V-1650 powered P-40's

[gjs238]

If I understand correctly...
- The P-40F's and L's received the Packard Merlin 28 (Mark XX) [V-1650-1] (single stage, two speed supercharger)
- The P-51 received the V-1650-3 (two speed, two stage supercharger)

Questions:
1) Why use the V-1650-1 in the P-40? What was the expected benefit over the V-1710?
2) Why not use the V-1650-3 in the P-40? With all the altitude criticism the P-40 received, why not give it the V-1650-3?

 

[tomo pauk]

1) It was expected that Packard Merlin will give the performance boost, particularly at higher altitudes.
2) P-51 was a vastly better airframe, so it got any two-stage V-1650s Packard could produce for USAAC. And there was a delay to get those engines in the 1st place; US production of two-stage Merlins was lagging behind British by a full year, IIRC.

 

[wuzak]

1) The benefit was that the Merlin had been approved for higher power (IIRC the V-1710 didn't at that stage have War Emergency Ratings) and, as Tomo notes, had better altitude performance.

2) When they put the single stage V-1650-1 in the P-40 the two stage hadn't yet entered production. By then the P-40 airframe was mostly considered obsolete (though it remained in production).

 

[Shortround6]

1.) there was a definite performance boost (or maybe performance relocation would be a better term) with the V-1650. While the V-1650 powered planes were barely faster than the V-1710 powered planes (F vs E) the F hit it's top speed at 20,000ft and not 15,000ft. At 22-23,000ft the F was around 30mph faster. At 15,000ft and below it was a bit slower than the E.

2.) by the end of 1942 Packard had delivered 7,296 single stage Merlins and 5, yes 5, two stage engines. By the time, end of July 1943, Packard had delivered another 260 two stage engines they had delivered 8300 more single stage engines. Granted roughly 2/3 of these engines ere going to the British but by the time the V-1650-3 shows up in any numbers the P-40 is out of the running as a first line fighter

 

[Ratsel]

Reading some paragraphs from Jay Overcash while he was flying with the 64th fs / 57th fg in Tunisia, he remarked that the V-1650-1 was troublesome at all altitudes wasn't as powerful, reliable, or fast as the Allison V-1710. He seemed to really like his P-40K-1 Ser.No. 42-46046 with its Allison V-1710-73.

 

[vanir]

There's a record of some DAF P-40K being overboosted up to 66"Hg WER (around 1600hp).
I also read that RR found Packard was building Merlins better than they were, when an executive toured the Packard factory he took new metallurgies for making bearings that RR incorporated into their own production. He also commented that "Packard has made many minor improvements to the Merlin engine in production."

Shortround6 I think, if I remember it correctly, once explained how the Allison blower mounting and manifolding is better than the Merlin style.

Essentially the way I've read it is the Allison got handicapped by Army imposition to make a low altitude Pursuit plane with a small, reliable single stage blower. The Merlin XX had two gears. The best idea would've been put a different blower on the Allison, but Army wanted what it wanted.

Also it wasn't really until 1941 AFAIK that Army was about to reconsider the altitude range of fighter engagements, nobody talked about improving the altitude performance of the P-40 until the F and L were produced, the K of course was surplus F and L airframes with no Merlins to put in them from what I gathered. Then as Shortround6 says by that time they were out of the running as the main front line fighter type, things were shaping up to be the new P-47.

 

[Shortround6]

I think people get confused as to what was low altitude and high altitude in the late 30s. in 1939 ANYTHING and EVERYTHING that did not have a turbo charger was "low altitude". There were NO workable 2 stage mechanical blowers in any country and the 2 speed single stage super charger was only 6-7 years old and the ONLY production engines with 2 speed superchargers were the British Armstrong Siddeley Tiger, Bristol Pegasus and Merlin X, The American Wright Cyclone (since 1937) and the P &W Twin Wasp (after the Cyclone), and the German inverted V-12s.
Given the state of the art in supercharger design (the actual impellers and housings) nobody was really ahead of anybody else at this point. Critical altitudes (full throttle heights) even for the 2 speed superchargers didn't go over 17,000ft and many of them were down around 12-14,000ft in high gear. In many cases the 2 speed supercharger was used to boost take-off power and climb out as much or more than it was used to improve altitude performance.

