DCS: Spitfire Mk LF IXc Discussion

[TwilightZone]

What am I looking at? (What is M/S gear?)

 

 

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Moderate supercharger

[KansasCS]

Ah. Ok :)

Still, the graph is confusing. How do I read it? Was the S gear only used at higher altitudes, I take it? And from which altitude onwards? Or is it overlayed, meaning the boost lines can be imagined as going through the M gear lines, slightly below?

 

Apologies for my reckless lack of knowledge.

 

 

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[TwilightZone]

Ah. Ok :)

Still, the graph is confusing. How do I read it? Was the S gear only used at higher altitudes, I take it? And from which altitude onwards? Or is it overlayed, meaning the boost lines can be imagined as going through the M gear lines, slightly below?

 

Apologies for my reckless lack of knowledge.

 

 

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The impellers were driven by a hydraulically operated two-speed gearbox.[6] At low to medium altitudes, the supercharger was in Moderate Supercharger or M.S. gear (this referred to the gearing and thus the speed, at which the impellers were operating). Once the aircraft reached and climbed through a set critical altitude, (20,000 feet (6,100 m) for the Merlin 61 and 70 series) the power would start to drop as the atmospheric pressure (the density of air) dropped.[7] As the critical altitude was passed a pressure-operated aneroid capsule operated the gearbox, which changed speed to Full Supercharger (F.S.) gear, which drove the impellers faster, thus compressing a greater volume of the air-fuel mixture

[KansasCS]

It's dawning on me. The mustang has a similar system.

 

 

 

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[MiloMorai]

KansasCS take a look at this site to answer most of your questions, http://www.spitfireperformance.com/

 

The P-51B,C,D,K used an American produced (by Packard) Merlin so would be the same.

 

 

As can be seen the coupling from the crankshaft is mechanical

[Friedrich-4B]

Also, I'd like to see concrete Speed/rate of climb over altitude charts.

 

 

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[ame]http://www.spitfireperformance.com/JL165-Rolls-Royce.pdf[/ame]

 

JL165 was built as a Spitfire VC in March 1943, but modified to a Mk IX later in the year.

 

 

http://www.spitfireperformance.com/jl165form78.jpg

 

 

JL165's s performance was slightly lower than usual for an L.F Mk IX.

 

also see:

 

 

http://www.spitfireperformance.com/merlin66_18_25.jpg

 

 

 

http://www.spitfireperformance.com/merlin-comparison.jpg

[KansasCS]

So the speed advantage coming from the higher grade fuel is roughly 23mph in lower altitudes.

Highly substantial.

If it bears truth though that the 150 octane fuel was a rarity among allied forces(as stated by Kurfürst I believe), only used for V1 hunting, why is everyone upset that we aren't getting a 25lbs version?

 

 

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[Decibel dB]

If it bears truth though that the 150 octane fuel was a rarity among allied forces(as stated by Kurfürst I believe), only used for V1 hunting, why is everyone upset that we aren't getting a 25lbs version?

 

 

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As Talisman posting I fail to see it that way

[Decibel dB]

Development of the Rolls-Royce Merlin from 1939 to 1945

 

A Lecture Delivered by Mr. A. C. Lovesey to the de Havilland Aircraft Company Technical Department in November, 1945.

 

http://www.wwiiaircraftperformance.org/merlin-lovesey.pdf

 

Page 223 says:

 

"The first operational use of this fuel was against the flying bombs in the middle of 1944. Subsequently the whole of A.D.G.B. Was put on this fuel. Later it was used by the Second Tactical Air Force during and after the invasion of the Continent."

 

This is evidence to show that the whole of Air Defence Great Britain was using 150 grade fuel, including all its Spitfire Mk IX squadrons, before D-Day.

The Normandy map is due to cover the South of England and the English Channel, as well as France.

A.D.G.B took part in D-Day operations and also flew sorties on the continent.

2nd TAF used 150 grade fuel, including in its Spitfire Mk IX squadrons.

Therefore, I submit that a 25lbs boost Spit Mk IX would not be out of place on the upcoming DCS Normandy Map.

Whether or not we eventually get a 25lbs Spit Mk IX is in the hands of the model developers, but I believe that there is clearly enough evidence to show that it would not be out of place for the WWII project.

