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

[drgondog]

View: https://www.youtube.com/watch?v=sTD7DqXfRno

He sez he will talk about Drag later but somehow misses comparing the speed of the Bf 109 to the Spit IX with essentialy same engines as Packard 1650-7 in the P-51D. Or compare the 109G-6 at 1450PS at 22K vs P-47D-10 with 2320HP at 22K and 56"MP for 410mph TAS? Did he not get the memo that the primary differences were not engine power, but Drag?

Somehow with his reputation for deep dive into the arcane, he really doesn't seem to know that the relationship between PS rating and HP rating is 0.986:1. He focused on MP gap as the 'ah hah'.

Further he postulates that P-51D was 6o mph faster than Bf 109G-6, trying to found the discussion on delivered HP based on MP derived from 150 octane fuel when the primary difference was Parasite Drag of P-51B/D was that it had 40% less than Bf 109G.

A little research on Fluid Dynamic Drag would have revealed Sighard Hoerner, PhD devoting nearly a complete chapter (14) on Drag Analysis of a Fighter Airplane, with a deep dive on the Bf 109G.

Greg missed the memo on the 1650-3 to 1650-7 kits - he stated that kits converted -7 to -3, just the reverse as Every P-51B/C/D Mustang were equipped with -3 until approximately April/May 1944 when NAA switched over to -7 and delivered only in -7 from that point forward. Additionally The P-51Ds (and late block B/Cs) arriving at BAD2 from late June had the -7. 44-1 150 octane was approved for 8th AF in June, for 2 TAF in August, for 9th AF November. By that time the -10 and the 109G-6 AS were in play as well as emerging G-14 operating at 1.7ata with MW-30 and MW-50.

Last but not least - 1650-3/-7 HP=f (altitude, MP, gear ratio) for the 1650-3 and -7 and that the Mustang was Not always delivering even 20mph more speed than say 109G-6 and 109G-6AS, or climb, when extenal bomb racks were attached (always) on the P-51B/D. Further, it was a Rare occassion when the P-51B/D actually engaged a 109 at 25-30000 feet. The chase may have began near bomber altitudes but quickly devolved to mid-altitudes down to the deck - which was the judgment of AAF and the reason for the 1650-7 being preferred in ETO.

 

[Jabberwocky]

Some data to add to the discussion:

109G speeds from official reports obtained via Kurfurt's 109 site

109G-1 (seems like an early test example): 660 kph at 7000m with 1230 PS from DB 605 at 2600 rpm
109G-1 (serial production example): 622 kph at 6000m with DB 605 E at 2500 rpm at 1.3 ata
514 kph at 0m with DB 605 E at 2500 rpm
109G-1 (serial production example): 626 kph at 6100m with DB 605 A at 2600 rpm at 1.3 ata
507 kph at 0m with DB 605 A at 2600 rpm
109G-1 (serial production example, mid 1942): 649 kph at 7000m with DB 605 A
109G-1: 660 kph at 7000m with DB 605 A
109G-1 (Finnish tests): 636 kph at 6300 with 1310 PS from DB 605 A at 2540 rpm (aircraft was estimated at capable of 652 kph, but appears to be slightly damaged and under-performing)
109G-2 Tropical (RAF testing): 384 mph/618 kph at 23,000 ft/7000m with DB 605 at 2800 rpm and 1.42 ata
109G-2 (RAF estimate): 395 mph/636 kph at 22,000 ft/6700m with DB 605 at 2800 rpm and 1.42 ata
109G-2: 652 kph (average of 13 serial production aircraft from the Erla factory in mid 1943)
109G-2 (Soviet tests): 666 kph at 7000m with DB 605 A/1 (reported as giving 1310 hp at 5800m)

109G-5: 654 kph at 8300m with DB 605 AS
109G-6: 652 kph at 5400m with 1355 PS from DB 605 A at 1.42

Bf 109G-14: 665 kph at 5000m with 1700 PS from DB 605 AM engine, at 1.7ata with MW-30 injection
Bf 109G-14/U4: 668 kph at 7500m with 1800 PS from DB 605 ASM engine, at 1.7ata with MW-50 injection

640-660 kph (398-410 mph) seems to be a pretty good average for a clean 109G-2 or 109G-6 when the P-51B/C started to see ETO service (December 1943 unless I'm not recalling correctly?).

