Discussion about video - "P-51 Mustang vs. Fw 190 D-9"

[tomo pauk]

Greg at 'Greg's Airplanes and Automobiles' made this video comparison between P-51D and Fw 190D-9 back in July.

I find the video very good up until 30-th minute mark, unfortunately some things don't add up, like the 100 oct fuel giving 30 mph speed increase for RAF fighters during the BoB at high altitudes, or that turbo was 1st stage 2nd stage of compression on B-17s or P-47s. The notion of simply adding a second S/C stage to an existing engine is also not right IMO; ditto for referring of the auxiliary stage on 2-stage P&W engines as being 'remotely installed'.
Implying that USA was supplying the British with 100 oct fuel while circumventing their own law? Comparison of P-51A from mid-1943 vs. Spitfire V of mid-1941; no advantage of V-1650-1 vs. V-1710-39??
The best is jet to come - erstwhile Merlin was 'sucking hind tit', and didn't became the great engine until it used American fuel, American carb and American-derived if not designed supercharger?? (about min. 41 of the video)

Or it might be just me being me, the old nitpicker

 

[Deleted member 68059]

Greg at 'Greg's Airplanes and Automobiles' made this video comparison between P-51D and Fw 190D-9 back in July.

I find the video very good up until 30-th minute mark, unfortunately some things don't add up, like the 100 oct fuel giving 30 mph speed increase for RAF fighters during the BoB at high altitudes, or that turbo was 1st stage of compression on B-17s or P-47s. The notion of simply adding a second S/C stage to an existing engine is also not right IMO; ditto for referring of the auxiliary stage on 2-stage P&W engines as being 'remotely installed'.
Implying that USA was supplying the British with 100 oct fuel while circumventing their own law? Comparison of P-51A from mid-1943 vs. Spitfire V of mid-1941; no advantage of V-1650-1 vs. V-1710-39??
The best is jet to come - erstwhile Merlin was 'sucking hind tit', and didn't became the great engine until it used American fuel, American carb and American-derived if not designed supercharger?? (about min. 41 of the video)

Or it might be just me being me, the old nitpicker

Nope yout not nitpicking, its filled with gigantic factual errors, huge leaps of faith - absurd assumptions and wishful thinking. All disguised by good presentation and entertaining delivery together with a healthy sprinkling of truth cookies to distract the viewer.

Describing the Merlin-61 supercharger as: "US derived if not designed dual-stage supercharging" is literally insane. 41:55

You might as well call the Corsair "Effectively invented by the British because the gull-wing was stolen by the Americans from the Supermarine Type 224" - which would
also be totally untrue and basically insane to imply.

 

[GrauGeist]

I was just reading about "How the Junkers Ju87 influenced the design of the Curtiss A-8" and while the bit was presented well, the glaring error was that the A-8 was being flown several years before the Ju87 was even put to paper...

I don't think that these people are intentionally spreading misinformation, but instead have an idea of something and run with it without taking the time to research their subject.

 

[davparlr]

... unfortunately some things don't add up, like the 100 oct fuel giving 30 mph speed increase for RAF fighters during the BoB at high altitudes ...

I don't know about the 30 mph stuff but I had read somewhere that the Germans were surprised by the performance of the spitfire until one was downed in occupied territory and an analysis of the fuel revealed it was 100 octane.,

or that turbo was 1st stage of compression on B-17s or P-47s. The notion of simply adding a second S/C stage to an existing engine is also not right IMO; ditto for referring of the auxiliary stage on 2-stage P&W engines as being 'remotely installed'.

I'm not sure of your question here. Certainly the P-47 had a single speed, single stage engine mounted supercharger which was in turn fed by a second supercharger powered by exhaust (turbo-supercharger) mounted remotely behind the pilot. I suspect the P-38 was the same. Don't know about the B-17/24. It is true that a two stage two speed PW R-1830 was delivered for F4F-3 in early 1939. Whether this impacted RR on their engine I don't know. Relations between British and American weapons manufacturing during this period of time probably warrants a doctoral thesis.

Implying that USA was supplying the British with 100 oct fuel while circumventing their own law?

Apparently, 100 octane fuel manufactured in various places was being supplied to GB in 1939. I have read that Spitfires were not upgraded to 100 octane until March, 1940. It is not hard to believe Roosevelt was capable of circumventing laws, although I did read that some shipments were held up.

 

[tomo pauk]

I don't know about the 30 mph stuff but I had read somewhere that the Germans were surprised by the performance of the spitfire until one was downed in occupied territory and an analysis of the fuel revealed it was 100 octane.,

Spitfire was a far more streamlined machine than Bf 109E, let alone than Hurricane, and Merlin III have had a better altitude performance than DB 601A; a good turn of speed can be expected.
We can take a look at speed figures achieved on boost up to +6.25 psi (= 87 oct minimum), SPitfire I was good for 360+ mph by the time ww2 started. 100 oct fuel helped zilch above ~16500 ft. link

I'm not sure of your question here. Certainly the P-47 had a single speed, single stage engine mounted supercharger which was in turn fed by a second supercharger powered by exhaust (turbo-supercharger) mounted remotely behind the pilot. I suspect the P-38 was the same. Don't know about the B-17/24. It is true that a two stage two speed PW R-1830 was delivered for F4F-3 in early 1939. Whether this impacted RR on their engine I don't. Relations between British and American weapons manufacturing during this period of time probably warrants a doctoral thesis.

