Last & Best of the Piston Engine Fighter Aircraft.

[Tommy Cookers]

T-C, as a perusal of the Pilot's Notes of the various Griffon-powered Seafire/Spitfire marks
will show - only the contra-prop equipped types - were cleared for full-power take-offs.

I have already shown that this is false and how this is false
if true that would have been material and stated in official correspondence/disputes at the time and available since to history

amusingly the contra-prop Seafires had less thrust for a given takeoff power (having smaller prop diameter)
ie the propstream being smaller would be faster and so have less efficient of conversion of power into thrust

good conversion of power into thrust at low speed eg Sea Fury 14' prop means sacrifice of conversion efficiency at high speed
the design of a fighter shouldn't be skewed towards low speed conversion - but the design for ground attack should be

[J.A.W.]

T-C, as a perusal of the Pilot's Notes of the various Griffon-powered Seafire/Spitfire marks
will show - only the contra-prop equipped types - were cleared for full-power take-offs.

I have already shown that this is false and how this is false
if true that would have been material and stated in official correspondence/disputes at the time and available since to history

amusingly the contra-prop Seafires had less thrust for a given takeoff power (having smaller prop diameter)
ie the propstream being smaller would be faster and so have less efficient of conversion of power into thrust

good conversion of power into thrust at low speed eg Sea Fury 14' prop means sacrifice of conversion efficiency at high speed
the design of a fighter shouldn't be skewed towards low speed conversion - but the design for ground attack should be

Well T-C, I've cited verbatim from the 'Pilots Notes' & posted a link to a site where they can
be checked, so any "false" claims can be debunked at source, for those who are interested...

As for the contraprop offering neutral torque effects & thus allowing a max-available boost
power-level for take-off accordingly, that would indeed tend to negate yet another assertion.

The Centaurus radial powered Hawker Fury used a smaller diameter (albeit a 5-blade) prop
than the 14ft unit of the Sabre Tempest, while the Fury prototype which also flew with the
R-R Griffon - ran contraprops, which were duly cropped in an attempt to find the predicted
performance - yet the Martin-Baker MB5 also utilised a contraprop set up, sans drama.

[J.A.W.]

This vid shows how a longnosed Spitfire Mk 18 contrasts with a shortnosed FW 190A,
staccato growl & supercharger whine of the R/R Griffon vs BMW's grumbling rumble:

[hollus]

This was initially posted yesterday and initially removed, because "one does not just make a first post in a forum with links to a commercial product in it" /insertlordoftheringsmemehere/

It turns out to be relevant, so here is the post and links:

Going back to "The Secret Horsepower Race" whih someone mentioned earlier in this thread, for those interested my WW2 fighter engines book is finally at the printers and will be sent out in 4 weeks. (I`m the author).

The publisher has made a 22page preview (of the 470 pages), which includes the Foreword by
James Allison.

https://issuu.com/mortons-digital/docs/ ... Nzk0MzA3Nw

If anyone is interested in purchasing, best link is below:

https://www.mortonsbooks.co.uk/product/ ... Code/15057

I think we have about 50 of the signed ones left (1st come 1st served) and 700 of the total 2000
print run left.

@snowygrouch, it looks like the automatic site bots also found this suspicious and your user might have been deactivated. If you cannot log in, feel free to make a new user to join any discussion.

[63l8qrrfy6]

Totally relevant I would say.

I might have been the one to mention the book a while ago.

Callum is a former colleague and one of the best engineers I've worked with.
He's had spells in engine design at TMG (Toyota) and Mercedes HPP.

I've been to a couple of his lectures on ww2 engine design and all I can say is the book is a must have for anyone with an interest in the field.

[J.A.W.]

Totally relevant I would say.

I might have been the one to mention the book a while ago.

Callum is a former colleague and one of the best engineers I've worked with.
He's had spells in engine design at TMG (Toyota) and Mercedes HPP.

I've been to a couple of his lectures on ww2 engine design and all I can say is the book is a must have for anyone with an interest in the field.

In an oddly convergent coincidence, Calum has posted some excerpts from his book on
a WW2 aircraft forum, & on page 79 he discusses the crankshaft details of the Jumo V12
engine, noting that it featured through drilling with plain big-end bearings, pressure-fed from
the end, glowingly describing it as "...decades ahead of its time " & "...probably prompted by the
high cylinder pressures of the diesel engines which Jumo had already become famous for..."

