Last & Best of the Piston Engine Fighter Aircraft.

[J.A.W.]

with the benefit of the Spitfire experience emerged a rather standard type of wing design - eg on the Firefly and the Tempest
as the Spitfire wing was not of a 'laminar flow' section neither was the Tempest's

and I am not the only person who has referred to the Mustang's as a so-called 'laminar flow'
and of course 'laminar flow' benefits do not imply compressibility benefits
https://www.aerosociety.com/media/4953/ ... itfire.pdf

T-C, in the context of 1940`s era 'laminar-flow' wings..
it is technically correct to assert that they really weren't - in practical usage, vs the theoretical values..
they were more of an 'honest attempt' - at getting the concept into use..

& in the event, such wings of max thickness @ about 40% chord & very fine finish from the leading edge back..
in service, certainly did offer significant drag reduction characteristics/benefits..

Hawker's "high speed wing" ( 'laminar-flow') profile endowed the Tempest..
with a 20+ mph speed advantage over its thick winged predecessor the Typhoon,
while using the same power, right across the range, as well as significant improvement in the roll rate..

Ironically, while the Tempest adopted a semi-elliptical planform shape, vs the straight-taper Typhoon,
the Supermarine designers went the opposite way, & their 'laminar-flow' Spiteful wing was straight-taper.

US fighters (except the Mustang) needed additional palliatives in the way of 'dive-flaps' to cope..
with their fairly low Mach limitations*, & not become 'terminal' in high-speed dives..vs 109/190..

The Spitfire needed/recevied a new, sturdier wing, for its final 20 series iteration..

*the dreaded 'compressibility zone' - loss of control, problem.

[Tommy Cookers]

[quote=J.A.W.].......Hawker's "high speed wing" ( 'laminar-flow') profile endowed the Tempest..[/quote]

you should stop writing that the Tempest wing was laminar-flow because that means it had a 'laminar-flow' section
it did not have such a section and should not be called laminar-flow
you need to stop imagining that a high-speed section and a laminar-flow section are 2 names for the same thing - they are not
the Spiteful/Seafang wing which of course came after the Tempest was the first (and only ?) British wing to have a laminar-flow section

my accidental discovery that you in another forum have written as quoted above was the reason for my writing the previous post
you do not seem to have read or understood the reference material that I linked

[J.A.W.]

.......Hawker's "high speed wing" ( 'laminar-flow') profile endowed the Tempest..

you should stop writing that the Tempest wing was laminar-flow because that means it had a 'laminar-flow' section
it did not have such a section and should not be called laminar-flow
you need to stop imagining that a high-speed section and a laminar-flow section are 2 names for the same thing - they are not
the Spiteful/Seafang wing which of course came after the Tempest was the first (and only ?) British wing to have a laminar-flow section

my accidental discovery that you in another forum have written as quoted above was the reason for my writing the previous post
you do not seem to have read or understood the reference material that I linked

'fraid you are incorrect in your assertions there, T-C..
I do check the links you cite, as my computer is quite capable of enabling such tasks..

& as per the Tempest wing meeting the criteria for 'laminar-flow' as it was known..
with its maximum thickness at 37.5% of chord, it most certainly does, & is duly acknowleged as such:

http://www.flight-manuals-online.com/pr ... er-tempest

& for a period view of Hawker's "high-speed wing" profile:

http://www.wwiiaircraftperformance.org/seafury-x.pdf (see 2nd column, P.115 of the article)

J.D. Anderson, on P.352 of 'A History of Aerodynamics: & its Impact on Flying Machines' writes:

"...laminar-flow airfoils would enjoy success: Those airfoil shapes with the maximum thickness far back
from the leading edge... were found to have excellent high-speed characteristics."

[J.A.W.]

Here below is a 'Flight' review of Napier aero-engines..

Check the remark re: Sabre Mk VIII, a development "Intended for the Hawker Fury",
& good for "Nearly 4,000 hp."

If it indeed flew in VP 207, which was still being test-flown in 1948, despite the RAF being notably
uninterested - in new piston-engine powered fighters.. it might make useful reading, topic-wise..

I wonder where those Hawker flight test results are - now?

http://www.flightglobal.com/FlightPDFAr ... 200880.PDF

[J.A.W.]