 

Happy landings,

 

Talisman

 

^^ Read that Kansas

Edited May 12, 2016 by Decibel dB

[KansasCS]

Indeed, I stand corrected.

 

Further reading on the same site:

Following successful testing, the Spitfire IX's Merlin 66 was cleared in March 1944 to use +25 lbs, obtainable with 150 grade fuel. 36 In early May, No. 1 and No. 165 Squadrons comprising the Predannack Wing, were the first to convert their Spitfires to +25 lbs boost and employ 150 grade fuel on operations. 37 38 Air Defense Great Britain (A.D.G.B.) shared a report, dated 16th June 1944 with A.E.A.F. summarizing the RAF's experience with using 150 Grade Fuel in Merlin 66 engines. All pilots reported most favorably on the value of the high boost pressures obtainable with 150 Grade Fuel, however, Technical Staff felt that before the fuel was introduced on a large scale that the causes of backfires must be established and that at least 12 engines should complete 200 hours each. 39 By the end of July the backfires were overcome through fairly straightforward adjustments. 40 By 12 August 1944, 16 Squadrons in A.D.G.B. had been modified to to operate with 150 grade fuel. 41

The increased performance obtained with 150 Grade Fuel was put to good use by Mustangs, Tempests, Spitfires and Mosquitoes in intercepting V-1 Buzz Bombs launched against Britain beginning mid June. Performance increases at sea level were as follows: 42 43

130 Grade150 Grade Spitfire IX335 mph358 mph +25 lb Spitfire XIV359 mph366 mph +21 lb Tempest V372 mph386 mph +11 lb Mustang III (V-1650-3)360 mph390 mph +25 lb Mosquito NF. Mk. XIX

363 mph +25 lb The Royal Aircraft Establishment (RAE) reported in Technical Note No.Aero.1501(Flight) that a Mustang III (Merlin V-1650-7), flying at +25 lb./sq.in. as received from Squadron, obtained 382 mph at sea level. 44 404 mph was obtained at sea level after "cleaning up" the aircraft by removing the bomb racks and aerial bracket, repainting the wing's leading edge and rubbing down the aircraft. 316 Squadron was one of the Mustang units to convert to 150 grade fuel, their Operations Record Book stating for 1.7.44 "18 A/C test after modification to +25 lbs boost". 45 610 Squadron uprated thier Spitfire XIVs on 14 July, the Operations Record Book stating "A technical party visited the unit to modify the aircraft to fly at 21 lbs boost on 150 octane petrol". 46 These squadrons did more that just chase "divers" as 315 Squadron demonstrated with their Mustangs when they shot down 6 Me 109's, 1 Me 110 and 1 Fw 190 while escorting Beaufighters to Norway on 30 July 1944. 47 85 and 157 Squadrons were two of the Mosquito units operating at +25 lbs boost with 150 grade fuel. 48 49 By mid August the V-1 diver threat was largly eliminated with the advance of the allied armies beyond the launching areas. The ADGB squadrons that had converted to 150 grade fuel now found more time to operate over the continent. The Spitfire IX Squadrons were permanently pulled off anti-diver duty on 10 August and went over completely to escort work, sweeps and armed recces. They paid their first visit to Germany on 27 August 1944. 50 51 316 Squadron flying their Mustangs downed 3 Me 109’s and a Fw 190 five miles N. of Chalom on 14 August. 52 315 Squadron met with remarkable success on 18 August, claiming 16 Fw 190’s shot down near Beauvais with their boosted Mustang III’s (II./JG 26 admitted to 8 killed and 2 wounded). 53 By this time Headquarters, Air Defense of Great Britain required all Packard Merlin V-1650-7 engines in the Mustangs to be modified to operate at 25 lbs. boost. 54 55 56 57 The Spitfire XIV squadrons quickly got into the swing of it with 350 Squadron scoring on 19 August by shooting down a Ju 88 on the outskirts of Brussels. 58 By early September the Spitfire XIV units were engaged in operations over Germany. 59 60 61 62 63

