How much better was the P-51 B/C over the D model?

[drgondog]

From a wrench twister's point of view, adjusting the limit stops, especially if there are factory provided optional settings, is a heck of a lot quicker and easier than changing the mechanical advantage of the linkage. As long as the additional stick travel is not an issue, that's definitely the way to go. If pilots in harm's way are not getting adequate roll response, it's not hard imagining field commands quietly going 15° regardless of factory spec.
When's your publication date?
Cheers,
Wes

Wes - theoretically spring release

 

[grampi]

This maybe of interest to you Grampi. From William Hess's book - Fighting Mustang 1970.

I've seen so many conflicting accounts of P-51s vs whatever the Germans had at the time from our combat pilots then, and guys who fly these planes today, and I can't get over how different their opinions are. These writings seem to claim the P-51 was considerably superior to the 109, and the 51 pilots had a pretty easy time outflying them, but if you listen to some of todays pilots that have flown both, they claim the 109 was superior. They say it would outclimb, outdive, and outturn the 51. I don't know who to believe, but I would tend to believe those who actually flew them in combat situations over today's pilots...

 

[Glider]

Except, when you set out to improve a machine, it's not always clear that your "improved" machine is going to be lacking in some significant way from the original. Often it takes trial by fire to discover these things. A slight deficiency in climb rate, roll rate, or WEP top speed might be less important to an engineer/production manager than to a nugget pilot up against an experten type in a D9.
Cheers,
Wes

If you believe that the average squadron pilot went to the edge of an aircrafts performance then you are sadly mistaken. That ability is one of the factors that sorted the experts from the average. For the vast majority the slight deficiency in a performance factor made no difference at all.

 

[Navalwarrior]

I've seen so many conflicting accounts of P-51s vs whatever the Germans had at the time from our combat pilots then, and guys who fly these planes today, and I can't get over how different their opinions are. These writings seem to claim the P-51 was considerably superior to the 109, and the 51 pilots had a pretty easy time outflying them, but if you listen to some of todays pilots that have flown both, they claim the 109 was superior. They say it would outclimb, outdive, and outturn the 51. I don't know who to believe, but I would tend to believe those who actually flew them in combat situations over today's pilots...

Resp:
I suspect that the individual combat pilot had a greater determining effect than the aircraft they flew. I don't think that today's pilots were flying war weary machines when they formed their opinions/assessments. Timing, weather, position when combat was initiated, etc. likely played major roles. Remember, all that is being discussed is 'history.' Facts and assessments from that time period are often muddled. Keeping things in perspective helps me sleep at night.

 

[Barrett]

Having flown both the C and D, I personally like the D better, but only for a couple reasons. Visibility in the D is insanely better, and, although I obviously didn't fly in combat, I'd rather have 6 guns than 4. The cockpit of the B/C is much more comfortable and and slightly reclined and the trims are much easier to manage. Any power change requires re-trimming the airplane. The D model trim controls are under the larger throttle quadrant and are fiddly to work with if you are used to the B/C. They honestly both fly the same, although Betty Jane liked a few extra miles an hour on landing, probably because of the weight of the rear cockpit. Chris Fahey, at Planes of Fame, dispelled the myth that the wing was fattened to accommodate the upright .50s. He stuck a ruler in the gun bay of the A,C,and D...the measurements were identical. The D model canopy can also be opened in flight whereas the B/C is closed for the duration...it can and will blow off the airplane even at idle if it is opened on the ground...and it takes 3-4 people to get it back on. The B/C is also faster in cruise at the same power settings but that could be negligible at combat weight. The Mustangs I've flown are all far below a fully loaded airplane. Hope this helps.
Jim

Don't recall if I mentioned elsewhere in this thread but Jim's comment about 6 guns v 4 tracks with just about every combat 'stang guy I ever asked. However, comma: I crunched the numbers and found that the D, with 50% more firepower, was only 10% more lethal. That's based on the number of Destroyed credits among Destroyed, Probables and Damaged. For WW II fighters, four .50s looks just about optimum, and it's noteworthy that the FM-2 and F8F reverted to the dash three Wildcat's armament. (The "Wilder Wildcat" scored by far, by far, the highest kill-loss ratio in US history before the F-15, on the order of 30-1. Would have to dig out my stats again.)

 

[pbehn]

Don't recall if I mentioned elsewhere in this thread but Jim's comment about 6 guns v 4 tracks with just about every combat 'stang guy I ever asked. However, comma: I crunched the numbers and found that the D, with 50% more firepower, was only 10% more lethal. That's based on the number of Destroyed credits among Destroyed, Probables and Damaged. For WW II fighters, four .50s looks just about optimum, and it's noteworthy that the FM-2 and F8F reverted to the dash three Wildcat's armament. (The "Wilder Wildcat" scored by far, by far, the highest kill-loss ratio in US history before the F-15, on the order of 30-1. Would have to dig out my stats again.)

