P-40 vs. Yak-1 vs. Hurricane

[Shortround6]

The Merlin III of 1940 had 1320 hp with 12 lbs boost, by 1941 16 lbs boost and 1440 hp. Max speed of Tomahawk would have been at same altitude as Spitfire and Hurricane. So its heavier, it can dive faster and has a longer range, so not as good as an interceptor, but much better when used in the 1941 France Air Offensive. More suited.

Before you hit the X button you might want to do a little more research. The 1320hp was at 9000ft, power at 16,500 and above was unchanged.
the 1440hp was at 5500ft, power at 9000ft and at 16,500ft was unchanged. The 1440hp rating was only approved for Sea Hurricanes, in part the CAM ones that were expected to ditch at the end of the flight so engine life was not very important.

Now please note that while not officially sanctioned, the early Allison was frequently over boosted in squadron service in NA so it was making at least a few hundred more HP than the official figures at low altitude.

as to the range, a P-40B held about 160 US gallons inside (about 133 Imp gallons) and had no drop tank. A P-40C with better self sealing tanks held 137 US gallons (114 Imp gal) inside. Better range than a Spitfire but not really enough to get very far past the coast.

 

[Shortround6]

Merlin III was single speed.

Merlin XX was 2 speed.

The P-40B didn't get into production until 1941.

Probably looking at Merlin XXs or a Merlin 45. At least for the first 6 months the engine supply would had to have been British, as Packard came up to speed.

Packard built 45 engines in 1941, 26 of them in Dec. ALL fighter production in 1941 would have had to come from British sources (Packard built 5 engines in October).

 

[Shortround6]

I would note that not only was the Merlin XX a two speed engine (which helped low altitude more than high ) , it got the better Hooker modified supercharger (which is what really improved high altitude performance) and it got some beefed up parts to stand up to the higher output better.

 

[Kevin J]

Merlin III was single speed.

Merlin XX was 2 speed.

The P-40B didn't get into production until 1941.

Probably looking at Merlin XXs or a Merlin 45. At least for the first 6 months the engine supply would had to have been British, as Packard came up to speed.

I don't think there were many Merlin 45's available until the Summer of 41. Its either the Merlin III, the XII or a few Merlin XX's.

 

[Schweik]

Before you hit the X button you might want to do a little more research. The 1320hp was at 9000ft, power at 16,500 and above was unchanged.
the 1440hp was at 5500ft, power at 9000ft and at 16,500ft was unchanged. The 1440hp rating was only approved for Sea Hurricanes, in part the CAM ones that were expected to ditch at the end of the flight so engine life was not very important.

Now please note that while not officially sanctioned, the early Allison was frequently over boosted in squadron service in NA so it was making at least a few hundred more HP than the official figures at low altitude.

Extra power at medium and low altitudes was not a trivial thing. Combat often descended to lower altitude in the course of a fight, and in the Med it was common practice both for Hurricane and (especially) Tomahwak / Kittyhawk pilots to flee to lower altitude where they had better performance, especially when overboosting had become more common (officially sanctioned and otherwise). Standard escape maneuver for a P-40 was a Split-S and dive down to a 'healthier' altitude where they could turn the tables. This was something Neville Duke did several times for example, as well as American aces like Levi Chase and Bill Momyer.

Having 1440 hp at 5500 feet would mean probably a 20 mph speed boost and ~ 3500' fpm (initial) rate of climb, as well as a better turn rate and of course, faster dive speed. All quite useful in combat. Enough to put them on parity with Bf 109 E through F-2 at that altitude.

 

[Shortround6]

Extra power at medium and low altitudes was not a trivial thing. Combat often descended to lower altitude in the course of a fight, and in the Med it was common practice both for Hurricane and (especially) Tomahwak / Kittyhawk pilots to flee to lower altitude where they had better performance, especially when overboosting had become more common (officially sanctioned and otherwise). Standard escape maneuver for a P-40 was a Split-S and dive down to a 'healthier' altitude where they could turn the tables. This was something Neville Duke did several times for example, as well as American aces like Levi Chase and Bill Momyer.

