Last & Best of the Piston Engine Fighter Aircraft.

[Tommy Cookers]

another plane that was out of control before it left the ground (Spitfire-mockers might note) was the Tornado/Typhoon
(as I've said before a wide-track undercarriage isn't a magic problem-solver)

the Tornado prototype (though designed to do so) couldn't be kept straight during take-off runs (at Langley)
so for 6 months its pilot Phillip Lucas used his own curved path that only met the runway at the point of take-off
(with the Typhoon prototype Mr Lucas avoided this due to immediate in-flight structural failures)

similarly the (production) Typhoon I was in AFDU Report 37 (30.10.1941) said to be ....
incapable of takeoff in a starboard crosswind ('such operations should be avoided')
and the Tempest II required according to CFE Report 30 (5.7.1945) ......
to contain the swing 'the throttle must be opened slowly'
the swing is also mentioned as a factor in night landings
btw too many Mosquito crew died in this situation
(someone wrote that one night group used their own low rpm to avoid this - less 'gyroscopic' torque of course)
(on TV an ex-Mossie Canadian said in prime adspeak that it was - 'unforgiving of those who under-controlled it')

an outstanding read .....
https://vintageaviationecho.com/bf109e/
I flew with a Buchon owner
afaik the 109 'handed' fin that Wiki worship says Buchons kept exactly (or the rudder) was actually realigned to compensate


the Typhoon's conspicuously low stalling speed was presumably because max Cl rises with wing % thickness ....
and the Tempest's benign near-stall behaviour screams out that the aerofoil wasn't really 'laminar'
(and I see that the Wiki gang talks nonsense about Merlin negative g cuts - a restrictor cures rich cuts)

the Tornado (Vulture) engine seems to have been debugged eventually - and 'Merlinised' bore' 5.4" x 5.5" work started
the V was lighter than the Sabre ? - one crankshaft being lighter than two

btw a non-work acquaintance told me the BAe Tornado ADV radar installation mock-up BAe gave to GEC was wrong
ie this was the reason the radar as designed and made by GEC wouldn't fit in the BAe Tornado ADV plane

[J.A.W.]

Yeah, T-C, quite a few lurid assumptions in your most recent post...

A check of operational losses (combat & non-combat) shows that even the
heavily laden Bomber Command Mosquitos had an admirable sortie/loss %,
even compared to the 4-engined 'heavies', let alone other twins...

Same goes for the Typhoon, which in that 1941 AFDU test not only 'burst the Spit=best bubble',
but once fitted with a 4-blade prop, & Tempest tail-plane, showed it was a much more effective
close-support aircraft for the invasion of 'Festung Europa' compared to the vast numbers of Spits
on hand, (& the USAAF turbo-charged fighters) roped into the same job..

Again, the thick-winged Typhoon gave good low-speed lift, but like the Hurricane, was risky
to ditch on the sea, due to the 'stop-dead' characteristics of that fat-profile wing, something
remediated by the Tempest/Sea Fury, which 'skipped' across, just as scale tank-tests predicted.

I'd also suggest that the semi-elliptical planform also offers a characteristically forgiving stall
profile, 'laminar flow' or no, due to the propensity of the shape in giving even stall, span-wise,
with plenty of forewarning. Of course, the Hawker machines were stoutly constructed also,
& allowed a fair degree of 'liberty taking' in flight regime extremis, without falling apart in mid-air..

[J.A.W.]

Here is a link to that 1941 AFDU Typhoon versus Spitfire Tactical Trial:

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

It ironically enough, forewarned the effect of the - soon to arrive Focke Wulf FW190,
(while both the FW 190 & Typhoon were 'rushed' into service, with problems causing
consternation to combat pilots accordingly, the Germans at least, 'got cracking' on
both fixing their issues & mass producing the BMW engine & aircraft in useful numbers)
which came as a shock - to the complacent 'Spitfire Mafia'.

AFAIR, Hawker test pilot Mr Lucas ('Are you free, Mr Lucas?') later admitted the structural
(but not fatal) damage suffered by the (then sole!) prototype Typhoon was his doing,
by 'pushing the envelope' as the American test pilots would put it, & performing evolutions
exceeding the intended test-program profile.

