Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)

[SaparotRob]

Inspired by the "Most overrated fighter of WW 2", I had just spent about 40 minutes trying to figure out the range of a mid 1943 P-47 to compare it to a mid 1943 P-39. It's tougher than I thought and I think I can't trust the Wiki numbers. I'm guessing it's some average or a cherry picked distance of a specific model I can't link to. I'm thinking that with the right date or models I could see for myself if the P-47 had a better combat radius than the Airacobra. Clean airframes, no tanks.
Am I the only one who has to scroll up to see just what thread I'm posting to as they all seem to be the Groundhog thread?

 

[SaparotRob]

Gee willikers, He's got me looking up technical info!

 

[Shortround6]

Gee willikers, He's got me looking up technical info!

You have to use numbers in the range charts in the flight manuals.
Many of which are on this web site.

Other Mechanical Systems Tech.

ww2aircraft.net

And you have to use a bit of common sense.
For example the P-47 at 14,000lbs could use around 100 gallons of fuel just warming up, taking off and climbing to 25,000ft. The initial warm up and take-off are done on internal fuel.

Operational radius is always much less then than even 1/2 the range.

 

[buffnut453]

This was a one-off example. I have shown numerous times how a properly equipped 1942 P-39 would have weighed 7150 lbs.

Bell did show how P-39 weight could be reduced by 1000lbs in May 1943. Details were not provided in the book.

That's absolutely priceless. You criticize me for finding one whole mark of Spitfire that exceeded 12,000lb AUW (let's ignore for the moment that I actually identified 2 different marks, plus another 2 that exceeded 10,000lb) and yet you're staking your claims for a high-performance P-39 on a single airframe? You should go on the stage....you'd have them rolling in the aisles.

The bottom line is that Bell was on entirely the wrong track with the P-39. Every customer was asking for higher altitudes, higher speeds, longer range and heavier weapons. Putting the engine in the middle of the fuselage imposed a lot of additional structural weight and limited growth potential for bigger engines. For aircraft like the Spitfire, changing from the Merlin to the much more powerful Griffon was relatively straightforward because most of the structure aft of the firewall remained unchanged (yes, the tailplane and rudder were enlarged on later versions...but those are relatively minor changes). Trying to shoehorn a larger engine into the P-39 essentially involves a redesign of the entire airframe; it's not airframe growth, it's a completely new design.

While other manufacturers were incorporating more powerful engines, Bell's only response was to tinker within the limits of the P-39 design. For example, we have the continual flip-flopping on the weight of armour installed in different versions. That wasn't happening because of changing operational requirements. It was simply an example of Bell trying to eke out performance from an airframe that lacked growth potential.

Look at this from the customer perspective. You have every manufacturer out there bolting on new, more powerful, engines to improve performance and cope with increased weights. Then you have Bell tweaking round the edges to reduce weight. Given that procurement is trying to plan months in advance, where would you put your money if you were responsible for buying aircraft? Would you invest in designs that were demonstrating growth potential to meet operational needs or place orders with a company that's futzing with the same basic design with only modest performance improvements (and at the cost of operational equipment/weapons/fuel)?

It's interesting to consider Bell's postwar work which, from a high-performance fighter perspective, focused on one-off or limited-run experimental types. That work aligns pretty well with the behaviours exhibited by the company during WW2, tweaking one-off airframes to maximize performance.

 

[pbehn]

Gee willikers, He's got me looking up technical info!

The range given for an aircraft is under certain conditions. Escorts operated under escort conditions. The P-39 if tasked to escort a US bomber formation would be getting close to where maximum speed and stall speed are the same and so cruising speed is maximum speed also. The range of a fighter is the start point for the operational planners who have to build in all the things that use fuel up and then build in contingencies for screw ups. If you draw a line from Norwich in the middle of East Anglia where many bombers were to Berlin you go across almost all the heavily defended industrial areas of NW Germany and the Netherlands so you cant take a straight line.