Yet as shown in a recent crankshaft design thread, these features had in fact been in use
by Napier in their 'Lion' W12 engine for "decades" already, (& given that Napier & Jumo
were on 'friendly' business terms, it seems probable that Jumo would've had a Lion to
inspect, just as Napier's had access to Jumo 2T diesel-tech - indeed buying a licence
to manufacture them & post-war utilizing its design in their big 'Deltic' diesels) - so it is
perhaps not unreasonable - to sheet home these design qualities to the proven British unit.

[tangodjango]

While I know this isn't relevant for this particular topic. I was unsure where to post it and hope some of the experts on here could shed some light on this aspect of aircraft engines:
"One engineering problem that all of these aircraft have to overcome is how air is ingested by the engines at high speed.

Gulping in air at supersonic speeds creates problems for all aircraft engines. The intakes are devised so as to break up that airflow and reduce it to a velocity the engine can cope with.

It's a highly sensitive area, which even caused an Anglo-French rift at the time of Concorde's retirement. Air France retired its fleet, but British Airways was keen to keep the aircraft flying.

"One reason Airbus, which had assumed authority over Concorde's design, wouldn't give us the full design authority to keep it flying was because the intake design was still secret," says Mr Bannister."

BBC News - New jets promise to revive supersonic travel
https://www.bbc.co.uk/news/business-54416696

[J.A.W.]

While I know this isn't relevant for this particular topic. I was unsure where to post it and hope some of the experts on here could shed some light on this aspect of aircraft engines:
"One engineering problem that all of these aircraft have to overcome is how air is ingested by the engines at high speed.

Gulping in air at supersonic speeds creates problems for all aircraft engines. The intakes are devised so as to break up that airflow and reduce it to a velocity the engine can cope with.

It's a highly sensitive area, which even caused an Anglo-French rift at the time of Concorde's retirement. Air France retired its fleet, but British Airways was keen to keep the aircraft flying.

"One reason Airbus, which had assumed authority over Concorde's design, wouldn't give us the full design authority to keep it flying was because the intake design was still secret," says Mr Bannister."

BBC News - New jets promise to revive supersonic travel
https://www.bbc.co.uk/news/business-54416696

Yeah, you should probably start a dedicated thread, & FYI, its not so "secret",
check this citation, linked below:

https://www.heritageconcorde.com/air-in-take-system

Previously, the Americans had built long-range Mach 3 military aircraft,
like the SR-71, (including the largest ever to fly, the XB-70), & in these, had
chosen other methods to blend problematic supersonic shock & air intakes.

If you are interested in supersonic nozzle design, (which may relate to F1 tech),
NASA education conveniently offers a 'DIY' program:

https://www.grc.nasa.gov/WWW/k-12/airplane/ienzl.html

[J.A.W.]

Here below is linked an excellently concise, cogently written article by Bill Pearce,
describing the fabulous Napier Sabre, as a service engine itself, a mighty achievement.

https://oldmachinepress.com/2020/09/20/ ... ft-engine/

I'll just add that for all the drama & myths ascribed to this engine as being
somehow diabolically complex (complexity & multiplicity are not the same thing),
& an expensive horror show to keep functional, the RAF always operated them hard,
from wartime interception duties (inc' German jet planes/missiles) & postwar in
rough African/Middle Eastern conditions, then right up to the mid`50s, in providing
realistic high-speed low-level target-training for NATO jet-jockeys...

[Tommy Cookers]

yes that article is good
I notice that the Sabre was changed in the last version to have individual exhaust stubs
the British experts having never properly merged exhaust pulses (because they didn't believe in exhaust pulses)
like the experts who believed that an exhaust turbine couldn't recover power without 'back pressure'
but the author seems to say the later Sabre was the only 3000 hp engine

nobody seems to be creating by conversion a Sabre Tempest or Fury - but Sabres are held for recreating Typhoons
one possible DIY 'Last & Best' is a F2G-1 'Goodyear Corsair' (and conversion is legitimate here)
Cleland won the big races by turning the screw that controls the boost (and using 150/200 triptane fuel blend)
so the '3000 hp for 3 minutes' Wasp Major 4360 gave him nearly 4500 hp for 70 minutes
thousands were then made eg giving 3500 hp on 115/145 or 108/135 for airline, cargo, and tanker use
and 3800 hp turbocharged for B-36s
(there were designs with VDT (recovery turbine before turbo before exhaust thrust) for 4300/4800 hp + thrust)
presumably retrofitting C series parts would now make 2800 rpm the rated speed
or a DIY XP-72 ?
afaik the 'exhaust' thrust (no turbocharger) was 20% of crank power at 500 mph/35000ft


