Zoom climb

[Conslaw]

Friends,

I think we're too hung up on a number. There is nothing magical about 380 MPH. The tactical advantage doesn't come in a number it comes in the status of being "fast enough". My premise is that entering into the combat area fast, before contact with the enemy is a huge tactical advantage. At this stage, you aren't going to be be using any fluid injection, and you are not going to be using a power setting that requires a tear-down at the end of the flight. In other words, you aren't going to uses "war emergency" power. You also aren't going to use a power setting that doesn't give you enough endurance to do what you want to do. You will use the highest power setting that allows you to do what you need to do. You might call that a "fast cruise". You might call it something else. The Mustang, because of its low drag, could go faster per unit of power and fuel consumption than most or all of its peers/adversaries. Going into the battle fast in a Mustang is crucial because the plane is heavy in relation to its power. Not being caught low and slow is crucial to survivability in a P-51. If a P-51 is bounced while in eco-cruise, all of its performance advantages are gone. Conversely, if the P-51 maintains a continuous speed (none dare call it "cruising") in the combat area which is above the maximum continuous speed of its adversary's, the adversary will be at a significant disadvantage unless the adversary has a substantial altitude advantage. It is unlikely the adversary will have a position advantage at the Mustang's 6 because the Mustang already passed that area faster than the adversary could go. If you start with that speed advantage, add in a numerical advantage and the advantage that the P-51's main job is to protect bombers, and the Luftwaffe's main ob was to shoot down bombers, it is easy to see how the P-51 had the second highest score against enemy aircraft for US fighter types. (#1 was the F6F Hellcat which was slower than the Mustang, but was fast enough to do what it had to do.)

 

[GregP]

You're right. Nothing magical about it at all. But it was stated and they didn't do it in the real, actual war.

Capability to do it aside, why the heck would anyone escort someone while flying twice the speed of the escorted planes? You'd be more than doubling your plane's actual flown range, and a 1,200 mile mission is long enough.

Pushing up the speed when you expect combat is reasonable, but cruising there isn't. Might be different if you were escorting B-29s and if they were crusining at 230+ mph, then there would be at least SOME justification for flying faster in the ETO, but we din't use B-29s in the ETO , and there was NO point in going faster in the PTO most of the time becuase the weather was mostly severe clear and you could see your enemies a long way off.

If the weather was bad that's another story since you were better off engaging faster against Japanese fighters. If you fought them slow, the'd likely get you.

 

[drgondog]

it is easy to see how the P-51 had the second highest score against enemy aircraft for US fighter types. (#1 was the F6F Hellcat which was slower than the Mustang, but was fast enough to do what it had to do.)

A common misconception. The F6F was credited with 8 (ETO),0 (MTO), 5160 (PTO) 0 (CBI)Total = 5168

The P-51 was credited with 4239 (ETO) 1862 (MTO),297 (PTO), 345 (CBI).. Total = 5964.



Aircraft Type ETO - European Theatre of Operations MTO - Mediterranean Theatre of Operations PTO - Pacific Theatre of Operations CBI - China-Burma-India Total
P-51(Includes F-6 and A-36)
P-51 4239 1063 297 345 5954
F6F 8 0 5160 0 5168
P-38 497 1431 1700 157 3785
P-47 2685.5 263 696.67 16 3661
P-40 0 592 660.5 973 2225.5
F4U 0 0 2140 0 2140
F4F 0 26 986 0 1012
FM-2 0 0 422 0 422
Spitfire 15 364 0 0 379
P-39 P-400 2.5 25 288 5 320.5
SBD 0 0 138 138
P-61 59 0 63.5 5 127.5
TBF/TBM 0 0 98 0 98
Beaufighter 6 25 0 0 31
F2A 0 0 10 0 10
P-43 0 0 3 3 6
P-36 0 0 3 0 3
P-70 0 0 2 0 2
P-26 0 0 2 0 2
P-35 0 0 1 0 1
Mosquito 0 1 0 0 1

Aircraft Type ETO - European Theatre of Operations MTO - Mediterranean Theatre of Operations PTO - Pacific Theatre of Operations CBI - China-Burma-India Total
P-51(Includes F-6 and A-36) 4239 1063 297 345 5954
F6F 8 0 5160 0 5168

 

[drgondog]

You're right. Nothing magical about it at all. But it was stated and they didn't do it in the real, actual war.

