could the Allison engine have done what the Rolls Royce Merlin did?

[Koopernic]

If Britain faced a shortage of Merlins it could theoretically have powered the Lancaster, Wellington, Halifax & Beaufighter with the Allison. It was a while before the two speed superchargers were used on the Merlins I believe.

The turbo-charged Allision probably could have been fitted to these British bombers. A Turbo charged Allison on a Lancaster might give it quite a good altitude performance, perhaps as good as the Liberator.

USAAF policy seems to have been to use simple single speed single stage non intercooled superchargers, some were two speed superchargers without intercooling, for low flying aircraft and turbo-superchargers for high altitude. This infamously left the P39, P40 and P51A with poor altitude performance while the P-38 went through years of extended debugging and the P-47 was still in development.

The US Navy had quite a different policy, it used multispeed multi stage superchargers with independent stage drives and intercooling. Eventually these navy R2800 engines did find themselves on some USAAF aircraft.

Unfortunately the USN never used the Allison and aircraft (only air ships), had it have chosen too it might have provided the funds and impetus to develop a mechanical superchargers for the Allison.

 

[wuzak]

If Britain faced a shortage of Merlins it could theoretically have powered the Lancaster, Wellington, Halifax & Beaufighter with the Allison. It was a while before the two speed superchargers were used on the Merlins I believe.

All those aircraft you listed used two speed Merlins.

The Lancaster and Beaufighter had Merlin XXs (the latter was because of possible supply problems with the Hercules).

The Halifax started life with the Merlin X, before later getting the Merlin XX and then the Hercules.

The Wellington Mk.II had the Merlin X. Most had the Hercules, however.

The Whitley Mk IV had a single speed Merlin until late production models, which had the X. The Whitley Mk V had the Merlin X, first flying in late 1938.

The turbo-charged Allison probably could have been fitted to these British bombers. A Turbo charged Allison on a Lancaster might give it quite a good altitude performance, perhaps as good as the Liberator.

Yes, a turbocharged V-1710 would have worked in the Lancaster, probably not worth it on the others.

However, there would have been a lot of redesign necessary to fit the turbocharger, intercooler, etc.

 

[wuzak]

Unfortunately the USN never used the Allison and aircraft (only air ships), had it have chosen too it might have provided the funds and impetus to develop a mechanical superchargers for the Allison.

The Bell XFL-1 Airabonita was a V-1710 powered aircraft proposed for the USN, but not adopted.

 

[Shortround6]

Two speed Merlins (the Merlin X) were shown at the 1938 Paris air show/exhibition. And were just starting squadron service in Whitleys out the outbreak of the war.
The Merlin XX with two speed supercharger was in production in the late summer of 1940.

Any British bomber trying to use Allisons in late 1939 or the first part of 1940 would have been in big trouble. All Allisons manufactured for the US up until that time had to be derated in service (max rpm 2770) until they could be sent back to the factory and rebuilt.

In 1939/40 the Allison used in the P-40 was the highest altitude Allison they could build. Itis a myth to claim that a two speed supercharger drive would have improved anything except take-off power.

US "Policy" in 1939/early 40 was to get planes that would actually work, Which the turbo equipped prototypes often didn't. It also took P & W a while to fully sort out the 2 stage supercharger used in the Wildcat. Early planes suffered from breakdowns in airflow and compressor stall which was manifested in rumblings in the supercharger ducts.
Having planes with a low service ceiling beat having no planes at all.

 

[wuzak]

In 1939/40 the Allison used in the P-40 was the highest altitude Allison they could build. Itis a myth to claim that a two speed supercharger drive would have improved anything except take-off power.

Of course if your engine already is rated to a (relatively) high altitude, the second gear helps low down power, which had been sacrificed for the altitude performance.

And the improvement in take-off power is why the UK bombers got the X and the Spitfire and Hurricane didn't (the Hurricane dd get the XX at the end of 1940).

 

[Shortround6]

You are quite right. this story about the US aircraft at the beginning of the war being "low altitude" gets wide circulation but has little basis in fact.

