Last & Best of the Piston Engine Fighter Aircraft.

[J.A.W.]

the Tempest Aerofoil is uncusped - 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...

We've been over this a couple of times already in this thread, (check page eight), & flight tests
unequivocally demonstrate the reduced drag benefits of the (putative) 'L-F' profiles for
both Mustang & Tempest.

Mustang wings were carefully smoothed even when in 'natural' Al finish - after camouflage paint
schemes were deleted, but the adoption by Supermarine of a straight-taper planform 'L-F' wing
of significantly reduced area - to replace the Spitfire was not a success, the Spiteful/Seafang
were rejected for service whereas the final generation of 20 series Spitfire/Seafire were not.

The final production Mustang was significantly redesigned, but ironically adoption of the later
66XXX-series NACA 'L-F' profile wing wing proved to be one area which didn't offer improvement.

[Tommy Cookers]

the Tempest Aerofoil is uncusped - 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...

We've been over this a couple of times already in this thread, (check page eight), & flight tests
unequivocally demonstrate the reduced drag benefits of the (putative) 'L-F' profiles for
both Mustang & Tempest.

not so
I have now been all over the co-ordinates of the 3 airfoils - that's how I just wrote what I just wrote
you Tempest fans don't seem ever to have done this ....
and ....
reduced drag benefits in one corner of the flight envelope don't make the increased drag elsewhere disappear

Lee Attwood said a zillion times that the Mustang's speed was due to the cooling thrust not to 'LF'-reduced wing drag
(and to its somewhat higher wing loading of course)
other US manufacturers at that time rejected that airfoil as impractical (somewhere in my last linked source)

the Tempest wing question seems to remain unaddressed and unanswered
the Tempest writers have written coffee-table books - they seem to have coffee-table minds

yes we know the Spiteful did have NPL's version and idea of the thing
faster than the Tempest but rejectable as handling no better than the 20000 Mustangs that had been embraced

the writers have 100% ignored the 20 years of racing 'high-speed' ie thin airfoils before WW2
and ignored others using more rearward thickness distributions
structural designers were glad the 'LF' label promoted such - as rearward spar positioning was aeroelastically helpful

the Spitfire people were taken with their LE edge 'single spar' and its 1930 type airfoil choice complemented that
(being rather intended for concentrated loading by struts)
Bellanca knew better than NACA how well it worked at low % thickness - then so did the Spitfire aerodynamicists

[J.A.W.]

the Tempest Aerofoil is uncusped - 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...

We've been over this a couple of times already in this thread, (check page eight), & flight tests
unequivocally demonstrate the reduced drag benefits of the (putative) 'L-F' profiles for
both Mustang & Tempest.

not so
I have now been all over the co-ordinates of the 3 airfoils - that's how I just wrote what I just wrote
you Tempest fans don't seem ever to have done this ....
and ....
reduced drag benefits in one corner of the flight envelope don't make the increased drag elsewhere disappear

Lee Attwood said a zillion times that the Mustang's speed was due to the cooling thrust not to 'LF'-reduced wing drag
(and to its somewhat higher wing loading of course)
other US manufacturers at that time rejected that airfoil as impractical (somewhere in my last linked source)

the Tempest wing question seems to remain unaddressed and unanswered
the Tempest writers have written coffee-table books - they seem to have coffee-table minds

yes we know the Spiteful did have NPL's version and idea of the thing
faster than the Tempest but rejectable as handling no better than the 20000 Mustangs that had been embraced

the writers have 100% ignored the 20 years of racing 'high-speed' ie thin airfoils before WW2
and ignored others using more rearward thickness distributions
structural designers were glad the 'LF' label promoted such - as rearward spar positioning was aeroelastically helpful

the Spitfire people were taken with their LE edge 'single spar' and its 1930 type airfoil choice complemented that
(being rather intended for concentrated loading by struts)
Bellanca knew better than NACA how well it worked at low % thickness - then so did the Spitfire aerodynamicists

C'mon now T-C, never mind you "going over the coordinates" - its time you accepted the evidence,
from 'Tactical Trial Comparisons' through to Lednicer's appraisal, the Hawker H.S.W. did what was
indicated 'on the side of the tin', for a piston engine fighter, just as the 'flight limitations' clearly note.

