Thread: Merlins

I think that a major reason the Merlin stayed in production so long was that it was engineered into a number of very good airframes. Hurricane, Spitfire, Mustang, Lancaster, Mosquito. The very similar Allison V1710 was just as good a performer when built to similar specification, and a far easier engine to maintain, but development of this type was virtually at a standstill from about 1942 because of the very powerful radial engines coming out of Wright, and Pratt & Whitney, and the development in secrecy of jet engines. The US Navy became very aware of the need to get the pilots back on board. US Industry could build aircraft much, much, faster than carrier pilots could be trained. Pilot survivability became an issue, one of the reasons for the ascendancy of the radial over the liquid cooled in-line engines. The radials didn't have a cooling system to be shot full of holes. The radials were also easier to maintain as one cylinder at a time can be serviced. Particularly important in the cramped accomodation of the carriers of the time. There are plenty of recorded instances of radial engined aircraft getting home with a cylinder or more shot off. Radials are much shorter and the space saved was usually filled with fuel tank, which combined with drop tanks gave the long range required for the Pacific theatre and for escorting the bombers in long penetration of Germany, and later the endurance to hang around the battlefield to give ground forces some aerial artillery when called upon. The Spitfire was pretty much a home defence fighter initially with very short range and time in the air.

I haven't read all of the thread and apologise if this has been posted before. If you are interested in Merlins and Spitfires, try to read "Sigh for a Merlin" by Alex Henshaw, Supermarine's head test pilot at their assembly plant in Castle Bromwich during WWII.

Lots of interesting stuff and a few hair raising moments.

Originally Posted by Brian Hjelm

I think that a major reason the Merlin stayed in production so long was that it was engineered into a number of very good airframes. Hurricane, Spitfire, Mustang, Lancaster, Mosquito. The very similar Allison V1710 was just as good a performer when built to similar specification, and a far easier engine to maintain, but development of this type was virtually at a standstill from about 1942 because of the very powerful radial engines coming out of Wright, and Pratt & Whitney, and the development in secrecy of jet engines. The US Navy became very aware of the need to get the pilots back on board. US Industry could build aircraft much, much, faster than carrier pilots could be trained. Pilot survivability became an issue, one of the reasons for the ascendancy of the radial over the liquid cooled in-line engines. The radials didn't have a cooling system to be shot full of holes. The radials were also easier to maintain as one cylinder at a time can be serviced. Particularly important in the cramped accomodation of the carriers of the time. There are plenty of recorded instances of radial engined aircraft getting home with a cylinder or more shot off. Radials are much shorter and the space saved was usually filled with fuel tank, which combined with drop tanks gave the long range required for the Pacific theatre and for escorting the bombers in long penetration of Germany, and later the endurance to hang around the battlefield to give ground forces some aerial artillery when called upon. The Spitfire was pretty much a home defence fighter initially with very short range and time in the air.

The American navy made the decision to ditch liquid cooled engines in the twenties, nothing to do with WW2. Their decision, however was, as you note a desire to get their pilots home. This was the result, not of enemy action, but of the Liberty engine. This engine, designed by a committee of auto engineers for mass production (allegedly on the back of an envelope in a railway carriage or hotel room) featured separate cylinders with welded on water jackets that regularly cracked. Interestingly, their reliability depended on which car manufacturer built them - and Packard's were reputed to be the worst. Built in very large numbers in 1918, they powered much of US aviation until reliable aircooled radials appeared in 1927.

As these were developed, they became the engine of choice for commercial aircraft in the late twenties and thirties (from the Southern Cross to the DC-2,3,4 etc), with little effort being put into liquid cooled engines, so that both manufacturing capacity and development of US aircooled radials was way ahead of European practice, as their liquid cooled expertise was behind. Add to that the Navy's aversion to liquid cooled engines, and the lack of a separate airforce, and it is little wonder that the best US aircraft had aircooled engines.

John

Originally Posted by JDNSW

The American navy made the decision to ditch liquid cooled engines in the twenties, nothing to do with WW2. Their decision, however was, as you note a desire to get their pilots home. This was the result, not of enemy action, but of the Liberty engine. This engine, designed by a committee of auto engineers for mass production (allegedly on the back of an envelope in a railway carriage or hotel room) featured separate cylinders with welded on water jackets that regularly cracked. Interestingly, their reliability depended on which car manufacturer built them - and Packard's were reputed to be the worst. Built in very large numbers in 1918, they powered much of US aviation until reliable aircooled radials appeared in 1927.

