P-40 top fighter?

[tomo pauk]

...
The Allison that about 4% bigger in displacement need a two stage supercharger to pick up 2,000ft of altitude??
Something was not right with the Allison two-stage supercharger if it can barely beat a single stage supercharger.

Not all superchargers were created equal.

The last sentence is very true. It is also true for Allison-made 2-stage superchargers - the 1st gen of the service-worthy types, as on the P-63A, was not as good as second version, let alone the 3rd version (the one with aux stage turning now faster, and has the carb between the stages). The 1st generation also benefitted less with ram effect (1500 ft gain in rated alt vs. 4000 ft for the engines installed on P-63C and later); ram air intake was certainly not in the best position for either engine it had. Difference in rated altitude was ~6000 ft between the engines (no ram), or 8000-8500 ft with ram.
Granted, lack of intercooler hampered the power of the engine, especially at altitude, the latest 2-stage V-1710 when operating on 3200 rpm was about the equivalent of the Merlin 61 from 1942 with regard to the altitude power. With that said, IMO, the main problem of 2-stage V-1710 was that it was perhaps 6, if not 12 months too late to matter. Add to that these engines were installed on the aircraft irellevant for ww2, to wrap up the story.
The intercooled V-1710-119, for the P-51J, was to be the best of the lot, with 1200 HP at 3200 rpm @ 30000 ft, but again it was too late.

 

[Shortround6]

You are aware that those engines in the P-40Q did not have an intercooler, right? And none of the P-63 engines had intercoolers.

I am fully aware that those engines did not have an intercooler.
It is one of the reasons they sucked.
I would also note that some of the P-63s were carrying 25 gallons of ADI fluid (twice as much as an F4U or F6F) in an attempt to make up for the lack of intercooler.
The ADI can be used to not only provide for much increased power at low altitude by over boosting but to increase the critical height of the engine by making the intake charge cooler and denser. This may have become more important with the later -117 engine with it's 7.23 auxiliary supercharger drive gear. ADI was used when the manifold pressure exceeded 58in.

For the P-40Q fans the military power of this engine was at 58in (about,it seems to vary by 0.5 in or so in some accounts but the difference is minor) and top speed at this power rating was 407mph at 24,000ft which while much better than older P-40s is not competitive with with P-47s or P-51s that are running at military power, Now stick in the older -93 engine with less power and a lower FTH and think about if you really have a competitive airplane with either other allied planes or with the better enemy planes, not just if this plane is better than an older P-40 which were viewed as obsolete.

 

[P-39 Expert]

I believe the P-40 could have been made competitive with an F series version of the -93. If you give up on the intercooler then you can improve critical altitude by 3000' by simply moving the carb up to the normal location on the internal stage supercharger instead of on the auxiliary stage. Now you have 1150hp at 24500'. The current single stage Allison-81 in the P-40N made about 780hp at that altitude or 370hp less. This additional 370hp was before increasing the aux stage supercharger gear ratio as was done later.

Comparing the Merlin I to the -93 is a little misleading if you use the often quoted critical altitude of 21000' since that included ram. Critical altitude of the Merlin I without ram was 15600' for 1250hp. This engine improved P-40F speed from 360mph at 15000' to 365mph at 19000'. A -93 with the carb moved up would make 1150hp at 24500' while at that same altitude the Merlin I made only 880hp or 270hp less. That 270hp would have helped the P-40 substantially. Even without moving the carb up the -93 critical altitude was 21500'. At that altitude the Merlin I made only 1000hp compared to 1150hp for the -93. By almost any comparison the -93 was superior to the Merlin I.

I know I'm comparing a two stage -93 to a single stage Merlin I. I know the two stage Merlin 61 made more horsepower. But still, the P-40 could have been competitive with contemporary Luftwaffe fighters in 1943 with a -93 engine.

That same Allison -93 (even before moving the carb up) pushed the P-63A to 422mph at 24000'. That was certainly competitive with any 109 or 190 in 1943.

 

[Shortround6]

Some of your data seems a little off, Please make sure you are comparing the Merlin -1 in the proper supercharger gears.
I also think adding 4,000 ft of altitude for RAM for most planes is a mistake.