A good supercharger in the late 30s was capable of delivering a pressure ratio of about 2.3 to one installed in the aircraft. Really good ones were touching a pressure ratio of 2.8 to one. If your engine needed 44in of manifold pressure to make rated power then the critical altitude was going to be about 12,000ft with a 2.3:1 supercharger. Spinning it faster wasn't going to help, the design was maxed out. Spinning it slower would take less power to drive at lower altitudes, it would heat the intake air less and it would allow the throttle plate to open wider meaning less intake loss. A big boost in power at "LOW" altitude like the 3-7,000ft heights that ALL the production 2 speed engines used as their "LOW" altitude critical height.
A 2.8:1 supercharger could get the 44in MAP engine to about 17,000ft, however a 2.3:1 supercharger engine that needed only 39in of MAP could have a critical height of 15,000ft.
The supercharger on a Merlin III had a Pressure ratio of about 2.6:1.
Considering that the P-40 was "designed" (adapted from the P-36) in 1938 and production orders first place in the Spring of 1939 with the object of getting USABLE fighters into service as soon as possible with the least amount of development work needed there really wasn't much other choice. The Army was very interested in high altitude operations, they just were not possible given the currant technological state of the art.

As has been said before, Allison was a small company in 1937-38 with fewer than 25 employees in the engineering section. They also had no real production facility. In 1939-40-41 they knew that a better supercharger was needed ( work did start in 1938 on a two stage) but the rapid expansion and getting the basic engine into production sucked up a lot of time and effort. The Army was probably more at fault for wanting a variety of different engines than for not wanting a better supercharger. With the P-39 extension shaft engine, the Aircuda extension shaft pusher engine, the handed engines for the P-38 (and Aircuda?) and the V-3420 24cylinder engine the Allison staff may have been stretched way too thin to put proper effort in a better supercharger. With General electric supply the supercharger design and parts to ALL American engine makers until about 1937 there wasn't much of a pool of supercharger designers to draw from either.

Design got a lot better in 1941-42-43 but in many countries production of existing designs often trumped improved models.

 

[MikeGazdik]

Shortround, what an educational post!! Thanks.

 

[gjs238]

I was under the impression that the V-1710 was rather competitive with the Packard Merlin 28 (Mark XX) [V-1650-1] (single stage, two speed supercharger) used in the P-40F's and L's.

Now I'm wondering if the Packard Merlin 28 (Mark XX) [V-1650-1] (single stage, two speed supercharger) could have/should have been employed in P-51's.

 

[wuzak]

I was under the impression that the V-1710 was rather competitive with the Packard Merlin 28 (Mark XX) [V-1650-1] (single stage, two speed supercharger) used in the P-40F's and L's.

Now I'm wondering if the Packard Merlin 28 (Mark XX) [V-1650-1] (single stage, two speed supercharger) could have/should have been employed in P-51's.

I believe Shortround has shown that the V-1710 held its own at certain altitudes against the V-1650-1, but not at the higher altitudes.

Even so, the two stage V-1650-3 was much better at altitude than the -1 and the V-1710.

 

[Ratsel]

Shortround, what an educational post!! Thanks.

I agree!

 

[gjs238]

Well, yes.
My point was that it took some time for the V-1650-3 to appear in the P-51.
Meanwhile, perhaps, the V-1650-1 could have been employed in lieu of the V-1710.

Another question:
Were V-1710's powering P-51's while V-1650-1's were powering P-40's?

 

[Shortround6]

First, thank you for the compliments.

Second, the Merlin XX was the first Merlin to use the Hooker modified supercharger, because of the improved inlet it was able to achieve a better pressure ratio than the previous Merlin supercharger, but it doesn't show up until the summer of 1940. It is at this point that Allison starts to fall behind Merlin in supercharger performance, This supercharger is able to deliver 9lbs boost (about 48in MAP) at 18,500ft or a pressure ratio of about 3.28. The first five V-1710F3R (-39) engines that wound up powering the P-40 E were ordered in Jan of 1940 for development and provision to the XP-46 and XP-47 programs. The supercharger was slightly improved from the the one on the V-1710C15 (-33) engine used in the P-40s through the "C" model. By the time the later engines with the 9.60 gears show up a few minor tweaks have improved things to the point that the Allison supercharger is providing a pressure ratio of about 2.7:1. The supercharger on the German DB605A was good for a pressure ratio of about 3.0:1, earlier DB601 engines didn't seem to reach that pressure ratio (except for the 601E?)