Being 10% more lethal just by adding 2 guns and ammunition is a massive return for almost zero investment

 

[XBe02Drvr]

These writings seem to claim the P-51 was considerably superior to the 109, and the 51 pilots had a pretty easy time outflying them, but if you listen to some of todays pilots

You've got to consider the pilots involved. By the time the D Mustang was available in quantity, the average 109 pilot was not as well trained or experienced as the average Mustanger, and was flying a more demanding and tricky machine than his predecessors had. You can't cram more horsepower and weight into a small, and already awkward handling airframe like the 109, without making it even more challenging to operate.
Now jump ahead to the 21st century. The airframes are old and tired (except the new builds), and any one with any sense of responsibility is going to handle them gingerly. Add to that everybody is going to be operating at reduced power settings. 100LL hasn't the antiknock qualities of WWII fighter fuels, although it's closer to what the Germans had than the allies. That said, nobody flying on today's fuel is going to go "through the gate" into WEP in a "friendly" mock dogfight.
Likewise, pilots aren't likely to aggressively explore the G limits of those valuable tired airframes.
So, since the 109s operated on generally less high performance fuels than the 51s back then, and a goodly number of today's 109s are new builds, perhaps they are operating at somewhat less of a handicap than in 1944-45.
Cheers,
Wes

 

[Navalwarrior]

Being 10% more lethal just by adding 2 guns and ammunition is a massive return for almost zero investment

Resp:
I read a post-war US assessment that came to the same conclusion; four guns did the trick. However, it would be hard to envision a 4 gun P-47.

 

[Navalwarrior]

You've got to consider the pilots involved. By the time the D Mustang was available in quantity, the average 109 pilot was not as well trained or experienced as the average Mustanger, and was flying a more demanding and tricky machine than his predecessors had. You can't cram more horsepower and weight into a small, and already awkward handling airframe like the 109, without making it even more challenging to operate.
Now jump ahead to the 21st century. The airframes are old and tired (except the new builds), and any one with any sense of responsibility is going to handle them gingerly. Add to that everybody is going to be operating at reduced power settings. 100LL hasn't the antiknock qualities of WWII fighter fuels, although it's closer to what the Germans had than the allies. That said, nobody flying on today's fuel is going to go "through the gate" into WEP in a "friendly" mock dogfight.
Likewise, pilots aren't likely to aggressively explore the G limits of those valuable tired airframes.
So, since the 109s operated on generally less high performance fuels than the 51s back then, and a goodly number of today's 109s are new builds, perhaps they are operating at somewhat less of a handicap than in 1944-45.
Cheers,
Wes

Real:
Also, a fair number of P-51 pilots entered the war flying different or less advanced fighters; for instance, the 78th FG of the 8th AF learned a lot while flying P-47s. So much so, that they initially wanted to keep their P-47s . . . as they learned how to use them to great effect. But once they switched, they saw advantages the P-51D had over the P-47!

 

[XBe02Drvr]

Resp:
I read a post-war US assessment that came to the same conclusion; four guns did the trick. However, it would be hard to envision a 4 gun P-47.

I think a flak tower or a locomotive would much rather face a 4 gun jug, given the choice.

 

[drgondog]

I've seen so many conflicting accounts of P-51s vs whatever the Germans had at the time from our combat pilots then, and guys who fly these planes today, and I can't get over how different their opinions are. These writings seem to claim the P-51 was considerably superior to the 109, and the 51 pilots had a pretty easy time outflying them, but if you listen to some of todays pilots that have flown both, they claim the 109 was superior. They say it would outclimb, outdive, and outturn the 51. I don't know who to believe, but I would tend to believe those who actually flew them in combat situations over today's pilots...

Apples and oranges in so many ways - mostly related to Power Available vs Power Required. The Warbirds of today don't run over 51" (occasionally 61 METO) in the 51. None of the friendly competitions in past 60 years between various 109 version ever come close to 75" MP available to the 1650-7 or 90" in the 1650-9 with WI - fuel availability of Spec 44 130/150 and engine replacement costs being greatest factors.

Also consider that guns and ammo weight as a weight fraction to the airframe is higher for the 109. when you strip armament and armor from both, the 109 wing loading advantage increases over the Mustang. Last but not least is that none of these excursions are at 22-30000 feet where the engine power advantage is distinctly in the Merlin 61/65 corners.

Might also mention that Skip Holm, the most vocal of those voices, had 5 or 6 Bf 109s he was trying to sell. That said, Skip was an excellent pilot.

 

[pbehn]

Resp:
I read a post-war US assessment that came to the same conclusion; four guns did the trick. However, it would be hard to envision a 4 gun P-47.