 

[pbehn]

You made me watch another one!!!!!!!!!!!!!!!!!!

The whole reason behind watching these videos is to be told to watch more of them where he will explain more, count the times he says that. That is a long fishermans yarn, which implies that the Bf 109 would have been much better if only an expert from 2023 set up the supercharger. Watching the video, and using its information why wouldnt a P-40 with Merlin engines be just as effective as a P-51?

As I understood things the reason the P-51B?C D were faster than the Spitfire with the same engine was that P-51s all around better aerodynamics, but this includes the Spitfire having cannon which was a deliberate choice. The two stage Merlin allowed the Spit to have parity not huge superiority with the Bf 109 and Fw 190 which both had more swept volume. I would therefore expect the P-51 to have 20-30 MPH advantage over a Bf 109. The rambling style gives me again the impression that he is misrepresenting something, and he is.

 

[Timppa]

Sighard F. Hörner did say that G6 could fly 800km/h (500 mph for you muricans) if everything was perfect and if pigs could fly (in theory).

 

[drgondog]

Sighard F. Hörner did say that G6 could fly 800km/h (500 mph for you muricans) if everything was perfect and if pigs could fly (in theory).

Timppa - where could I find the Hoerner reference to the conditions of the 109G-6 a well as powerplant? I could see that in a terminal 1g dive, but not in even a special DB603 with MW-50 at 1. ata.

 

[drgondog]

You made me watch another one!!!!!!!!!!!!!!!!!!

The whole reason behind watching these videos is to be told to watch more of them where he will explain more, count the times he says that. That is a long fishermans yarn, which implies that the Bf 109 would have been much better if only an expert from 2023 set up the supercharger. Watching the video, and using its information why wouldnt a P-40 with Merlin engines be just as effective as a P-51?

As I understood things the reason the P-51B?C D were faster than the Spitfire with the same engine was that P-51s all around better aerodynamics, but this includes the Spitfire having cannon which was a deliberate choice. The two stage Merlin allowed the Spit to have parity not huge superiority with the Bf 109 and Fw 190 which both had more swept volume. I would therefore expect the P-51 to have 20-30 MPH advantage over a Bf 109. The rambling style gives me again the impression that he is misrepresenting something, and he is.

The P-51B/D at 67" at best altitude (FTH =24K for -7 and 29K for -3) for P-51 has a decided avantage in top speed of ~ 60mph (-3 at 32K) without Racks - which didn't happen in combat. The P-51B/D with improved racks with -7 at 67" FTH at 24K had about a 35-40mph advantage.

For 109G-6 with DB603AS at FTH of 27K was at a 35+mph disadvantage at 27K, a 35mph disadvantage at 24K, a 40mph disadvantage at 20K, a 45mph disadvantage at 16K and a 40mph disadvantage at 4K.

Your point about P-40 is dead on. From flt test of F, with racks, 1100 Hp for 1650-1 - the P-40F tested at 374mph. Bf 109G-6 at same altitude at ~ 385mph. The P-51D-15 at 2400RPM, 42", 1100 Hp travelled ~ 390mph The first two above at combat settigs, the P-51D in fast cruise below max continous power just below 46" Max continuous HP.

and the Spit was faster at all altitudes than the 109G-6 but significantly less margin compared to P-51B/D with wing racks.

I honestly don't believe Greg is 'misrepresenting' consciously, only misunderstanding that the factual basis of the engine/MP disussion was NOT the dominant factor in the speed disparities.

 

[Vincenzo]

Jabberwocky i think that your 601A actually are 605A

 

[tomo pauk]

Timppa - where could I find the Hoerner reference to the conditions of the 109G-6 a well as powerplant? I could see that in a terminal 1g dive, but not in even a special DB603 with MW-50 at 1. ata.

For 109G-6 with DB603AS at FTH of 27K was at a 35+mph disadvantage at 27K, a 35mph disadvantage at 24K, a 40mph disadvantage at 20K, a 45mph disadvantage at 16K and a 40mph disadvantage at 4K.