They may have been low altitude due to being heavy for the available engine power, but the Allison in 1940 was not that far behind the Merlin III and was ahead of the DB601 (at least some models).

The reason the US radials got two speed superchargers was to help take-off performance of large transports and bombers.

 

[Koopernic]

SNIP

In 1939/40 the Allison used in the P-40 was the highest altitude Allison they could build. Itis a myth to claim that a two speed supercharger drive would have improved anything except take-off power.

US "Policy" in 1939/early 40 was to get planes that would actually work, Which the turbo equipped prototypes often didn't. It also took P & W a while to fully sort out the 2 stage supercharger used in the Wildcat. Early planes suffered from breakdowns in airflow and compressor stall which was manifested in rumblings in the supercharger ducts.
Having planes with a low service ceiling beat having no planes at all.

A two speed single stage supercharger on the V-1710 would have done much more than increase take-off power. It would have provided 100hp more power all the way to 9200ft if the Merlin 27 (two speed) used in the Hurricane IV versus the Merlin 46 (single speed) Used in the Spitfire Vc. The lower first stage speed is more efficient leading to loss in parasitic shaft power and less preheating of the mixture and therefore increased boost. Speeding up the second gear may not yield much but it may have been compromised to yield reasonable low altitude performance. What two speeds would allow is the introduction of a larger impellor, no more than 10% greater diameter) that was more efficient a high altitude. I wouldn't be much of a gain but it would be something.

And who knows where this might have lead. Junkers improved the Jumo 211 not only with a two speed supercharger but intercooling which gave over 1500hp at high altitude on 87 octane.

The problem with turbosuperchargers in the US was that they were so bulky and tightly packe a reliable installation couldn't be made on single engined aircraft. There are only a few solutions
1 Integrate them only in twins using the nacelle space
2 Make a special airframe eg the P47
3 Integral turbo charger where the manufacturer builds the turbo, intercooler into a unitary body. This was the route the Germans went after having learned the lesson of the Fw 190 Kangaroo but the effort was abandoned as not worth while though they made integral turbos for the BMW801 (retaining two speed supercharger on top of the turbo)

 

[Shortround6]

A two speed single stage supercharger on the V-1710 would have done much more than increase take-off power. It would have provided 100hp more power all the way to 9200ft if the Merlin 27 (two speed) used in the Hurricane IV versus the Merlin 46 (single speed) Used in the Spitfire Vc. The lower first stage speed is more efficient leading to loss in parasitic shaft power and less preheating of the mixture and therefore increased boost. Speeding up the second gear may not yield much but it may have been compromised to yield reasonable low altitude performance.

While what you say is true it also condenses the time frame by several years.
In 1939-40 using the existing Allison supercharger going to a two speed drive is not going to gain much at all except in in take-off/low altitude power, Very low altitude power.

The Hooker modified supercharger didn't exist at this time and the supercharger on the Merlin 46 was still a considerable period of time away.

The Long nose Allison was rated at 1040hp at 12,800ft with backfire screens. some sources give bit higher altitude, like 14,300ft. The engine was also rated at 1040hp for take-off. Unlike the Merlin III.
However the long nose Allison had a few problems which probably prevented trying to drive a higher supercharger gear for better high altitude performance (the famous 9.60 gear).

Please note the C-15 engine (V-1710-33) used in the early P-40s had the following changes from earlier C series engines.
Improved supercharger thrust bearing and change from 6.23 gears to 8.77 gears.
Heavier 15 blade impeller of improved design instead of 12 blade impeller.
Rotating steel inlet guide vanes.
Bendix 3 barrel carburetor instead of a two barrel carburetor
Larger supercharge cover to accommodate the bigger carburetor.
Modified supercharger diffuser.

There were other changes but those are the ones done to the supercharger to improve altitude performance.

US had an advantage in that the engine was designed to use 100/100 fuel instead of 87 octane fuel.

However the early C-15s had structural problems and the first 228 built had to be recalled and fitted with new crankshafts, crankcase and a few other parts to make rated power. Until that was done they were de-rated to 2770rpm and 950hp for take-off and 950hp at 8,000ft.

