Last & Best of the Piston Engine Fighter Aircraft.

[Tommy Cookers]

Tempest I .... siting of the radiators precluded the available space/usage of the leading-edge for fuel tankage
as fitted to the Tempest V ....

nonsense
all Tempests had fuselage fuel tanks - because unlike the Typhoon there wasn't room in the wing
so engine/prop were shoved half a yard forward to make room for fuselage tanks ....
this forward movement of the cg dictating .....
of course the Tempest's huge fin & rudder .... and .....
the loss of pitch control authority (not stability) at highest Cl (ie lowest airspeeds)
https://aeroscale.net/news/tempest-mk-v ... -oil-tanks

and ....
regarding the Sabre's supposed lower porting/valving losses than conventional engine's
(though not so supposed in Robert J Raymond's article) .....
isn't the conventional's (if higher bmep) relatively higher cost in supercharge power .....
largely repaid in the 'pneumatic motor' part of said engine's power ? ..... and .....
entirely repaid in the 'exhaust jet power at high speed' part ? .....
(for good jet power exhaust speed must anyway be raised by outlet restriction ie between cylinder and atmosphere)

[J.A.W.]

Tempest I .... siting of the radiators precluded the available space/usage of the leading-edge for fuel tankage
as fitted to the Tempest V ....

nonsense
all Tempests had fuselage fuel tanks - because unlike the Typhoon there wasn't room in the wing
so engine/prop were shoved half a yard forward to make room for fuselage tanks ....
this forward movement of the cg dictating .....
of course the Tempest's huge fin & rudder .... and .....
the loss of pitch control authority (not stability) at highest Cl (ie lowest airspeeds)
https://aeroscale.net/news/tempest-mk-v ... -oil-tanks

and ....
regarding the Sabre's supposed lower porting/valving losses than conventional engine's
(though not so supposed in Robert J Raymond's article) .....
isn't the conventional's (if higher bmep) relatively higher cost in supercharge power .....
largely repaid in the 'pneumatic motor' part of said engine's power ? ..... and .....
entirely repaid in the 'exhaust jet power at high speed' part ? .....
(for good jet power exhaust speed must anyway be raised by outlet restriction ie between cylinder and atmosphere)

"Nonsense" T-C?

Perhaps you should've checked the real thing, rather than a plastic kitset model?
Since along with Tempest inter-spar wing tanks, another fitment was also made.

Such as the ~30 gal port leading edge tank in the Kermit Weeks collection? See:




I recall reading Luftwaffe test pilot H-W Lerche's account of doing an emergency landing while flying
a captured Tempest, & having to cope with a WWI rotary engine style 'all on, or all off' powered landing
after a throttle linkage failure, & how he'd praised the Tempest's "good natured" controllability.

Furthermore, the Tempest I flew well with the Typhoon fin/rudder, & never required the larger area
which the 'chin' radiator/bulbous radial of the other 'long-nose' Tempest variants needed, albeit flight
trials of a larger area horizontal stabilizer def' offered an advantage - which was indeed worthwhile
being retro-fitted (plus the 4-blade prop) - to Typhoons..

As for exhaust efflux jet-thrust/'nozzle' usage per the Sabre, this was discussed just a few pages back, wherein both the individual ejector stubs - which superseded the paired type - for ADI/boost increases,
& the propensity for the Sabre VI prototype Warwick to lose its skin when subject to the inline row of
hot gasses concentrating the blast in a stream, during high power settings - were duly noted...

[Tommy Cookers]

isn't the conventional's (if higher bmep) relatively higher cost in supercharge power .....
entirely repaid in the 'exhaust jet power at high speed' part ? .....
(for good jet power exhaust speed must anyway be raised by outlet restriction ie between cylinder and atmosphere)

... 'long-nose' Tempest variants ......
... exhaust efflux jet-thrust/'nozzle' usage per the Sabre, this was discussed just a few pages back ....

were there 'short-nose' Tempests ? .... (I think not)

what I claimed here was that exhaust-jet restriction negates the supposed (exhaust side) benefit of sleeve valves
ie if the sleeve valve is less restrictive it's 'bigger' than the poppet valve ....
so the Sabre's restriction for jet effect would need to be relatively greater than would the conventional engine's ....
to increase the mean exhaust speed to the same required speed
given the restriction slightly reduces crankshaft power ......
the loss in crankshaft power would be greater in the Sabre for the same degree of exhaust jet thrust