Regardless of what Lee Attwood may have claimed, British tests of the P-51 with radiator 'blanked off'
still showed a marked effect on speed - due to that low-drag wing, something that Nazi-science duly
confirmed as being in accordance with their own experimental 'L-F' research values - & they too noted
the Tempest wing to be of similar performance, accordingly.

The Spiteful was only faster than its contemporary Napier Sabre powered Hawker fighter - at a much
higher altitude, due to its complex multi-stage supercharged Griffon, but since the RAF only wanted
piston engine powered fighters for A2G work post-war - the Spiteful was naturally overlooked...

In fact the 20-series Spitfires had a heavily revised wing, (which finally gave a Vne equivalent to the
Typhoon, if ~4 years late) to remediate problematic 'aileron reversal/aero-elastic' issues, & even then
only the last Mark 22/24 with the largest (Spiteful-type) tail empennage, actually made service grade,
with the Mark 21's being quickly withdrawn/reduced to spares, (inc' later units, straight from the factory).

[Tommy Cookers]

for the last time !? - the 'low drag' wing gives lower drag when drag is low and higher drag when drag is high ..and btw
there was never a Spitfire wing problem
a problem in IXs was pilots overloading in pullouts - solved by weighting the elevator cables to increase stick force
the wing was 0.85 Mach/450 mph ias down to 20000' (that's c.615 mph true airspeed EDITED)- says AP 1565 PN's
Powles went to 690 mph tas 0.94 Mach and Martindale 606 mph tas 0.89 Mach

more usefully ....
https://reports.aerade.cranfield.ac.uk/ ... 826.2/3233 - this pdf is a priceless monument to great work
and it seems to show ....
the British called so-called 'laminar flow' aerofoils 'low drag' aerofoils
so-called critical Mach was rather arbitrary and so could be safely exceeded in the Spitfire (and why)
the view then that (LF) airfoil design was the answer to compressibility (not as emerged structural design)
.... there is only 1 plot showing or mentioning the Tempest aerofoil (this plotted with the Spiteful's)

https://lin-web.clarkson.edu/~pmarzocc/ ... series.pdf
seems to show that the NACA 'laminar flow' airfoils were in many ways just poor
(and NACA had just invented airfoils with max thickness far forward)

https://ww2aircraft.net/forum/threads/w ... 177/page-2
jabberwocky's post Aug 20th seems to show ......
a Hurricane with 'LF' had 26% less drag at 0.1 Cl
P-63 waviness-rectified to 1 in 2000 had lower drag (than conventional airfoils) 0.1 Cl to 0.5 Cl - but more otherwise
(ex factory its drag at 0.1 Cl was worse than the conventional)

a lift coefficient of 0.5 is a cruising coefficient - not a fighter coefficient
'LF' aerofoils had higher Cd (than conventional) when flown fighter-style - and their max lift coefficients were lower
the Mustang and Tempest and later fighters - all were 'half-a-plane'
largely they got away with this because of the lower altitudes then used .... but ....
the big benefit was to range issues - 'LF' reducing drag relatively more at cruise speed and cruise Cl (than at max)
Sabre-powered planes wouldn't benefit from 2 stage supercharging at some altitudes where Merlin-powered would
evaluations of new planes eg Tempest & Mustang were in part defensive campaigns to build confidence .....
ok zoom climb rate is an amplification of their marginally greater speed - but zoom is brief ..... and ....
a Spitfire pilot would always have fancied a new Spitfire's chances against them

EDIT & NB in those days a zoom was a dive followed by a zoom climb ... said ....
Sqdn/Ldr Wade OC Flying AFDU here www.wwiiaircraftperformance.org/sl-wade.html

maybe we should liken the Tempest to the 1000cc Moto GP 4-stroke - and the Spitfire to the 500cc Moto GP 2-stroke

[J.A.W.]

