In the early stages of WW II, the need for a fast, maneuverable low level photographic airplane had been stressed by Army Air Force Ground-Air Support Command, resulting in the study of the feasibility of a photographic installation in the P-51. This study was conducted at the North American Aviation Corporation, Inglewood, California, and a representative of the Photographic Laboratory, Materiel Center, Wright Field, was present during the study, design and fabrication of the installation. The study appears to have been conducted in late 1942 to early 1943, as the memorandum describing it and summarized herein dates from January 19, 1943.
After considerable study, it was determined that two cameras would satisfy the requirements set by the Ground-Air Support Command. One camera was to be a combination vertical and rear oblique and adjustable while in flight. The other camera was to be a side oblique which, when used in conjunction with the rear oblique camera, would result in the overlapping of the two pictures. The combination vertical and oblique camera was mounted just aft of the radiator exhaust scoop. See photograph nos. G-1796, G-1789, G-1794, and G-1788 above.
In the installation, very little rework was necessary in the airplane, except for the addition of a heavy shear web and plate glass window in the bottom panel, as shown in photo G-1797.
The rear combination camera mount was hung on an oilite bearing in a bracket fastened to the skin of the longeron and was connected with the tilting control, as shown in photos G-1791 and G-1796. The control for the tilt was located on the left side of the cockpit above the flap control.
The rear camera had two positions—vertical and rear oblique. When the camera was in the oblique position, the control handle was in its rearward position and the optical axis of the camera was at an angle of 30° below the horizontal center line of the airplane. When changing from oblique to vertical position, the pilot grasped the slide handle and pushed forward. To lock in the vertical position, the pilot merely gave the handle a 90° turn either up or down, as shown in photo G-1790. This control was later replaced with a small crank, which required a 340° turn to change the camera position.
The rear camera was easily accessible for reloading or servicing by removing the window (photo G-1797) located underneath the ship just aft of the radiator scoop outlet. The mount was a CG mount with US Rubber shock mounts for vibration absorption.
The front oblique camera was mounted on a triangular mount fastened to the overturn structure with four thumb screws, as shown in photos G-1798 and G-1795. This camera photographed through a plate glass window which was inserted in the plexiglas radio window, as shown in photos G-1797 and G-1793. The plate glass insertion was necessary to give satisfactory pictures. The optical center line of the camera was 41° out from the center line of the ship and was depressed 30° when the camera was in position. No overlap was possible when the cameras were in their positions, but to obtain overlap it was necessary to use a position in which the front oblique camera had a large amount of cut-out in the photograph due to structural interference. The front oblique camera was readily accessible through the right hand radio window for reloading or servicing. The camera mount was a CG mount with integral US Rubber vibration absorbers.
The controls for both cameras were located on the left hand side of the cockpit underneath the upper longeron, as shown in photo G-1790. The control box had three switches and three yellow blinker lights. It was used in conjunction with the intervalometer which was located just forward of the control stick underneath the instrument panel. The inboard gun firing button on the control stick was used in conjunction with the control box in order to operate the camera under run-away (continuous shooting) conditions. The cameras could be operated either run-away or with the intervalometer and independently of each other, if desired.
For operation of the cameras, the camera switch had to be in “ON” position. If desiring to use the camera run-away, the forward switch on the panel had to be in the “MANUAL” position. To operate the camera, the pilot pressed the button on top of the control stick. The cameras would then operate run-away, taking approximately three pictures a second. This run-away operation would exhaust the film in approximately 40 seconds if the magazine contained 125 exposures.
For operation of the camera with intervalometer, the intervalometer was first set at the desired interval and, with the camera switches in the “ON” position, the forward switch on the panel was put in the automatic position. The cameras would then take pictures at the interval of setting, photo G-1792.
The blinker lights over the front and rear camera switches blinked every time the camera took a picture. The light over the forward switch would go on when the intervalometer was in use and would stay on until an impulse was given to the camera and then would go off for approximately 1 second. The intervalometer had a counter on the lower left hand corner of the lid.
Upon completion of the installation, flight tests were conducted. As only one K-24 camera was available, two flights were necessary in order to test the camera in both of its positions.
Pictures were taken at various altitudes from 1,000 to 20,000 ft, with the rear camera in its vertical position. For test of the oblique camera position, the plane was put into a long shallow dive from 20,000 ft and at about 100 to 150 ft a straight run was made with the camera operating run-away. A speed of approximately 400 mph was obtained. For test of the front oblique camera, one run was made at approximately 200 to 300 ft altitude.
From photographs taken in all tests and the reports from pilots who had flown the airplane, this installation was very satisfactory for the purpose intended.
Identity of this Mustang
Sharp-eyed reader Mark Williams noticed that all the photos above are labeled with “91-xx-x,” with the “91” indicating North American model number 91 (NA-91), which was the Allison-powered, 20mm cannon-equipped P-51, also known as the Mustang Mk. 1A. The serial number of the aircraft in the photos is clearly visible in photo G-1792 on the “Radio Call” plate on the lower instrument panel; this is aircraft 41-37327, one of 55 originally sold to the British, but retained by the USAAF. This definitely matches the NAA model number NA-91, and is designated as an F-6A; note the early-style, round antenna as well. This aircraft was later involved in a landing accident on 12/14/1944 at Lakeland Army Airfield, Florida. It’s not known if this aircraft was deployed to North Africa (or Sicily) in 1943 with the recon squadrons, but it is known that most F-6A’s were withdrawn from the ETO (replaced with F-6C’s, etc.) and used as trainers for the remainder of the war.
It should be noted that the Royal Air Force had already modified many of their Mustang Mk. 1’s for tactical reconnaissance due to the poor high-altitude performance of the aircraft’s Allison V-1710 engine. These aircraft were involved in many famous missions, such as photographing the French port of Dieppe before the ill-fated commando raid in August 1942. The success of these early British reconnaissance Mustangs may have played a part in the USAAF’s decision to develop their own P-51’s modified for the photo reconnaissance role.
All images from NARA Archives II, College Park, MD, RG 342
Memorandum, F.O. Carroll, Brig. General, Chief, Eng. Division, to Chief of Staff, AAF Mat. Com., Dir. of Photog., subject: Photographic Installation in P-51 Mustang, January 19, 1943, in the files of National Archives II, College Park, MD, RG 342