excessive radiation exposure. Other roles Since the type's inception, the Chinook has carried out various secondary missions, including medical evacuation, disaster relief, search and rescue, aircraft recovery, fire fighting, and heavy construction assistance. In February 2007, the Royal Netherlands Air Force became the first international customer of the CH-47F model, expanding their Chinook fleet to 17. On 10 August 2009, Canada signed a contract for 15 extensively modified and upgraded CH-47Fs for the Canadian Forces, later delivered in 2013–2014 with the Canadian designation CH-147F. On 15 December 2009, Britain announced its Future Helicopter Strategy, including the purchase of 24 new CH-47Fs to be delivered from 2012. Australia ordered seven CH-47Fs in March 2010 to replace its six CH-47Ds between 2014 and 2017. In September 2015, India approved purchase of 15 CH-47F Chinooks. On 7 November 2016, Singapore announced that the CH-47F would replace its older Chinooks, which had been in service since 1994, enabling the Republic of Singapore Air Force to meet its requirements for various operations, including Search and Rescue (SAR), Aeromedical Evacuation (AME), and Humanitarian Assistance and Disaster Relief (HADR) operations. In February 2020, the Indian Air Force started using Chinooks at theatres such as Ladakh and Siachen Glacier to assist Indian forces deployed at the Indian borders with China and Pakistan. Variants HC-1B The pre-1962 designation for Model 114 development aircraft that would be redesignated CH-47 Chinook. CH-47A The all-weather, medium-lift CH-47A Chinook was powered initially by Lycoming T55-L-5 engines rated at , but then replaced by the T55-L-7 rated at engines or T55-L-7C engines rated at . The CH-47A had a maximum gross weight of , allowing for a maximum payload around Initial delivery of the CH-47A Chinook to the U.S. Army was in August 1962. A total of 354 were built. ACH-47A The ACH-47A was originally known as the Armed/Armored CH-47A (or A/ACH-47A). It was officially designated ACH-47A as a U.S. Army Attack Cargo Helicopter, and unofficially referred to as Guns A Go-Go. Four CH-47A helicopters were converted to gunships by Boeing Vertol in late 1965. Three were assigned to the 53rd Aviation Detachment in South Vietnam for testing, with the remaining one retained in the U.S. for weapons testing. By 1966, the 53rd was redesignated the 1st Aviation Detachment (Provisional) and attached to the 228th Assault Support Helicopter Battalion of the 1st Cavalry Division (Airmobile). By 1968, only one gunship remained, and logistical concerns