[johnny comelately]

isn't the conventional's (if higher bmep) relatively higher cost in supercharge power .....
entirely repaid in the 'exhaust jet power at high speed' part ? .....
(for good jet power exhaust speed must anyway be raised by outlet restriction ie between cylinder and atmosphere)

... 'long-nose' Tempest variants ......
... exhaust efflux jet-thrust/'nozzle' usage per the Sabre, this was discussed just a few pages back ....

were there 'short-nose' Tempests ? .... (I think not)

what I claimed here was that exhaust-jet restriction negates the supposed (exhaust side) benefit of sleeve valves
ie if the sleeve valve is less restrictive it's 'bigger' than the poppet valve ....
so the Sabre's restriction for jet effect would need to be relatively greater than would the conventional engine's ....
to increase the mean exhaust speed to the same required speed
given the restriction slightly reduces crankshaft power ......
the loss in crankshaft power would be greater in the Sabre for the same degree of exhaust jet thrust

At the 8 minute mark the comparative exhaust thrust figures are spoken about....
And at the 6:30 mark the Riccardo (sort of) precombustion chamber with stratification

[J.A.W.]

isn't the conventional's (if higher bmep) relatively higher cost in supercharge power .....
entirely repaid in the 'exhaust jet power at high speed' part ? .....
(for good jet power exhaust speed must anyway be raised by outlet restriction ie between cylinder and atmosphere)

... 'long-nose' Tempest variants ......
... exhaust efflux jet-thrust/'nozzle' usage per the Sabre, this was discussed just a few pages back ....

were there 'short-nose' Tempests ? .... (I think not)

what I claimed here was that exhaust-jet restriction negates the supposed (exhaust side) benefit of sleeve valves
ie if the sleeve valve is less restrictive it's 'bigger' than the poppet valve ....
so the Sabre's restriction for jet effect would need to be relatively greater than would the conventional engine's ....
to increase the mean exhaust speed to the same required speed
given the restriction slightly reduces crankshaft power ......
the loss in crankshaft power would be greater in the Sabre for the same degree of exhaust jet thrust

The "short-nose" with chin radiator - is the Typhoon - of course...

The Tempest I prototype - leading-edge radiators with long, yet tapered nose - never did require
or receive extra fin-rudder area additional to its original Typhoon tail, unlike Tempest Mk's II/V/VI.

As for ideas about exhaust-stub gas-flow/jet efflux parametrics, isn't the whole feedback loop
'merry-go-round' between supercharger power demands due to high boost & exhaust thrust
gains - mainly applicable to multi-stage compression optimised for high-altitude performance,
whereas - the effect of adding ADI for lower altitude full-throttle boost is a 'nozzle' mass-flow issue?

Per sleeve-valve/Sabre characteristics, the data gained from the Napier flight-testing of the turbo
Typhoon might be revealing - even per the basic comparison shown in the graph (sourced via the 'snowygrouch' literature review collection) - several pages back in this thread.

[johnny comelately]

Noticed Harry Weslake's name in this.
Had forgotten about his involvement with Rolls Royce Merlin and then others, eg,:
"Weslake would also work as a consultant with Chrysler, developing a wedge head combustion chamber for their RB engine which was first fitted as Stage II in 1963.[22] In 1953, Weslake were given a patent for a unique layout of having valves provide a weak and rich mix to enable high compression ratios to be used without pre-ignition or pinking of the charge taking place. This was a precursor to Honda's CVCC engine which appeared in February 1971, five month's after the Weslake patent expired"
Anyone know about the valves mentioned here?
https://en.wikipedia.org/wiki/Weslake
Also, a question for the aficionados: re the fluid coupling for the supercharger drive, my knowledge is that they lock up with revs, is this how they worked on these fighters?

[J.A.W.]

Fluid flywheel is a more basic 'clutch-type' coupling than the torque converter, lacking
the extra turbine fluid redirection components which cause a variable torque function
and thus a defacto gearing capability.

Ironically, the 'lock-up' device is a mechanical clutch addition to the T.Q.,
which acts to prevent needless slippage in top-gear 1-to-1 engine crankshaft
output/transmission shaft cruising speed - which improves efficiency lost in
energy wastage via rpm-final drive gearing loss/heat-producing slippage...

WWII aero-engines did not feature a T.Q. as such, & the oil pressure/slippage/shock suppression
factors inherent in the fluid flywheel drive was deemed sufficient by some, but not by others.

The turbocharger driven by exhaust gases as a 'working fluid' was a similar concept, as well.

