Which is the better fighter, P-40F or Typhoon?

[Glider]

At the end of the day if I had to choose one over the other it would clearly be the Typhoon. Its speed, dive, firepower, protection and payload were all considerably superior to the P40. Neither were great at altitude and I think the range was similar to the other.

It's simply no contest

 

[DarrenW]

That would be cool - I'm 100% ok with making this thread a poll I just couldn't figure out how to after the fact.

It's an excellent discussion, would be nice to see how people would vote after seeing all the "facts" presented.

 

[Shortround6]

Well considering that the original WEP setting on that engine was supposed to be 45" Hg and the test you refer to was at 56", the Allison memo mentions their agreeing to 60", mentions units in the field routinely using 66" and 72", and the Mustang I report mentions 70" as a routine practice for sustained periods of time by RAF pilots (and also specifically recommends increasing the official boost limit to 56"), I would suggest that you are somewhat overstating your case. Obviously they routinely overboosted, and clearly overboosting in the field prompted the Air Force, the aircraft company and the engine company to adjust their standards higher. The only real question is how much and when did they start.

Flat out wrong. The engine was rated at 44.6in in military rating. Military was NOT WEP. WEP came later. Military power settings may have had time limits but as long the time limits were adhered to (or even vaugle respected) there were no notions in the log books and no extra maintenance procedures needed. EVERY use of WEP power required a notation on the aircraft log book and decisions by crew chiefs and squadron technical officers as to more frequent spark plug changes and oil inspections.

Again the 70 in or 72 in requires the max forward speed the plane can do and surprise! the Mustang is much faster and can generate a bit more pressure in the intake duct than the P-40 due to the higher speed. Trying to duplicate Mustang max pressures in a P-40 might require higher rpm of the engine.

Could a P-40 outrun a Typhoon at Sea Level through overboosting? I have no idea I wouldn't bet on it. But 72" Hg is quite a bit more power than 56", producing about 200 more hp from what I understand, and no doubt it was useful even if it dipped slightly to a 'mere' extra 100 or 150 hp during a turn or a climb. According to the same couple of P-40N tests you are referring to they were still getting substantial boost right up to 10,000 feet so it's hardly something you can only do while mowing grass. That 1750 / 1780 number represents the top limit clearly, but the larger point - that they were not limited to the 45" Hg / 1150 hp that the manual states seems to somehow get lost in these discussions. Most overboosting was probably up to around the 1400-1600 hp level at anywhere between Sea Level and 9,000 or 10,000 ft depending on the exact variant and engine in question.

smart bet the Typhoon, even running at 7lbs boost was 25mph faster than a P-40 using 56in at sea level,

how ever the bolded part is the main part of the argument, I quoted a test of P-40N using an engine with the 9.60 supercharger gears. this changed the level at which 56in or 50 in or even 52 in could be maintained by 4-5000ft. The D-Es and Ks with the 8.80 supercharger gears are more in the grass cutting territory. you don't get it both ways. The engine in the N could make 1410 hp at 9,500ft at 57in. it could also make 1125hp at 15,500ft at 44.5in vs the 1150hp at 11,700-12,000ft that the older engines made. What the engine in the N could NOT do was run at 70in or close to at sea level without a much increased chance of blowing the engine up. Since the impeller was spinning about 2400rpm faster it was churning the air more and heating it to higher temperatures than the 8.80 gears at the same boost level. Please remember that the power required and the heating goes up with the square of the impeller speed. that change from 8.80 to 9.60 required about 19% more power to the supercharger and of that power about 30% went directly to heating the intake charge, not performing useful work, like compressing the air, which heated the air too.

The fact they were not limited to 45" is not getting lost, it is getting buried by the claims that P-40s could use 60-70 inches at all kinds of altitudes that were impossible with the P-40D-E-K.

Look at the K, with it's stronger engine and slightly modified supercharger it was allowed 60 in (1580hp) at 2500ft. Even if the pilot exceeded that "allowance" the supercharger simply wouldn't supply much more than 60in at that altitude. 62-63in maybe? or maybe due to other changes it was wide open at 2500ft and power was going to fall as it climbed It certainly wasn't going to give you even 1400hp at 9,000ft.