Bill - no DB 603 for the Bf 109...

 

[Jabberwocky]

Jabberwocky i think that your 601A actually are 605A

Yes, thanks. Slip of the keyboard.

Corrected.

 

[pbehn]

The P-51B/D at 67" at best altitude (FTH =24K for -7 and 29K for -3) for P-51 has a decided avantage in top speed of ~ 60mph (-3 at 32K) without Racks - which didn't happen in combat. The P-51B/D with improved racks with -7 at 67" FTH at 24K had about a 35-40mph advantage.

For 109G-6 with DB603AS at FTH of 27K was at a 35+mph disadvantage at 27K, a 35mph disadvantage at 24K, a 40mph disadvantage at 20K, a 45mph disadvantage at 16K and a 40mph disadvantage at 4K.

Your point about P-40 is dead on. From flt test of F, with racks, 1100 Hp for 1650-1 - the P-40F tested at 374mph. Bf 109G-6 at same altitude at ~ 385mph. The P-51D-15 at 2400RPM, 42", 1100 Hp travelled ~ 390mph The first two above at combat settigs, the P-51D in fast cruise below max continous power just below 46" Max continuous HP.

and the Spit was faster at all altitudes than the 109G-6 but significantly less margin compared to P-51B/D with wing racks.

I honestly don't believe Greg is 'misrepresenting' consciously, only misunderstanding that the factual basis of the engine/MP disussion was NOT the dominant factor in the speed disparities.

Thanks drgondog, I was speaking in general terms about the Spit when introduced, its engines boost pressures were changed with boost pressures etc but this brings me to the first issue I have, what are you talking about Greg and why. He chooses to compare the G-6 to the P-51D... why? As he says later (as you do) the different fuels and systems used on the Bf 109 changed the game but its complicated. So we will compare a US fighter introduced in mid 1944 to a German fighter introduced in early 1943. He is comparing the power outputs but never states them once. How about a graph of both engines showing the power output growth from first running to end of hostilities, showing how different fuels/boost levels supercharger systems changed things. How about a graph comparison of the speeds at different altitudes of the P-51B D and the various Bf 109s after the G6 was introduced?

Then we come to flag waving nonsense. Throughout the video he refers to the Merlin as an American engine, it doesnt use the method of other Amrican engines for two stage supercharging "probably because of its British origins". This isnt serious discussion, the project to make a high altitude engine for a Wellington bomber considered using a turbo but this was rejected because it wouldnt fit easily in a S/E fighter, nothing to do with "British" at all. He says that there was no room under the cowl for a two stage supercharger!!! Well maybe he should watch the movie Battle of Britain because the planes representing the LW have just that, Bf 109s with Merlins called a Buchon. When discussing the -7 and -3 versions he says The P-51s designers could tailor the engine to suit the altitude, he even describes the Merlins two stage supercharger as "The P-51 system" I have the greatest of respect for NAA but they didnt design the freakin engine. He says "it was clear to the Mustangs designers that it would have to escort US bombers" really? I have a book on that subject, it wasnt clear to the Mustangs designers that it would be an escort until 1943. The Bf 109 had an "incredible" drive system but no such compliment is given to the P-51s engine. etc etc etc

But towards the end all is revealed. He is actually addressing the gaming sim community. He says that if you operate WEP for five minutes then after you have to let the aftercooler cool down, since there isnt a temperature gauge leave it for a minute or two and it should be OK. This is pure invention, planes without aftercoolers have WEP limits, it is to do with "stuff" above my pay grade like build up of thermal loads and breakdown in lubrication caused by the temperature and pressure on the oil film in bearings etc. The Merlin had both and intercooler and an aftercooler. He goes on to say "if you have to fight" in the present tense, it is sim stuff not actually history at all.

 

[Deleted member 68059]

View: https://www.youtube.com/watch?v=sTD7DqXfRno

He sez he will talk about Drag later but somehow misses comparing the speed of the Bf 109 to the Spit IX with essentialy same engines as Packard 1650-7 in the P-51D. Or compare the 109G-6 at 1450PS at 22K vs P-47D-10 with 2320HP at 22K and 56"MP for 410mph TAS? Did he not get the memo that the primary differences were not engine power, but Drag?

