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Copy of Letter from the President: of Moller International February 2002

 Dear Skycar Enthusiasts:

I know you are all anxious for news about the Skycarâ flight tests, but I think it would be worthwhile to also provide you with a detailed review of the past six month's effort which will better let you understand where we are today.

Six months ago we had completed the software and the hardware for the control and stability systems. We also had all engines up and running. We are temporarily using single rotor air cooled models of our engine rather than the eventual two rotor models which generate twice the power. When we began the engine installation more than two years ago we did not have our twin rotor liquid cooled engines fully developed. In our optimism we felt that we would begin tests before they would be available, and therefore elected to go with higher powered versions of the single rotor engines used in the M200X (80 HP vs. 50 HP). In hindsight, of course we could have waited since the stability and control system took more than an extra year to develop. In any case, that decision influenced a number of other components, etc. that caused their own delays. For example:
  1. We added a temperature controlled water spray system to the fins to help cool this air cooled engine at this high power.
  2. We had to get the nacelles to be as efficient as possible in generating thrust because of this limited power. This development took well over one year.
  3. Even with water spray the engines operated at fairly high temperatures when we were testing in 100°F weather this past summer. As a result we changed to alcohol as a fuel. This cooled the engines down and is also much safer in case of fire; but it meant changing fuel pumps, injectors, etc., including having to fabricate our own spark plugs.
  4. Alcohol has its own unique lubrication requirements which took some time to address.
Following initial hovering tests we felt we needed to improve the available control power in pitch. With four passengers the center of gravity coincides with the center of lift from the nacelles in hover. However, we are now either hovering remotely or with only the pilot which while making the M400 lighter and able to be lifted with single rotor engines also places the C.G. further forward. This means the engines in the front nacelles were operating at higher power than the rear (near their limit). By moving the front nacelles forward we improved the lift balance of the front and rear nacelles. This change improved pitch stability and took three weeks primarily due to having to lengthen more than 300 electrical wires.

One final modification is being undertaken to provide even better balance prior to providing a press release. A patent pending improvement is being applied to the present M400. This change will further improve pitch stability in addition to a number of other benefits.

Much of the time this past year has been taken up in debugging and improving the software and tuning the propulsion system as problems were discovered during various tests. The most difficult problem was to formulate the algorithms that determine how one variable such as the amount of angular velocity about an axis interacts with the throttles controlling the engines and the engine response time, which itself varies with RPM, etc. Most of these relationships are non-linear and therefore very complex in the results from their simple interactions. In early December we determined the right formulation and gain values for the CORPM (Close On RPM) algorithm. There were many other issues that were addressed during this period that are part of the ultimate success.

While the M400 has been undergoing testing we have continued our wind tunnel and engine testing in preparation for entering the production phase of the Skycarâ development. As a result we have patents pending on new elements of the Skycarâ that appear as important as those we already have in place. The following goals were achieved as a result of this recent development:
  1. The design of the production Skycarâ width was reduced from 10 ft. (wing folded) to 8.5 ft. (wing folded), which allows it to be legal width on the highway without a variance.
  2. The aerodynamic efficiency in forward flight was improved sufficiently to project fuel efficiency of 28 miles per gallon versus 18 miles per gallon of the present design.
  3. We found a way to temporarily boost power by more than 50% without increasing the engine heat being generated. As a result, the total installed horsepower can be reduced or the payload significantly increased.
  4. A unique design of the nacelle/airframe interface allowed the nacelle C.G. to move and thereby coincide with the thrust lift center in hover and then with the aerodynamic lift center in forward flight. This design also improved thrust by over 10% and therefore net payload by over 30%.
  5. Finally, we were very pleased when we weighed the M400 Skycarâ and found the final empty weight was 1,435 lbs. This was better than we expected considering that we used a hand lay-up airframe with numerous modifications using fiberglass. Achieving 1,435 lbs. empty weight in an aircraft with 640 HP (not boosted) is clearly a first. We will remove about 250 lbs. from the airframe when using vacuum bagged carbon fiber in the final production airframe. We will also add about 250 lbs. by going to twin rotor engines. This means that together with patent pending improvements we could significantly exceed our original design goal of a useful payload of 950 lbs. in a 2,400 lb. aircraft.

The upcoming extended demonstration of the M400's hover characteristics will provide very convincing evidence of the merits of our design. I hope that you can all appreciate the level of effort that it took to reach this point, and will continue to support us as we reach for and achieve new milestones on the way to bringing this capability into production.

Sincerely,

Paul S. Moller
President