An Operational Requirement, commonly abbreviated OR, was a United Kingdom (UK)

Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force and civil aviation that existed from 1918 to 1964. It was under the political authority of the ...

document setting out the required characteristics for a future (i.e., as-yet unbuilt)

military aircraft A military aircraft is any Fixed-wing aircraft, fixed-wing or rotorcraft, rotary-wing aircraft that is operated by a legal or insurrectionary military of any type. Some military aircraft engage directly in aerial warfare, while others take on su ...

or weapon system. The numbered OR would describe what intended role the

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

would be used for, e.g.,

bomber A bomber is a military combat aircraft that utilizes air-to-ground weaponry to drop bombs, launch aerial torpedo, torpedoes, or deploy air-launched cruise missiles. There are two major classifications of bomber: strategic and tactical. Strateg ...

, fighter, etc., or what type of

weapon A weapon, arm, or armament is any implement or device that is used to deter, threaten, inflict physical damage, harm, or kill. Weapons are used to increase the efficacy and efficiency of activities such as hunting, crime (e.g., murder), law ...

was required, e.g.,

gun A gun is a device that Propulsion, propels a projectile using pressure or explosive force. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns or water cannon, cannons), or gas (e.g. light-gas gun). So ...

, armament,

bomb A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechan ...

type, etc. In conjunction with any official specification, prospective manufacturers would then choose whether to design an aircraft or weapon for this particular requirement. Operational Requirements were carried over with the dissolution of the Air Ministry and the creation of the

Ministry of Defence A ministry of defence or defense (see American and British English spelling differences#-ce.2C -se, spelling differences), also known as a department of defence or defense, is the part of a government responsible for matters of defence and Mi ...

(MoD).

Other requirements

An Experimental Requirement (ER) was for an aircraft for

research Research is creative and systematic work undertaken to increase the stock of knowledge. It involves the collection, organization, and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness to ...

purposes; e.g., ER.100 in support of development of the English Electric Lightning.

Other requirements

See also

Notes

Further reading