? For Snake45 & others........

[Bob Wright]

Someone sent me this illustration of a P-51 of my brother's squadron some time ago. The caption identifies it as a P-51D-5NA. Seems to me it is a P-51D-25NA:



As I recall the earliest Ds lacked the longer fin extension?

Bob Wright


Later: Further research shows some 8th AF P-51D 5NAs were retrofitted with the dorsal fin extension. Could be correct.

 

[737tdi]

Bob Wright: A little off your topic but sort of interesting. The extension of the dorsal fin and why it was done. I won't begin to explain the aerodynamics of it but you can find out much about it searching. It is amazing to me the difference in controllability over drag is as important as it is. If you look at side views of the 737-200,300,400,500,700,800,900 you will see each one is different. Especially between the -300 and -700. I will just say this, the dorsal fin actually becomes part of the vertical stabilizer and rudder system so can improve handling and even speed. By the way so can those wing to body fairings which changed with different models of the P51 as well.

Karl

 

[Wyandot Jim]

A, C model built in Dallas with a dorsal fin and a Malcom Hood. Also looks like a camera installed.

Despite these modifications, the P-51Bs and P-51Cs, and the newer P-51Ds and P-51Ks, experienced low-speed handling problems that could result in an involuntary "snap-roll" under certain conditions of air speed, angle of attack, gross weight, and center of gravity. Several crash reports tell of P-51Bs and P-51Cs crashing because horizontal stabilizers were torn off during maneuvering. As a result of these problems, a modification kit consisting of a dorsal fin was manufactured. One report stated:


"Unless a dorsal fin is installed on the P-51B, P-51C and P-51D airplanes, a snap roll may result when attempting a slow roll. The horizontal stabilizer will not withstand the effects of a snap roll. To prevent recurrence, the stabilizer should be reinforced in accordance with T.O. 01-60J-18 dated 8 April 1944 and a dorsal fin should be installed. Dorsal fin kits are being made available to overseas activities"

The dorsal fin kits became available in August 1944, and available as retrofits for P-51Bs and P-51Cs (but rarely used on the "razorback" -B and -C Mustangs), and to early P-51Ds and P-51Ks that had not already been built with them. Also incorporated was a change to the rudder trim tabs, which would help prevent the pilot over-controlling the aircraft and creating heavy loads on the tail unit.[31]

 

[Snake45]

Cool!

I don't recall offhand which block number introduced the dorsal fillet on the D Mustang, but I know it was a larger number than 5.

I don't think I've ever seen a fillet-less D model in the 55 FG. Most of the ones I've seen were with the 4, 352, or 357 groups. I think 55 group was still flying 38s until after the fillet was introduced, but I'd have to doublecheck that.