Zoom climb

Yes Greyman, Cruise power is NOT maximum continuous power, but COULD be ... it certainly is NOT when you are flying a long escort mission and time in the air is important. On shorter missions, say maybe Oct 1944 onward, the mission were getting shorter ... and thinga could change.

If there were not a war on, and if you weren't constrained by needing to fly a long distance, the P-51 is certainly capable of cruising in the mid-to-upper-mid 300s. That assumes the fuel burn and engine wear are acceptable and, in a war the engine wear is not a factor as the government CAN overhaul engines. The operative factor would be what the mission is. If you need to be ariborne for 7 - 8 hours, you are not flying at 380 - 400 mph in a P-51D with drop tanks on it. If you are escorting bombers you REALLY aren't cruising that fast or else you will never make the range required.

If the mission is 1200 miles and if your fighter flies twice as fast as the bombers ... but has to protect the bombers ... then your mission is 2400 miles while the bombers fly 1200 miles. Simple math, no surprises. The escorts didn't want to be flying 180 mph, but they also wanted to S-turn above the bombers, not fly in long ellipse-type circular paths.

If the P-51s were on a fighter sweep, they could cruise whereever the fuel they had would take them at the acceptable power selected. I they were clean, maybe 365 mph on a short mission. If they had tanks, bombs, both, or a longer mission ... no way. In Europe the weather is usually bad at certian times of the year, ay least for aircraft operations, and capable of being so any time. Nobody wanted to waste fuel he might need when returning due to weather. Fuel was an important factor.

The PLANE could probably do it, but there was no logical reason to go that fast on escort and no reason to court engine failure by cruising at high power levels beyond best-range cruise. Nobody with an ounce of brains wasted gasoline unless he had a reason. If he HAD the reason then yes, push it up as far as you want. Push it too far and join Colonel Hogan and Sargeant Schultz in Stalag 13 just from fuel exhaustion or engine failure. That ruins your day.

I do NOT question the P-51's ability to go fast when going fast was desired; it will and still does. I question the real-world decision to go fast when NOT needed and on the outbound leg of a long mission of any sort. Maybe if you HAVE the gas and are headed home and don't have to stay with the bombers because you picked up a relief squadron, then they might well get pretty fast to get back to the pub.

But if they hadn't seen an enemy fighter, they would not have dropped the tanks unless they were paper tanks. Metal tanks were a commodity you saved when you could. If not, well it WAS a war.

You know, maybe Stevo is mistaken and the veterans will say differently next week. Could be. I have been taken to task in here before for quoting the veterans who were there and will just ignore that going forward. In my opinion, they are the ONLY guys who KNOW, sort of like the Beatles are the ONLY people who know what went on in the back of their limosine. Everyone else is making assumptions that might be valid and might not be, including me.

So I could be off-base here and, if so, I'll admit it when I find out. Everyone makes mistakes including me, Bill (not often in my experience ... unfortunately for me), and anyone else. So, if I step in it, I'll own up to it, in here, and say I was wrong. It happens.

Bill seems to think I somehow have it in for him when I post something he disagrees with and he's mistaken. He is right most of the time and COULD be this time too. If so, the crow served up is mine, not his.

If anyone is interested, I added another couple of pics to the Planes of Fame Update thread. They had another week of polishing the Sabre ... and it shows. Our F-86F and MiG-15 bis are gone for 2 - 3 months on continuous airshow duty, so I can't update the paint and markings pics yet.

GregP said:

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.

Greg - one simple question. Do you understand the difference between INDICATED AIRSPEED and TRUE AIRSPEED? Do you understand that Steve Hinton Jr and every expert in the P-51 or any other fighter is referencing the instrument in front of him - which in WWII was an airspeed indicator referencing ONLY Indicated Airspeed based on air pressure recorded by pitot tube?

Go to pg 59 of the P-51D-5 Manual AN 01-60JE-1 which is the Operations Planning table for 75 Gallon tanks (110 tables removed).

The solid black line is six rows up and underscores 25000. That is the altitude reference. Go to the far right "Column V" for maximum range data settings with 419 gallons to achieve 1820 mile range.

There are six columns which are RPM, I.A.S., Mixture, MP, GPM and T.A.S.
25000 = 2250 RPM, 200mph IAS, Auto Lean, FT, 57gpm and 295mph TRUE AIRSPEED

Over on the far left is "Column I" for Emergency Cruise for 1000 miles and 419 gallons
25000 = 2700 RPM, 255mph IAS, Auto Rich, 46", 115gpm and 375mph TRUE AIRSPEED.