A Merlin 61 has a pressure ratio of 5.0:1 in high gear. Without pressure ratios in the over 4 range nobody was going to get really good engine performance (not aircraft performance) in the 25,000-30,000ft range. P-47C hada pressure ratio of about 5:1 and a P-38L could manage 6:1.

High altitude "aircraft performance" could be had by using a light airplane with a not so hot engine. Heavy planes were doomed without a well performing altitude engine.

 

[Shortround6]

Well, yes.
My point was that it took some time for the V-1650-3 to appear in the P-51.
Meanwhile, perhaps, the V-1650-1 could have been employed in lieu of the V-1710.

Another question:
Were V-1710's powering P-51's while V-1650-1's were powering P-40's?

The answer to the last question is yes. But a problem is production scheduling and not just what would make the "best" fighter but what would give the "MOST" good fighters. Just like the Hurricane got the Merlin XX (V-1650-1) and the Spitfire didn't. The Spitfire could be competitive with a single speed engine. The Hurricane would have been even further behind with the Merlin 45, less power for take-off and at low altitude.
Most Merlin powered P-40s went to the MTO. With a 20-30mph speed advantage over an Allison powered P-40 at 20-25,000ft it was thought they would have a better chance against the Me 109. The difference at low altitude wasn't anywhere near as great. But production allocations had to be made and Fighter groups equipped months before combat was actually joined in North Africa. If the Merlins are given to the P-51s you have ONLY the poorer performing Allison powered P-40s and you may have disrupted P-51 production by several months. While much easier to fit in that the two stage Merlin the single stage Merlin is a bit heavier than the Allison and more importantly it gets rid of a different amount (percentage) of heat to the oil and coolant than an Allison which means you may not be able to use the same radiators and oil coolers. SO you still have to test fly the installation and then order the appropriate radiators/oil coolers ( for delivery weeks or months down the road). Not impossible or even terribly hard but one more detail. The Allison P-51 could hit 415mph at 10,400ft using WER and could hit a claimed 395mph at 25,000ft with Military power. It was competitive without the Merlin in 1942, early 1943. A V-1650-1 poweerd version may have been faster adn climbed better but you may have had fewer TOTAL number of effective fighters.

 

[vanir]

Yeah the DB-601E has a real strong 1.42ata all the way to throttle altitude, about 5800m I think, 605A bumps it to around 6200m. But you can safely overboost the 601E to about 1.5ata at about 2000m in a nice ram dip, it returns its best power at this height. All on B4 too, IG Farben spent a lot of research on combustion chambers trying to replicate it in the DB-605.
Every pilot I ever heard loved the Me-109F best of the series, if you ask me it was that beautiful 601E so well matched to the airframe, not underdeveloped, not overkill. If it wasn't wartime, it probably would've been the standard in European fighter aircraft for a decade.

 

[tomo pauk]

The answer to the last question is yes. But a problem is production scheduling and not just what would make the "best" fighter but what would give the "MOST" good fighters. Just like the Hurricane got the Merlin XX (V-1650-1) and the Spitfire didn't. The Spitfire could be competitive with a single speed engine. The Hurricane would have been even further behind with the Merlin 45, less power for take-off and at low altitude.
Most Merlin powered P-40s went to the MTO. With a 20-30mph speed advantage over an Allison powered P-40 at 20-25,000ft it was thought they would have a better chance against the Me 109. The difference at low altitude wasn't anywhere near as great. But production allocations had to be made and Fighter groups equipped months before combat was actually joined in North Africa. If the Merlins are given to the P-51s you have ONLY the poorer performing Allison powered P-40s and you may have disrupted P-51 production by several months. While much easier to fit in that the two stage Merlin the single stage Merlin is a bit heavier than the Allison and more importantly it gets rid of a different amount (percentage) of heat to the oil and coolant than an Allison which means you may not be able to use the same radiators and oil coolers. SO you still have to test fly the installation and then order the appropriate radiators/oil coolers ( for delivery weeks or months down the road). Not impossible or even terribly hard but one more detail. The Allison P-51 could hit 415mph at 10,400ft using WER and could hit a claimed 395mph at 25,000ft with Military power. It was competitive without the Merlin in 1942, early 1943. A V-1650-1 poweerd version may have been faster adn climbed better but you may have had fewer TOTAL number of effective fighters.

