Engine technology free-for-all

[J.A.W.]

Early turbo-jets lacked both long range & short take-off abilities..
& so piston engined fighters were still used for duties such as naval aviation, immediately post-war..

Here are a couple of those seen as classics, the USN Grumman Bearcat & RN Hawker Sea Fury..

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

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

[wuzak]

Did the Pennine ever make production status, pass a 'type-test' or even fly?

No, no and no.

It also didn't benefit from 10 years of development.

[wuzak]

There were a number of factors..

A, There were tens of thousands of cheaply available ex-military engines & airframes suitable for transport use.

B, High performance fighter-aircraft piston engines were largely passé due to the advent of turbo-jets..

C, Post war Britain was broke & had to eke out some viable productive use from its service dependant industries,
but compared to ~125,000 2,000+hp R-2800s built in USA..
.. Britain all told - made fewer than 20,000 Centaurus/Griffon/Sabre 2,000+hp aero engines.

The R-2800 was only a bit player in the post war commercial aviation field. The R-3350 dominated.

Rolls-Royce's airliner engine was, oddly, the Merlin. A bit small, really, meaning it had to be boosted to get the performance. One would have thought the Griffon would be the better bet, but maybe RR were just going through the piston engined motions before jets came into service.

[wuzak]

Early turbo-jets lacked both long range & short take-off abilities..
& so piston engined fighters were still used for duties such as naval aviation, immediately post-war..

Here are a couple of those seen as classics, the USN Grumman Bearcat & RN Hawker Sea Fury..

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

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

The Bearcat is hardly a king of long range.

The Sea Fury is not much better.

The de Havilland Vampire had a longer range than both, and was made into the Sea Vampire post war.

Launching aircraft was helped by catapults - RN carriers had that facility during the war.

[wuzak]

The McDonnell FH Phantom was carrier capable and first flew in 1945.

http://en.wikipedia.org/wiki/McDonnell_FH_Phantom

Its range was similar to the Sea Fury.

[J.A.W.]

Quite a few R-2800s flew & still fly in C-46s & DC-6, & various Convair/Fairchild/Martin types..
& while civil Merlins flew in British/Commonwealth service, they could not economically compete for US use..

The successful naval jet fighters took several years of post-war development - to be competitive,
& especially in the ordnance lifting/A2G role, piston jobs remained on carrier decks through the Korean war..

Nor could the 1st turbo-jets do the long range escort/bomber interceptor/all weather interdiction/recce roles..

See here, a Fury beat the Vampire record for London to Rome..
http://www.flightglobal.com/pdfarchive/ ... 00969.html

[J.A.W.]

Did the Pennine ever make production status, pass a 'type-test' or even fly?

No, no and no.

It also didn't benefit from 10 years of development.

No benefit from 10 years of development?
No wonder it never got off the ground.. ..R-R sadly didn't get far with any of their sleeve-valve efforts..

[Tommy Cookers]

in no particular order .....
piston-engined planes had more endurance ('persistence' not the same as range) than jets, especially useful to naval aviation
eg Corsairs made till 1950, Skyraiders till 60s, (and B-26s)
Beamont said of the (earliest ?) jets that they could not even reach their official top speeds without running out of fuel
and the turboprop (not the jet) was expected for all applications except fighters
though Hives turned down Govt orders for the Clyde

was someone saying the Vulture should have had 1 piece rods, so requiring a 4 throw built-up crankshaft ?

TBO is a regulatory mechanism, based on condition monitoring eg compression test, it could mandate a stripdown long before TBO
TBO can be extended 'on condition' by 40% or more, contingent upon maintenance regimes
RR did a lot of work to get postwar airline Merlins up to a 700 hr life
(on paper the Merlin was better for range eg Canadair Argonaut and Tudor than the usual (larger) radials)
non-TC Wright Duplex Cyclones (ie 3350s) in waterbomber Mars get/got around 2000 hr
even today seperate cylinders are a priceless feature because below-par cylinders can be fixed without disrupting the whole engine
so effectively extending life by hundreds or hours

there was once a 22 cylinder Wright, and Bristol planned the Orion
the airline market was small, but events eg the Berlin airlift and Korean war meant a huge military air transport buildup
all Wright TCs went to the military (ie mostly unpressurised) the airlines only started with the TC later
unique in its power and economy, it enabled airliner modifications to carry more fuel and have serious trans-oceanic range
now pressurised, airliners could benefit, eg the bsfc at 30000' was down to 0.34 lb/hr (exactly equalling the Nomad efficiency)
EDIT - checking the figures, they are 0.37 at sea level and 0.325 at 30000' for the later 7.2 CR version (effic beats the Nomad)

the Wright TC, in recovering exhaust energy to the propellor, was efficiency-matched to rather slow (and low) flight
P&W's compounded development of the 4360 had a variable geometry prop-or-jet recovery system for better high and fast flight
this system required an airframe designed around it (unlike the Wright), and it was never produced

[wuzak]

was someone saying the Vulture should have had 1 piece rods, so requiring a 4 throw built-up crankshaft ?