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.

With the greatest respect to Steve Hinton, the manual was Issue, not unofficial, that data was nearly 100% the same for the P-51B-10 manual and the Manual dated 1944 stated - Upper Left Corner of the Table that for the P-51D-5 with 1650-7 engine that Normal Rated Power settings are:
2700RPM, 46" MP, High&Low Blower, AR (auto rich) CONT. (max duration), 109 to 106 GPM.

I suspect Steve is basing his comments about both the fuel type differences and Caution based on Warbird experience.

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.

245mph IAS/375 TAS on Max Continuous at 25000 feet, 255IAS/390 mph TAS at 30,000 feet WITH external 75 gallon tanks

280IAS/410 TAS on Max Continuous at 25000 feet, for 680 mile range with 269 gallons of fuel.

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.

Ask the question the right way, Greg. Remember the difference between TAS and IAS at 25000 feet (or even more pronounced difference at 30,000 feet where some of the escort missions were flown.

Put into context for Steve - because if the P-51 was escort cruising at 190mph TAS. they could never CATCH a fully loaded B-17 at 25000 feet

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

Click to expand...

See the above - I sent Steve a Facebook PM ad will send Chris Fahey the same note.

Nothing derogatory on you - just what I explained to you multiple times so that he had the context of the questions, the reference and my suggestion that you may not know the difference between IAS and TAS

EDIT - my PM was to Steve Hinton, Sr as well as Chris Fahey another former F-16 driver that flys may shows with Steve Hinton Jr in either the Mig 15, the F-86, the P-51A, the P-51B and the P-38's. For what it is worth, Chris agrees the P-51B and D Operating Manual for Planning Tables as a 'Guide' but each pilot has a tendency to cruise at different altitudes -and RPM/Boost settings - to suit themselves. I haven't gotten a reply from Hinton, Sr but Chris will chat with SteveO when he gets back today from the Idaho air show and the F-86F to see what Steve 'heard'.

There seems to be a bit of confusion between max cruise and max continuous.

Max continuous was the maximum amount of power the pilot was supposed to use with an unrestricted time limit. The ONLY restrictions being engine temperature, oil temperature and running out of gas or oil.

Max cruise is a little fuzzier, as in many instances, max cruise was also done at rich settings. It is subject to the same four restrictions as above and will give more range (in some cases, much more range).

Some planes had an "economical maximum" given on their charts which was the max power using lean mixture.

And here we have another source of possible confusion. Late P-51s had a 3 position control for mixture, idle cut-off, normal and rich. Early P-51Bs had 4 position control, idle cut-off, auto lean, auto rich and full rich. When the switch over between controls was made or if there ware one or more intermediate mixture controls.
Were the pilots "cruising" using lean or normal, were they actually the same? Or was the "normal" somewhere between auto lean and auto rich and the later "rich" equal to "full rich" ?

talking to a veteran who flew a P-51B with the 4 position control on a V-1650-3 engine might give a different answer than a veteran who used the 3 position control on a V=1650-7 engine only a few months later.

Shortround6 said:

There seems to be a bit of confusion between max cruise and max continuous.

Max continuous was the maximum amount of power the pilot was supposed to use with an unrestricted time limit. The ONLY restrictions being engine temperature, oil temperature and running out of gas or oil.

Max cruise is a little fuzzier, as in many instances, max cruise was also done at rich settings. It is subject to the same four restrictions as above and will give more range (in some cases, much more range).

Some planes had an "economical maximum" given on their charts which was the max power using lean mixture.

And here we have another source of possible confusion. Late P-51s had a 3 position control for mixture, idle cut-off, normal and rich. Early P-51Bs had 4 position control, idle cut-off, auto lean, auto rich and full rich. When the switch over between controls was made or if there ware one or more intermediate mixture controls.
Were the pilots "cruising" using lean or normal, were they actually the same? Or was the "normal" somewhere between auto lean and auto rich and the later "rich" equal to "full rich" ?

talking to a veteran who flew a P-51B with the 4 position control on a V-1650-3 engine might give a different answer than a veteran who used the 3 position control on a V=1650-7 engine only a few months later.

Click to expand...

