Last & Best of the Piston Engine Fighter Aircraft.

[Smokes]

anyone know anything about the asymmetrical wing of the Macchi C.202. ie how well it worked in countering the prop torque.

[Tommy Cookers]

the limit of turn performance should be problematic and recovery from the consequent spin should be difficult/impossible
it was
in a spin one the dominant wing (the one that's more deeply stalled than the other) holds the plane in the spin
span-asymmetry increases the dominance of the dominant wing
ok a highly asymmetric WW2 German plane (Blohm & Voss 141 ?) was good (but how was the spin ?)
the genesis of S-A seems to be 2 government workers who were the S and V of the WW1 Ansaldo SVA
intended to be efficient wrt range and speed
their designer was C.Rosatelli - the CR of Fiat CR32 CR 42 ? etc (someone on the 'net says the G50 was span-asymmetrical)

'countering prop torque' sounds important but what does it mean ?
PT (because the prop slipstream is helical) has more related yaw effect than related roll effect
and the helicity of the slipstream (in a single-engine plane) causes a rolling effect from the tail that opposes the PT roll
and the ailerons are ground-settable to counter average PT roll and/or trimmable in-flight to counter any PT roll
a Spitfire has no aileron trim
a Mustang has aileron trim but it is not used eg for takeoff
a Skyraider has aileron trim and it is used eg for takeoff
all these of course had and used eg for takeoff rudder trim
(famously the 109 has no rudder trim - alleviated 109F-onwards by the fin aerofoil effect)
a flying club might have 5 planes that don't quite fly laterally level and straight 'hands-off' - and 1 ground-set so that it does
lateral trim of 2 equal-span wings however performed amounts to effective local differences in airfoil

very broadly the PT is constant regardless of airspeed and it is continuously countered in flight without pilot thought
but at low airspeeds the flight controls have far less authority and control will be difficult
Richard Grace has just told us on TV that the 109 should be kept on the ground till reaching a goodly speed
ie that uneven ground can have it tipping onto 1 mainwheel
he works on these (Hispano Buchons) and other WW2 stuff at Sywell
https://vintageaviationecho.com > p-47-thunderbolt-nellie and others are worth a read
any time a fast plane is flying slowly then goes to high power the pilot is giving himself a big job
with fixed pitch props the PT will be excessive relative to the thrust developed
(fwiw I suspect some wartime versions of CS-prop planes would also over-pitch - to contain the engine rpm regardless
fwiw I suspect there's a name for this aspect of performance - some TNs etc in the Cranfield or NASA archive)

this big job might be less than C205 pilots pulling 6 'g' and getting 12 tons of lift on the right wing but 13 tons on the left

[J.A.W.]

^ Yeah, T-C, I do not know about the Macchi 202, (which re-engined from a radial to a V12),
but Macchi did have experience with powerful racing seaplanes, the fastest of which did
utilize contra-rotating props (fixed pitch units at that, too).

Late production Spitfires could not use full-power for take-off, due to torque issues,
& they too, eventually had a contra-prop arrangement offered...

The Bf 109 did have a vertical tail-fin aero-foil shape oriented to off-set the prop-vortex,
but managed to fly satisfactorily later in Spanish service with R-R Merlin power, one which
turned the 'wrong way', sans alteration to either the fin, or by prop-rotation palliatives.

[Tommy Cookers]

....Late production Spitfires could not use full-power for take-off, due to torque issues....

untrue
you and other 'net miners' are inventing a myth ...
a distortion that started to emerge after on my posting here years ago that ....
Mk XIV Spitfires were (at some time and place) required to use only 3 bar boost on takeoff (to avoid tyre overload failures) ...
this I was told by one such pilot after he had retired decades later as commander of a transport training squadron
'late' production Spitfires of course all had much wider-spaced undercarriage legs and no tyre overloading

fwiw my guess would be that there's nothing in the official-issue pilot's notes

[J.A.W.]

^ No, not "untrue" T-C, since (verbatim) according to Pilot's Notes for the Spitfire Mk XIV:

"49. Take-off.
(i) Whenever possible open the throttle slowly up to +7lb/sq.in. boost only. This is important as
there is a strong tendency to swing to the right & to crab in the initial stages of the take-off run.
If much power is used, tyre wear is severe."

However, the contra-prop equipped Seafire 47 eliminated that problem as noted in a Trial Report:

"Take-off in the 47 is easier than in the previous marks of Seafire since there is no tendency to swing."