That would be the P-51A/Mustang II - so it's really from June 1943 in combat service (1st produced in March 1942)? The 1st P-40s with Packard Merlin were produced in January 1942 - 14 months before P-51A. While it would've taken time (and caused less fighters produced) to develop a V-1610-1 P-51, the same was true for the P-40 with Merlin.

Too bad for Allied cause that Brits didn't borrowed a Merlin XX to the NAA back in late 1940/early 1941.

 

[Edgar Brooks]

Too bad for Allied cause that Brits didn't loan a Merlin XX to the NAA back in late 1940/early 1941.

With the U.S. at peace, they, almost certainly, wouldn't have been allowed to. Even when work (and the war) was going on, to marry the Merlin to the Mustangs, one U.S. general said that the politicians seemed to be more interested in having an all-American airframe, than in defeating the Germans, so it wasn't all plain sailing.

 

[gjs238]

That would be the P-51A/Mustang II - so it's really from June 1943 in combat service (1st produced in March 1942)? The 1st P-40s with Packard Merlin were produced in January 1942 - 14 months before P-51A. While it would've taken time (and caused less fighters produced) to develop a V-1610-1 P-51, the same was true for the P-40 with Merlin.

Too bad for Allied cause that Brits didn't borrowed a Merlin XX to the NAA back in late 1940/early 1941.

When the Brits ordered the P-51 (and for that matter approached NAA for license-built P-40's) they knew they would be getting V-1710 performance.
So it seems reasonable that the planes could have been ordered, or supplied at some point, with V-1650's.

 

[tomo pauk]

With the U.S. at peace, they, almost certainly, wouldn't have been allowed to.

The Brits have supplied Merlin 28 (RR built, that is) to Curtiss, in order to expedite the P-40F development - the plane flew on June 30th 1941 (airframe AC40-360). So, that was allowed.

Even when work (and the war) was going on, to marry the Merlin to the Mustangs, one U.S. general said that the politicians seemed to be more interested in having an all-American airframe, than in defeating the Germans, so it wasn't all plain sailing.

Many people on high places were doing sterling job, but they made mistakes, too. Allied brass could got away with that (after 1942), Axis brass could not.

When the Brits ordered the P-51 (and for that matter approached NAA for license-built P-40's) they knew they would be getting V-1710 performance.
So it seems reasonable that the planes could have been ordered, or supplied at some point, with V-1650's.

A plane with a V-1710 was as good performer in 1940 as that was same plane with Merlin, but in 1941 and later that was not the case. Maybe Brits were expecting that Allison is going to 'grow' with same pace as Merlin did, yet it did not. We can recal that Rolls-Royce/Merlin was receiving a major Governmental support in late 1930s (UK was gearing for a major war, so that's no wonder) - not the case for Allison/V-1710, and that shows.
The Packard deal for Merlins specified/ordered 3000 V-1650s for USAAC, more than USAAC ordered V-1710s by that time, by the way.

 

[Shortround6]

Ah, guys, Packard delivered about 45 Merlins in ALL of 1941. While there may have been a few available for flight testing in a few air frames with 2/3 of production going to the British there would have been darn few American P-51s with Merlins before 1942. There were also only 138 P-51s accepted in 1941 compared to 2,246 P-40s and in 1942 the numbers went 634 P-51s to 3,854 P-40s. A big jumps in Mustang production came with the opening of the Dallas Factory and moving a lot of B-25 production to Kansas City.

A Merlin V-1650-1 wold have been better than an Allison powered one overall ( but not by much at certain altitudes depending which Allison) but it would not have been available in any numbers in 1942 or early 1943 and would only have been available at the cost of the P-40F which at the time was the second best Army altitude fighter available in any quantity next to the P-38. In 1942 early 1943 there were nowhere near enough P-38s to go around. Over 3600 P-40F-s were built along with 700 'L's. Granted near the end the V-1650-1 was competing for production with the V-1650-3 but allocation for raw materials and finished sub-contractor parts have to be months and months before a US plane ever saw combat.