'Increasing the Charge' - how piston engine technology provided the power to fly

[J.A.W.]

Schematic comparison of R-2800 fighter supercharger ducting installations, P-47 & F-4U.

http://www.enginehistory.org/Installations/P-47.jpg

http://www.enginehistory.org/Installations/F4U.gif


& turbo control..

http://www.enginehistory.org/Installations/TypeBControl.jpg

 

[mz]

Some of the solutions seem so odd.

Why was the P-47 intake all the way in the front? It takes a huge amount of space. Why not put it further to the rear top like in a P-39 or sides like P-38 oil coolers or bottom like the P-51 oil cooler? (Latter might cause debris problems?)

 

[tartle]

P-47 air cooled; P-51 liquid cooled may have some part to play in the aircraft powerplant designers' choices.

 

[Granit]

Why not put it further to the rear top like in a P-39 or sides like P-38 oil coolers or bottom like the P-51 oil cooler?

Republic did so, making the P-72.

 

[J.A.W.]

Ah, yeah, the huge P&W R-4360 'corncob' 28 cylinder 4 row radial..

It was tried as a fighter mill & flown in both Thunderbolt & Corsair airframes,
but it failed to offer any worthwhile performance improvement over the proven R-2800 installations.

No production Thunderbolts & ~10 Corsairs were built to examine the monstrosity.
The XP-72 shown - deleted the turbo, & flew as a single stage mechanical supercharged unit..

The R-2800 equipped P-47 utilized the ram air effect via the scoop integral to its engine cowl..

Tartle is correct to note that liquid cooled engines could operate inter/after coolers using their liquid coolant,
this of course, is a more compact/efficient method than the air/air type utilized by the R-2800..

 

[J.A.W.]

Here is an example of a much modified Mustang racer, with intakes moved to the wing leading edge..

http://www.warbirdsnews.com/warbird-restorations/anson-johnson-p-51-racer-restored-neam.html

 

[J.A.W.]

This article from 'Flight' shows the Hawker Fury as fitted with Centaurus radial & Sabre inline mills..

http://www.wwiiaircraftperformance.org/Fury/Sea_Fury_Flight.pdf



& the Hawker Fury matched with Griffon inline/offset annular radiator.

http://1000aircraftphotos.com/Contributions/PippinBill/5597L-2.jpg

 

[J.A.W.]

This 'Flight' article shows the comparatively compact arrangement of the R-R Griffon intercooler.

http://www.flightglobal.com/pdfarchive/view/1945/1945%20-%201853.html

 

[tartle]

Most Typhoon websites contain the same sentence:
"Another Typhoon modification, the P.1010, was to have had leading-edge radiators and a turbo blower, but work on this was not proceeded with."
At Kew this morning whilst waiting for some documents to arrive from the vaults I found a reference to a 'turbo supercharged Typhoon Proposal"
I ordered it up (from the vaults) and to my surprise amongst all the reports and documents was a couple of folded blueprints.
The best copies I could get are attached below:
The first three show the engine layout and blower position in wing roots behind wingroot intakes'
The GA is in the next three.
Some performance estimates will follow

 

[JFC Fuller]

Oh tartle, you really do know how to spoil us. I do love that moment at Kew when you realise the folder you have collected contains one of those envelopes that can only contain some sort of large chart or plan.

Those drawings do raise a number of questions though, most notably whose turbo were they thinking of using?

Re Sabre Furys; without doubt the best looking UK piston engined fighters ever built and probably the best performing too. However, the Air Ministry preferred Centaurus birds, even in Tempest form, so tried to chop 1,500 Sabres from the 1945 programme. The Liverpool factory was intended to be capable of, and seems to have achieved, 2,000 Sabre's a year. I don't have the figures for the original Napier Acton plant.

 

[J.A.W.]

Good archive mining effort - well rewarded there, T.

Paper proposal only? Unless it was a 'sweetener' for the mooted US production?
For Bell/Chrysler perhaps? Chrysler intended their V16 to be turbo'd, & Bell tried to turbo their P-39..

Napier has now been producing turbochargers for longer than they made aero-engines, but I don't know if they
ever actually test ran - or flew - a turbo-Sabre..

JFCF, as the Flight Fury article makes plain, the RAF was jet bent, & did not want any new piston fighters.

The Centaurus Fury was 'marinated' for the RN/FAA ( oddly- since the Griffon was the FAA mill).

& the ratio of Sabre Tempests to Centaurus Tempests built ended up being ~2-1.

Sabre Tempests were being run hard ( the way they ran best) right up to the mid `50s - as target-tugs,
- likely as a way of using up all those Sabres held in store.

 

[J.A.W.]

It seems the Sabre Fury prototypes were the fastest mil-spec piston powered aircraft below ~20k ft.

