The state-of-the-art aircraft is believed to be the fastest civilian helicopter on the market and replaces the charity's seven-year-old former air ambulance.
It was officially unveiled yesterday morning, at Althorp House, in Northamptonshire, befo
re embarking on its first day of work.
The new air ambulance, which is leased by the charity and is not a one-off capital cost, is capable of top speeds of almost 200mph and will mean stricken patients will be delivered to hospital quicker than ever.
Andy Williamson, chief executive of the WNAA, said the helicopter would also help crews deliver better, safer care to victims of serious accidents.
He said: "It is the fastest civilian helicopter that you can buy and it can take off in under one minute.
"Like any piece of machinery our old helicopter suffered from general wear and tear. This helicopter replaces it and has more up-to-date equipment so we are very excited to have it."
The new aircraft will increase reliability and host a new patient monitoring system, as well as an impressive new stretcher system.
The new generation stretcher, which automatically rotates and glides out of the aircraft door, is aimed at reducing lifting and handling and improving patient comfort.
Steve Porter, clinical supervisor for WNAA, said: "To us this means we can do so much more on the scene.
"We have always been able to deliver front-line medicine to patients but we will really be able to push the boundaries now."
As well as being faster and better equipped, the new helicopter can carry heavier loads, meaning additional casualties or doctors can be carried on board.
The extra space will also mean the staff are able to deliver life-saving operations and even carry out chest surgery on board.
Steve, who has been with WNAA since it was launched in October 2003, said he was delighted to welcome the new helicopter to the team, even if it meant saying a sad goodbye to the old one.
He said: "It is very sad to say goodbye to the old one. It has been with us from day one and it has served us very well.
"A few people shed a few tears but she is an old lady and she is ready for the retirement home now.
