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

[eagledad]

Wuzak,

You are correct, I did mis-understand what you had written. However, in the process I learned something new about the Spitfire Mk IX!

Thanks!

Eagledad

 

[Denniss]

A 5/43 range report probably of a british-captured Bf 109G-2 trop:

 

[P-39 Expert]

Hello P-39 Expert,
What you are stating isn't really accurate.
The FW 190A through the A-7 and even early A-8 series had two fuel tanks as standard.
The Forward Tank was 233 Liters (61,5 USG)
The Middle Tank was 292 Liters (77.1 USG)
The Aft Fuselage Tank which was optional on some models became standard during the A-8 production run and added 115 Liters (33.3 USG).

So.... Early models would have had 138.69 Gallons and Late models would have had 169 Gallons of internal fuel.

Note also that the FW 190 series could carry a lot of external stores or fuel which the Airacobra could not.

- Ivan.

P-39 held more internal fuel than FW190 RELATIVE TO THE DISPLACEMENT/OUTPUT of the engine.

Two planes each hold 150gal, one has a 2000hp engine and one has a 1000hp engine. The 1000hp plane holds more fuel.

 

[P-39 Expert]

You guys are much sharper than I on these two aircraft. My question is how did they stack up or compare range wise. I'm assuming the radial had a higher gallon per mile covered or greater fuel burn than the inline (V12) of the P39?

Cheers,
Biff

The FW190 (clean) endurance was about 1.4hr at high cruise and 2.1hr at low cruise after reserves.

P-39 (clean 120 gal) per manual endurance was about 1.3hr at high cruise and 2.6hr at low cruise at 20k' after reserves (16gal).

 

[Ivan1GFP]

P-39 held more internal fuel than FW190 RELATIVE TO THE DISPLACEMENT/OUTPUT of the engine.

Two planes each hold 150gal, one has a 2000hp engine and one has a 1000hp engine. The 1000hp plane holds more fuel.

Hello P-39 Expert,
I believe you are using a rather contrived measurement that is pretty meaningless.

If you want to play with the numbers, then you should look at the early FW 190A that only had about 1450 HP and a late model Airacobra that had about the same amount of power.
How about a comparison between the Daimler Benz DB 605 versus the Merlin or the Allison V-1710?
The power outputs were fairly similar but the DB605 has a lot less supercharger and a lot more displacement.

Here's a good question: When the comparing the FW 190A to the FW 190D, which had more fuel?
The actual fuel volumes are identical, but the inline has more power even though it has less displacement.

This is why I believe your assertion does not hold up well.

- Ivan.

 

[Milosh]

The FW190 (clean) endurance was about 1.4hr at high cruise and 2.1hr at low cruise after reserves.

P-39 (clean 120 gal) per manual endurance was about 1.3hr at high cruise and 2.6hr at low cruise at 20k' after reserves (16gal).

Depends on what altitude.
Fw190A-8
1.2hr @ 0.3km @ 2300rpm @ 1.2ata @ 515kph
2.1hr @ 0.3km @ 2000rpm @1.05ata @ 440kph

1.48hr @ 7.0km @ 2300rpm @ 1.2ata @ 580kph
2.18hr @7.0km @ 2000rpm @ 1.05ata @ 495kph

 

[Ivan1GFP]

Depends on what altitude.
Fw190A-8
1.2hr @ 0.3km @ 2300rpm @ 1.2ata @ 515kph
2.1hr @ 0.3km @ 2000rpm @1.05ata @ 440kph

1.48hr @ 7.0km @ 2300rpm @ 1.2ata @ 580kph
2.18hr @7.0km @ 2000rpm @ 1.05ata @ 495kph

I wonder how much this changes when each is carrying maximum external tanks.
I believe the P-39 could carry at most one external tank and the FW 190 could carry three.

- Ivan.

 

[Milosh]

with 300litre drop tank
3.24hr @ 0.3km @ 2000rpm @ 1.05ata @ 415kph
3.1hr @ 5.0km @ 2000rpm @ 1.05ata @ 485kph

 

[Ivan1GFP]

with 300litre drop tank
3.24hr @ 0.3km @ 2000rpm @ 1.05ata @ 415kph
3.1hr @ 5.0km @ 2000rpm @ 1.05ata @ 485kph

I wonder how far it would go with either two or three drop tanks.
This critter is carrying 2 x 300 liter tanks but the center position could also carry a tank instead of the 250 Kg bomb that is here.

 

[Denniss]

3 d/t was unlikely unless they had some extra oil reservoir installed somewhere

 

[P-39 Expert]

I wonder how much this changes when each is carrying maximum external tanks.
I believe the P-39 could carry at most one external tank and the FW 190 could carry three.

- Ivan.

P-39 could carry various tanks up to 175gal (660litres) on its center line giving 6.7hr at low cruise of 41gph and 3.3hr at high cruise of 82gph at 20000'. At high cruise at 25000' it was good for 4.4hr. After reserve for takeoff.

 

[fubar57]

Documentation.....?

 

[P-39 Expert]

Hello P-39 Expert,
I believe you are using a rather contrived measurement that is pretty meaningless.