SR - the Mixture Control could be set at a Auto Rich or Auto Lean but the pilot was looking at the Manifold Pressure to fine tune any position while also adjusting RPM and Throttle - until satisfied - then lock those settings down. Everything within the span of your left paw... so it really didn't matter if there was a Full Rich notch past Auto Rich.

Depending on altitude and mission - the RPM at cruise for example could be from 1600RPM (say low speed, low burn for maximum loiter time) all the way to 2700 RPM and 46" for Normal Power Emergency Cruise.

The reason pilot recollections are all over the place is that they are flying all over the place from one mission to another - and the Pilot is trying to recall one mission long range and flying high cover at 30,000 feet, another is a fast cruise untethered by bomber escort, another is a low level fighter bomber sweep - but ALL will start with the Operating Manual that you posted 'way back' and be GUIDED by the altitude and mission range requirements.

Thank you, I didn't know if it made a difference or not.

Somewhere I had down loaded a Manual for a P-51B-1 but the flight charts are a mess. ALL the numbers are in red which usually means the numbers are calculated or estimated while black numbers mean they had been checked with flight tests. There are columns for IAS in MPH and IAS in Knots but they make no sense as the speed in knots is often higher than the speed in MPH. Unless they put the numbers for true air speed in the column labeled IAS Knots.

For instance in Column II of the chart 2100rpm and 41 in at sea level is "supposed" to give 285mph IAS and 275 Knots IAS but at 3,000ft the same rpm, pressure and IAS on MPH is 285knots IAS (the same rather than 10 low) at 6,000ft the same rpm, pressure and same 285mph IAS is now 295 knots, at 9,000ft the 2100rpm/41in/285mph IAS combo is 310 knots. 12,000ft and 2200rpm/41in/290mph IAS is 330knots, at 15,000ft it gives 2250rpm/41in/295mph IAS for 350knots IAS and at 20,000ft 2500rpm/F.T/ 290mph IAS is 375 knots IAS.

The rest of the charts are similar.

This is from T.O. No. 01-60JD-1 and is dated July 1st 1943.

SR - the difference between TAS and IAS is a function of Pressure and Temperature which as you know changes nearly linearly from SL through ~ 37,000 feet (CRS). The density changes, the dynamic pressure changes with altitude. Look at the Charts and IAS = TAS at SL but at 25000 feet IAS on the instrument panel is 30% less that the True Airspeed at 25,000 feet.

On several Flight Tests validating the operations Planning entries in the manual, the actual and calculated and IAS TAS data are often in () to compare against the Charts.

At 10,000ft in Betty Jane the following was noted:
36"MP 2,350rpm Normal Cruise IAS was 220kts 64gph auto lean (shadin fuel flow meter)
40"MP 2,500rpm High Cruise IAS was 235kts 72gph auto rich (there isn't much difference between 40" and 42")

I am running 40" 2,500 for doing loops with an entry speed of 270kts @3 1/2 - 4Gs . It is possible to do loops with a normal cruise power setting but it gets slow over the top. At 40" 2,500 it carries a bit more energy over the top with more control authority. On a normal day from 8,000ft it takes around 1,500ft of diving to attain 270kts. Through the backside and out of bottom of the loop at around 250kts you can zoom climb for about 20-30 seconds back up to 8,000 but the speed and energy diminish quickly. We do not run high power settings for acro. Some still do and the added inches of manifold pressure does help maintain momentum a little better than the 40" I use for vertical. We are running right around 7,500lbs so we are considerably lighter than a wartime airframe. hope this helps

jim

Thanks Jim.

The warbird 'lite' versus the Manual 'heavy' does draw several important contrasts. I suspect that the fuel octane from late WWII also influences the nuances on cruise setting for max loiter, max range and Max Continuous from The P-51D operating Manual and Tables?

The P-51D 'book Tables' for racks only, 9600 pounds medium cruise settings is 2400/36" for 270IAS mph and 290Mph/252kts TAS at 10,000 feet. So reasonably close for to same performance you are flying for 7500 GW

I said I'd check back in here when we had our "Little Friends" presentation and we had it today, so I'm back.

I asked the presenters how fast they cruised the P-51s in the Pacific both with and without bombers to escort, and whether or not they knew the same information about missions in the ETO. Not surprisingly, the subject had come up at the last meeting of WWII escort pilots a few weeks earlier.