Somehow with his reputation for deep dive into the arcane, he really doesn't seem to know that the relationship between PS rating and HP rating is 0.986:1. He focused on MP gap as the 'ah hah'.

Further he postulates that P-51D was 6o mph faster than Bf 109G-6, trying to found the discussion on delivered HP based on MP derived from 150 octane fuel when the primary difference was Parasite Drag of P-51B/D was that it had 40% less than Bf 109G.

A little research on Fluid Dynamic Drag would have revealed Sighard Hoerner, PhD devoting nearly a complete chapter (14) on Drag Analysis of a Fighter Airplane, with a deep dive on the Bf 109G.

Greg missed the memo on the 1650-3 to 1650-7 kits - he stated that kits converted -7 to -3, just the reverse as Every P-51B/C/D Mustang were equipped with -3 until approximately April/May 1944 when NAA switched over to -7 and delivered only in -7 from that point forward. Additionally The P-51Ds (and late block B/Cs) arriving at BAD2 from late June had the -7. 44-1 150 octane was approved for 8th AF in June, for 2 TAF in August, for 9th AF November. By that time the -10 and the 109G-6 AS were in play as well as emerging G-14 operating at 1.7ata with MW-30 and MW-50.

Last but not least - 1650-3/-7 HP=f (altitude, MP, gear ratio) for the 1650-3 and -7 and that the Mustang was Not always delivering even 20mph more speed than say 109G-6 and 109G-6AS, or climb, when extenal bomb racks were attached (always) on the P-51B/D. Further, it was a Rare occassion when the P-51B/D actually engaged a 109 at 25-30000 feet. The chase may have began near bomber altitudes but quickly devolved to mid-altitudes down to the deck - which was the judgment of AAF and the reason for the 1650-7 being preferred in ETO.

The 109G, especially in terms of the version "as built" (wartime conditions etc) had pretty workmanlike aerodynamics in terms of drag,
all the carbuncles to suit armament changes and so on really took their toll.

So much faster was the P-51 with so little fuel used that at one RLM conference, when Milch was discussing the war
situation, was asked about how to combat the P-51, Milch gave up. "The mustang is in another class" he simply
responded, and the discussion returned to the minutia of the day.

Messerschmitt were desperate to employ the laminar wing technology as soon as possible (which Greg says doesn't work),
and so designed a new 109 with laminar flow wings. It was never employed because Messerschmitt had decided to use
a very high wing loading (his main philosophy for fighters) and so to achieve reasonable landing and take off runs
you needed slats. Once the Germans tested the Laminar wings, they found the little bump where the slat met the
wing when it was retracted was enough to ruin the flow advantage and so the new 109 had a wing 30% bigger
in area than the old wing (so that it had a lower wing loading and didn't need slats). The production change
this needed was judged to be so detrimental to high factory output that the project was canned.

The Germans were amazed by the P-51 wing, their aerodynamics experts declared they were stunned how
far back the flow remained attached.

 

[GregP]

Thanks drgondog, I was speaking in general terms about the Spit when introduced, its engines boost pressures were changed with boost pressures etc but this brings me to the first issue I have, what are you talking about Greg and why. He chooses to compare the G-6 to the P-51D... why? As he says later (as you do) the different fuels and systems used on the Bf 109 changed the game but its complicated. So we will compare a US fighter introduced in mid 1944 to a German fighter introduced in early 1943. He is comparing the power outputs but never states them once. How about a graph of both engines showing the power output growth from first running to end of hostilities, showing how different fuels/boost levels supercharger systems changed things. How about a graph comparison of the speeds at different altitudes of the P-51B D and the various Bf 109s after the G6 was introduced?

