XP-39 II - The Groundhog Day Thread

[Mike Williams]

front line units usually used 91-95 oct Soviet fuels or 100 oct LL fuel (outside mid-1942 - early 43, when Soviet fuel supply was in crisis), I have seen Soviet speed graphs for P-39Q showing the speeds with 95 and 100 oct fuel. Soviet 95 oct was usually used by M-82F and FN engines, so La-5F, -FN, La-7 and Tu-2. Spitfires and P-39s used usually 100 oct LL fuel. IIRC one big offensive was delayed a couple of days so that they could store enough LL fuel for a P-39 fighter division for the operation.

Thank you for the informative post Juha! If you ever get a chance and can put your hands on those P39Q charts showing speeds with 95 and 100 octane, it would be very much appreciated if you can share them here.

 

[Juha3]

As asked

Ps. and my previous message was mostly based on messages made by the pseudo name Altea here in 2009.

 

[Ivan1GFP]

IIRC The La-5FN tested at Rechlin was old and worn-out a/c. On La-5FN max speed, the new production a/c usually were capable to 625 to 635 km/h and the 648 km/h was the speed of a prototype. Soviet prototypes in early 40s tended to be faster than the production a/c.

Hello Juha3,

My original statement regarding maximum speeds for the La 5FN was that anything from about 390 MPH to 403 MPH seems pretty reasonable and that they seemed to vary.
What do you believe the altitude was that the aircraft achieved its maximum speed?

- Ivan.

 

[Ivan1GFP]

P-39 and P-40 are aluminum airplanes. At least the ones operated by the Planes of Fame are. There is some steel, but the structure is aluminum. Landing gear oleos are steel along with a few other items. The engine crankshaft, camshaft, and other parts are steel, but the engine case is aluminum. Mixed material is normal due to strength and heat requirements.

If you tried out aluminum valves in the engine, they wouldn't last longer than a couple of minutes, if that long. In an Allison V-1710, the valve are Stellite (cobalt-chromium alloy) with powdered sodium fill for heat dissipation.

Hello GregP,

Don't forget there are often Magnesium wheels, Copper alloys in the heater / radiator cores.

The Sodium in the valve stems is actually liquid..... Nasty stuff if it should get out.

 

[GregP]

I'm sure it was liquid back in WWII. Not so sure about today, but cannot speak for the state of it before it is exposed to air when a valve gets destroyed. Generally, I leave broken valves alone, and not just because they are not repairable.

 

[ThomasP]

Hey Mike Williams,

In the early-2000s (around 2008?) I ran across a serious paper written on the history of the Russian/Soviet Union/Russian/Ukranian/etc oil industry from the 1800s on to the early 2000's. The author is an accredited historian and his name is Alexander Matveichuk. The paper covers most of the things related to the Russian/Soviet oil industry - ie history and exploitation of oil fields, quality of the crude oil, transport, refining/production, and changing technology. It had a fairly extensive section on the subject of aviation fuel quality and availability in the WWII period. I have not been able to find the original paper/history in a complete form on the internet, however there appear to be pieces of it available on various websites. Some of the websites require memberships.

An abbreviated account of the section on WWII aviation fuel quality, production, and acquisition can be found here:

"Oil of Russia : www.oilru.com : No. 2, 2011 / A HIGH-OCTANE WEAPON FOR VICTORY"

If anyone finds the complete paper on the internet I would very much appreciate it if you would let me know.

 

[ThomasP]

Hey guys,

re sodium filled valves

Metallic sodium is solid at room temperatures, but melts at around 208°F. The value in using it in valves is that it has a very high heat transfer coefficient in liquid form (about 2x liquid water), a boiling point of about 1620°F, and a vaporization temp of about 1645°F. The critical temperature of sodium is also much higher than water (4172F vs 705F) so while sodium is under pressure inside the valve stem it retains a better heat transfer rate to much higher temperatures.