I've made a mistake there - Greg notes the turbo as being second stage, not the 1st stage I've wrote. (corrected now)
RR (and anyone else) knew about advantages of more than one stage of supercharging, since there were well-published altitude records achieved by aircraft powered by Bristol and Junkers engines with 2 stage S/C in 1936 or so - well before P&W made their 2-stage S/Cs. There was also the French suggestion for an single shaft 2-stage S/C published in 1938. Trick was getting the 2-stage superchargers packaging to be compact enough for use in fighters of the day, while getting acceptable reliability.

 

[davparlr]

I've made a mistake there - Greg notes the turbo as being second stage, not the 1st stage I've wrote. (corrected now)
RR (and anyone else) knew about advantages of more than one stage of supercharging, since there were well-published altitude records achieved by aircraft powered by Bristol and Junkers engines with 2 stage S/C in 1936 or so - well before P&W made their 2-stage S/Cs. There was also the French suggestion for an single shaft 2-stage S/C published in 1938. Trick was getting the 2-stage superchargers packaging to be compact enough for use in fighters of the day, while getting acceptable reliability.

It does seem to be intuitively obvious.

 

[RCAFson]

100 Octane fuel allowed for Merlin III 12lb boost at ~10K ft, and gave about a 30mph increase at that altitude. Approval of 12lb boost was given in Nov 1939:

http://www.wwiiaircraftperformance.org/hurricane/hurricane-12lbs-14nov39.jpg

above 10K ft, boost levels would decrease steadily and at ~18K ft would decline to 6lb of boost which was the rated 87 octane boost for the engine.

 

[tomo pauk]

100 Octane fuel allowed for Merlin III 12lb boost at ~10K ft, and gave about a 30mph increase at that altitude. Approval of 12lb boost was given in Nov 1939:
http://www.wwiiaircraftperformance.org/hurricane/hurricane-12lbs-14nov39.jpg
above 10K ft, boost levels would decrease steadily and at ~18K ft would decline to 6lb of boost which was the rated 87 octane boost for the engine.

Nobody disputed that 100 oct fuel enabled a lot of power at lower altitudes, with corresponding increase of speed. What put me off was the claim that 100 oct fuel enabled extra 30 mph at higher altitudes.

 

[Deleted member 68059]

Nobody disputed that 100 oct fuel enabled a lot of power at lower altitudes, with corresponding increase of speed. What put me off was the claim that 100 oct fuel enabled extra 30 mph at higher altitudes.

Higher octane cannot provide ANY increase in speed above rated altitude, to be fair he just says "higher" without specifiying what that was. However, I think its at best misleading.

 

[RCAFson]

Nobody disputed that 100 oct fuel enabled a lot of power at lower altitudes, with corresponding increase of speed. What put me off was the claim that 100 oct fuel enabled extra 30 mph at higher altitudes.

Yes, I was refuting the claim of high altitude speed increases.

 

[RCAFson]

Apparently, 100 octane fuel manufactured in various places was being supplied to GB in 1939. I have read that Spitfires were not upgraded to 100 octane until March, 1940. It is not hard to believe Roosevelt was capable of circumventing laws, although I did read that some shipments were held up.

Fighter Command had approval to use 100 octane fuel in Sept 1938:

http://www.wwiiaircraftperformance.org/100-octane/24sept38-spitfire-100oct-approval.jpg

 

[pbehn]

Apparently, 100 octane fuel manufactured in various places was being supplied to GB in 1939. I have read that Spitfires were not upgraded to 100 octane until March, 1940. It is not hard to believe Roosevelt was capable of circumventing laws, although I did read that some shipments were held up.

All part of the drift from peace to war,I vaguely recall something about charging an extra $1 per barrel, by the end of 1940 the USA and UK were in discussions to harmonise what 100 Octane actually meant.

 

[davparlr]

Fighter Command had approval to use 100 octane fuel in Sept 1938:

http://www.wwiiaircraftperformance.org/100-octane/24sept38-spitfire-100oct-approval.jpg

This document, page two initial paragraph, refutes your referenced document. I would guess that the first documents authorizes the use of 100 octane, the latter document references the implementation of the use of 100 octane.
http://www.wwiiaircraftperformance.org/100-octane/banks-fuel.pdf

 

[davparlr]

One more comment. While the author compares the P-51D, with racks, to the Fw 190D-9, which is reasonable because the P-51 most likely got to the battle area with drop tanks, an airframe to airframe comparison i.e., clean wings, 5 to 10 mph would have to be added to the P-51 speeds.