Then we come to flag waving nonsense. Throughout the video he refers to the Merlin as an American engine, it doesnt use the method of other Amrican engines for two stage supercharging "probably because of its British origins". This isnt serious discussion, the project to make a high altitude engine for a Wellington bomber considered using a turbo but this was rejected because it wouldnt fit easily in a S/E fighter, nothing to do with "British" at all. He says that there was no room under the cowl for a two stage supercharger!!! Well maybe he should watch the movie Battle of Britain because the planes representing the LW have just that, Bf 109s with Merlin two stage engines called a Buchon. When discussing the -7 and -3 versions he says The P-51s designers could tailor the engine to suit the altitude, he even describes the Merlins two stage supercharger as "The P-51 system" I have the greatest of respect for NAA but they didnt design the freakin engine. He says "it was clear to the Mustangs designers that it would have to escort US bombers" really? I have a book on that subject, it wasnt clear to the Mustangs designers that it would be an escort until 1943. The Bf 109 had an "incredible" drive system but no such compliment is given to the P-51s engine. etc etc etc

But towards the end all is revealed. He is actually addressing the gaming sim community. He says that if you operate WEP for five minutes then after you have to let the aftercooler cool down, since there isnt a temperature gauge leave it for a minute or two and it should be OK. This is pure invention, planes without aftercoolers have WEP limits, it is to do with "stuff" above my pay grade like build up of thermal loads and breakdown in lubrication caused by the temperature and pressure on the oil film in bearings etc. The Merlin had both and intercooler and an aftercooler. He goes on to say "if you have to fight" in the present tense, it is sim stuff not actually history at all.

The Buchons in the Battle of Britain had single-stage Merlin 500-45s originally. Those are single-stage engines.

The Buchon at the Planes of Fame has a Merlin 224 in it, which is a Merlin 24 (single-stage built by Packard).

I have seen maybe 3 - 4 of them and have yet to see a 2-stage engine in one of them.

 

[Shortround6]

Both the Buchons and Spanish He 111s had the equivalent of a Merlin XX. At the end of the war and for quite a while post war RR was offering T-24s and Merlin 500s for commercial service, either for transports or for fighters/fighter trainers. Like the Fiat G.59. The transport series engines were rated at the same power as the Military twenty series engines but were beefed up in certain areas for longer life. The two stage engines were the 600 series.
You not only need the supercharger, you need the intercooler and you need the intercooler radiator somewhere in the airflow.

"The Merlin had both and intercooler and an aftercooler."

It did and it didn't.

The big box is the after cooler and it did most of the work. The "intercooler" were a few water passages that the air flowed over between the 1st and 2nd stage.

They did something and maybe Calum has some figures on how effective they were but I would guess not very (could be very wrong, P-38s used the leading edge of the wing going both ways and it didn't work well)

 

[SaparotRob]

It must've been asked before but did LW Bf-109 experten ever get to fly Buchons post war and comment on them?

 

[pbehn]

Both the Buchons and Spanish He 111s had the equivalent of a Merlin XX. At the end of the war and for quite a while post war RR was offering T-24s and Merlin 500s for commercial service, either for transports or for fighters/fighter trainers. Like the Fiat G.59. The transport series engines were rated at the same power as the Military twenty series engines but were beefed up in certain areas for longer life. The two stage engines were the 600 series.
You not only need the supercharger, you need the intercooler and you need the intercooler radiator somewhere in the airflow.

"The Merlin had both and intercooler and an aftercooler."

It did and it didn't.
View attachment 716204

The big box is the after cooler and it did most of the work. The "intercooler" were a few water passages that the air flowed over between the 1st and 2nd stage.
View attachment 716205

They did something and maybe Calum has some figures on how effective they were but I would guess not very (could be very wrong, P-38s used the leading edge of the wing going both ways and it didn't work well)

Thanks I edited it, but the point remains the same. He says a two stage supercharger wont fit under the cowl. Well a Griffon doesnt fit under the cowl of a Spitfire Mk I either. You dont design an aircraft by taking a cowl and seeing what will fit under it. It may be true that it would be too big, probably more tru that the effort needed wouldnt be worth it, but that isnt what he says. Did they have one to know it wouldnt fit?