Ability of an unmodified engine to turn 9.60 gears for improved altitude performance is subject to question even if such gear had been available and even if such gear had stood up to the load (which they did not in the Nov-Dec 1941) D and E series engines.

Grafting the Merlin 46 supercharger and most especially the Merlin 27 drive onto the back of an Allison would be a major undertaking. perhaps it is one that should have been done. but it would have been at a different time than the C-15 productin was going on. and perhaps the people in charge did not want to approve the drop in production that would have meant. Allison built 502 engines in July of 1941 and over 1100 in Dec of 1941 and stayed between 1039 and 1379 per month for all of 1942. When in 1942 would have been a good time to loose several hundred engines when the change was made?

 

[tomo pauk]

A two speed single stage supercharger on the V-1710 would have done much more than increase take-off power. It would have provided 100hp more power all the way to 9200ft if the Merlin 27 (two speed) used in the Hurricane IV versus the Merlin 46 (single speed) Used in the Spitfire Vc. The lower first stage speed is more efficient leading to loss in parasitic shaft power and less preheating of the mixture and therefore increased boost. Speeding up the second gear may not yield much but it may have been compromised to yield reasonable low altitude performance. What two speeds would allow is the introduction of a larger impellor, no more than 10% greater diameter) that was more efficient a high altitude. I wouldn't be much of a gain but it would be something.

The V-1710 with a bigger impeller would've been a net gain, even if it featured just 1-speed drive for the impeller.

And who knows where this might have lead. Junkers improved the Jumo 211 not only with a two speed supercharger but intercooling which gave over 1500hp at high altitude on 87 octane.

Junkers didn't improved the 211 with a 2-speed S/C drive, it was already there. They did improve the 210 with 2-speed S/C drive.
Jumo 211 never did more than 1300 HP at altitue (talk 5 km and above), the 1500 HP power was achieved at low level. The turbocharged 211Q did it, but it it was not used on a service aircraft.

The problem with turbosuperchargers in the US was that they were so bulky and tightly packe a reliable installation couldn't be made on single engined aircraft. There are only a few solutions
1 Integrate them only in twins using the nacelle space
2 Make a special airframe eg the P47
3 Integral turbo charger where the manufacturer builds the turbo, intercooler into a unitary body. This was the route the Germans went after having learned the lesson of the Fw 190 Kangaroo but the effort was abandoned as not worth while though they made integral turbos for the BMW801 (retaining two speed supercharger on top of the turbo)

The P-43 was certainly a 1-engined aircraft, not some 'special airframe' so the turbocharger can be used.
Germans made a mistake by not pressing the turboed BMW 801 in service on Fw 190 (not that making such a Fw 190 would've changed the outcome of the war by a single jota). The Kangaroo installation was appalling indeed.

 

[drgondog]

Great post, indeed.

There was no major hurdle to install the two stage V-1710 (the 'normal' drive equivalent of the E-11 installed in the P-63A) in the P-51 airframe and send it in the ETO in 1944. The altitude performance would not be on par with the Merlin Mustang, esp. vs. the early models with the high altitude V-1650-3, but it should be enough for a decent performance advantage vs. the LW opposition.
Another approach could've been the single engined fighter with turbo V-1710, something along the lines of the XP-60A (3 view). The plane based around that power-plant was feasible as early as P-38.

Actually Tomo - the auxiliary second stage was an absolute no-go from NA-73 through NA-122. The added required movement of the engine in front of the firewall made a complete re-design including moving the wing forward, larger empenage - based on AAF and GM request to 'look and see', layouts were made in response. It was only after much whining and some sympathy from AAF was the Allison tried in the P-51J.

 

[Shortround6]

People may be ignoring the materials limitations of the time.

Turbo compound Allison at the end of the war. Extra power from the turbine, over and above that needed to drive the auxiliary supercharger was routed through the driveshaft into rear of the engine to the crankshaft.

Granted this engine was operating at much higher pressures and temperatures than early war engines did but it was found that they needed to inject water/alcohol into the exhaust system to keep the inlet temperature to the turbine within limits or risk turbine blade failure.