Greg - slooooooowly. It was stated that it Could cruise at Max Continuous Power at 380, when in fact with just racks it Could cruise at 404-410 mph TAS.

Repeat once - It Could Cruise at what is described in AN 01-60JE-1, dated September 1944 for the P-51D-5, as Emergency Cruise, at 2700RPM, 46" MP at 25,000 feet at 410mph with a fuel burn rate of 115gph. Page 54.

Capability to do it aside, why the heck would anyone escort someone while flying twice the speed of the escorted planes? You'd be more than doubling your plane's actual flown range, and a 1,200 mile mission is long enough.

Sloooooooooooowly Greg, 'No One' would escort at twice the speed of the escorted planes if they were flying close escort.

Slooooooooooowly, Greg, 'No One' would fly at Max Continuous Cruise settings if the mission was to provide, say target escort at Berlin for a roundtrip of 1100-1200 miles.

Slooooooooooowly, Greg, YOU are the only one that keeps connecting '380mph Cruise at Max Continuous' with the second phrase 'Escort to Berlin'. Nobody but You.

Pushing up the speed when you expect combat is reasonable, but cruising there isn't. Might be different if you were escorting B-29s and if they were crusining at 230+ mph, then there would be at least SOME justification for flying faster in the ETO, but we din't use B-29s in the ETO , and there was NO point in going faster in the PTO most of the time becuase the weather was mostly severe clear and you could see your enemies a long way off.

If the weather was bad that's another story since you were better off engaging faster against Japanese fighters. If you fought them slow, the'd likely get you.

Once again, to help you understand escort factors for the P-51, the reason that flight tests were done Before AN 01-60JE-1 were to fully understand optimal cruise settings BELOW maximum continuous power - which at the same time were nearly 70-100 mph faster than the B-17G at 25000 feet at Best settings for 110 gallon tank cruise speeds.

Sloooooooooooowly Greg - the 281mp TAS from Best Cruise setting (way below Max Cruise Power) was close to 200 IAS at 25,000 feet for 4.81 miles per gallon for 11,600 pound P-51D-5-NA. As the fuel burned off, the Gross weight burned away at about 300 pounds per hour giving the P-51D-5-NA even better cruise performance each hour of the escort leg.

Sloooooooooooowly Greg - at 281 to 300 mph for a two hour penetration/target and withdrawal mission before relief - those darn P-51s are still flying 80-100mph FASTER than those slow ass B-17s at 205mph TAS.. BUT Dayum - they are still hanging around those rascally slow B-17s (or the faster B-24s). How Essing or running up and back paralleling the Bomber boxes they were assigned to.


So - Please quit darkly hinting about boneheads that don't understand you - or escort tactics flown by all the folks that lecture at POF. THEY aren't Disagreeing with the scenario I just laid out for you. YOU don't comprehend what they are telling you - and you don't know enough about Mission Profiles and Operational planning/Execution to ask questions when you don't comprehend what you are hearing?

QUIT saying or implying that either Shortround or I are saying that ETO missions were flown ANYWHERE NEAR max Continuous Power. It is irritating that you don't understanf, but even more irritating that you keep repeating yourself.

