Question for Drgondog

[GregP]

Hi Bill,

I have a question that you may well be able to answer and I have no agenda here except the question.

We have a customer who has a genuine TF-51D Mustang. It was converted by Temco. It has the tall tail like the P-51H model and also has the real TF-51 canopy with a larger enclosure. So, my question is:

Was the tall P-51H-style tail necessary? The extra vertical area from the canopy seems to be behind the center of lift so the extra tail area does not seem to be indicated to me, but I wonder if you have the aerodynamic data to justify the tall tail.

I do not ask for any work on your part, I just wonder if the tall tail seems indicated to you since other TF-51D's, like Miss Velma do NOT have the tall tail and do not seem to suffer any loss of directional stability according to the pilots who have flown both. One such is Steve Hinton Jr. who say they fly the same.

It's been a long time since I tried to figure out changes in tail area based on incomplete data and I thought you might already have data on the TF-51 on file. If not, thanks for a reply anyway.

 

[OldSkeptic]

In the absence of DR, it seems like a late model, post the introduction of the 51H.

The 51D (and the B/C) did have stability issues fully fueled/loaded up, not just CoG related but also in lateral stability. The later added strake helped (and strengthened the tail too, which was a weakness in the early Merlin Mustangs). The 51H design cured all that (and restored the G limits and improved the mach limit). So I can see it making sense to add the H tailplane to the later Ds.

You see similar thing with the Spits too with the later tailplanes.

 

[drgondog]

Hi Bill,

I have a question that you may well be able to answer and I have no agenda here except the question.

We have a customer who has a genuine TF-51D Mustang. It was converted by Temco. It has the tall tail like the P-51H model and also has the real TF-51 canopy with a larger enclosure. So, my question is:

Was the tall P-51H-style tail necessary? The extra vertical area from the canopy seems to be behind the center of lift so the extra tail area does not seem to be indicated to me, but I wonder if you have the aerodynamic data to justify the tall tail.

The one dad bought in 1959 was modified by Cavalier in return for a trade on a new 1650-7. It had standard flight controls, basic instruments, seat and 'long canopy - but the tail was stock.

NAA experimented with the "P-51H" style tail in early 1944 with limited positive results over the standard tail for the P-51D. Gruenhagen addresses the dive and tail tests.

The tall tail with the H wasn't as important as limiting aft fuselage fuel to 50 gallons or extending the fuselage 13". I never flew an F or an unmodified P-51D so I have no basis of comparison other than dad saying my ass in the back seat was nothing compared to full 85 gallons behind him and he could see no difference between unmodified D and the Cavalier two seater.

I don't recall if the tall tail D at Davis Monthan Heritage in 2010 and 2011 was a Tempco mod but it sounds like it.

I do not ask for any work on your part, I just wonder if the tall tail seems indicated to you since other TF-51D's, like Miss Velma do NOT have the tall tail and do not seem to suffer any loss of directional stability according to the pilots who have flown both. One such is Steve Hinton Jr. who say they fly the same.

I would believe Hinton is correct for the reasons I stated aboveI

It's been a long time since I tried to figure out changes in tail area based on incomplete data and I thought you might already have data on the TF-51 on file. If not, thanks for a reply anyway.

I have never seen test data on the TF-51D. I do know there were several field mods at Steeple Morden into two seaters but the canopy was a kluge three piece monstrosity.

NAA couldn't 'analyze' differences either so they popped a couple of different styles and tested in wind tunnel. You could probably analyze today with apps like VSAERO and a complete and accurate airframe model in level flight.

NAA was looking for more vert stab authority and less rudder in dives to improve yaw w/o over torqueing the fuselage

 

[GregP]

Thanks, Bill. I'll get a few pics Monday and post them.