RR themselves(or at least the Rolls-Royce Heritage trust) lists the Merlin -1 at 1240hp t 11,500ft, in low gear. believe this is with no ram. They list 1120hp at 18,500ft in high gear.
A US Army test from July of 1942 gives a critical altitude of 12,800ft and an estimated power of 1240hp (power ratings are from charts and not direct measurements) in low gear and a critical altitude of 19,270ft in high gear with 1105hp. this would be with RAM

A British test shows considerably lower speeds but a critical altitude of 14,700ft low gear and 20,400ft in high gear.

However the point is not if the Merlin -1 was as good but if the modifications and disruption to production for the small improvement the -93 Allison (or the F series equivalent) would provide would be worth it.

The -93 (or equiv.) is not a drop in engine for either existing Allison or for the -1 Merlin. It is 16 in longer than the single stage Allison so you have a choice.
1, move the firewall backwards and find new locations for the oil tank and coolant header tank and a few other bits and pieces.
2. extend the fuselage as was done on the P-40Q which was 2 feet longer, the rear fuselage was stretched to counter the extended front fuselage/cowl aerodynamically (although it may have helped with weight too).

The increased dry weight has been mentioned. However the drive for the supercharger required more oil and larger oil coolers (larger radiators would be needed too.)

the -93 (or equiv.) boosted the critical altitude 6-7000ft over the engines in the P-40N but it cost about 5.5-6lbs of manifold pressure. It took 13.4% more manifold pressure to get about the same power at the higher altitude and the extra power that represents was being used to drive the Aux supercharger. the extra power has to be cooled somehow as does the results of the hotter intake charge.

 

[wuzak]

I was confused for a bit. He was comparing the Merlin I with the V-1710-93, one a pre-Hooker single stage single speed engine and the other a 2 stage late 1943 design.

Then I realised that he was talking about the V-1650-1.

 

[Shortround6]

Then I realised that he was talking about the V-1650-1.

Yep, that ( - ) dash can mean a lot at times

 

[P-39 Expert]

Some of your data seems a little off, Please make sure you are comparing the Merlin -1 in the proper supercharger gears.
I also think adding 4,000 ft of altitude for RAM for most planes is a mistake.

RR themselves(or at least the Rolls-Royce Heritage trust) lists the Merlin -1 at 1240hp t 11,500ft, in low gear. believe this is with no ram. They list 1120hp at 18,500ft in high gear.
A US Army test from July of 1942 gives a critical altitude of 12,800ft and an estimated power of 1240hp (power ratings are from charts and not direct measurements) in low gear and a critical altitude of 19,270ft in high gear with 1105hp. this would be with RAM

A British test shows considerably lower speeds but a critical altitude of 14,700ft low gear and 20,400ft in high gear.

However the point is not if the Merlin -1 was as good but if the modifications and disruption to production for the small improvement the -93 Allison (or the F series equivalent) would provide would be worth it.

The -93 (or equiv.) is not a drop in engine for either existing Allison or for the -1 Merlin. It is 16 in longer than the single stage Allison so you have a choice.
1, move the firewall backwards and find new locations for the oil tank and coolant header tank and a few other bits and pieces.
2. extend the fuselage as was done on the P-40Q which was 2 feet longer, the rear fuselage was stretched to counter the extended front fuselage/cowl aerodynamically (although it may have helped with weight too).

The increased dry weight has been mentioned. However the drive for the supercharger required more oil and larger oil coolers (larger radiators would be needed too.)

the -93 (or equiv.) boosted the critical altitude 6-7000ft over the engines in the P-40N but it cost about 5.5-6lbs of manifold pressure. It took 13.4% more manifold pressure to get about the same power at the higher altitude and the extra power that represents was being used to drive the Aux supercharger. the extra power has to be cooled somehow as does the results of the hotter intake charge.

Straight from the "no ram" chart in Tomo's post #50. Most all the Allison charts are no ram. Apples/apples, etc.

 

[P-39 Expert]

I was confused for a bit. He was comparing the Merlin I with the V-1710-93, one a pre-Hooker single stage single speed engine and the other a 2 stage late 1943 design.

Then I realised that he was talking about the V-1650-1.

Yes I was calling the Packard a Merlin. It's a copy of the Merlin. So it should have the same rating. And it pretty much does, if you quote no ram. With ram it sounds like a world beater. No ram brings it back to normal.

 

[P-39 Expert]

Some of your data seems a little off, Please make sure you are comparing the Merlin -1 in the proper supercharger gears.
I also think adding 4,000 ft of altitude for RAM for most planes is a mistake.

