Greg strikes again - Bf 109G-6 was so slow compared to P-51D

[Engineman]

Many yrs. ago i read Heinz Knokes book, where he stated in a passage that his Me109g was becoming very sluggish, he blamed it on all the crap being hung on the airframe and the "bulges" all over the fuselage. The R4M rockets on the wings seemed to draw his ire as a major drag issue. I think some pilots nicknamed the aircraft "the bulge"

So, bear in mind that Knoke is partly commenting on the "Gunboat" Bf 109 G aircraft that were principally trying to kill bombers. The underwing Gondola cannons were not liked for their extra weight and drag. Likewise, the BR21 rocket projectile was very draggy, even after firing the rocket.
Most of the later Bf 109 G aircraft were also operated with the 300l external tank, so the overall aircraft was very heavy at T/O.
R4M rockets were a less draggy installation, seen mostly on Me 262.
Late Bf 109 G and K types did get more power from late Spring 1944 onwards.

Eng

 

[PAT303]

In ww2 , from late 1941 , Germany s fighters were badly outperformed by the western fighters.

Any allied fighter pilot crossing the channel in 1941 would have to be alert and have his head on a pivot if he wanted to survive.

 

[pbehn]

Any allied fighter pilot crossing the channel in 1941 would have to be alert and have his head on a pivot if he wanted to survive.

It can be answered in one word, Dieppe.

 

[Deleted member 68059]

 

[pbehn]

View attachment 717055
View attachment 717056

View attachment 717057

Written almost exactly one month before Dieppe.

 

[Mike Williams]

Most of the later Bf 109 G aircraft were also operated with the 300l external tank, so the overall aircraft was very heavy at T/O.

Eng

Yes, and just like the P-51, the 109's external tank rack remained after the tank's release, contributing to drag. Of course, this should be taken into account when doing comparisons.

 

[Shortround6]

Any allied fighter pilot crossing the channel in 1941 would have to be alert and have his head on a pivot if he wanted to survive.

It can be answered in one word, Dieppe. 19 August 1942

Now I may be guilty of confusing the time scale but weren't the Germans having trouble with the 109G and the FW 190 in the summer of 1942?
Not being able to use the full intended boost?

The Germans stumbled several times with the intended engine/aircraft development schedule and since the British were trying to guess what the Germans were doing, or where they were intending to go, while trying to figure out where the British should go with research and production you can wind up with confusion. British could not depend on the German planning going wrong (DB 605 stuck with 1.30 boost for months)

The Merlin and the DB 605 get the benefit of "sprint" ratings. Very useful in a fighter for combat, not very useful for a bomber.

 

[tomo pauk]

Now I may be guilty of confusing the time scale but weren't the Germans having trouble with the 109G and the FW 190 in the summer of 1942?
Not being able to use the full intended boost?

The Germans stumbled several times with the intended engine/aircraft development schedule and since the British were trying to guess what the Germans were doing, or where they were intending to go, while trying to figure out where the British should go with research and production you can wind up with confusion. British could not depend on the German planning going wrong (DB 605 stuck with 1.30 boost for months)

Problem was, from the British point of view, that even with reduced settings on their engines, both Fw 190 and Bf 109G were much better performers than the Spitfire V.

The Merlin and the DB 605 get the benefit of "sprint" ratings. Very useful in a fighter for combat, not very useful for a bomber.

DB 605 received the 'sprint' rating much later than it was the case with BMW 801.
A bomber outfitted with Merlin or DB 605 will benefit a lot vs. a bomber outfitted with BMW 801: smaller installed weight, lower drag, much better fuel mileage - so the starting design can be smaller and much lighter, and with better airfield abilities. Comparison between Mosquito and A-20 might be of use here.

 

[Shortround6]

both Fw 190 and Bf 109G were much better performers than the Spitfire V.