The Vulture had 6 throws, so would have required 7 pieces.

But no, that suggestion was not made.

[wuzak]

Pratt & Whitney were developing the Variable Discharge Turbine for the R-2800 and R-4360.

The engine would not have a supercharger, like all the big WW2 piston jobs, but a turbo, or turbos, whose speed would be controlled by altering the outlet.

The problem was that the mechanism for controlling the system had yet to be invented, and thus required constant monitoring and adjustemnt for the flight engineer. Not a very practical solution.

The R-4360 VDT was said to give 4300hp.

[Tommy Cookers]

the VDT was intended at speed to reduce the TC exhaust recovery path and open a exhaust jet path ?
the airframe changes (eg needed to the B50) were judged to be excessive

the first airline use of the Wright TC was as a more-or-less 'bolt on' option to the existing design (early DC-7 ?)
this use was to avoid abandoning some US internal routes when the FAA cut flight times to 8 hrs
unrelated to the later aircraft redesigns that allowed huge range (costing speed)

and ..... so-called large overlap (mainly late exhaust valve closure) came in WW2 to cool EV and piston crowns at high meps
eg Merlin and Allison EVC had become much later than R-2800
clearly why the NACA work on increasing TCing showed that the 2800 'PU' gave best efficiency with actual -delta P
but that the Allison 'PU' efficiency was best at 0 delta P

and ..... when fuel quality was raised CRs were usually held and mep/boost raised
this should have increased the exhaust thrust even with the usual simple exhaust systems
so how much exhaust jet thrust (or equivalent hp) would eg a 2000 hp Mustang or Spitfire have had when high and fast ?
(the A380 has 16% jet thrust and 84% fan thrust)
what do the current unlimited air racers have ?
what did the Merlin 1940 'ejector exhausts do ? (these were then dropped) increase crankshaft power ? increase jet effect by entrainment ?

[strad]

boy ,, This thread took off into the wild blue yonder.

[wuzak]

the VDT was intended at speed to reduce the TC exhaust recovery path and open a exhaust jet path ?

Yes, the help use the exhaust thrust. But also eliminate the engine mounted supercharger, relying on turbos only for supercharging, freed up several hundred hp.

the airframe changes (eg needed to the B50) were judged to be excessive

On R-4360 VDT was tried on a B-50. But the flight engineer had to monitor and control it constantly.

and ..... when fuel quality was raised CRs were usually held and mep/boost raised
this should have increased the exhaust thrust even with the usual simple exhaust systems

Higher boost improved performance at low altitude. That is the critical altitude or full throttle height was lower at a higher boost level, above which the extra boost could not be maintained.

Exhaust thrust was far more important at high altitudes, where engine power was reducing and propeller efficiency was lower.

so how much exhaust jet thrust (or equivalent hp) would eg a 2000 hp Mustang or Spitfire have had when high and fast ?

Not sure. There are figures about.

We can say that the Mosquito picked up ~10mph by changing to ejector exhausts.

what did the Merlin 1940 'ejector exhausts do ? (these were then dropped) increase crankshaft power ? increase jet effect by entrainment ?

The aime was to get more exhaust thrust, though the end shape was sometimes modified to reduce exhaust glare for night flying.

The ejector exhausts were refined throughout the war.

[J.A.W.]

A couple of items of topical interest in this page from 'Flight'..
http://www.flightglobal.com/pdfarchive/ ... 01455.html

A, The increased boost ADI equipped Sabre Tempest F6..
.. has adopted a high thrust output exhaust - with a discrete - per port ejector (replacing siamesed ejectors).
& a comment re sleeve-valve engines being muted flame/glare-wise.

B, The civil Merlin with figures showing fairly high boost settings for regular service operations.

[J.A.W.]

Document tabulating WW2 American aero-engine serviceability.. http://www.usaaf.net/digest/t115.htm