Bf-109 vs Spitfire vs Fw-190 vs P-51

[claidemore]

Mustang IVs were cleared for 25 lb boost, 1940 HP, as were the Mustang IIIs, they both used the same 1650-7 engine.

On 18 September 1944 ADGB noted, that with respect to the Mustang III/Packard Merlin 1650-7, "A total of over 7,000 hours have been flown at a maximum boost pressure of + 25 lbs./sq. in.". 25 The RAF's Mustang Pilot's Notes gives the Combat Engine Limitation as "81 ins. boost for 5 minutes when using 150 grade fuel". 26 Combat Reports show +25 lbs was used operationally over the continent by UK based Mustangs of ADBG

Also, 65 Squadron combat report with Mustang IV using 70 inches.
http://www.wwiiaircraftperformance.o...n-5april45.jpg

[Soren]

The Mustang III's boosted that much were used for V1 hunting IIRC and did not encounter any enemy fighters. And as for P-51D's, well AFAIK only one was tested running at +25 lbs/sq.in. boost, and with a RR engine.

[ponsford]

Originally Posted by Soren

Those are no P-51D's ponsford, those are Mustang Mk.III's.

Nope, not all of them are for Mustang III. That Pilots Notes scan/copy/photo is shown as from Air 10/2873 of the National Archives which a quick search shows it to be is listed as follows: "Pilot's Notes for Mustang IV Packard Merlin 1650-7 Engine". Anyway, the thread is titled "Bf-109 vs Spitfire vs Fw-190 vs P-51". I didn't see any qualifier excluding the Mustang III. But so what if they were all Mustang III (they weren’t and the RAF did operate Mustang IV’s)? That doesn’t change the fact that the RAF had operational Mustangs employing +25 lbs boost with BHP of 1940 BHP.

[ponsford]

Originally Posted by Soren

The Mustang III's boosted that much were used for V1 hunting IIRC and did not encounter any enemy fighters. And as for P-51D's, well AFAIK only one was tested running at +25 lbs/sq.in. boost, and with a RR engine.

Nope, wrong again. You must not have read those previous links. Read this one again:

http://www.wwiiaircraftperformance.o...-23march45.jpg

F/Lt. G.M. Davis of 129 Squadron flying a Mustang III S.W. of Bremen "opened up to +25 lbs. of boost 3,000 revs and dived down to engage" ... an Me 262.

[Soren]

Again, a Mustang III not a P-51D.

The P-51D is the version listed and thus the one we will be comparing first.

But we know that the P-51D ran at 75" MAP, which gave around 1,830 HP.

[bada]

can check in the polish book "skies in fire" from bogdan arct, a polish pilot that flew in the 145/PFT and was squadron leader of the 316 in the mustang3 period.
His poney3 (a replacement airframe, hated by all the pilots )had a gizmo and his engine stopped above germany ...he talks about the poney3, he liked it very much because of it's great performance and explain some things about it (a bit like clostermann).So, the admission pressure should be cited.(the 316 beeing a "normal" squadron, the poneys3 should be "standard" with max performance allowable for fighter sweeps above ennemy teritory. )

[Kurfürst]

Originally Posted by ponsford

That doesn’t change the fact that the RAF had operational Mustangs employing +25 lbs boost with BHP of 1940 BHP.

Question is, how many of them? I understand two RAF Mustang III Squadrons used 150 grade fuel in conjunction with +25 lbs boost in the anti-diver campaign.

And though Mike tries to push their operations in the summer of 1944 as if V-1 hunting was something of a passtime when they had nothing better to do, a little research reveals that something like 95% of their sorties in the summer were anti-diver operations (I have the exact number of sorties somewhere), while Mike has been quoting those two missions which belong to that 5%.. again its the sort of typical manipulation Mike has a reputation for.

I am rather sceptical about that +25 lbs saw any sort of meaningful scale outside the anti-diver campaign. That a dozen or two planes were specially boosted for a special task hardly justifies a comparison of them against widely used standard types.

OTOH, there`s no doubt the USAAF had used widely in the 8th FC the moderate 72" boost pressure with 150 grade, although spark plug fouling caused considerable trouble as I understand.

[ponsford]

I don’t know which is more peculiar, that rant or the numbers machinations/games employed to dismiss/deflect/obfuscate the performance comparisons of operational aircraft. It isn’t even a requirement that they be operational as far as I'm concerned, it’s all interesting. V-1’s or some grudge is all quite irrelevant to the linked report showing +25 lbs employed by Mustangs over Germany. Again for those without some odd agenda and with an interest in learning check: http://www.wwiiaircraftperformance.o...-23march45.jpg Case closed as far as I’m concerned.