 

[pbehn]

I was just surprised and curious as to how an aircraft could be said to "cruise" with or without external tanks, full or almost empty internal fuel at almost any speed between stall and maximum as the same in terms of economy and therefore distance. The aerodynamic drag of external tanks and the additional drag of having to provide lift for the extra weight to me means the quoted cruise speed would actually be the maximum or close to it. Drag increases with speed, increasing weight increases drag in the case of internal fuel, increasing fuel by external tanks increases weight and massively increases drag. The idea that in any configuration a P 51 can fly about at any speed and fuel consumption is not a serious consideration is, shall I say new to me.

 

[Shortround6]

Please look at the charts provided.

Or this test. P 51D Performance Test

Please note using WER this plane could do 438mph at 25,000ft using 67in and 3000rpm and that was calculated to be 1410hp.
Dropping to Military power the plane could do 428mph at 25,000ft using 61in and 3000rpm and that was calculated to be 1285hp.
Dropping to max continuous the plane could do 404mph at 25,000ft using 46in and 2700rpm and that was calculated to be 1025hp.

72.7% of the power will give you 92% of the speed so the cruise figures are hardly maximum. Many planes cruise at 70% of max power (OK I cheated a bit, many planes would cruise at 70% of military of take-off power)

However your statement about " almost any speed between stall and maximum as the same in terms of economy and therefore distance" isn't quite right either as the charts show that on the same fuel the Mustang will go 35% further by slowing down to around 335mph from the 390-400mph speed.

 

[Ottobon]

There is a HUGE distinction between how lightweight and high power planes like say Spitfires, mid to latewar Yaks Lavochkins, BF 109s, or even A6Ms can utilize zoom climbs and how heavyweight, high speed, but lower power to weight planes like a P-47, Tempest, or FW 190 can utilize a zoom climb.

The distinction being that in steep, high G, and high angle zoom climb being a fantastic move in the lighter planes which usually incure less induced drag and feature very high powerloading/climbrate. With heavy planes you have to maintain that speed by not pulling too many Gs (bleeding too much speed) and then letting your power and inertia from the heavy weight or aerodynamics (P-51) sustain your climb and extend away.


The best description of this effect is probably told first hand in a story by Robert Johnson where he had a impromptu mock dogfight with a unknown Spitfire pilot:

"I opened the throttle full and the Thunderbolt forged ahead. A moment later exhaust smoke poured from the Spit as the pilot came after me. He couldn't make it; the big Jug had a definite speed advantage. I grinned happily; I'd heard so much about this airplane that I really wanted to show the Thunderbolt to her pilot. The Jug kept pulling away from the Spitfire; suddenly I hauled back on the stick and lifted the nose. The Thunderbolt zoomed upward, soaring into the cloud-flecked sky. I looked out and back; the Spit was straining to match me, and barely able to hold his position.

But my advantage was only the zoom--once in steady climb, he had me. I gaped as smoke poured from the exhausts and the Spitfire shot past me as if I were standing still. Could that plane CLIMB! He tore upward in a climb I couldn't match with the Jug. Now it was his turn; the broad elliptical wings rolled, swung around, and the Spit screamed in, hell-bent on chewing me up.

This was going to be fun. I knew he could turn inside the heavy Thunderbolt; if I attempted to hold a tight turn, the Spitfire would slip right inside me. I knew also, that he could easily outclimb my fighter. I stayed out of those sucker traps. First rule in this kind of fight: don't fight the way your opponent fights best. No sharp turns; don't climb; keep him at your own level.

We were at 5,000 feet, the Spitfire skidding around hard and coming in on my tail. No use turning; he'd whip right inside me as if I were a truck loaded with cement, and snap out in firing position. Well, I had a few tricks too. The P-47 was faster, and I threw the ship into a roll. Right here I had him. The Jug could outroll any plane in the air, bar none. With my speed, roll was my only advantage, and I made full use of the manner in which the Thunderbolt could roll. I kicked the Jug into a wicked left roll, horizon spinning crazily, once, twice, into a third. As he turned to the left to follow, I tramped down on the right rudder, banged the stick over to the right. Around and around we went, left, right, left, right. I could whip through better than two rolls before the Spitfire even completed his first. And this killed his ability to turn inside me. I refused to turn. Every time he tried to follow me in a roll, I flashed away to the opposite side, opening the gap between our planes.

