Some comments on the Tilt Rotor's advantages, which are never put into true perspective by advocates (How many times have you read, "Tilt rotors carry twice the payload, twice as fast twice as far as helicopters"?) Here is some unvarnished info:
The typical tilt rotor/helicopter comparison made in the sales literature always compares the tilt rotor to the next smaller sized helicopter, a neat trick if the public laps it up. If one selects helicopters with the same empty weight and the same installed power (which is typically the next larger sized helicopter, because tilt rotors are so inefficient) then one finds:
1) Range - Its a draw - Tilt rotors have no range advantage over an equivilent helicopter. This is a fact born of the low payload of the tilt rotor, which never lets its better cruise efficiency catch up with a helicopter.
2) Speed - Yep, tilt rotors are lots faster - The max speed of the tilt rotor is 1.8 times faster, a great advantage. The best range cruise speed is somewhat less, about 1.6 times faster. For typical trips in the 200 to 300 Nm range, this yields trip times that are about 1 hour faster (1 hour by tilt rotor vs 2 hours by helicopter). If the city heliport requires Cat A/JAR Ops Class I, there might be more difficulty for the tilt rotor as its fuel and/or payload drops considerably as the heliport shrinks below 1000 feet length.
2) Payload - Nope, tilt rotors lose bigtime - Tilt rotors carry half the payload of the equivilent helicopter to any range they can go. This is because the tilt rotor weighs so much more (the great big engines and the wing's greater vertical drag in a hover).
3) Cat A performance - Tilt rotors are generally hurting - Tilt rotors have great difficulty meeting the Cat A requirements (or JAR Ops) because their rotors need very much more power.
4) Initial cost - Jury is out, lets see what they charge for 609, V-22 is no bargain - Tilt rotors seem to cost about twice what the equivilent helicopter costs because of all the transmissions, rotor controls airplane controls and tilt mechanism. Figures are hard to get on this, V-22 seems to cost between 55 Million and 80 million. Initial 609 numbers were 8.5 million, but these were withdrawn about 2 years ago. Any more current ones, guys?
5) Maintenance ease - Tilt rotor loses bigtime - Tilt rotors are extremely complex, much more so than a helicopter. They have a full set of tandem rotor mechanisms, a full set of airplane mechanisms and a tilt mechanism. They are as if a Chinook and an F-14 had a baby. For example, the typical tilt rotor has between 26 and 32 flight critical control actuators on it, while the typical helicopter has 8. A typical tilt rotor can have 3 dual MR servos per rotor, 2 dual tilt servos, 2 dual aileron, stabilator and rudder servos, 2 dual flap servos makes 32! This situation is made much worse by the awful weight reduction tradeoffs made to keep the payload usable. Example - the hydraulic lines on the V-22 that handle its 5,000 psi are thinner (0.022" wall thickness) than any other manufacturer allows for pressure lines (0.028" wall thickness is standard for 3,000 to 4,000 psi)! The line that chafed and failed on V-22 was 0.022" thick, there are no plans to thicken them.
Some facts and figures:
While the 609 is often compared with the S-76 family (since it carries less payload than an S-76) , it actually has more installed power than the Black Hawk, and has virtually the same empty weight, too. When reviewing the below, remember the Black Hawk numbers are for the 3000th aircraft built, in full gear; the 609 numbers are for an as-yet unproven aircraft and likely to change very much for the worse.
Bell 609:
Max gross weight 16,800 lbs, empty weight 11,300 lbs, max useful load 5,500 lbs
Cabin Volume 237 cubic feet
Max Range 750 NM no reserve
Max cruise speed 275 knots
HOGE at MGW un-reported
http://www.bellagusta.com/html/theAi...cs.html#6notes PT-6C-67A, 1940 HP takeoff X 2= 3880 HP total
http://www.pwc.ca/en/3_0/3_0_3/3_0_3_2_2.asp
UH-60L/S-70A:
Max Gross weight 22,000 lbs, empty weight 11,700 lbs, max useful load = 10,300 lbs
Cabin Volume 372 Cubic feet
Max range 1140 Nm with 10% reserve, 10 kt headwind
Maxumim cruise speed 149 knots
HOGE at 22000 lbs 3900 ft
http://www.sikorsky.com/details/1,,C...ETI561,00.html T700-701C, 1890 HP takeoff X 2= 3780 HP total
http://www.geae.com/engines/military...t700-701c.html