According to three of our presenters, they cruised the P-51s (mostly P-51D's) at 220 mph, which turned out to be somewhere around 29" – 30" and 1,700 – 1,900 rpm depending on configuration. Every hour for about 10 minutes, they'd run the engines up to 35" – 40" at 2,400 rpm and auto rich to make sure they didn't foul the plugs, and then go back to 220 mph or so. They said that the P-51s in the ETO did pretty much the same or slight slower 190 – 210 mph or so, clearing the plugs for 10 minutes every hour before going back to lean cruise.

I asked about 320+ mph cruise and most laughed and said they'd never done that or heard of that. One asked if I was a video game player. I told them it was a question in a WWII aviation forum on the internet. The general consensus was that the only excuse for going over max continuous to clear the plugs was getting bounced or expecting imminent combat, and they'd rapidly go back to low cruise once things cleared away from combat.

So they pretty much said what they've said when this subject has come up before in past "Little Friends" presentation made by WWII combat veteran pilots of P-51s. However, this cloud might have a silver lining for both Bill and me. I didn't specifically ask, so I made an assumption that they guys were talking IAS. Suppose they were flying at 20,000 feet at 220 mph IAS with an OAT correction of 2%. It turns out TAS would be 308 mph under those conditions. So it is possible that both Bill and I are right or wrong.

They almost certainly did NOT cruise at 300 + mph in P-51Ds if we are talking IAS, which I was talking, but they could be cruising in the low 300s TAS. I was talking IAS because that is all the pilot sees on his instrument panel. The 505 mph dive limit is IAS and it gets lower with altitude and the speeds in the handbook for IAS almost never approach the maximum.

So I can understand Bill's 300 mph claim. But the pilots at our presentation from all theaters for the last 9 years I have been going and hearing the Q A have never supported seeing cruise speeds above about 250 mph and mostly not that fast. I never asked before about altitude, rpm, and MAP, but I'm sure that if they had a short mission, and pushed the cruise up to 260 mph IAS at 25,000 feet, they'd see somewhere around 390 mph TAS at 20,000 – 25,000 feet.

Nobody in the last 9 years had ever said they cruised at 260 mph (IAS), but I'll allow it was possible if you weren't going to escort someone a long way. I'm not sure any ETO bombers warranted cruising that fast, ever. I don't think P-51s escorted Mosquitos very often and the B-17, B-24 and Lancaster would not require cruising that fast even on their best days.

I think we've had some harsh words for nothing since I was always talking IAS. I can't speak for Bill, but It is likely he was using TAS numbers from the charts.

This is as funny as the USAF saying the SR-71 goes Mach 3.0 at high altitude. The SR-71 could get to 2,000 mph TAS and, at high altitude, the speed of sound is 660 mph. 2,000 divided by 660 gives Mach 3.03 when you run the numbers, but the IAS is still about the same as the SR-71 sees at 10,000 feet and max speed since the same IAS generates the same heat or thereabouts. 850 mph IAS at 70,000 feet will give around 2,000 mph TAS or Mach 3.03 and that sounds a lot faster than 850 mph, doesn't it? It's all about image.

The real WWII pilots never saw 380 mph cruise on the airspeed indicator and laugh when you bring it up. Really. NOBODY cruises at max possible speed on a long range mission. The two are incompatible with one another. Max cruise will NOT get you max range and the Breguet Range equation ain't all that far from wrong.

That's pretty much all I have to say on it. Not too interested any further since the P-51 veterans as well as current P-51 pilots, including some really quite qualified guys, say it didn't happened in service. But unless you're careful with your terminology, you can be both right and wrong when talking speeds.

I never bothered to flight plan TAS when flying a Cessna 172 because everyone at the FAA service center will laugh if you file a C-172 flight plan at Mach 0.17 ... I did it only once with Albuquerque Center and it made their day. They were laughing uproariously and I expected that. When I got to "souls on board," I also filed for "One plus an athiest" and got another round of laughter. But I got willing flight following that day since it broke up the boredom.

GregP said:

I said I'd check back in here when we had our "Little Friends" presentation and we had it today, so I'm back.

I asked the presenters how fast they cruised the P-51s in the Pacific both with and without bombers to escort, and whether or not they knew the same information about missions in the ETO. Not surprisingly, the subject had come up at the last meeting of WWII escort pilots a few weeks earlier.