I have never seen it it written out but there may have been a very good reason that US turbos were mounted a number of feet away from the engine and usually with a number of feet of the exhaust duct exposed to the open air before it reached the turbine. Only the P-47 enclosed the turbine and it was quite a number of feet from the engine.

Trying to closely package the turbine to the engine just because you had room(?) might not have been a good idea?
Again I can't prove it but please remember there was quite a bit of work going with different turbos and uprated materials and rpm limits as the war went on.
Saying they should have done XXX in 1941 because they could do it in 1944/45 may not be correct.

 

[tomo pauk]

...I have never seen it it written out but there may have been a very good reason that US turbos were mounted a number of feet away from the engine and usually with a number of feet of the exhaust duct exposed to the open air before it reached the turbine. Only the P-47 enclosed the turbine and it was quite a number of feet from the engine.

Trying to closely package the turbine to the engine just because you had room(?) might not have been a good idea?
Again I can't prove it but please remember there was quite a bit of work going with different turbos and uprated materials and rpm limits as the war went on.
Saying they should have done XXX in 1941 because they could do it in 1944/45 may not be correct.

The last sentence is right on the money - the internally-cooled turbine blades were not used on turbochargers (in service, not what people had on the test benches) before 1944. Germans started some time in mid 1944 on BMWs powering the Ju 388, the Americans used it on the turbo for the Curtiss SC Seahawk (about 1000 turbochargers manufactured by Wright).

'Early' American approach worked on the technology of the day.

 

[GregP]

When the US sent out the actual requirement that resulted in the Allison V-1710, it specified a single-stage supercharged engine and, if a higher altitude capability was desired, the aircraft could use the newly USAAC-developed turbo-supercharger, or turbocharger as we call it today. The USAAC overestimated the state of development of its own turbocharger. General Electric was the sole source of American turbochargers during this period and for most of the US involvement in WWII.

The Allison Engine Company built engines to order, and the government ordered what they wanted. Over 60% of the post-1941 pursuit aircraft were powered by the Allison V-1710 that were almost all single-stage supercharged engines either with or largely without the turbocharger. The early V-1710's were about 1,000 HP and the late P-38L was 1,600 Hp, while the final V-1710-143/145 was rated at 2,300 HP maximum.

Improvements in manufacturing brought the cost down from $25,000 to $8,000 and allowed the installed lifetime to be increased from an initial 300 hours to as much as 1,000 hours for the less-stressed powerplants. Weight increases were minimal with the result that all models were able to produce more than 1 pound per horsepower at takeoff rating.
Comparisons with the Merlin are inevitable. What CAN be said is the Allison made more power with less boost, had a longer time between overhauls, and did so with a parts count that was nearly half that of the Merlin (around 7,000 Allison parts versus 11,500+ Merlin parts). There was a high degree of commonality of parts throughout the series and individual parts were produced to high degree of standardization and reliability. The Allison was not particularly vulnerable to ground fire though the liquid cooling systems used had various degrees of same.

Saying the above does not detract from the Merlin engine at all. Rolls Royce developed a very good supercharger thanks to Sir Stanley Hooker. It virtually made the difference in that engine family, though there were other improvements as well.

The original Bell P-39 prototype had a turbosupercharger that was specified by Ben Kelsey and Gordon Saville. Numerous changes were made while Kelsey was busy with P-38 work, and the turbocharger was deleted, making the P-39 a low-altitude fighter that was not suited to Europe's higher altitude requirements. The P-39 was rejected by the British but was used by the U.S.A. in the Mediterranean and Pacific Theaters, and particularly by the Soviet Union in large numbers. In the P-39, Soviet fighter pilots scored the highest number of individual kills made in ANY US or British fighter type, primarily because the Soviet war was a tactical, short-range, low-altitude war.