The ill-fated R/R Vulture did behave itself when powering the Typhoon's near-sister Tornado,
but not doing bomber-work (unlike the BMW) & did any X-crank see satisfactory service?

Certainly R/R gave up on it, & tried to have 'a bob each way' by building an oversized,
overweight (& yet unreliable) Sabre-clone which was 'too much, too late', & a scaled-up
'old hand' V12 in the Griffon, which while of similar cubic capacity (~36 litre) to the Sabre,
was unable to match its performance - so, ironically the Sea Fury was accepted for naval
service with the big Bristol Centaurus - although the Griffon was already shipborne in
Seafire & Firefly, thus adding another logistics complication, (& that's just so British, too).

[Tommy Cookers]

the H16 BRM was designed in emulation of the Sabre - but WW2 had no engine rules ....
the only engine 'size' (limiting factors) were the physical dimensions and the weight
the Sabre was 'big'

all planes have less thrust during the take-off roll than at the point of take-off and in initial climb
because the prop's conversion of mechanical power to thrust increases with airspeed
rushing towards WOT gives more rpm and much more boost - this then causes more autothrottling to hold down boost
... two reasons why it's good not to rush to WOT - even in a non-Spitfire
and of course with multi-engines not rushing to WOT ie differential throttling was literally vital

the later introduction of auto ie single-lever control of power and pitch seemed to enforce this (discreetly)
ie in later a/c such as Tempests (and I presume with later Mosquitos)
single-lever giving lower rpm through the take-off roll (compared to old separate command of rpm by pitch control lever)

also the later props mostly were less efficient converters at runway speeds (especially the contra-rotators)
(because typically smaller diameter with the same power or the same diameter with increased power)

notice iirc the fixed pitch Spitfire/Hurricane prop weighed 84 lb and the early 3 blade VP comparison weighed 342 lb
so it seems the plane (for the comparison tests) artificially had 150 lb of ballast when FP (ok 40 lb ballast when VP)
and the 'last gasp' Italian Schneider Trophy 24 cylinder - it's contra-prop gave the design smaller so shorter floats
but their shorter length was slower to unstick - takeoff runs were 2 miles
maybe the earlier designers knew what they were doing


that Mr Shenstone seemed to know what he was doing .....

in effect NACA invited design of airfoils via a unified system of 'formulae' derived from outstanding airfoils worldwide
NACA 22s didn't exist as proven designs unless/until someone outside NACA made and tested them (at realistic Re nos)
ie NACA made and tested and reported on the 00 and 23 and 46 families and many others - but never 22s
eg NACA Report 460 1933 and NACA technical Note 487
460 shows that 2312 (12% thick) is probably the best 23 aerodynamically (ignoring structural properties of course)
487 shows that the 'old' Clark Y was better in lift coefficient than the 22s

Shenstone was talking to Bellanca - and the Spitfire acquired fillets like the (long-distance racer) Bellanca 28-70
that used a (Bellanca) 'type M high lift' airfoil c.12% thick - its performance was clearly outstanding (record breaking)
the 28 having a rather forward mainspar and external bracing - the 'M' was quite similar to the NACA 22 'formula'
Shenstone presumably chose the 2212 (rather than 2312) because of the Spitfire's 'single' spar web being rather far forward
btw/iirc using the modern convention for the point of 'tip thickness' some determine the Spit tip aerofoil as 2208.5
the 2212 seems to have been the best match to the ongoing Spitfire structure established around steam cooling

elliptical wings give less induced drag so mainly help at high altitudes not low (Typhoon/Tempest) altitudes

[J.A.W.]

The Macchi 'twin twelve' seaplane which was indeed fast enough to take
(& hold, to this day) the seaplane speed record was too late to stop
Supermarine taking the Schneider Trophy for Britain in perpetuity,
but of course had each V12 powering a coarse/fixed-pitch wooden prop,
so every take-off was bound to be to be a 'judicious' event, counter
rotating props, or no.

The extra blade added by using the Tempest prop on the Typhoon,
shortened take-off distance (& reduced the fatiguing buzz-vibration),
- something the late-production Corsairs emulated - while that inverted
'gull-wing' was intended to provide both prop-disc clearance & also a
root attachment which did not require the Spitfire's elaborate fillets.

