it was found that the minimum operating requirements for successful autorotation include that altitude is , and that the system keeps rotor rpm above the minimum 70% for stable recovery. The test pilots subsequently received the Iven C. Kincheloe Award for their role in the tests. Further developments At the Farnborough Air Show in July 2012, AgustaWestland announced that it was to offer a higher-weight variant of the AW609 (up to ); this model would trade some of its vertical takeoff performance for increased payload capacity. Officials from AgustaWestland have suggested that this short take off and vertical landing (STOVL) variant may be an attractive option for search and rescue and maritime operators. According to senior vice-president of marketing Roberto Garavaglia, the Italian government is interested in acquiring several AW609s for coastal patrol duties; due to an agreement with Bell, these may not feature armament. In June 2013, AgustaWestland announced that work to integrate design changes as part of a major modernisation would delay the AW609's certification by up to one year. These design changes primarily involved aerodynamic improvements, aimed at achieving a 10% reduction in drag and a significant reduction in overall weight, increasing the AW609's performance and capabilities. Separate improvement programs were underway on the aircraft's engines and avionics systems. In 2015, AgustaWestland announced the development of external fuel tanks which would permit flights carrying six passengers over three hours. In 2013, AgustaWestland was considering a US-based final assembly point for production AW609s; managing director Robert LaBelle stated that 35% of the customers for the tiltrotor are expected to come from the US market. Reportedly, the primary production line was to be located in Italy while a second production line in the US was under consideration. In 2015 AgustaWestland announced that the AW609 will be produced at its Philadelphia facility, the production site for the AW139, AW119 KXe and AW169. Two to three AW609 aircraft will be assembled there beginning in 2017, and once production matures, a second final assembly line is being considered for Italy. Leonardo develops a full flight simulator in Philadelphia to assist pilot training in the peculiarities of flying a tiltrotor. In 2015, Bristow Helicopters and AgustaWestland agreed to develop dedicated offshore oil and gas transport and search and rescue configurations for the AW609. Bristow Group signed a joint development agreement with AgustaWestland at Heli-Expo on 3 March 2015 which will allow Bristow to