Civilian Tilt Rotor Baggage

The Bell/Agusta BA609 civil tiltrotor has been in the works for a over 10 years, as reported by an August, 2007 article in Aviation International News (AIN) called "As time passes, operators question BA609 appeal". That article goes on to relate the diminishing interest by potential buyers of the craft. A more recent article in 2008 by Aero News Net, titled "BA609 Tiltrotor Makes Its First Appearance At Show", further confirms this by saying "but officials at the American helicopter manufacturer [Bell] have recently signalled the market they once saw for the aircraft has declined significantly in today's economic conditions."

From our perspective, an airplane that can take off and land vertically like a helicopter and also fly as fast and with the same ease as a fixed wing aircraft is the ideal. So, why are people losing interest in the BA609? The primary reason is cost: almost $20,000,000 for a plane that carries eight or nine passengers. With that kind of money, one could buy several helicopters or about five very light jets (VLJs). Other issues quoted by the AIN article are: that the craft is "too big for use on standard helipads and yet too small for comfortable executive charter." Given the already existing helipads in major cities, oil rigs, company campuses, hospitals and private homes, an vertical flight airplane must be able to use them, or it will require an set of such landing pads of its own.

We've already talked before about the inherent weaknesses of a tilt rotor design. That technology is not the most efficient and most reliable way to add vertical flight capability to an airplane. The lack of efficiency and the potential safety problems is what has swollen the cost of the BA609 to far more than any of the competing aviation modes: helicopter or fixed wing plane. We think it just is not possible to build a tilt rotor vertical take off and landing (VTOL) craft without spending money on redundant computer systems and other complexities, thereby inflating the cost considerably.

We do offer an alternative: our Arc Wing VTOL airplane. By using deflected slipstream technology, which we think is the most efficient (the most elegant, really) approach to vertical flight, our craft will cost about the same as a VLJ and will be far more inherently safe than a tilt rotor craft (or even helicopters) due to the simplicity and aerodynamic qualities of the design. We invited all those interested in the best possible VTOL airplane to look into our proposal. The Arc Wing VTOL can be scaled from four passengers to far more. The smaller ones will easily work with existing helipads. The larger craft will have to be accommodated as per their size. In all cases, the cost will be similar to turbine fixed wing planes of corresponding size.

Tilt Rotor Turmoil

The Dreadnaught blog reported in March a story about the faster than expected wearing out in Iraq of the engines for V-22 Osprey tilt rotor aircraft. This issue is just the latest in a long series of problems this plane has experienced.

An article in the the New York Times on April 14 of 2007, summarized the history of the development of the V-22. That story pointed out the high development cost, $20 billion dollars, high craft cost, $80 million each, and the fatal accidents that have occurred with this plane. The article relates further criticisms, including the lack of any ability to land safely should power fail, or the craft run out of fuel. It also states that the vortex ring state, where the propellers get caught in their own turbulence during landing is its chief operational risk.

From my perspective these criticisms should be expected because the V-22 Osprey, like any other tilt rotor craft, has an inherently flawed design. As I see it, the V-22 is far too complex because it uses the wrong technology for vertical flight and as a result many workarounds and add ons are needed to get it to operate at all. It's flaws include:

1. The laterally disposed rotors present an asymmetrical lift situation, and any unequal lift from one or the other propellers can cause severe roll moments. It is essential to have centerline thrust to avoid this fatal occurrence.
2. In total power failure or “running out of gas“, the V-22 is a free falling body below 1600 feet altitude. It cannot use its wing for gliding flight to non disastrous landing, because the large propellers will impact the ground on landing and crash the craft. Again, neither can it auto rotate its propellers like a helicopter.
3. The complexity of V-22 cross shafting, nacelle tilt bearings, two transmissions, and servos, are inherent failure points, and potentially fatal failure elements.
4. The V-22 is all computer programmed and controlled, additional elements to fail. The pilots need special training that exceed mere rotor craft training.
5. In VTOL (vertical take off and landing) mode, the download of the propeller slipstream on the wing costs 10% of the trust for lift, plus there is additional upward fountains of air between rotors causing more loss of lift It has a less than optimal use of the propeller lift.
6. With the high cost and maintenance of the V-22, only the military can afford it.
   

At Aeromobile Inc., we have designed and experimented with an entirely different approach to vertical take off and landing. Our Arc Wing VTOL airplane uses deflected slipstream for vertical maneuvers, and is a fixed wing airplane for horizontal flight. It does not have the inherent design problems I listed for the V-22 Osprey tilt rotor craft and will make a far more efficient, safe and inexpensive VTOL aircraft.