1950: Lavochkin La-9 v.s Grumman F8F-1B Bearcat

[GregP]

First Tomo,

Thank you for the pic-post!

Can't read it but I see the FN in Greek. Exactly what book is this from and why should it be believed over other references? I have several that say diffferently for the FN.

Not arguing, just asking as I can't read most of it, but the Greek letters are easy. 1,850 cv is about 1,824.7 HP in the U.S.A. (550 ft-lbs/min type HP).

As long as I'm asking, do you know the airfoil section for the root and tip chords?

 

[Koopernic]

That a Soviet engine in 1946 would be producing less power than a BMW801 in late 1943 is somewhat hard to believe.

 

[Juha]

Hello Greg
most documets/WWII publications on engines I have seen agree the 1850cv WEP, 1630cv or 1650cv military max power at 1650m, but claimed either 1430cv or 1450cv as max 2nd gear sc power at around 4700m, but some a/c books give for La-5FN/La-7 1470cv as max 2nd gear sc power at around 4700m, the low level power being same as in the WWII sources.

 

[tomo pauk]

First Tomo,

Thank you for the pic-post!

Can't read it but I see the FN in Greek. Exactly what book is this from and why should it be believed over other references? I have several that say diffferently for the FN.

Not arguing, just asking as I can't read most of it, but the Greek letters are easy. 1,850 cv is about 1,824.7 HP in the U.S.A. (550 ft-lbs/min type HP).

As long as I'm asking, do you know the airfoil section for the root and tip chords?

The La-9 and -11 were supposed to be outfitted with laminar-flow wing, I dont know the exact profile used. The LaGG-3, La-5 and -7 was using the NACA 230 series.
The graph is from the manual for the ASh-82FN. The name "АШ-82ФН" is in cyrilic, the type of letters that emanated from Greek wrting. The monks (later sainted) Cyril and Method brought it from Byzantium to the many Slavic people in the early Medieval. It is in use in Serbia and Bulgaria today, for example, the last known writtings in Croatian cyrilic were dated circa 1500-1600s.

That a Soviet engine in 1946 would be producing less power than a BMW801 in late 1943 is somewhat hard to believe.

I don't see a reason why it would produce more than BMW 801 - both were using the same technology and were roughly of same size. The 801D turned greater RPM and was using better fuel from mid-war on.

 

[Shortround6]

That a Soviet engine in 1946 would be producing less power than a BMW801 in late 1943 is somewhat hard to believe.

Not really, the Soviets never really progressed beyond 95 octane fuel. At least for service engines. Add in the fact that the ASh-82 was never rated for more than 2500rpm for take-off and the other ratings were at 2400rpm and the lower power rating seems inline. A Wright R-2600 which was slightly bigger, used 100/130 fuel and ran at 2800rpm for take-off made 1900hp.

 

[tomo pauk]

Another thing that might be observed is that ratings for the ASh-82FN, other the 5-min overboosting in low gear, were called 'nominal'. So we might be better off comparing the 30 min power of the BMW 801D with that nominal power - 1320 CV at 2400 rpm at 5300m equals the nominal power of the ASh-82FN at that altitude. Granted, the 801D was rated for greater powers for short term ratings.

 

[grampi]

Off topic, the La-9 is much more pleasing to the eye imo.

I was thinking just the opposite...the La-9 looks like a Russian version of the P-36 to me...the Bearcat on the other hand looks like a mad hornet ready to take on anything in the sky....

 

[GregP]

For those of you who wish to pursue this, I found the airfoils at The Incomplete Guide to Airfoil Usage: The Incomplete Guide to Airfoil Usage

The Grumman G-58 F8F Bearcat, both the F8F-1 and F8F-2, had an NACA 23018 airfoil at the root and an NACA 23009 airfoil at the tip.

The Lavochkin La-9 was a different animal. The LaGG-1 through La-7 all had an NACA 23016 airfoil at the root and an NACA 23010 at the tip. The La-9 changed to a "TsAGI Laminar Airfoil" at the root and tip ... and that's all the explanation I can find, so coming up with a coherent analysis might be tough. At this time, I do not know how a TsAGI laminar arfoil would different from another laminar airfoil.

Thank you Tomo and Juha. I am assuming the 1,850 cv is wet War Emergeny Power (limited boost liquid ADI) and 1,630 - 1,650 cv is dry military power. Max without ADI. That makes sense. Most of the sources I have seen did not have the wet power, they only had one number. If two powers had been present, I would have suspected ADI for the upper number.

