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The Bell-Boeing V-22 Osprey

v1.0.0 / 01 jul 17 / greg goebel

* In the 1950s and into the 1960s, a large number of prototype "vertical takeoff & landing (VTOL)" aircraft were developed, most of which amounted to little. However, they did eventually lead the way to operational VTOL aircraft -- a significant example in the 21st century being the Bell-Boeing "V-22" Osprey, which is now in operational service. This document provides a history and description of the V-22, and the Bell "XV-15" demonstrator that preceded it -- as well as to the emerging Leonardo "AW609" and Bell "V-280 Valor" VTOL machines, both along the same lines as the V-22.

Bell-Boeing MV-22B Ospreys


[1] THE BELL XV-15
[2] MV-22 OSPREY: ORIGINS
[3] OSPREY IN DETAIL
[4] CV-22B / CMV-22B / OSPREY IN SERVICE
[5] AW609 TILTROTOR
[6] BELL V-280 VALOR
[7] COMMENTS, SOURCES, & REVISION HISTORY

[1] THE BELL XV-15

* From World War II, there were studies for and experiments with vertical take-off & landing aircraft that used props or wings that rotated to the vertical for takeoff and landing, and to the horizontal for normal flight. Such "tiltrotor" and "tiltwing" machines as were built had varying degrees of flight success, but none entered production.

In the mid-1950s, the Bell Helicopter Company developed a primitive experimental tilt-rotor, the "XV-3", performing trials with it into the mid-1960s. Following up on the work with the XV-3, Bell proposed moving on to an operational tiltrotor, the "Model 266", for a US Army requirement for a light tactical transport. It would be powered by twin General Electric (GE) T64 turboshafts and be able to carry 30 passengers.

The XV-3 had been something of an experimental "kluge", nothing like a practical aircraft, and the Army felt that more research was needed before committing to development of an operational machine. The US National Aeronautics & Space Administration (NASA) had been conducting ongoing research on VTOL aircraft, the NASA Ames Research Center in California having initiated design studies for a tilt-rotor demonstrator aircraft in 1971. Following up on that work, in 1973 the US Army Air Mobility Laboratory and NASA Ames awarded Bell a contract to built two "Model 301 Research Tiltrotor" aircraft, to be given the military designation of "XV-15". The first prototype performed its initial free flight on 3 May 1977, with the second prototype following on 23 April 1979.

The XV-15 was still a purely experimental machine, with no real operational capability, but it was far more refined than the XV-3, indeed being trim and futuristic in appearance. It was built primarily of aircraft aluminum alloy; it had a high wing with a 6.5-degree forward sweep -- it seems to ensure proper center of gravity in vertical flight -- and a 2-degree dihedral, plus a twin-fin tail with swept tailfins. Flight surfaces were conventional, including flaps, flaperons, elevators, and rudders; all under manual control with hydraulic boost.

The XV-15 had a rotating engine pod at each wingtip; the engines could pivot under electro-hydraulic actuation from horizontal to five degrees beyond the vertical. Each pod featured an Avco Lycoming LTC1K-4K turboshaft, driving a three-bladed stainless-steel rotor with a diameter of 7.62 meters (25 feet). The LTC1K-4K was a T53-L-13B turboshaft, providing 1,155 kW (1,550 SHP), modified to operate vertically.

Bell XV-15 demonstrator

The two engines were linked by a driveshaft, allowing the aircraft to stay in the air if one engine failed; if both engines failed, the rotors would auto-rotate at the same RPM, to prevent the aircraft from rolling over as it fell to ground. There were twin bladder fuel tanks in each wing, total fuel capacity being 830 liters (219 US gallons), Each engine could draw fuel from both tanks. An auxiliary fuselage tank was later added to increase fuel load by 64%.

The XV-15 featured a climate-conditioned cockpit for two crew, with dual controls and side-by-side seats for pilot and copilot, both sitting on Rockwell-Columbus LW-3B ejection seats -- originally designed for the Rockwell OV-10A Bronco battlefield spotter aircraft. Cockpit layout was analog, flight control was by stick and rudder. The controls worked conventionally in airplane mode, the stick operating as a helicopter-style collective control for up and down movement, the rudders operating as cyclic controls, for directional movement. Each pilot had two switches to control rotor tilt -- one giving continuous tilt across the entire tilt range, the other giving tilts at presets including 0, 60, 75, and 90 degrees relative to the horizontal. There was a emergency control, used in case of electrical system failure, that flipped the nacelles up into helicopter mode.