The Allison V-1710 initially had some issues in Europe. Some of the issues were: 1) Poor intake design (Allison), 2) poor regulation of the turbocharger temperature (GE), different fuel formulation from that used for development (not sure it was anyone's fault). The P-38 also had a very poor cockpit heater, which was a major problem in Europe's higher-altitude environment. Last, one of the biggest issues was poor or almost complete lack of pilot training on good flying practices when entering combat areas. The intake design, fuel issues, cockpit heater, and pilot training were "fixed" within a year, but the temperature regulation of the turbochargers was never really fixed by General Electric.

Today, Allison V-1710 engines are smooth and reliable in warbird use when built with "late" 100-series internal parts regardless of the dataplate "dash" number. Merlins are likewise reliable. Today, there is no high-altitude requirement for either engine and both are used with little thought of engine failure unless the use is for racing.

 

[wuzak]

When the US sent out the actual requirement that resulted in the Allison V-1710, it specified a single-stage supercharged engine and, if a higher altitude capability was desired, the aircraft could use the newly USAAC-developed turbo-supercharger, or turbocharger as we call it today.

Actually the turbocharger was developed by General Electric. This was initiated by NACA and then funded by the USAAC.

Not many aircraft engines had a supercharger with more than one stage when the V-1710 program was initiated in 1929. Some didn't even have a supercharger at all.

The USAAC overestimated the state of development of its own turbocharger. General Electric was the sole source of American turbochargers during this period and for most of the US involvement in WWII.

GE was the sole source of production turbochargers for the USAAC/F for the duration of the war. Other turbochargers were trialled, but never went into production.

GE was also the source of most of the aero industry's supercharger designs for most of the 1930s. This included Allison.

The Allison Engine Company built engines to order, and the government ordered what they wanted.

All engine manufacturers built engines to order. No pint building 1,000 engines that nobody wants of can use.

Improvements in manufacturing brought the cost down from $25,000 to $8,000 and allowed the installed lifetime to be increased from an initial 300 hours to as much as 1,000 hours for the less-stressed powerplants. Weight increases were minimal with the result that all models were able to produce more than 1 pound per horsepower at takeoff rating.

The cost fell with the increase in production. Not really related to any engineering improvements.

Comparisons with the Merlin are inevitable. What CAN be said is the Allison made more power with less boost, had a longer time between overhauls, and did so with a parts count that was nearly half that of the Merlin (around 7,000 Allison parts versus 11,500+ Merlin parts).

Oh no, not the parts count again! Considering that most of the difference was composed of extra fasteners. And is the comparison like-for-like? That is, are we comparing single stage, single speed version of the Merlin with the V-1710, which, as you noted, was almost always single stage, single speed.

Of course the fact that the Merlin was typically rated at higher altitudes had no bearing on this. If it is true at all.

The early V-1710's were about 1,000 HP and the late P-38L was 1,600 Hp, while the final V-1710-143/145 was rated at 2,300 HP maximum.

That 2,300hp version was at 100inHg manifold pressure. Meanwhile the Packard V-1650-9 was not far behind on a mere 90inHg manifold pressure.

here was a high degree of commonality of parts throughout the series and individual parts were produced to high degree of standardization and reliability.

And Merlins were hand crafted by fitters using files and feeler gauges and drilling holes in-situ?

Hasn't that been debunked enough?

The V-1710 was modular, so that the core engine could be configured in different ways - for extension shafts, as a pusher, regular, single stage or two stage supercharger, etc. That is a blessing in someways, but in others it was a downfall. Much time was spent doing these extra options before the engine was fully sorted.

The original Bell P-39 prototype had a turbosupercharger that was specified by Ben Kelsey and Gordon Saville. Numerous changes were made while Kelsey was busy with P-38 work, and the turbocharger was deleted, making the P-39 a low-altitude fighter that was not suited to Europe's higher altitude requirements. The P-39 was rejected by the British but was used by the U.S.A. in the Mediterranean and Pacific Theaters, and particularly by the Soviet Union in large numbers. In the P-39, Soviet fighter pilots scored the highest number of individual kills made in ANY US or British fighter type, primarily because the Soviet war was a tactical, short-range, low-altitude war.

The XP-39 with turbocharger was a turd. It never had the performance promised, and likely not even the performance of the modified XP-39 without turbo.

