P-51D propeller technical data request

[hvengel]

have been working on a P-51D model for use with FlightGear. FlightGear and my model are "open source" and are available to the public at no charge. See:

wiki.flightgear.org

for more information on FightGear

and to download the P-51D model use the following link.

RapidShare: 1-CLICK Web hosting - Easy Filehosting

I have found a wealth of information about the aircraft in terms of flight test and wind tunnel data detailing things like lift, drag and moments. But one area where I have not found much info is for the propeller. What I need is actual engineering data for the prop that has the following information.

1. The thrust coefficients for the range of advance ratios and pitch angles needed for a P-51D.

2. The power coefficients for the range of advance ratios and pitch angles needed for a P-51D.

3. The minimum pitch angel of the prop.

4. The maximum pitch angel of the prop.

5. Propeller rotational inertia.

6. Propeller disk diameter.

7. Minimum RPM.



8. Maximum RPM.

The aircraft being modeled has a round tip cuffed prop. But I would be happy to get the above data for any prop actually used on a P-51D. My primary goal for the model is to make is as realistic as possible and feedback from those "flying" it is greatly appreciated.

[FLYBOYJ]

Here's a few

11 ft 2 in (3.40 m) diameter

3000 rpm

there's no minimum RPM - normally idle was set between 800 and 1000 rpm

I think you're looking at a 24D50 prop, this might help

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/48496dcb1d17867d8525670f0068c846/$FILE/p-784.pdf

[hvengel]

Here's a few

11 ft 2 in (3.40 m) diameter

3000 rpm

there's no minimum RPM - normally idle was set between 800 and 1000 rpm

I think you're looking at a 24D50 prop, this might help

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/48496dcb1d17867d8525670f0068c846/$FILE/p-784.pdf

The hub is the 24D50 but it was fitted with different blades. The main thing I need is the two tables that have the thrust and power coefficient data. These tables will look something like this:

Thrust coefficient table 

advance                blade angle
ratio         15         25         35         45         55          65
0.0           0.2068  0.2534  0.2792  0.2974  0.2779  0.2326
0.2           0.1696  0.2358  0.2615  0.2825  0.2640  0.2210
0.4           0.1243  0.2273  0.2498  0.2726  0.2571  0.2152
0.6           0.0622  0.1934  0.2262  0.2512  0.2398  0.2036
0.8           0.0032  0.1344  0.2038  0.2248  0.2226  0.1890
1.0           -0.0532 0.0798  0.1903  0.2076  0.2148  0.1841
1.2           -0.1094 0.0246  0.1564  0.2005  0.2148  0.1841
1.4           -0.1598 -0.0430 0.1351  0.2370  0.2530  0.2210
1.6           -0.1682 -0.1150 0.0775  0.2405  0.2612  0.2326
1.8           -0.1682 -0.1682 0.0130  0.2068  0.2534  0.2326
2.0           -0.1787 -0.1787 -0.0549 0.1716  0.2681  0.2472
2.2           -0.2522 -0.2522 -0.1746 0.1746  0.3722  0.3490
2.4           -0.2733 -0.2733 -0.2733 0.1008  0.3293  0.3780
2.6           -0.3153 -0.3153 -0.3153 0.0147  0.2405  0.3878
2.8           -0.3889 -0.3889 -0.3889 -0.1077 0.1943  0.3889
3.0           -0.4099 -0.4099 -0.4099 -0.2459 0.1074  0.3151
3.2           -0.4309 -0.4309 -0.4309 -0.3975 0.0100  0.2321
3.4           -0.4519 -0.4519 -0.4519 -0.4519 -0.0972 0.1389
3.6           -0.4730 -0.4730 -0.4519 -0.4519 -0.2051 0.0350

The power coefficient table will be very similar. These tables are standard engineering data used for propellers. I am currently using tables that were generated by a utility program but these tables are clearly less than optimal since these appear to be optimized for a different speed range than would be ideal for the P-51D. As a result the low speed performance is too good and it has poor high speed performance. I have hand tweaked these generated tables to try to fix this but this is at best a kludge. I need the real data for the actual prop. to be sure I have it right.

[FLYBOYJ]

I believe the most common P-51D blade was the 6813. I cannot find other model numbers that fit the 24D50 hub. There might be some old data compiled at Wright Pattersone that might have what you're looking for. Have you tried these guys? Sometimes some interesting documents float through there.

P-51 Mustang Who? Case # 226 Find out who that P-51 is! ... MustangsMustangs.com

[unix_nerd]

Hallo!

I suggest the use of javaprop to get the data !

