haste & distraction, but no excuse) but as soon as I re-read it, I edited it..

& you are correct about the importance of teams, it was what finally won America's 1st big Le Mans title for Ford, 1,2,3!
( albeit it was won by a Kiwi driver crew - in an NZ black - GT 40.)

Some immediate post-war Hercules power/economy figures in this 'Flight' table..
http://www.flightglobal.com/pdfarchive/view/1947/1947 - 1491.html

Anyone care to post the equivalent R-2600 data - for comparison?

I see the 36 litre Griffon burns about 25* (imp) gallons per hour extra @ 25,000ft,
to make ~100 more hp using + 7lbs boost - than the 38 litre Hercules 130 does
at that height - for max lean cruise on +2lbs boost..

* 94 VS 70.

J.A.W. said:

Some immediate post-war Hercules power/economy figures in this 'Flight' table..
http://www.flightglobal.com/pdfarchive/view/1947/1947 - 1491.html

Anyone care to post the equivalent R-2600 data - for comparison?

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And here is were it starts going south, Wright pretty much stopped development of the R-2600 before the war ended. One source claims production ceased immediately at the end of WW II.

But a BB series R-2600 was good for 1900hp at take-off at 2800rpm using 46in of boost (8.0lbs), the engine used a compression ratio of 6.9 to 1.
Cruise fuel consumption was supposed to be 0.46lbs per hp. Cruise rating given was 1040hp at 2100rpm at 10,000ft.
Normal (max continuous) was 1600hp at 2400rpm at 3000ft.
This for a single speed single stage supercharger. Numbers from Wilkinsons Aircraft engines of the World.
Weight was about 2090lbs.
Please note that the 1900hp R-2600s were used in Eastern Aircraft TBM-3s, Curtiss SB2C-3/-4s and Martin PBM-3Ds. They had built just about 1000 of them in 1943. Over 8800 in the Cincinnati plant in 1944 before production was stopped to concentrate on the R-3350.

so yeah, lets compare the Hercules 230 and 730 to an engine that was in production in 1943 and essentially untouched afterwards.
BTW the R-2600 never used water injection. Never used anything better than 100/130.

Want to post the 1943 Hercules figures?

'Flight' appears to have been constrained from publishing those figures during
wartime, due to security concerns, & 'Pilot's Notes' don't go into hp @ rpm figures..

But here's a 'Flight' article from May `45, with the Hercules power/consumption charts:

https://www.flightglobal.com/pdfarchive/view/1945 - 1015.html

Max power: 1,775hp @ 2,800rpm on +7lbs boost for 0.792 lb gas per hp/hr.
Max continuous: 1,550hp @ 2,400rpm on +6lbs boost for 0.693 lb gas per hp/hr.
Max weak cruise: 1,280hp @ 2,400rpm on +3lbs boost for 0.418 lb gas per hp/hr.


Edit: Looks like typical air-cooled radial use of the juice - as an internal coolant, running hard,
& oh yeah, a fine volumetric efficiency factor on eco-cruise, as expected by sleeve-valves..

J.A.W. said:

Ok, you asked for it!

Here's ol' Len Setright getting more'n a tad lurid - about the Sabre..

The Greatest Engines of All Time by LJK Setright

( To be fair, Lenny did have full access to the Napier technical archive, before R-R 'lost' it..)

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Ah, yes, the epitome of flag-waving, where is proven beyond a shadow of a doubt that Sabre was making 2600+ HP on early Typhoons, and capable for 5000 HP later (why not, say, 7000 HP, now that numbers can be tossed around like it's no-one's business?). Yet, not a single facsimile of any original test report was provided by Setright that would've prove those figures. A three stage supercharger on any Sabre??? 3700 BHP day after day??? Never being envisaged as high altitude engine - a lame escuse for not being capable for coming out with a 2-stage S/C. Modestly rated at Typhoon at +15 psi while it took 130 grade fuel and reinforced crankshaft in 1944 to attain +11 psi??? Those are Luft'46-level fairytales, going along with conspiracy theory galore.

Sabre's power (and it was a powerful engine) came from use of many cylinders that allowed for high piston speed and high RPM, good dispacement and heavy weight. Napier knew well that small cylinders/pistons will allow for great RPM with Dagger.
Since there is no such thing as a free lunch, Sabre run too late to matter for the Allied war effort, too late for shadow factories to be built pre-war, and was plagued with reliability problems until those were solved via use of Bristol-made sleeves.

The discussion concerning the Napier engine and the aircraft it powered has been quite illuminating for me to say the least. And while I haven't quite made my mind up yet concerning whether or not the Typhoon/Tempest combo had been "underrated" all these years, you gotta love what these babies were capable of when their engines were in good working order:

View: https://www.youtube.com/watch?v=Wgx8z-QBtGk


View: https://www.youtube.com/watch?v=fQTfXVqNo9A

tomo pauk said:

Ah, yes, the epitome of flag-waving, where is proven beyond a shadow of a doubt that Sabre was making 2600+ HP on early Typhoons, and capable for 5000 HP later (why not, say, 7000 HP, now that numbers can be tossed around like it's no-one's business?). Yet, not a single facsimile of any original test report was provided by Setright that would've prove those figures. A three stage supercharger on any Sabre??? 3700 BHP day after day??? Never being envisaged as high altitude engine - a lame escuse for not being capable for coming out with a 2-stage S/C. Modestly rated at Typhoon at +15 psi while it took 130 grade fuel and reinforced crankshaft in 1944 to attain +11 psi??? Those are Luft'46-level fairytales, going along with conspiracy theory galore.

