McDonnell Douglas C-17 Globemaster III C-17B

The C-17B was a proposed tactical development of the C-17 Globemaster III that Boeing offered several times from 2007 onwards to give the airlifter access to short and austere strips that the production C-17A could not use. Although the C-17 had been designed from the outset with short-field performance in mind, the US Army's Future Combat Systems (FCS) programme, which planned a new family of medium-weight vehicles meant to be flown in close to the fight, raised the prospect of a requirement for even shorter landings on semi-prepared surfaces. Boeing offered the C-17B to the US military in 2007 precisely as the aircraft to carry those vehicles and the rest of the FCS equipment.

Boeing's package combined several structural and systems changes. The most visible was an additional main landing gear on the centre fuselage, a centre body gear intended to spread the load and allow operation from semi-unprepared strips; double-slotted flaps would increase lift for shorter take-offs and landings. The aircraft would receive higher-thrust versions of the Pratt & Whitney PW2000-family engines, an engine-out compensation system, a stability and augmentation system and an advanced situational awareness and defensive countermeasures suite. Other descriptions of the proposal also mention self-deflating tyres and a precision-landing capability. According to the figures Boeing released in May 2007, maximum take-off weight would rise from about 265 tonnes to about 279 tonnes, while the take-off distance at gross weight would shrink slightly.

C-17 programme manager Dave Bowman put the development cost of the modified C-17B at 1.5 to 2 billion dollars, against 15 to 20 billion for an all-new aircraft, and argued that if the production line kept running to around 2011 a C-17B could be ready in 2012, ahead of the planned entry into service of the FCS vehicles. The offer was closely linked to the industrial situation of the Long Beach line: production was then guaranteed only up to the last contracted aircraft, and long-lead items had been placed under a stop-work order in March 2007. For Boeing, a C-17B was a way of keeping that line busy beyond the existing orders.

The Air Force was not convinced. In October 2007 Flight International reported that Boeing was seeking the Army's support for the new version after the concept had been publicly rejected by a senior US Air Force official about a month earlier. Boeing also offered the C-17B content as a series of discrete upgrades that could be applied piecemeal to the existing fleet, and the last known public proposal dates from 2008.

The C-17B never progressed beyond a proposal. The aircraft was already expensive to operate, and from 2008 Congress began cutting the defence budget that would have paid for it. Operational experience in Iraq and Afghanistan also suggested that most missions did not need such an extreme short-field capability, since cargo could be delivered to established airfields and moved forward from there by C-130s or road convoys. No C-17B was built, and the improvements it bundled together remained on paper.