Zoom climb

[drgondog]

Betty Jane was restored with a modern panel. At 10,000ft in level flight at 36" to 38" I indicate around 220kts at around 73gph. Next time I'm up I'll take some photos in cruise at various altitudes. It's a fun exercise with customers to show them the different performance curves. I meant 200mph, not knots...I've been flying her in kts for so long I really have to stop and think about which plane I'm in or what I am typing.

Thanks, Jim for those that remain confused about KTS, MPH and altitude adjustments
"220kts Indicated" at 10K for IAS at 2400/38" is about 253mph IAS (on original instrument panel and about 296mph True Airspeed.

The book example above is:

So, roughly 'the Book' thinks that after getting back to 10K and back to steady level flight at your panel instrument readings of 2400RPM, 38"MP, and then reading ~ 234kts IAS? burning somewhere around 73 gph? for a calculated 317 mph TAS?


Jim

So, your experience in Betty Jane is 220kts IAS versus a table extraction of 234kts IAS at 10,000 feet. a Delta of 14Kts/16mph slower in today's Betty Jane than the 1944 Tables present for 10K, ~ 8500pounds GW at TO,

270mph IAS (calculated Manual 235kts IAS vs Betty Jane actual = 220kts IAS), 2400RPM vs 2400 RPM, 38"MP vs 36 to 38"MP, 315mph TAS vs Betty Jane PROJECTED 301mph TAS.

Net difference between Manual and today's experiences w/Betty Jane is 14KTs Indicated and 15+mph TAS or about a 5% Delta Lower performance than the Book.

Thanks for taking the time, Jim

 

[DerAdlerIstGelandet]

They didn't cruise that fast and all the writing in the world won't change tat fact. Go talk with the vets before they are all gone and LISTEN for a change.

Considering Bill's father was a P-51 flyer, I think he has.

I think you are biting off more than you can chew and should take your own advise.

 

[DerAdlerIstGelandet]

Cricket, cricket, cricket...

 

[drgondog]

I think the various Cruise throttle, rpm and manifold pressure settings vs IAS vs TAS for various operational range planning scenarios has worked its course.

Everybody else has been in Oshkosh lately.

Jim H raised an interesting point regarding current Mustangs experiencing about 5% less actual cruise speeds at 10,000 feet than the P-51D manual posts for clean airframe and his airspeed indicator snapshots coupled with the manifold pressure and Tach and RPM confirms it for Betty Jane. As that P-51B is a Collings ship there is no notion that it is not getting world class maintenance.

I'm curious so I have asked a pilot friend at POF to run some comparisons in some of the 51's he flies to compare the 10,000 foot results at same or similar control settings.

So, to summarize:

The P-51D-5 Manual, Flight Operating Instructions, AN 01-60JE-1, dated April 1944, posts a setting that it defines as Maximum Continuous Power, and further states for Emergency Cruise only is:

2700RPM, Auto Rich, 46" MP. The various Ranges are cited for this setting with full internal fuel of 269 gallons, wing racks only (~ 6mph additional drag from clean) - 9600-8000 pounds GW -Page 54

No consideration for warm up, take off at MP, climb to altitude, or on the landing leg of the flight profile.
590 miles at 25000 feet 280mph IAS, 410mph TAS, 110 gph consumption

518 miles at 10000 feet 305mph IAS. 355mph TAS, 108 gph consumption.

With 75 gallon tanks 419 gallons fuel, GW= 10,700 to 9600..
1820 miles at 25000 feet 2200RPM 200mph IAS, AL, FT,295mph TAS, 57mph ----------> Long Range escort
1700 miles at 10000 feet 1750RPM 200mph IAS, AL, FT, 245mph TAS, 52gph

No tables for 110 gallon tanks as they weren't introduced until May 1944, nor were they flight tested until June to update the future Operating Instructions.

 

[DSR T-888]

Table V compares the diving performance of the P-51, P-47, F4U and Hellcat. I was actually surprised that the P-47 was able to out dive the P-51, even when starting at lower speeds. Wouldn't an aircraft that dives faster also zoom climb faster?

http://a.moirier.free.fr/Essais en vol/Flight test comparison.pdf

 

[drgondog]

Table V compares the diving performance of the P-51, P-47, F4U and Hellcat. I was actually surprised that the P-47 was able to out dive the P-51, even when starting at lower speeds. Wouldn't an aircraft that dives faster also zoom climb faster?

http://a.moirier.free.fr/Essais en vol/Flight test comparison.pdf

It depends but in most cases of the initial phase of the recovery and climb - yes. The comparison between these two requires consideration for the differences in weight and drag as the zoom climb continues. The Mustang weighed less and had less drag but the P-47 had more Thrust Horsepower.