According to three of our presenters, they cruised the P-51s (mostly P-51D's) at 220 mph, which turned out to be somewhere around 29" – 30" and 1,700 – 1,900 rpm depending on configuration. Every hour for about 10 minutes, they'd run the engines up to 35" – 40" at 2,400 rpm and auto rich to make sure they didn't foul the plugs, and then go back to 220 mph or so. They said that the P-51s in the ETO did pretty much the same or slight slower 190 – 210 mph or so, clearing the plugs for 10 minutes every hour before going back to lean cruise.

Greg - that is 220mph Indicated - not True Airspeed. and 190-210mph Indicated - not True airspeed. A B-17 cruises at 150 mph IAS, which at 25,000 feet is between 215 and 225mph True Airspeed depending on temperature.

I asked about 320+ mph cruise and most laughed and said they'd never done that or heard of that. One asked if I was a video game player. I told them it was a question in a WWII aviation forum on the internet. The general consensus was that the only excuse for going over max continuous to clear the plugs was getting bounced or expecting imminent combat, and they'd rapidly go back to low cruise once things cleared away from combat.

Greg - you have a challenge in a.) absorbing what is being discussed and b.) putting it in context. Nobody stated, implied or otherwise communicated that cruising at 320mph Indicated was performed as a matter of practice - ONLY that the standard Operating Tables Present a cruising speed of 375mph TRUE AIR SPEED for 2700RP< 46" Max Continuous Power setting with two 75 gallon external tanks and 10,700 pds GW at Take Off with 420 mile operating range (no allowance for WU, TO, Climb, etc)

So they pretty much said what they've said when this subject has come up before in past "Little Friends" presentation made by WWII combat veteran pilots of P-51s. However, this cloud might have a silver lining for both Bill and me. I didn't specifically ask, so I made an assumption that they guys were talking IAS. Suppose they were flying at 20,000 feet at 220 mph IAS with an OAT correction of 2%. It turns out TAS would be 308 mph under those conditions. So it is possible that both Bill and I are right or wrong.

No, Greg that is not correct - you are re-writing history. REPEAT - go back and look at the discussions, Greg. I brought to your attention the difference between IAS and TAS early in the discussion. The AN 01-60JE-1 P-51D-5 Flight Operating Instructions dated April 5, 1944 contains ALL of the data that I have presented to you and the Appendix II "Flight Operating Charts" the THE BOOK for P-51D operations based on flight testing at Wright Pat, and further validated by the series of tests run on June 15, 1945 in a P-51D-15 by Don Gentile.

They almost certainly did NOT cruise at 300 + mph in P-51Ds if we are talking IAS, which I was talking, but they could be cruising in the low 300s TAS. I was talking IAS because that is all the pilot sees on his instrument panel. The 505 mph dive limit is IAS and it gets lower with altitude and the speeds in the handbook for IAS almost never approach the maximum.

No, you were NOT talking IAS Greg. Go back and look.

So I can understand Bill's 300 mph claim. But the pilots at our presentation from all theaters for the last 9 years I have been going and hearing the Q A have never supported seeing cruise speeds above about 250 mph and mostly not that fast. I never asked before about altitude, rpm, and MAP, but I'm sure that if they had a short mission, and pushed the cruise up to 260 mph IAS at 25,000 feet, they'd see somewhere around 390 mph TAS at 20,000 – 25,000 feet.


I think we've had some harsh words for nothing since I was always talking IAS. I can't speak for Bill, but It is likely he was using TAS numbers from the charts.

The BS flag is thrown. I gave you line by line, column by column the data contained in the Appendix II. The Format is consistently "RPM","mph in I.A.S", "Mixture","M.P.", "GPH". "mph T.A.S.";

Example given for 25000 feet, 75 Gallon externals, 10,700 Pds GW, for Max Continuous (NOT ESCORT VALUE - ONLY MAX CONTINUOUS POWER as ShortRound began the DISCUSSION - I.e NOT WHAT DID AS A MATTER OF STD OPS BUT WHAT WAS POSSIBLE !!!!!!!!!!!!!!!

So, 2700RPM, 255mph IAS, AR, 46"MP, AR, 115GPH, 375mph TRUE AIR SPEED. Lower left, 1st Column.

Example Given for MAX RANGE, Far Right Column, Lower Right
For 25000 feet, 1820 miles Range, 75 Gallon Tanks, 10,700 pds GW:

so, 2200RPM, 200 IAS, AL (auto lean), FT, 57GPH, 295mph TAS.