On 18 September 1944 A.D.G.B. very positively summarized the experience gained to date using 100/150 grade fuel. However, due primarily to logistical difficulties, such as the interchange of squadrons between A.D.G.B. and 2nd T.A.F., it was decided that UK based fighter squadrons should revert to the use of 130 grade fuel. 64 Its uncertain as to the degree to which this decision was carried out as of November 1944 Fighter Command was still using 2,000 tons of 150 grade fuel per month. 65 With the adoption of 150 grade fuel by the Second Tactical Air Force, any logistical difficulties to Air Defense of Great Britain (A.D.G.B.) use of 150 grade fuel were removed. By early 1945, United Kingdom based Mustangs of A.D.G.B. were operating at +25 lbs/sq.in/80" hg. with 150 grade fuel on operations over the continent and Germany. 66 67 68 69 Eventually all Rolls-Royce Merlin and Griffon engines were cleared to operate on 150 grade fuel, as well as Centaurus, Hercules, Sabre II and Pratt & Whitney Double Wasp engines. 70

The Second Tactical Air Force Plans were being made in August to supply the 2nd TAF with 150 Grade Fuel. 71 During November 1944 S.H.A.E.F cleared 100/150 grade fuel for use by the Second Tactical Air Force: [...]

 

http://www.wwiiaircraftperformance.org/150grade/150-grade-fuel.html

 

I highlighted the areas Kurfürst might be referring to. He is not wrong that the 150 grade fuel in MkIXs were primarily(moreover initially) used for V1 intercepts; yet they saw broader action over continental Europe later on.

Furthermore, the order to pull mainland based spits from the fuel again was apperently not done extensively.

 

I reckon ED is modelling an 18lbs boost Spitfire, simply because there might be more consistent and detailed data for it. After all, minor changes had to be made to the engine to endure the higher rated fuel(As read in the article, spark plug problems were initially not unheard of).

Bluntly put and as far as I understood the article, modelling a Merlin 66 with 150oct fuel is more complex than simply "making the boost needle hit the 25 and adjusting level speeds". It is a different engine entirely, at least from a sim developers POV.

 

This article reveals something else too, which I noticed in complaints from other threads as well: That the DCS Mustang is literally underrated. But that is a for a different thread.

 

PS: If all this was mentioned in this thread before, I humbly apologize. Also, for the sake of being the nitpickers we apparently are, a second different source on the matter would be good, though at the time of writing this, I haven't found one.

[Ala13_ManOWar]

This article reveals something else too, which I noticed in complaints from other threads as well: That the DCS Mustang is literally underrated. But that is a for a different thread.

Indeed some people asks for a 72 or 75" P-51. But you're missing the Mustang III mentioned in the article is the English version of P-51C, probably with RR engines instead of Packards, so can be seen as completely different aircraft.

 

S!

[KansasCS]

Yes of course :)

my mistake.

[NeilWillis]

Indeed some people asks for a 72 or 75" P-51. But you're missing the Mustang III mentioned in the article is the English version of P-51C, probably with RR engines instead of Packards, so can be seen as completely different aircraft.

 

S!

 

You do realise that the Packard was simply an American made Rolls Royce Merlin engine made under license, and as such, would there be a huge difference?

[Friedrich-4B]

Indeed some people asks for a 72 or 75" P-51. But you're missing the Mustang III mentioned in the article is the English version of P-51C, probably with RR engines instead of Packards, so can be seen as completely different aircraft.

 

S!

 

No, there was no major difference; the Mustang IIIs and IVs mostly used the Packard V-1650-7 (some early IIIs had the -3); the -7s had similar power/altitude ratings to the Merlin 66. (eg :)

 

http://www.wwiiaircraftperformance.org/mustang/rae1501.html

 

4.2 Mustang III (Merlin V-1650-7)

 

Performance measurements were made on Mustang III F.B.377. This aircraft, as received from Squadron [No. 316, Brent], was flying at +25 lb./sq. in. boost, 3,000 r.p.m. The enrichment jet and the balance pipe had not been fitted. These modifications were carried out.

 

The aircraft was a standard mark III type. Bomb racks were fitted under the wings. The whip type aerial was fitted behind the hood and offset to starboard.. The adhesive patches over the gun ports were loose and were replaced by fabric patches before flight. Except for this minor altercation, the aircraft was flown as received.

 

You do realise that the Packard was simply an American made Rolls Royce Merlin engine made under license, and as such, would there be a huge difference?

 

There were some significant differences between the Packard and Rolls-Royce built Merlins; most of these are explained in the attached article. (Courtesy of AEHS http://www.enginehistory.org/ )

Packard as Aero-Engine Builder.pdf

Edited May 12, 2016 by Friedrich-4/B
add article

[Ala13_ManOWar]

You do realise that the Packard was simply an American made Rolls Royce Merlin engine made under license, and as such, would there be a huge difference?