Given the prodigious output figures published for the Napier Sabre..

'Aircraft Engines of the World'- gives Sabre 7 rated output as "3,500hp/3,850rpm @ +20lb (70.6in)" for take off,
& a "military rating of 3,055hp/3,850rpm... ...normal rating of 2,235hp/3,700rpm... cruising... 1,750/3,250..."
(Figures for low - M/S - alt/levels).

A turbo installation which would maintain that Sabre boost/power output to +30k ft, - would certainly have allowed the Hawker fighters an unequivocal 'fastest' piston-powered accolade..

 

[JFC Fuller]

There were large scale cancellations of piston fighters for the RAF in 1945. The Air Ministry seems to have favoured the Centaurus, even for RAF aircraft, for the Pacific theatre. The reason for the final figures favouring the Sabre Tempest is because it took a long time to set up Centaurus production which pushed out Tempest II production to such a stage that it suffered heavily from the 1945 cancellations. However, it is true that all RAF Furies were to have the Sabre VII.

 

[J.A.W.]

JFCF,

- it is very likely, more a question of engine availability, & production-political-service need issues..

.. since 400 Tempest Mk I (with higher altitude rated Sabre & wing leading edge radiators) were also cancelled.

& like-wise the final (& best performing production type) Tempest - Mk VI - was cut back to a total of 143 built.

Addit: A quick book-check shows a bit of production-political musical chairs-type mucking about too..

Gloster were to build Tempest Mk II ( Centaurus), but were busy with Typhoon-then-Meteor, so Bristol
were assigned the Mk II production, but Hawker then finished with Hurricane production..

.. ( & Hawker workers on strike upset Tempest production in 1944 - when they were required for defence against the V1 cruise-missiles).. , so Hawker then got all Tempest/Fury production back 'in house' at Langley.

 

[JFC Fuller]

The Tempest I was cancelled because Napier abandoned the Sabre IV due to development issues. As far as I am aware this was a case of either or, not of additional engines/aircraft as there was not a planned increase in Sabre output. Those 400 aircraft became Tempest Vs.

For the record, Ministry of Aircraft Production preferred the Sabre- because the two plants associated with it were up and running at full tilt. It was the Air Ministry that wanted the Centaurus.

 

[tartle]

JFCF... the turbo was specified as a General Electric one....
and then this morning we unearthed this installation drawing of the Fairey P.24 plus a good description.. to long to post will absorb and summarise ... eventually.
Then there was that matter of the A.S.H. gas turbine... see the other thread.
...tbc

 

[J.A.W.]

The Tempest I was cancelled because Napier abandoned the Sabre IV due to development issues. As far as I am aware this was a case of either or, not of additional engines/aircraft as there was not a planned increase in Sabre output. Those 400 aircraft became Tempest Vs.

For the record, Ministry of Aircraft Production preferred the Sabre- because the two plants associated with it were up and running at full tilt. It was the Air Ministry that wanted the Centaurus.

JFCF,
Do you know if the Air Ministry wanting the Centaurus - for the Tempest - was related to the fact
that the Tempest design was amenable to accommodation of the Bristol mill, whereas the Typhoon,
(then in full production/operational service/attrition) was limited to Sabre use only?

How many Centaurus mills did Bristol actually get in to WW2 wartime combat service - in any airframe?

Is it known why the FAA, went with the Centaurus, even though the likes of Firefly & Seafire were
using the Griffon, as intended?

Was it due to the Fury prototypes running the Griffon not performing so well?
Or was there a contra-deal with R-R & Griffons going to the Shackleton instead?

The whys & wherefores of the British aero-engine market share/operational use are curiously complex..


Addit: Are the numbers of the 'big three' British piston aero-engines produced definitively known?

AFAIR, numbers built Griffon ~8,500, Sabre ~6,000 & Centaurus ~2,500 (Centaurus figures, from-Wikipedia).

 

[tartle]

I seem to remember from my reading of 'Devons' that part of the problem with wartime planning was the sheer volume of aero engines needed and the obvious inability to switch from one engine to another without considerable disruption. The development delays with say the Sabre represented a nightmare for the planners as it would mean an idle factory... the beauty of the power 'egg' developed by RR and Bristol meant that it was easier to substitute a RR powerplant for a Bristol one and vice versa. Hence the big bomber programme that utilised the opportunity. Must have another look when I finally escape Kew's magnetic attraction.

 

[J.A.W.]

This site includes an interesting photo of a group of female inspectors examining a laid out Sabre on a table..

http://www.aviationshoppe.com/sabre-ii-sleeve-valve-engine-p-256.html

The accompanying blurb appears to be lifted wholesale from Len Setright's work..

