Corky Scott wrote:

Much great stuff snipped

When the model D Mustang was initially introduced, pilots complained
about it being more unstable than the B. That was because the
fuselage had been cut down and a bubble canopy installed instead of
the earlier turtledeck. This changed fuselage actually diminished top
speed somewhat and caused some instability. The engineers then added
the dorsal fin to the front of the rudder which is now considered one
of the signal visual characteristics of the model D.

Corky Scott


Hi Corky,

Excellent post. I used to believe the above:

that the dorsal fin was added to the D model only, and it was because the
fuselage was cut down. that's what all the books said.

However recent reading of some T.O.'s issued at the time show this may
actually not be the case:

Several crash reports tell of P-51B's and C's crashing because the
horizontal stab was torn off during maneuvering. The report says:

"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"

A previous entry for another crash:

Sections II and III of T.O. 01-60J-18 had not been accomplished. The
stabilizer was approximately 20 percent below the strength of a completely
reinforced stabilizer. It is believed that this type of failure will be
completely eliminated after compliance with T.O 01-60J-18 and the
installation of a Dorsal Fin and reverse rudder bost tab."

A Supplement to Basic Technical Order (From old Hap himself) says:

"1. Due to horizontal stabilizer failures which are believed to have
resulted form slow rolls, all P-51B, P-51C an dP-51D airplanes wil not
perfomr slow rolls pending the installation of dorsal fin and rudder
reverse trim tab, and compliance with T.O. No. 01-60J-18."

Part of this T.O. 01-60J-18, it seems, was to "...use 1/4" rivets rather
than 3/16" to attach the elevator outboard and rudder upper hinge fittings,
....to stabilizer ribs, providing additonal shear strength....."

The date of 01-60J-18 is 15 January 1945. By that time maybe most production
51's were D's (Don't know that for sure), so it would SEEM as if the Dorsal
was added for the D's only.

Also, I guess that drillingout the rivet holes to take the larger rivets
didn't weaken the riveted pieces any - they must have had enough meat left
over.


Also you can see photos of P-51B's or C's with the dorsal fin:

http://www.mustangsmustangs.net/p-51...tary/eto/6.jpg

http://images.google.com/imgres?imgu...% 3D%26sa%3DN
Scroll down til you see photos of T9 CK

--
Saville

Replicas of 15th-19th century nautical navigational instruments:

http://home.comcast.net/~saville/backstaffhome.html

Restoration of my 82 year old Herreshoff S-Boat sailboat:

http://home.comcast.net/~saville/SBOATrestore.htm

Steambending FAQ with photos:

http://home.comcast.net/~saville/Steambend.htm