by Damien Burke
Canopy Jettisoning and/or Escape Hatches
46. Apart from any arrangements that may be made under paragraph 45, it must be possible to jettison the canopy and/or escape hatches by simple hand operated mechanical controls to enable the crew to leave the aircraft quickly in the event of ditching or crash landing.
Armour Protection
47. The aircraft is to be designed with a view to reducing vulnerability. Wherever possible structure or equipment is to be placed so as to provide protection for the crew and important components of the aircraft. The possibility of providing some armour below and behind the crew positions is to be examined and the penalties involved made known to the Air Staff.
TARGET DATE
48. The Air Staff require this aircraft in Service in 1964 or as soon thereafter as possible.
Air Ministry, (D.O.R (A))
March 1957.
APPENDIX II
Operational Requirement 343
The following is the text of the operational requirement that TSR2 was built to satisfy. It is based on the first issue of the OR, as covered by BAC’s original development contract. Compared with GOR.339, the major differences were that top speed was increased from Mach 1.7 to 2.0; low-level flight decreased to 200ft (60m) from 500ft (150m); and runway requirements were made stricter, with take-off distances halved and surface quality reduced. Several modifications were made to this requirement through the project’s life span; first of all in issue 2 in May 1961, which introduced several changes, followed by five amendment lists (AL1 to AL5 from August 1961 to June 1963), each of which made small changes. All of these changes are noted in italic.
SECRET
Air Staff Requirement No. O.R.343
TACTICAL STRIKE/RECONNAISSANCE AIRCRAFT
INTRODUCTION
By 1965 a new aircraft will be required by the Royal Air Force for tactical strike and reconnaissance operations using nuclear and conventional weapons. Such an aircraft will enable the Royal Air Force to continue to provide tactical support for the Army, to make an effective contribution to the strength of SACEUR’s shield forces, and our other Regional Pacts.
It is the Air Staff’s primary intention to exploit to the full a combination of high speed with low altitude and thus gain all possible advantage from the difficulties which an enemy will face in producing an effective defence in these conditions, The aircraft’s operational flexibility will, however, be greatly enhanced by a Mach 2 capability at medium altitude.
Importance is attached to the provision of a system which will permit effective delivery of nuclear or HE weapons from low altitude in poor visibility and at night. An alternative delivery capability from medium altitudes is also required.
Of equal importance is the provision of a comprehensive system for all-weather reconnaissance, thus giving the aircraft a major alternative role.
The flexibility of role and tactics outlined above is dependent upon a comparable ground flexibility. This can only be realised by an ability to use small airfields with rudimentary surfaces and restricted maintenance facilities.
To advance a study into the possibilities of combining likely developments in aircraft and equipment design in time to meet the required In Service date of 1965, the Air Staff issued a General Operational Requirement, GOR.339, to the MoS in March 1957. This stated in broad terms the outline of this Operational Requirement. The following Operational Requirement is based upon analysis by the Air Staff and MoS of the studies of GOR.339 made by the Aircraft Industry and the Research Establishments.
The dependence of the aircraft upon its equipment to enable it to exploit fully all weather conditions, and to deliver accurately its weapons, necessitates a Weapon System approach to the problem. By this approach all aspects of the aircraft, its weapons and associated equipment are to be designed and developed concurrently, and mutually, so that the final product is a complete and integrated air weapon. Without compatible ground equipment the capabilities of the aircraft weapon system will be nullified, and adequate attention must be paid to this aspect of the requirement.
REQUIREMENT
The Air Staff require a Tactical Strike and Reconnaissance Weapon System to the requirements which follow.
ROLES OF THE AIRCRAFT
The aircraft is to undertake the following roles:-
To obtain reconnaissance information for all tactical purposes, including target mapping at low altitudes, under all-weather conditions by day and by night using radar and/or photographic methods.
To deliver effectively tactical nuclear weapons from low altitudes at the maximum ranges obtainable, and with minimum consideration for the prevailing weather conditions, by day and by night.