 

[JFC Fuller]

Setright's work is great, but in a previous three we tried tracing down the really high HP Sabre test runs and nobody could work where he had gotten the numbers from: http://www.secretprojects.co.uk/forum/index.php/topic,11807.msg114525.html#msg114525

 

[tartle]

Returning to the P-72 intake discussion. The liquid vs air coolant for engine allows for different design solutions:
As water or glycol/water is denser than air in terms of bulk and specific heat it allows minimum loss ducts to be schemed e.g. Mustang and Sptifire. However with air cooled cylinders options are less... the sooner the air gets to the cylinder the better from a ducting point of view. The P-72 minimised the air inlet size round the prop spinner by using a fan. The mechanically driven supercharger was located rearwards of the engine and driven by a long shaft as a search of our site would show. The engine charge air can then go in the belly intake into s'charger then into engine- swapping a short duct for a whippy shaft seems like a swapping one issue for another! You can draw anything on paper as I am finding as I dig deep into archives... but does the system work in practice?

 

[J.A.W.]

AFAIR, Len Setright claimed (when challenged over the Sabre power outputs included in 'The Power to Fly'),
that he had both interviewed the engineers & had seen the documentation that verified them..

Perhaps there is some gold (Sabre dyno-tests) that remains hidden in the vaults at Kew?


The US remote mount, shaft-driven 'auxiliary' superchargers as fitted to the P-63 & XP-72 (proposed, but not flown on the latter) were a bit of a 'lash-up' arrangement for USAAF (nominally turbo users for hi-alt function)
use, but the USN had the most sophisticated mechanical supercharging arrangements for radials.

 

[J.A.W.]

Setright's work is great, but in a previous three we tried tracing down the really high HP Sabre test runs and nobody could work where he had gotten the numbers from: http://www.secretprojects.co.uk/forum/index.php/topic,11807.msg114525.html#msg114525

There appears to be some confusion in this linked statement too, since 3,500hp was listed as the rated
take-off power for the Sabre 7, - in 'Aircraft Engines of the World' - rather than as a destruction test..

The documents would of course, set the matter straight, when/if located/posted..

 

[JFC Fuller]

Every other source I have ever seen for the Sabre VII gives it 3,050hp and not 3,500hp, so I have always disregarded the latter figure as incorrect.

Tartle,

I think your big bomber programme was B.1/39 which was intended to have interchangeable Hercules/Griffon power eggs. Hercules / Griffon matching in paper designs was all the rage for a period in 1939-41. Also, don't forget the Tornado / Tempest approach of using the same basic airframe with different power-plants which of course paid dividends in that case.

 

[J.A.W.]

JFCF,
'Aircraft Engines of the World' lists the Sabre 7 output ratings on +17.25lbs & +20lbs boost.
The 3,500hp take off rating is at the higher boost level.

The Tornado could accommodate the Centaurus in place of the Vulture, but the Typhoon suited the Sabre only.
Likewise the Manchester was proposed as a twin - to use Vulture/Centaurus, but neither was readily
operationally serviceable/available, so the Lancaster adopted quad Merlins/Hercules instead.

The Bristol Hercules & R-R Merlin 'power-egg' units were used on service Beaufighter & Lancaster aircraft,
& the Mosquito trialled the Merlin 'P-E' type against the regular De Havilland installation.

The Halifax also used both Hercules & Merlin, but AFAIR, not the 'power-egg' per se..

 

[JFC Fuller]

Napier only ever ever advertised the Type as a 3,050hp engine. If 3,500 was achieved on a bench (which it probably was as that SHP was offered for an evolved version beyond the VII) it was not an operational engine rating.

Typhoon and Tornado used the same basic wing and rear fuselage, it was the fat Vulture that caused the forward fuselage/engine mounting changes.

Manchester was not merely proposed as a twin but entered service as one, however the Vulture lacked both the power and reliability required for operational use- hence Halifax and Lancaster coming to fulfil the B.12/36 role. The Lancaster Power egg was the Merlin XX Ready to Fly Unit (at least in propaganda).

 

[J.A.W.]

See here for Napier Sabre specs & outputs..

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

Note: the steady increase in boost & power ratings over series development, up to +20lbs/3500hp for T-O.


Manchester was dismal in service , & Halifax, while also proposed as a twin - only saw service as a 4..

Warwick also saw service as powered by a brace of R-2800s (or Centaurus), but was little liked/used..

 

[J.A.W.]

BMW also offered its WW2 radial as a 'power-egg' for Do 217 & Ju 88/188 twins plus some 4/6 (Ju 290/390) use.

 

[J.A.W.]

Important factor to note with fighter engine functionality was the careful attention to ease of operation
paid to controls in German & British applications, such as the BMW Kommando-gerat,
& as listed in the Sabre 7 specs, an equivalent single lever cockpit control set-up..