Having 1440 hp at 5500 feet would mean probably a 20 mph speed boost and ~ 3500' fpm (initial) rate of climb, as well as a better turn rate and of course, faster dive speed. All quite useful in combat. Enough to put them on parity with Bf 109 E through F-2 at that altitude.

ANd pretty much useless if trying to escort the British bombers of 1941 as proposed in Post #293. The Wellingtons and Hampdens and whatever else the British could scrape up for a daylight escorted bombing offensive are NOT going to be cruising around at 5000-9000ft where their 'escorts' engine work best but they are fat ripe targets for AA guns.
Split-S to a lower altitude for the escorts just leaves the bombers open to attack by the German interceptors.

The higher power limits can be quite useful in some situations, just not this one.

The practical difference between an early Spitfire and a early P-40 was not the difference Between and Allison C-15 and a Merlin III but the fact that the P-40 weighed 1000-1200lb more than the Spitfire. A Bf 109F-1/2 went about 6000lbs in interceptor mode (no bombs or drop tank) and that was part if it's success at altitude, the supercharger wasn't all that great, the engine just wasn't trying haul around anywhere near as much wight.

Edit, there seems to be a problem with numbering of the posts.

I was replying to this
"but instead of Tomahawks being only suitable for army co-operation in Europe, we would have had a fighter with a better range better suited to escorting our bombers on daylight attacks"

 

[Schweik]

ANd pretty much useless if trying to escort the British bombers of 1941 as proposed in Post #293. The Wellingtons and Hampdens and whatever else the British could scrape up for a daylight escorted bombing offensive are NOT going to be cruising around at 5000-9000ft where their 'escorts' engine work best but they are fat ripe targets for AA guns.
Split-S to a lower altitude for the escorts just leaves the bombers open to attack by the German interceptors.

The higher power limits can be quite useful in some situations, just not this one.

I don't agree - if you look at the actual battlefield record, it was fairly normal for P-40s to escort bombers or fighter bombers at regular medium bombers cruising altitudes 10, 15, 20k feet whatever (also keep in mind medium bombers often flew at 'medium' altitude since many medium bomber types didn't always perform that well very high), whether or not the fighters were over their own performance ceiling (which ranged from 12-16k for earlier model Allison engined P-40s, 20k for Merlin) and do their best at that altitude, but dive down below if they got in trouble with intercepting fighters. This was true both in the Med and in the Pacific.

This reality actually contributed to the official divergence between "close escort" and "free range escort" type policies later in the war, on both sides.

Though in theory this would leave the bombers alone and vulnerable in practice it seemed that the attacking and escorting fighters would often get into mixed up affrays while the bombers went on their way (sometimes fleeing at high speed and a shallow dive). It didn't take the bombers very long to get out of sight nor did it take Bf 109s very long in combat to run low on fuel and not be able to chase them. Zeroes of course (and to a lesser extent, Ki 43s) had much more endurance but they had less of a speed margin to chase fleeing bombers. An A-20 running flat out wasn't much slower than a Zero.

Mission profiles and performance envelopes often do not hinge on sticking to the optimal conditions of a planned mission but also quite often devolve to how could they handle worse case scenarios, which in combat with as formidable an enemy as the Luftwaffe or IJN were all too routine an occurrance. An escort fighter that could survive missions at a high rate was an escort fighter that could continue to be used.

Vulnerability is of course an issue. You did need fast enough bombers. One could in fact imagine a scenario with merlin engined P-40s escorting Allison Engined P-51 dive bombers.

The practical difference between an early Spitfire and a early P-40 was not the difference Between and Allison C-15 and a Merlin III but the fact that the P-40 weighed 1000-1200lb more than the Spitfire. A Bf 109F-1/2 went about 6000lbs in interceptor mode (no bombs or drop tank) and that was part if it's success at altitude, the supercharger wasn't all that great, the engine just wasn't trying haul around anywhere near as much wight.

