Alternative engines and aircraft

[PMN1]

The Lancaster, Halifax and Beaufighter were all flown with different engines to guard against the possibility of a reduced supply or failure of the original engine.

Also, if possible more than one of each type of specification was ordered in case of failiure with one of the designs.

Given this development, it seems strange that EVERYTHING was gambled on the Merlin Hurricane and Spitfire when there were alternatives such as the Gloster F5/34 (Mercury) and Vickers Venom (Aquila) which from what I have read had roughly the same performance a the original Hurricane and the Bristol 153 (Hercules engine) which could have given the Spitfire a run for its money.

Does anyone know why, was it a case that the Merlin was considered so reliable there wouldn't be a problem, were the Bristol, Vickers and Gloster designs considered 'undevelopable' even with newer engines?


Also numerous designs had varients with different engines - Lancaster, Beaufighter, Wellington, Tempest, Fury etc

Was any compromise in airframe and wing needed to be able to use different engine types?

[GregP]

Look at the Hawker Typhoon and Tornado. They were essentially the same airframes with different engines.

Aircraft design is a funny thing, and many factors are involved. In just one example, the Messerschmitt Bf 109 was designed for the Daimler-Benz DB601/603/605 engines. When retrofitted with a Merlin, the Spanish Messerschmitts were almost deadly to fly since the Merlin turned in the opposite direction to the BD engines.

Last, alternate engines may or may not have been successfully developed into reliable powerplants.

Witness the Rolls-Royce Vulture versus the Merlin. COULD it have been made reliable and COULD it have replaced the Merlin? Probably, but then you'd be asking "What's wrong with the Merlin?"

I beileve the decisions at the time were based on how they could use the limited development resources and time available to best come up with a reliable and powerful piston aircraft engine to combat the Germans on equal or better-than-equal terms BEFORE the war was lost. The engineers probably convinced everyone involved that the Merlin was closer to being "service-ready" than any other powerplant currently in development at the time ... and that is probably why the decision was made as it was.

Surely someone in Merry Old England knows more about Rolls-Royce than I do! C'mon guys, chime in here.

As far as British engines go, there were a few to chose from, but how much development work was needed after 1939 or so? Seems to me that the Merlin was the best liquid-cooled inline engine available in the 1938 - 1940 timeframe as far as state-of-development was concerned.

The American Allison was a good engine (as was the Hispano-Suiza), but it needed more development to be close to the Merlin in specific output and altitude capabilities. It need a supercharger, turbocharger, or turbo-supercharger. Lack of engine development and lack of a "charger" made the Merlin simply the best available inline engine at the time available to the Allies.

As far as radials are concerned, there were several good ones. I lean toward the American R-2800, R-3350, and R-4360 as the best (though the 3350 and 4360 DID have development troubles ...), but the Bristol Centaurus was also a good engine. The Japanese used radilas almost exclusively since their supply of mechanics were familiar with radials. Their forays into liquid-cooled inlines were not very successful ... mostly due to time and resource constraints.

There were many altrernative engines of the radial variety but, again, there was only so much time, manpower, and money to do the job ... and the R-2800 performed very well in the existing aircraft.

This can be applied to the Germans as well. They never DID have a mass-produced 2500hp engine that was reliable and service-ready. Was it beyond their capability? No.

It was beyond their resources at the time and beyond the time available for completion of the project in order to do the war effort any good. Germany had lost the war by the end of 1942, but it took time to complete the job. By the end of 1942, the Germans had a severe resource problem coupled with a severe raw amterial problem. If a 2500 hp, service-ready engine HAD been developed, then they would have needed a quick aircraft design to make use of it, and the capability to produce the airframes and FUEL them.

Many German planes were completed ... all except for propellers and fuel. A new engine would not have changed that.

Any other opinions?

[ChrisMcD]

As I understand it the Vickers Venom was a development of the Jokey lightweight fighter and was not able to carry the warload (ie 8 machine guns) needed. Also it was tricky to fly and was crashed after a flat spin.

I think that the Bristol and Gloucester machines were later than the Spitfire and Hurricane and fell foul of politics to a certain extent.

Hawkers bought Gloucester and did not fancy a competitor, so the design team was pointed at twin engined fighters and jet fighters (both are known by their Spec nos which I forget).

Bristol were preoccupied with Blenheim, Beaufort and Beaufighter plus Frank Barnwell had killed himself.

[Mark J]

The P-40 was a P-36 with an inline engine until they lengened the fusalage.
The Lagg-3 had an inline, replaced with a radial to become the La-5.
Kawasaki had a good inline engined fighter then they gave it a radial.
The Italians did engine swaps on many of their aircraft.

I think these changes were made to continue development with the resources available at the time.

[Lightning]

Hi GregP,

In the oppinion of many (myself included), the Allison engine was more reliable than the Merlin and a better performer at low altitudes. Also, the Merlin had a mechanical supercharger for high-altitude operations. It seems that I read it used both one- and two-stage superchargers.