As these were developed, they became the engine of choice for commercial aircraft in the late twenties and thirties (from the Southern Cross to the DC-2,3,4 etc), with little effort being put into liquid cooled engines, so that both manufacturing capacity and development of US aircooled radials was way ahead of European practice, as their liquid cooled expertise was behind. Add to that the Navy's aversion to liquid cooled engines, and the lack of a separate airforce, and it is little wonder that the best US aircraft had aircooled engines.

John

The Liberty was still in production throughout WWII and used in boats and armoured vehicles. Packard were making them, and Hall-Scott, as was Morris Motors (Lord Nuffield) in the UK. Many of the US Navy's torpedo boats had three Liberties. Hall-Scott were also making their own designs used in work boats, and heavy military vehicles. They made an in-line six cylinder single OHC engine of 17.6 litres, an engine of imposing size and magnificent appearance when restored, painted and polished. The torpedo boats also had Merlins as did the RN's MTB's and MGB's. Vosper also made "Fairmiles" using UK produced Isotta-Fraschini engines they acquired the rights to pre-war. RAF air-sea rescue boats also used three Merlins, and later three Griffons. The fuel bill for three Griffons must have contributed greatly to the UK's war debt.

I love the spitfire!

It is by far my most favored aircraft of all time and sounds brilliant , unfortunately all i have is a model

Originally Posted by Brian Hjelm

The Liberty was still in production throughout WWII and used in boats and armoured vehicles. Packard were making them, and Hall-Scott, as was Morris Motors (Lord Nuffield) in the UK. Many of the US Navy's torpedo boats had three Liberties. Hall-Scott were also making their own designs used in work boats, and heavy military vehicles. They made an in-line six cylinder single OHC engine of 17.6 litres, an engine of imposing size and magnificent appearance when restored, painted and polished. The torpedo boats also had Merlins as did the RN's MTB's and MGB's. Vosper also made "Fairmiles" using UK produced Isotta-Fraschini engines they acquired the rights to pre-war. RAF air-sea rescue boats also used three Merlins, and later three Griffons. The fuel bill for three Griffons must have contributed greatly to the UK's war debt.

I was nearly going to add the bit about the use of Liberty engines in WW2, particularly as a tank engine. The Hall-Scott engine you mention was probably also derived from one of their WW1 aeroplane engines that was markedly unsuccessful.

I have a fascinating autobiography of one of Vosper's engineers. In it he recounts a visit to Isotta-Fraschini before Italy entered the war. In this visit he was trying to push the production of the engines, and was told the holdup was on the Bosch magnetos. He recounts listening across the desk as the manager phoned Bosch and abused them for late delivery of them. Incidentally he also says that the engines were not made in Britain but were imported, and when Italy entered the war, they were unable to deliver any boats due to a lack of engines, until Packard commenced manufacture of marinised Merlins (production capacity in the UK could not be spared for non-aero uses of the Merlin.

John

The Allison V1710 ran out of puff at higher density altitudes until they packed on the superchargers.. but by that time the Merlin was established.

From vnx205

It would never have occurred to me that they might have to do some sort of acrobatic manoeuvre at the start of an engagement just to make sure the engine didn't die on them in the middle of a dogfight.

Carbies take a lot of management in flight even now (many light A/C still use them). Any 0 or negative G will have you splutter / windmill in no time.. and that takes some getting used too ! Also think about oil and engine lubrication.. Oh and carbie icing kills, too.

The maneuver is called a wing-over.. you can see it in almost all WWII films when the A/C break formation and 'peel off' into a dive. Its spectacular.. and great for the pilot to visually assess the theater as you get views in pretty much every direction.

Originally Posted by flagg

The Allison V1710 ran out of puff at higher density altitudes until they packed on the superchargers.. but by that time the Merlin was established.

The Allison in its P38 format had the high altitude capacity and performance that the Merlin never had until the Mark 61 or 63 got the twin stage two speed and intercooled superchargers. The Allisons in the P38's had a turbocharger, intercooler and a centrifugal supercharger. This gave the P38 Lightning its outstanding ceiling and high altitude performance. The Lightnings swept the land based Japanese air force out of the Pacific theatre operating from altitudes that the Japanese aircraft simply could not reach. They had it all, high speed, high ceiling, fast dive, fast climb, stable and heavily armed, not to mention the long range needed for the Pacific theatre. Conversely its specification for the Pacific was a drawback in Europe as they were not built to operate in the severe cold of Europe's high altitudes and engine failures were common at first. All high performance aircraft engines of that era were supercharged or turbocharged or both. It was Stanley Hookers 2 x 2 superchargers that changed the Merlin from a fairly ordinarily performed engine into a good one. They gave it ceiling and high altitude performance by restoring take off horsepower at higher altitudes.

As an aside GM's Allison Division made over 70,000 of them, as well as making most of the slipper bearings used buy the other US aero engine makers.