Last & Best of the Piston Engine Fighter Aircraft.

[J.A.W.]

T-C, given your suggestion that the 'L-F' profile NPL/Hawker 'high-speed' wing employed
by the Tempest, as a major 'upgrade' over the Typhoon, was somehow of little value, since:

"...the big drag source isn't the wing."

Well, the fact that the Tempest was ~20mph faster at all power-settings, (as well as eliminating the
Typhoon's concerning aerodynamic 'buzz' vibration which caused fatigue to both airframe & pilot)
was an advantage - just as the Spiteful showed over the Spitfire - when both were otherwise
similarly powered, contradicts that particular assertion.. & this was true, even though the wing
area of the Tempest was increased over the Typhoon, & the Spiteful's decreased vs the Spitfire.

The Tempest was found (by more experienced Typhoon pilots than the USAAF chaps you noted)
to be similar in turning, but vastly improved in roll, over the Typhoon, esp' once spring-tab
ailerons were fitted to regular production machines.

Tactical trials of fighters undertaken in early 1944, prior to the Allied invasion of 'Festung Europa'
clearly showed the Tempest held a marked performance edge over all other machines at the low-
to-medium altitudes at which operational sorties in support of the invasion forces would be flown.

Monetary cost of Sabre production and Hawker airframes did not enter into consideration,
indeed rather, just as in F1, qualitative concerns were of greater importance for the projection
of air-superiority, in defence roles for ADGB (Fighter Command), & for 2nd TAF offensive ops.

Anyhow, a significant % of funds spent on British V12 production was squandered via R/R Merlin
by 'Butcher' Harris & his 'export-to-Germany' program via Bomber Command - plus as single-stage
supercharged engines for obsolescent fighters - useless for combat work against Nazi forces, such
as Hurricanes & Mk V Spitfires.

Nor were Mk IX/XVI Spitfires a match for Typhoons when pressed into 2nd TAF A2G work,
& Griffon Spits were not as effective as Tempests in tactical air-superiority roles,
just as the trials had predicted...

[J.A.W.]

...Hawker favoured conservative versatile designs for saleability
eg Hurricane had a large wing area and lift coefficient...

...the reason the Spitfire was unbeatable in a sustained turning match and at altitude

Hawker had to meet the `30s RAF requirement that fighter aircraft be 'light enough on their feet'
not to make divots with their tyres on the standard pitch grass airstrips used by the fighter stations
of the era, so as a heavy plane - the Typhoon had fat tyres within that thick wing & a landing flare
of moderate loading - to ensure compliance.

As for beating the contemporary Spit, see here below:

http://www.wwiiaircraftperformance.org/ ... Trials.pdf

Ok yes, later mark Spits with 2-stage superchargers were thereby endowed with a high-altitude
advantage (but not a critical Mach/IAS limit) over the single-stage Sabre-powered Tempests,
but what use was that, if 'no trade was to be found upstairs', & even the really expensive USAAF
turbo-charged high-altitude configured fighters were sent to the 9th AF for Tactical/A2G tasks...

[Billzilla]

FWIW this is supposed to be a very comprehensive & thorough book on the subject. A little out of my price range right now unfortunately. And even more expensive at ABEBooks.

https://www.booktopia.com.au/the-secret ... 58504.html

[Stu]

There is a fabulous episode of the “We have ways…” podcast on this subject. I’ll see if I can find a link!!

[J.A.W.]

FWIW this is supposed to be a very comprehensive & thorough book on the subject. A little out of my price range right now unfortunately. And even more expensive at ABEBooks.

https://www.booktopia.com.au/the-secret ... 58504.html

Yeah, the author is a member here, but seems a tad reticent to jump in on this thread...

Perhaps due to a few issues in his book, that ah, drew some flak here, on technical grounds.

(To be fair, I have posted some of his literature review research cache, as Calum kindly put it up
on his site - being notably useful - & esp' since the 'Flight' archive is no longer available, on-line).

[Stu]

FWIW this is supposed to be a very comprehensive & thorough book on the subject. A little out of my price range right now unfortunately. And even more expensive at ABEBooks.

https://www.booktopia.com.au/the-secret ... 58504.html

Yeah, the author is a member here, but seems a tad reticent to jump in on this thread...