Another 'Flight' feature, from 1946 - presenting British fighters..
@ the apotheosis of the piston aero-engine, & on the cusp of the turbo-jet take-over..

http://www.flightglobal.com/pdfarchive/ ... 00517.html

[Tommy Cookers]

[quote=J.A.W.]
& as per the Tempest wing meeting the criteria for 'laminar-flow' as it was known..
with its maximum thickness at 37.5% of chord, it most certainly does, & is duly acknowleged as such:
http://www.flight-manuals-online.com/pr ... er-tempest
& for a period view of Hawker's "high-speed wing" profile:
http://www.wwiiaircraftperformance.org/seafury-x.pdf (see 2nd column, P.115 of the article)
J.D. Anderson, on P.352 of 'A History of Aerodynamics: & its Impact on Flying Machines' writes:
"...laminar-flow airfoils would enjoy success: Those airfoil shapes with the maximum thickness far back
from the leading edge... were found to have excellent high-speed characteristics."[/quote]

none of these shows that max thickness at 37.5% necessarily denotes a 'laminar flow'section
eg symmetrical or semi-symmetrical airfoils would often go to this eg the (British) P 2040 was 40%
the symmetrical section in the source below has about 12 NACA foils not coded as laminar with max t at 40-50%
symmetricals were used by eg the B-17 and Vultees used NACA 64-009 tip and 64-018 root which have max t at 40% chord
NB ok these, being 5 digit 6 series have a revised profile deemed as laminar (6 digit 6 series are not laminar)
http://www.airfoiltools.com/search/inde ... unt%5D=136
this source matches NACA 1412 (called semisymmetrical not LF on the Bellanca Decathlon) with the Tempest H1414 at the 61% semispan
http://www.airfoiltools.com/airfoil/det ... aca1412-il

anyway for all airfoil designs interaction of aerodynamic and structural effects at high speeds demands maximum stiffness towards the rear
ie all high-speed airfoils will tend to have their max thickness (and stiffness) well back
eg the Spitfire 23 wing had its front region 'drooped'/thinned
the B-24 had in its Davis airfoil a rearward max thickness but was not at the time claimed as LF and unrelated to the NAA/NACA LF

you have not shown a source from those times that supports your interpretation
afaik there has been nothing eg in Beamont's writings regarding the Tempest's H1414 and LF

recent NASA general-interest history seems to claim for the Mustang wing a vague and broad merit rather than LF as such
WW2 Germany had plenty of Mustangs but seems to have invented rather different airfoils for similar applications
ok many later planes used these NACA LF airfoils

LF will always be greater at lower (than WW2 fighter) Re Nos
so became common in 'light' aircraft eg Piper Cherokee 65-415 and many others eg Pitts S-2A 63A015
max thickness % chord was around the implied 'magic' 37.5%

http://www.pprune.org/tech-log/438359-f ... oil-2.html
http://www.pprune.org/tech-log/438359-f ... rfoil.html
https://aviation.stackexchange.com/ques ... w-behavior
http://m-selig.ae.illinois.edu/ads/aircraft.html
https://en.wikipedia.org/wiki/Supercritical_airfoil

btw the Tempest airfoil is suggested as NPL origin - and seems wrong in 14% thickness being impossible at 37.5% semispan (14% is root thickness)
and max t position has been quoted as 37.5% but is 38.3% - the 37.5% is the span

here is a 6 digit 6 series non-laminar flow airfoil with a max t at 40% chord
http://airfoiltools.com/search/index?m% ... yt0=Search

[J.A.W.]

Actually T-C, as a matter of fact, the Tempest wing profile does conform with 'laminar-flow' pattern..
& this is, indeed - widely acknowledged.

http://www.airvectors.net/avcfury.html

Those readers interested in the subject here, can see for themselves, as graphically shown below.

1,Typical 'laminar-flow' wing profile compared with period 'ordinary' type:
http://www.allstar.fiu.edu/aero/images/fig14.gif

2, Tempest profile:
http://www.airfoiltools.com/airfoil/det ... empest1-il


& here below, from 'Flight' in 1947, a data table list of Britsh piston aero-engines:

http://www.flightglobal.com/pdfarchive/ ... 01491.html

[Tommy Cookers]

a matter of fact ?

