Could the P36 have become America's Zero?

[Mangrove]

Speed is rather dependent on the cowling, the difference in armament may be minor (more drag with 6 guns?) but the fasted figure I have seen for a "service" radial engine Hawk is under 330mph. Climb is more dependent on weight and that depends on protection and structure more than armament, unless you go nuts and try to fit 4 or more .50 cal guns.

The highest ever recorded level flight velocity for a service Finnish Hawk 75 equipped with a 1200 hp Wright Cyclone GR-1820-G205A was 439 km/h at 3505 meters, i.e. 273 mph at 11500 feet. The same figure for a Finnish Hawk with 1065 hp Twin Wasp SC-G was 429 km/h at 1500 meters, i.e 267 mph at 5000 feet.

According to a 1939 factory manual "Curtiss Hawk 75-A Pursuit Airplane", the maximum speed for a plane with a GR-1820-G205A was 323 mph (520 km/h) at 15100 feet. The (Finnish) State Aircraft Factory speculated with was flown by a plane without a radio or armament.

 

[JtD]

At Boscombe Down the Cyclone model managed 300 mph at 15000 feet, the Twin Wasp 300mph at 10000 feet. Note the export Twin Wasp models used 87 octane fuel and produced only around 1050 hp whereas the Army P-36's Twin Wasp used 100 octane fuel with higher boost and got 1200 hp out of the engine. Low altitude performance therefore was significantly better, and top speed marginally higher.

 

[Mangrove]

Note the export Twin Wasp models used 87 octane fuel and produced only around 1050 hp whereas the Army P-36's Twin Wasp used 100 octane fuel with higher boost and got 1200 hp out of the engine.

The exported 1065 hp Twin Wasps indeed used 87 octane fuel, but the Cyclones could utilise 90 octane fuel as per factory and Finnish specifications. However, the Curtiss manual rates the Twin Wasp S3C3-G as 1100 hp. Thus the difference between using 87 octane fuel and using 100 octane fuel was merely 35 hp at takeoff, 40 hp at the sea level and 50 hp when cruising (2200 r.p.m).

Low altitude performance therefore was significantly better, and top speed marginally higher.

I doubt there was a major weight difference between a 1100 hp Twin Wasp using 100 octane fuel and a 1200 hp Cyclone using 90 octane fuel. I still have my doubts regarding the performance figures provided by the factory.

 

[Shortround6]

The weight difference is in the manual/sales brochure. However the Cyclone powered planes had a different cowl than the P &W planes and may have had a different drag.

There are US Army test reports on the wwiiaircraftperformance web site which seem to show a pretty consistent top speed of around 290-295mph using the -17 engine ( Single stage, single speed with FTH of 6500ft.)

With the -23 engine (different gear ratio on the supercharger) speed seems to be about 316-318mph. But only one plane had this engine and it was converted back. Some of the Cyclone powered Hawks had 2 speed superchargers and had more power at 10-15,000ft than the majority of the P&W powered planes even if they had the same take-off power.

The difference between the 1200hp 100octane fuel engines and the 1050hp hp 87 octane fuel engines wasn't that great at 15,000ft. Many of them used the same supercharger and one speed gear ratio and the extra power was only available at low altitudes. Supercharger just couldn't supply enough air at much over 10,000ft.
For some reason many of these engines never got a WEP or even a "military" rating. they got a take-off rating at 2700rpm and a "normal" rating at 2550rpm. Looking at the power available from the P-36 propeller tests it seems as much power could be had at 2550rpm and a higher boost than 2700rpm and a lower boost. I don't know why the boost was limited at 2700rpm. Cooling problems?

 

[Greyman]

I haven't looked too closely at the P36 data from wwiiaircraftperformance.com, but here is a collection of Hawk data I've come across to date.

 

[Jabberwocky]

Very nice Greyman. I've never seen the British and Finnish figures before!

I'm in the early stages of building a database of performance for early war types (speed, climb and roll-rate). Any chance you could send me the raw data?