I must say I am impressed with the La-9. I have seen many Bearcats but never a "real live" La-9 ... only pics of the one Ray Hanna used to fly. It is a good-looking aircraft indeed.

I still need some hard performance charts for the La-9 to want to open my mouth about a winner, but the La-9 makes a really interesting opponent for the Bearcat. Had jets not come along, the fifties might have been a very interesting time for aviators.

 

[Koopernic]

Not really, the Soviets never really progressed beyond 95 octane fuel. At least for service engines. Add in the fact that the ASh-82 was never rated for more than 2500rpm for take-off and the other ratings were at 2400rpm and the lower power rating seems inline. A Wright R-2600 which was slightly bigger, used 100/130 fuel and ran at 2800rpm for take-off made 1900hp.

Shvetsov ASh-73 that was used on the Tu-4 (B-29 clone) wasn't quite as much a laggard compared to the R-3350. I would imagine they knew the direction was going to be jets (apart from long range aviation) and chose not to invest in catching up.

 

[dedalos]

Once again , for a soviet fighter of the era, we must note its very low weight
And once again i ask
1) What Navigation and radio equipmentit had? What flying instumentation it had?Hoe effective its gunsight was?The pilots work load?
2) What strength limits ithad? What was its mach limit?What armor it carried?
3) While F8F was also a dedicated low level fighter,the La s altitude performance was terrible for its day.In korea could barely reach the speed of b29s
4) What was its exterior load capability?
5)The f8f could reliably deliver 2300hp, and even up to 2800hp if nessecary. The La s 1850 hp ,was for very short duration at very low level, and its questionable its RELIABILITY at this power setting

Judging 2 aircrafts is more than just throwing numbers.
In my opinion the F8F is FAR superior

 

[tomo pauk]

In my opinion the F8F is FAR superior

It probably is.

...
Thank you Tomo and Juha. I am assuming the 1,850 cv is wet War Emergeny Power (limited boost liquid ADI) and 1,630 - 1,650 cv is dry military power. Max without ADI. That makes sense. Most of the sources I have seen did not have the wet power, they only had one number. If two powers had been present, I would have suspected ADI for the upper number.
...

The ASh-82FN (or other -82 radial) never featured the ADI. The over-boost was of the 'dry' variety, boost of 1200 mm Hg means about 47.25 in Hg (+8.5 psig, ~1.63 ata). Rather a modest value, for example the R-2800 'B' was at ~52 in Hg for military power, on better fuel though (100/130 grade).

 

[GregP]

If I am not mistaken, 1200 mm HG converts to 77.2 inches HG (USA), 23.2 psi (British), and 2.665 ata (German). Most of our radials were not boosted that high.

For refrence, 55 inches HG is 637 mm HG.

1 ata = 28.958" HG = -0.326 Bar = -3.258 kPa = -0.473 psi

I posted a spreadsheet that does the conversions some time back but can do it again if anyone wants it.

Gut feel, I think the F8F is far superior in general, too, but I have almost NO documentation on the La-9 and was attempting to not claim what I don't know. I'd like to confirm it before claiming it. Been bitten by that before ... in here.

 

[Juha]

one in=25,4mm; 4.7in=120mm (a RN naval gun) so 1200mm ~47in
And as Tomo wrote in the ASh-82FN case forsage means "dry" overboost

 

[GregP]

These are not linear units of equivalence, they are national standard units of manifold atmospheric pressure. Some are absolute pressure and some are gauge pressure, notably British Boost. 1 ata is NOT 1 standard atmosphere, it is 1 technical atomsphere.

1) The U.S.A. uses inches of Mercury (in Hg) absolute pressure.

2) British psi of boost (lbs Boost) = [(14.696/29.92) * in Hg] – 14.696 ... gauge pressure of boost. Hence you subtract the 14.696.

3) German Technical Atmospheres (ata) = (in Hg) / 28.958 ... not a stndard atmosphere.

4) Japanese / Russian mm Mercury (mm Hg) = (in Hg – 29.92) * (760 / 29.92)

If you look below on the figure , you will notice 47.25 inches of Mercury (U.S.A. units) is right at 440 mm HG (Japanese units), right where my spreadhseet says it is (really it converts to 440.2 mm HG) ... and it is also right at +8.5 psi Boost (British units) and 1.632 ata (German units). I didn't make this stuff up, but it isn't all that hard to come up with it, either.

I can post an "extended" chart if anyone is interested, that covers idle to Reno racing levels. The chart below covers from near cruise to upper levels usually attained by radials.