There was a cargo compartment behind the cockpit, for accommodating test kit, additional crew, or baggage and such for flights to remote test locations. The entry door was on the left side of the cargo compartment. The XV-15 also featured retractable tricycle landing gear, all gear with dual wheels -- the nose gear retracting back, the main gear retracting forward into sponsons. The landing gear was obtained from the Canadair CL-84, an earlier twin-turboprop tiltwing research aircraft. A switch on a main gear strut prevented the retraction of the landing and tilt of the rotors more than 30 degrees off vertical when the aircraft was in contact with the ground. Incidentally, for ground taxiing, the pilot would simply tilt the rotors one degree forward; and brake by tilting them one degree back.


   BELL XV-15:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   span, rotors turning    17.42 meters        57 feet 2 inches
   wing area               15.7 sq_meters      168.9 sq_feet   
   length                  12.83 meters        42 feet 1 inch
   height                  3.86 meters         12 feet 8 inches

   empty weight            4,574 kilograms     10,083 pounds
   MTO weight              6,000 kilograms     13,000 pounds

   max speed               555 KPH             345 MPH / 300 KT
   service ceiling         8,840 meters        29,500 feet
   range                   825 kilometers      515 MI / 445 NMI
   _____________________   _________________   _______________________

The XV-15 was sized to permit it to fit into the wind tunnel at Ames, which had a cross-section of 12 x 24 meters (39.4 x 78.7 feet). The two XV-15 prototypes were put through a wide-ranging set of trials by NASA and the Army, and had long subsequent lives as test and trials aircraft. They often flew demonstrations at airshows to successfully "wow the crowd". The XV-15s were flown by hundreds of pilots, in order to get as much feedback as possible; they were was generally found to be straightforward to fly.

XV-15 at NASM

The XV-15s were updated in service, being fitted with a Rockwell-Collins "glass cockpit". The first XV-15 prototype was lost in a crash on 20 August 1992; a bolt gave way, with one rotor going to full pitch, and the aircraft flipping over to impact on the ground. Both aircrew survived with little injury, with the cockpit being salvaged for use as a flight simulator. The second prototype continued in tests to 2003, when it was donated to the Smithsonian National Air & Space Museum. It is now on display at the Steven F. Udvar-Hazy Center at Dulles International Airport in Virginia.

BACK_TO_TOP

[2] MV-22 OSPREY: ORIGINS

* XV-15 trials going well, in 1982 the Pentagon initiated the "Joint Services Advanced Vertical Lift Aircraft (JVX)" program, to develop a production machine for use by America's armed services. The US armed services had not been particularly enthusiastic about VTOL transport aircraft up to 1980, having had no interest in the Ling-Temco-Vought XC-142 four-engine tiltwing transport of the 1960s. Conventional rotorcraft were perceived as being able to do the job.

However, the need for a next-generation vertical lift machine had been underscored by the disastrous failure of Operation EAGLE CLAW, an attempt to rescue American hostages being held in Tehran, Iran, on 24 April 1980. The mission was badly planned and ended in disaster, with a Sikorsky CH-53 helicopter colliding with a Lockheed C-130 transport at a desert rendezvous point; both machines were destroyed, with eight servicemen killed.

The failure of EAGLE CLAW suggested that, along with better planning, similar missions in the future would benefit from a vertical-lift capability with much greater range and speed. The JVX effort was originally run by the Army, being transferred to US Navy control early in 1983, with a contract issued in April 1983 for a 24-month preliminary design study.

The aircraft that emerged from the study in January 1985 was the "V-22 Osprey". A seven-year full-scale development (FSD) contract was awarded to a Bell-Boeing team in May 1986, which gave the type the company designation of "Model 901". The FSD contract specified delivery of six prototypes:

The first prototype performed its initial flight on 19 March 1989. It was followed by prototypes 2 through 5 -- the sixth being a ground-test airframe. Osprey prototype development was paralleled by experiments and trials performed with the XV-15, including tests of operations off the amphibious assault ship (helicopter carrier) USS WASP. The Osprey flight test program was completed, with all the surviving prototypes retired, the last flight of a prototype being on 27 March 1997. Two prototypes had been destroyed in accidents to that time:

In the interim, political support for the Osprey wavered, doubts growing about the wisdom of actually producing it, the 1992 crash having been a particular discouragement. The services were generally insistent, however, and a contract for four preproduction prototypes was accordingly issued in 1997.