 

[Greyman]

I can send the British data but the French and Finnish figures were merely typed to me over email and boards like this.

 

[davparlr]

And there you have it. NOBODY had well designed radial installations in 1936-41 compared to what was being done in 1942-45. They were working on it, and working on it hard but it took time and a lot of failed experiments to get on the right path.
The timing for a good radial engine installation is "just" too late to have any real effect for a service aircraft in 1942 (FW 190 was the exception) To be in service in 1942 in numbers, it had to go into production in 1941 which means the design had to be finalized when in 1941?

While I don't really disagree with you on what you have stated here, but I do think there were some very good, non-FW 190 radial installations prior to 1942. Certainly one was the Hughes H-1 which was nearly, according to my estimate, 100 mph faster at sea level than the only slightly bigger and heavier, but more powerful, Bf-109D. Now it was indeed a superb aerodynamically designed hand built aircraft with much effort in detail to reduce drag, but it had to have a very efficient engine housing. Also, I suspect a lot of engineering went into the nacelle design of the B-26 since speed was paramount. Lastly, the F4U which flew in 1940 was quite comparable to the Fw-190 in performance and was MUCH heavier and had a comparatively huge wing (60% larger). I do not believe there was much improvement in the engine installation as the F4U performance increase significantly, although I could be wrong. I think the significant increases in hp post 1942 made smaller items in drag reduction such as elliptical wings and mid mounted wings, and possible radial engine installation of minor importance.

 

[davparlr]

A P-40 with sensible armament and proper tactics should be able to counter the zero.

I would agree.

 

[Shortround6]

While I don't really disagree with you on what you have stated here, but I do think there were some very good, non-FW 190 radial installations prior to 1942. Certainly one was the Hughes H-1 which was nearly, according to my estimate, 100 mph faster at sea level than the only slightly bigger and heavier, but more powerful, Bf-109D.

Some people estimate that Hughes was getting about 1000hp from his P&W R-1535 engine which gives him about 45-48% more power than a Bf 109D. He was using 100 octane fuel for the record run and getting much more power than a "stock" engine running on normal fuel. His engine may have been essentially unmodified but it was not running at factory power levels. Also in record setting form the Hughes aircraft had a 138-140 sq ft wing.

AS for the F4U, depending on altitude it may have 300-400 more HP than the 190 and that is without water injection. The early F4Us did a lousy job with exhaust thrust though.

When you change to the F4U-4 I don't know how much of the improvement is due to the more powerful engine, how much to better use of the exhaust thrust and how much may be due to a better engine installation or better engine , the "C" series engine in the -4 had much better finning and needed less airflow ( drag) for the same amount of cooling (cylinder head and cylinder barrel temperatures)

 

[Jabberwocky]

There was a comment earlier in the thread that US fighters were "cursed" with the M2. This is something of an overstatement, but not too far off the mark. The M2 was heavy for a machine gun, thus not particularly efficient in terms of weight vs firepower. However, it was effective and adequate enough for the jobs it was called on to perform.

There was also a comment that the Zero's armament weight was only 120 kg. This figure is roughly correct, but I don't think it includes the full armament weight, such as ammo and mountings. 120 rounds of 20 x 72B and 1000 rounds of 7.7 mm would have weighed in at 75 kg. The Type 99-1s weighed 24 kg bare and about 27.5 kg installed. The Type 97 weighed 12.5 kg, installed.

Thus, the actual armament weight for an A6M1 or A6M2 was more like 155 kg (75 + 55 + 25).

This weight is really is only applicable for the early Zeros, the A6M1, A6M2, and some A6M3s. The Japanese willingly went with heavier but more effective weapons, and more ammunition, on the A6M3 onwards.

According to the TAIC report on the Zero and competing USN fighters, the A6M Model 52 had a total installed armament weight of 493 lbs/224 kg - of which 101 kg/222 lbs is gun weight. They swapped the Type 99-1 for the more powerful Type 99-2, with higher velocity ammunition and upped the capacity from 60 to 100 rounds per gun. They also added another 200 RPG for the 7.7 mm cowl guns.

