F-35 Lightning II has three different variant that use conventional take-off (CTOL / Conventional Take-Off and Landing / F-35A), STOVL (Short Take-Off and Vertical Landing / F-35B) and CATOBAR (Catapult Assisted Take-Off but Arrested Landing / F-35C) methods. Thus, platforms have some structural changes for these abilities.
F-35B Lightning IIs of the Royal Air Force (RAF) will fly without a cannon. The UK Ministry of Defence said in a statement that there is currently no gun pod acquisition plan.
To ensure STOVL capability, the F-35B Lightning IIs feature a lift fan system under the retractable door in the mid-section of the fuselage. The equipment in question changes the internal system layout of the B model aircraft. For this reason, the internal fuel capacity of the platforms decreased compared to the A and C models. In the CTOL variant, 25 mm cannon equipment on the left inner part of the body was cancelled. A solution was made to load the 25-mm GAU-22 gun, which comes as standard in the F-35A Lightning II, can be used as an optional pod in the F-35Bs, which can be attached to the centerline of the aircraft.
Following the retirement of the Harrier GR.9 and GR.9A of the Royal Navy and Royal Air Force inventory, the UK decided to procure only the F-35B Lightning II.
Weighing 104 kilograms, the GAU-22 / A can fire HEI and API ammunition. The weapon, which can operate with linked or linkless feed system, has 16,5 kN recoil force.