May be not a huge difference, but RR was cleared to 81" boost (25lbs) and Packard was cleared just 72 or 75" as best, isn't it? That's a difference.

 

S!

[Solty]

May be not a huge difference, but RR was cleared to 81" boost (25lbs) and Packard was cleared just 72 or 75" as best, isn't it? That's a difference.

 

S!

 

No, all P-51s were made in the USA with Packard engines. There was no British production.

 

Tell me is the engine that can fly 8h mission without stoping using max continous, military and on some ocasions WEP, come back home, a badly made engine? If what you are saying was true, P-51B/C/D would not be greenlit as the main escort fighter and replace the P-47 Thunderbolt, which was a very good escort fighter with far more reliable engine than any Merlin.

 

My theory is that 81'hg was used by the British because they were not flying as escort for long range missions that often as the USAAF, I would see the reason there. And USAAF wanted to preserve their engine life more, so they were not pushing it to the limit. Very similar thing happened to the Alison engines that were proven to be able to be pushed far beyond their limits, just the limit itself was imposed to be 100% sure nothing will break.

Edited May 12, 2016 by Solty

[Zunzun]

Weren't the USAF mustang in the pacific using 81" when scorting the b-29? I think I red it somewhere.

[Solty]

Weren't the USAF mustang in the pacific using 81" when scorting the b-29? I think I red it somewhere.

I've heard about it, and it is possible. Afterall they were flying way higher than normal where it is even colder and power drops drastically, so it might be possible they were pushing it more to stay with B29s more easily after chasing away the IJA and IJN planes.

Edited May 12, 2016 by Solty

[Ala13_ManOWar]

No, all P-51s were made in the USA with Packard engines. There was no British production.

 

Tell me is the engine that can fly 8h mission without stoping using max continous, military and on some ocasions WEP, come back home, a badly made engine? If what you are saying was true, P-51B/C/D would not be greenlit as the main escort fighter and replace the P-47 Thunderbolt, which was a very good escort fighter with far more reliable engine than any Merlin.

 

My theory is that 81'hg was used by the British because they were not flying as escort for long range missions that often as the USAAF, I would see the reason there. And USAAF wanted to preserve their engine life more, so they were not pushing it to the limit. Very similar thing happened to the Alison engines that were proven to be able to be pushed far beyond their limits, just the limit itself was imposed to be 100% sure nothing will break.

I'm not saying they were faulty at all, did I? What I'm not sure is, weren't 81" cleared engines RR? Like Spitfire was. Everything we have talked, and papers I've seen myself at least, about European USAAF in the other hand was 72 or 75" while 81" was only seen after the war IIRC. So, if cleared to use 81", may be British Mustang III and/or IV used RR engines instead of Packard built? I thought I saw something about it, but really I can't recall for sure right now.

 

S!

[MiloMorai]

British Mustangs had Packard Merlins.

The Royal Air Force received 281 Ds and 594 Ks, designating them Mustang IV and Mustang IVA respectively. The type did not enter RAF service until September 1944, with the earlier Mustang III still remaining in active service.

 

http://www.joebaugher.com/usaf_fighters/p51_10.html

 

and http://www.joebaugher.com/usaf_fighters/p51_11.html

[GrapeJam]

May be not a huge difference, but RR was cleared to 81" boost (25lbs) and Packard was cleared just 72 or 75" as best, isn't it? That's a difference.

 

S!

 

Fun fact, British Mustangs were American made with Packard Merlin engines and were cleared for 25lbs boost.

[Zunzun]

I think Solty's theory quite plausible. That considering the role USAF mustang had to fulfil compared to British ones they preferred more conservative ratings to lengthen engines life.

[saburo_cz]

or they just had different safety limits

like in plane constructions,

for example lightweighted Mustangs P-51F/G

[MiloMorai]

or they just had different safety limits

like in plane constructions,

for example lightweighted Mustangs P-51F/G

 

Why would they, the P-51D,K, delivered to the British have different safety limits?

[Zunzun]

By the time those Pacific mustang were using that settings, war in Europe was over. Maybe at that point they had seen the setting was safe (with the British) so they start using it.

As far as I know the pacific Mustangs were same as Europe ones too.