It was a little bit of both, actually. The Merlin XX certainly did improve the higher altitude performance of the P-40F/L, just as the steadily improving high altitude performance of both Merlin and DB engines helped Spitfires and Bf 109s perform higher and higher.

By contrast, the early Zero which was quite light of course actually had relatively poor altitude performance, A6M2 wasn't so great about 18k from what I have read.

S

 

[Schweik]

come to think of it, I'm sure a P-51A would have benefited from a Merlin III or XX, if not to the miraculous extent as with the Merlin 60

 

[tomo pauk]

come to think of it, I'm sure a P-51A would have benefited from a Merlin III or XX, if not to the miraculous extent as with the Merlin 60

From Merlin III - no, the V-1710-81 was in no way a worse engine. Granted, it became available several years after Merlin III was 3rd or 4th best Merlin.
On the other hand, Merlin XX, 45 or 46 would've improved performance of the P-51A, let alone of the P-51 (here is the Merlin III an improvement).

 

[Shortround6]

I don't agree - if you look at the actual battlefield record, it was fairly normal for P-40s to escort bombers or fighter bombers at regular medium bombers cruising altitudes 10, 15, 20k feet whatever (also keep in mind medium bombers often flew at 'medium' altitude since many medium bomber types didn't always perform that well very high), whether or not the fighters were over their own performance ceiling (which ranged from 12-16k for earlier model Allison engined P-40s, 20k for Merlin) and do their best at that altitude, but dive down below if they got in trouble with intercepting fighters. This was true both in the Med and in the Pacific.

This reality actually contributed to the official divergence between "close escort" and "free range escort" type policies later in the war, on both sides..........

This rather disregards an essential difference between Europe and the Med and Pacific.
Yes the British bombers of 1941 aren't going to fly as high as the turbocharged B-17s and B-24s but there was a much higher density of AA guns in Europe than in North Africa/Med and the Pacific.
Pretty much the only AA guns you had to worry about were the ones at/near the target (and Japanese light AA was crap) as opposed to Europe where, if you actually planned to go very far past the coast there were a number of defended areas you had to pass by or detour around.

Think of AA coverage like a dome over each gun/battery. The higher you fly the less time you spend in the "dome" or the further you fly from the center.

A "good" height (medium?) was out of the effective range of 37-40mm guns (not their max range/ceiling) but low enough to cause problems with traversing the big guns or with the fuse setters. There is sort of a minimum effective distance although not talked about much.

While the Germans had nowhere near enough AA guns to cover all of France and the low countries they certainly had a higher number of guns per large area of ground than they had in the desert and floating in the Mediterranean sea.

We are also talking about 1941 and not 1942 and the British have nowhere near the number of "fast bombers" they would have in 1942.

 

[Kevin J]

Extra power at medium and low altitudes was not a trivial thing. Combat often descended to lower altitude in the course of a fight, and in the Med it was common practice both for Hurricane and (especially) Tomahwak / Kittyhawk pilots to flee to lower altitude where they had better performance, especially when overboosting had become more common (officially sanctioned and otherwise). Standard escape maneuver for a P-40 was a Split-S and dive down to a 'healthier' altitude where they could turn the tables. This was something Neville Duke did several times for example, as well as American aces like Levi Chase and Bill Momyer.

Having 1440 hp at 5500 feet would mean probably a 20 mph speed boost and ~ 3500' fpm (initial) rate of climb, as well as a better turn rate and of course, faster dive speed. All quite useful in combat. Enough to put them on parity with Bf 109 E through F-2 at that altitude.

All Hurricanes had 16 lbs boost from 1942.

 

[Shortround6]

All Hurricanes had 16 lbs boost from 1942.

Hurricane Is with Merlin IIIs or Hurricane IIs with Merlin XX engines (or later)?

For a while Hurricanes IIs were allowed to use 14lbs of boost in low(or medium) supercharger and 16lbs in high gear with their Merlin XX engines.