Osprey 3rd prototype

The four preproduction Ospreys were significantly different from the initial prototypes, featuring a modified and lighter airframe structure, an improved engine / drive system, a redesigned rotor system, and pyrotechnic escape hatches. The US Marines were first in line to receive Ospreys, the USMC variant being designated "MV-22B", intended for the tactical transport role. Low rate initial production was begun in parallel with manufacture of the preproduction prototypes, and the first LRIP MV-22B for the Marines Corps flew on 30 April 1999. The aircraft was handed over to the Marines in May, and was joined by three more MV-22Bs for operational evaluation.

The operational evaluation included trials on the aircraft carrier USS ESSEX. One was loaned to the Air Force 58th Special Operations Wing, the USAF intending to acquire the type for the Air Force Special Operations Command (AFSOC) as the "CV-22B", with two preproduction Ospreys converted in 1999 as prototypes.

However, the Osprey's troubles were by no means over. On 8 April 2000 when the fourth LRIP MV-22B crashed at an airport in Arizona during a test exercise, with all 19 on board killed. After an investigation, the problem was attributed to pilot error, and the MV-22B was cleared for flight operations once more.

Unfortunately, on 11 December 2000 a second MV-22 crashed near New River, North Carolina, killing all four on board. The accident was traced to a hydraulic system problem, an issue that had plagued Osprey development. The accident dealt a serious blow to the program. The AFSOC seriously considered withdrawing from the program, which would in turn affect the already high unit cost of Marine MV-22s. The incoming Bush Administration was very uneasy about the program, given its long and expensive development history, and its future was very much in doubt.

The military proceeded carefully, however, resuming testing in 2002 and putting the aircraft through a year of exhausting trials. The test results were impressive enough to convince senior Pentagon acquisition official E.C. "Pete" Aldridge, who had been one of the skeptics, to recommend that the Osprey be taken off life support and put into full-rate production. Robert Wall of AVIATION WEEK reported the event in an article aptly titled: "More Phoenix Than Osprey". The test and evaluation program was finally completed in the summer of 2005, with the machine stamped "ready for production", though a few minor fixes in kit, none of them show-stoppers, were directed.

By that time, about 25 Ospreys had been built, all prototypes or test and evaluation machines. Approval for full-rate production was granted in the fall of 2005, with the first MV-22Bs fielded in 2007, to be quickly deployed to Iraq. That was 21 years after the issue of the original developmental contract. The CV-22B went into service with AFSOCOM in 2009. Fortunately, there were no more fatal accidents or losses of airframes to the end of that decade -- though some machines were badly damaged in incidents, and there were groundings.

BACK_TO_TOP

[3] OSPREY IN DETAIL

* The US Army is the only one of the four US military branches to not obtain the Osprey, having pulled out of the program in 1989. The Marines, as noted above, were the first to obtain the type, in the form of the MV-22B variant. The MV-22B was intended to replace the Marines' Boeing CH-46 Sea Knight helicopter, though the original plan to buy 552 Ospreys was scaled down to a buy of 360.

The MV-22B provides a baseline for the series. It clearly shows its roots in the XV-15, with a very similar configuration, if substantially scaled up. The MV-22B is built with an aluminum frame and composite skins; by weight, it is about three-fifths graphite-epoxy composite, a fifth metal, a tenth fiberglass, and a tenth "other". The MV-22B has retractable tricycle landing gear, with two wheels on each unit. The nose gear retracts backwards, the main gear tucks into sponsons on each side of the fuselage.

The wing has a slight forward sweep. The tailplane is straight, while the tailfins are swept back. Flight control surfaces are straightforward, including rudders, elevators, and twin "elevons" in each wing; of course, there are no flaps. There are de-icing boots in the leading edges of the wings and tailfins. Like the XV-15, there is an engine in each wingtip nacelle, which rotates to the vertical for vertical flight operations. Transition from hover to forward flight takes about 12 seconds.

Bell-Boeing MV-22B Osprey

The powerplants are Rolls-Royce T406-AD-400 (501-M80C) turboshafts, each with a takeoff rating of 4,585 kW (6,150 SHP), and a continuous rating of 4,395 kW (5,890 SHP). They have full-authority digital engine controls (FADEC), with analog backup, and an automatic fire extinguisher system. The engines are mounted on the wingtips -- like the XV-15, each driving a shaft running through the wing that connects the two engines, with a coupling scheme that allows the two engines to operate independently under normal circumstances, while allowing one engine to get the aircraft home if the other fails. The exhaust system for each nacelle incorporates a thermal emission suppression system to make the aircraft less vulnerable to heat-seeking missiles.