JavaProp

I did a little calculation with the following settings
Diameter 3,40m (correct value)
Sipnnerdiameter 0,45m (estimated)
Power 1214000W
RPM 3000
Airfoil ClarkY Re500000 for the two outer section
Airfoil ClarkY Re100000 for inner sections
Speed 60m/s

this will give you:

Durchmesser D 3,40 m
Spinner Durchm. Dsp 0,45 m
Drehzahl n 3000 1/min
Geschwindigkeit v 60,000 m/s
Blattzahl B 4
Propeller
v/(nD) 0,4 v/(ΩR) 0,127
Efficiency η 69,21 % loading medium
Thrust T 14,003,5 N Ct 0,0566
Power P 1,214,01 kW Cp 0,0327
β at 75%R 14,9° Pitch H 1,87 m

This might be not the very historical value but might be within 10% of the data from the correct modeled thing.

please find attached my java prop input file

The historical prop went from low pich 23grd to high pitch 65grd. For the analysis and modeling for the sim this can be ignored as it was designed to give the optimum thrust at given power setting.

best regard

[hvengel]

Hallo!

I suggest the use of javaprop to get the data !

JavaProp

I did a little calculation with the following settings
Diameter 3,40m (correct value)
Sipnnerdiameter 0,45m (estimated)
Power 1214000W
RPM 3000
Airfoil ClarkY Re500000 for the two outer section
Airfoil ClarkY Re100000 for inner sections
Speed 60m/s

this will give you:

Durchmesser D 3,40 m
Spinner Durchm. Dsp 0,45 m
Drehzahl n 3000 1/min
Geschwindigkeit v 60,000 m/s
Blattzahl B 4
Propeller
v/(nD) 0,4 v/(ΩR) 0,127
Efficiency η 69,21 % loading medium
Thrust T 14,003,5 N Ct 0,0566
Power P 1,214,01 kW Cp 0,0327
β at 75%R 14,9° Pitch H 1,87 m

This might be not the very historical value but might be within 10% of the data from the correct modeled thing.

please find attached my java prop input file

The historical prop went from low pich 23grd to high pitch 65grd. For the analysis and modeling for the sim this can be ignored as it was designed to give the optimum thrust at given power setting.

best regard

I had a look at this and it appears that your input file is in error. The merlin was geared and the prop RPM at an engine RPM of 3000 was 1260 RPM. But even with that I don't know how to use JavaProp to generate what I need. Perhaps you can give some clues of how to go about using it to generate the tables I need (see the example above).

I have been in contact with the curators at the National Air and Space Museum about this and they were unable to find the information. But I did learn that there were at least three different Ham Standard blades used during or right after WWII on Merlin powered Mustangs. These include the 6523A-24 (probably the most common one), 6547A-12 (the so called paddle blade) and the 6526A-24 (this is what the NASM P-51D has). It appears that the modern replacement blade is a 6813 that has been cut down to the correct length. This is supposed to be exactly like the 6523 blades.

[dairwin]

Prop reduction ratio 0.477 on early Packard V1650, or 0.479 on later marks.

[hvengel]

Prop reduction ratio 0.477 on early Packard V1650, or 0.479 on later marks.

Some sources also list 0.42. This makes sense since the V-1650 series was derived from the Merlin 61 which is listed as having a 0.42 ratio. I believe that 0.42 is correct for the V-1650-7 since a lower ratio would result in lower prop tip speeds and for faster the aircraft this will allow for more of the speed envelope to be below a prop tip speed of 1000 FPM which is the point where efficiency starts to drop off.

[hvengel]

The prop file for JavaProp that unix_nerd posted gave me a good starting point and I was able to figure out how to use JavaProp to generate a full set of table data.

I now have generated a set of prop tables. Initial testing with the new prop data went well and things felt right with things like climb rates and speeds being fairly close to published figures right out of the box although these were a little on the low side (perhaps 5% below published figures). I will likely have to do a bunch of testing and tweaking to get things tuned to be closer to published performance data. I should also add that the resulting prop feels better than any that I have tried so far. For example take off performance is excellent were as all of the other props I have tried have had major issues with this part of the envelope and have needed extensive hand tweaking to make takes feel even close to right.

I am still trying to find the actual historic data but the prop generated using the above tools seems to be fairly good and if I don;t find the actual historical data I think I can live with it.

As a side note my updates to this model have now been accepted by the FlightGear project and are in it's source code repository. It will be included in the next release.

[dairwin]

Sorry, I haven't followed this thread for a while.

The reduction gearing for Packard V1650-3 and -7 engines provides a ratio of 0.479 to 1 and consists of a 21-tooth spur-type drive pinion and a 44-tooth propeller shaft gear.

The Merlin 68 and 69 reduction gear assemblies provide a ratio of 0.420 to 1 and are fitted with a 21-tooth pinion and a 50-tooth propeller shaft gear.

Merlin 61 and 72 are 0.42 to 1, and Merlin 63, 63A and 64 were 0.477 to 1.

Hope this helps.

DAI