[J.A.W.]

Here in this vid posted below, at 7:30 in, erstwhile member 'snowygrouch' appears to make
some erroneous assumptions about the Napier Sabre engine, & sleeve valves in general.

He needs to check the published ratings of these engines, as the R/R Merlin never matched
the Sabre's contemporary power outputs, & the Sabre doubled its supercharger boost levels
in service between 1942 & 1945, without habitually punching sleeves through its ports.

(How do wet-sleeve engines cope?).

Further, only comparatively few Sabre engines were produced, ~5000, compared to about
30 times as many Merlin mills. R/R wanted to offer its Griffon V12 as a Sabre substitute,
for De Havilland & their 'super-Mosquito' design - & for Hawker, too - but it was inadequate.

[Tommy Cookers]

.... some erroneous assumptions about the Napier Sabre engine, & sleeve valves in general.
.... the Sabre doubled its supercharger boost levels
in service between 1942 & 1945, without habitually punching sleeves through its ports.
(How do wet-sleeve engines cope?).

wet liners have stiffening ribs
boost increase isn't absolute pressure increase - the Sabre's peak cylinder pressure didn't change hugely
the Calum Douglas book is useful - I gave it an upvote


the Sabre (as other sleeve-valvers) was a response in the 1930s to the problem of the 1920s ......
detonation (forcing low supercharging or low CR) due to low fuel quality and high valve temperature

these problems had (for the Allies) disappeared by WW2
improved internally 'sodium'-cooled valves and 100/130 fuel allowing far more power via increased supercharging
100/130 being of high aromatics content - their detonation resistance rose via low flame temps via very rich mixture
the '1000 hp' class V12s became 1500-1600 hp almost overnight - and retained good cruise economy (range)
NACA's Pinkel said the supercharger was far more important than the engine ....
and (due to exhaust jet effect) better than the turbocharger except at high altitude

how would they have used anything else ? (to real advantage)
the low-altitude role flattered the Tempest (playing to its high engine weight and high wing loading)

[J.A.W.]

In fact, the unencumbered combustion chamber, with ideally placed sparkplugs
allowed the sleeve valve engines to operate on a higher compression ratio for
any given grade of avgas, & thus burned it more efficiently, in cruise settings.

The Napier Sabre reached its highest in-service boost levels on 100/130 avgas,
whereas the poppet valve R/R V12s required 150 grade fuel to safely run at
highest pressures, & were limited to more modest supercharging by 100/130.

Further, the excessive TEL dosing of 150 grade avgas caused 'leading' issues
for the poorly located sparkplugs of OHC V12s & damage to poppet valve seats,
while sleeve valve engines were not so affected by such 'lead poisoning'.

As for your comments on the the Tempest, of course for the RAF - both the low-level
defensive ops against Nazi V1 cruise-missile attack, then post-invasion tactical ops
on the continent - were naturally going to require their best performing fighter at the
altitudes where combat was happening (whereby 'trade could be done', in RAF speak).

[J.A.W.]

The medium/low altitude suited the "...More warlike qualities" of the Tempest, as Spitfire ace
& Tempest Wingco-flying E.D. Mackie put it, (& esp' in comparison to the USAAF 9th TAF usage
of their portly high-altitude optimised/turbo-charged P-47 Thunderblot in the same role).

The official figures also contradict your assertion re: cylinder pressures T-C,
(as cited by Wilkinson & viewable online in WWII Aircraft Performance
& linked in this post, below these examples):

See for example, as a comparison of contemporary engine marks shows:

Merlin 45 & Sabre IIa respectively;

BMEP (max): 243lb/sq.in & 210lb/sq.in.

Hp/litre: 56hp/L & 60hp/L

Weight/hp: 0.41kg/hp & 0.48kg/hp

Cruise fuel consumption: 235g/hp/hr & 210g/hp/hr


Merlin 66 & Sabre Va;

BMEP (max): 274lb/sq.in & 239lb/sq.in.