British may have been a bit late upgrading the boost ratings of the Merlin 45.
At some point in 1941 they went from 9lb to 12lbs and in Jan 1942 they went to 15lbs, at least on paper.
Test reports dated March/April of 1942 have the planes being tested at 9lbs of boost.
Tests were being done on Squadron planes at 16lbs of boost in 30th June 1942 and at test at Boscombe down from July through Sept (report Nov 1942)

Spitfire Mk V AA.878 Report

Awful long time to go from 15lbs of boost to 16lbs????
They were still looking at cooling issues.

Not saying that would fix things but it would have made things a bit closer.

A bomber outfitted with Merlin or DB 605 will benefit a lot vs. a bomber outfitted with BMW 801: smaller installed weight, lower drag, much better fuel mileage - so the starting design can be smaller and much lighter, and with better airfield abilities. Comparison between Mosquito and A-20 might be of use here.

It does and it doesn't.
The A-20 was stuck with the original engines for pretty much the duration of the war. Once they got the R-2600s they stayed with the 1600hp version all the way to the last of J's in 1944 when they got just about the same engines the B-25 was using since 1941.

Now the 1600hp R-2600 was good for 1400hp at 11,500 ft at military rating (it never got a WEP rating) and yes it is larger and heavier than a Merlin, however it was also good for 1275hp at 12,000ft max continuous. It was thirsty but you could run it at that power level as long as the fuel held out and the engine stayed within temperature limit.
It would also give 1350hp at 5,000ft in low gear.
Having an extra 150-225hp per engine can make a difference in climb to a heavily loaded bomber.
You want to compare to the Mosquito use an early Mosquito with Merlin 21s and the boost limit from early 1942.
For the Germans imagine trying to swap BMW 801s for DB 605s on a Do 217.

 

[pbehn]

Now I may be guilty of confusing the time scale but weren't the Germans having trouble with the 109G and the FW 190 in the summer of 1942?
Not being able to use the full intended boost?

The Germans stumbled several times with the intended engine/aircraft development schedule and since the British were trying to guess what the Germans were doing, or where they were intending to go, while trying to figure out where the British should go with research and production you can wind up with confusion. British could not depend on the German planning going wrong (DB 605 stuck with 1.30 boost for months)

The Merlin and the DB 605 get the benefit of "sprint" ratings. Very useful in a fighter for combat, not very useful for a bomber.

Without discussing all the ins and outs of boost pressures, the RAF took a hammering at Dieppe. However the Spit Mk IX and Mustang I were there, which showed things were changing.

 

[tomo pauk]

British may have been a bit late upgrading the boost ratings of the Merlin 45.
At some point in 1941 they went from 9lb to 12lbs and in Jan 1942 they went to 15lbs, at least on paper.
Test reports dated March/April of 1942 have the planes being tested at 9lbs of boost.
Tests were being done on Squadron planes at 16lbs of boost in 30th June 1942 and at test at Boscombe down from July through Sept (report Nov 1942)
Spitfire Mk V AA.878 Report
Awful long time to go from 15lbs of boost to 16lbs????
They were still looking at cooling issues.

Not saying that would fix things but it would have made things a bit closer.

We both know that increased boost at lower altitudes (5-10 kft for the Spitfire V) does nothing for fighters' performance at high altitudes (above 15000 ft, let alone above 20000 ft).

It does and it doesn't.
The A-20 was stuck with the original engines for pretty much the duration of the war. Once they got the R-2600s they stayed with the 1600hp version all the way to the last of J's in 1944 when they got just about the same engines the B-25 was using since 1941.

Now the 1600hp R-2600 was good for 1400hp at 11,500 ft at military rating (it never got a WEP rating) and yes it is larger and heavier than a Merlin, however it was also good for 1275hp at 12,000ft max continuous. It was thirsty but you could run it at that power level as long as the fuel held out and the engine stayed within temperature limit.
It would also give 1350hp at 5,000ft in low gear.
Having an extra 150-225hp per engine can make a difference in climb to a heavily loaded bomber.
You want to compare to the Mosquito use an early Mosquito with Merlin 21s and the boost limit from early 1942.