Against this, the USN fighters had the following ammunition weights:

F6F: 1076 lbs (120% more)
F4U: 1056 lbs (118% more)
FM-2: 753 lbs (53% more)

 

[Shortround6]

There was a comment earlier in the thread that US fighters were "cursed" with the M2. This is something of an overstatement, but not too far off the mark. The M2 was heavy for a machine gun, thus not particularly efficient in terms of weight vs firepower. However, it was effective and adequate enough for the jobs it was called on to perform.

When you have a 2000hp fighter carrying a decent battery of .50 cal guns and ammo is one thing, when you have a 1000-1200hp fighter it is another thing.

There was also a comment that the Zero's armament weight was only 120 kg. This figure is roughly correct, but I don't think it includes the full armament weight, such as ammo and mountings. 120 rounds of 20 x 72B and 1000 rounds of 7.7 mm would have weighed in at 75 kg. The Type 99-1s weighed 24 kg bare and about 27.5 kg installed. The Type 97 weighed 12.5 kg, installed.

Thus, the actual armament weight for an A6M1 or A6M2 was more like 155 kg (75 + 55 + 25).

It doesn't include mounts but but 1000 rounds of 7.7mm ammo should be about 27-28kg. 120 rounds of 20 x 72B ammo at 200 grams per round is 24kg, not including drums. drums may be 10kg each?

Weight of a total armament installation can run 20-40% more than just the guns and ammo, mounts, ammo boxes, chutes, chargers, gun heat arrangements local reinforcing, etc.

This weight is really is only applicable for the early Zeros, the A6M1, A6M2, and some A6M3s. The Japanese willingly went with heavier but more effective weapons, and more ammunition, on the A6M3 onwards.

They also went for a more powerful engine, or at least one with a 2 speed supercharger to even the power out at different altitudes. the Sakae 21 having almost 200hp more for take-off and as much power at 6000meters at the Sakae 12 did at 4200 meters.

According to the TAIC report on the Zero and competing USN fighters, the A6M Model 52 had a total installed armament weight of 493 lbs/224 kg - of which 101 kg/222 lbs is gun weight. They swapped the Type 99-1 for the more powerful Type 99-2, with higher velocity ammunition and upped the capacity from 60 to 100 rounds per gun. They also added another 200 RPG for the 7.7 mm cowl guns.

Against this, the USN fighters had the following gun andammunition weights:

F6F: 1076 lbs (120% more)
F4U: 1056 lbs (118% more)
FM-2: 753 lbs (53% more)

A P-40 L or early N with four .50 cal guns and 201 rounds per gun had a gun/ammunition weight of about 554lbs. A P-40E with full ammo boxes (1410 rounds for all six guns,235 per gun) was carrying 900lb + of guns and ammo, and that is the "curse".

Six .50s are a pretty good battery and will be an "adequate" armament for most jobs but you need a powerful engine to carry it. The early US fighters didn't have the engine power to pull it off. With four .50s you are trading firepower for performance and depending on the opposition it may be a good trade. but trying to cut weight below four .50s leaves the US with a real problem. A low rate of fire and a gun that depends on kinetic energy for effect. The US never developed (in WW II) explosive bullets or even high capacity incendiary bullets or used mixed belts with incendiaries only making up 40% of the belt. Two .50s as the 'fixed" armament for a fighter is not enough and two .50s with 200rpg is 125kg. another 50rpg is another 13.6kg.

 

[davparlr]

Some people estimate that Hughes was getting about 1000hp from his P&W R-1535 engine which gives him about 45-48% more power than a Bf 109D.

My book "German Combat Planes" by Wagner and Nowarra states that the Bf 109D had a DB 600Aa engine of 910 hp. Wikipedia tends to agree. This is probably close to the Hughes stock R-1535 (as bragged by Hughes, although I am sure it was well tuned) engine running 100 octane. In addition, the Bf 109E-1 with the more powerful 1100 hp DB 601A was only capable of a sea level speed of 290 mph, or 60+ mph less than the H-1, an impressive performance for a radial engine aircraft of similar power. In addition, the H-1 flew seven and a half hours at a high power setting to achieve a cross country record. The engine installation was not only aerodynamically efficient but was also apparently thermodynamically efficient.

