A short takeoff and vertical landing (STOVL) variant aircraft, the F-35B is similar in size to the Air Force F-35A,
trading fuel volume for vertical flight systems. The F-35''s main power plant comes from Pratt & Whitney''s F119 or GE Rolls Royce fighter team''s F136, with the STOVL variant of the latter incorporating a Rolls-Royce Lift Fan module.
Expected to be available beginning 2012, F-35B variant is intended to replace the later derivatives of the Harrier Jump Jet, the world''s first operational short takeoff / vertical landing fighter/ground attack aircraft. The RAF and Royal Navy will use this variant to replace the Harrier GR7/GR9s. The US Marine Corps will use the F-35B to replace both its AV-8B Harrier II and F/A-18 Hornet fighters.
Weaponry: 1 × GAU-12/U 25 mm cannon — slated to be mounted
internally with 180 rounds in the F-35A and fitted as an external pod with 220 rounds in the F-35B and F-35C
Internally, up to four AIM-120 AMRAAM, AIM-9X Sidewinder or AIM-132 ASRAAM internally or two air-to-air and two air-to-ground weapons (up to two 2,000 lb weapons in A and C models; two 1000 lb weapons in the B model) in the bomb bays. These could be AMRAAM, the Joint Direct Attack Munition (JDAM) — up to 2,000 lb (910 kg), the Joint Standoff Weapon (JSOW), Small Diameter Bombs (SDB) — a maximum of four in each bay, the Brimstone anti-armor missiles, Cluster Munitions (WCMD) and High Speed Anti-Radiation Missiles (HARM).
The MBDA Meteor air-to-air missile is currently being adapted to fit internally in the missile spots and may be integrated into the F-35.