for the last time !? - the 'low drag' wing gives lower drag when drag is low and higher drag when drag is high ..and btw
there was never a Spitfire wing problem
a problem in IXs was pilots overloading in pullouts - solved by weighting the elevator cables to increase stick force
the wing was 0.85 Mach/450 mph ias down to 20000' (that's c.520 mph true airspeed) - says AP 1565 Pilot's Notes
Powles went to 690 mph tas 0.94 Mach and Martindale 606 mph tas 0.89 Mach

more usefully ....
https://reports.aerade.cranfield.ac.uk/ ... 826.2/3233 - this pdf is a priceless monument to great work
and it seems to show ....
the British called so-called 'laminar flow' aerofoils 'low drag' aerofoils
so-called critical Mach was rather arbitrary and so could be safely exceeded in the Spitfire (and why)
the view then that (LF) airfoil design was the answer to compressibility (not as emerged structural design)
.... there is only 1 plot showing or mentioning the Tempest aerofoil (this plotted with the Spiteful's)

https://lin-web.clarkson.edu/~pmarzocc/ ... series.pdf
seems to show that the NACA 'laminar flow' airfoils were in many ways just poor
(and NACA had just invented airfoils with max thickness far forward)

https://ww2aircraft.net/forum/threads/w ... 177/page-2
jabberwocky's post Aug 20th seems to show ......
a Hurricane with 'LF' had 26% less drag at 0.1 Cl
P-63 waviness-rectified to 1 in 2000 had lower drag (than conventional airfoils) 0.1 Cl to 0.5 Cl - but more otherwise
(ex factory its drag at 0.1 Cl was worse than the conventional)

a lift coefficient of 0.5 is a cruising coefficient - not a fighter coefficient
'LF' aerofoils had higher Cd (than conventional) when flown fighter-style - and their max lift coefficients were lower
the Mustang and Tempest and later fighters - all were 'half-a-plane'
largely they got away with this because of the lower altitudes then used .... but ....
the big benefit was to range issues - 'LF' reducing drag relatively more at cruise speed and cruise Cl (than at max)
Sabre-powered planes wouldn't benefit from 2 stage supercharging at some altitudes where Merlin-powered would
evaluations of new planes eg Tempest & Mustang were in part defensive campaigns to build confidence .....
ok zoom climb rate is an amplification of their marginally greater speed - but zoom is brief ..... and ....
a Spitfire pilot would always have fancied a new Spitfire's chances against them

maybe we should liken the Tempest to the 1000cc Moto GP 4-stroke - and the Spitfire to the 500cc Moto GP 2-stroke

Only "...for the last time... T-C - if you are prepared to finally grasp the empirical/experiential - evidence-base...

Whatever figures may have been noted by PRU-type Spitfire pilots who survived a dive well beyond 'placard' limits
(in out of control dives), the fact remains - these were not practicable fighter-tactic performances - & likely they
were lucky to survive the aero-elastic overstrain, as a consequence (S/Ldr Martindale was 'gonged' with a DFC?).

As I have noted previously in this thread, Tempest 'Pilots Notes' showed ASI/height 'limitations' well in excess of
the Spitfire, (& were confirmed by wee 'Winkle' Brown in RAE Mach-meter tests, as well by actual combat reports),
just as P. Clostermann duly remarked regarding a Spit XIV which had emulated the Tempest's high-speed dive in
a (successful) hot pursuit of a Nazi turbo-jet Arado 234:

"...his poor Spit's wings were buckled like a concertina, all the paint had come off the surfaces,
the rivets had sprung and the fuselage was twisted. Good for the scrap heap!"

Merlin Spitfires could not match a Mustang bomb-load (not even the smaller main-wheel P-51H) despite greater
wing area/lower wing loading, nor keep up with a Mustang in Vmax/Vne at any altitude, & this enabled the Mk III
Mustang to hunt Nazi V1 cruise-missiles heading for London much more effectively, despite "light armament",
(albeit nowhere near as efficaciously as the Tempest, with a Sabre-given ability to maintain high power-settings
plus 4 x 20mm cannon aimed via a 'HUD' gunsight).

One Typhoon Sqd was reserved by ADGB for V1 duties, but with that thick NACA profile wing - certainly they did
better sent on 2nd TAF attack sorties, esp' once its Sabre was armoured, & also given the Tempest's larger tailplane
& 4-blade prop, (though remarkably, one rocket-firing Typhoon did down a V1 by dint of air-to-air missile use).