 

[GregP]

Both the Buchons and Spanish He 111s had the equivalent of a Merlin XX. At the end of the war and for quite a while post war RR was offering T-24s and Merlin 500s for commercial service, either for transports or for fighters/fighter trainers. Like the Fiat G.59. The transport series engines were rated at the same power as the Military twenty series engines but were beefed up in certain areas for longer life. The two stage engines were the 600 series.
You not only need the supercharger, you need the intercooler and you need the intercooler radiator somewhere in the airflow.

"The Merlin had both and intercooler and an aftercooler."

It did and it didn't.
View attachment 716204

The big box is the after cooler and it did most of the work. The "intercooler" were a few water passages that the air flowed over between the 1st and 2nd stage.
View attachment 716205

They did something and maybe Calum has some figures on how effective they were but I would guess not very (could be very wrong, P-38s used the leading edge of the wing going both ways and it didn't work well)

The P-38 intercooler in the leading edge worked just fine, but was only good to remove the heat from 1,000 hp. If you used more power (very possible), the temp would rise until you reduced below 1,000 hp of heat flow or it blew, whichever came first. The beard radiators in the J and L model were to get more heat removal from the intercooler and more radiator core area. They worked.

 

[GregP]

It must've been asked before but did LW Bf-109 experten ever get to fly Buchons post war and comment on them?

Not too sure about the experten, but there have been many commentaries on the Buchon. Most say it was OK when flown off grass, but vicious off pavement. Although it climbed very well, almost nobody liked the way it flew and handled. The Spanish DID finally put a decent canopy on the Bf 109 / Ha.1112! Check out the cockpit canopy below.

 

[Timppa]

Timppa - where could I find the Hoerner reference to the conditions of the 109G-6 a well as powerplant? I could see that in a terminal 1g dive, but not in even a special DB603 with MW-50 at 1. ata.

14-7:

 

[PAT303]

RAE 1501 its surprising how much the quality of the finish effect's the speed.

 

[Juha3]

Some data to add to the discussion:

109G speeds from official reports obtained via Kurfurt's 109 site

109G-1 (seems like an early test example): 660 kph at 7000m with 1230 PS from DB 605 at 2600 rpm
109G-1 (serial production example): 622 kph at 6000m with DB 605 E at 2500 rpm at 1.3 ata
514 kph at 0m with DB 605 E at 2500 rpm
109G-1 (serial production example): 626 kph at 6100m with DB 605 A at 2600 rpm at 1.3 ata
507 kph at 0m with DB 605 A at 2600 rpm
109G-1 (serial production example, mid 1942): 649 kph at 7000m with DB 605 A
109G-1: 660 kph at 7000m with DB 605 A
109G-1 (Finnish tests): 636 kph at 6300 with 1310 PS from DB 605 A at 2540 rpm (aircraft was estimated at capable of 652 kph, but appears to be slightly damaged and under-performing)
109G-2 Tropical (RAF testing): 384 mph/618 kph at 23,000 ft/7000m with DB 605 at 2800 rpm and 1.42 ata
109G-2 (RAF estimate): 395 mph/636 kph at 22,000 ft/6700m with DB 605 at 2800 rpm and 1.42 ata
109G-2: 652 kph (average of 13 serial production aircraft from the Erla factory in mid 1943)
109G-2 (Soviet tests): 666 kph at 7000m with DB 605 A/1 (reported as giving 1310 hp at 5800m)

109G-5: 654 kph at 8300m with DB 605 AS
109G-6: 652 kph at 5400m with 1355 PS from DB 605 A at 1.42

Bf 109G-14: 665 kph at 5000m with 1700 PS from DB 605 AM engine, at 1.7ata with MW-30 injection
Bf 109G-14/U4: 668 kph at 7500m with 1800 PS from DB 605 ASM engine, at 1.7ata with MW-50 injection

640-660 kph (398-410 mph) seems to be a pretty good average for a clean 109G-2 or 109G-6 when the P-51B/C started to see ETO service (December 1943 unless I'm not recalling correctly?).

There was nothing wrong with the Finnish AF MT-215, BTW a Bf 109G-2, during the tests, problem is Kurfürst, the 636 km/h is with the compressibility correction, without it the max speed was 652 km/h, so it shows that the Messerschmitt figures were without the compressibility correction.