 

[Schweik]

The original 45" setting was mandated for 5 minutes, to me that is WEP. That is why the P-40E is typically listed as having 1,150 hp instead of the ~1,480 hp that it would have at 56". The P-40N test that both of us keep quoting is also one of the only official tests done at WEP that we have access to at any rate. So again the top speed, initial climb rate etc. for the early P-40s were always listed based on that 1,150 hp setting.

The V-1710-73 used by the P-40K was just a V-1710-39 with a strengthened crankshaft and crank case - culmination of a series of strengthening measures which started midway through the -39 production run, obviously to accommodate the overboosting going on in the field as mentioned by the Allison memo etc.

1580 hp at 2500' was very helpful, clearly, for P-40K pilots for the reasons I already outlined in my previous post. Clearly very helpful given the number of aces who flew that particular variant. Of particular value in Russia where almost all the combat took place below 5,000 ft, as well as in a lot of the fighting in the Pacific, Med and CBI where attack planes and dive bombers and so on were the focus of the fighters.

However this thread is about P-40F and L so it's really Merlin XX / Packard V-1650 that matters.

 

[pbehn]

The Typhoon was restricted to 400MPH with rocket rails or bombs attached.

 

[wuzak]

Resp:
We are also pitting one version of the P-40 (Merlin engined) against all variants of the Typhoon? To me it is clear to that the Typhoon was the better in the role of ground attack; performing splendly post D-Day of 6 June. If the Typhoon was used in the MED, I am not aware of it. Typhoon pilots had to use oxygen from the time of take off to touchdown, as fumes polluted their cockpits.

Ans:
"All variants" (production) of the Typhoon were the IA, with 12 x 0.303" mgs, and the IB with 4 x 20mm. And maybe an FR.IB tactical reconnaissance variant.

There were only a few IAs.

 

[DarrenW]

The Typhoon was restricted to 400MPH with rocket rails or bombs attached.

In a dive, level flight, or both? And is that indicated or true airspeed? I'm just trying to get an idea of it's real-world limitations.

 

[Shortround6]

The original 45" setting was mandated for 5 minutes, to me that is WEP.

doesn't matter if that is what you think, that is not the way it was. Many engines had military rating, some never got a WEP rating.
Now please note that not nations rated their engines the same and not all nations test their engines the same.

for instance in 1939 the US required an engine to pass a 150 hour test while the British wanted 153 hours and the French wanted 113.5 hours.

However the US wanted 10 hours at take-off power (which was sometimes the same as military but not always) while the British were satisfied with 9 hours and the French with 3 hours.
The US wanted 50 hours at the "rated" power (max continuous which for an Allison was 1000hp) the British wanted 42 hours and the French wanted 10 hours. there were sometimes requirements for running the engine at an overspeed setting (but not necessarily making more power) to make sure the engine didn't destroy itself in a dive with the propeller overspeeding the engine and the rest of the hours were spent at 70-90% of the "rated" power.

The take-off power (or military) was done several ways and was often up to manufacturer, at least in the US. Usually it was done in 5 minute increments with a cooling off period between each 5 minute segment (might be 3 minutes of some engines) . The cooling off was done at cruise (70-90% of rated) power. Sometimes the manufacturer could request longer periods of time at the high power settings. It was bit of a gamble. If the engine broke during this government test it was up to the manufacturer to fix it and the test would be delayed during repairs.

Obviously air cooled engines might want to take advantage of any cooling breaks they could get.

US WEP ratings as they came about in 1942 called for a test engine to complete 7 1/2 hours at the desired WEP rating done in 5 minute intervals with appropriate cooling off periods (running at cruise). Obviously this built in a fairly good safety margin but it assured that the worst engine out of a production batch of hundreds would probably stand up to the WEP rating in service (only one engine had to pass the test).

I don't know if the US changed the testing procedure at a later date. I have seen engine charts that give 15 minute time limit to military power and 5 minutes to WEP.

Now please note that the Military rating didn't exist in the US until after the start of WW II in Europe. One many early war engines the Military power was the same RPM and manifold pressure used for take-off (but not always).