To deliver effectively high explosive weapons as an alternative to the tactical nuclear weapon.
To increase the flexibility of the weapon system an alternative medium-altitude strike and reconnaissance capability is required.
GENERAL DESIGN REQUIREMENTS
The Air Staff require the aircraft design to incorporate two engines.
No defensive armament is required. In order to minimise the effect of enemy defences, primary emphasis will be given to penetration to, and escape from, the target at low altitude. The design is to provide the best possible gust response characteristics, consistent with the airfield performance specified, in order to ensure the maximum operating efficiency of the crew. Low-altitude operations may be carried out down to 200ft or less above ground level. Under blind conditions periodic ascents to 1,000ft to increase the radar fix acquisition will be acceptable if the navigation system so demands. Such ascents will not be made within 50nm of the target except as necessary during weapon delivery.
It is accepted that strike and high-grade reconnaissance will not be combined in a single sortie. However, as every opportunity must be taken at all times to obtain reconnaissance information, the aircraft will be required to carry out the maximum photographic and/or radar reconnaissance without prejudice to the strike role.
The servicing time needed for changing roles should be as short as possible and must be less than 6 hours under airfield servicing conditions. The turn round time between sorties when used in the same role is to be as short as possible.
The aircraft and its ground equipment is to be weatherproof and remain serviceable with only the minimum of routine attention for 30 days in the open. The aircraft is to be weatherproof in flight and is to be suitable for operations in any part of the world.
PERFORMANCE
Speed
Penetration to target at sea level is to be used at a speed of not less than 0.9M with an ability to make a short burst at supersonic speed provided that this can be done without affecting the design of the weapon system. An ability to attain 2.0M at the tropopause is required.
Radius of Action
Without resort to in-flight refuelling or overload fuel tanks the aircraft is to be capable of attacking targets at a radius of action of at least 1,000nm
A ferry range of at least 2,500nm in still air without overload fuel or inflight refuelling is required.
Sortie Profiles
A typical 1,000nm radius sortie profile is to comprise:
Take-off and climb economically to cruise altitude.
Cruise economically to a point approximately 650nm from base.
Accelerate to and cruise at a speed exceeding 1.7M for 100nm.
Descend at maximum speed to low altitude.
Fly 200nm at a height of 200ft or less above ground level at a speed not less than 0.9M.
Deliver a 2,000lb weapon.
Return to 200nm from the target at low altitude at a speed not less than 0.9M.
Climb to cruising altitude and return to overhead base at economic speed.
Descend to base to arrive with fuel reserves to permit 8 minutes loiter at 1,000ft above ground level plus 5% of the total internal fuel.
For a shorter tactical sortie of not less than 450nm radius of action typical flight profiles might comprise
either:-
A high/low approach to the target including 100nm supersonic cruise at altitude and 200nm at low altitude at a speed not less than 0.9M.
[Issue 2: ‘supersonic’ replaced by not less than 1.7M]
or
A low-altitude flight all the way to and from the target at a speed not less than 0.9M. The Air Staff would like to be informed of any penalty involved in this.
The fuel load is to enable either flight profile to be accomplished with fuel reserves to permit 8 minutes loiter at 1,000ft above ground level plus 5% of the starting fuel.
[Issue 2: ceiling of continuous operation at 56,000ft added]
Runway Performance
It is the intention normally to operate the aircraft from airfields having paved runways about 2,000yd in length, when safety margins are required. However, under the threat of an attack it will be necessary to disperse to semi-prepared airstrips, or existing airfields, whose length may be less than 1,500yd and which may have surfaces which have deteriorated or are rudimentary. When such dispersed, or emergency, operations are undertaken some abatement of the margins of safety during takeoff and landing may be accepted.
To enable the maximum number of inferior airfields to be used the aircraft must require the shortest practicable ground roll. Take-off and landing procedures which will exploit to the fullest extent the capabilities of the aircraft may be adopted.