the Tempest airfoil is provisionally attributed by airfoiltools to the (British) NPL

and according to 'ARB' Darrol Stinton's book wouldn't be deemed laminar flow unless generated from the special NACA recipe - their 6 series 5 digit code
presumably this excludes any combination available within that code not chosen or at least approved by NACA
and the British (and Hawker work beginning in Mar 1940) no doubt considering the Mustang airfoil and wing but directed at eg the Tempest

this may be the reason no official or contemperaneous records etc of the Tempest seem to include the term 'laminar flow'
(yes, it would be interesting to consider case of the Spiteful LF airfoil)

here is a non-laminar (6 series 6 letter) NACA airfoil with max t at 40% chord
http://airfoiltools.com/search/index?m% ... yt0=Search

Spiteful aerofoil (described as laminar effect in outer part of wing) in this report p21 - max t at 50% chord
http://naca.central.cranfield.ac.uk/rep ... m/2535.pdf

regarding the credibility of unattributed statements that appear in one book, followed by repetitions elsewhere constituting 'matters of fact' ....
we should remember the relatively recent books etc screaming about eg unsupercharged P-38s etc supplied to the British
this nonsense coming from a 1950 USAF report that sloppily wrote unsupercharged when it meant non-turbocharged ....
only when used 40 or 50 years later by some fools who thought they were authors

[J.A.W.]

Well T-C, disregarding 'red herring' diversions about turbo-superchargers, or lack thereof..
& getting back to the facts about the Tempest wing-form developed for Hawker, by NPL in Britain,
NPL certainly knew the theoretical design basis of 'laminar-flow' - was inherent in their profile..

As noted in this period 'Flight' article: http://www.flightglobal.com/pdfarchive/ ... 01124.html

But 'laminar-flow' - as it pertained to the NPL/Hawker 'high-speed wing' as employed on the Tempest, was
not seen as the primary characteristic deemed necessary - in replacing the Typhoon's thick airfoil.

Hawker documentation put it thus:

"The section was however primarily designed for high speed conditions where, owing to the fact that there
are no sharp changes in pressure gradients, the onset of compressibility effects are delayed.
The aircraft is thus able to fly & dive at high speeds without any adverse effect on stability & control."

& British test pilot 'wee winkle' Brown duly demonstrated an instrumented Mach 0.87, in a Tempest V for the RAE.

By contrast, the contemporary users of the NACA 6-series 'laminar-flow' profiles - seemed to want to
'tout' that particular design characteristic, as seen below in the 'Flight' report of the Aussie CAC CA-15:
http://www.flightglobal.com/pdfarchive/ ... 00647.html

[Zynerji]

*need more popcorn*

[J.A.W.]

A well-written piece on the - sadly unwanted in the new jet-age, Sabre-powered Hawker Fury.

https://oldmachinepress.com/2014/10/14/ ... re-powered

Seems a pity that the Hawker works could hold on to its final Hurricane built - for historical reasons..
yet signally failed to preserve - even a single example - of its many Napier Sabre powered machines..
& VP 207, as the zenith of their piston-engined fighter designs to fly - ought to have been a 'keeper' IMO..

[Tommy Cookers]

the introduction of the Spiteful report that I linked establishes an association of (outer panel) 'laminar' (enhancement) with cusped trailing edges
in simple terms the 'laminar flow' designer uses such little curvature on most of the chord he needs concavity at the rear to form a TE
the Spiteful specification was issued in Jan 1943

all aerofoils deemed laminar showed this cusping (concavity) - see Mustang and Spiteful (above report) and .....
the 'next-stage LF' Bell P-63 (NACA 66-116 & 216) and Douglas A-26 (65-215) - see eg airfoil database list NACA 6 digit p 7 and p 6
maximum camber is far back eg 50% chord and the LE looks unusually 'sharp' and flat therafter (relative to conventional high-speed 'foils)
there is always some cusping on the lower surface (varying with camber) and often on both upper and lower surfaces

the Tempest aerofoil/airfoil shown on the airfoil database list beginning T ......
has clearly a less sharp LE, less 'flatness' initially, max camber being around 40% chord - and no cusping
the Tempest specification was issued in Oct 1941

numerically what distinguishes a 'laminar' airfoil (from other high-speed airfoils) is rearwards position of max camber - not of max thickness as claimed

so it seeems clear the Tempest aerofoil was not related to the 'laminar' foils - hence (afaik) no official or otherwise credible source deemed it 'laminar'


regarding the 'LF' airfoils widely taken up by more recent light aircraft - it seems that there's few 'free lunches' .....
LF will according to Stinton always give an inferior Cl max and l:d ratio outside its favoured AoA range
eg rather than use LF, Bellanca used a modified RAF 27 airfoil because of its particularly consistent l:d ratio
a bit like Ferrari fitting traction control because the people who actually buy Ferraris benefit from it