On August 17 1943 the Schweinfurt Regensburg raid saw RAF Spitfires escorting to Antwerp with P-47s taking over as far as Eupen, 82 miles further.

 

[Shortround6]

You have four companies that used Allison engines.
The P-39 and P-40 are the most contemporary.
The Mustang was a bit late and unloved by the USAAC
The P-38 was a twin and used turbos.

The P-40 was a 1934/35 design with a new engine tacked on. Curtiss did rather well with it as it was the right plane at the right time. It's time had gone past by 1943/44 though.
Bell P-39 was later in design and Bell mucked things up by trying to be too clever. Too much "stuff" in too small an airframe. No idea on how to design cooling ducts or place radiators/oil coolers and so on.
Instead of taking the bull by the horns and building a slightly larger airframe they seemed to want to take stuff out (like fuel) and blame the customer for not seeing the brilliance of the design.
The fact that the plane couldn't reach the enemy with less fuel and was therefore useless seemed to go over their head

US didn't need point interceptor bomber destroyers in 1942-43.
The Idea behind the 37mm cannon (which Bell and the USAAC held onto for far too long) was to destroy very large bombers like the US bomber Mafia was dreaming about (see B-15 and B-19). Turns out the 37mm wasn't really needed, yes it could kill smaller aircraft rather well given a hit but it was hard to hit with.
USAAC hung onto the 37mm for quite some time in other prototypes.
.

 

[GregP]

Best post ever.

Regarding the "Urchin-Snouted Codiece" comment, I offer this spreadsheet I created some years ago to generate Monty Python insults. Simply follow the instructions.

I am in Las Vegas right now with VERY SLOW internet. I'll post the Shakspearian Insult file when I get home tomorrow.

 

[SaparotRob]

The range given for an aircraft is under certain conditions. Escorts operated under escort conditions. The P-39 if tasked to escort a US bomber formation would be getting close to where maximum speed and stall speed are the same and so cruising speed is maximum speed also. The range of a fighter is the start point for the operational planners who have to build in all the things that use fuel up and then build in contingencies for screw ups. If you draw a line from Norwich in the middle of East Anglia where many bombers were to Berlin you go across almost all the heavily defended industrial areas of NW Germany and the Netherlands so you cant take a straight line.

On August 17 1943 the Schweinfurt Regensburg raid saw RAF Spitfires escorting to Antwerp with P-47s taking over as far as Eupen, 82 miles further.

I wanted to see if the P-47 variant that was operational on say, Bastille Day 1943, was competitive in range to the Airacobra variant OPERATIONAL on that same day. I came up with P-47D -25RE (?) and the P-39D. I looked at the range charts for the P-47, no external fuel, on that section's second page. After some eye strain, I went out for errands. I think it was statute 760 miles, not nautical miles. So divide in half, 380 miles. Now eliminate the fooling around time, whatever percentage that is which would leave us with 275 miles.
I then started looking up the range charts of the P-39 and as the Lord is my witness, I didn't want to read anything more about the P-39.

I wanted to just briefly respond to your post. It's too late for that.
I understand that the distance to the target is not a straight line. Someone brought up the woefulness of the P-47's range in this, the P-39 thread. So I started to look for myself. I think the P-39's range was less than that. I have not yet completed my research. Nor will I ever.

 

[SaparotRob]

Of course, your mileage may vary.

 

[GrauGeist]

USAAC hung onto the 37mm for quite some time in other prototypes.

It's almost comical how some air forces were obsessed with certain things.
With the USAAC/USAAF, the 37mm seemed to be their holy grail of combat.
Aside from the P-39/P-63, they fooled with the P-38, XP-58, XP-67 (which was planned to be armed with six!), XA-41 (planned to be armed with four), XP-72 (two or four) and XP-54 (two).

I'm sure I'm forgetting some, too...

 

[pbehn]

Of course, your mileage may vary.