Perhaps due to a few issues in his book, that ah, drew some flak here, on technical grounds.

(To be fair, I have posted some of his literature review research cache, as Calum kindly put it up
on his site - being notably useful - & esp' since the 'Flight' archive is no longer available, on-line).

He is the guy in the podcast, I think.

[J.A.W.]

He is a member here: 'snowygrouch', but as stated, has not posted on this thread AFAIK,
perhaps the level of discussion is a bit too 'technical' for him - as his posts on a forum
of lesser technical value regarding topical engine matters/usage - would tend to indicate.

(See link below, scroll down to post #15, wherein he falsely conflates max-supercharger boost-pressures
as marker of engine efficiency - rather than say, BMEP, or volumetric efficacy, let alone output/time
at 'normal' power levels - or via fuel use, lbs/hp/hr ).


https://ww2aircraft.net/forum/threads/d ... rpm.57509/

[Tommy Cookers]

He is a member here: 'snowygrouch',
......falsely conflates max-supercharger boost-pressures as marker of engine efficiency ......

supercharger efficiency was improved greatly both with and without added complexity ....
raising engine efficiency in every aspect .....
NACA's head of propulsion Dr Pinkel said that the supercharger was the important thing not the engine

the book discussed iirc covers the advanced throttle/vane thing of Junkers etc via the USSR engines
afaik the same thing was invented by a Polish person in or given to France c.1939 and there seen by the RAE etc
and eventually earmarked for the BRM V16 ? (but never used)

[J.A.W.]

He is a member here: 'snowygrouch',
......falsely conflates max-supercharger boost-pressures as marker of engine efficiency ......

supercharger efficiency was improved greatly both with and without added complexity ....
raising engine efficiency in every aspect .....
NACA's head of propulsion Dr Pinkel said that the supercharger was the important thing not the engine

the book discussed iirc covers the advanced throttle/vane thing of Junkers etc via the USSR engines
afaik the same thing was invented by a Polish person in or given to France c.1939 and there seen by the RAE etc
and eventually earmarked for the BRM V16 ? (but never used)

It misses the essence however, since a less efficient engine can be 'forced' to make more power
by extra boost, but this will still not effectively compensate for volumetric design deficiencies
fundamental to the engine itself, even if it is structurally capable of handling the added pressure
for periodic bursts.

By "...vane thing", you allude to the 'swirl throttle' which did offer efficiency gains via vortex flows.

[johnny comelately]

...the Sabres smaller bore and much shorter stroke would seem ideal for poppet valves
(given the fuel quality revolution)
Sabre funding was maintained both to keep a sleeve-valve foot in the liquid-cooled door,
and a reserve engine for the Vulture.

As regards this view T-C, which you have reiterated in this thread, you might find this
period graph to be of some interest since it shows the Sabre's architecture did in fact
suit the volumetric efficacy of sleeve valves, versus big 2V hemi/4V pent-roof poppets...

(though I don't see what that has to do with the Sabre architecture) ....

the main 'American 2 valve poppet' engine then was the 1820 Wright Cyclone (made for 25+ years)
conveniently for this discussion it had the same bore:stroke ratio as the Bristol engines shewn
but more impressively the later Cyclones at takeoff ran at 2800 rpm - ie 16.3 m/sec or 3850 ft/sec mean piston speed
and the Cyclone supercharger efficiency was improved from 60% to 75% during WW2 - and more post-war
this improvement (as I said before) relieved the suggested problem of poppet valve breathing
over a few years the 1820 Cyclone doubled in power


logic says (though authors don't think of this) that historical improvements in strength ....
(allowing more piston acceleration/rpm but demanding relatively bigger ports/valves at some point)
imply that the ideal bore:stroke ratio would have increased over the years
ie that the old low bore:stroke ratio engines were right for their times

because (strength considerations say) rpm can increase in proportion to the square root of a stroke reduction ....
reduced cylinder volume (eg given bore:stroke ratio) increases breathing (relatively) of both sleeve-valve and poppets
reduced cylinder volume (eg given bore:stroke ratio) increases rpm so increased breathing is handy
these were the basis of Ricardo's and Heron's US Hyper program suggestions ie improving the volumetric 'efficiency'
ie displacement per unit time was raised by raising rpm - but unlike motor sport WW2 didn't have any engine rules

