Extreme Machine- page 3 | Flight Today | Air & Space Magazine
Current Issue
September 2014 magazine cover

Save 47% off the cover price!

Extreme Machine

The U.S. Marine Corps' sword gets a brand-new edge.

Air & Space Magazine | Subscribe

(Continued from page 2)

A ramp folds down at the rear to accommodate two utility vehicles, and the craft has two belly hooks so that it can carry cargo on a sling beneath it. Once aboard a carrier, the Osprey takes only 90 seconds to fold into a package slightly longer than its 57-foot, four-inch fuselage. Although the equipment for the stowing cycle exacts a penalty in weight and cost, self-stowage means that more aircraft can be carried, and all can be launched and recovered within minutes. The Osprey can be refueled in flight through a probe, and it carries a rescue hoist plus a "fast rope"the line commandos slide down when they arrive in their special way. With inflight refueling, the V-22's ultimate range depends only on having enough tankers and on how long the crew can stay awake. Fuel tanks are located in the sponsons and the wings (plus three that can be installed in the cabin for transoceanic trips). Should gearbox lubricant be lost, the craft can fly another 30 minutes.

The Osprey has three independent flight control systems, any one of which can fly the aircraft. All three use fly-by-wire technology that employs electronic signals rather than cables and pulleys to operate the controls. There are two mission computers and three inertial navigation systems to help you figure out where you are, and the displays in the glass cockpit can be routed to any of the video tubes in the event one of them fails. All information for a mission can be loaded in seconds from a cartridge that plugs into a computer system. In addition to the various alerts and warning lights, an audio annunciator tells you what kind of trouble you're in. (The disarmingly dulcet voice belongs to Barbara Smith, deputy to Colonel Nolan Schmidt, the Marines' program director for the V-22.)

There are four electrical generators, two located with the engines and two more in the upper fuselage, and a battery good for 20 minutes of flying if all else fails. An onboard generator extracts nitrogen gas out of the air and floods the fuel tanks, displacing oxygen and reducing the risk of fire. The outer skin has a fine copper mesh embedded in it to form a conductive path in the event of a lightning strike. The aircraft has three completely independent hydraulic systems, which operate at 5,000 pounds per square inch; out in the fleet, only the F/A-18 has such high hydraulic pressures. But the V-22's hydraulic lines are made of titanium, which is thinner and lighter and thus saves weight. "We had to invent the connectors for that system," Buyers says. The engineers also had to rewrite all the criteria for replacing a line that has been scratched or nicked.

A little less than half the airplane is manufactured of composite materials, which, while incredibly light, are also corrosion-resistant and strong. Should a bullet penetrate it, the composite fibers ensure that the hole won't expand or start to crack. Systems and controls are distributed and separated throughout the aircraft so that one bullet can't take out all of anything. When things fail, they fail "softly"only half a control surface at a time, for example.

If all of the systems, capabilities, protection, and toughness seem hard to believe, consider this: The V-22 is an aircraft of the '90s, and the aerospace industry never stands still. Things have changed. At the old Vertol (now part of Boeing) plant in Philadelphia, where workers are building the first parts, there's little of the old din of metalworking; all those industrial sounds have been replaced by the softer whirring of electric motors, fans, and the actuators in robots. The workers here behave as if they're working on the hottest project in aerospace. There's the razor-sharp young engineer, Ken Eland, who is revolutionizing the way the Osprey is built. The company saved $21 million by eliminating the traditional mockup and so far has cut the parts count by 36 percent, eliminating 18,000 fasteners by such simple steps as making the skins and their stiffeners as a single integrated part.

And there's Valorie Bring, a former IBM employee who says she sort of fell into her current job of designing displays and switches and controls that the pilots can understand and use easily. She uses the word "customer" a lot. She's in charge of the Osprey's cockpit environment and co-author of a paper on how the entire electronic system works on a hypothetical mission. But her biggest job is to listen. "Ask 10 pilots and you'll get nine opinions, and then that one guy will change his mind," she says. "The trick is to find the common thread in their words."

You find the same culture at Pax River. In the hangars where the V-22s are tended between flights, the test aircraft are helpless giants with their innards exposed and people crawling all over them. They remind you of patients in an intensive care ward, surrounded by scaffolding, lines, and service carts. The military officers in khakis and olive flightsuits and black shoes mix with civilians wearing Nikes and sporting the occasional tattoo or piercing, while out in the parking lot there are motorcycles scattered among the pickups and sports cars and imports. You wondered where the new generation was headed? They're hard at work on the V-22.

While the basic principle of tilting the props to create an airplane that can hover seems obvious, it is not easy to design and build a craft that can do it successfully, as testified by the long line of research aircraft that have led up to the Osprey. The V-22 succeeds in large part because of small, lightweight, powerful computers that can store complex control laws to guarantee success in the hands of an average pilot. When the first Marine service pilots begin flying the V-22, the airplane's flight control system won't let them get into trouble. Bell Boeing senior test pilot Bill Leonard puts it this way: "There are three computers and a pilot, and all of us get one vote. There have been many times when I have been outvoted."

The engine nacelles are controlled by a small knurled thumbswitch on the thrust control lever in the pilot's left hand. The nacelles can rotate from zero degreesstraight ahead in the propeller positionto plus 95 degreesslightly aft of straight up so that the lift force pulls toward the tail of the airplane to slow down and even back up. A huge screw drive rotates the nacelles at up to eight degrees per second, and conversion can take as little as 12 seconds. Leonard says, "From about 60 degrees nacelle to 95, it flies like a helicopter. From 30 degrees down to zero, it's an airplane." (In the transition, it's a little of both.) In helicopter mode, the prop-rotors have full cyclic and collective controls using the stick and thrust control lever (TCL), respectively. "You use your left hand [TCL] to control altitudethe verticaland your right hand [stick] to control your position in pitch and roll," Leonard says. The foot pedals control the yaw axis, which works in helicopter mode by diverging the lift axes of both rotors, just as it works on a tandem-rotor helicopter like the CH-46 (see "Yaw Control," p. 31).

At between 40 and 80 knots forward speed (the Osprey uses knots, which equal 1.15 statute miles per hour, for airspeed measurement), the wing begins to produce lift and the airplane control surfacesailerons (in this case, combined flaps and ailerons called "flaperons"), elevator, and ruddersbegin to have an effect. At the same time, the helicopter controls begin to phase out of the prop-rotors, and at about 100 to 120 knots, they become propellers. The airplane's genius is in phasing from one mode to the other based upon flight conditions, mixing the controls so that both are active in the region between about 40 and 120 knots. The pilot can rotate the nacelle forward with the thumbswitch or, while accelerating, let the computer do it. During deceleration the pilot must rotate the nacelles to the vertical with the thumbswitch; otherwise, with the power pulled back, the V-22 will slow and eventually stall.

About George C. Larson

George C. Larson served as editor of Air & Space from 1985 to 2005. He is currently an inactive pilot, but holds a commercial pilot's license, with instrument and multi-engine ratings. He is between airplanes at this time, but has owned or operated a Grumman American AA-5B Tiger and a Mooney 201. He has been writing about aviation since 1972, when he joined the staff of Flying Magazine.

Read more from this author

Comment on this Story

comments powered by Disqus