Plans for a next generation vertical airlifter to support all branches of the US military are gathering pace, writes Paul Derby
Bell Helicopter's Quad Tiltrotor (QTR) programme could be the key beneficiary of a rapidly emerging joint requirement for an advanced vertical airlifter destined for the US armed forces.
The US manufacturer is in the early stages of a development programme for the proposed aircraft, which would take tiltrotor technology to a fresh level, but now has a clear market to aim at.
Until very recently there was little cohesion in the future airlift plans of the USMC, the US Army and the US Navy. Each recognised it required a platform capable of transporting a 20t payload into combat zones, as part of a highly networked Future Combat System (FCS), but beyond that co-operation was limited.
US Department of Defense officials have now won support from both the US Army and the US Navy for a common specification, lending a critical element of cross-service support to the project. A joint requirements document that clears the way to launch a development programme is now being drafted and should be finalised by the end of the year.
All this is good news for Bell and the QTR. The aircraft is by no means the only contender, but its combination of a fuselage larger than the C-130 Hercules, 300mph-plus speed, range in excess of 1,000 miles and vertical take off and landing capability gives it a distinct edge over competing designs.
A variety of ideas has been proposed by potential bidders to date, including tiltwings, tiltrotors, fan-in-wing, super-short take-off and landing aircraft (SSTOLs), plus coaxial and compound helicopters. A Lockheed Martin C-130-sized gyrodyne was also touted.
These ideas were studied in detail following a decision by Michael Wynne, undersecretary of defense for acquisition, technology and logistics, to form the Joint Vertical Airlift Task Force (JVATF). Chaired by Wynne aide Michael Walsh, JVATF was asked in August 2003 to examine the US military's fleet of roughly 5,500 helicopters, and make broad recommendations for modernisation investments and ways to address capability shortfalls. The heavylift element of the modernisation was seen as the most pressing.
Designing an all-new heavylift transport posed the greatest technical challenges. Breakthroughs would be required in propulsion and airframe materials. The study noted that there was no vertical take-off and landing-capable engine with a 15,000shp (11,175kW) rating, the minimum power requirement for the heavylifter.
The task force also identified that it would take a huge development effort for an operational aircraft to arrive between 2020 and 2025.
The JVATF's recommendations included launching a $2.5 billion research effort spread over four or five years, starting in fiscal year 2006. The science and technology phase would then be followed by a roughly 10-year system development and demonstration effort worth at least $10 billion.
It was judged that no single service could afford the fiscal and technical challenge of leading such an effort alone. The JVATF recommended that the requirements of all three services with an existing need - the army, navy and USMC - be combined into a single development programme, based on the Lockheed Martin F-35 Joint Strike Fighter model. The scale of the undertaking also suggested to the JVATF that an international partnership should be considered. NATO, France and Germany each have a requirement for a similar heavylift requirement, and EADS subsidiary Eurocopter is working on its own vertical transport requirement.
Bell's development efforts on the QTR, closely aligned with the company's recently formed XworX research body, progressed last year with the start of wind tunnel testing at Texas A&M University's low speed wind tunnel.
Advanced technology work in the field of flow control is ongoing to reduce QTR drag and increase payload by reducing download. More producible actuators are being investigated, which Bell says will be considered for its BA609 civil tiltrotor and the V-22 if successfully developed.
In parallel to developments taking place at industry level, US armed forces strategists began to insert the theory of a new heavylift vertical transport into futuristic wargames. Very quickly, a new warfighting doctrine began to take shape called mounted vertical manoeuvre (MVM).
The doctrine called for an aircraft capable of carrying payloads of vehicles and equipment weighing at least 20t hundreds of kilometres behind enemy lines, according to Maj Al Huber of the Army Aviation Centre's Directorate of Combat Development. "MVM allows the theatre commander to place significant mobile combat power suddenly at almost any location on the battlespace."
According to Huber the results showed the high-speed VTOL aircraft "was the most efficient means of force delivery". He said that the tiltrotor's high speed reduced demand for fuel, the vulnerability of the aircraft and the risk of crew fatigue.
Source: Flight Daily News