[Tommy Cookers]

J.A.W.'s post above is a perverse inversion of the points of my previous post - IMO of course

the many Spitfire XIVs produced were the low point of Spit takeoff handling qualities - (there was a war on !!)
as we seem to agree, the consequence was orders or recommendations to restrict power ie boost during takeoff
there was anyway a general recommendation to increase power slowly during the roll (and withhold maximum where possible)
eg as in (my) pilot's notes PNs for Merlin Spitfires IX, XI & XVI and Mustang III

this is essentially not a torque issue (as Macchi's asymmetrical-span idea) - it's a yaw issue
a tailwheel aircraft is mechanically unstable on the ground (like a wheelbarrow)
the mechanical instability can be stronger than its aerodynamic stability and aerodynamic control authority combined
tail-down the pilot might have mechanical control and if desperate can add mechanical steering by differential braking
(little scope for that in a Spitfire or 109 - and the reason why undercarriage track was increased in later designs)
aerodynamic stability only exists by developing a yaw angle - so yes the takeoff can/will be crabbing ie scuffing the tyres
of course 2 and 4 engined tailwheel planes were steered in the early part of the takeoff by differential throttling

I assumed he agreed with me that 'later Spitfires' were the 21, 22, and 24 etc
these had no such observations (in the AEEE and AFDU reports) - yes it would be interesting to see any PNs for these
eg AFDU did takeoffs of the 21 LA201 at 18" boost and more (only asking that the throttle was opened slowly)
these later Spits had 8" wider undercarriage track (and longer legs to allowing their 7" bigger props)
and the 22 and 24 had a much bigger tailplane, fin & rudder

significantly btw ....
the prototypes of both the XIV and 21 used large fins conspicuously having straight leading edges (and large rudders ?)
but the production aircraft had smaller fins/rudders (looking like existing production types eg XIV had VIII units ?)
21s were in production but the AFDU withheld its endorsement of this aircraft (for stability/trim issues in yaw and pitch)
21 orders were migrated to the 22 then 24 as its fundamentally bigger tailplane, fin & rudder solved all the problems

some sfuff was changed during the XIV production run - then 18 and PR19 were similar in layout (pilot's notes anybody ?)
the 18 seemed to have a slightly bigger 'dorsalised' fin (with the fuselage cut down to suit the bubble canopy as many XIVs)
one early XIV recommendation was to move the fine pitch limit stop to a finer position to raise the rpm relative to boost
there being a default throttle/pitch interconnection (unknown earlier in the war ?)
yes this would help a 'torque problem' (as 'predicted' in my earlier post) due to the relatively small prop

contra-rotating props were very heavy - and only used on carrier planes
they solved a problem that didn't need solving
they reduce stability (ok reducing some of the demands on stability)
the SkyRaider managed better without them

[J.A.W.]

^ "...perverse inversion" T-C?

Your ex post facto revisions?

By "later Spitfires", I meant the longnosed Griffon-powered jobs, of course.
Most production Spitfires were wartime 'lash-ups' or "interim" as they were termed,
being 'hotrod' variants of earlier types, albeit receiving needful adaptations as shown below:

http://www.spitfireperformance.com/rb141handling.html

The Spitfire XIV did have increased fin area over its (already modified) Mk VIII parent,
& it was somewhat overpowered, but it was the later yet, & significantly modified Mk 21
Spitfire which was panned for its poor handling characteristics, which were then remediated
by Mk's 22/24 via inclusion of the still larger-yet tail empennage from the new Spiteful
(which had finally adopted the Hawker-style inward folding wide-stance landing cart,
but which also had its own handling issues, due to the dreaded 'laminar-flow' small-area wing).

[Tommy Cookers]

the 21 with improved rudder trim and elevator balance was deemed 'suitable' by AFDU in Mar 1945
120 such then entered service eg in Europe before VE day

ie apparently no Spitfire type introduced at or after this date was required to limit its takeoff power
this of course without contra-props
such machines served till 1955
yes, as I said, it might be interesting to look at the 19's and 18's PNs etc
and remember Merlins didn't exceed 6 lb boost at full power till the introduction of '100 octane' fuel in summer 1940

btw
Spitfire IX - XVI PNs ....
give severe restrictions when rear fuselage tanks are in use
suggest 7 - 9 lb boost for takeoff 'at normal loads'
give 30 gph in weak mixture at -(minus that is) 4lb boost/1800 rpm
Mustang III (RAF) PNs ...
similar restrictions/recommendations etc
give 17 gph weak at 20"/1800 rpm (called 'boost' really MAP) low altitude - and 25 gph high altitude
Mustang USAF flight handbook says ...
high blower can be manually selected at altitude below set 'auto' altitude (ie not just ground checks of high blower function)

[J.A.W.]

A fair few Pilot's Notes are available for perusal/download at https://www.avialogs.com/

A check of the Spitfire Mk 22/24 Pilot's Notes shows the remarks per take-off to be in fact
identical to the Spitfire Mk XIV paragraph quoted in my post on this subject above, (2nd Dec).

