View Full Version : Ian Boys: Please read: Data re. the P-47D27

08-18-2003, 07:44 AM
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Message Edited on 08/18/0306:49AM by RAF74BuzzsawXO

08-18-2003, 07:44 AM
No Text

Message Edited on 08/18/0306:49AM by RAF74BuzzsawXO

08-18-2003, 07:50 AM
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Message Edited on 08/18/0306:51AM by RAF74BuzzsawXO

08-18-2003, 07:52 AM
Salute Ian

Previously I posted details relating to the P-47D-10, which does not have the wing pylons.

This post is in relation to the P-47D-27 and peripherally, the P-47D-22, which although it has pylons, has a razorback configuration and different weight.

Please bear with me, and try to follow my reasoning in this instance.

First of all, there do not seem to be as readily accessible primary sources which deal directly with the rollrate of the D-27 as there are for the D10.

There are a number of excellent secondary sources, in particular the book: "America's Hundred Thousand", which has extensive references to its material to the primary source material from which its author gathered his data. It is clear the author did his homework. However he does not present copies of the original NACA charts or manufacturers charts, instead creating its own amalgamated charts.

For this reason, I will only be using these charts as corroboration of primary source material rather than accepting them on their own merits. I am presenting the figures here, but will not be posting the charts.

The charts available in this book specify either a rollrate for the C1-RE, using the same figures which I previously supplied to you in the NACA material posted earlier. It also specifies at rollrate for a "P-47", without indicating which model. And finally it specifies a rollrate for the D-30, but only at a 30 lb Stickforce. (this data obviously comes from a NACA report which I will be using as my primary reference in this presentation)

The "America's Hundred Thousand" graph chart for the P-47C-1RE indicates the exact same rollrate performance for this aircraft as seen in the NACA chart I have presented previously. As mentioned, the C-1RE is identical all practical respects to all models of the Razorback P-47D up to the D21.

The "America's Hundred Thousand" graph chart for the unidentified "P-47", indicates a maximum rollrate of 55 degrees per second at 160 mph, (I pick the figure of 160 mph for a reason you will understand later) peaks at approximately 72 degrees per second at 250-300 mph, and maintains a rollrate of over 62 degrees per second up to 400 mph .

The "America's Hundred Thousand" graph chart for the P-47D-30 at 30lbs stickforce, indicates a maximum rollrate of approximately 50 degrees per second per second at 160 mph, a peak rollrate of 62 degrees per second at around 210 mph, and maintains a rollrate over 40 degrees per second up to 300 mph.


The one available primary source for Bubble top P-47's with the dorsal fin addition is NACA Report # 2675, located here:


This report was commissioned to investigate the stability of the late model bubble top P-47D's with the dorsal fin. Earlier bubble top models had yawing instability with heavy rudder application due to the removal of the Razorback "ridge" portion of the original plane. Republic corrected this problem with the addition of a dorsal fin running between the bubble canopy and the tail.

For the reason that this report is not primarily concerned with lateral rolling performance, rollrate was only peripherally mentioned in the report. However, we can make some determinations based on the information contained.

The test was done with the F-47D-30, which was the renamed ID for the aircraft previously known as the P-47-D-30

The first chart which comes to our attention is this one, which details rollrate for the D-30 at stickforce of 30 lbs.


30 lbs was not the standardized test figure for stick force used in WWII by the USAAF. It was used in this instance only as an arbitrary figure. The measurement of rollrate was not the intent of this report, rather, measurement of yawing instability was the intent. Yaw is primarily induced by application of rudder. However in most maneuvers, rudder is applied simultaneously with aileron. Therefore, in this report, the requirement was to standardize the amount of aileron applied at a benchmark figure which could be used in the tests. In this case, it was decided to set the benchmark at 30 lbs for the particular test which the chart shows us. Other tests in the report used different stick forces, varying from 10 lbs to 50 lbs.

Since the figure used in the above chart is only 30 lbs, then the results can only be taken as a gauge of the rollrate up to the point at which 30 lbs was no longer sufficient to apply full aileron deflection. The results can be taken as accurate for that.

We know from studies, that full aileron deflection can be attained at lower speeds with a smaller application of force to the stick.

This chart shows a rollrate of approximately 50 degrees per second at 160 mph, a peak of 62 degrees per second between 200 - 230 mph, and maintains a rollrate of over 40 degrees per second up to 300 mph. The chart essentially goes flat at 200 mph, obviously this is the point at which 30 lbs stickforce is no longer capable of fully deflecting the ailerons against the pressure of the atmosphere.

As clearly detailed in my previous posting re. the P-47C-1RE and D-10, most USAAF rollrate tests used a stickforce benchmark of 50 lbs. I am now going to add a Chart which details a test at 50 lb stickforce with a P-47C-1RE for the purposes of comparison to the first chart:


If we look at this chart, we see a rollrate of 58 degrees per second at 160 mph, a peak of 84 degrees per second between 230 and 270 mph, and maintains a rollrate of over 65 degrees per second up to 400 mph.

Now the first thing the comparsion between these charts tells us is that at 160 mph, there is a difference between the P-47C-1RE and the P-47D-30 even though at that speed, full aileron deflection is likely be achieved by the D-30.

The difference between the two aircraft's rollrate at 160 mph is 14 %.