Then I played the trump. The Spitfire was clawing wildly through the air, trying to follow me in a roll, when I dropped the nose. The Thunderbolt howled and ran for earth. Barely had the Spitfire started to follow--and I was a long way ahead of him by now--when I jerked back on the stick and threw the Jug into a zoom climb. In a straight or climbing turn, the British ship had the advantage. But coming out of a dive, there's not a British or German fighter than can come close to a Thunderbolt rushing upward in a zoom. Before the Spit pilot knew what had happened, I was high above him, and the Thunderbolt hammering around. And that was it--in the next few moments the Spitfire flier was amazed to see a less-maneuverable slower-climbing Thunderbolt rushing straight at him, eight guns pointing at his cockpit."

(From Fighter Combat, Robert Shaw)

 

[GregP]

Bill,

You and I are gonna' disagree forever on how fast the Mustang cruised. Just a fact. You think anybody in 1943 - 1944 took off at under 10,500 pounds?

In fact, we can disagree and it's fine. I know what the guys I know who own them say and what the veterans who flew them say, and that's good enough for me. If it isn't for you, well then - OK.

Let's say we both think it was a very good fighter, even great, and let the details alone betwen us. I'll continue to think what I do and so will you. Neither one detracts from the combat record or the legacy, so let it go at that.

I'll allow they cruised fast on fighter sweeps away from bomber escort, but I'll just laugh at the thought 410 mph cruise. Didn't happen as far as I know. But out of completeness, I will ask next weekend when the vets show up again for the "Little Friends" event.

Please quit being condescending. It's all I can do to be civil already. Just say what you're going to say and leave out the barbs and put downs. Things will be much friendlier that way.

 

[Conslaw]

I love this quote from Johnson about his climbing duel with the Spitfire. Later in Thunderbolt, (page 176 according to Google book search) he talks about how the paddle-blade propeller helped the Thunderbolt's performance. He said after he got the paddle-blade propeller he had a climbing dual with a Spitfire 9b - the same model that out-climbed his P-47 earlier, and this time the Thunderbolt was the faster climber.

 

[GregP]

Lots of people forget that the P-47 had two lives ... before paddles and after paddles.

 

[Ottobon]

Happy you enjoyed it, another comment or subject about zoom climbing real quick.

Maybe I'm barking up a tree that has already read these documents, but i always found the F4U vs FW 190 A4 documentation interesting,

http://www.wwiiaircraftperformance.org/fw190/ptr-1107.pdf

Specifically the part where the FW 190 A4 being noted as having much better performance in high speed zoom climbs (although worse at any fairly low/medium speeds.) I'll assume this is mostly down to drag, although more specific aspects of it would be interesting to know. If nothing else the ideal climbspeeds of the F4U and FW 190 alone indicate a FW 190 has low enough drag but also high enough wing loading it just works better at high speed (about 160mph on Corsair vs 180mph on FW 190 iirc. Quite large frontal area of the F4U probably being a factor.



Anyways i find it interesting because considering both the FW 190 A4 and F4U-1 (with Water Injection apparently) jockied for similar speeds, acceleration, and climbrate at various altitudes i would normally suspect that with built up inertia a F4U due to excess weight it would be close to the FW 190 A4 in a high speed zoom climb, but apparently the aerodynamics are such that the 190 would just pull away in any high speed zoom climb.

Any comments on this subject?

 

[GregP]

Never knew the F4U and the Fw 190 ever fought one another, so never considered it. Will have to think on it. I'd take an F4U-4 any day, but the F4U-1, -1A, and -1D are much closer to the Fw 190 radial aircaft. They are Naval and so have the requisite weight and low-speed handling and ruggedness for carrier operations. They also rolled better than some US fighters but not as well as the Fw 190.

