The case for the tiltrotor

As the US Army aviation community gathers in Nashville for the annual Mission Solutions Summit – where industry will be provided updates on various army upgrade programmes – our cover story in the latest issue of Defence Helicopter features one platform the service doesn’t fly.

While there are far fewer USAF CV-22B Ospreys in service than those flown by their Marine Corps brethren, the use of the tiltrotor for special operations missions over the past decade has equally changed the way the USAF does business.

We recently gained a valuable insight in what it takes to prepare crews to fly the CV-22, with intrepid reporter Barry Smith spending several days with the training unit, the 71st Special Operations Squadron (SOS), at Kirtland AFB, New Mexico.

The Osprey is tailor-made for the vast distances encountered in many of the regions the US finds itself operating in, thanks to such features as an aerial refuelling capability, allowing the USAF and USMC to ‘collapse speed and distance’, in the words of one marine commander.

However, despite a decade of intense and relatively incident-free operations, the fatal accidents that dogged the V-22’s development continues to cast a long shadow. One obvious manifestation of this has been the public reaction in Okinawa to MV-22 operations there, particularly after an accident on 13 December that temporarily grounded the fleet. Given Japan itself is purchasing the V-22, it will be interesting to watch how that shapes public perception there in the years to come.

The suitability of the tiltrotor in meeting the gamut of demanding military missions will also be placed further under the spotlight by the US Army, as it works through the Future Vertical Lift programme in the years ahead.

And that question takes us back to Kirtland AFB, where the 71st SOS has a training syllabus that is finely honed to the unique challenges of flying the V-22.

The training focuses on the importance of CV-22 pilots and special mission aviators (SMAs) – essentially a combination of the flight engineer and loadmaster career fields with many other duties – working together, particularly given the famous rotor downwash of the Osprey, which requires close crew coordination to land in an unimproved landing zone.

Collective dyslexia

One of the biggest personal challenges transitioning from helicopters to the V-22 is the added control input of changing the angle of the engine nacelles, something the commanding officer of the unit said resulted in ‘collective dyslexia’. While this does require some getting used to, ‘everyone figures it out just fine’.

The danger of entering a ring vortex state, which was a serious problem in early USMC tiltrotor operations, is also now well understood and students are taught how to avoid it. They are also shown how to stay out of the rotor wash of other V-22s with very specific techniques and parameters.

This is not unique to the V-22 and, as the commander correctly pointed out, all aircraft have parts of the flight envelope to avoid.

Operating the V-22 will remain within the reach of very few militaries around the world, given the aircraft’s procurement and sustainment costs. While the speed and range of the platform are clearly unmatched by any other VTOL aircraft, the smaller proprotors limits the V-22’s ability to go into a hot, high-altitude landing zone at a high gross weight. In such conditions, a helicopter such as the CH-47 Chinook may well be the better choice.

Nevertheless, the story of the 71st SOS and the effectiveness of the CV-22 training programme is a provocative one in the context of the US Army’s current examination of tiltrotor versus compound coaxial for its future rotorcraft fleet.

Bell Helicopter is developing its V-280 tiltrotor as part of the army’s Joint Multirole – Technology Demonstrator effort, while Sikorsky-Boeing is advancing the SB>1 Defiant co-axial compound helicopter for the requirement – the latter recently announcing the maiden flight of the Defiant will be delayed to the first half of next year.

Despite facing off against the two industry giants in the sector, Bell will be no doubt hoping that established operations with the V-22 across three of the services will help tilt the race in its favour.

For more on the operations of the 71st SOS, see the May-June issue of Defence Helicopter

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