 

[RCAFson]

This document, page two initial paragraph, refutes your referenced document. I would guess that the first documents authorizes the use of 100 octane, the latter document references the implementation of the use of 100 octane.
http://www.wwiiaircraftperformance.org/100-octane/banks-fuel.pdf

No, not really. IIRC, there are documented examples of 100 octane use at the squadron level in 1939 and this shows it's use in Feb 1940:

http://www.wwiiaircraftperformance.org/hurricane/111-15feb40-100-octane.jpg

and it seems that the change over was a gradual affair rather than an abrupt transition.

 

[Shortround6]

A possible source of confusion on the "american" 100 octane fuel is that any fuel coming from the western hemisphere was sometimes referred to as coming from the "Americas" with the "S". The British were getting a lot of their 100 octane fuel from the west indies (Trinidad-Tobago) and not from United States of America refineries in 1939-40-41.

US Military standard 100 octane fuel of 1939-40 might not have allowed quite the amount of boost that British 100 octane did in 1940. They did not come up with a common fuel specification until after the BoB.

 

[Mike Williams]

A possible source of confusion on the "american" 100 octane fuel is that any fuel coming from the western hemisphere was sometimes referred to as coming from the "Americas" with the "S". The British were getting a lot of their 100 octane fuel from the west indies (Trinidad-Tobago) and not from United States of America refineries in 1939-40-41.

US Military standard 100 octane fuel of 1939-40 might not have allowed quite the amount of boost that British 100 octane did in 1940. They did not come up with a common fuel specification until after the BoB.

Fwiw, also see: Trimpell Oil Refinery

 

[Mike Williams]

One more comment. While the author compares the P-51D, with racks, to the Fw 190D-9, which is reasonable because the P-51 most likely got to the battle area with drop tanks, an airframe to airframe comparison i.e., clean wings, 5 to 10 mph would have to be added to the P-51 speeds.

I didn't see the article in question so can't speak directly to that, however, alternatively deduct for as delivered service condition Fw 190 D-9s about 5-6 mph as equipped with ETC 504 tank rack and fixed wheel covering; and another ~9 mph without engine compartment sealing. FW 190 D-9 Flight Trials

 

[Koopernic]

I don't know about the 30 mph stuff but I had read somewhere that the Germans were surprised by the performance of the spitfire until one was downed in occupied territory and an analysis of the fuel revealed it was 100 octane.,
SNIP

Apparently, 100 octane fuel manufactured in various places was being supplied to GB in 1939. I have read that Spitfires were not upgraded to 100 octane until March, 1940. It is not hard to believe Roosevelt was capable of circumventing laws, although I did read that some shipments were held up.

The British fuel was 100/130 octane (RON 100 in stoichiometric air: fuel (14.2:1) or lean rating, Performance Number in Rich Mixture Rating 130%) The 130% means 30% more power as established in a test engine when the engine was rich in a variable compression test engine. I'm not sure what the 'rich' ratio was. I think about 12:1. All that excess fuel was just discharged and wasted in the exhaust.

130% means ore engine power but obviously not more aircraft speed. Climb rate would tend to increase 30%.

This was all the Britishers own work. It became viable after the development of acid alkylation at BP.

The 100 octane fuel used in the US has a different, much earlier, origin that was also 100% American work. It was a 100 octane lean rating with no particularly strong specification for or test to establish rich mixture performance. (there must have been something but it wasn't much and there almost certainly wasn't a performance number based system or test). The Americans were interested in sustained performance and range.

The USAAC began insisting it would only buy 100 octane fuel even if it paid 4-5 times the price. This was a way around seeking congressional fuding but it had the effect of the US oil industry investing in the production of iso-butylene (the feedstock for iso-octane) and catalytic cracking.

Roosevelts "neutrality patrols" had the US Navy escorting British Supply Convoy's over half way across the Atlantic and attacking u-boats.. That was 5 1/2 months before WW2.

However it was not US fuel that came into use in Britain, they made their own, though the RAF had started experimenting with American 100 grade fuel in the late 1930s.

The infrastructure developed for producing 100 grade US aviation gasoline leant itself well to production to the 100/130 grade RAF spec.

 

[Mike Williams]

A possible source of confusion on the "american" 100 octane fuel is that any fuel coming from the western hemisphere was sometimes referred to as coming from the "Americas" with the "S". The British were getting a lot of their 100 octane fuel from the west indies (Trinidad-Tobago) and not from United States of America refineries in 1939-40-41.

To your point:
Dutch West Indies - Leo McKinstry, Hurricane, Victor of the Battle of Britain, (John Murrey Publishers, London, 2010), p. 87.
Aruba & Trinidad- Bill Gunston, Rolls-Royce Aero Engines, (Patrick Stephens Limited, 1989). p. 72.