[J.A.W.]

the introduction of the Spiteful report that I linked establishes an association of (outer panel) 'laminar' (enhancement) with cusped trailing edges
in simple terms the 'laminar flow' designer uses such little curvature on most of the chord he needs concavity at the rear to form a TE
the Spiteful specification was issued in Jan 1943

all aerofoils deemed laminar showed this cusping (concavity) - see Mustang and Spiteful (above report) and .....
the 'next-stage LF' Bell P-63 (NACA 66-116 & 216) and Douglas A-26 (65-215) - see eg airfoil database list NACA 6 digit p 7 and p 6
maximum camber is far back eg 50% chord and the LE looks unusually 'sharp' and flat therafter (relative to conventional high-speed 'foils)
there is always some cusping on the lower surface (varying with camber) and often on both upper and lower surfaces

the Tempest aerofoil/airfoil shown on the airfoil database list beginning T ......
has clearly a less sharp LE, less 'flatness' initially, max camber being around 40% chord - and no cusping
the Tempest specification was issued in Oct 1941

numerically what distinguishes a 'laminar' airfoil (from other high-speed airfoils) is rearwards position of max camber - not of max thickness as claimed
so it seeems clear the Tempest aerofoil was not related to the 'laminar' foils - hence (afaik) no official or otherwise credible source deemed it 'laminar'

regarding the 'LF' airfoils widely taken up by more recent light aircraft - it seems that there's few 'free
lunches' .....
LF will according to Stinton always give an inferior Cl max and l:d ratio outside its favoured AoA range
eg rather than use LF, Bellanca used a modified RAF 27 airfoil because of its particularly consistent l:d ratio
a bit like Ferrari fitting traction control because the people who actually buy Ferraris benefit from it

T-C, the Tempest ( then known as Typhoon II) was indeed built to specification F.10/41.
& which, according to D.N. James on P.88 - in 'Hawker an Aircraft Album'
"...stemmed from a desire to eliminate the earlier Typhoon's high speed buffet..."

& if you check the period 'Flight' articles - you can see the NLP diagram clearly shows the same profile..
listed as ' laminar flow' - as the linked Tempest example,
(& the experiments on the P-63 by RAE - are noted there, also).

An interesting note of potential relevance to F1 aero - is in the final page of that article, with an example
of a low-drag, but high-lift (or downforce, - when inverted), 'blown/suction' slot, laminar-flow airfoil..

As for Bellanca & L-F, their 'Skyrocket II' prototype demonstrated the effect of such profile use,
as practical with modern composite ultra-smooth contruction methods, ( confirmed by NASA test),
but alas, fell foul of prohibitively expensive 'liability' issues, so never made 'production'..

www.payneng.com/PDFs/SkyRokt2.pdf

[J.A.W.]

De Havilland also utilised the NPL high speed wing profile designs on the Hornet & Vampire,
& as per the Tempest, they are also currently acknowledged as being of the 'laminar-flow' type.

Here is a period 'Flight' article on the Hornet, which is not only interesting as being of a 'composite' construction..
but also certainly deserves inclusion in this thread, among the 'last & best...' : http://www.flightglobal.com/pdfarchive/ ... 00152.html

[J.A.W.]

Another remarkable period 'Flight' article - is this translation of a startlingly frank 'Nazi-science' aero-tech review,
(from 1942), which includes matters such as 'laminar-flow', direct injection, & 'meredith effect'..
(& a very NPL/Tempest-like wing profile diagram, for illustrating the L-F process!).

http://www.flightglobal.com/pdfarchive/ ... 00666.html

Anyone who is interested - can compare an overlay of Mustang/Tempest wing profiles,
& see how just how similar they are - for themselves, at the site linked below..
so, once again T-C, clearly - not much "imagining" is required to see the classic 'laminar-flow' shape - in both:
http://airfoiltools.com/compare/

Such an overlay exercise will show that, notwithstanding T-C's emphasis on the lower wing recurve feature..
the Tempest wing profile indeed demonstrates that claims of a "...less sharp LE, less flatness initially..."
actually are - better applied - to the Mustang..