Perhaps T-C, if you checked some of the memoirs written by 'aces' who flew combat sorties in Spitfire/P-51/Tempest
you'd be forced to revise your opinion based on expert evidence as to which fighter was the most potent A2A machine.

[johnny comelately]

[Tommy Cookers]

1 ... PRU-type Spitfire pilots who survived a dive well beyond 'placard' limits (in out of control dives) ...
they were lucky to survive the aero-elastic overstrain, as a consequence (S/Ldr Martindale was 'gonged' with a DFC?).

2 .. Tempest 'Pilots Notes' showed ASI/height 'limitations' well in excess of the Spitfire ...

3 ... Merlin Spitfires could not .. keep up with a Mustang in Vmax/Vne at any altitude ....

4 .... which fighter was the most potent A2A machine.

each of the above-quoted points is incorrect

there were no actual ASI/height limitations other than the speed the aircraft could actually reach
the 'placard' limits eg 1942 etc Spitfire IX Pilots Notes were 0.85 Mach 450 mph indicated (ie 615 mph true) at 20000'
these limits are common to IX XI and XVI (PRs had blunter noses and bigger wing tanks - so weren't easier)
Martindale had huge g as prop etc broke off due to rpm fault - but never any aeroelastic misbehaviour
158 pages show a dived Spit (it had less drag over 0.67 M) was therefore faster than a dived (PR or fighter) Mustang
all such flights eg the American's own flights of course were also 'over the placard limits'

Mustang Vne is 0.77 Mach and 505 ias at 9000' (c.420 ias at 20000' - that is just under 600 tas)
yes the 1944 RAF PNs simply give 505 ias regardless

so yes in some situations Mustangs went faster than any Merlin-engined Spitfires could have done ....
but also vice-versa in some other situations of course
any plane at speed can be over-stressed by pilot action
Mustangs & the Spitfires with rear tanks were prone to reduced stick force with 'g' eg in zoom climbs (surprised ?)

yes I say the Mustang was (like the Tempest) 'half a fighter plane'
neither is fast enough to justify eg its poor turning over the wide speed range
due to the so-called LF wing - which gives less lift and except at the higher speeds gives increased drag

[J.A.W.]

1 ... PRU-type Spitfire pilots who survived a dive well beyond 'placard' limits (in out of control dives) ...
they were lucky to survive the aero-elastic overstrain, as a consequence (S/Ldr Martindale was 'gonged' with a DFC?).

2 .. Tempest 'Pilots Notes' showed ASI/height 'limitations' well in excess of the Spitfire ...

3 ... Merlin Spitfires could not .. keep up with a Mustang in Vmax/Vne at any altitude ....

4 .... which fighter was the most potent A2A machine.

each of the above-quoted points is incorrect

there were no actual ASI/height limitations other than the speed the aircraft could actually reach
the 'placard' limits eg 1942 etc Spitfire IX Pilots Notes were 0.85 Mach 450 mph indicated (ie 615 mph true) at 20000'
these limits are common to IX XI and XVI (PRs had blunter noses and bigger wing tanks - so weren't easier)
Martindale had huge g as prop etc broke off due to rpm fault - but never any aeroelastic misbehaviour
158 pages show a dived Spit (it had less drag over 0.67 M) was therefore faster than a dived (PR or fighter) Mustang
all such flights eg the American's own flights of course were also 'over the placard limits'

Mustang Vne is 0.77 Mach and 505 ias at 9000' (c.420 ias at 20000' - that is just under 600 tas)
yes the 1944 RAF PNs simply give 505 ias regardless

so yes in some situations Mustangs went faster than any Merlin-engined Spitfires could have done ....
but also vice-versa in some other situations of course
any plane at speed can be over-stressed by pilot action
Mustangs & the Spitfires with rear tanks were prone to reduced stick force with 'g' eg in zoom climbs (surprised ?)

yes I say the Mustang was (like the Tempest) 'half a fighter plane'
neither is fast enough to justify eg its poor turning over the wide speed range
due to the so-called LF wing - which gives less lift and except at the higher speeds gives increased drag

I'd suggest a closer look at A. Martindale's test Spit, post flight. It is bent out of shape, inc' wings.