The aircraft is to be capable of operating from the widest variety of airfield surfaces which may be undulating or uneven. The lowest possible runway classification number (LCN) is required and LCN, as near to 20 as possible should be aimed at. Tyre pressures should be such that the risk of rutting the airfield surface is minimised.
It must be appreciated that it may, on occasions, be necessary to make a landing as soon as possible after take-off and the undercarriage design must permit the greatest possible landing weight.
Operations under Normal Conditions
Take-off. In conditions of still air, or in a steady crosswind of 35kt at right angles to the runway, in a temperature of ISA +30°C at sea level, the aircraft is to be capable of taking off with a ground roll of less than 1,300yd. The takeoff weight is to enable the 1,000nm radius sortie to be accomplished.
Landing. In conditions similar to those in para. 25 above the aircraft is to be capable of being stopped on a wet runway with a ground roll less than 1,300yd. The landing weight is to include 2,000lb in the weapon bay plus 10% of the total internal fuel.
Operations Under Emergency or Dispersed Conditions
Take-off. The aircraft is to be capable of taking-off in a temperature of ISA +30°C at sea level with a ground roll of less than 1,000yd for the 1,000nm radius sortie, or less than 600yd ground roll for the 450nm radius sortie in ISA conditions.
Landing. The aircraft is to be capable of being stopped in a ground roll of less than 600yd on a wet surface in ISA conditions at sea level. The landing weight is to include 2,000lb in the weapon bay plus 10% of the starting fuel.
Aids to Take-off and Landing
Rocket Assisted Take-off Gear is not required. The landing performance specified is to be met without the use of ground aids such as arrester wires. A tail braking parachute may be used if necessary. It is to be expected that at some airfields safety barriers may be available.
[Issue 2 – safety barrier sentence deleted]
NAVIGATION, ARMAMENT, RECONNAISSANCE AND FLIGHT CONTROL SYSTEMS
General Requirements
The weapon system will be effective only if it is easy to operate. The best possible aircraft handling qualities are to be realised particularly below 10,000 feet.
The navigation and flight instrument displays are to be readily and simply interpreted so that accurate height, ground speed and track can be maintained at all times.
The complete weapon system is to be so designed that it gives the enemy little or no help in detecting the approach of the aircraft, and is to have the greatest possible immunity to enemy countermeasures.
Terrain Clearance and Forward Radar
[Issue 2: terrain clearance replaced by terrain following]
Terrain clearance equipment is to be provided since this will greatly enhance the flexibility of the aircraft, reduce vulnerability by permitting flight at lower altitude, and add to operating safety. The Air Staff appreciate that the problems are complex, therefore the desired performance may not be available by the introduction date of the aircraft. The design must enable the aircraft automatically to maintain a selected height down to 200ft above the ground under all-weather conditions. Additionally, the design must permit this target to be met without major modification to the airframe should an interim equipment be found necessary when the aircraft is first introduced into Service.
A display is required which indicates the nature of the commands being transmitted by the terrain clearance equipment to the Automatic Flight Control System (AFCS) and which provides director information to the pilot.
The forward radar necessary to provide terrain clearance is to include a radar ranging mode which is to be displayed to enable rocket attacks to be launched. It is highly desirable that the forward radar provides a means of direct sighting for bombing discrete targets from medium altitude. It is accepted that the forward radar will provide indication of only one mode at a time.
The forward radar must be capable of providing homing facilities to assist in the approach and landing phase. This information may be provided in conjunction with a transponder beacon on the ground similar to that required for air to air homing for flight refuelling. See paragraph 70.
Navigation System
The navigation system is to be based primarily on precise dead reckoning corrected at intervals by selected visual and/or predicted radar fixes. The accuracy of the DR equipment is to be such that the interval between radar fixes may be 100nm, and between visual fixes 50nm The system is to permit a reasonable choice of predictable radar fixes and is to work at all heights of which the aircraft is capable.
[Issue 2: visual fix interval increased to 100nm]
The navigation system is to operate without manual adjustment between latitudes 75°N and 75°S. The accuracy of the system is not to be seriously degraded over periods of up to 2 minutes during violent aircraft manoeuvres, or during a climb or a descent. At low altitude it is to permit the aircraft to be flown along a chosen route to an accuracy of 1nm.