and these (2 parts) are priceless
https://www.faaaa.asn.au/heritage-flying-sea-fury/
of course many can emulate the so-called 'torque stall' without change in the propeller torque
this was an essential part of theoretical and practical flight training for 70 years
the underlying issue is we might call differential stall (however that arises)
unless differential stall is desired - we then call this spinning or flick rolling aka snap rolling
in WW1 flick/snap rolling was the only way of rolling - and what we now call rolling was called aileron rolling

propeller torque must be seen as a yaw issue not a roll issue
preventing yaw prevents an uncommanded spin/snap - aileron (roll) inputs can't be assumed to work
yes the RAN could teach SF pilots whatever it pleased for its purposes

the SF has insufficient pitch authority for 3 point landings with conventional (runway) landing power and methods

[J.A.W.]

Higher boost + ADI = increased exhaust efflux, thus individual ejector stubs for Sabre VII:

[J.A.W.]

...the British experts having been consistently wrong
like the experts who knew that an exhaust turbine couldn't recover power without 'back pressure...

Not really T-C, it was a matter of proper design/testing/production, so with the
RAF's Mk III Merlin-Mustangs being 'over-boosted' to +25lb for anti-V1 cruise-missile
sorties being duly fitted with less restrictive LF Spitfire-type open exhaust stubs,
both to gain a bit of speed, & since testing showed the original items blowing apart
under stress, (an idea picked-up for standard use in the factory high-boost P-51H).

The high-boost Allison-powered P-82 'Twin Mustang' also featured
24 individual exhaust stubs, (something the R/R V12's didn't, due to
the in-head 2-1 bifurcation of the 4V poppet-valve exhaust ports).

It was well known that the 'saxaphone' exhaust manifolding
applied to flame-damp the Merlin for night-ops cost speed,
& that daylight Mosquitos (& for night-ops on anti-V1 duties)
would very much benefit from a more efficient system too:

http://www.wwiiaircraftperformance.org/ ... k290-b.pdf

Meanwhile, Bristol also slapped an inefficient/primitive type
of cowling-nose ring-collector exhaust plus high-drag tail-pipe*
to its night-ops Hercules engines, even though it was also well known
that sleeve-valve designs didn't emit much of an exhaust flame-glow,
& knowing BMW had already developed a much-more efficacious set-up
on its own (poppet-valve) radial, to be (eventually) emulated by Bristol...

*Perhaps it was 'Air Ministry' bumpf which insisted on it?

[J.A.W.]

With kind permission of member here 'snowygrouch', noted above, & from his book
'The Secret Horsepower Race', are these graphs of RAE/Napier estimates of probable Sabre
performance on 100 octane avgas, 1stly comparing an experimental turbo set-up @ +10lbs,
plus the later addition of ADI to increase boost/power output with the mech-supercharger.

[Tommy Cookers]

...the British experts having been consistently wrong
like the experts who knew that an exhaust turbine couldn't recover power without 'back pressure...

Not really T-C, it was a matter of proper design/testing/production .....
+25lb for anti-V1 cruise-missile .... fitted with less restrictive LF Spitfire-type open exhaust stubs ....

'expertise' had Schneider Trophy planes (and Spitfires) laterally exhausting via 6 flush openings (no drag but no thrust)
followed on the Spitfire eg early 1937 by a laterally-ported cover/sleeve over of the 6 flush/almost-flush openings
(Oestrich's 1932 NACA Misc.Paper No 34 had first proclaimed the thrust available by rearwards exhausting)

till 1937 when Dorey and Pearson (not Hooker) of R-R produced the conspicuous 'ejector exhaust' for the Merlin
giving 70 lb thrust (author Price implies the cost in drag was small) at 300 mph (without loss of crankshaft power)
in Sept 1937 flight tests showed that the ejector exhaust increased the Spitfire max speed from 348 mph to 360 mph
(Hooker said prop efficiency was c.70% - Merlin had 840 lb thrust at ? mph vs Gloster's experimental jet plane 800 lb)

conspicuously the EE had 3 separate elements each combining and directing backwards exhaust from 2 adjacent cylinders
conspicuously the EE was characteristic of the 'Battle of Britain' - but it then conspicuously disappeared from production
promptly replaced by 6 stub systems - still of course called ejector exhausts
with Merlin unanticipated progress outmoding that anticipated ie the simple 40 series distancing the lavish 20 series