   BELL BOEING MV-22B OSPREY:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor diameter          11.58 meters        38 feet
   wingspan                15.52 meters        50 feet 11 inches
   width across rotors     25.40 meters        83 feet 4 inches
   stowed width            5.61 meters         18 feet 5 inches

   length                  17.47 meters        57 feet 4 inches
   stowed length           19.08 meters        62 feet 7 inches

   height over tailfins    5.38 meters         17 feet 7 inches
   height, nacelles up:    6.63 meters         21 feet 9 inches
   stowed height           5.51 meters         18 feet 1 inch

   empty weight            15,030 kilograms    33,140 pounds
   max loaded weight       23,980 kilograms    52,870 pounds

   maximum speed           509 KPH             316 MPH / 275 KT
   service ceiling         7,925 meters        26,000 feet
   range                   1,760 kilometers    1,090 MI / 950 NMI
   _____________________   _________________   _______________________

Each engine drives a three-blade propeller of composite construction -- the composite rotors were trialed on the XV-15 -- with the engines rotating in opposite directions. The propellers have a powered folding mechanism, and the entire wing can swivel 90 degrees, with the engines turned horizontal, to permit compact stowage. The stowage sequence takes about a minute and a half; when it's done, the Osprey has about the same footprint as the Sikorsky CH-53E. When sitting on the runway with the engine nacelles flat, the props are locked into the proper position, one blade directly upright, to ensure they clear the ground.

The MV-22B features flexible self-sealing fuel tanks from ILC Dover, with an 1,809-liter (478 US gallon) fuel tank in the front of each sponson; a long-range fuel tank with a capacity of 1,196 liters (316 US gallons) in the rear of the right sponson; and a 333-liter (88 US gallon) fuel tank outboard in each wing, for a total fuel load of 5,480 liters (1,448 US gallons). Up to three 1,628-liter (430 US gallon) ferry tanks can be installed in the cargo bay. There are refueling points on each wing and in the front of the right sponson. There is a retractable inflight refueling probe in the right side of the nose; apparently it is removeable, but it is unusual to see images of MV-22Bs that don't have the probe, so it seems it is normally fitted.

The Osprey has two independent hydraulic systems and a backup system. A Hamilton Standard Turbomach T-62T-46-2 auxiliary power unit (APU) turbine, in the rear of the wing center section, is used to drive two electrical generators and an air compressor; the APU also has an automatic fire extinguisher system. The aircraft has an onboard oxygen generator system (OBOGS) to eliminate the need to stock crew oxygen bottles, and a similar nitrogen generation system for fuel tank pressurization. The aircraft is not pressurized.

The MV-22B is crewed by a pilot, in the right seat, and a copilot and crew chief, all on crashworthy armored seats. Cockpit flight controls, all of "hands on throttle and stick (HOTAS)" configuration, are conventional for an aircraft, including stick, rudder pedals, and throttle, which operate as cyclic, yaw pedals, and collective in helicopter mode. The flight control system adroitly handles the transition between horizontal and vertical flight, without the flight crew worrying overmuch about the details.

The main cabin is big enough to carry 24 troops in full combat gear, sitting on inward-facing crashworthy folding seats, plus a gunner. In the medevac role, it can carry 12 litters, in four stations of three litters, and medical attendants. In the cargo transport role, the Osprey can carry 9,070 kilograms (20,000 pounds) of cargo, and includes a cargo winch and pulley system with a load capacity of 900 kilograms (2,000 pounds). A removeable cargo roller system can also be installed. There are dual cargo hooks on the belly for external sling loads; one hook by itself can handle up to 4,535 kilograms (10,000 pounds), the two together can handle 6,800 kilograms (15,000 pounds). Of course, flight with the nacelles turned horizontal is rule out when hauling sling loads.

There is a rear loading ramp; there is also a large cargo door at the front on the right side, with the top half opening up and inward and the lower half -- featuring built-in steps -- opening out and downward. There are emergency exit windows on the left side, and an escape hatch on top of the fuselage in back of the wing. There are provisions for a rescue hoist for use through the rear door; it was originally fitted to the side door. Three fast rope / rope ladders can be deployed through the rear door.

MV-22B Ospreys with wings folded

The Osprey has a triple-redundant digital fly-by-wire (FBW) flight control system, and dual MILSTD-1553B databuses. It has an autopilot and a "glass cockpit" with four multifunction displays -- two each for pilot and copilot -- plus a central status and alarm display and a small monochrome status display. Early aircraft had CRT displays, but they soon gave way to color LCD flat panels.