[Soren]

The only one who seems to have an agenda is you Ponsford, you undoubtedly come from some gaming forum with that attitude of yours.

[drgondog]

Originally Posted by Soren

Bada,

Thanks but I already have it.

Bill,

We can also do it with full fuselage tank but that would be abit unfair I think seeing that the pilots were adviced to empty this first so as to correct the CG. We can also simulate the 40% reduction of fuel load at the time period you mention.

By comparison it wasn't uncommon for German fighters to take off with half fuel tanks, fuel being in desperate demand.

You might have misunderstood my point - it was almost unheard of for German Gighters to engage either B's or D's before they crossed the Channel as they were flying toward R/V for target Escort.. all or most of the fuse tank would be burned first, then external, then internal in that order. In that circumstance (for example Munich, they woul have burned fuse, external and be into internal fuel. Just TO, forming up, climbing to altitude and getting to the coast would take most of the fuselage tank - which did have the 85 gallon capacity but SOP for Europe was fill only 65 .. at 25 Gal the cg was back in acceptable limits

Worst case for either the B or D would be empty fuse tank, full external and full internal wing tanks (184 gallons) - punch external immediately - that could be for example crossing the Dutch or Danish Coast.

Average for the battles in eastern Germany would be using internal fuel near Central Germany

[drgondog]

Originally Posted by Soren

Ofcourse HP means nothing without knowing prop efficiency, but the speeds of the a/c compared to the overall drag give a very good idea of this.

.

The problem with having a very good idea about Thrust is that just to obtain the value you have to back it out by matching the level flight max speed at specific altitudes Hp, blower settings then calculate the Drag by adding the Cdwet to Induced drag using the equations - thereby creating a load balance.

Ok - that is good for one altitude, level flight, one RPM, One Boost and trimmed for level flight..

For high angle of attack situations, propellers lose a certain percentage of efficiency.. Turns would be an example of that. It would be different for different a/c and honestly I don't know the difference between the typical three paddle blade common for the 109 and 190 and the 11' four blade Hamilton Standard.

For every altitude and power setting you can solve for thrust, but you have to solve for it. I'm researching my textbooks to see if I can find enough about propeller theory to shed light on efficencies as a function of AoA from the Thrust Line, and whether or not it corresponds to AoA of the wing-body in a linear way.

So, an accurate baseline CDwet for each aircraft has to be established. Lednicer's Report has the figures for 190A-8 and 190d-9 and Spit IX and 51B and D - are those the ones we will use?

Second, which set of Speed versus altitude, Per Hp/Boost condition charts are going to be the common view?

I would propose to use one rpm and boost for all the altitudes to simplify the math and comparisons? and assume that the propeller efficiencies as a funtion of AoA be ignored.

But we need to decide the altitudes to drive the Thrust calculations results, need to have the set of Hp to altitude charts to agree that comparisons in the 'saw tooth context' and note the gross weight of the a/c in the tests above the empty weight..

I am ok to use the USAAF flight test results on both the P-51B and P-51D instead of Manufacturer but if the results, for example, used for German a/c by manufacturer are not aligned with LW Test results we will have a question as to accuracy..

[drgondog]

Originally Posted by Soren

Again, a Mustang III not a P-51D.

The P-51D is the version listed and thus the one we will be comparing first.

But we know that the P-51D ran at 75" MAP, which gave around 1,830 HP.

Remembering the P-51D was inferior in performance to the B/C because of the extra weight and that B/C's still comprised 25+% of the P-51 inventory in January, 1945..

And that the Hp is for one altitude only.

And we must calculate individual thrust for all the a/c in this comparison at the specific altitudes we agree to look at?

[Kurfürst]

Originally Posted by ponsford

I don’t know which is more peculiar, that rant or the numbers machinations/games employed to dismiss/deflect/obfuscate the performance comparisons of operational aircraft. It isn’t even a requirement that they be operational as far as I'm concerned, it’s all interesting.

I am not sure I am getting it all right - we are comparing operational aircraft, but for some aircraft, unlike the others, it isn`t a requiirement that they would be operational in any meaningful numbers...

Anyway, I have a simply questions, since this is all interesting as well: How many Mustang Squadrons in the RAF, and how many operating at +25 lbs...?