The Allison V-1710 initially had some issues in Europe. Some of the issues were: 1) Poor intake design (Allison), 2) poor regulation of the turbocharger temperature (GE), different fuel formulation from that used for development (not sure it was anyone's fault). The P-38 also had a very poor cockpit heater, which was a major problem in Europe's higher-altitude environment. Last, one of the biggest issues was poor or almost complete lack of pilot training on good flying practices when entering combat areas. The intake design, fuel issues, cockpit heater, and pilot training were "fixed" within a year, but the temperature regulation of the turbochargers was never really fixed by General Electric.

The problem wasn't really the regulation of turbocharger temperature, but rather regulation of the turbocharger speed, which was controlled using the wastegate. The problem was the wastegate would get stuck closed, sending too much exhaust through the turbine and causing the unit to overspeed.

Fun fact, for an engine designed to be used with the turbocharger, it was a long time before a V-1710 was tested on an engine stand with a turbocharger (1939 or 1938, after the XFM-1 and XP-37 flew with turbos). The aircraft manufacturers just slapped them on.

 

[fastmongrel]

And Merlins were hand crafted by fitters using files and feeler gauges and drilling holes in-situ?

Wasn't the Merlin handcrafted in a little shop in Saville Row. When a young gentleman joined the RAF he would travel to London and be measured up for his bespoke Spitfire. "Does Sir wear his supercharger on the left or the right and would Sir like pinstripe camouflage or tweed camouflage for European travel"

 

[GregP]

Hi Wayne,

To address your post above.

1) GE developed the turbocharger at the request of the USAAC/USN, using government money.

2) I clearly stated GE was the sole source if you read it.

3) The US government owned the Allison type certificate. It was also the ONLY V-12 that passed the 150-hour type test during the war. Rolls Royce and others were free to develop their engines as THEY were the owners of the design. The Merlin was privately developed during the Schneider cup races. You know the first Merlin (PV-12) used technology directly from the Rolls Royce Type R engine. The Griffon of 1933 even used the same bore and stroke as the Type R. It was not directly -related to the later Griffons.

4) I never mentioned the Merlin when I said the latest Allison that was flying regularly could make 2,300 hp. You did. Why quote me? Make your own post about the Merlin. It was and IS a good engine and I didn't say different in my post.

5) I didn't say Merlins were hand-crafted with files in the post above. I also never said Merlins were badly built. They weren't.

6) You say the XP-39 was a turd. Many in here have said that. But I have yet to see ONE shred of proof from a flight test that backs it up. What I AM sure of is that if the turbocharger had been retained, the altitude performance of the P-39 would have materially improved. I can't say if it would ever have been a good system since it wasn't developed further than the one installation. Nobody can reliably say how fast it went since the data apparently does not exist or has yet to be uncovered and published.

7) The turbocharger was GFE supplied from GE. If GE didn't fix it, it didn't get fixed. Like the other manufacturers, Allison was not allowed to modify GFE. They bolted it into the airplane and used it. Same with guns and other GFE. When I was in the weapons industry (1980s and 1990s), it was the same then. If you got something from the government, you used it as supplied. If you had GFE issues, you tried to work them out in meetings with the customer and the GFE supplier ... you didn't throw money at a "fix" for which you might or might not get compensated, even IF it got accepted for production. Generally, the users (USAAC pilots and squadrons) would filter back their complaints and the manufacturers would try to work things out as best they could while still turning out products for the war effort.

Not sure what your problem with me is, but it is obvious you don't want to hear anything good about an Allison engine. Too bad, They ARE good engines and run just fine.

Here is Bob Deford's experience with it. He built a Marcel Jurca kit (steel tube fuselage and wood wings). It flies very nicely. He flies over and visits Chino occasionally from Arizona.

 

[Shortround6]

The cost fell with the increase in production. Not really related to any engineering improvements.