(Again, do take the youtube presentations by 'Greg' too - with a descent dose of NaCl, rather than
accepting his views at face value - as if they've been carefully parsed/fact-checked - for validity).

[J.A.W.]

T-C, if of interest, the Tempest 'laminar-flow' wing is again duly noted - within a SAE journal paper written
by David A. Lednicer on WWII-era aerodynamics linked below - while considering Bell's P-39/P-63 fighters.

"In 1942, the Hawker Typhoon was redesigned with a new wing, incorporating laminar flow airfoils,
as the Hawker Tempest."

https://www.researchgate.net/publicatio ... _Kingcobra

[Tommy Cookers]

... WWII aero-engines did not feature a T.Q. as such, & the oil pressure/slippage/shock suppression
factors inherent in the fluid flywheel drive was deemed sufficient by some, but not by others ....

great numbers of German engines had superchargers driven by (non torque-multiplying) fluid couplings

varying the quantity of fluid in the coupling through the flight varied the slip&torque developed by the coupling so ....
the supercharger speed increased with altitude so regulating at the required boost regardless of altitude
presumably with less throttling than many conventional engines used to regulate boost at low altitudes

the German engines were relatively large displacement/low boost so their supercharger powers were relatively small


I look forward to someone showing the wording and source of Mr Lednicer's supposed position on the Tempest airfoil
the P-51 airfoil was chosen shortly after the Tempest's - maybe 2 years before the P-63's airfoil was available to choose

[J.A.W.]

That "someone..." could be you, T-C, perhaps?

Since I expect that if you send an email to D.A. Lednicer with your query,
via his published contact address, you'd likely get a considered reply...

If I was to put a wager on it, most probably it'd be based on historical NACA 'L-F' profiles
being duly developed post-consultation with NPL's B. Melvill-Jones, who'd presented 'L-F'
findings in the inaugural 'Wright Brothers Lecture' at Columbia University on 17/12/37.

(You'd recall from earlier in this thread, S. Camm utilised such NPL profiles in production of
the 'Hawker high-speed wing' per Tempest/Fury, replacing 'thick' NACA types - used earlier.)

[J.A.W.]

...I look forward to someone showing the wording and source of Mr Lednicer's supposed position on the Tempest airfoil
the P-51 airfoil was chosen shortly after the Tempest's - maybe 2 years before the P-63's airfoil was available to choose...

Here's another D.A. Lednicer aerodynamic appraisal of some WWII piston-engine fighter aircraft:

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

(Should you wish to contact him T-C, he is currently posting as 'Aeroweanie' over at https://ww2aircraft.net )

[J.A.W.]

Here's a vid showing a well-financed effort by a mob in Canada restoring a Tempest Mk II,
(they appear a bit more enthusiastic than skilled research-backed so 'fingers crossed', IMO).

However the spaces forward of the wing spar utilized for the fuel tank/oil-cooler (port/starboard resp')
& engine intakes are clearly shown, as it was applied to the later production Tempest variants Mk II/VI.

[Tommy Cookers]

... most probably it'd be based on historical NACA 'L-F' profiles
being duly developed post-consultation with NPL's B. Melvill-Jones, who'd presented 'L-F'
findings in the inaugural 'Wright Brothers Lecture' at Columbia University on 17/12/37.
... S. Camm utilised such NPL profiles in production of the 'Hawker high-speed wing' per Tempest/Fury)

it (the Tempest aerofoil) is nothing like NACA LF
implying that Hawker weren't in March 1940 given the NACA LF airfoil that the BPC was then buying in the Mustang
and being unusually thick towards the TE it's rather different also to the NPL LF aerofoil used later on the Spiteful
the rear thickness could alleviate structurally the aeroelastic disadvantage otherwise of this overall thinner wing

the entire Tempest LF myth/legend comes from the 12 (small) page Profile Publications partwork no 197 of c.1967
this being the Francis K Mason 'book' that is the only bibliography source given by all the later legion of authors
Mason gave no source for his LF story
was he also expert on c.63 other aircraft that he described in the 12 small page format for PP ?
and the legion of Tempest authors seems to know and care nothing about any NPL contact with Hawker

Roland Beamont, Eric Brown and Morien Morgan never called the Tempest LF - and that's good enough for me


the E28/39 work showed that NPL's (like NACA's) predictions of LF relieving compressibility and drag were incorrect
but of course their prediction of greatly reduced L/D ratio at large lift coefficients was correct ....
that's why the Spitfire's sustained climb and sustained turn were never equalled
LF was flattered by being mostly used at low altitudes and correspondingly low lift coefficients

[J.A.W.]