Hurricane IVs with Merlin 24 or 27 engines were allowed to use 18lbs but they had stronger supercharger drives/clutches than the Merlin XX engines.

 

[Kevin J]

Extra power at medium and low altitudes was not a trivial thing. Combat often descended to lower altitude in the course of a fight, and in the Med it was common practice both for Hurricane and (especially) Tomahwak / Kittyhawk pilots to flee to lower altitude where they had better performance, especially when overboosting had become more common (officially sanctioned and otherwise). Standard escape maneuver for a P-40 was a Split-S and dive down to a 'healthier' altitude where they could turn the tables. This was something Neville Duke did several times for example, as well as American aces like Levi Chase and Bill Momyer.

Having 1440 hp at 5500 feet would mean probably a 20 mph speed boost and ~ 3500' fpm (initial) rate of climb, as well as a better turn rate and of course, faster dive speed. All quite useful in combat. Enough to put them on parity with Bf 109 E through F-2 at that altitude.

Having 1440 hp at 5500 feet means that you can make your top speed at altitude your top speed at the lower height.

 

[Greg Boeser]

They would have made more Merlin engined Warhawks if the engines had been available.

Once the decision was made to put Merlins in P-51s, Merlin engine P-40s were stripped and converted back to Allisons (P-40R).

 

[wuzak]

I don't think there were many Merlin 45's available until the Summer of 41. Its either the Merlin III, the XII or a few Merlin XX's.

There would not have been many available to aircraft other than the Spitfire.

The Spitfire V was entering operational service by early 1941.

Hurricane Mk IIs with Merlin XXs were being built since ~June of 1940 and went into squadron service in September 1940.

 

[Shortround6]

Once the decision was made to put Merlins in P-51s, Merlin engine P-40s were stripped and converted back to Allisons (P-40R).

Actually has nothing to do with each other. The engines in the P-40s used single stage superchargers and the P-51 used two stage superchargers.

The Army goofed when it allocated or requested Merlin engines for the P-40 Production. They only requested about 20% extra engines for spares (30-50% was more normal) and then (later) decided to send the planes to North Africa where the sand considerably shortened the engine life. Faced with useable airframes in a war zone but without useable engines they followed two paths. 1. The British supplied tons of parts to assist in overhauling the engines in theater, breaking down hundreds of their own used engines. 2. The US either re-equipped some planes in the Field with Allison's (doubtful as they need different radiators and oil coolers unless they got them from junked P-40Es or Ks) or they took RR engines from stateside planes and shipped the engines to North Africa as replacements and requiped the the engineless planes in the US with the Allison installation.
This episode also points out the fallacy that British and American Merlins didn't use interchangeable parts.
Some parts were not interchange (supercharger drive and some things like carbs or starter motors) but the guts were fully interchangeable.

 

[Schweik]

Once the decision was made to put Merlins in P-51s, Merlin engine P-40s were stripped and converted back to Allisons (P-40R).

I'm not sure that is precisely how that happened, as so far as I know it was a different Merlin that went into the P-40F and L - the Merlin 28 aka Packard V-1650-1, a license built Rolls Royce Merlin XX. The one in the Mustang was a 60 series, (Merlin 68 and 69 / aka Packard V-1650-3 and V-1650-7) license built RR Merlin 63 and 63A much more sophisticated - two stage blower.

List of Rolls-Royce Merlin variants - Wikipedia

I'm sure Shortround can tell us more.

Merlin XX was the first two speed Merlin, while Merlin 60 series were the first two stage Merlin, a far more impressive, sophisticated and useful innovation. Rather amazingly, it was developed for some kind of high altitude Wellington bomber.

Wiki says Merlin XX was being built from 1940 by the way. +14 boost or +16 with 100 Octane fuel

P-40R did have Allisons instead of Merlins but I suspect that was due to their not having enough Merlins either due to the original engines being burned out / needing replacement or because they just didn't have any available to put in them. It's not entirely clear.