When I get time, I'll look at it. Good comparison to think about.

The Fw has the armament advantage all the way, but the F4U ain't no slouch in a fight.

 

[Mike Williams]

Happy you enjoyed it, another comment or subject about zoom climbing real quick.

Maybe I'm barking up a tree that has already read these documents, but i always found the F4U vs FW 190 A4 documentation interesting,

http://www.wwiiaircraftperformance.org/fw190/ptr-1107.pdf

Specifically the part where the FW 190 A4 being noted as having much better performance in high speed zoom climbs (although worse at any fairly low/medium speeds.) I'll assume this is mostly down to drag, although more specific aspects of it would be interesting to know. If nothing else the ideal climbspeeds of the F4U and FW 190 alone indicate a FW 190 has low enough drag but also high enough wing loading it just works better at high speed (about 160mph on Corsair vs 180mph on FW 190 iirc. Quite large frontal area of the F4U probably being a factor.



Anyways i find it interesting because considering both the FW 190 A4 and F4U-1 (with Water Injection apparently) jockied for similar speeds, acceleration, and climbrate at various altitudes i would normally suspect that with built up inertia a F4U due to excess weight it would be close to the FW 190 A4 in a high speed zoom climb, but apparently the aerodynamics are such that the 190 would just pull away in any high speed zoom climb.

Any comments on this subject?

Perhaps you're conflating the results of sustained climbing with zoom climb? Section 3. a. of the report discusses rates of climb at rated powers for indicated airspeeds of 140, 160, 180 and 200 knots at various altitudes, with the FW 190 generally being better the faster the climb.

Section 3. f. of the report discusses manueuverability, noting that "In zooms after dives the Fw-190, f4u-1 and F6f-3 were found to be about equal."

 

[drgondog]

Bill,

You and I are gonna' disagree forever on how fast the Mustang cruised. Just a fact. You think anybody in 1943 - 1944 took off at under 10,500 pounds?

Greg - this is a good illustration of one of many reasons why I move from debate to scorn when any conversation goes past ONE exchange.

On Post #16, my VERY first post on this subject, I said this following SR's post of the p-51D Operating manual...

Don't understand the debate about the Official Pilot's Operating Manual. They are straight from the Flight Tests to optimize range for P-51D-15 with racks only, fully loaded internally, and also with 110 gallon fuel tanks and also 500 and 250 pound bombs... 11,700 pounds at take off with the 110's, 10,200 with full internal load, clean wing with racks only

From the Flight Tests - also available on Mike Williams' site, at 2700 RPM and 46" MP - a Safe Continuous Power setting for all Merlin Mustangs.

25K Rack only 404mph cruise@100 gallons per hour
25K 110 Gallon 371mph cruise@89 gallons per hour
25K 500# Bombs 357mph cruise@100 gallons per hour
25K 250# Bombs 381mph cruise@92 gallons per hour

Those are not optimal cruise settings. The optimal settings for maximum Range (normal deep escort profile to say Poland) for 110 gallon tanks at low recommended Lean mixture was for25K 110 gallon tanks 303mph@57 gallons per hour for 2250 RPM and 29" MP. That is the TAS they flew at 25000 feet while they were linked to close escort (i.e. Essing while connected to a specific Box). It was not the speed and settings used to fly to the R/V or Sweep or return home after BE unless the mission profile was Extreme Range requirement such as Posnan with a 1480 mile round trip.. Speed was life and the mission commander set the profile.

At normal Warbird cross country cruise altitudes of say 10,000 feet, without racks and externals, the P-51B/C/D with a 1650-3, 9 or -7 can be safely run at 46" and 2700 RPM all day long but it also burns 90GPH. At lower RPM and leaner mixture 40" with 2200 RPM and it will scoot along at 325mph with a burn of 66 GPM. That is conservative because Warbirds do not carry Guns, ammo or aft fuel tank so the flight is conducted at 900-1000 pounds less than the War TIME recommendations.

