P-51H flight test performance

[prentice672]

Hi, I'm new to this forum business so I hope this message gets through. I stumbled on to this site the other day looking for FW-190D-9 data and I found an interesting discussion on "If you were rich and could afford ..." in which one of you presented some very interesting data on the P-51H. I was surprised to see a flight test report(October of '46, serial number 44-64182) that gave the top speed as only 451 mph with 90 inches Hg, which is in stark contrast to the 487 mph figure one usually sees in the literature. I find this very hard to believe since another flight test report on the P-51B gives its top speed of very nearly the same value. In fact, there is another flight test report on the P-51H (dated May of '45 related to serial number 44-64161) which gives a top speed of 450 mph with just 67 in. Hg. Has anyone reconciled these figures by any chance?

Ron

 

[davparlr]

In that thread, I was also confused by the difference in what was published and what was tested. The published speed, 487 mph, was an engineering analysis with some input from flight test. The calculations was based on a clean wing with no bomb/fuel tank racks. The flight test data you identify was with those racks. As stated in the referenced thread, I made the following analysis:

"As an engineer, what has been bothering me is why the P-51H engineering charts deviated so greatly from test data (482 mph (776 kmh) to 453 mph (729 kmh). These guys were pros and would be unlikely to make such a large error. I think the deviation (identified on another site) is that the engineering charts reflect a clean aircraft (no racks) and the flight test were done with fuel and bomb racks attached. Flight test data on P-51Bs shows that max speed with racks was 431 mph and without racks, 444 mph. Therefore you can expect a greater impact at higher speed (I believe drag increases by the square of the speed), so it is reasonable to believe that the impact to the P-51H would be in the 15 mph range. This would raise the P-51H's top speed to 468 mph in test. This would bring the error to 3%, add in the typical engineering/marketing optimisim, and the engineering value makes sense."

I have never found flight test data on a clean P-51 or that shows the 487 mph, so I believe that the P-51H, clean is capable of around 470 mph. I understand that North American recaluculated 471 mph, but I have not seen that data. Most of the data supporting the above data points can be found on your referenced thread. The P-51H is still a very fast aircraft.

 

[Twitch]

By contrast I've never seen the top end listed as anything other than 487 MPH in every book I own or have perused. I dunno.

 

[davparlr]

By contrast I've never seen the top end listed as anything other than 487 MPH in every book I own or have perused. I dunno.

Neither have I. But the only place I have seen 487 mph in an analysis or flight test has been in a North American engineering chart and that was with a clean wing. The flight test I have see on spitfireperformance shows a couple of test with a speed of around 450 with wing racks, thus my analysis.

 

[Soundbreaker Welch?]

Nice siggy Twitch.

 

[Soren]

I'm gonna have to agree with davparlr on this one.

 

[Jank]

So is sounds like the P-51H wasn't the high speed king it has been made out to be.

Both the P-47 M at 472mph and P-47 N at 467mph were faster and were operational in their respective theatres before the end of the war.

 

[davparlr]

So is sounds like the P-51H wasn't the high speed king it has been made out to be.

Both the P-47 M at 472mph and P-47 N at 467mph were faster and were operational in their respective theatres before the end of the war.

I looked at some data on the P-47M and N at a sources that seems to have pretty good data. The charts that reflected the speeds noted above appear to be Corporate documents similar to the one that shows the P-51H doing 487 mph. They did not look like flight test data. I always look for a tail number for flight test aircraft. These did not have it. It did have flight test of a P-51N with a tail number, but unfortunately, it did not show war emergency power.

Without further info, which could be out there, I would consider this info engineering analysis, and, according to Soren, could be 4% off (FW requirements). You can bet it won't be on the low side.

 

[Mike Williams]

I think the confusion stems from exactly what condition constitutes a "clean" aircraft.

Flight Test of the P-51H Airplane AAF No. 44-64182 states "All tests at the fighter configuration (bomb and rocket racks only) were flown at a take-off weight of 9544 lbs…." Check Here. Note that the specified weight of 9544 lbs, which includes bomb and rocket racks, is also recorded on the climb and level speed graphs.

A clean aircraft in this instance is equipped with one bomb rack and three rocket racks per wing with no ordnance. Please refer also to this photo of 64182.

For a similar occasion where a clean aircraft in fact includes the racks please see
Flight Tests on the North American, P-51D Airplane, AAF No. 44-15342 This report states: "The clean configuration included one external bomb rack on each wing." Check Here. Of interest is the max speed of 442 mph, which includes bomb racks.

The P-51 Tactical Planning Characteristics Performance Chart notes that the early racks cost 12 mph at high speed, while the new type bomb racks decrease high speed 4 mph.

It can be seen therefore that the maximum speeds recorded for 64182 were largely influenced by the drag of rocket racks.

 

[Jank]

All I could find concerning actual speeds achieved was the following:

Figures are for aircraft in combat loaded condition. The high speed of the "D" - 435mph @ 32,000ft is estimated. The top speed of the "M" - 473mph @ 32,000ft and the "N" - 457mph @ 32,000ft are actual.

 

[davparlr]

All I could find concerning actual speeds achieved was the following:

Figures are for aircraft in combat loaded condition. The high speed of the "D" - 435mph @ 32,000ft is estimated. The top speed of the "M" - 473mph @ 32,000ft and the "N" - 457mph @ 32,000ft are actual.

This seems to be the source of my reference for the M. Most AF documents tend to be good since there is no reason to stretch the numbers. This is no flight test document and no tail numbers are listed but this does state that the numbers are actual (except the D). Several of the super hi-performing aircraft tend to run around the 470 mph top, P-51H (my estimate), Ta-152H, and P-47M. This probably indicates that drag increases with those aircraft are reaching their limits for the engines available. Also, I suspect propeller efficiency is starting to fall off. It seems more and more data is emerging every day. Great news for those of us who love to study these planes.

 

[davparlr]

Just for a note of interest, the world's record for a piston engine aircraft, unlimited over a 3 km course is an F8F, with a R3350 engine (non-standard) generating 3800 hp, of 528 mph in 1989. Over a 15/25 km course is a P-51D, with a merlin generating 3000 hp, of 518 mph in 1983. I'm sure both of these aircraft and engines were highly modified. I think you can tell that piston engine aircraft were definately reaching their limit.

 

[Jank]

davparlr said, "Most AF documents tend to be good since there is no reason to stretch the numbers."

I came across some AAF data on the late model P-47D with paddle blades and water injection. Impressive rate of climb (3,200fpm) but nothing outstanding as far as top speed.

 

[prentice672]

There are two flight test reports on the P-51H I have referred to; one is TSCEP5E-1898 dated May 1, 1945, and the other is TSFTE-2029 dated October 14, 1946. The first of these tested an airplane with wing racks installed but no rocket racks, the later report tested an airplane with both installed. In the former report they could only pull 67" Hg due to a malfunction in the water injection system and they state that they would obtain data for the 90" power setting and attach it as an addendum to that report. Does anyone know if that addendum is available somewhere? Thanks.

Ron

 

[Soundbreaker Welch?]

I was wondering if the P-51D also suffered from speed loss when wearing it's droptank racks, and perhaps manuverability. Are there any stats that indicate this?

 

[Soren]

It would've lost speed no doubt, but I don't believe it suffered in other departments.