The pilot and copilot also have helmet-mounted displays (HMD), like those often used in modern military multirole helicopters; they're described as "head-up displays (HUD)", not HMDs, in some sources. It appears that that the HMDs were originally monochrome, but have been or are being updated to color. The cockpit is night vision goggle (NVG) compatible. A range of military radios, including satcom links, is fitted, along with an identification friend or foe (IFF) system. Other standard kit includes:

The Osprey is fitted with a electronics defensive measures suite, including:

The initial MV-22B "Block A" configuration was in a baseline configuration, lacking full kit, with "Block B" and "Block C" bringing the Osprey up to spec. Initial production plans envisioned the Osprey as being armed with a cannon in a nose turret, but it was deleted due to budget concerns. However, the idea didn't go away, and in 2000 an MV-22 was tested with a 12.7-millimeter (0.50-caliber) gun in a nose turret. The gun is a variant of the General Dynamics GAU-19/A three-barrel gatling gun, with a cyclic rate of fire of 1,200 rounds per minute.

The turret wasn't fielded. In practice, Marine Ospreys used a machine gun on a flexible mount, firing out the tail door -- originally the 7.62-millimeter (0.30-caliber) M240 MAG, but this giving way to the classic, more potent Browning M2 12.7-millimeter (0.50-caliber) machine gun. The idea of a turret didn't go away, with the the "Interim Defensive Weapon System (IDWS) turret from BAE Systems introduced late in the decade, being fitted with a 7.62-millimeter GAU-17 three-barrel gatling gun. It was fielded by the Marines but didn't prove satisfactory, it appears because it was too heavy, and was sometimes removed in the field.

BACK_TO_TOP

[4] CV-22B / CMV-22B / OSPREY IN SERVICE

* The US Air Force's CV-22B was intended for the long-range special missions role with the AFSOC, replacing the Sikorsky MH-53J Super Jolly helicopter in that organization. The Air Force originally planned to buy 80 Ospreys, but the order was eventually trimmed down to 50. The two CV-22B prototypes were rebuilt from Osprey production prototypes.

USAF CV-22B Osprey

The CV-22B's airframe is the same as that of the MV-22B, with the cockpit arrangement, navigation gear, and IFF being much alike. There are a number of significant differences, however, including:

Early deliveries of the CV-22B were in the "baseline" Block 0 configuration with a subset of operational avionics, but they were then updated through "Block 10" and "Block 20" to full planned avionics.

* Early on, the US Navy had intended to obtain 48 "HV-22B" Ospreys, for combat search and rescue (CSAR), special operations, and fleet logistics support. The deal fizzled out -- but in 2009, the Osprey was put forward in response to a requirement for replacement of the Navy's Grumman C-2 Greyhound carrier onboard delivery (COD) aircraft, for delivering material and personnel to carrier groups at sea.

As part of the evaluation, in 2012 an MV-22B landed and refueled on board the carrier USS NIMITZ, with cargo-handling trials conducted on board the USS HARRY S. TRUMAN the next year. In early 2015, the Navy and Marines signed a memorandum of understanding to obtain the Osprey for the COD mission, with an order formally confirmed later that year. The Osprey seemed well-suited to the role, having a carrying capacity like that of the Greyhound, but also capable of operating off other large ships with helipads, and carrying sling loads.

The Navy variant will be designated "CMV-22B". The CMV-22B will feature more fuel tankage to extend range from 1,590 kilometers (990 miles / 860 NMI) to 2,125 kilometers (1,320 miles / 1,150 NMI); it will also feature a beyond-line-of-sight communications system to stay in touch with a carrier group, and a public address system to stay in touch with passengers. The Navy has experimented with "rolling takeoffs and landings" with an MV-22B; straight vertical takeoffs and landings are not efficient for a heavily laden cargo transport. 44 CMV-22Bs will be obtained, with deliveries from 2020.

US Navy CMV-22B

Bell-Boeing has promoted the Osprey as a Navy platform for various missions, such as communications relay, electronic warfare, aerial refueling, search and rescue, and antisubmarine warfare. The US Army originally had a requirement for 231 V-22 transports, similar to the Marine MV-22. The Army withdrew the requirement, but remains interested in the type for medevac, special operations, and combat assault missions.