At 200 mph, the P-47C-1RE rolls at 73 degrees per second. The P-47D-30 with 30 lb stickforce rolls at 62 degrees per second.

The difference between the two aircraft's rollrate at 200 mph is 15%

The two aircraft's rollrate graph lines seem to be moving in syncrony.

Over 200mph, the rollrate of the P-47D-30 at 30 lbs goes flat. Meanwhile the rollrate of the C-1RE continues to climb. Obviously the extra 20 lbs force applied to the ailerons of the C-1RE is allowing full aileron deflection to continue at the higher speeds. In fact rollrate of the C-1RE continues to increase up to 230 mph at which point it also goes flat. Again, the conclusion can be drawn that at 230 mph, the C-1RE has reached the point at which 50 lbs is no longer sufficient to fully deflect the ailerons against the force of the atmosphere.

What are my conclusions from this comparison?

Well, we know the D-30 had pylons fitted. Whereas the C-1RE did not.

It is logical to assume that the presence of the pylons is what has reduced the D-30's rollrate by approximately 15% at lower speeds. That would explain the difference in rollrate at low speeds where the lower 30 lb stick force was not a handicap.

I am going to make the logical deduction from this, that we can also assume, that given a 50 lb stickforce for the D-30, its rollrate curve would follow the C-1RE's, minus 15%.

Therefore, based on this assumption, we would see from the D-30, a rollrate of the following:

50 degrees per second at 160 mph. (this figure we know is minimum achievable at this speed from the 30 lb test) 71.5 degrees per second at 230 mph through 260 mph, and maintaining a rollrate of at least 55 degrees per second up to 400 mph.

Now you may say, "How do I know the P-47D-30 could have 50 lbs stickforce applied?"

We know it could, since there are other charts in Test Report # 2675 which show the aircraft tested at stickforce of 50 lbs.

You can see from the two following charts this is the case:



In fact stickforce is shown at 50 lbs on the second chart.

Further to these charts:

Measurement of Helix Angle of Roll through equation pb/2V, which is what these chart results provide, is another way of measuring rolling characteristics, although not as accessible to us plebians without aeronautics degrees.

The following define the values of the equation: pb/2V

P= Angular Velocity in Roll, Radians per second
B = span of wing
V = True Airspeed

The size of a radian is determined by the requirement that there are 2Pie radians in a circle. Thus 2Pie radians equals 360 degrees. This means that 1Pie radian = 180/ degrees, and 1 degree = Pie/180 radians.

If someone wants to work back from the above charts which recorded the Helix Angle of Roll measurements of a series of tests, they would be able to determine the number of radians per second which the aircraft rolls, and by translating radians to degrees, would be able to provide a figure of degrees per second rollrate.

I could probably do the calculation with a bit more research, but I am at the moment, a little burnt out on the subject. If no one else has the time or is unable, I will do it in a few days.

In any case, my conclusions are that the P-47D-30 should have a maximum rollrate of approximately 71.5 degrees per second at 230 - 260 mph and should not drop below 50 degrees per second through the speed range of 160 mph to 400 mph.

The question of the P-47D-22's rollrate remains. But it is logical to assume it would fall somewhere between the other two aircraft.

Thankyou for your patience RAF74 Buzzsaw

08-18-2003, 07:52 AM
Sorry, screwed up post of first two attempts.

08-18-2003, 07:56 AM
Salute Ian

Please respond to indicate you have read the post.

Thanks again RAF74 Buzzsaw

08-18-2003, 08:55 AM
Salute Ian

Just realized I have the answer to the rollrate question right in front of my nose.

If you look at the first chart again:


You see that at 30 lbs Stickforce, the rollrate peaks at 62 degrees per second.

If you look at the lower section of the chart, you see that the pb/2V number peaks at .074.

Therefore a pb/2V number of .074 is equivalent to a rollrate of 62 degrees per second.

Then look at the second two charts:



You can see the pb/2V number peaks at .074 at 130 mph, 150 mph, 200 mph, and 250 mph. It drops to .070 at 300 mph, further to .030 at 350 mph and 400 mph.

If we use a percentile calculation, we get the following rollrates:

130 mph 62 degrees per second

150 mph 62 degrees per second

200 mph 62 degrees per second

250 mph 62 degrees per second

300 mph 60 degrees per second

350 mph 25 degrees per second

400 mph 25 degrees per second

The only issue with this is that we may be shortchanging the P-47D30's rollrate, because the stickforce applied to get the .074 pb/2V figures is less than 50 lbs at all speeds except 300 and 400 mph. And at the higher speeds application of maximum stick force would be crucial to attain maximum aileron deflection.

However, we do know now clearly that the P-47D-27's rollrate should be higher than what is being achieved now.

Thanks RAF74 Buzzsaw

08-18-2003, 09:06 AM

Speeds are TAS at 5000 ft.

08-18-2003, 12:00 PM
tas??? are u sure?

Ian Boys
Kapitan - 38. OIAE

08-18-2003, 02:09 PM
ian why do you guys think naca makes up information i remember skychimp posting charts of the roll rate and before fb came out and oleg said naca data is unrealiable. Just wondering why 1c thinks that?


Good dogfighters bring ammo home, Great ones don't. (c) Leadspitter

08-18-2003, 02:53 PM
IMHO its because its only ONE source of information, to get the full details, several sets of data needs to be gathered and correlated.

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