That's pretty much all I have to say on it. Not too interested any further since the P-51 veterans as well as current P-51 pilots, including some really quite qualified guys, say it didn't happened in service. But unless you're careful with your terminology, you can be both right and wrong when talking speeds.

You never got the difference 'right' in any of the past discussions

I never bothered to flight plan TAS when flying a Cessna 172 because everyone at the FAA service center will laugh if you file a C-172 flight plan at Mach 0.17 ... I did it only once with Albuquerque Center and it made their day. They were laughing uproariously and I expected that. When I got to "souls on board," I also filed for "One plus an athiest" and got another round of laughter. But I got willing flight following that day since it broke up the boredom.

Click to expand...

You are trying way too hard to recover, Greg. If you had simply pulled out the Operating Manual used as the reference for my data and remarks - you might have figured it out earlier.

GregP said:

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.

Greg Here is VERBATIM what I said on this two days before this post by you

"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 200-220IAS, which at 25000 feet is ~320mph+ 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 220IAS 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 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..


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.

Click to expand...

Can to find a mention of 400mph cruise in the context of a typical escort discussion at either 25000 or 30000 feet? Can you see a differentiation between IAS and TAS terminology? Do you see any such presentation to SteveO so that he understood what we were talking about?

I didn;t reasd tyhi thread from Last Sunday until last night, so whatever you posted twp days agao, I didn't read. Considering teh way you say it, I won;t go back and do tyaht either.

You apparently didn't read my post either, the guys answered for both escort and general flying when no escorting. They didn't even cruise at 260 IAS when alone, there being no point to going faster until necessary. Ad I very cealrly stated what Ia sked ... whichw as, "How fast did you crusie the P-51 when escorting bombers and when not flying escort?"

They all answered about 220 mph with 10 minutes in auto rich each hour to keeep the plugs from fouling.

So while tyhere might be a few people out tehre who did fly fast for a reason, tghey were cruising aorunf at 380 mph or 400 mph or whatever high speed you are touting. They werer cruising to save fuel, save the engines, and get the job done ... exactly as I said many pages back.

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.

Yesterday, "zoom" climbing out of a loop back up to 11,500 from 8,000

And the day before I was flying the 24 and noted the cruise settings, you can see for yourself it's pretty slow




At altitude your true airspeed will be higher depending on temperature, air density and winds aloft. The bombers topped out at 200 no matter how you look at it...that's why the fighters flew an S pattern over top of them. A fully loaded mustang with drops would be lucky to get over 200IAS as well...indicated. Certainly no where near even 300TAS.
Jim

GregP said:

I didn;t reasd tyhi thread from Last Sunday until last night, so whatever you posted twp days agao, I didn't read. Considering teh way you say it, I won;t go back and do tyaht either.

You apparently didn't read my post either, the guys answered for both escort and general flying when no escorting. They didn't even cruise at 260 IAS when alone, there being no point to going faster until necessary. Ad I very cealrly stated what Ia sked ... whichw as, "How fast did you crusie the P-51 when escorting bombers and when not flying escort?"

They all answered about 220 mph with 10 minutes in auto rich each hour to keeep the plugs from fouling.

And SteveO responded 190-220 and I said from 200-220IAS. Pick one.

So while tyhere might be a few people out tehre who did fly fast for a reason, tghey were cruising aorunf at 380 mph or 400 mph or whatever high speed you are touting.

GregP - I think you are trolling - at least being terminally dense. What I stated is that the MANUAL Presents a cruise speed (high) and cruise range (low) at 2700RPM, 46", Auto rich, 108GPH 410mph at 25000 feet with only external racks, 375mph TAS with same settings at 375mph TAS - both at 25000 feet. I dis not assume or state that anyone Did That - only that the Manual says that you CAN do that at Max Continuous Power.

They werer cruising to save fuel, save the engines, and get the job done ... exactly as I said many pages back.

Yes, Greg, as everyone has said, I have said, as well as presented data to show the difference between 480 miles or range and 1820 miles of range.

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.

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I don't know how old you are Greg - but I have been talking and listening to my father and his friends - and the friends I have made on my own since at least 1950 - which gives me 65 years of listening, researching, asking questions, researching, asking more questions and forming opinions based on what many of the best fighter pilots remember.