* The Osprey has distinguished itself in Iraq, Afghanistan, and other front lines in the "war on Islamic terror". Although there have been operational losses of Ospreys, concerns over reliability and vulnerability have been, admittedly after strenuous efforts, put to rest. The Osprey has several times the operational radius of the CH-46 that it replaces in Marine service, and can get a force onto the ground in about half the time. In the medevac role, the Osprey can get casualties to a field hospital much more rapidly than a helicopter. Major General Thomas Trask, an AFSOC commander, commented about the Osprey:

BEQIN QUOTE:

Pilots love this aircraft. It's comfortable, and very easy to get accustomed to. It has the flexibility you can't get with most helicopters. Bottom line, it's a joy to fly.

END QUOTE

Senior officers are inclined to put a positive spin on everything, but flight engineer TSGT Nathan McKinney praised the aircraft as highly:

BEQIN QUOTE:

We can take this aircraft into almost any landing zone. We can operate in difficult conditions in terms of weather and terrain, and insert and extract special operations teams far more effectively than any previous aircraft.

END QUOTE

From 2013, the Marine helicopter squadron HMX-1, which provides lift services for the US president and other senior government VIPs, obtained the first of what was supposed to be a total of a dozen or so MV-22Bs for the presidential flight. These MV-22Bs -- they don't seem to have a VIP designation -- only fly in support roles; they do not carry the president.

USMC MV-22B of HMX-1

The Osprey continues to be enhanced in service. Software updates have been ongoing, as well as hardware modifications to deal with problems. The Air Force is now moving towards replacement of the CV-22B's AN/APQ-186 radar with the Raytheon "AN/APQ-187 Silent Knight Radar" -- which will be a "low probability of intercept" radar, hard for the Black Hats to pick up. The USAF is also obtaining armor for the CV-22B, in the form of the "Advanced Ballistic Stopping System (ABSS)", which will be a relatively lightweight set of armor elements to protect crew and critical aircraft systems.

In 2014, Bell-Boeing conducted armed trials of the Osprey on their own funding, the aircraft being fitted with a targeting turret and a stores pylon on the right side of the nose. Weapons fired included 70-millimeter unguided rockets, laser-guided APKWS 70-millimeter rockets, and Griffin small laser-guided missiles. There has also been talk of an engine replacement.

In October 2016, Bell-Boeing awarded a contract to Cobham Mission Systems of the UK to develop a palletized aerial refueling system that will allow the Osprey to act as an inflight refueling tanker. The "V-22 Aerial Refueling System (VARS)" will use a modified version of Cobham's existing FR300 Hose Drum Unit (HDU). The contract followed investigatory work going back to 2013, with operational capability expected in late 2019. The FR300 HDU is a well-established system; the first version of the FR300 was designed in the 1960s, with the Lockheed Martin C-130 Hercules being the best-known platform that uses the FR300. Proof-of-concept tanker trials with the Osprey were performed with an existing FR300 haywired into the Osprey.

MV-22B tanks up Hornet

The production Osprey VARS will be a "roll-on / roll-off" system, easily installed and removed as needs require. It will require some modifications to the MV-22B for use -- including changes to allow the refueling hose to be deployed regardless of rear door position, and electrical system changes to allow the VARS to be used in both rotary- and fixed-wing flight modes. The changes are not seen as extensive or, by aerospace standards, expensive.

Bell-Boeing is also considering other special-mission configurations of the Osprey -- such as surveillance, electronic warfare, or command post -- but there's been no action on such yet.

BACK_TO_TOP

[5] AW609 TILTROTOR

* In 1996, Bell and Boeing came to an agreement to work on civil tiltrotor, as a complement to the development of the V-22, with plans for a first flight in 1999. That didn't happen. In 1998, Boeing withdrew from the partnership; Bell then hooked up with Augusta Aerospace of Italy to continue the effort, coming up with a design for a "Bell-Augusta 609 (BA609) civil tiltrotor aircraft, with a general configuration similar to that of the Osprey but in the size range and style of a business aircraft.

Augusta merged with Westland of the UK in 2000 to become "AugustaWestland"; the partnership with Bell on the BA609 continued. Initial flight of the first BA609 prototype was in March 2003, with the first full vertical takeoff / forward flight test on 22 July 2005. A second prototype followed a year later.