If you want to play with the numbers, then you should look at the early FW 190A that only had about 1450 HP and a late model Airacobra that had about the same amount of power.
How about a comparison between the Daimler Benz DB 605 versus the Merlin or the Allison V-1710?
The power outputs were fairly similar but the DB605 has a lot less supercharger and a lot more displacement.

Here's a good question: When the comparing the FW 190A to the FW 190D, which had more fuel?
The actual fuel volumes are identical, but the inline has more power even though it has less displacement.

This is why I believe your assertion does not hold up well.

- Ivan.

How else can you compare fuel load on different aircraft with vastly different engines? Why would you compare an early FW190 (1941) with a late model P-39 (mid '44) when one has 2600CID and one has 1710? One has 1700HP and one has 1150/1325/1200hp depending on model?

 

[Shortround6]

Simply compare actual range/radius at a given speed/altitude. And then ignore anything much under a 20% difference (arbitrary) as useful for winning bar bets but pretty much useless for figuring out operational differences.

Using ferry tanks makes for a mildly interesting number but is useless for figuring out operational capabilities. Hurricanes could carry a pair of 44 imp gallon drop tanks for combat but could carry a pair of 90 imp gallon tanks for ferrying. Trying to use them means you can get a Hurricane much deeper into enemy territory than it can get out if drops the tanks with fuel in them.

Comparing peak or max HP is also a rather false assumption to compare fuel capacity to. as most of the time such power/fuel consumption was only used for a small percentage of the flight.

 

[Reluctant Poster]

Was looking for a Spitfire IX data sheet and found this - fuselage tank mods for a long range IX
http://www.spitfireperformance.com/spitfire9-fuelsystem-lr.jpg

I think the date is 1945, but I can't tell for sure.

The standard IX had 85 imperial gallons, which is 102 USG. Which is less than the 120USG that some P-39s had, but more than most P-39s had (87USG).

This long range Spitfire had 96 UKG forward of the pilot and 66 or 74UKG behind the pilot, depending if it had the standard or cut down rear fuselage.

MK VIIIs had 96 UKG forward tanks as standard and 13 UKG in each wing, for a total of 122UKG. This carried over to the XIV.

I'm not sure if IXs ever got the leading edge tanks. I suspect not.

In any case, it appears that the Spitfire had more space where fuel could be added, even if that could cause stability issues (eg rear tanks).

The Mark XIV reverted to 85 imp gallons forward of the pilot. This was due to the relocation of the oil tank from under the engine to in front of the pilot.
According to Spitfire by Morgan and Shacklady, late model Mark IXs had two 18 imp gallon Mareng bags in the wings.

 

[wuzak]

The Mark XIV reverted to 85 imp gallons forward of the pilot. This was due to the relocation of the oil tank from under the engine to in front of the pilot.
According to Spitfire by Morgan and Shacklady, late model Mark IXs had two 18 imp gallon Mareng bags in the wings.

Thanks RP.

 

[tomo pauk]

How else can you compare fuel load on different aircraft with vastly different engines? Why would you compare an early FW190 (1941) with a late model P-39 (mid '44) when one has 2600CID and one has 1710? One has 1700HP and one has 1150/1325/1200hp depending on model?

I really wonder when people will stop posting bogus figures on this fine forum.
Fw 190 from 1941 have had 1600 HP engine, that power being limited to 3 minutes. P-39 from mid-1944 have had 1420 HP (5 min limit). Talking about cubic inches is meaningless, it is thrust (enabled by power + prop combination, plus exhaust thrust) what propells aircraft, not cubic inches.

 

[Ivan1GFP]

3 d/t was unlikely unless they had some extra oil reservoir installed somewhere

Very good point!

How else can you compare fuel load on different aircraft with vastly different engines? Why would you compare an early FW190 (1941) with a late model P-39 (mid '44) when one has 2600CID and one has 1710? One has 1700HP and one has 1150/1325/1200hp depending on model?

Just use the actual volumes. That is pretty hard to dispute.

If you really want to play with some numbers, how about comparing a fairly early (1942) P-39D-2 or P-39K with a V-1710-63 engine?
At low altitude, those engines were putting out well over 1500 HP on War Emergency power which isn't that different from a contemporary FW 190A....

When you start comparing engine designs, there are a lot more characteristics that affect things than simple displacement and power output.
Factor in manifold pressure and RPM and things even out a bit but of course there are consequences to those choices.

- Ivan.

 

[Kevin J]

Very good point!



Just use the actual volumes. That is pretty hard to dispute.

If you really want to play with some numbers, how about comparing a fairly early (1942) P-39D-2 or P-39K with a V-1710-63 engine?
At low altitude, those engines were putting out well over 1500 HP on War Emergency power which isn't that different from a contemporary FW 190A....

When you start comparing engine designs, there are a lot more characteristics that affect things than simple displacement and power output.
Factor in manifold pressure and RPM and things even out a bit but of course there are consequences to those choices.

- Ivan.

I thought war emergency only became available on the P-39K or did the Russians get there earlier on the D-2?

 

[Greyman]

With no automatic boost control - are manifold pressures limited (to a certain extent) only by the throttle discipline of the pilot?