Funny, but I am asking this question for years, and while appearantly there is a lot of info emerging about boosted P-38s, P-47s, P-51s in the USAAF, there is absolutely nothing emerging about the wide scale use of 150 grade in the RAF, which Mike and Neil is claimig for years. Odd isn`t it, they dig the British National Archieves for years, and can`t seem to find anything on it... well perhaps they are looking for something that doesn`t exist but in their wishful thinking.

V-1’s or some grudge is all quite irrelevant to the linked report showing +25 lbs employed by Mustangs over Germany.

.. and similiarly, a single or two boosted Mustang Squadrons doing occasional missions over Germany and otherwise stationed in Britain for anti-diver duties is all quite irrevelant to the big picture, and typical engagements.

[mad_max]

Use the USAF Merlin at 72 damn inches then. Sheeze cut the BS about what Mike and Neal say. I'm so tired of all the bad mouthing a few folks do about others when I see each has their own agendas.

We still don't have any numbers of the "supposed" usage of 1.98 ata 109K. Can't be more than a couple Brit squads flying at 25 inches you say. So using that train of thought then we can't use that version of the 109 then either.

So use 72" with the Merlin and the 605 with 1.80 ata. See that was easy yes?

[Kurfürst]

Originally Posted by mad_max

We still don't have any numbers of the "supposed" usage of 1.98 ata 109K.

Supposed...?

I believe we have seen the transcript of the order that clears 1,98ata for four Luftwaffe fighter wings in March 1945, for what... 3+ years..?

OKL, Lw.-Führüngstab, Nr. 937/45 gKdos.(op) 20.03.45

No. Unit Present type Convert to Notes
1. III./ JG 1 Bf 109 G-10 He 162 (April/May) -
2. II. / JG Bf 109 G-10 K-4 when deliveries permit -
3. III. / JG 3 Bf 109 K-4 no change -
4. III. / JG 4 Bf 109 K-4 no change -
5. IV. / JG 4 Bf 109 K-4 K-4 -
6. III. / JG 5 Bf 109 G-14 K-4 when deliveries permit -
7. IV. / JG 5 Bf 109 G-14 K-4 when deliveries permit -
8. III. / JG 6 Bf 109 G-14/AS K-4 when deliveries permit -
9. II. / JG 11 Bf 109 G-10 K-4 when deliveries permit -
10. I. / JG 27 Bf 109 K-4 no change boost increase to 1.98 ata
11. II. / JG 27 Bf 109 G-10 K-4 when deliveries permit -
12. III. / JG 27 Bf 109 G-10 no change boost increase to 1.98 ata
13. I. / JG 51 Bf 109 G-14 K-4 when deliveries permit -
14. III. / JG 51 Bf 109 G-14 K-4 when deliveries permit -
15. IV. / JG 51 Bf 109 G-14 K-4 when deliveries permit -
16. II. / JG 52 Bf 109 G-14/U4 K-4 when deliveries permit -
17. III. / JG 52 Bf 109 G-14 K-4 when deliveries permit -
18. II. / JG 53 Bf 109 K-4 no change -
19. III. / JG 53 Bf 109 K-4 no change boost increase to 1.98 ata
20. IV. / JG 53 Bf 109 K-4 no change boost increase to 1.98 ata
21. I. / JG 77 Bf 109 G-14/U4 K-4 when deliveries permit -
22. II. / JG 77 Bf 109 G-10 K-4 when deliveries permit -
23. III. / JG 77 Bf 109 G-10 K-4 when deliveries permit -
24. III. / JG 300 Bf 109 G-10/R6 via K-4 to Me 262 planned, deadline
25. IV. / JG 300 Bf 109 G-10/R6 via K-4 to Me 262 -
26. I. / KG(J) 6 Bf 109 G-10/R6 K-4/R6 when deliveries permit -
27. II. / KG(J) 6 Bf 109 K-4 K-4/R6 when deliveries permit -
30. I. / KG(J) 27 Bf 109 G-10/R6 K-4/R6 when deliveries permit -
31. I. / KG(J) 55 Bf 109 G-10/R6 - -
32. II. / KG(J) 55 Bf 109 K-4 - to industrial defense
33. Ist Italian FG Bf 109 G-10 K-4 when deliveries permit -
34. IInd Italian FG Bf 109 G-10 K-4 when deliveries permit -
35. IIIrd Italian FG Bf 109 G-10 K-4 when deliveries permit -

That some like to pretend the order does not exist is not my problem..

As I have said I hava absolutely no doubt the 72" boost was used on a wide scale in the USAAF for Mustang (8th AAF Mustang Groups, I believe 15th AAF was 67", as it received 100 octane only).