As a contrast, Hawker Tempest T-O, (on test by a 'Flight' staff pilot, linked back on page one):

"I had been told that +9lb boost @ 3,750 rpm was adequate, but +15lb @ 3,850 was available,
if I preferred it."

(A higher T-O power level than any Spitfire had "available", & via a 14 foot diameter prop!)

So it seems that unless contra-prop equipped, Griffon-engined longnose Spitfire take-off
power-level was indeed limited by the undercart, to judicious boost, & due circumspection...

[Tommy Cookers]

A check of the Spitfire Mk 22/24 Pilot's Notes shows the remarks per take-off to be in fact
identical to the Spitfire Mk XIV paragraph quoted in my post on this subject above, (2nd Dec).

As a contrast, Hawker Tempest T-O, (on test by a 'Flight' staff pilot, linked back on page one):
"I had been told that +9lb boost @ 3,750 rpm was adequate, but +15lb @ 3,850 was available,
if I preferred it."
(A higher T-O power level than any Spitfire had "available", & via a 14 foot diameter prop!)
So it seems that unless contra-prop equipped, Griffon-engined longnose Spitfire take-off
power-level was indeed limited by the undercart, to judicious boost, & due circumspection...

you have conveniently misrepresented the Spitfire XIX/XIX PNs on takeoff (as limiting to 7 lb boost)
by omitting the second sentence of the paragraph (it destroys your argument)
it says '12 lb boost may be used at heavy load'
(12 lb is the rated ie non-combat maximum power)

so there's no evidence that any Spitfire was for takeoff unable to use rated maximum power


the narrow track undercarriage (vs the wide track undercarriage) ......
yes narrow would have more of its travel 'eaten' by prop torque (roll effect) - springs/tyres could bottom on bumpy airstrips
(we might call this the 109 effect - read John Romain in the link I posted)
in some ways wide is bad (eg some pilots said that the Spit was better at keeping straight) ...
and eg wide ..
inhibits single-wheel touchdowns (for crosswinds)
doesn't really reduce the factors starting swing aka 'groundloop'
eg lots of Mosquitos were wrecked that way
eg TO 1F-51D-1 says for the Mustang 'do not jam throttle forward, as torque will cause loss of control of the airplane'
eg PN Mustang III 'open throttle slowly to the takeoff position if 61" is required - 46" is sufficient for a normal takeoff'
doesn't do much to prevent the plane going over its nose
doesn't do much to help taxying crosswind any distance
yes it was handy for pilot confidence (that the plane was more likely to remain 'bubble up' in a takeoff/landing accident)

like all high power/weight tailwheel aircraft a Tempest, Sea Fury etc was in takeoff and landing an accident waiting to happen

[J.A.W.]

No T-C, "...an accident waiting to happen" is going too far.

Spitfires evolved from 1930's 'light on their feet' fighters designed to operate from RAF
shortish grass strips, (& were described by Bf 109 pilots on test as "childishly easy" to handle),
into longnosed over-powered 'hot-rods', with double the power (& commensurate weight-gain).

Of course more boost could be used on a heavily-loaded (9,200lb Mk's 22/24) take-off, laden
with bombs/auxilliary fuel tanks,(& with alterations in CoG), but Griffon engines themselves
were rated at up to +25lb boost, inc' +21lb for take-off (depending on fuel grade*) even if
Spitfires could not utilize it: http//www.spitfireperformance.com/griffon-69.pdf

Per the problematic directional stability take-off issues exhibited by the Mosquito, some were
certainly addressed in the later, more advanced Hornet, 1stly by using 'handed' rotation engines,
& also by the needful addition of significant extra fin/keel area..

*Those powering the Shackleton were contraprops provided with an ADI/'wet' take-off boost option.

[Tommy Cookers]

....but Griffon engines themselves were rated at up to +25lb boost, inc' +21lb for take-off (depending on fuel grade*) even if Spitfires could not utilize it: http//www.spitfireperformance.com/griffon-69.pdf

Per the problematic directional stability take-off issues exhibited by the Mosquito, some were
certainly addressed in the later, more advanced Hornet, 1stly by using 'handed' rotation engines,
& also by the needful addition of significant extra fin/keel area..