I wouldn't bet the farm on the evaluations. The use of 100LL instead of wartime 130 or even 150 octane limits the Mustang the most in these evaluations and I am mystified regarding the discussion of stick forces in the turn and reverse maneuver comparisons. You probably also noted that the dives were all at 30degrees - which would favor the heavier aircraft slightly and in no way pushes the test to Vne - The Mustang and P-47 were very close in terminal dive speeds but the Mustang's entry and recovery from Ncr were more benign.

As to the comments regarding the Mustang's handling characteristics in maneuver and marveling at its combat record despite the high stick forces? Guys like Zemke who flew the P-47, P-38 and P-51 in combat clearly favored the Mustang to fight with - citing its maneuverability, performance and range. He scored victories against the same enemy in all three aircraft.

As an aside, if you wish to explore another documented test comparisons of 125+ fighter and test pilots from Army, USN, USMC, RAF, NACA, and the manufacturers comparing all the top Allied Fighters - day and night both - then read the "Report of Joint Fighter Conference - NAS Patuxent River, MD 16-23 October, 1944". The aircraft tested and compared and ranked for Stability, Controllability, Performance, Armament, Cockpit, Power Plant and Protection. The aircraft included F4U-4C, P-47D-30, P-38L-5, F6F-5, F7F-1, XF8F-1, P-61A, P-51D-15, Mosquito, FG-1A, P-63, FM-2, XF2G-2, Zeke-52, Seafire

 

[DSR T-888]

It depends but in most cases of the initial phase of the recovery and climb - yes. The comparison between these two requires consideration for the differences in weight and drag as the zoom climb continues. The Mustang weighed less and had less drag but the P-47 had more Thrust Horsepower.

I wouldn't bet the farm on the evaluations. The use of 100LL instead of wartime 130 or even 150 octane limits the Mustang the most in these evaluations and I am mystified regarding the discussion of stick forces in the turn and reverse maneuver comparisons. You probably also noted that the dives were all at 30degrees - which would favor the heavier aircraft slightly and in no way pushes the test to Vne - The Mustang and P-47 were very close in terminal dive speeds but the Mustang's entry and recovery from Ncr were more benign.

I'm curious of how the 30 degree angle dive would favour the heavier aircraft. Recovery from nearly hitting compressibility? The P-47D-30s and above had dive recover flaps installed. Pulling out is much more physically demanding on the P-51 compared to the P-47 or any other allied fighter. What is Ncr?

As to the comments regarding the Mustang's handling characteristics in maneuver and marveling at its combat record despite the high stick forces? Guys like Zemke who flew the P-47, P-38 and P-51 in combat clearly favored the Mustang to fight with - citing its maneuverability, performance and range. He scored victories against the same enemy in all three aircraft.

What was Zemke's preferred dog fighting style? Just by doing some quick research he did exploit the P-47's strengths of BNZ. Pilots like Erich Hartmann seemed to prefer the style of "Boom 'N' Zoom", He said in an interview that he'd only attack if he had 2000 meters of clearance above the enemy. I can only imagine a plane with lighter stick forces and greater firepower would favour this roll. Possibly a dog-fighting roll would favour the P-51 due to its greater acceleration and turning capabilities. From what I can find on the P-38, obviously depending on the variant of which he flew. The P-38 could turn a slightly tighter radius and could roll faster than the P-51. I'm making the assumption that he probably favoured the P-51 over the P-38 because of its superior visibility.

As an aside, if you wish to explore another documented test comparisons of 125+ fighter and test pilots from Army, USN, USMC, RAF, NACA, and the manufacturers comparing all the top Allied Fighters - day and night both - then read the "Report of Joint Fighter Conference - NAS Patuxent River, MD 16-23 October, 1944". The aircraft tested and compared and ranked for Stability, Controllability, Performance, Armament, Cockpit, Power Plant and Protection. The aircraft included F4U-4C, P-47D-30, P-38L-5, F6F-5, F7F-1, XF8F-1, P-61A, P-51D-15, Mosquito, FG-1A, P-63, FM-2, XF2G-2, Zeke-52, Seafire

Thanks, I'll take a look.

I'm still learning, that's why I made this account.

I do enjoy reading a lot of your comments drgondog.

 

[DSR T-888]

Here are some Immelmanns and Split S's comparing the P-47D(light blue) and P-47N(Blue)

http://i.imgur.com/8BUoBWL.png
http://i.imgur.com/PsnNRXD.png
http://i.imgur.com/x2kOs4n.png
http://i.imgur.com/Ghb5NyM.png

 

[drgondog]

I'm still learning, that's why I made this account.

I do enjoy reading a lot of your comments drgondog.

I'm curious of how the 30 degree angle dive would favour the heavier aircraft. Recovery from nearly hitting compressibility? The P-47D-30s and above had dive recover flaps installed. Pulling out is much more physically demanding on the P-51 compared to the P-47 or any other allied fighter. What is Ncr?