(my bold)
Even with such limits, Mosquito ends up as better of the two.

For the Germans imagine trying to swap BMW 801s for DB 605s on a Do 217.

Do 217 does not fill in this category:

so the starting design can be smaller and much lighter

IOW, it already started as a big and heavy A/C.

 

[Shortround6]

We both know that increased boost at lower altitudes (5-10 kft for the Spitfire V) does nothing for fighters' performance at high altitudes (above 15000 ft, let alone above 20000 ft).

True but the FW 190 wasn't exactly a ball of fire over 20,000ft either. An extra 12-20mph at lower altitudes for the Spitfire V may have helped things out while waiting for the Spitfire IX.

Even with such limits, Mosquito ends up as better of the two.

Perhaps not by as much as you think
The A-20 could not maneuver as well and you could have quite a bit if difference just in paint on both planes.
One test of an A-20 in 1941 (running light) had it doing 333mph at 5000ft, most service planes were slower.

Do 217 does not fill in this category:

Only in sense that when comparing radials to in-lines the difference between WEP and military power and max climb can be rather different.
To pick on the Americans, the R-2800 in the P-47 went from 2000hp to 2500-2600hp with new turbos and water injection.
The MAX continuous rating (climb or max cruise) stayed the same.
One reason they could not substitute R-2800s for R-3350s in the B-29s no matter what the WEP rating of the R-2800 was.

 

[tomo pauk]

True but the FW 190 wasn't exactly a ball of fire over 20,000ft either. An extra 12-20mph at lower altitudes for the Spitfire V may have helped things out while waiting for the Spitfire IX.

Against anything that was not Bf 109 of the era, and before Spitfire IX arrived, it was a ball of fire. Including the above 20000 ft altitude band. Expecting that enemy will fight at one's favorable altitude band is a surefire way to loose.

Perhaps not by as much as you think
The A-20 could not maneuver as well and you could have quite a bit if difference just in paint on both planes.
One test of an A-20 in 1941 (running light) had it doing 333mph at 5000ft, most service planes were slower.

Difference in range/radius was amazing, Mosquito vs. A-20.

 

[blueskies]

This is a comparison of service quality wings done by the DVL. This represents service condition wings with a somewhat rough surface. Cwp = Cd, Ca = Cl, Cwp M is measured and Cwp id is theoretical ideal.

 

[Deleted member 68059]

This is a comparison of service quality wings done by the DVL. This represents service condition wings with a somewhat rough surface. Cwp = Cd, Ca = Cl, Cwp M is measured and Cwp id is theoretical ideal.
View attachment 717132

Is there a date on that report ? or a UM/FB No. ?

 

[drgondog]

This is a comparison of service quality wings done by the DVL. This represents service condition wings with a somewhat rough surface. Cwp = Cd, Ca = Cl, Cwp M is measured and Cwp id is theoretical ideal.
View attachment 717132

Interesting,

The 0.0072 value for Cdo above is very close to the Drag Build ups value for P-51D wing = 0.0070 at R.N. =2x106^6. Ref.NAA. Report NA-8449 Performance Estimates for Mosel P-51D-5 Airplane.

 

[PAT303]

True but the FW 190 wasn't exactly a ball of fire over 20,000ft either. An extra 12-20mph at lower altitudes for the Spitfire V may have helped things out while waiting for the Spitfire IX.

Until the high boosted LF models arrived there wasn't much you could do to the MkV to get any resemblance of parity to the 190, cleaning up the airframes and clipping the wings might have helped, a change in leadership also.

 

[Clayton Magnet]

bulges for 15mm MG 131

MG 131 was the 13mm machine gun.

 

[Snautzer01]

Indeed 13mm. A typo i am sure.

Mg131 in detail here

 

[drgondog]

Indeed 13mm. A typo i am sure.

Mg131 in detail here

Yep - meant MG 151