all Griffon-engine Spitfires having 21lb boost takeoff engines could use 21lb for takeoff
and/but no such fighter planes eg Hawker, DH, or VS used military aka combat power for take-off
(afaik only eg Merlin 70/266 in the 'invasion special' Spitfire XVIs did)
and Griffons never had a rating at 25lb at sea level (except perhaps on the much later ADI Shackletons)

and the comment re the Mosquito and Hornet is nonsense
contra-rotation props eg handed make essentially no difference when an engine stops
there is a 'death zone' from take-off until speed reaches Vmca
eg with a Hornet at max weight below 155 knots the outcome (of an engine loss) was typically fatal (similarly so the Mosquito)
ie an engine failing as fuel exhaustion commences after a protracted war flight/landing attempts in adverse weather

the (Sea) Hornet was to have 'inner blade upwards' prop rotations - good for wing drag but control and stability were nbg
it had to be given 'inner downwards' prop rotations and a fin extension to be any use

regardless of prop 'same-rotation' or contra-rotation a tailwheel aircraft will try to leave the runway in any direction
'same-rotation' just gives a greater effect in one direction (and less in the other direction)
eliminating any cross-wind helps (but you need an aircraft carrier for this)
that's why they went to tricycle wheel designs

there was always a conflict between stability/controllability and flight performance
often apparent when increased performance was required, whether after design or before
eg the Sea Fury needed redesign giving a bigger and fancier rudder before it was acceptable (just like those Spitfires)
though the SF as designed had a longer tail than the Tempest - as the P-82 and P-51H had longer tails than the eg P-51D


regarding Smokes post and implied 'torque problems' .....
PNs (mid-WW2) show automatic coordination of 'throttle lever'/boost/rpm - this seems potentially disadvantageous
at takeoff (to minimise torque) prop rpm should and would be maximised ie manual over-ride used (as predating auto)
'throttle' lever and autothrottle together demand boost/torque and the prop torque-matches the engine by adjusting aerodynamic pitch
presumably (if slamming throttle up in low speed flight) overpitching is the designer-chosen lesser evil (rather than over-revving)

automatic coordination presumably eased difficulties in engine control elsewhere
supercharger delivery is very rpm-driven so the auto lowering of rpm with 'throttle' reduction could be useful
eg to prevent pilots frightened of plug fouling from high lead fuel keeping rpm rather high in cruise
interestingly Mustangs & Merlin Spitfire PNs explain forcing medium blower in high altitude cruise (for better economy)
as well as not explaining forcing high blower at lower altitudes (which some have admitted doing)

[J.A.W.]

"Nonsense" T-C?

Well indeed, your claim that Griffon Spitfires were cleared to use +21lb boost
for take-off is specifically contradicted by the Pilot's Notes, & with due rationale.

The 'Flight' pilot testing the Tempest was advised that max-boost of +15lbs @ 3,850rpm
was "available" for take off, if he "preferred" it, as I'd noted, earlier.

As for R-R going to the trouble of developing 'handed' rotation Merlin engines,
it seems highly unlikely that Lord Hives would approve such a development,
if it amounted to "nonsense", either.

Capt Brown was the Admiralty's test pilot for the Sea Hornet FAA trials, & he
made further recommendations for improvement to low-speed control functions
over the standards acceptable for RAF flying, & he'd already noted the advance
the Hornet offered over the Mosquito in this vital area of flight performance.

[Tommy Cookers]

no Griffon engined Spitfire built for a 21lb boost takeoff rating engine was unable to use that 21lb boost at takeoff

AFDU wrote in late 1944 (though temporarily rejecting the Mk 21) that ...
(a) there was no problem with takeoff - this was better than the XIVs
(the rejection was due to poor flying characteristics wrt gunnery)
(b) exceeding 18 lb was unnecessary for takeoff unless from a very short runway, full boost then being allowed

so as I posted 2 weeks ago ...
VS didn't make Griffon Spitfires after the XIV limited to a takeoff power less than the engines takeoff rating

regarding the 'nonsense' of counter-rotation on the Sea Hornet ....
it was no relief to the engine-out danger of the Mosquito (and other twins whose power and weight so increased in WW2)
95% crashing if an engine stopped early in the climb
(having only enough rudder authority for a lighter, less powerful and more stable plane)
btw on this site there was a post by Autogyro re what Eric Brown said about this SH aspect at a lecture


regarding asymmetry and 'torque' ....
the first thousands of Spitfires had only 1 wing radiator
apparently intended somewhat to act against said 'torque'

[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.

Also, for Griffon Spitfires, even maximum weight take-offs at available higher power settings
were restricted to hard surface airstrips, presumably due to the torque effect causing divots.

In fact, the 'mislanding' section of the P.N. specifically warns about torque effects due to abrupt
application of high power throttle-settings, on aborted landing attempts, then subsequent fly-offs.

& AFAIR, it was the increased cooling demands of power increases (inc' 2-stage charge-cooling)
which dictated the larger volume of the underwing coolant scoops on successive Spitfire marks.