... most probably it'd be based on historical NACA 'L-F' profiles
being duly developed post-consultation with NPL's B. Melvill-Jones, who'd presented 'L-F'
findings in the inaugural 'Wright Brothers Lecture' at Columbia University on 17/12/37.
... S. Camm utilised such NPL profiles in production of the 'Hawker high-speed wing' per Tempest/Fury)

it (the Tempest aerofoil) is nothing like NACA LF
implying that Hawker weren't in March 1940 given the NACA LF airfoil that the BPC was then buying in the Mustang
and being unusually thick towards the TE it's rather different also to the NPL LF aerofoil used later on the Spiteful
the rear thickness could alleviate structurally the aeroelastic disadvantage otherwise of this overall thinner wing

the entire Tempest LF myth/legend comes from the 12 (small) page Profile Publications partwork no 197 of c.1967
this being the Francis K Mason 'book' that is the only bibliography source given by all the later legion of authors
Mason gave no source for his LF story
was he also expert on c.63 other aircraft that he described in the 12 small page format for PP ?
and the legion of Tempest authors seems to know and care nothing about any NPL contact with Hawker

Roland Beamont, Eric Brown and Morien Morgan never called the Tempest LF - and that's good enough for me


the E28/39 work showed that NPL's (like NACA's) predictions of LF relieving compressibility and drag were incorrect
but of course their prediction of greatly reduced L/D ratio at large lift coefficients was correct ....
that's why the Spitfire's sustained climb and sustained turn were never equalled
LF was flattered by being mostly used at low altitudes and correspondingly low lift coefficients

T-C, per the quote clip (1st line of your post), I was referring to the P-63, which featured a later type
of NACA 'L-F' profile, the development of which stemmed from earlier work per NPL/NACA data sharing.

The Hawker 'High-speed wing' profile ('L-F' conforming - according to Lednicer & others), was derived
from NPL studies in the UK, while the original Mustang wing was a NAA profile worked up from NACA
research, it is incorrect to claim one was directly related to the other, (except from a basis of NPL
data exchange with NACA in the late 1930s), as previously noted...

Of course the practical effect of 'L-F' profiles in high speed regimes meant that the palliatives of
'dive brakes' as applied to P-38/P-47 were not needed by P-51/Tempest, (while the Spitfire did need
significant structural changes to its wing, & was Vne 'placarded' well below 500mph during wartime).

Drag reduction per 'L-F' is a fact, speed/~power-settings/dive-zoom comparisons clearly proved this.

As for the Spitfire's sustained climb & turn performance, this is largely a factor of wing area/power-
to-weight, something the Mitsubishi Type 0 pilots showed the Spitfire Mk V trop-jockeys to their shock
in combat over Northern Australia, no less than FW 190 pilots had proved* that in air-combat evolutions
with Spitfire V's over the English Channel that mere turning contests were not a be & end all, either...

*Just as that AFDU Typhoon VS Spitfire V combat trial (linked earlier) had also demonstrated.

[Tommy Cookers]

the Tempest Aerofoil is uncusped - (cusping being what we might call slightly slimmed towards the TE)
that's much of how it is "nothing like" the Mustang's
so either NPL and/or Hawker (or NACA) were wrong - they can't all have got the LF benefit

the NACA Mustang type airfoil was replaced by a less ambitious and less demanding type ie on the A-26 and P-63
though Farnborough showed that even a new P-63 wing didn't really work in many areas
the first NA Mustangs of course had special wing surface preparation
Anderson etc says that an 'LF' airfoil can easily have even less LF than has the conventional airfoil....
and LF always gives inferior L/D at high Cl

the Davis airfoil (bought by the military c.1936) seems to have caught out the NACA and caused the LF hype
https://earlyflightera.com/2019/01/25/testing/

again - there's no such thing as a 'low drag' wing - but a different wing drag for every different condition of flight
increased LF tends to produce benefit when that benefit will be least ie in fast straight & level flight at low altitude
(because that's where the wing Cd is unusually low anyway but the rest of the plane's Cd isn't low)
particularly with the 1940-style lowish wing loading of the Tempest
such flying would be better served by a higher wing loading ie smaller wing etc .... but ....
this will tend to reduce protracted climb and turning capabilities particularly at altitude

since WW2 the field is packed with airfoils that just aren't efficient at high Cl (some even having LE bubbles)
packed whether the LF flag is waved or not