RR themselves(or at least the Rolls-Royce Heritage trust) lists the Merlin -1 at 1240hp t 11,500ft, in low gear. believe this is with no ram. They list 1120hp at 18,500ft in high gear.
A US Army test from July of 1942 gives a critical altitude of 12,800ft and an estimated power of 1240hp (power ratings are from charts and not direct measurements) in low gear and a critical altitude of 19,270ft in high gear with 1105hp. this would be with RAM

A British test shows considerably lower speeds but a critical altitude of 14,700ft low gear and 20,400ft in high gear.

However the point is not if the Merlin -1 was as good but if the modifications and disruption to production for the small improvement the -93 Allison (or the F series equivalent) would provide would be worth it.

The -93 (or equiv.) is not a drop in engine for either existing Allison or for the -1 Merlin. It is 16 in longer than the single stage Allison so you have a choice.
1, move the firewall backwards and find new locations for the oil tank and coolant header tank and a few other bits and pieces.
2. extend the fuselage as was done on the P-40Q which was 2 feet longer, the rear fuselage was stretched to counter the extended front fuselage/cowl aerodynamically (although it may have helped with weight too).

The increased dry weight has been mentioned. However the drive for the supercharger required more oil and larger oil coolers (larger radiators would be needed too.)

the -93 (or equiv.) boosted the critical altitude 6-7000ft over the engines in the P-40N but it cost about 5.5-6lbs of manifold pressure. It took 13.4% more manifold pressure to get about the same power at the higher altitude and the extra power that represents was being used to drive the Aux supercharger. the extra power has to be cooled somehow as does the results of the hotter intake charge.

I think critical altitude listed on the Performance Memorandums in wwiiaircraftperformance (19270') is the critical altitude of the plane and not the engine. That would be taking ram into account.

 

[Shortround6]

Straight from the "no ram" chart in Tomo's post #50. Most all the Allison charts are no ram. Apples/apples, etc.

I will give you that, sort of, see further down

Yes I was calling the Packard a Merlin. It's a copy of the Merlin. So it should have the same rating. And it pretty much does, if you quote no ram. With ram it sounds like a world beater. No ram brings it back to normal.

again sort of.....................

I think critical altitude listed on the Performance Memorandums in wwiiaircraftperformance (19270') is the critical altitude of the plane and not the engine. That would be taking ram into account.

You are correct, now as to apples and apples and what is "normal"

Critical altitude of the Merlin I without ram was 15600' for 1250hp.

This is misleading, yes the engine would make 1250hp (or 1240, reading charts is tough) at 15,600ft but the engine had been rated at 9lbs of boost (48in) originally and it would hold that pressure and power (1120hp) to 18,500ft no ram. That is critical height or full throttle height and not picking a power and altitude out of a straight line on a chart. That is the highest altitude the engine would hold 9lbs of boost without ram, If you change the boost limit you change the critical height of the engine and as far as I know no rating of the Merlin XX series (or the Merlin-1) ever coincided with a 15,600ft altitude. the Boost limit was changed from 9lbs to 12lb (54in) and then to 14lbs in low gear and 16lbs in high gear and some later engines with certain strengthen parts (like the supercharger drive) were allowed 18lbs of boost. I don't believe the Merlin V-1650-1 was ever allowed this boost limit. This is top line on the chart Tomo posted the link to. However the line labeled "Max Combat MKS XX, 21,22, 23" seems to be in error or the chart made at a time when these engines were not allowed 16lbs of boost or they simplified the chart and did not post all the different limits/combinations. The US sort of punted and allowed 61in WEP (15.5lbs or very close) on the Merlin V-1650-1 but then had several typos in the pilots manual (like listing the take off power under war emergency for both supercharger gear ratios), the manual also lists the "no ram" values in the "with ram" column.

The Merlin XX series was good for 1490hp at 12500ft at 16lb of boost and boost and power are going to fall off in a straight line as the plane climbs, the line passing through the 9lbs 1120hp at 18,500ft data point.

This engine improved P-40F speed from 360mph at 15000' to 365mph at 19000'

Your characterization of the benefit of the Merlin engine is also misleading if technical correct. yes the max speed only changed by about 5mph but the P-40E (or the K ) was about 25-30mph slower at 25,000ft and up compared to the P-40F, granted neither one flew that high very often. This is often overlooked when comparing the planes, with claims the Merlin only added 5mph or so to the speed while ignoring the substantial increase in performance at the higher (over 15,000ft) altitudes. It was this increase in Performance that lead to the P-40F (and L) being used to equip a number of US fighter groups in North Africa.