I think Packard was being switched over to full scale production of the Merlin 63 (Packard Merlin 68 / V-1650-3)

Other fun fact about the V-1650-1 was that it was made a bit more robust than the original (tougher bearings) and therefore probably capable of higher boost.

S

 

[Schweik]

Actually has nothing to do with each other. The engines in the P-40s used single stage superchargers and the P-51 used two stage superchargers.

The Army goofed when it allocated or requested Merlin engines for the P-40 Production. They only requested about 20% extra engines for spares (30-50% was more normal) and then (later) decided to send the planes to North Africa where the sand considerably shortened the engine life. Faced with useable airframes in a war zone but without useable engines they followed two paths. 1. The British supplied tons of parts to assist in overhauling the engines in theater, breaking down hundreds of their own used engines. 2. The US either re-equipped some planes in the Field with Allison's (doubtful as they need different radiators and oil coolers unless they got them from junked P-40Es or Ks) or they took RR engines from stateside planes and shipped the engines to North Africa as replacements and requiped the the engineless planes in the US with the Allison installation.
This episode also points out the fallacy that British and American Merlins didn't use interchangeable parts.
Some parts were not interchange (supercharger drive and some things like carbs or starter motors) but the guts were fully interchangeable.

Beat me to it.

I know that they ran short enough on P-40 F and L models that the 64th squadron of the 57th FG had to be equipped with P-40K's for a while.

The two DAF squadrons with Merlin P-40s (Kittyhawk II and IIA), the 260 RAF and the 3 RAAF, both ran out of them in Italy before they wanted to and had to switch over to far less capable P-40Ms. One of them (260 RAF) switched back to Kittyhawk II's for a while (probably due to some kind of scramble for parts such as you described above) and still had a few left before switching to Mustang III's in April 1944.

P-40Ms were fine for fighter bomber duties but when they were going up against the Luftwaffe they really preferred the Mk II.

Apparently P-40Ks were pretty sought after in the RAF as well, Bobby Gibbes (10 Kill Australian Ace) mentions "stealing" one from the RAF for a while, during which time he pulled away from his squadron and shot down a Bf 109 out of a group of three passing overhead.

S

 

[wuzak]

I'm not sure that is precisely how that happened, as so far as I know it was a different Merlin that went into the P-40F and L - the Merlin 28 aka Packard V-1650-1, a license built Rolls Royce Merlin XX. The one in the Mustang was a 60 series, (Merlin 68 and 69 / aka Packard V-1650-3 and V-1650-7) license built RR Merlin 63 and 63A much more sophisticated - two stage blower.

The V-1650-3 was equivalent to the Merlin 63. The V-1650-7 was equivalent to the Merlin 66 - lower critical altitude and stronger internals.

Merlin XX was the first two speed Merlin

No, that honour belongs to the Merlin X, as used in the Halifax I, Wellington II and Whitley V and VII.

while Merlin 60 series were the first two stage Merlin, a far more impressive, sophisticated and useful innovation. Rather amazingly, it was developed for some kind of high altitude Wellington bomber.

Yes, originally designed for high altitude bombers.

Then the head of Rolls-Royce suggested they fit one to the Spitfire. The Merlin 61 was the first fighter 2 stage version.

 

[Shortround6]

Other fun fact about the V-1650-1 was that it was made a bit more robust than the original (tougher bearings) and therefore probably capable of higher boost.

This may be fact or it just might be a good story. I don't know. The British took a while to approve higher than 9lbs boost for the Merlin XX although they did eventually get to to the 14lb and 16lb limits mentioned earlier. They were keeping the Merlin XX at 9lbs even though they were using 12lbs in the Melrn III.
The Americans stayed at 9lbs boost for quite some time although using 12lbs boost for take-off. It took until late 1942 and into early 1943 for the US to rate it's engines for WEP so many early manuals make no mention of it. I don't when or if the US "officially" raised the boost limits on the Merlin V-1650-1.
There are also sometimes differences between what the factory says is OK and what the Government says is OK, P & W for instance rarely lists WEP power levels in company charts or tables even though we know both the navy and army used them.