Pilots and mission planners generally didnt deal in miles, it was all relative to fuel. A late poster here said that for him a long mission was 11 hours in a B-17. A long mission in a P-51 was six hours, and that is close to what humans can do regularly on such missions. A Merlin burns fuel at about 50 gallons per hour when running economically and 3 times that on full power. With 200gals ext fuel and 265 int fuel it has enough for over 9 hrs economical running which shows how much everything eats into its economy. For all these planes the absolute maximum for consideration is how far it can go on internal fuel having dropped its tanks and had 15-20 minutes combat. There was a 170 gal slipper tank for a Spitfire which could get you to a place you just cant get back from

 

[33k in the air]

I wanted to see if the P-47 variant that was operational on say, Bastille Day 1943, was competitive in range to the Airacobra variant OPERATIONAL on that same day.

The general rule-of-thumb is to take the range and divide by three. That will get you a reasonable approximation of the combat radius. (The actual fraction, of course, varies with the details.)

 

[33k in the air]

You have to use numbers in the range charts in the flight manuals.
Many of which are on this web site.

Other Mechanical Systems Tech.

ww2aircraft.net

And you have to use a bit of common sense.
For example the P-47 at 14,000lbs could use around 100 gallons of fuel just warming up, taking off and climbing to 25,000ft. The initial warm up and take-off are done on internal fuel.

Operational radius is always much less then than even 1/2 the range.

And radius can be extended by such things as including the distance covered in climbing to combat altitude, or by changing the amount of reserve fuel allotted.

 

[Peter Gunn]

Of course, your mileage may vary.

I see what you did there...

 

[Peter Gunn]

This sounds like a job for SaparotRob !

See my post #2,232, he's too busy becoming the Edsel expert...

 

[P-39 Expert]

So they used something heavier? So what is your point? How can you claim the British wanting things that increased weight was perfidy when the US was doing exactly the same. BTW you are doing that thing again where your "never" becomes not "often". Of those 100,000 the P-39s used by the USA as a weapon was also an insignificant amount.

And how does that look against a P-38, P-47, Mustang I, Spitfire IX, Typhoon? Would you cross the Channel to take on an Fw 190 with it?

My point is: British were specifying 30cals on P-400s when shortly the AAF/USN would move on to 50cals and cannon.

A 1942 P-39/400 at 7150lbs looks pretty good against P-38s since they weren't in combat until late 1942. P-47 was not in combat until spring 1943. Would outclimb a Mustang I and go about the same top speed. Spitfire IX started in mid '42 but production didn't get rolling until :ate '42. Would outclimb a Typhoon and about as fast. As far as a FW190A5 it would be outclimbed by a 7150lb P-39/400.

 

[P-39 Expert]

And it was also specified in the Bell Model 13, P-39C which suggests the British did NOT specify the gas heater. This has been raised several times but you keep ignoring this fact.

If the gas heater was useless, then it's down to Bell who included it as standard equipment in the Model 13. The British would simply have ensured cockpit heating was provided...it was down to Bell to ensure the heating system worked correctly.

See my post #2617.

 

[P-39 Expert]

Yes the British were experimenting in the BoB with cannon, that was a year before the P-39 arrived in UK. You have repeatedly quoted the performance of your 1942 super light P-39 as being useful in Europe, even suggesting it could be used as a bomber escort.

Never suggested a 1942 P-39 could be used as a bomber escort. Escort by AAF P-47 didn't begin until Spring '43.

 

[P-39 Expert]

It's worth noting that one of the main reasons why the RAF rejected the Airacobra was compass deviation when its guns were fired, at rates as high as 160 degrees, which rendered it completely useless. This was clearly unacceptable to the British, but eventually, a fix was found, although by that time the decision had been made to replace the Airacobras in service with Spitfire Vs, which had better performance at any rate. Did the US forces ever record this as an issue with the P-39?

No.

 

[P-39 Expert]

Did it improve the type's performance at all?

One example. One. Improved climb to 5000' by 25%.