 

[P-39 Expert]

I will give you that, sort of, see further down

again sort of.....................


You are correct, now as to apples and apples and what is "normal"



This is misleading, yes the engine would make 1250hp (or 1240, reading charts is tough) at 15,600ft but the engine had been rated at 9lbs of boost (48in) originally and it would hold that pressure and power (1120hp) to 18,500ft no ram. That is critical height or full throttle height and not picking a power and altitude out of a straight line on a chart. That is the highest altitude the engine would hold 9lbs of boost without ram, If you change the boost limit you change the critical height of the engine and as far as I know no rating of the Merlin XX series (or the Merlin-1) ever coincided with a 15,600ft altitude. the Boost limit was changed from 9lbs to 12lb (54in) and then to 14lbs in low gear and 16lbs in high gear and some later engines with certain strengthen parts (like the supercharger drive) were allowed 18lbs of boost. I don't believe the Merlin V-1650-1 was ever allowed this boost limit. This is top line on the chart Tomo posted the link to. However the line labeled "Max Combat MKS XX, 21,22, 23" seems to be in error or the chart made at a time when these engines were not allowed 16lbs of boost or they simplified the chart and did not post all the different limits/combinations. The US sort of punted and allowed 61in WEP (15.5lbs or very close) on the Merlin V-1650-1 but then had several typos in the pilots manual (like listing the take off power under war emergency for both supercharger gear ratios), the manual also lists the "no ram" values in the "with ram" column.

The Merlin XX series was good for 1490hp at 12500ft at 16lb of boost and boost and power are going to fall off in a straight line as the plane climbs, the line passing through the 9lbs 1120hp at 18,500ft data point.



Your characterization of the benefit of the Merlin engine is also misleading if technical correct. yes the max speed only changed by about 5mph but the P-40E (or the K ) was about 25-30mph slower at 25,000ft and up compared to the P-40F, granted neither one flew that high very often. This is often overlooked when comparing the planes, with claims the Merlin only added 5mph or so to the speed while ignoring the substantial increase in performance at the higher (over 15,000ft) altitudes. It was this increase in Performance that lead to the P-40F (and L) being used to equip a number of US fighter groups in North Africa.

Not any P-40s at 25000'. None. If combat ceiling is a 1000feet per minute rate of climb, the E couldn't get to 20000' IN CLEAN CONDITION (no drop tank). The mighty Merlin P-40F could just barely touch 25000' after taking over 14 minutes to lug itself there. This is in clean condition, when virtually every mission was with a drop tank. The standard P-40N (not the early ultralight) couldn't do it, crapping out about 22500'. Put the ubiquitous drop tank on the P-40 and it could barely get off the runway.

That was the Warhawk's biggest problem, every attack came from above. Rugged, maneuverable and well armed, but an absolute death trap in virtually any air to air combat. Needed a two stage engine to get in the fight at all.

And I stand by Tomo's no ram chart.

 

[wlewisiii]

The P 40 was like the Hurricane II and Spitfire MkV, not the best, not the worst, but available.

It was better than people remember because the P-47 and P-51 were so much better later on it seemed like it had always only been the advanced trainer it had become late in the war. Instead the D/E had a (metaphorically) near bullet proof engine and robust and maneuverable air-frame that could take more than the manual said it could and that let it hold the fort until the arrival of newer aircraft.

Had Curtis done serious work on it earlier, so much the better. But as it was, the P-40 was a far more dangerous aircraft than people tend to remember today.

 

[tomo pauk]

...
Had Curtis done serious work on it earlier, so much the better. But as it was, the P-40 was a far more dangerous aircraft than people tend to remember today.

Problem of P-40 was in front of the firewall, not behind.

 

[Kevin J]

Problem of P-40 was in front of the firewall, not behind.

Problem with the P-40 was its superior competitors like the Cobra, Lightning, Thunderbolt and Mustang. The only way the Q is going to be built is for a niche market. Perhaps Soviet Naval Aviation for their war in the Soviet Far East in August 1945 where its range would be useful island hopping down the Kuriles to Hokkaido. No one else needs it.