Some of the early export aircraft were fitted with commercial engines and these engines were often called by their max continuous rating. AS in an 850hp Wright Cyclone (which was good for 1000hp for take off)

The British and Americans didn't rate their engines quite the same and it's gets more complicated the more countries you try to bring into the mix.

US engines were rated at max continuous (rated power) for either 0ne hour or until the fuel ran out (joking, but some engines had no time limit on max continuous) the US had no climb rating, it was either military/take-off or max continuous. the British had a 30 minute rating for climb and then a max cruise or max rich cruise.

and once again you have to consider the fuel. The -33 Allison (and the -39) were originally designed and tested using US 100 octane fuel which had no rich rating it was 100/100 in theory but in practice it could vary from 100/97 to 100/105 or so. Not kidding, a few batches were later tested and found to be under 100 when running rich. fuel testing was done only at lean mixture at this time. The performance number scale and ways to measure rich mixture response only came into being in either late 1940 or early 1941?
The British knew they could use more boost with their fuel than with using US fuel but they didn't really know how much more since they couldn't measure the fuel differences from batch to batch or specify the actual response they wanted from the manufacturers. BoB fuel varied from around 100/115 to around 100/120.

Long winded way of saying until you had 100/125 or 100/130 fuel you had about zero chance of rating an engine using high boost for WEP. You could run an Allison -33 or -39 at full military power on US 100/100 octane fuel.

 

[eagledad]

Gentlemen,

Please find attached an Australian report on the P-40N. Toward the end of the report, there is data for the P-40N-10 at 57" mp
As an aside. from the 325th FG website, it appears that the group also flew P-40K's along with the F/L.
Eagledad

 

[Schweik]

Thanks a million, that is a magnificent document. I recommend uploading it to ww2aircraftperformance.org. Really helpful, it has a lot of detail there!

 

[Schweik]

As an aside. from the 325th FG website, it appears that the group also flew P-40K's along with the F/L.
Eagledad

They did also use a few P-40Ks for a while, the 57th FG also used some in one squadron for a few weeks. The issue was replacement Merlin engines for the P-40F/L, apparently the American army hadn't thought to send any. Eventually the RAF scrounged up enough Merlin XX (basically identical to the Packard -1650 in the P-40F) and they straitened that out.

This was also part of the reason why they (325 and 57th FG) switched over to P-47s

 

[pbehn]

In a dive, level flight, or both? And is that indicated or true airspeed? I'm just trying to get an idea of it's real-world limitations.

Its on the Wiki page, pilots have referred to it being stable attacking targets at 400MPH so I would assume level flight IAS.

 

[Shortround6]

They did also use a few P-40Ks for a while, the 57th FG also used some in one squadron for a few weeks. The issue was replacement Merlin engines for the P-40F/L, apparently the American army hadn't thought to send any. Eventually the RAF scrounged up enough Merlin XX (basically identical to the Packard -1650 in the P-40F) and they straitened that out.

This was also part of the reason why they (325 and 57th FG) switched over to P-47s

The Americans had only procured about 20% more spare engines than airframes which was an abnormally small amount. What they did with the spare engines I have no idea (held them in storage or shipped them late?) Due to the lower air intake on the Merlinit is thought (no proof?) that the Merlins didn't last as long in dusty/sandy conditions compared to the Allisons which further hurt the spares situation. Most sources claim (but could be wrong) that the British broke down up to 600 Merlin's to provide spare parts for overhaul rather than supplied replacement engines (US Merlin 1650-1s used a different propshaft spline for one thing than the British XX engines did. I believe it also used a different carburetor. )

 

[DarrenW]

Its on the Wiki page, pilots have referred to it being stable attacking targets at 400MPH so I would assume level flight IAS.

Thanks for the info.

 

[Greyman]

The Typhoon was initially limited to:

- 525 mph IAS when diving​

- 400 mph IAS when diving with bombs​

This was later lifted to:

- 480 mph IAS when carrying RP or rails only​

- 450 mph IAS when carrying bombs​

- 400 mph IAS when carrying other stores​

I don't know the date of change, but I'd say the absence of a figure for RP in the first set of limits is a clue.