RJ Raymond's article in AEHS gives Hooker's view that (later) EE gave 13 lb exhaust thrust per 1000 crankshaft hp
NACA Pinkel's April 1941 view was 16% 'free bonus' exhaust thrust with prop efficiency 80% (at 350 mph 20000' 45" Hg)
Flight said DH Hornet exhaust thrust c.500 mph equivalent to 30% of crankshaft power (fewer % of prop power)
NACA report 765 in 1943 predicted 27% at 500 mph and MAP .2 bar over ambient

Hooker said was little of no exhaust thrust with turbocharging (unless at high altitude) - so EE was the best
the P-47J gave 23% 'exhaust thrust bonus' (if 80% prop effic) from turbo exhaust only - ok at 35000' and 500 mph
consistent with RJR giving NACA's paper showing EEs as better at low altitude than the turbocharged engines

correctly speaking none of these (3 or 6) EE /jet stub systems were restricted ..... ie
mean exhaust pressure was never increased above ambient - as exit nozzle area was at or above the critical area
(below critical area increase in exhaust pressure loses more in engine power/health than any gain in exhaust thrust)
yes critical area changes somewhat with MAP and ambient pressure ie altitude

though (it's said)? unlimited racers (props/gears non-ideal at extreme power) use 'constricted' exhaust exits/nozzles
sometimes to increase exhaust thrust and reduce engine power (relative to the potential otherwise)

and ... are tuned length exhaust systems (ie some free supercharging) viable in these low-altitude radials ?

a 3 EE system would suffer with the increased exhaust durations used later in WW2 (eg Merlins 288 deg)
because V12s have 8 of the adjacent cylinders exhausting at 240 deg intervals
the 12-stub Sabre would have had some limitations - this maybe a motivating factor for 24 stubs
(NACA compounding Allisons coupled non-adjacent exhausts 1+6 2+5 3+4 to get all 12 exhausting at 360 deg interval)
the original Typhoon had 4 3-1 manifolds each side
and extreme durations (via DI of course) then became the hot ticket eg the Wasp Major/4360
eg NACA Technical Note 1475 'Investigation of Valve Overlap Scavenging'

seemingly ....
the extractor exhaust was so named because in the 1930s the USA sought to improve air cooling via ....
multiple pipes exhausting backwards each extracting air (bounded by augmenter tubes) from around the engine
clusters of 3 pipes from chosen cylinders were an improvement
then the pipes were put in the flanks of the fuselage within common integral bounding (ie augmenting) ducting
in 1939 the NACA's Benjamin Pinkel saw NACA extractor reports - in Germany
then came the 'Zero' , 190 , P-42 etc etc

Pratt & Whitney made for the military a Sabre-in-all-but-name and a similar larger H3730
but they stopped these, paid back every dollar, and showed that eg the Wasp Major had less drag anyway
the anticipated huge bombers with buried engines were supervened by actual big bombers with thinner wings
and 115/145 etc

[J.A.W.]

P & W's in-house attempt at a Sabre-clone was a failure, as was R/R's,
just like Chrysler's own V16, in reality amounting to: 'too much, too late',
(with British plans to have Chrysler produce the Sabre canned - due to the
priority of the B-29 program & thus the need for a serviceable big Wright radial,
- available in big numbers), but Bristol built fairly few equivalent Centaurus radials,
(did any of the ahem - big Bristols - see actual wartime combat-squadron service?).

Even the Germans were unable to emulate the Sabre's performance,
not least as a practicable/operational service unit, with their 'ersatz'
24 cylinder (double V12) also being troublesome, ( nor did the Americans ever
use their Allison iteration of this scheme, in anything but prototype aircraft).

The huge 'corn-cob' 28 cylinder 4-row P & W radial proved a bit too demanding
for most commercial users, & later likewise problematic in Reno race-tune.

Here is an early high-speed Sabre streamline-paired 6-into-1 exhaust manifold,
(interestingly enough that particular engine later saw wartime duty in a Typhoon,
& I'd bet the Wingco flying most likely nabbed that one for his 'personal use')...