He was using 100 octane fuel for the record run and getting much more power than a "stock" engine running on normal fuel. His engine may have been essentially unmodified but it was not running at factory power levels. Also in record setting form the Hughes aircraft had a 138-140 sq ft wing.

This is true but I doubt it makes up for a 35% increase in airspeed.

AS for the F4U, depending on altitude it may have 300-400 more HP than the 190 and that is without water injection. The early F4Us did a lousy job with exhaust thrust though.

Spitfire performance tests show the Fw 190A-3 had a SL max airspeed of 335 mph. The non-MW-50 or C-3 injection BMW 801D-2 engine generated 1700 PS (1677 hp).
http://www.wwiiaircraftperformance.org/fw190/fw190-a3-climb-speed-26-11-42.jpg

The F4U-1 with normal power (approx.. 1700 hp) had a SL max airspeed of 326 mph, or only 9 mph less.
http://www.wwiiaircraftperformance.org/f4u/02155-level.jpg

The F4U-1 is a huge aircraft compared to the Fw 190A-3 with an empty weight being 2600 lbs greater than the 190 it had a previously mentioned much larger wing (see your comments regarding the impact of the H-1 wing).

I don't think the claim can be made that the Fw-190 engine installation was efficient and at the same time stating that the F4U-1's was not.

While I think your general comment on the status of radial engine integration is correct, I do think there were a few very capable radial engine integration designers prior to 1942.

 

[Shortround6]

What date is "German Combat Planes" by Wagner and Nowarra? most of the books from the 90s and later seem to say the "D"s had Jumo 210s like the "C"s. And the 109, while small, was not the cleanest of airframes.
The Hurricane I prototype did 253mph at sea level with a fixed pitch prop and the engine running at 2505rpm and 6lbs of boost. production planes with constant speed props but with a weight of over 3000kg could do about 263 at sea level using 880hp. A Spitfire I with a fixed pitch prop could do 295mph at 2,000ft with the Merlin running at 2370rpm and 6.4lbs boost. the 880hp rating is at 3000rpm and 6 1/4 lbs. Hughes may have had 33% more power in a smaller airplane.

The H-1 did NOT fly 7 1/2 hours at a high power setting. It flew a number of hours at high altitude ( Hughes was on oxygen until in malfunctioned) to take advantage of a good tailwind, the altitude got the plane into air influenced by the jet stream. Hughes had piloted or co-piloted over a dozen commerical west to east airline flights and done one flight with Jackie Cochran's Northrop Gamma. to try to map or gain experience with these tailwinds.

The high altitude flying on oxygen trick had been done by Benny Howard and the Mr Mulligan 4 place cabin monoplane in the Bendix air race.

A Hawker Hurricane once did a flight that averaged 400mph, doesn't mean the plane could actually do it.

Take another look at the pictures of the H-1. There do not appear to be ANY cowl flaps or way of adjusting the airflow, Pretty normal for 1935/36 but unless these guys were waaaay more advanced than the even the designers at the end of the war something is off. The cowl is either set up for max speed or some compromise. Long duration high power climbs may have been a problem. One long climb on a record run overloaded with fuel doesn't prove much as the plane could be climbed slowly watching the temperature gauge.

 

[Juha]

In fact CUc-506 achieved 476km/h at 3500m (418km/h at SL). Source Ilmailu 11/89, see also Lentäjän näkökulma II p. 212 Picture 2 Graph 1.
CUw-572 414km/h at SL and 436,5km/h at 2285m with over-rich and 394km/h at SL and 433,5km/h at 3570m with automix.

Juha

 

[Mangrove]

In fact CUc-506 achieved 476km/h at 3500m (418km/h at SL). Source Ilmailu 11/89, see also Lentäjän näkökulma II p. 212 Picture 2 Graph 1.