ANY of those cruise settings discussed above at 46" is safe for Warbird operations - even without yanking the guns, ammo and fuselage fuel... for 130/150. So for crappy expensive stuff today the settings will change to optimize burn quality without going too Lean.


In fact, we can disagree and it's fine. I know what the guys I know who own them say and what the veterans who flew them say, and that's good enough for me. If it isn't for you, well then - OK.

If you knew what to ask, and if you comprehended the answers to each specific question - they (the veterans and the Warbird pilots) would agree what I posted then and what I just posted in this reply. "They" operated by the 'Book' rather than each seek a 'different approach for safe operations and economy. I posted the wartime RANGES of cruise options, I (Shortround first) posted the Recommended Cruise options to maximize range and posted them for Ranges of Take OFF Gross Weights ranging from 10,200 pounds to 11,600 pounds

Let's say we both think it was a very good fighter, even great, and let the details alone betwen us. I'll continue to think what I do and so will you. Neither one detracts from the combat record or the legacy, so let it go at that.

I'll allow they cruised fast on fighter sweeps away from bomber escort, but I'll just laugh at the thought 410 mph cruise. Didn't happen as far as I know. But out of completeness, I will ask next weekend when the vets show up again for the "Little Friends" event.

Please take the time to read, then re-read what I posted. Print off Post 16 or this post. Take what I posted, and re-posted, on a sheet of paper and ask - "Do you believe this? Is it contrary to your experience - if yes, what is different and what were the circumstances? Write the differences down as well as the author of the comments.

Please quit being condescending. It's all I can do to be civil already. Just say what you're going to say and leave out the barbs and put downs. Things will be much friendlier that way.

Greg go back to your earlier post (#36) where you opened it up with "lets use Logic here" as if you were talking to a retarded child who didn't understand the depth of your brilliance - to illustrate a point that was not even the topic framed in context. It went downhill from there.

Your opening to the world of debaters on this subject - after you missed what Shortround said and what I said - was:

Here's another try at logic ...

Let's look at this from a planning point of view. Nevermind startup, taxi, takeoff, and forming up, a B-17 normally cruised at about 185 mph. It is 580 air miles from London to Berlin and back, or 1,160 miles round trip with no allowance for turnaround. 1,160 miles divided by 185 mph give a mission of 6.3 hours.

Take this statement and the rest of your post to Bud Anderson if he is there, hand it to him and ask for a comment about your logic from 'a planning point of view'.

Write the comments down, Report back.

 

[grampi]

I love this quote from Johnson about his climbing duel with the Spitfire. Later in Thunderbolt, (page 176 according to Google book search) he talks about how the paddle-blade propeller helped the Thunderbolt's performance. He said after he got the paddle-blade propeller he had a climbing dual with a Spitfire 9b - the same model that out-climbed his P-47 earlier, and this time the Thunderbolt was the faster climber.

I don't see a P-47 outclimbing a Spit regardless of what prop it has on it...the power to weight ratio just doesn't support his claim...

 

[drgondog]

Friends,

I think we're too hung up on a number. There is nothing magical about 380 MPH.

Only one person can't shake the '380 mph' emergency cruise speed notion or why it is one of many points of data in the P-51D Operating manual.

The tactical advantage doesn't come in a number it comes in the status of being "fast enough". My premise is that entering into the combat area fast, before contact with the enemy is a huge tactical advantage.

No question here but a typical tactical scenario in the ETO is that a fighter Group of three squadrons were 'normally' deployed around one and maybe two 'boxes' of bombers. In mid 1944 a box would be approximately 50 B-17s or B-24s with one full Bomb Group and part of another from the same Bomb Wing.