Hp/litre: 63hp/L & 70hp/L

Weight/hp: 0.44kg/hp & 0.44kg/hp

Cruise fuel consumption: 240g/hp/hr & 225g/hp/hr


Merlin 130 & Sabre VII;

BMEP (max) : 293lb/sq.in. & 321lb/sq.in.

Hp/litre: 67hp/L & 95hp/L

Weight/hp: 0.43kg/hp & 0.33kg/hp

Cruise fuel consumption: 225g/hp/hr & 205g//hp/hr



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

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

[Tommy Cookers]

In fact, the unencumbered combustion chamber, with ideally placed sparkplugs
allowed the sleeve valve engines to operate on a higher compression ratio for
any given grade of avgas, & thus burned it more efficiently, in cruise settings.

The Napier Sabre reached its highest in-service boost levels on 100/130 avgas,
whereas the poppet valve R/R V12s required 150 grade fuel to safely run at
highest pressures, & were limited to more modest supercharging by 100/130.
Further, the excessive TEL dosing of 150 grade avgas caused 'leading' issues
for the poorly located sparkplugs of OHC V12s & damage to poppet valve seats,
while sleeve valve engines were not so affected by such 'lead poisoning'.

As for your comments on the the Tempest, of course for the RAF - both the low-level
defensive ops against Nazi V1 cruise-missile attack, then post-invasion tactical ops
on the continent - were naturally going to require their best performing fighter at the
altitudes where combat was happening (whereby 'trade could be done', in RAF speak).

the Mustang III flew at 17 gph (AP 2025G Pilot's Notes)
being a smaller engine - at low powers the Merlin consumed much less fuel than the Sabre (at those powers)
no matter if at its best-efficiency power some Sabre is better than some Merlin (at it's best-efficiency power)
and Wilkinson shows that the Merlin (61/V-1650-3) and earlier give 0.45 lb/hp/hr
ok later 60s 0.5 lb - seemingly the effect of the (for GB ?) mod 987 camshaft change that increased overlap to 70 deg
it's often said that the Mustang (and eg bombers) prioritised range in their engine choice ie continued with 1650-3s)

ok sleeve-valvers had higher CR (so they should with their lower boost) and were slightly better 'on the bench'
though the hp figures ignore exhaust thrust - this would be proportionately higher with Merlins due to their 'low' CR
exhaust thrust perhaps paid most dividend in aiding climb before dive

but the Sabre VII was a fiction ie it was never cleared at 20 lb boost for flight or for sale (as I wrote 3 years ago)
eg what plane would have used 20 lb boost 3500 hp at takeoff ? - and with what propeller ?
20 lb boost was not available from Napier or Bristol - but it was used every day by Merlins
(remember RM17SM spec Merlins were cleared with ADI at 30 lb boost - ok none were sold but they were cleared)
and Sabre VII weight given was 2500-2540 lb - remember even the Centaurus knocked 350 lb off the Tempest's weight


and .....
150 grade had no more lead than 100/130
British 150 was 100/150 (the 100 'proved' there was no more lead) - the 150 came from the 2.5% monomethyl aniline)
115/145 of course is the one with the high lead content
mod 987 engines required a particular type of spark plugs
remember GB supplied millions of plugs to the USA - on those eastbound ships

a Spitfire or Mustang designed for a low level role would have had much less wing etc etc than otherwise as they did
(remember the Spit 3 and so some Spit 12 conversions eg DP845 had less wing than any later clipped wings)
then consider the Republic AP-4 & AP-10 which was the initial XP-47 (100-130 sq ft wing area with an Allison 1710)
of course the usual argument against this is that armament must be lighter

[J.A.W.]

being a smaller engine - at low powers the Merlin consumed much less fuel than the Sabre (at those powers)
no matter if at its best-efficiency power some Sabre is better than some Merlin (at it's best-efficiency power)
and Wilkinson shows that the Merlin (61/V-1650-3) and earlier give 0.45 lb/hp/hr
ok later 60s 0.5 lb - seemingly the effect of the (for GB ?) Mod 987 camshaft change that increased overlap to 70 deg
it's often said that the Mustang (and eg bombers) prioritised range over power (so kept on using 1650-3s)