 

[tomo pauk]

Problem with the P-40 was its superior competitors like the Cobra, Lightning, Thunderbolt and Mustang. The only way the Q is going to be built is for a niche market. Perhaps Soviet Naval Aviation for their war in the Soviet Far East in August 1945 where its range would be useful island hopping down the Kuriles to Hokkaido. No one else needs it.

Again - a P-40 with 1-stage V-1710 and V-1650 has a problem. That means in front of the firewall, not behind. Higher it flies, the bigger the problem.

 

[Shortround6]

Perhaps Soviet Naval Aviation for their war in the Soviet Far East in August 1945 where its range would be useful island hopping down the Kuriles to Hokkaido. No one else needs it.

What range? it held about 160 US gallons of fuel inside the plane. Better than some planes but hardly something to rave about or plan an island hopping campaign around.

 

[Shortround6]

Not any P-40s at 25000'. None. If combat ceiling is a 1000feet per minute rate of climb, the E couldn't get to 20000' IN CLEAN CONDITION (no drop tank). The mighty Merlin P-40F could just barely touch 25000' after taking over 14 minutes to lug itself there. This is in clean condition, when virtually every mission was with a drop tank. The standard P-40N (not the early ultralight) couldn't do it, crapping out about 22500'. Put the ubiquitous drop tank on the P-40 and it could barely get off the runway.

Just for clarity's sake the P-40 was powered by engines that could provide the following.

1150hp at 11,700ft no ram P-40D though K
1125hp at 15,500ft no ram P-40M and N
1120hp at 18,500ft no ram P-40F and L
1100hp at 28,000ft no ram P-40-Q prototypes.

there are minor variations depending on intake manifold and backfire screens.
One might scoff at the "mighty Merlin P-40F could just barely touch 25000' after taking over 14 minutes to lug itself there." but it was doing it in the summer or fall of 1942 and for the US, aside from the P-38, nothing else came close at the time. By the summer of 1943 things were somewhat different and by the Nov/Dec of 1943 the P-40F was definitely 2nd class and by such a margin that the early 2 stage Allison was not going to save it. The engine used in the P-40Qs was too late and never worked right.

and yet we are to believe that an engine that was good for

1150hp at 22,500ft was going to turn the P-40 into a high altitude wonder?

And I stand by Tomo's no ram chart.

You can stand by it. nothing in it is wrong, it just doesn't have everything in it and you are interpreting it wrong.

The Merlin -1 (or XX or 21, 22, 23 was never rated at the boost level that would result in a critical altitude (or FTH) of 15-16,000ft.

Critical altitude of the Merlin I without ram was 15600' for 1250hp.

it was either rated at a lower boost (and higher altitude) or a higher boost and lower altitude. It does show that the Merlin -1 was good for an extra 100-125hp over the 9.60 geared Allison engines at that altitude though.

The -93 and -101 Allisons were well over a year late compared to the early two stage Merlins and the -121 used in the P-40Q was not built until early 1944.

 

[Kevin J]

What range? it held about 160 US gallons of fuel inside the plane. Better than some planes but hardly something to rave about or plan an island hopping campaign around.

Go look at a map of the Kuriles. The islands are all reasonably close together. This would not be like the Pacific Campaign where the next stop off from Okinawa was Kyushu, which was like the distance from London to Berlin.

 

[Peter Gunn]

I am fully aware that those engines did not have an intercooler.
It is one of the reasons they sucked.

*SNIP*

Are you sure they didn't blow instead? After all, we are talking turbo/superchargers which are commonly nicknamed "blowers"...

...

Why are you looking at me like that?

OooooKay, I'll just grab my coat and be leaving now...

 

[Dan Fahey]

The reason the P40 was successful was because the vast majority of the fighting was near ground level.
It was where most of the targets were.
Most were lost in Fighter Bomber configuration from fighters and AA.

The key reason in the early years for losing so many fighters like the Hurricane and Warhawk was tactics and experience.
When those changed there was some parity.

Agree addition short sightedness was not building a Allison engine with higher altitude performance.

Speaking for myself...it was criminal not to upgrade the Allison powered plane with a better supercharging system.
When working properly the Turbo stage gave better performance in the P38.
Here again slow development hampered its capabilities.

What I see is a habitual issue that could have added a huge performance profile for the P40.
When the Brits pumped up the Allison to 70 inches in the P51 and P40 they said the planes were different animals.

The Bearing life in an Allison was three times that of a Merlin.
It had the bandwidth to make a lot more power.