*EDIT for what it's worth, the 1943 AAF P-40 manual (E, F, L, K, M and N) says the aircraft is 'red-lined' at 480 mph IAS, and says not to dive faster than 350 mph IAS with a bomb.

 

[Stig1207]

These are all basically from January to July 1943, during which period they lost 17 fighters in combat

There are also 12 lost to unknown causes here

Another source posted by Eagledad in another thread gave 481 USAAF P-40 claims in the MTO.

 

[Schweik]

The Typhoon was initially limited to:

- 525 mph IAS when diving​

- 400 mph IAS when diving with bombs​

This was later lifted to:

- 480 mph IAS when carrying RP or rails only​

- 450 mph IAS when carrying bombs​

- 400 mph IAS when carrying other stores​

I don't know the date of change, but I'd say the absence of a figure for RP in the first set of limits is a clue.

*EDIT for what it's worth, the 1943 AAF P-40 manual (E, F, L, K, M and N) says the aircraft is 'red-lined' at 480 mph IAS, and says not to dive faster than 350 mph IAS with a bomb.

The P-40 dive speed limit was basically whatever transonic speed was at the given altitude. They could out dive any aircraft in the war.

This P-40 (E I would guess) made 661 mph in a dive

 

[Airframes]

A couple of clarifications regarding the 'faults' with the Typhoon.

1. Ditching. Although the large radiator housing played a part, the actual dangerous to lethal ditching 'qualities' were the fault of the wing. Ditching trials with the Tempest (same engine and radiator housing), showed that the aircraft was no worse than any other, and better than many when ditched.
2. Engine Reliability. Once the valve and other engine problems had been sorted on the later series engines, reliability (and fire problems) were more or less eradicated, although the Sabre was still a complex engine to maintain, especially in the field. The carbon monoxide into the cockpit problem, although reduced, was not fully resolved, and pilots were advised to remain on oxygen during all flight aspects.
3. Empennage weakness. After the loss of a number of Typhoons due to the tail unit breaking away, particularly in a high speed dive, and with at least one pilot surviving to describe what had happened, initial modification involved the reinforcing, internally, of the transport joint at the tail, by the addition of flange plates over the frame joints, and the fitting of external 'fish plates' over the joint circumference. This was found to (almost) cure the problem, but vibration, sometimes severe, was still experienced under certain flight conditions. Further trials and investigation suggested control surface buffeting, and the fitting (including retro-fitting to earlier airframes) of the larger Tempest tail planes and elevators cured the problem.

 

[Shortround6]

A couple of clarifications regarding the 'faults' with the Typhoon.

1. Ditching. Although the large radiator housing played a part, the actual dangerous to lethal ditching 'qualities' were the fault of the wing. Ditching trials with the Tempest (same engine and radiator housing), showed that the aircraft was no worse than any other, and better than many when ditched.
2. Engine Reliability. Once the valve and other engine problems had been sorted on the later series engines, reliability (and fire problems) were more or less eradicated, although the Sabre was still a complex engine to maintain, especially in the field. The carbon monoxide into the cockpit problem, although reduced, was not fully resolved, and pilots were advised to remain on oxygen during all flight aspects.
3. Empennage weakness. After the loss of a number of Typhoons due to the tail unit breaking away, particularly in a high speed dive, and with at least one pilot surviving to describe what had happened, initial modification involved the reinforcing, internally, of the transport joint at the tail, by the addition of flange plates over the frame joints, and the fitting of external 'fish plates' over the joint circumference. This was found to (almost) cure the problem, but vibration, sometimes severe, was still experienced under certain flight conditions. Further trials and investigation suggested control surface buffeting, and the fitting (including retro-fitting to earlier airframes) of the larger Tempest tail planes and elevators cured the problem.

There may have been a component of vibration from the airscrew traveling through the airframe and affecting the joint/tail. Many of the later Typhoons also got a 4 blade airscrew. although there were a few problems with this.

 

[Shortround6]

The P-40 dive speed limit was basically whatever transonic speed was at the given altitude. They could out dive any aircraft in the war.

This P-40 (E I would guess) made 661 mph in a dive

You are, of course, joking.

I have seen some old books published during the war that claim the P-40 could do over 400mph in level flight (and not the Q).