Also the low boiling temperature of water (212°F) and expansion ration of 1600 would result in such high pressures inside the valves that I do not know if valves of the usual stem/wall thickness and weight would survive, meaning a heavier valve body.

These properties of liquid sodium are the reason it is used in sodium cooled nuclear reactors.

 

[Mike Williams]

As askedView attachment 600662

Ps. and my previous message was mostly based on messages made by the pseudo name Altea here in 2009.

Thanks Juha, I'll study on that chart a bit and try to figure out how the P-39 compares with US tests. The first question that comes to mind is - was the engine operated at lesser RPM, boost or both with the differing fuels. Looks like they were using Military power and I wonder what manifold pressure was used. Also wondering if it had external wing guns.

Hmmm, From: Pilot's Flight Operating Instructions for Army Model P-39Q-1 Airplane

War emergency 3000 RPM, 57" MP, critical alt with ram 9,000'
Military power: 3000 RPM, 44.5" MP, critical alt with ram, 15,500'
Max continuous: 2600 RPM, 39.2" MP, critical alt with ram. 14,000'

From MEMORANDUM REPORT ON Pursuit Single Engine P-39Q-5, AAF No. 42-19615

329 mph at SL with 57" Hg.
374 mph at 10,000' with 57" Hg.

 

[Mike Williams]

Hey Mike Williams,

In the early-2000s (around 2008?) I ran across a serious paper written on the history of the Russian/Soviet Union/Russian/Ukranian/etc oil industry from the 1800s on to the early 2000's. The author is an accredited historian and his name is Alexander Matveichuk. The paper covers most of the things related to the Russian/Soviet oil industry - ie history and exploitation of oil fields, quality of the crude oil, transport, refining/production, and changing technology. It had a fairly extensive section on the subject of aviation fuel quality and availability in the WWII period. I have not been able to find the original paper/history in a complete form on the internet, however there appear to be pieces of it available on various websites. Some of the websites require memberships.

An abbreviated account of the section on WWII aviation fuel quality, production, and acquisition can be found here:

"Oil of Russia : www.oilru.com : No. 2, 2011 / A HIGH-OCTANE WEAPON FOR VICTORY"

If anyone finds the complete paper on the internet I would very much appreciate it if you would let me know.

Thanks Tom!

 

[Ivan1GFP]

I'm sure it was liquid back in WWII. Not so sure about today, but cannot speak for the state of it before it is exposed to air when a valve gets destroyed. Generally, I leave broken valves alone, and not just because they are not repairable.

Hello GregP,

I have seen a LOT of destroyed valves. A few of them have even come from cars that we owned.
One of the cars we bought was sold to us after the timing belt broke while the car was running on the highway.
Mr. Piston meet Mr. Valve..... The Pistons were not significantly damaged but the Valves were bent pretty badly.
My Dad mounted quite a few of them into the machine used for grinding valves and spun them to show me that a few that looked just fine were slightly bent.
Plenty of minor to seriously burned valves and various associated pieces were to be found because mechanics have a tendency to keep the more interesting looking destroyed pieces as souvenirs. I don't believe I ever saw one that looked like it once contained Sodium though.

I am still pretty sure that even today the Sodium inside the valves are liquid. Sodium is a liquid at room temperature and the main purpose for it to be inside the valve is to conduct heat away from the head to reduce the likelihood of burned valves.

Some of the early shipboard nuclear reactors even used Sodium as a primary coolant for the reactor core.

Update:
Sodium: Liquid v Solid.... Maybe I wasn't as good in Chemistry as I thought.... <sigh>

-- Ivan.

-

 

[Stig1207]

So to strip 1500 pounds from the P-39, what should be removed?
USAF Historical Study No. 101
Report pgno. 90 (PDF pgno. 101)

 

[ThomasP]

Hey IvanGFP,

re "Sodium is a liquid at room temperature"

Metallic sodium is solid at room temperatures. Melting point is about 208°F.

