51fixer wrote:
visaliaaviation wrote:
Regarding the mention of both B/C's and D in the same T.O. for EXACTLY the same reasons, IMHO, seriously jeapardizes the long held myth that the D needed the the DFF "because of the loss of side area in rear fuselage". To me, it's a rather obvious question that if the D needed to compensate for the loss side area, one is forced to ask why was it also ordered for the B/C, at the same time?
I had several discussions with expert aerospace guru Bruce Boland when younger and involved with air racing. He designed an enlarged vertical for the Red Baron P-51 because it needed still more surface area in the rear. Going back to NACA in the mid 40s, they operated a few P-51Ds that were used for various research projects. One project was using the P-51 for a wind tunnel. They found that increasing the thickness of the wing by around an inch over the gun bay area they could get the airflow in that area to go high transonic/ low supersonic. That was faster than the wind tunnels were. They would bolt a model or experiment on to the top of the wing. They would have to dive with power from high altitudes at high speeds. The Mustang would get a bit unstable doing this. They added an extension on top of the vertical to raise its height which inceased the surface area of the tail. This worked for them and they incorporated this same data into the new P-51H. They increased the height of its vertical after a number had already been produced. BTW they had to do the same later for the F-100.
For Frenesi we have considered building the tail area as a -5 without the fillet. After discussions with several sources (can we say brain trust) we have decided to retain the fillet. To those who operate P-51s having a fillet on a D is a fact.
Rich
The Flight Restrictiom TO 01-60J-6C that was issued 6 June 44 was a revision to a previous TO 01-60J-6B dated 27 Jan 44. The original was dated 31 Aug 43.
The -6C revision was to add the D to this TO which previously had only the B/C model listed.
With my slow typing I will copy the instructions:
1. Due to horizontal stabilizer failers which are believed to have resulted from slow rolls, all P-51B, C, D airplane will not perform slow rolls pending the installation of dorsal fin and rudder reverse trim tab and compliance with TO No. 01-60J-18.
The title of the -18 TO is
North American-Reinforcement of Horizontal Stabilizer and Fin- P-51 B,C,D and K This is dated 15 Jan 45 and revises a TO issued 8 April 44. The revision is to increase rivets in the elevator attaches from 3/16 to 1/4".
This reinforced the center of the fwd spar and the outboard elevator attaches along with the upper rudder attach.
The title of the -8 TO is
North American- Installation of Dorsal Fin and Reverse Rudder Boost Tab- P-51D
You mentioned that your opinion was the dorsal fillet was a reinforcement of the fus to vertical area. You mentioned that Reinforcement was a part of the TO and that was why you were calling the DFF a reinforcement. Is it possible that you are mistaking the reinforcement of the upper attach of the rudder as specified in the -18 TO?
This is the TO that uses the reinforcment in its title but it only applies to the horizontal spar and outer elevator attaches along with the vertcal upper rudder attach point.
The middle elevator and the middle rudder attach fittings were the same parts and design as well as the outer elevator and the upper rudder attach points. If they felt one was weak they applied the same fix to the other as well.
Rich
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