That Could look like - one squadron flying as much as 4-5000 feet above the box, one flying off to one side and one flying on the other side if the Box is in an interior position. If the Box is a lead box, the one of the squadrons might be running from one side to 5-10mi out in front and back. Any squadron tethered to the bombers is running approximately 220IAS, which at 25000 feet is ~320-350mph TAS, which forces P-51s to 'Ess'

At 220IAS the fuel burn rate is about 10% higher than 'max cruise with 110 tanks and fully loaded P-51D - at 11,600-700 pounds GW at TO. in order to stay with the bombers they are assigned to. Any fighter squadron on a Sweep or an Area Patrol to block inbound enemy fighters will still fly around 200-220mph IAS but more in a straight line and covering a lot more ground. As the fuel is burned down the cruise speed (as you know) will increase at same power settings.

'They' can't afford the luxury of running much above Max Range Cruise on a long mission, and they have to really try to hold on to the external tanks to empty if possible and reserve all internal fuel except 25+ gallons of burn off, plus some 10 gallons on warm up and take off in the left main. If they get in a fight too early and have to punch 110's with a lot of fuel remaining, they have to go home before completing the escort assignment.

The squadron commanders were disciplined and sent flights or sections frequently when bouncing smaller numbers of 109s or 190s, holding the rest of the squadron in reserve and not punching tanks. Occasionally a really large batch of enemy fighters are spotted and sections, then whole squadrons engage while calling for help from the other squadrons.

At this stage, you aren't going to be be using any fluid injection, and you are not going to be using a power setting that requires a tear-down at the end of the flight. In other words, you aren't going to uses "war emergency" power.

Unless the situation is dire Military Power was the first run up on the throttle and RPM. Everybody was aware of not getting home on a bad engine after WEP..

You also aren't going to use a power setting that doesn't give you enough endurance to do what you want to do. You will use the highest power setting that allows you to do what you need to do. You might call that a "fast cruise". You might call it something else. The Mustang, because of its low drag, could go faster per unit of power and fuel consumption than most or all of its peers/adversaries. Going into the battle fast in a Mustang is crucial because the plane is heavy in relation to its power. Not being caught low and slow is crucial to survivability in a P-51. If a P-51 is bounced while in eco-cruise, all of its performance advantages are gone. Conversely, if the P-51 maintains a continuous speed (none dare call it "cruising") in the combat area which is above the maximum continuous speed of its adversary's, the adversary will be at a significant disadvantage unless the adversary has a substantial altitude advantage. It is unlikely the adversary will have a position advantage at the Mustang's 6 because the Mustang already passed that area faster than the adversary could go. If you start with that speed advantage, add in a numerical advantage and the advantage that the P-51's main job is to protect bombers, and the Luftwaffe's main ob was to shoot down bombers, it is easy to see how the P-51 had the second highest score against enemy aircraft for US fighter types. (#1 was the F6F Hellcat which was slower than the Mustang, but was fast enough to do what it had to do.)

Because of the nature of the range requirements for most deep strikes, fuel management was king. The eyes were depended on because the P-51 needed to cruise in the 4-4.8 mile per gallons per hour range of fuel consumption (60-70 gph) while fuel remained in a 75/110 gallon tank. That 'selects' the Cruising speed you think you can afford An 8:05 hour mission is the longest I am aware of in the ETO (admittedly a relatively small sample sixe)- but even that translates to 59+ gph. The Mustang can't go very fast at that average burn rate on any leg of a mission when the rock bottom is around 52gph

 

[Shortround6]

part of the problem in reconciling cruise speeds and range compared to other fighters is that only about 3 fighters ever took on really long range missions at high altitudes, fighter missions that is. The Spitfire took on long range photo recon missions.

Here is a graph from Mike Williams site for power required for different speeds and altitudes.

