The Bell Boeing V-22 Osprey is set to evolve significantly during the next decade through block upgrades, but some desired improvements face increasing pressure from rising concerns about aircraft weight and cost.
In the 18-month flight pause from December 2000, the programme settled on a plan to sequence a long list of upgrades recommended following two fatal V-22 almost five years ago. The upgrade strategy has been divided into three blocks.
The Block A upgrade programme – almost complete – provides the USMC with a "safe and operational aircraft" and is the standard configuration for the eight aircraft entering an operational evaluation period as soon as next month. After the test period, part of the Block A fleet will transition into the V-22 training unit, while the others will later be modified to the next block design.
Block A focused on redesigning the V-22's pivoting nacelles, including expanding hydraulic line clearances, re-working the electrical wiring design and a new detailed pattern for claming bundles of cables and tubing in the engine.
Block B is intended mainly to introduce reliability improvements, such as installing clam-shell doors on fuselage panels to improve access for maintainance. It also includes an active vibration suppression system to improve the cabin environment as well as reduce stress on airframe parts, and flight control software changes and de-icing system improvements.
"The first aircraft is going to be delivered shortly from Philadelphia," says Bob Ellithorpe, Bell's V-22 programme manager. "They've already incorporated the Block B changes into the fuselage. And we will deliver the first Block B aircraft, which is aircraft 70, in December of this year."
Programme officials, however, are closely watching the Block B weight target. Design reviews indicate the aircraft is meeting weight targets, but have also identified a risk of a 115kg (250lb) weight growth beyond the aircraft's limits. The Block B design cannot remain over weight targets without prompting a change to the joint operational requirements document that authorises the programme's acquisition strategy.
Meanwhile, programme officials are close to approving the final design this year for a Block C configuration, which would seek to incorporate several mission enhancements. A key element of Block C would be a Link 16 datalink capability. Other Block C candidates include a backup GPS navigation system, weather radar, forward firing ALE-47 countermeasures dispensers and a night vision goggle-compatible head-up display.
The programme's long-held desire is to incorporate a gun into the block upgrade strategy, but that goal appears to be unlikely to overcome affordability concerns. USMC officials have evaluated several options for installing an "interim gun system" on the V-22 ramp. A major weight penalty was always expected, but the review's findings of an average cost of about $1 million per aircraft came as a surprise.
"Right now, none of [the options] are affordable," says Colonel Keith Berkholz, USMC head of aviation weapon systems. Berkholz adds however that the MV-22B's unique flight characteristics could help mitigate a move to shelve the weapon upgrade. He explains that combat support helicopters operating in "hot" landing zones need a rear-firing weapon, especially during a relatively slow ascent and horizontal flight away from hostile fire.
The tiltrotor's ability to transition to forward flight dramatically reduces the aircraft's vulnerability to ground fire, as does the ability to fly higher than a helicopter. In addition, Berkholz says, the V-22 is less vulnerable than a helicopter to armour-piercing bullets.
The CV-22 flight test schedule has been plagued by delays, but a new push in March aims to set the programme back on track. Current plans call for the CV-22 US Air Force special operations variant to begin operational evaluation in mid-2006.
However, by late-January the two-aircraft test fleet based at Edwards Air Force Base, California, was off-schedule by about six months, say programme officials. The CV-22 test team is waiting for a third aircraft to be delivered in March. That addition is being counted on to boost availability rates and close the schedule gap within 18 months.
STEPHEN TRIMBLE / WASHINGTON DC
Source: Flight International
