BACKGROUND
The Canberra's design team at Preston were tasked with producing a photographic version of the Canberra B.2 to be a replacement for the ageing Mosquito types that were in service during and immediately post war. The Canberra proved ideally suited to the role bringing a high altitude capability that was also an extremely stable platform as well as being very fast (for its day).

Shortening the bomb bay and extending the fuselage by some 14 inches allowed the design team to fit a fuselage (belly) fuel tank and forward camera bay without resorting to any changes in the basic design of the aircraft. Flight testing of this extended fuselage amplified a known Canberra trait, ie that of producing a lateral tail section slow frequency vibration. This was partially cured by slabbing the fuselage sides with thick aluminium sheets from the wing spar to just below the fin strake. This modification increased the stiffness of the rear section allowing the aircraft to be cleared for service release. The PR.3, which had a limited production, and PR.7 fuselages were identical, the difference in marks being the introduction of the later higher thrust Rolls Royce Avon 109s and integral wing fuel tanks to the PR.7.

CAMERA INSTALLATIONS
The PR Canberra was designed to have four operational roles. . .
1 Day Role
2 Alternative Day Role
3 Day Survey Role
4 High Level Night Role

The F52 cameras were externally driven by a fuselage mounted motor and flex drive, the F49 and F89 cameras had built in motor drive assemblies. The F52 cameras because of the external drives were very noisy in operation. Shutter release timing of the F52 and F49 cameras was controlled by the navigator from either his position behind the pilot or from the nose prone position by Type 35 camera controllers. The F89 camera had its own F89 controller. The F49 Survey camera could optionally be fitted in to a Type 50 mounting. This could compensate for aircraft heading inaccuracies due to winds and aircraft trim. This meant that alongside the Type 35 controller in the navigator's or prone position was fitted a Type 50 drift-and-tilt controller as well.

FORWARD CAMERA BAY
The forward camera bay was just foward of the flare bay and accessed from a double handled door under the fuselage. This bay could hold in the Day Role up to four F52 cameras.

No provision was made to assist in the mounting or positioning of these cameras due to a marked lack of space. In the Alternative Day role only two cameras were fitted.

CENTRE CAMERA BAY
Access to the centre camera bay was gained via the rear hatch, a hinged door under the fuselage just aft of the flare bay. This allowed the fitting of either two F52 cameras in the Day Role or two F89 cameras in the High level Night Role. Because of the room available inside the rear fuselage, a mini hoist system was available and could be used, if required, to help get the cameras in to position.

REAR CAMERA BAY
The rear camera bay was accessed using the same rear hatch entrance as the centre camera bay. It could be fitted with an F49 camera with or without its Type 50 drift-and-tilt compensating mounting. Various lens options could be fitted depending on the role intended, provision for this being made in various height adjustable pip pin mounting holes provided. For the Night Role two windows were provided for the two Photo Cell units used to trigger the operation of the F89 cameras. These were both usually fitted to the port window.

NAVIGATOR'S STATION
Depending on the aircraft's role Day Role operations could be controlled from the Type 35 controllers fitted on the navigator's starboard side wall, along with the Type 50 mounting controller. Using input derived from the Green Satin Radar the Type 50 mounting would be set up to give a “square” picture unaffected by drift.

T35 Camera Controllers Starboard Side of Nav Compartmet

PRONE POSITION Day Role operations could also be controlled from the prone (bomb aimer) position. Using pre-flight fitted Type 35/50 controllers as well as the passive Banana Photo sight or the Type 1 gyro controlled Photographic sight. The Night Role, after being initially set up from the back seat, would be controlled from here. Photo flash aiming was achieved by a gyro stabilised bomb sight Type T3 or T4.

Banana Sight For Use In Prone Position	Banana Sight In Use (Crown Copyright)

PYROTECHNICS The aircraft was designed to carry either a 150 capacity crate of 1.75inch flares or a flare carrier of five 8inch magnesium flares. These were initially released by the navigator pressing the flare release button/camera start button. Both systems were then controlled by pulses derived from the camera circuitry to release flares at pre-determined intervals. The cameras being triggered to take photographs by the output of the rear camera bay mounted photo cells. A pre-requisite to this of course was that the flare bay doors had to be in the open position. Controlled from a pilot operated switch (on his port console), hydraulically operated clam shell doors retracted in to the fuselage arming the circuits to the flare carriers when fully retracted. The flare bay doors doors were similar in construction and operation to a standard Canberra's bomb doors, just shorter. The camera door switch on the same pilot's console operated hydraulically controlled forward, centre and rear camera bay doors. Once fully open, exposing the optically flat and air demisted camera windows, allowed the camera magazines to be wound on to provide fresh film ready for the proper work to begin. The pilot's job then was to follow the navigator's instructions to the letter. Because you brought back to base the results (good or bad) of your efforts you could be judged accordingly. F95 CAMERAS A wealth of options became available with these cameras. In the PR.3 and PR.7 they were only available to be fitted in the forward camera bay. Official Air-to-Air photography became viable for the first time from a camera controlled and aimed almost exclusively by the pilot.

Forward Camera Bay With F95 Showing

F95 Camera Mounted in Forward Camera Bay

A brief mention should be given to the sighting method employed by the pilot to aim the lens of the fixed position F95. Remember you had to move the whole aircraft to get the required picture in the frame. A wax black marker pencil would be used to mark a cross on the inside of the double glazed canopy and another cross marked on the outside, lining up the two marks meant, if your calculations and marking were correct, your objective would be centre frame. This could be a long and arduous process on the ground with the pilot shouting instructions to his navigator wandering about well in front of the aircraft with various hand-held 'targets'. FINALLY . . . Testimonials to the Canberra’s effectiveness as a PR aircraft are widespread; credit is due to a large part to the navigators who took on this black art. A much longer and more intense training period, coupled with a selection process ensured that only the best went on to become PR navigators enabling the Canberra PR marks to serve us well and with distinction for many years during and after the Cold War. Canberra PR3, WF922, at the Midland Air Museum is fitted with a working F52 camera, a fitted F49 survey camera and a pair of F95 cameras in the forward camera bay. Visitors can arrange to see and photograph this installation by asking at reception. Depending on guide availability it is not always possible to power-up the aircraft. Please phone before visiting to avoid disappointment.

M Lambert, 2008