ok sleeve-valvers had higher CR (so they should with their lower boost) and were slightly more efficient 'on the bench'
but the Sabre VII was a fiction ie it was never cleared at 20 lb boost for flight or for sale (as I wrote 3 years ago)
eg what plane would have used 20 lb boost 3500 hp at takeoff ? - and with what propeller ?
20 lb boost was not available from Napier or Bristol - but it was used every day by Merlins
(remember RM17SM spec Merlins were iirc cleared with ADI at 25 lb - ok none were sold but they were cleared)
and the Sabre VII weighed 2500-2540 lb - remember even the Centaurus knocked 350 lb of the Tempest's weight
and the (then) official hp figures ignored exhaust thrust - proportionately higher with Merlins due to their 'low' CR
exhaust thrust was also quite useful in the climb


and .....
150 grade had no more lead than 100/130
(150 was often 100/150 - proving there was no more lead)
(the 150 came from the 2.5% monomethyl aniline)
115/145 of course is the one with the high lead content
Mod 987 engines required a particular type of spark plugs
remember GB supplied millions of plugs to the USA - on those eastbound ships

a Spitfire or Mustang designed around the low level role would have had much less wing etc etc than they did
(remember the Spit 3 and so some 12 conversions eg DP845 had less wing than any later clipped wings)
then consider the Republic AP-4 & AP-10 which was initially the XP-47 (100-130 sq ft wing area with an Allison 1710)
of course the usual argument against this is that armament must be less

Wilkinson's published figures of officially "cleared" ratings are surely not "fiction" T-C,
regardless of your claims otherwise, & the BMEP gains shown clearly demonstrate the
ability of the Napier/Bristol sleeve valve to accept high pressures sans punching parts
through ports, as was purported.

As I noted earlier, the R/R V12's required 150 grade fuel to operate on higher boost levels,
& accordingly de-rated postwar, to cope with ordinary 100/130 avgas, (ADI Griffons excepted)
R/R themselves published a pamphlet on the issues that they had to overcome with
the use of highly TEL 'doped' avgas: http://www.wwiiaircraftperformance.org/ ... lovesy.pdf

I'd suggest you re-check your claims about weight, since the Centaurus was a rather big engine,
& for equivalent boost levels did not match the Sabre in performance either as power-to-weight,
or in flight, while powering the Hawker Tempest/Fury, as shown in the 'Flight' article below:

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

[Tommy Cookers]

for a plane that's half the weight of the Tempest and half the wing area and half the power .....
try a new-built Yakovlev 3 with an Allison 1710
(or a new or rebuilt 11 with a Twin Wasp R-2000 like the holder of a c.410 mph record)
https://vintageaviationecho.com/yakovlev-yak-3/

so the serving Merlin 130 was 'derated' for 100/130 fuel - to 2030 hp @ 18lb boost no ADI (and engine weight 1640 lb)
the serving Sabre 7 without ADI gave 28% more power (or 50% more with ADI) than the 130 - but had 55% more weight
and what was the weight of its ADI tank and the contents ?
if the 130 had used a single-stage supercharger (like the Sabre) it would have weighed 1450 lb
ie the Sabre would have been 75% heavier
this makes the DH Hornet configuration look attractive
and the ideas that minimise crankshaft and crankcase weight eg radial and 'X' arrangements

a single-stage Merlin (designed for low altitude) could make 1850 hp on 100/130 @ 20 lb no ADI (and weigh 1385 lb)
(according to RR's Lovesey paper that showed the best superchargers at low PRs were the later single-stagers)
(earlier naval 32s had given 1645 hp @ 2000' in 1942)
and 2050 hp on 100/130 @ 25 lb with ADI (or on 100/150 fuel 2400 hp without ADI and 2640 hp with ADI)

so on 100/130 the Merlin flew extensively at 18 lb without ADI .....
but no Sabre at more than 15 lb without ADI - or 17.25 lb with ADI

RRs paper seems to have the same status as one reference book's Sabre 7 claim of 3500 hp @ 20 lb with ADI
there seems to be no record or claim that such a 'Development Type Test' was passed
there seems to be no evidence of customer interest eg 1946 Airspeed or Folland ?
the chairman of Napier Power Heritage has rubbished Setright's (other) distant and wild claims
RR had customers flying 'Type Tested' and flight-cleared engines at 30 lb 36 lb and 120" Hg eg P-82 and XP-51F & G

http://www.npht.org/sabre-3
the Sabre was originally a sleeve-valve diesel - perhaps scope there for sleeves punched into ports ?