You still have yet to respond with Your versions/variances of the P-51D Operating Manual which departs from what I have stated/referenced, the reference document, the page numbers and the cruise values for the load outs and range conditions as well as altitude. You are non specific and wander between IA and TAS.You remind me a lot of Soren, when confronted. You get on a soapbox and grab a megaphone and recite chapter and verse of anecdotal recollections from people you don't name (except Steve Hinton Jr (SteveO) and then you contradict him with new references.

Settle this - trot out your numbers for a typical long range mission to Berlin with 75 gallon tanks.

When you quote your version, Pick a 1944 manual for P-51D Operations recommendations and state the RPM, IAS, Mixture, Manifold Pressure, Gallon per hour fuel rate and True airspeed for those settings.

Compare those with examples I presented on posts 31, 64, 76, 82, 91 and 92. and show how and where I was wrong and you were right.

Never let reality get in the way of a good manual...I've flown quite a few WWII airplanes and they continually fall short of the book numbers. Even lightly loaded I am continually amazed they achieved the results they accomplished. I see and talk to veterans every day, and particularly the bomber crews, say every flight was marginal. Trade bombs for fuel or fuel for bombs.

Jim

jimh said:

Never let reality get in the way of a good manual...I've flown quite a few WWII airplanes and they continually fall short of the book numbers. Even lightly loaded I am continually amazed they achieved the results they accomplished. I see and talk to veterans every day, and particularly the bomber crews, say every flight was marginal. Trade bombs for fuel or fuel for bombs.

Jim

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Jim - I know you are right. Having said that, the flight tests were flown to develop an Operating Guide for pilots new to the airframe and served as a Guide for planning purposes. If a particular ship or ships wasn't making a cruise speed by the book, a prudent mission commander adjusted accordingly.

I spent many hours listening and cross examining dad and his friends to 'try' to understand the variables before I got my degrees in Aero - then realized afterwards that it was all about 'It depends' as contrast with a hard throttle/rpm/MP as each airframe and engine was a different beast.

Simple question - when you were new to the 51 was the Operating Guide useful - or outdated because of different constraints imposed by severe financial penalties for running on the edge of the 'Book' recommendations and losing an engine or airframe? or tribal knowledge of the system after 70 years?

Performance figures from tests of export/Lend-lease RAF/Commonwealth aircraft seem to be a bit more realistic for real-world performance compared to standard USAAF/USN test results applied to planning charts. (short of cases of operating out of spec -particularly overboosting, though that seems more common in ammended notes and such rather than actual recorded test figures)

Jim - I just noted your comment on 200IAS not 'being anywhere near 300TAS" - I wonder if you are thinking KTAS?

at 25,000 feet, 200 mph IAS is 295mph TAS at standard Temp/Pressure.
At 30K, 195mph IAS is 315mph TAS. 190-220 mph IAS is ~283mph to 323mph TAS

A B-17 SOP cruise was 150mph IAS at 25,000 - which at STP is about 220mph TAS.

BTW I noticed on your panel that you were indicating about 156Kt - do you know when that airspeed indicator was put in your 51 to replace the standard airspeed gage?

So, at 10,600 ft the 156KTS on your airspeed indicator, would be about 183kts TAS and about 210mph TAS at that moment in time

the 'Book' which serves only as a planning guides, sez that at 10,000 feet, racks only (I suspect you are totally clean) in the 8000-9000 pound GW state at take Off ( the higher weight with full aft tank and full mains, full ammo)

2400RPM, 270IAS(mph), 36", 73gpm, 315mph with good airframe and good engine.
Reference P-51D-5 Operating Manual, 4/44 - page 54 for Column III range of 950 miles (intermediate condition )

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?

Is that not close for those cruise settings?

Jim - How far off between your 51 and the 'Book'?

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.

I've found that the "Books" are good for the slower end of the envelope, stall/spin recovery, traffic pattern speeds, short field techniques, and aerobatic speeds. All those numbers are relevant. We run the combat cruise settings and get what we get. They were optimized numbers to prevent plug fouling and greatest endurance. If you fly around at 30" and below you are going foul plugs pretty quickly.

The radials aren't as sensitive to that but we still run book numbers on the 24. The B-17 we run 40" for takeoff and 25" 1700 for cruise...simple because it is so light and has a great wing.

The closest I've come to have performance match the book is the AT-6 and the B-25...they both are nearly spot on.

Jim