The program was well lagging the original estimate of a first flight in 1999, and was to encounter further delays. Bell had been cooling on the exercise, partly because of distractions with getting the Osprey into proper service, and frictions with AgustaWestland grew. AgustaWestland negotiated with Bell to obtain complete control over the program in 2011, with the tiltrotor redesignated "AW609". Bell retained a minority involvement in the program as a subcontractor, with the deal stipulating that AgustaWestland not sell an armed military version of the machine. AgustaWestland moved forward on the construction of two more prototypes, with the third flying in 2015, and the fourth flying in 2017 -- the fourth being near to production standard.

The program suffered a major setback in 2015, when the second prototype broke up in mid-air, killing the two test pilots, Herb Moran and Pietro Venanzi. However, the program continued, with expectations that the AW609 will obtain civil certification in 2018. This is challenging, because the certification has to meet specs for both fixed-wing aircraft and rotorcraft.

* Leonardo Helicopters -- which superseded AgustaWestland in 2016 -- regards the AW609 as a high-priority project, seeing it as giving a decade step ahead of competitors, nobody else having been willing to endure the level of pain the company had endured to come up with a machine with such capabilities. Leonardo officials actually don't expect sales to skyrocket immediately, since the new technology will have to carve out a market for itself. However, the fact that the AW609 can use existing heliports is seen as a plus.

Leonardo AW609

The general configuration of the aircraft has changed little since the first mock-ups made their trade show debuts in the early 2000s. It is made primarily of composites, with a circular-section pressurized fuselage, with a high-set wing featuring a slight forward sweep. It has a tee tail, but no rudder, yaw control being performed by differential thrust from the props. Production machines feature aerodynamic refinements that cut drag by 10%.

The AW609 is powered by twin Pratt & Whitney Canada PT6C-67A turboshaft engines with 1,450 kW (1,940 HP) each and FADEC. The engines are mounted on the wingtips, each driving three-bladed rotors with a diameter of 7.9 meters (26 feet). The engine modules can tilt from horizontal to 95 degrees upright, just beyond vertical; as with the Osprey, the engines are cross-coupled, allowing one engine to keep the aircraft aloft if the other fails.

The AW609 has a sophisticated FBW flight control system designed by BAE Systems. The prototypes are fitted with Rockwell Collins Pro Line 21 avionics suites, but production aircraft will feature Pro Line Fusion system -- featuring 36-centimeter (14-inch) touchscreen displays, plus an integrated flight management system with satellite-based navigation, synthetic and enhanced vision, as well as head-up display interfaces. Weather radar is optional.

The AW609 is designed to be flown by a single pilot; the control layout is like that of a helicopter, with cyclic and collective sticks. The controls work effectively the same in both vertical and horizontal flight. The engine module tilt is controlled by a thumbwheel on the collective; they tilt at 3 degrees per second normally, 8 degrees per second in an emergency.


   LEONARDO HELICOPTERS AW609:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   rotor diameter          7.9 meters          25 feet 11 inches
   wingspan                10 meters           32 feet 10 inches
   width across rotors     18.3 meters         60 feet
   length                  13.4 meters         44 feet
   height over tailfin     4.6 meters          15 feet 1 inches

   empty weight            4,765 kilograms     10,505 pounds
   max takeoff weight      7,620 kilograms     16,800 pounds

   maximum speed           509 KPH             316 MPH / 275 KT
   service ceiling         7,620 meters        25,000 feet
   range                   1,390 kilometers    865 MI / 750 NMI
   _____________________   _________________   _______________________

The AW609 can be fitted with from 6 to 9 passenger seats, though combi-cargo, medevac, and SAR configurations are possible as well. Leonardo has investigated a large double door that can be opened in flight, with a hoist for SAR missions. Potential markets include business aviation services, search and rescue organizations, emergency medical evacuation services, and offshore oil drillers.

Leonardo AW609

Although the AW609 is more expensive than a helicopter of comparable size and capacity, it is much faster and has much greater range, while still being able to operate off of existing helipads -- it was sized to do so. In response to customer input, an auxiliary wing fuel tank system is in the works, which would extend maximum range to 2,000 kilometers (1,240 miles / 1,100 NMI), or fly six passengers over a range of 1,480 kilometers (920 miles / 800 NMI) in a little over three hours.

As a follow-up to the AW609, Leonardo Helicopters is planning to fly a "next-generation civil tiltrotor (NGCTR)" in 2021 -- along the lines of a scaled-up AW609, with 20 seats. The NGCTR is still in the concept phase, the company being preoccupied with getting the AW609 on the market.