In combat it was 10% better which is worth a negligible drop in performance. In ground attack it was 50% better and it was used for ground attack.

 

[Milosh]

So, since the 109s operated on generally less high performance fuels than the 51s back then

B4 fuel but not C3 fuel. C3 was at least 125PN.

 

[Navalwarrior]

The -6 canopy (Dallas Canopy, bulged in comparison with the -2). My father flew the B/C canopy, the Malcolm Hood and both D canopy versions. He liked the Dallas D best, the Malcolm Hood next, the -2 canopy for the P-51D-5/-10-NA next and birdcage last.

Resp:
I know this question deals with post war P-51s, but you may have an answer. I have seen at least two P-51D with extended 'vertical stabilizers' at Air Shows. These are much taller than the 14'8" stabilizer on factory Mustangs. What, if any, advantages does a taller one provide?

 

[XBe02Drvr]

Resp:
I know this question deals with post war P-51s, but you may have an answer. I have seen at least two P-51D with extended 'vertical stabilizers' at Air Shows. These are much taller than the 14'8" stabilizer on factory Mustangs. What, if any, advantages does a taller one provide?

Almost always when you see extended tailfeathers on an airplane it's to deal with some sort of stability issue, such as perhaps more power with its resulting torque and P factor, or a mod that results in more side area forward of the center of pressure. The cut down razorback of the bubble top Mustangs reduced the keel effect aft of the CoP, resulting in a strake extension being added forward of the vertical stabilizer. It's not hard to imagine increases in horsepower resulting in the need for yet more surface area aft. And given that the P51 can be a bit of a handful for a non military trained civilian nosedragger pilot, a little added stability can't hurt.
Cheers,
Wes

 

[drgondog]

Resp:
I know this question deals with post war P-51s, but you may have an answer. I have seen at least two P-51D with extended 'vertical stabilizers' at Air Shows. These are much taller than the 14'8" stabilizer on factory Mustangs. What, if any, advantages does a taller one provide?

It is all about increasing rudder/fin authority while trying to retain excellent roll characteristics. R-R noticed the yaw instability introduced by changing from Allison/three blade to Merlin four blade system when throttle advanced or retarded. the first step was the DFF which improved the yaw issues, the second was to increase the fin chord which further improved but resulted in lessened roll capability. The first tall tail was introduced in test on P-51B-1-NA 43-12095 which later went to NACA for dive tests. The production DFF was introduced to the P-51B/C and D in kit form April 8, 1944 along with Reverse Rudder Boost Tab but the fin cap never made production until the P-51H.

At the long end of the test 'tunnel' the fin cap (tall tail), the DFF and finally the added 13 inches to the fuselage of the P-51H was the best combination in 1945.

 

[drgondog]

Almost always when you see extended tailfeathers on an airplane it's to deal with some sort of stability issue, such as perhaps more power with its resulting torque and P factor, or a mod that results in more side area forward of the center of pressure. The cut down razorback of the bubble top Mustangs reduced the keel effect aft of the CoP, resulting in a strake extension being added forward of the vertical stabilizer. It's not hard to imagine increases in horsepower resulting in the need for yet more surface area aft. And given that the P51 can be a bit of a handful for a non military trained civilian nosedragger pilot, a little added stability can't hurt.
Cheers,
Wes

Wes - actually cutting the quarterdeck/turtleback from B/C to D was not the issue - it was discovered when R-R made the conversion from Allison to Merlin in fall 1942. It took over a year for NAA to test various configurations to arrive at the DFF (104-25001 and 109-25001) config for P-51B/C and D in late March 1944 for production release. The aft deck issue was more a root cause leading to decreasing the H.Stab angle of incidence and adding metal elevators due to ripping fabic elevators in terminal dives.

 

[wuzak]

DFF = dorsal fin fillet?

 

[Navalwarrior]

It is all about increasing rudder/fin authority while trying to retain excellent roll characteristics. R-R noticed the yaw instability introduced by changing from Allison/three blade to Merlin four blade system when throttle advanced or retarded. the first step was the DFF which improved the yaw issues, the second was to increase the fin chord which further improved but resulted in lessened roll capability. The first tall tail was introduced in test on P-51B-1-NA 43-12095 which later went to NACA for dive tests. The production DFF was introduced to the P-51B/C and D in kit form April 8, 1944 along with Reverse Rudder Boost Tab but the fin cap never made production until the P-51H.

At the long end of the test 'tunnel' the fin cap (tall tail), the DFF and finally the added 13 inches to the fuselage of the P-51H was the best combination in 1945.

Resp:
Yes, I have noticed the production P-51H had a tall tail. Thanks.

 

[Navalwarrior]

Resp:
Yes, I have noticed the production P-51H had a tall tail. Thanks. I've also know that Supermarine changed the rudder on their MkVIII and later MkIXs (retro fitted?).