Regards,
Lightning

[Mark J]

The high altitude 60 series Merlin as used by the mk IV Spitfire and the P-51 B,C,D had the two speed two stage supercharger with an intercooler between the supercharger and the carberettors.
The Allison had a small single speed, single stage supercharger which did little to improve performance other than at low altitude.
A Rolls Royce supercharger on an Allison inline engine is one of those big "if's", if Allison had developed their unit like RR did.
Turbo chargers require heat resistant steel alloys as they are exhaust driven but superchargers are mechanically driven ( and often heavier ) and don't need those high tech metals, which are not always easy to come by.

[ChrisMcD]

The Allison was an earlier engine than the Merlin and had more time to be developed into a reliable version (remember the early 'ramp head' Merlins).

But, the ultimate owners of Allison (General Electric?) kept them short of cash, with the result that they were overstretched (North American never forgave them for the delays in supplying the engine for the prototype Mustang) and Allison supercharger development was inconsistent (early in the Lightning but late in the P40).

Finally the RAF had problems with brass main bearing wear in the desert ("goldfish in the filters") so the Allison was not perfect in terms of reliability.

[Mark J]

I thought the RAF P-40's,Tomahawks, didn't have sand filters ( volks ) so engines were sucking in grit and grinding out main bearings. Hurricanes and Spitfires had the filters so their Merlins lasted longer but the bulky filters slowed the planes down. Kind of a loose, loose situation.
Just about any engine without a decent filter would suffer in the dessert.

[Lightning]

Hi All,

As to the Allison's reliability, after the war, these engines were used for other-than-aircraft purposes. They were used in racing boats, and , I believe, in racing cars. Also, they were used in the oil fields, which is where the owner of the P-38 that used to be based at New Garden Airport in New Jersey got one that he needed.

To the best of my knowledge, these engines performed well and reliably under harsh conditions for which they were not designed. I also believe that the "mean time between failures" (MTBF for you reliability engineers out there) was significantly longer for the Allison than for the Merlin.

Regards,
Lightning

[Weaver]

quote:Originally posted by ChrisMcD

As I understand it the Vickers Venom was a development of the Jokey lightweight fighter and was not able to carry the warload (ie 8 machine guns) needed. Also it was tricky to fly and was crashed after a flat spin.


Yes and no: the aircraft that couldn't carry the guns and crashed in a flat spin was the Vickers 151 (from memory) that preceded the Venom. The Venom carried the guns from day one (even on the prototypes) and although it looked a little crude, it actually flew magnificently. It made 312mph on just 625hp, mainly because it was so light, and had very easy maintainance, the whole engine assembly swinging sideways on a big hinge to get at it.

I can't help feeling that a beefed-up version with an 850hp Mercury would not only have been a lot more use than the Gladiator, but would also have made a good single-seat carrier fighter for the FAA, had they not had their dogmatic insistence on two-seats (despite which, they still bought some Sea-Gladiators).

[ChrisMcD]

Hi Weaver,

I agree the Vickers fighters would appear to be the basis for great naval aircraft with a decent radial, and surely they could have spared some Mercury's from all those Blenheims.

But, I still hark back to their reputation for poor handling.

Remember 'Winkle' Brown rejected the Miles M20 because it was too tricky to deck land (mind you he was not that keen on the Corsair).

[Weaver]

ChrisMcD: Every reference I can find says that the Vickers Type.279 Venom had superb handling. The Type.151 Jockey had poor handling because it's fabric-covered rear fuselage wasn't rigid enough and allowed the tail to twist. The Venom had a metal-covered tail cone which solved the problem.

Seems I'm not the only one to have this idea: it's also occured to a modeller too:

http://moneycentral.groups.msn.com/TheWhatifandoddballmodelpage/vickersseavenomiii.msnw?albumlist=2

[ChrisMcD]

Hi Weaver, Cannot find any comments on Venom's handling, but it makes sense that Vickers would have sorted out the Jockey's problems if this was a development series and they were competing in a new competition

What I have come across is the comment that the problem was the Bristol Aquila engine - which was one of the first sleeve valve designs. It was nice and compact with a very small frontal area.

http://1000aircraftphotos.com/APS/1960.htm

But Bristol decided the Aquila was not powerful enough and concentrated on the twin row Taurus development (and they took ages to sort that out for the Beafort!)

So I would guess that when Vickers needed increased power for the Venom they would have had real problems getting another engine to fit!

[Wuzak]

quote:Originally posted by Lightning

Hi All,

As to the Allison's reliability, after the war, these engines were used for other-than-aircraft purposes. They were used in racing boats, and , I believe, in racing cars. Also, they were used in the oil fields, which is where the owner of the P-38 that used to be based at New Garden Airport in New Jersey got one that he needed.


Merlins were used in all manor of military vehicles - from tanks to patrol boats.

Of course they didn't have superchargers in those installations.

I know that the Merlin has been used in cars since WWII - a guy in England built a Rolls Royce chassis with one, and a hot rodder here in Australia has put a (Packard built) Merlin into a '55 Chev (or was it a '57?).