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[6] BELL V-280 VALOR

* Bell has worked on other tiltrotor designs, such as the "Eagle Eye" drone, flying a subscale demonstrator in 1993. Although the US Coast Guard awarded Bell a contract for the Eagle Eye in 1998, it was cancelled, and the Eagle Eye disappeared.

Bell is moving forward on a crewed tiltrotor, smaller than the Osprey. In 2013, the company released drawings of a "V-280 Valor" machine being considered by the US Army's "Future Vertical Lift (FVL)" competition, with a full-scale mockup unveiled later in the year, and a demonstrator to fly in 2017. Lockheed Martin has signed on to the V-280 to provide systems expertise.

Bell V-280 Valor

The V-280 concept features a composite airframe, a vee tail, retractable taildragger landing gear, and twin engines -- though the engines don't tilt, they drive the rotors through a pivoting transmission system. The demonstrator will be powered by GE T64 turboshafts, coupled via a driveshaft as with the Osprey. The production engine hasn't been selected yet.

The V-280 will have an NVG-compatible glass cockpit and a triple-redundant FBW system. It will be able to carry a crew of 4 and 14 troops, with access through wide back-sliding side doors on each side. There is a forward-hinged door on each side of the cockpit. The Osprey had a tail ramp for troop access; the side doors on the V-280 were the primary reason the V-280 uses tilting rotors instead of engines, since tilting engines would have obstructed the troops on exiting the aircraft. Bell also claims the tilting rotor system is simpler and more reliable than tilting engines.

A machine gun can be mounted in a window on each side; presumably a hoist will be available as well. It seems likely that a countermeasures system and imaging turret will be optional, or possibly standard kit. The V-280 will be able to haul a 155-millimeter howitzer as a sling load. It will be capable of inflight refueling. Preliminary performance specs for the V-280 include:

Projected maximum takeoff weight is around 13,600 kilograms (30,000 pounds). The Army plans to select one or more FVL design submissions for development of a demonstrator. Bell is considering an attack derivative down the road, concepts having been presented with an undernose cannon turret, and missile racks under or alongside the fuselage.

* Along with the V-280, Bell Helicopter is also pushing a new naval tiltrotor drone, the "V-247 Vigilant", in anticipation of a US Marine Corps requirement for a ship-based armed drone. According to Bell, the V-247 would carry sophisticated sensor, electronic warfare, or communications-control systems -- not to mention weapons -- to serve as a ship-based companion aircraft to the Osprey and the Lockheed Martin F-35B VTOL strike fighter.

Bell Vigilant drone

Although the USMC hasn't committed to any such requirement yet, preliminary roadmap documents suggest a technology demonstration in 2018 and initial operational capability in 2026. Bell has not yet selected a power plant for Vigilant, but wants one in the 3,750 kW to 4,475 kW (5,000:6000 SHP) range. The V-247 will have an "open architecture" to permit mission customization, with three internal bays that could carry sensors, fuel, sonar buoys, radar, a homing torpedo, or Hellfire / JAGM anti-armor missiles.

At the upper end of the size scale, Bell-Boeing has proposed a next-generation four-propeller tiltrotor, simply called the "Quad Tiltrotor", that would be comparable to a Lockheed C-130 Hercules. It would be able to carry loads of up to 13.6 to 18.2 tonnes (30,000 to 40,000 pounds) over a range of 3,200 kilometers (2,000 miles) at a cruise speed of 520 KPH (320 MPH / 280 knots).

Bell-Boeing Quad Tiltrotor

The military didn't bite on the concept for a few years, but in 2005 Bell Helicopter Textron was awarded an investigation contract for the Quad Tiltrotor as part of the US military's "Joint Heavy Lift (JHL)" program.. There was skepticism over the practicality of the Quad Tiltrotor, with some Air Force officials saying the machine would not be able to operate in frontline combat conditions or behind enemy lines, and would have a tremendous propwash. The propwash of a V-22 is bad enough, but the Quad Tiltrotor would raise a hurricane of dust and debris when landing on an unprepared surface. So far, the Quad Tiltrotor remains a paper project.

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[7] COMMENTS, SOURCES, & REVISION HISTORY

* I finally got to see Ospreys in service at an airshow at Miramar Marine Corps Air Station -- near San Diego, California -- in 2012. They were definitely sci-fi in appearance, giving me a sense that I was indeed living in the 21st century. Of course, the irony is that the Osprey has been flying since the 1980s, but didn't get into service until after the turn of the century.

MV-22B at Miramar

* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* Sources include:

* Revision history:

   v1.0.0 / 01 jul 17
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