"Master control uniting throttle, boost, injector, ignition & propeller controls."
& the ADI likewise incorporating automatic ignition & fuel injection over-ride control.

US fighter engine installations tended to keep their pilots much more busy with fettling these factors in flight.

 

[J.A.W.]

A quick squiz at the 'pilots notes' for the Tempest reveals a significant difference in listed Vne speed for the
Centaurus powered Mk II (480mph below 10k ft) & the Sabre powered Mk V (540mph @ same height).

I presume this may have something do with the Sabre being much more tolerant of high rpm..

 

[J.A.W.]

Here, a 'Flight' article gives Sabre 7 performance - charted at up to +17.25lb boost..
& also lists 4,050rpm @ max boost - as allowable for Vne dives.

http://www.flightglobal.com/pdfarchive/view/1945/1945%20-%202284.html

Elsewhere Flight acknowledges "nearly 4,000hp on test" for the Sabre,
Fairly pushing the limits of propeller capacity in 1945?

 

[tartle]

My data says 3,350 hp. for the VIII and 3,055 for the VII...I may get to Kew next weekend ... ??? !!!
As to props absorbing power... the VIII was a contra prop design.
A good omen was being passed by a lorry carrying 'TeaCrates" last time I was there.

 

[J.A.W.]

Ok T, so..
'Aircraft Engines of the World' gives a Sabre 7 take-off rating of 3,500hp at +20lbs boost..
..how do these published figures compare with your data?

Sabre power ratings were revised with increased boost levels, +7, +9,+11,+13,+15, +17.25 & +20lbs.

AFAIR, S. Camm was reportedly irritated by Rotol propellers being unavailable, when De Havilland units
were proving unequal to the task of handling the Sabre - running on increasing boost - for V1 interception..

Kiwi Tempest pilot ( & successful 'rat-catcher' against the Me 262) Ron Dennis commented..

"All our machines were fitted with Rotol airscrews when the maximum rpm were increased to 3,850
from 3,700 & boost to +13lbs from +11, as the De Havilland airscrew could not absorb the added power
& more than once shed a blade, with somewhat detrimental effects..."

& T, - Good hunting @ Kew..

 

[J.A.W.]

From Bill Sweetman's 'High Speed Flight' - re Sabre power..

"Cooling & supercharging were the limits to performance, & when these limits were absent,
in bench runs, the Sabre produced phenomenal amounts of power, easily generating 3,750hp
& capable of being pushed to even higher outputs."

B.S. will maybe have a data set that verifies this assertion?

Or was he simply reiterating Len Setright's stuff?

 

[tartle]

Being published by Janes gives Sweetman's book a higher authenticity rating but in the last months of researching my own book I have found that even the best accept what seems fact and turns out to be just wrong... as documents are relaesed at Kew they enable re-interpretation from the doc rather than memory!!

 

[J.A.W.]

Quite right too, T, & verification via the mother lode of original documents must - of course - take precedence..

Anyhow - here is a bit about the Soviet approach by contrast..

http://mig3.sovietwarplanes.com/mig3/engineam35a.html

 

[J.A.W.]

In this following link, Len Setright states re: Sabre power figures..

"My information came from the wartime R&D department of Napier..."

http://www.hawkertempest.se/index.php/contributions/stories/130-the-greatest-engines-of-all-time-by-ljk-setright

 

[JFC Fuller]

Great, in which case there will be a paper trail somewhere, strange that the Napier Heritage Trust has no record of it and Setright appears to be the only author to have discovered this though.

The Sabre was a great engine, arguably the best design to see service in WW2 from some perspectives. However, the hero worship, and corresponding emotional conspiracy theories about why so few (comparatively speaking) were made, borders on TSR-2 levels of absurdity. The reality is that Napier didn't have the technology to manufacture the engine (it needed Bristol tech), it couldn't make a high altitude configuration and EE ultimately had to be brought in to provide proper management. Even then, it wasn't until 1945 that production and maintenance converged to end the engine supply problems.

 

[LowObservable]

The source was LJKS. Probably just as well that the 3750 hp had a caveat pinned to it about bench runs. However, operational Sabre performance (particularly relative to capacity and frontal area) was indicated by the Tempest's large low-level speed margin over almost anything else - hence its use for Diver and rat-catching. Clostermann reports that escort Spitfires could not keep up with bomb-laden Tempests, even loafing along at moderate boost, and that the only prop that beat him for speed was a Do335.

 

[JFC Fuller]

Indeed, it was an immensely powerful engine, and one suspects that the Sabre VII powered Fury would have easily beaten that Do335 and that the Tempest VI (with it's 2,340hp Sabre V) would have given it a run for its money.