What's New With The Civil Tiltrotor?

[21stCen]

What is often missed on this concept is the awesome inefficiency of the tilt rotor type: ... It has no more range, dont be fooled by the fact that TRs have enormous fuel tanks as standard, where helicopters has smaller tanks. If the helicopters used even half the extra payload they have as takeoff fuel, they have more range than a tilt rotor.

Not true, in fact just the opposite. For example, our AW139s carry 2,767 lbs standard fuel that provides a range of 437nm, while the 609 carries 2,480 lbs standard that gives it a range of 720 nm. When in the airplane mode the tiltrotor is far more efficient. The main reason for this is because the thrust developed by the main rotor of a helicopter has to provide both vertical lift and forward thrust. In the airplane mode a tiltrotor gets its lift from the wing and can use 100% of the proprotor thrust in the horizontal plane. However, in a hover the helicopter is far more efficient than a tiltrotor. The smaller blades of the tiltotor's proprotor cause it to have a much higher disk loading and are far less efficient than a larger helicopter rotor, plus the downwash on the large surface area of the wing creates a downward force on the top of the wing in addition to adding other aerodynamic inefficiencies.

the 16,000 lb AW609 needs more power installed than the 21,000 lb Black Hawk, it weighs more empty weight, and it has a gross weight about 5000 lbs less, all lost payload.

The max t.o. weight of the AW609 is now 18,000 lbs. The reason the manufacturer added such a large amount of power is because of the hovering inefficiencies mentioned above plus the added weight of the unprecedented number of triple redundant systems onboard the aircraft. The power to weight comparison is a good discussion point for engineers to debate and evaluate technical efficiencies. From a customer/end user standpoint that is irrelevant. Our customers will decide on an aircraft based on the number of pax it can carry and the performance offered (primarily speed and range). On the VVIP side our customers might compare an S-76D vs. AW139 vs. 609 for their choice of aircraft. In this category of customers cost is less of an issue particularly in our region. The same is sometimes true with military customers within reasonable limits. And as mentioned previously, if the 609 is the only aircraft that can do the job and the price is not obscenely high, the customer will choose it.

Also don't be fooled by the speed hype, the best range speed of the 609 is nowhere near 275 knots

Please reread the post you are referring to. It says very specifically that the "max cruise speed" is 275 kts. Best range and max cruise speeds are very different numbers. Max cruise speed is the speed that you are capable of cruising at if you need to get there in a hurry, but because of higher drag and added fuel burn it will certainly not provide best range! Several years ago the 609 demonstrated 334 kts inflight and at that time it was estimated that the redline would be set at 292 kts. Those numbers are probably outdated as they have since increased the amount of power available from the PT6C-67A engines.

...but its reality is probably well inside its current hype. It niche will be smaller by far than the one folks have mapped out for it, I believe.

Not true, in fact just the opposite IMHO. We no longer have to listen to hype from the marketeers. The 609 as flown nearly 1200 hours and the data hard points are readily available to customers. The CEO of Bristow just announced that the 609 will become a big part of their fleet in the future and they have committed to join in the operations development of the aircraft (see post #98). This decision was after the operations and engineering departments at Bristow studied the data from the 609 test flights to date and applied the cost and benefits in a business case study primarily for offshore ops. As a result the CEO remarked, “We see tremendous opportunities for this aircraft for our clients who are flying to more remote and hostile environments... With its vertical lift and landing capabilities combined with increased speed, extended range and airline-style amenities, Bristow will be able to provide more value to clients by offering complete logistics solutions with one aircraft type that will take them faster and farther offshore.” If you know something that Mr. Baliff is not aware of, perhaps you should give him a call...