Sabre's power (and it was a powerful engine) came from use of many cylinders that allowed for high piston speed and high RPM, good dispacement and heavy weight. Napier knew well that small cylinders/pistons will allow for great RPM with Dagger.
Since there is no such thing as a free lunch, Sabre run too late to matter for the Allied war effort, too late for shadow factories to be built pre-war, and was plagued with reliability problems until those were solved via use of Bristol-made
sleeves.

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Tomo, Len Setright did have access to the Sabre's test records, & they - just as the R-2800
& the Merlin did, showed they were capable of greater outputs on test, where the engines
themselves were not subject to the constraints imposed by airframe systems limitations.

In the test cell, available cooling, fuel, & supercharger pressures were practically unlimited,
should the tester want to run the engine core to max capability,
& propeller limitations were also absent.*

Wilkinson gives the official power ratings in his book,
( parts of which are available at wwiiaircraftperformance),
- along with BMEP & fuel grade figures.

The Sabre's crankshaft was modified, 1stly to use steel-backed shell insert plain bearings,
& 2ndly to delete the full counterweighting, which was found to be needless in practice.

Tomo while only 5,000 or so Sabre's were built, you are incorrect to assert that the Hawker
fighters they powered "were too late to matter for the Allied war effort", since those British
civilians being subject to Nazi attacks by FW 190 JaBos in 1942/43 & V1 cruise missiles
in 1944 were certainly glad of the effective interception capabilities bestowed by the Sabre.

& post D-day the Typhoon units bore the brunt of RAF 2nd TAF close support, being able
to range further, faster & with twice the war-load of the Spitfires doing similar work.

The power of the Sabre enabled the Typhoon to carry a significant layer of useful
armour protection too, something the svelte Spitfires could not do.

& when the Tempest was released from ADGB anti-V1 duties & returned to 2nd TAF,
for the offence, in the role of A2A/frontal air-superiority fighter, the Tempest shot down
every kind of long nose Focke-Wulf, late mark Bf 109, & ultra-modern turbo-jet flying..

See Caldwell's JG 26 history for evidence of how fierce were the combats which Tempest units
mounted against LW attempts to intercept Allied tactical aircraft, & mount their own A2G attacks.

Compared to the Centaurus, Griffon & Vulture, the other 'big' British aero-engines, the
Sabre was the most techically advanced of the lot, yet provided more useful war service than
the rest - put together!

*Developing propellers to handle the Sabre's output lagged behind Sabre power capabilities,
& Hawker design boss Sid Camm accused R-R of virtual sabotage - by delaying supply of
the needed Rotol props, ( de Havilland units were proving to be problematic) & Camm
would know, because Rotol props were available for his Bristol Centaurus powered
Tempest Mk II's ( albeit the engines themselves - were scarce!) but not for the Sabre.

(Rotol was co-owned by R-R & Bristol, the letter Ro for R-R, & tol, for Bristol).

The Typhoon was supposed to be a high altitude interceptor. Since it never got high altitude performance I fail to see how it was the most advanced engine and since it never had altitude performance the RAF would always need another fighter. Whatever the Tempests performance in 1944/45 it should have been in service much sooner, instead pilots had to press on in obsolete Hurricanes and Spitfires and others for ground attack for far too long. Napier as a company proved incapable of mass manufacturing their own design so I don't see how they can blame others for their problems.

Seems like you "don't see" - quite a few things, ben..

There really wasn't much high altitude 'trade' for RAF fighters in the ETO, was there..

& the British organised such excessive Merlin production ( while making very few 'big' mills)
that mass-produced obsolete Hurricanes* & out-dated Merlin-Spitfires had to be found
some useful work to do, as 2nd rate A2G 'mud-movers'..

*Albeit the Hurricane was so loss-costly, that it was withdrawn from such ops for the
post D-day, tactical air-power - invasion push into Europe).

J.A.W. said:

There really wasn't much high altitude 'trade' for RAF fighters in the ETO, was there..

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There was a lot of "trade", in high altitude interception, photo recon, there was N Africa, Malta and the far east in addition to "stuff" like Dieppe. You just discount any theatre or era where the Typhoon or Tempest didn't do well, Typhoons were at Dieppe you know.

C'mon ben, that stuff was 'bits & bobs' at best..

& the RAF kept their best, in the NW-ETO..

& as I wrote yesterday.. compare the score board record of the two Kiwi fighter squadrons in Blighty,
485, Spitfire equipped, & 486, who went Hurricane -Typhoon -Tempest, & see which'd got the most 'trade'...

J.A.W. said:

C'mon ben, that stuff was 'bits & bobs' at best..

& as I wrote yesterday.. compare the score board record of the two Kiwi fighter squadrons in Blighty,
485, Spitfire equipped, & 486, who went Hurricane -Typhoon -Tempest, & see which'd got the most 'trade'...

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You switch nimbly between advocating the Sabre as an engine and the Tempest as a plane. Most "trade" in 1944 was actually at high altitude over the Benelux and Germany and by far the most numerous and successful British engine was the Merlin in Lancasters, Halifaxes Moquitos and of course the P51. How did the Tempest get on in Italy, N Africa and the Far east BTW? Both the Sabre and Typhoon were ordered pre war, after years of development a few thousand were made and they did well in one theatre late in the war.