Please note that using 600hp the speed could vary from just over 260mph at 5,000ft to just over 350mph at 35,000ft. Granted the 35,000ft altitude is pretty useless for missions lasting hours due to oxygen consumption and cockpit heating and other health issues for the pilot. Also the engine will use a bit more fuel to make 600hp at the higher altitudes because it is powering the high gear of the supercharger. But a 23% increase in speed (and thus range) for only a little more fuel burn? At a much more useful altitude 25,000ft the Mustang can be doing 325mph on 600 hp?

The only fighters that could really cruise that high for long ranges were ones with two stage superchargers. Either turbo or mechanical. Single stage engines had to be pushed a bit more to make a reasonable speed (Cruising at much under 200mph indicated or 270-280mph true probably wasn't a good idea). A P-39Q needed 2600rpm and 26in MAP to do 222mph indicated at 20,000ft and 60 gallons an hour. Trying to fly 5,000 ft higher means pushing the engine harder. For some of the single stage aircraft with small fuel capacities it also came down to using the fuel climbing or for cruising. A P-40 with a drop tank (or bomb) could use 14 gallons of fuel climbing from 20,000ft to 25,000ft and maybe that 14 gallons would be better spent cruising at level altitude for 15-20 minutes.

For the Americans that pretty much means 5 aircraft and four of them were much bigger, had much more drag and sucked way more fuel per hour than the Mustang.
The British had pretty much the Spitfire with a two stage supercharger (single engine) and nobosy else had much of anything in production so comparisons become rather difficult.

 

[pbehn]

I had this in mind when I made my previous posts.
German Jet Encounters
The second story does not give the type of detail preferred by members of the forum (it is a story) but it does describe the problem of matching cruising speeds. In this case mosquito bombers with P51 escorts unusually in this case the bombers best cruising speed was faster than the fighter at least at the start of the mission. Anyway all the boys got home so a good job all around.

 

[GregP]

Well we had a slow day at the museum due to the fact that almost everyone was flying at airshows. But Seteven Hinton Jr. was there working on Voodoo and I asked him about WWII P-51 cruising speeds when escorting bombers and otherwise.

He grew up around the WWII aces, was raised in a P-51 or three, and is your current and six-time in a row National Champion in the Unlimied Gold racing class ... in P-51-based racers. His response was classic.

He said bomber escorts in P-51s and pretty much everything else flew around 190 - 220 mph until being bounced, seeing the enemy, or hearing about enemies in the same general area over the radio. So I was a bit optimistic when I said maybe 250 mph. He allowed they might push it up to 280 - 300 mph when alone, not escorting, and expecting combat, but otherise they'd fly 220 - 250 mph even when alone.

I asked about a close to 400 mph cruise at max continuous, which I understood was 42" and 2700 rpm. He said we must have been reading some unofficial manuals. He said max continuous is 42" and 2400 rpm and the stock WWII issue P-51 wasn't going to get aywhere NEAR 400 mph at that power.

This is coming from a guy who knows his way around stock as well as modified P-51s, and grew up with Bud Mahurin and other WWII aces ... who helped him solo and learn to fly P-51s.

Any argument for 400 mph fantasies falls on absolutely deaf ears here but again, in the interests of completeness, I will still ask the veterans yet again next weekend. I already know what they will say, and I suspect most of the forum readers in here already do, too.

I'll check back in next weekend to post what I hear from direct questions of veterans who were there and flew the escort missions. They've been presenting there for more than 40 years, so the subject is already rather well known.

Sloooowwwwlllyy now Bill, get the 400 mph cruise out of your head.

 

[Greyman]

Correct me if I'm wrong, but 'Cruising' means the engine settings which will allow continuous operation for an indefinite period (of course this can be further categorized up for maximum endurance, maximum range, different speeds, etc.).

For the purposes of comparing various cruise speeds to every other aircraft (which I think is what most of us are generally interested in here), it's unfair to the Mustang to pigeon-hole it and restrict the definition in its case to 'the speed at which it must escort bombers to Berlin and back'.