Bell’s civil tiltrotor makes its own way toward first flight

Aviation International News » August 2001
May 21, 2008, 10:24 AM

While its bigger cousin in the Marines stays grounded, work on the civil tiltrotor is proceeding in the same Bell Helicopter hangars from which the first prototype V-22 Ospreys rolled out some 13 years ago in Arlington, Texas. While the Marines’ MV-22 has suffered through an agonizing, sometimes tragic decade-and-change of design, redesign, modification, cancellation and resurrection, the Bell/Agusta BA609 has had smoother sailing so far, albeit with one major caveat–it has yet to fly.

Engineers and technicians at Bell’s Arlington Plant 6 facility are working hard to alleviate that small detail, readying the first prototype for an initial aerial excursion Bell still vows will take place by year-end.

“The first BA609 had its engines installed last week,” a Bell spokesman told AIN in mid-July, “and we expect to begin ground runups in late October with first flight set for early December.”

Systems testing of the first BA609, especially of its Collins Pro Line 21 integrated avionics, is ongoing. The month just past saw shipment to Bell of the BA609’s flight control software from BAE Systems in Santa Monica, Calif. (The BA609 will be the world’s first fly-by-wire general aviation aircraft.)

The second prototype is nearing completion of its basic fuselage, after which it will be used for mandatory proof-loads-testing of the cockpit and proprotor structure. The aeroelastic stability of the wing and tilting nacelles will also be evaluated using this aircraft.

All of these tests are required by the FAA, which, like Agusta and Bell, is breaking ground in the BA609 certification process by combining pertinent aspects of FAR Part 25 (airworthiness requirements for transport category aircraft) with rules from Part 29 (airworthiness requirements for rotorcraft). The unique nature of tiltrotor technology (is it a fixed-wing airplane or a helicopter?) provides aeronautical certification authorities with a “neither fish nor fowl” conundrum. To smooth the BA609’s path to international acceptance, Bell had applied to Europe’s Joint Aviation Authorities (JAA) for certification of its civil tiltrotor. However, daunted by the JAA process, Bell has since withdrawn that application, opting instead for certification in non-U.S. nations on a case-by-case basis. (This move is likely driven by the fact that the bulk of BA609 sales have come from U.S. buyers.)

Future operators of the BA609 in the U.S. and elsewhere will be both cheered and sobered by the first flight of a production-configured civil tiltrotor aircraft late this year, for when that first BA609’s wheels clear the tarmac, the first payment on the roughly $10 million aircraft, set at 25 percent of purchase price, will be due. Bell maintains that while there has been some order turnover in recent months, prompted by a combination of the ongoing economic downturn and uncertainties over tiltrotor technology raised by the well publicized problems with the U.S. Marines’ MV-22 Osprey program, new orders have replaced those lost. Total backlog for the Osprey stands at “more than 80,” according to Bell/Agusta Aerospace marketing director Donald Barbour.

In its nine-passenger initial configuration (there is talk of follow-on stretched variants of the BA609) the civil tiltrotor is designed to be a 16,800-lb-mtow aircraft with a 5,500-lb useful load and enough power to perform Category A operations at its maximum weight. That payload will be transported over a no-fuel-reserve range of 750 nm with a designed cruise speed (airplane mode) of 275 kt. With an operational ceiling of 25,000 ft, the BA609 will be the world’s first pressurized production rotorcraft, with a cabin designed to a cruise pressure differential of 5.5 psi.

A total of four BA609 test items are planned, with one of them intended as a static and fatigue test article. That series of tests, aimed at putting the airframe through the equivalent of 40,000 flight hours, will begin this month and is scheduled to conclude in 2003. Not all of the flight test will be in Texas. Under the terms of the Bell/Agusta agreement, half of that work will take place at Agusta’s Cascina Costa, Italy plant, where Agusta will have two of the prototype BA609s. Assuming all goes well, FAA certification will be granted in December 2003, with launch customer deliveries beginning a month later.

No Layoffs

While all this is going on, Bell is denying published reports that it is laying off personnel in the face of a production slowdown of the embattled Bell Boeing MV-22 Osprey. A reduction last spring of 60 machine workers who cut and grind components used in the transmissions, gearboxes and drivelines of Bell helicopters and the Osprey was said by the company to be in response to the “normal ebb and flow” of business at the company.

The Pentagon has ordered production of the military tiltrotor to be slowed to the bare minimum rate required to keep its production line open while Bell Boeing and military engineers implement a lengthy list of changes in the aircraft’s flight control, hydraulic and software systems. That list of changes resulted from the top-to-bottom program review ordered after two crashes last year–one in April and the other in December–that killed a total of 23 Marines.

Those accidents and the investigations that followed prompted charges of data fabrication amid indications of a high-level conspiracy to use that false data to create a impression that the Osprey was more operationally ready than it really is. The remaining eight Ospreys in the Marines’ fleet are still grounded and will stay that way until cleared for flight. Neither Bell Boeing nor the military has said when that restriction will be lifted.

Meanwhile, “reduced production” means a total of 11 Ospreys will be built this year, with another 12 planned for assembly and completion next year. Before the ongoing modification and investigation program that mandated this reduced production rate, plans had called for the manufacture of 20 Ospreys next year. (The December crash of an MV-22 near New River, N.C., that killed four Marines took place just one week before the Pentagon’s go/no-go production decision was due.)

Barriers unrelated to technology woes also remain for the Osprey program. The Department of Defense’s inspector general’s investigation into data falsification by Lt. Col. Odin Leberman, commanding Marine tiltrotor training squadron 204, has reportedly branched out in many unplanned directions and consumed far more time than previously expected. No charges have yet been filed but legal proceedings are expected.

Software flaws were chief among the faults cited as causes of the December 11 New River crash, a mishap that started when badly chafed titanium hydraulics lines began to leak. In the words of the post-accident report: “The hydraulic failure in the left nacelle resulted in a series of rapidly cascading warning indicators to the pilots. Chief among these were dual-hydraulic failure and a critical swashplate fault, combined with illumination of the primary flight-control system warning light accompanied by a warning tone. The published procedure for responding to such a failure is to press the primary flight-control system reset button. [When this was done,] a software anomaly caused significant pitch and thrust changes in both proprotors. Because of the dual hydraulic failure on the left side, the proprotors were unable to respond at the same rate. This resulted in uncommanded aircraft pitch, roll and yaw motions, which eventually stalled the aircraft.”

Subsequent investigation discovered that some modes of the flight-control software had not been tested. Tests of this computer control code, critical in a triple-redundant fly-by-wire aircraft, is a key part of the  Marine-mandated ongoing program course correction. Software is now undergoing test “until failure.”

What Makes It Fly? Funding

As if all the technological and political uncertainty surrounding the Osprey program weren’t enough, current fiscal year funding is also dicey. Reduced production rates means short-term savings for the Department of Defense, some $475 million worth. However, the Pentagon wants to allocate $80 million of that to cover the cost of MV-22 program fixes.

Meanwhile, as usual, Congress has different ideas. The House wants to add $40 million to the program fix budget but cut another $115 million from the Pentagon’s $475 million procurement kitty. The Senate feels more generous, however, and is willing to shave only $80 million from Osprey procurement. A planned conference committee hearing has been tasked with resolving these conflicting numbers.

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