The Russians typically used mm H2O, not mm HG ... but they DID use mm HG every once in awhile. When they did, it matched the Japanese units exactly, not surprisingly.

 

[Juha]

Hello Greg
thanks for explanation, I also have that scale, but were the Japanese and Soviet scales identical? I can understand that Japanese used the same 0 level than Brits but somehow I'd expect that the Russians would use a system with similar 0 level than that used by French (whatever it was) or Germans? After all they used cv/ps not hp.

Edit: German wwii book on Soviet engines gives for M-82FNW (must mean 82FNV) 1850 ps at 1.60 ata 2500rpm

 

[GregP]

If anyone is interested, attached is a spreadhseet that converts among the popular WWII aviation engine boost units and has a table from zero inches of Mercury up through 150 inches of Mercury.

That's the most boost that anyone I know of runs in an aircraft piston engine, and that happens at the US Reno National Championship Air Races every year.

The engines that run that boost are not Merlins. They start with a Merlin block, add Allison G-series rods, custom pistons and valves and springs, modern mags or electronic ignition, spray bars, run ADI, and run very low compression ratios. One even has Dwight Thorne custom racing cams and all the others WANT them. Most are running transport heads because that's mostly what is left to run AND they are strong. Reduction gear ratios vary from stock and props are almost all shorter than legal for Limited Category aircraft.

- Greg

View attachment Boost.zip

 

[GregP]

Hi Juha,

cv or ps is power. The U.S.A. uses 550 ft-lbs/sec HP while others use boiler or metric HP. Other units are available. Some use kW. Power-to-weight can be in lbs/HP, lbs/cv or ps, cv/kg, kW/kg, or even the inverse of these. Converting isn't difficult.

The manifold pressure scale is just manifold pressure and is unrelated to power units. It really only matters whether the manifold pressure is absolute or gauge pressure. The Germans are the only nation who used something related to technical atmospheres rather than internation standard atmospheres ... and, as long as you know that, conversion isn't all that difficult.

If you use gauge pressure, you get boost pressure, not MAP absolute.

It surely would be nice to standardize, wouldn't it?

I would not care which unit we standardized on, but I tend to use the unit associated with the nation in WWII since that is what is generally quoted in any specifications from the time period. As long as you can convert, it doesn't matter.

 

[Juha]

Hello Greg, thanks for the zip!

Juha

 

[GregP]

You are welcome. Might come in useful in a bizarre set of circumstances.

If you own one, you usually just follow the book!

 

[kool kitty89]

I would say that a bubble canopy has to 'bubble out' i.e; the lower edges of it relative to the pilots P.O.V positions must give at least some more downwards 'over the side' visibility when they move their head and neck to one side - in the 86 (not the Toyota 'Hachiroku' but the Sabre..) and certaily the F-14 from memory the lower edge of the canopy where it is mounted in the canopy frame rails, is inside the widest portion of the canopy which 'bubble out'-wards. You could say the original Zero-sen had a 1st operationally in service bubble top (in looks) /or a Malcolm hooded Spit.

The F2A was flying and in service before the A6M, and while not as aesthetically similar to the typical 'bubble' configuration as the Zero, the Buffalo may have had better all-around visibility. (even ignoring the belly glazing on the F2A) Without the telescopic sight, the F2A also has some of the better forward visibility of WWII fighters as well. (very broad canopy, heavily ribbed but not 'caged' ) Part of that was, of course, due to the bulky fuselage on the Buffalo, such that even if the canopy was no wider than the fuselage sides, it was still wider than the canopy of the slimmer A6M.

The Gladiator's canopy also very much resembles the 'bubble' configuration and has little framing at that, but in practical terms the biplane wing configuration restricts vision a good deal more. (the same canopy applied to the F.5/34 is a more compelling example, but then so would some He 112 variants)

And on a slightly more relevant note, I'd imagine the B.239's cockpit visibility was one of the more notable advantages the aircraft gave experienced Finnish pilots during the continuation war.

But like the usage of the term 'bike' by both bicycle, motorbike motorcycle users to be 'their' understanding of the word, so to does bubble canopy have such a wide mixture of peoples intpretations of meanings - I'd say the original descriptive one was the naval or bombers transparency that had a 'blown/bubbled out' aspect to to give improved downwards viewing ability.

There's the 'teardrop' canopy term used at times as well, and the lesser bulging on the P-51D's canopy that put it at a visibility disadvantage to the bulged Malcolm hood configuration.