See "Sodium - Wikipedia" right hand column under "Physical Properties"

 

[XBe02Drvr]

Metallic sodium is solid at room temperatures. Melting point is about 208°F.

That's what they taught us in mech school.

 

[windhund116]

That's what they taught us in mech school.

IIRC, pure liquid sodium metal looks like Mercury (Hg).

 

[Peter Gunn]

Peter,

Thank you! The numbers look fairly close (I don't have them memorized). Did the Germans use Allied fuel to get these results? Did Allied fighters and bombers use the same grade fuel? I would guess it was all the same...

Cheers,
Biff

Hey BiffF,

In the book the author only states that at times he had to wait for the correct high octane fuel before a flight, specifically with the P-47 and the P-51. I'd have to double check but I do believe he was using German fuel as he never makes any mention of using captured Allied Avgas. He was extremely impressed with the Mustang as were his comrades, his written opine was that the only (barely - his word) equal planes to the P-51B he tested were the FW-190D-9 and the Bf-109G-10.

 

[Juha3]

Hello Juha3,

My original statement regarding maximum speeds for the La 5FN was that anything from about 390 MPH to 403 MPH seems pretty reasonable and that they seemed to vary.
What do you believe the altitude was that the aircraft achieved its maximum speed?

- Ivan.

It varied between 5700 m (N 39211525 625 km/h) and 6200 m (N 39210466, 633 km/h) and one figure 634 km/h at 6250 m without info on the serial number and Gordon & Khazanov gives 620 km/h at 6150 m. I don't know are the figures compression corrected.

 

[Juha3]

Thanks Juha, I'll study on that chart a bit and try to figure out how the P-39 compares with US tests. The first question that comes to mind is - was the engine operated at lesser RPM, boost or both with the differing fuels. Looks like they were using Military power and I wonder what manifold pressure was used. Also wondering if it had external wing guns.

Hmmm, From: Pilot's Flight Operating Instructions for Army Model P-39Q-1 Airplane

War emergency 3000 RPM, 57" MP, critical alt with ram 9,000'
Military power: 3000 RPM, 44.5" MP, critical alt with ram, 15,500'
Max continuous: 2600 RPM, 39.2" MP, critical alt with ram. 14,000'

From MEMORANDUM REPORT ON Pursuit Single Engine P-39Q-5, AAF No. 42-19615

329 mph at SL with 57" Hg.
374 mph at 10,000' with 57" Hg.

Yes, the max speeds at around 5000 m indicates the use of Military power, I don't have any specifics because I don't have the book, only many scans from its graphs and tables. But from Gordon's Soviet Air Power in World War 2: P-39Q-10-BE Serial 42-20561 MTOW 3570 kg, max speed 467 km/h at SL, 598 km/h at 5300 m, time to 5000 m 6.4 min, 360 deg turning time, 20-21 sec, 1x37 mm + 4x12.7 mm.
P-39Q-25-BE Serial 43-2467 MTOW 3547 kg, max speed 462 km/h at SL, 586 km/h at 5400 m, time to 5000 m 6.2 min, 360 deg turning time, 19-20 sec, 1x37 mm + 2x12.7 mm.

 

[Ivan1GFP]

It varied between 5700 m (N 39211525 625 km/h) and 6200 m (N 39210466, 633 km/h) and one figure 634 km/h at 6250 m without info on the serial number and Gordon & Khazanov gives 620 km/h at 6150 m. I don't know are the figures compression corrected.

Hello Juha3,

The M-82FN engine installed in these aircraft had a critical altitude in high blower of only 4650 Meters.
Do you find it a bit odd that the aircraft would reach its maximum speed that much higher?
The altitude difference seems a bit much for ram effect.

- Ivan.

 

[fubar57]

Something similar to Post #1291, 561pgs..."USAAF in the South Pacific 1941-1942"

 

[pbehn]

The valve stem in a sodium cooled valve was hollow with the sodium not filling the void, the sodium moved up and down the valve stem as the engine ran giving much more rapid heat transfer from the hottest to the coolest part.