The navigation system is to provide, when required, a permanent record of such radar information as can be of use for reconnaissance purposes, when the special reconnaissance equipment is not fitted or not working.
Armament
The Air Staff require the aircraft to carry internally the weapons referred to below and to release them from any altitude or at any speed of which it is capable. Degradation of the specified accuracies is acceptable in extreme conditions. Additionally, the design should permit the carriage, when necessary, of weapons externally, in which case the Air Staff will accept limitations imposed by the weapons themselves.
A means of attacking a target with any weapon without the aircraft climbing above its minimum approach height is desirable.
Tactical Nuclear Weapons
Provision is to be made for the internal carriage of the tactical nuclear weapon specified in OR.1127. This weapon will be employed both at low and medium altitudes in LABS and dive-toss attacks. The following accuracies are required both with the aircraft flying at 200ft and 0.9M and at 25,000ft and 1.7M.
Visual conditions 600ft. 50% CEP.
Blind (when a suitable radar fix exists within 30nm of the target) 1,200ft. 50% CEP.
[Issue 2: external carriage of two similar weapons added; AL1: internal carriage of two tactical nuclear weapons rather than one.]
1,000lb HE Bombs
Provision is to be made for the internal carriage of four or more 1,000lb HE bombs. These bombs will be employed both at low and medium altitudes in dive and dive-toss attacks. The following accuracies are required.
/>
Visual conditions in dive attack. l00ft. 50% CEP.
Visual conditions in dive-toss attack. 200ft. 50% CEP.
[Issue 2: increased specifically to six 1,000lb bombs, and internal carriage of not less than six 25lb practice bombs added]
Rockets
Provision is to be made for the internal carriage of 24 × 3” Rockets with 60lb or alternative 24lb warheads.
or
74 × 2” Rockets.
[Issue 2: deleted, and replaced by external carriage of four 37 × 2in rocket pods.]
These rockets will be employed in shallow dive attacks in which the speed of the aircraft will be limited by kinematics of the attack and the performance of the weapons.
Air-to-Surface Guided Weapons
Provision is to be made for the internal carriage of two or more air-to-surface guided weapons to Air Staff Requirement No. OR.1173, with HE warheads. These weapons will be employed in visual attacks from low altitude. The aircraft is to provide a launching platform which will enable the ASGW to attain its accuracy capability. The Air Staff attach the greatest importance to accurate delivery of HE, and an accuracy of the order of 20ft 50% CEP at 20,000ft slant range when the aircraft is flying at 0.9M is required.
[Issue 2: deleted and replaced by external carriage of four similar weapons.]
Reconnaissance Systems
An all-weather reconnaissance capability using photographic and electronic equipment is required. This equipment is to provide reconnaissance for tactical purposes and target area mapping.
Target area mapping by electronic means is required to give ground co-ordinates for a subsequent blind attack with the accuracies quoted in paragraph 42 (b).
Photographic Reconnaissance. Photographic Reconnaissance is required at low and medium altitudes as follows:-
By Day.
Low level Oblique Cameras. Forward facing and lateral oblique cameras of the F.95 type are required in the basic aircraft for both strike and reconnaissance roles.
[Issue 2: forward facing camera realigned to vertical.]
Vertical Cameras. Vertical photography is required from 5,000ft up to the ceiling of the aircraft. In order that this requirement may be based upon existing cameras or modification to existing cameras, the Air Staff accept the possibility of having alternative camera fits based upon knowledge before takeoff of the likely operating height band. Forward coverage is to be at least 150nm in all cases, and lateral coverage of 10,000ft is required from altitudes of 20,000ft or above. Photography must be fully interpretable when taken from any altitude up to at least 35,000ft but the Air Staff are prepared to accept a scale of less than 1:10,000 from heights above 20,000ft provided that the reduction in scale is compensated by improvements in resolution.