What is the primary source quoted by the Ilmailu magazine and Raunio on his book? What was the weight of the plane and rpm pressure of the engine? I have not seen such document nor does any of the documents (dated from 1939 to December 1942) I have copies of mentioned such velocities.

 

[Juha]

What is the primary source quoted by the Ilmailu magazine and Raunio on his book? What was the weight of the plane and rpm pressure of the engine? I have not seen such document nor does any of the documents (dated from 1939 to December 1942) I have copies of mentioned such velocities.

In his book Raunio only thanks the staffs of the Sota-arkisto, Keski-Suomen Ilmailumuseo and Suomen Ilmailumuseo. Not really sure how much time Raunio spent in those but P. Manninen and co helped him and they have gone through at least most of the AF material at what then was Sota-arkisto. And Raunio have had access to the archive of VL .

In his Ilmailu article he mentioned besides US and British materia Selostuksia ja käyttöohjeita CUc and CUw koneita varten. Valtion Lentokonetehdas 1942.

Juha

 

[Mangrove]

In his book Raunio only thanks the staffs of the Sota-arkisto, Keski-Suomen Ilmailumuseo and Suomen Ilmailumuseo. Not really sure how much time Raunio spent in those but P. Manninen and co helped him and they have gone through at least most of the AF material at what then was Sota-arkisto. And Raunio have had access to the archive of VL .

I have also browsed through the material at the Finnish National Archive and various museums but found no such document as stated before. I also think that Raunio's book is quite a typical example of a work of an amateur historian with no accurate references to sources used to produce the book.

In his Ilmailu article he mentioned besides US and British materia Selostuksia ja käyttöohjeita CUc and CUw koneita varten. Valtion Lentokonetehdas 1942.

I have a copy of this manual and it does not contain any values recorded during the claimed CUc-506 test flight.

 

[Juha]

Hello Mangrove
At the early part of the article Raunio writes:"...artikkelin lähdeaineistona on käytetty Valtion Lentokonetehtaan koelentotuloksia CUw-551:llä (alatyyppi A2...), CUw-557:llä (alatyyppi A6...) sekä CU:506:lla (typo in original text) (alatyyppi A4, Wright Cyclone)..." In fact self-clear butat least gives the subtypes.

Juha

 

[davparlr]

What date is "German Combat Planes" by Wagner and Nowarra? most of the books from the 90s and later seem to say the "D"s had Jumo 210s like the "C"s.

Don't really know however the max speed quoted was 322 mph at 13k which is more in line with the 910 hp version verses than the 292 mph at 13k for the 640 hp Jumo. Also, the E-1 definitely had the 601A engine of 1100 hp and could only do 290 mph at SL. If you backed that down to 1000 hp, the difference would even be greater.

And the 109, while small, was not the cleanest of airframes.

Yep, you are certainly right.

The H-1 did NOT fly 7 1/2 hours at a high power setting. It flew a number of hours at high altitude ( Hughes was on oxygen until in malfunctioned) to take advantage of a good tailwind, the altitude got the plane into air influenced by the jet stream. Hughes had piloted or co-piloted over a dozen commerical west to east airline flights and done one flight with Jackie Cochran's Northrop Gamma. to try to map or gain experience with these tailwinds.

I don't know about that. Hughes was not known for his conservative approach to flying, in fact, he liked to push the envelope. I am sure he was pushing that plane. I also do not know if we know what altitude was that he flew at. If he was not on O2 he was not in the jet winds.

Take another look at the pictures of the H-1. There do not appear to be ANY cowl flaps or way of adjusting the airflow, Pretty normal for 1935/36 but unless these guys were waaaay more advanced than the even the designers at the end of the war something is off. The cowl is either set up for max speed or some compromise. Long duration high power climbs may have been a problem. One long climb on a record run overloaded with fuel doesn't prove much as the plane could be climbed slowly watching the temperature gauge.

There is no doubt it was tuned to the high speed record but it was still an impressive performance and honored in the National Air and Space Museum.