.... and btw there's a helluva lot of book people who think of takeoff power rating as the highest

[J.A.W.]

Going off on a bit of a ramble there again T-C?

"Some book", Wilkinson's contemporary tome* using official ratings figures,
or an R/R in-house produced period 'puff piece', which is most likely to be
reliable as an impartial data source.

For all his flamboyant flourishes in writing, Len Setright stated he'd had direct
access to Sabre test data via the original Napier factory files, something that
Napier Heritage does not, (though IMECH has some in their archive, as does Kew).

Whether BAE holds the Hawker-Langley test flight reports in its archives is also
of topical interest, as the 2nd Sabre-Fury prototype VP 207 was still being flown
there in 1948, as noted in 'Flight', (& in Hawker test pilot Neville Duke's memoir),
so it would've been the most likely recipient of any 3,500hp Sabre VII to fly, perhaps
excepting Napier's experimental Tempest VI, based at their Luton flight establishment.

Of course it is a mark of how robust an engine is, if it can tolerate WOT usage at S.L.,
& a contrast between Sabre & Vulture in as much as the Vulture appeared to behave
itself when flown in a fighter (Tornado), but disgraced itself under duress in hauling
a large twin-engine bomber (Manchester), whereas the Sabre threatened the airframe
of the similarly large twin-engine bomber (Warwick) it was test-flown in, due to power!

De Havilland would've liked to build a 'super-Mosquito' utilizing Sabre-power, but none
were forthcoming, (& the R/R Griffon was no substitute) so the Hornet was a fall-back
option, interestingly however, in postwar 'mock combat' the RN FAA pilots found the
Sea Fury had the measure of the Sea Hornet, but not the RAF's Sabre-Tempest F6's
encountered off East Africa, due to the power & wing area advantage of the Tempest.



*Noted by Lumsden, in his book, likewise.

[J.A.W.]

...so the serving Merlin 130 was 'derated' for 100/130 fuel - to 2030 hp @ 18lb boost no ADI
(and engine weight 1640 lb)...


a single-stage Merlin (designed for low altitude) could make 1850 hp on 100/130 @ 20 lb no ADI
(and weigh 1385 lb)...

Ah no, T-C, these figures are not supported by the official ratings published in Wilkinson,
& linked above, which show the Merlin 24 (single stage low-level) was making no more than
1640hp military on +18lb & 100/130, with 150 grade needed to make +25lb boost & 1780hp.


While the strengthened & improved Merlin 130 was capable of making 2020hp, but only
@ +25lb boost - which required 150 grade fuel, the best it could do on 100/130 avgas at
'military' power was 1830hp - whereas the Sabre Va at 'normal' power was giving 2165hp,
at similar heights, a figure the Packard Merlin V-1650/9 needed 115/145 (& ADI) @ 90" Hg
MAP (~ +30lb boost) to beat, & by about 55hp...

[Tommy Cookers]

http://www.wwiiaircraftperformance.org/ ... ornet.html
proves that ....
look at Supplemental (list of items) ....
(item Merlin 130...Operating Warning Card)
the Hornet was on 100/130 initially limited to 18 lb boost - but this was raised to 20 lb
(item Hornet Pilot's Notes - Operating Data)
the Sea Hornet was (being always on 100/130) limited to 20 lb ..... and .....
(item Sea Hornet MkXX&XXI Leading Particulars)
so gave 1960 hp at 4000' ..... and of course other powers at other altitudes
ie 2030 hp widely stated eg by (former head of experimental flying) ace pilot Brown isn't inconsistent with the above

(btw the performance chart suggests that Max Combat power gave 50 mph more speed than Rated power)

an engine rating is a boost rating - not a power rating ....
for a given boost..... supercharger power consumption will vary with altitude and with (auto) throttling
so crankshaft power (within a given rating) will be different for every different altitude
(so many apparently different rated 'powers' - this usually concealed on charts as being a pointless complication)