To be fair that is not what Greg said.
"Improvements in manufacturing brought the cost down"
while a lot of the cost reduction was simply due to mass production some of it was "improvements in manufacturing" which lowered the scrap rates of certain operations, like casting the crankcase and cylinder blocks. Some of it was due to the use of specialized machines which were too large and costly for use for small batches but did reduce costs on large runs. Just lining up more old, small machines with more workers doesn't get you the full benefit of mass production.

The XP-39 with turbocharger was a turd. It never had the performance promised, and likely not even the performance of the modified XP-39 without turbo.

Not much argument there. The Performance of the XP-39 was not only well below what what was promised before flight, it was well below what was claimed after flight if in fact such flights at anywhere near the claimed performance ever took place. XP-39 may have been one of the great con jobs of aircraft marketing at the beginning of the war.

The problem wasn't really the regulation of turbocharger temperature, but rather regulation of the turbocharger speed, which was controlled using the wastegate

I am not sure who supplied the turbo charger regulator. It may have been a 3rd party. neither GE or Allison or even the airframe maker. The early one sensed the pressure in the exhaust system and sought to maintain a preset value which in turn was thought to control the inlet pressure (kind of an obvious disconnect here) but it tended to freeze or accumulate ice in the sensor tube and so could stick at any position. Too closed could lead to overspeeding while too open meant the engine never developed rated power at altitude. Not as catastrophic but hardly ideal. This plagued a number of turbo installations, not just the Allison ones. A later regulator sensed the pressure in the intake duct and controlled the waste gate to maintain that preset value.
Preset in the sense that the engine controls interconnected with the regulator so a certain pressure was supposed to be present at the carburetor intake for a given throttle setting/flight condition without the pilot having to perform any mental gymnastics trying to figure out pressures before carb vs pressure in manifold after carb and engine supercharger.

 

[wuzak]

6) You say the XP-39 was a turd. Many in here have said that. But I have yet to see ONE shred of proof from a flight test that backs it up. What I AM sure of is that if the turbocharger had been retained, the altitude performance of the P-39 would have materially improved. I can't say if it would ever have been a good system since it wasn't developed further than the one installation. Nobody can reliably say how fast it went since the data apparently does not exist or has yet to be uncovered and published.

The fact that the XP-39 was whisked off to the NACA wind tunnel for analysis after its first or second flight may be a clue.

Whilst there may not be any shred of evidence from flight test data that the XP-39 was a turd, there is also no flight test data proving the XP-39 wasn't.

The fact that there is no flight test data may be because it probably didn't have any quantitative data taken before it went to NACA to be fixed.

 

[wuzak]

3) The US government owned the Allison type certificate. It was also the ONLY V-12 that passed the 150-hour type test during the war. Rolls Royce and others were free to develop their engines as THEY were the owners of the design. The Merlin was privately developed during the Schneider cup races. You know the first Merlin (PV-12) used technology directly from the Rolls Royce Type R engine. The Griffon of 1933 even used the same bore and stroke as the Type R. It was not directly -related to the later Griffons.

I don't know what type tests in the US the Merlin passed. I suspect the Merlin did not have to complete that test because it was a Rolls-Royce design that passed UK type tests.

Even later model V-1650s were built to Rolls-Royce specs and ratings.

The Merlin design started 2 years after the Schneider Trophy was won by the R.

It shared little with the R, if anything.

The 1931 R had a master and slave rod arrangement. The PV12/Merlin had a fork and blade.
The 1931 R had a Kestrel style cylinder head in unit with the block (as the R was based on the Buzzard, which was a 6/5 scale of the Kestrel). The PV12/Merlin started with the blocks and crankcases cast together and a separate cylinder head.
The 1931 R had a flat combustion chamber. The PV12 had the "ramp head".

No doubt that the PV12/Merlin design was informed by the R, but it differed in many key details.

The Griffon I of 1933 was a detuned R.

 

[wuzak]

4) I never mentioned the Merlin when I said the latest Allison that was flying regularly could make 2,300 hp. You did. Why quote me? Make your own post about the Merlin. It was and IS a good engine and I didn't say different in my post.

You made the claim that the V-1710 made more power with lower boost. I posted an example that showed that was not always the case.