IIRC, the Mk XI (PR) Spitfire utilized avoidance/evasion 'combat' tactics of attempted intercepts at
high altitudes by means of high-speed shallow dives, & thus, as such was used in high-Mach
research accordingly - esp' since its wing was reinforced - in an early version of 'wet-wing' tankage
for long-range, & lacked the fighter fitments inc' flat-panel windscreen, & cannon-caused - large
external 'lumps & bumps' - all of which tended to increase drag.

(PR Mosquitos were AFAIR, about the only Merlin-powered WWII aircraft to keep up with Merlin-Mustang
speed/power-settings when fitted with engines of equivalent altitude performance, fighter Mk Spitfires could not)

For low-level PR, the Allison-powered Mustang was preferred, & when these were no longer available,
Merlin-Spitfires were not used to replace them, Griffon-engine Mk XIVs were, but proved less satisfactory.

As for being "half a fighter plane", the RAF took all the Mustangs it could get, & (as with its Tempests),
kept them in hand to fight the toughest Nazi opposition (they sent Merlin-Spits to Stalin, & their P-47s
to India/Burma) so you might well need to re-think that erroneous idea, on the evidence base...

Do a comparison of the two NZ fighter squadrons based in Blighty for service with the RAF, 485 & 486;
485 flew Spitfires from Mk V through to Mk XVI, while 486 flew Hawker Hurricane/Typhoon/Tempest.
486 obtained much better A2A results (plus hundreds of V1 missiles), & 485 was subsequently slated
to convert to Tempests too (like 80 Squadron & others), but there were too few Tempests built...

Certainly, at the lower-level 10,000ft & below, both Tempest V(@ 540mph) & Mustang III (@ 505mph),
handily exceed the contemporary Spitfire (@ 470mph) 'limitations' for Vne, per the 'Pilots Notes',
& both accelerated much better in the dive than the Spitfire too, (as did the 109/190 opposition).

As for turning, at high speed the Tempest could readily out-roll the Spitfire,& the Mustang, while it
tended to 'porpoise' at Vne, it would not do a 'Mach-tuck' ever-steepening dive, so unlike P-38/P-47,
did not require the palliative of 'speed-flaps'

Here's a couple of quotes (from memoir written by pilots who'd made 'ace' status) on Spitfires:

From P. Clostermann, re: Sept' 1944, when ADGB (Fighter Command) relinquished Tempests to 2nd TAF:

"The Spitfires were powerless. There was only one Wing of 3 Spitfire XIV squadrons & the rest were
equipped with Spitfire IX's... operated most of the time as fighter-bombers... and the poor Spits had
neither the speed nor the range necessary to force the new German fighters to fight."

From R. Spurdle, C.O. of 80 Sqd on transition from Spitfire IX to Tempest ( & views of the Mustang):

"Our Tempests arrived! Brand new; shining in the sun! They seemed huge after our dainty Spitfires.
But could they go! We found they cruised at almost 100mph faster than the Spits, climbed like rockets,
& dived at incredible speeds... We were delighted... It was a fantastic thrill to have my own squadron
- to lead this bunch of fine pilots flying the best fighter in the Allies' stable...

On sortie No 551 some USAAF Mustangs jumped us. Enraged, I turned on my particular tormentor &
scared him fartless by firing bursts first on one side & then on the other while he twisted & turned
helpless against the far superior Tempest. Formating alongside I shook my fist at the stupid jerk, then
zoomed away. We should've hacked a few down to teach them aircraft recognition. We were sick of
their trigger-happy stupidities."

A. Reed & R. Beamont in ' Typhoon and Tempest at War' commented:

"The Tempest had also proved itself in a series of mock battles carried out over the south of England
in the summer of 1944 against American fighters flown by skilled USAAF pilots. The verdict was that,
flown skilfully, it could see off the excellent P-51D Mustang, while it completely overshadowed the P-47."

[johnny comelately]

Kawasaki Ki-61 Tony, Japan's Answer to the P-38

[johnny comelately]

An interesting piece first up featuring and in a little detail Harry Ricardo's water injection

[Tommy Cookers]

'water injection' WI ....