and increased bore:stroke ratios (as Napier) ie tend afaik to reduce the sleeve-valve's breathing (relatively)
(the port height reducing with stroke so port area doesn't rise with rpm rise)
though increased bore:stroke ratios (as Hyper) does increase the poppet-valve's breathing (relatively)
(so only 2 poppets were deemed necessary)

presumably cylinder size/bore:stroke reduction would allow poppet valve breathing to equal sleeve valve breathing
the Sabre was apparently intended for 4000 rpm but only got there via a convoluted and protracted route

I clicked on this because it had Bristol probably not the appropriate thread but.....
Anyway engines never fail to intrigue, here is a Bristol fired up with, to me, an innovative crankhandle, altogether fascinating

[Tommy Cookers]

maybe an original or replica Hucks starter
https://www.rafmuseum.org.uk/research/c ... s-starter/
I have seen them hand-starting it (that takes 3 people)


and ....my latest and overdue attempted refutation of JAW can be reduced to .....

the true measure of volumetric efficiency is the volume of air disturbed (to perform a given military task)
a volume wider and deeper with the Tempest due to its excessive weight - following from the Sabre's excessive weight
.. somewhat analogous to the arguments often used by F1 fans in favour of one car over another

that excessive weight could have been avoided by V12 close-pitched cylinders - ie having cylinder-side ports only
this of course reducing volumetric efficiency in the usual (meaningless) sense

the '2000 hp' class engine concept wasn't better than the '1000 hp' class unless its power:weight ratio was better

[J.A.W.]

maybe an original or replica Hucks starter
https://www.rafmuseum.org.uk/research/c ... s-starter/
I have seen them hand-starting it (that takes 3 people)


and ....my latest and overdue attempted refutation of JAW can be reduced to .....

the true measure of volumetric efficiency is the volume of air disturbed (to perform a given military task)
a volume wider and deeper with the Tempest due to its excessive weight - following from the Sabre's excessive weight
.. somewhat analogous to the arguments often used by F1 fans in favour of one car over another

that excessive weight could have been avoided by V12 close-pitched cylinders - ie having cylinder-side ports only
this of course reducing volumetric efficiency in the usual (meaningless) sense

the '2000 hp' class engine concept wasn't better than the '1000 hp' class unless its power:weight ratio was better

T-C, there are other factors to consider, esp' given advantages in engine output/performance which
meant that the RAF duly kept its Sabre-powered aircraft in hard-flown service, 'til the mid`50s.

The ability to overhaul and vector-intercept fast-flying enemy aircraft in a time:distance requirement
such as countering FW 190 JaBo raids on Southern England, & later the V1 cruise missiles - better than
contemporary Spitfires - was due to the Sabre's higher power setting availability, & one which was also
noted by Mosquito pilots under escort by Typhoons on intruder sorties, flying at a fast low-level cruise,
as they'd had to ask the Typhoon boys to ease off, because their Merlin-power could not keep pace.

Claims of "air disturbed/excessive weight" just do not stand scrutiny, given the size/speed/strength
requirements, and the roles performed - in which neither the RAF's Spitfires, nor their P-47s (on hand
due to 'Lend-Lease') could match their Sabre-powered Hawker machines - for such 'warlike' efficacy...

(Edit: typo correction).

[J.A.W.]

I clicked on this because it had Bristol probably not the appropriate thread but.....
Anyway engines never fail to intrigue, here is a Bristol fired up with, to me, an innovative crankhandle, altogether fascinating

If you think the 'Hucks starter' is fascinating (& it was a method retained by the Soviets through
WWII on their MiG/Yak/Lavochkins) - you should def' check out the 'Coffman starter' - its a real gas!*

* You may recall the original 'Flight of the Phoenix' movie, wherein the Coffman go/no-go ritual was
used as a set-piece of cinematic suspense..

[johnny comelately]

This may have been posted before, very interesting for me

[J.A.W.]

Yeah, it has Johnny, he's a member here ('snowygrouch') but he takes no interest in this thread...

You can read some cogent comments about some of his ah, bold assertions - just a few posts back.