The force of gravity is acting on all aircraft. In level flight the weight of the a/c is equally offset by the Lift, but contributes zero to the longitudinal axis (X)in line with the propeller thrust. As the a/c noses over the Weight force vector in the vertical plane of reference (Z)diminishes as W'COS (dive Angle) and the Weight Force vector increases from Zero along the X axis as SIN (dive angle) As the a/c noses. In a full 90 degree 1g dive (trimmed), there is no effective lift vector and all the Weight contributes to the Thrust vector. The case for climb is just the opposite as in climb the Weight Vector aligned with the thrust axis is working Against the Propeller Thrust.

Net - all things equal (T, D), the heavier ship will tend to out accelerate the lighter ship in a dive and under perform in a climb.

What was Zemke's preferred dog fighting style? Just by doing some quick research he did exploit the P-47's strengths of BNZ. Pilots like Erich Hartmann seemed to prefer the style of "Boom 'N' Zoom", He said in an interview that he'd only attack if he had 2000 meters of clearance above the enemy. I can only imagine a plane with lighter stick forces and greater firepower would favour this roll. Possibly a dog-fighting roll would favour the P-51 due to its greater acceleration and turning capabilities. From what I can find on the P-38, obviously depending on the variant of which he flew. The P-38 could turn a slightly tighter radius and could roll faster than the P-51. I'm making the assumption that he probably favoured the P-51 over the P-38 because of its superior visibility.

I suspect that all pilots that spot an enemy first will first seek a tactical advantage such as altitude and position (out of sun, blind spot, etc) but every fighter pilot that saw a lot of combat and encounters would have to deal with situations not favorable to them. Zemke for example was almost shot down by Krupinski (Not Rall) on May 12, who was attacking Zemke with a 5000 foot altitude advantage in a BnZ manner. He avoided the attacks but both his wingmen were shot down. Zemke then shot down a 109 up north of that location by simply sneaking up from six o'clock. In other words tactics were a combination of a.) planning and b.) desperation.

Every fighter pilot I know or have known over the last 65 of my 70 years knew the strengths and weaknesses of his aircraft and the enemy he fought as well as 'what Not to do' when caught at a disadvantage.

The P-38 when it employed the maneuver flaps of the P-38J-25 and all P-38L's could slightly out turn a Mustang (or a 109 or a FW 190). Correspondingly it lost energy faster because of the major drag penalty of a P-38 compared to P-51. Secondly, the P-38 could out roll a Mustang with the following caveat. Despite the roll rate due to boosted ailerons - it was Not and 'instantaneous' roll response. That was a HUGE fighter with a lot of roll inertia due to the outward locations of the engines.

The Fighter Conference notes on the P-38 spent a lot of time discussing the "Yes, but.." nature of initiating the turn with control yoke... and waiting, waiting - before the Roll was actually occurring.
It would slightly out accelerate and slightly out climb the comparable Mustang series by developing twice as much Hp to overcome the drag (until 130/150 octane was available to increase the 1650-7 boost from 67 to 72/75" in WEP).

Look also to the same comments recaptured in America's One Hundred Thousand" by Dean.

IMO the P-38 primarily failed to achieve expected results in the ETO for three reasons:
First is was easy to see and identify, giving an opponent with an equally performing aircraft a Major advantage of being able to see it first and plan accordingly.

Second, the intercooler and Turbocharger design was flawed for high altitude operations in the ETO until the J-15 was introduced in March 1944. Engine and turbo failures abounded.

Last but not least is that a FW 190 and Bf 109 easily out dove it because the P-38 at high cruise at 25000 feet was cruising only 10% under onset compressibility and almost immediately went into critical Mach compressibility when it pushed over. The shock wave developed and changed the Center of Pressure aft causing a nose down pitching moment, and the fully developed boundary layer separation tended to cause major turbulence immersing the elevator - all these factors made it impossible to pull out of a dive until much denser air was reached at lower altitudes.

Mcr is Mach Critical Velocity at which point a fully developed shock wave forms. A classic airfoil design of the period had the maximum T/C at 25% and the Center of Pressure near that point on the wing cord - whereas the Mustang max T/c was at ~45% and the CP near that point. As the velocities increase from leading edge on the 23xxx or similar (for F4U, F6F, FW 190, P-38, P-47) airfoils, there is a steeper velocity gradient from leading edge to peak velocity at 25% chord than the velocity profile for the NAA/NACA 45-001 laminar flow airfoil on the P-51 - causing the Mcr Compressibility shock wave to start at a higher velocity - for equivalent thickness of the wing. The P-47, Bf 109 and Spit had 'thinner' wings which also delays onset compressibility but not as much as the laminar profile achieves.


The Mcr of the Mustang was closer to .75-.8M and the movement of the CP was not so nearly dramatic as to cause a severe nose down pitching moment. NAA actually designed a Dive flap for the P-51D (similar to P-47D-30) but NACA decided after testing that it was not needed.