Ricardo followed-up the WW1 practice (British & French at least) of fuel from crudes naturally high in aromatics ....
establishing the value of so-called benzole as a readily-available ingredient thereafter added in quantity to any fuel
this was before supercharging had emerged
but (thermal) 'cracking' starting c.WW1 had the side effect of increasing aromatics (US crude rather lacking these)
and post-WW1 the US discovered TEL 'lead' and so started to greatly increase their ON

by 1938 the USAAC had as standard '100 Octane' for combat aircraft ....
but most US '100' eg bought by GB for WW2 was at rich mixtures deficient and so below expectations
this was not corrected until 1942 when all 100 became 100/130 - (at least in the ETO - including Germany)
catalytic 'cracking' appeared - (increasing aromatics)
and alkylation appeared - (improving octane via olefins not aromatics)

basically ....
aromatics greatly boost 'octane' at rich mixtures and TEL doesn't greatly
the US didn't like aromatics but were forced to go that way
GB chose to use fuel:air mixture up to 70% rich (rather than WI) to enable high boost for high max power ....
the US chose WI - helping superchargers intended for low boost to work at higher boost and avoiding intercoolers
eg P-47s used WI even through takeoff and DC 6s used WI in airline operation

Avgas grades were .....
'old style' 80/87 91/98 - (conventional in aromatics) .... and .....
'new style' 100/130 108/135 115/145 - (high in aromatics)
today 100LL is 100/130

1960s motor 100 octane was conventional in aromatics so c.100/108

https://www.concawe.eu/wp-content/uploa ... 7-01-e.pdf

[johnny comelately]

'water injection' WI ....

Ricardo followed-up the WW1 practice (British & French at least) of fuel from crudes naturally high in aromatics ....
establishing the value of so-called benzole as a readily-available ingredient thereafter added in quantity to any fuel
but (thermal) 'cracking' starting c.WW1 had the side effect of increasing aromatics (US crude rather lacking these)
and post-WW1 the US discovered TEL 'lead' and so started to greatly increase their ON

by 1938 the USAAC had as standard '100 Octane' for combat aircraft ....
but most US '100' eg bought by GB for WW2 was at rich mixtures deficient and so below expectations
this was not corrected until 1942 when all 100 became 100/130 - (at least in the ETO - including Germany)
catalytic 'cracking' appeared - (increasing aromatics)
and alkylation appeared - (improving octane via olefins not aromatics)

basically ....
aromatics greatly boost 'octane' at rich mixtures and TEL doesn't greatly
the US didn't like aromatics but were forced to go that way
GB chose (very) rich mixture eg 1.7 lambda (rather than WI) to enable high boost for high max power ....
the US chose WI - presumably this helped superchargers intended for low boost to work at higher boost
eg P-47s used WI even through takeoff and DC 6s used WI in airline operation

Avgas grades were .....
'old style' 80/87 91/98 - (conventional in aromatics) .... and .....
'new style' 100/130 108/135 115/145 - (high in aromatics)
today 100LL is 100/130

1960s motor 100 octane was conventional in aromatics so c.100/108

https://www.concawe.eu/wp-content/uploa ... 7-01-e.pdf

1.7?

[Tommy Cookers]

1.7?

now corrected
I meant to write 70% rich
ie 70% richer than stoichiometric

on the armouredcarriers site there's eyewitnesses saying their onboard RR tech rep proclaimed that....
there was per se no time limit on Seafire max boost - other than fuel consumption being literally a vital issue

[tok-tokkie]

If I may post an obliquely related question on this thread.

"Simplify and add lightness"
Google Advanced Search only lists Colin Chapman & he gets credited with coining the phrase.
I have distinct recollection of reading that Glenn Curtiss coined it & had a banner in his design office like that.
Do any of you have similar recollections?

[Tommy Cookers]

If I may post an obliquely related question on this thread.

"Simplify and add lightness"
Google Advanced Search only lists Colin Chapman & he gets credited with coining the phrase.
I have distinct recollection of reading that Glenn Curtiss coined it & had a banner in his design office like that.
Do any of you have similar recollections?

afaik
Bill Stout (designer of the Ford Trimotor ?) said - 'simplicate and add lightness'