Wichita Falls, Texas: Monday, April 5, 1999.

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CARTERCOPTER RETURNS TO OLNEY, TEXAS:

On Wednesday, March 31, and Thursday, April 1, the CarterCopter flew again at Olney, Texas. This was the seventh flight test program in the series. A little more than two additional hours of flight time were added to the 5 1/2 hours previously accumulated. The initial flight tests in September 1998 had been at Olney but testing was later moved to Sheppard AFB to take advantage of the longer runways.

CHANGES MADE SINCE THE PREVIOUS FLIGHT TEST:

The rotor head was modified to lessen control stick shake and control forces. Bearing blocks were added allowing the teetering axis to be raised two inches. Now, when the rotor 'cones' during flight, the blade teetering axis is closer to the blade center of gravity. An elongated hole was cut in the top of the rotor-head spinner to accommodate the raised collective arms and forks.

The engine was reworked. The compression ratio was increased from 8.2:1 (setup for turbos) to 10.3:1. An oil leak was also fixed. Oil had been leaking into the intake manifold and fouling sparkplugs.

The electronic prop controller was reworked.

A landing gear position sensor was added so the main gear would raise and lower together when on the ground. This function is used to set the aircraft pitch attitude for takeoff.

The nose-gear extension was removed in the expectation of doing zero-roll takeoffs and landings. This in turn placed the tip of the nose boom very close to the ground. A small skid was added under the tip as a precautionary measure. Small skids were also added just forward of the two rudders. The bottoms of the rudder extensions were trimmed to align with the skids. All of this was done as a precaution against dragging the tail during a nose-high flair.

A calibrated "dip-stick" was added for the fuel tank, so that fuel quantity could be verified visually.

PROBLEMS OCCURING DURING THESE TESTS:

The engine was run at a higher RPM than before in an effort to gain additional HP. At the higher RPM, the prop efficiency was less. The net result was less thrust than needed to perform the hoped for zero-roll takeoffs.

Flight Data previously collected on the prop controller had been insufficient to fine-tune the software. The prop has so little inertia due to its lightness that a slight pitch change results in an almost instantaneous RPM change. The result is that the prop controller tends to hunt for the optimum RPM. This hunting causes RPM and thrust surges that were disconcerting to the test pilots, Don Farrington and Jay Shapley.

An intermittent problem with the digital readout for the rotor RPM also hampered the flight tests. A faulty transducer is suspected. An analog readout in the cockpit provided rotor RPM information to the pilot, but the information could not be transmitted to the ground "flight control center."

Because of these problems, the airport pattern was not flown. Flying was limited to 120 ft. over the runway.

With the nose-gear extension removed, the aircraft sits in the pronounced nose down attitude that is needed for jump takeoffs. Fuel was limited to 30 gallons to save weight and to reduce the fire hazard in case of an accident. It was reasoned that the limited onboard fuel combined with the nose down attitude might hamper fuel pick-up from the fuel tank's rear pickup. The fuel pumps for both the front and rear tank pickups were therefore ran at the same time. Unknowingly, the pump for the rear tank pickup lost its prime and could not re-prime itself against the pressure from the other pump. With no fuel to keep it cool, the pump for the rear tank pickup "burned out" and had to be replaced.

FLIGHT TEST ACCOMPLISHMENTS:

The changes made in the rotor head proved effective in reducing stick shake and stick forces in the speed ranges flown. Don felt the arrangement is now acceptable although there is still room for improvement. Since the airport pattern was not flown, airspeed never exceeded 95 MPH due to the short length of the runway. Stick shake and stick forces above 100 MPH were therefore not tested.

Short-run takeoffs and landings were made for the first time with the landing gear in the normal "lowered" position. With the body of the aircraft close to the ground and tilted forward on the much shorter nose gear, Don was presented with a new sight-picture from the cockpit. New techniques were developed for both takeoffs and landings, including a technique for gently lowering the nose-gear to the ground after landing.

Sufficient data was collected this time to fine-tune the prop controller.

CHANGES NEEDED BEFORE THE NEXT TESTS:

The prop-drive pulley ratio will be changed so the engine can operate at a higher RPM and produce more HP, while at the same time the prop will operate at a lower, more efficient RPM. The net effect will be more thrust for takeoff.

The software for the prop controller will be fine-tuned to prevent RPM hunting.

The diameter of the orifices in the landing gear air/hydraulic solenoid valves will be enlarged to speed up extension and retraction time.

Both fuel pumps will be connected with a by-pass line that allows either pump to re-prime itself even against the pressure of the other pump. Normally only the pump tied to the rear fuel tank pickup is engaged since it will run dry first when the aircraft is on the ground or in a high speed cruise mode. Another reason is that as the aircraft slows down, the aircraft pitches up slightly allowing some 10 gallons of fuel to run back to the rear tank pickup.

GOALS FOR NEXT FLIGHT TESTS:

The next flight test is tentatively scheduled for the week of April 19. The goals will be the same as last time: do zero-roll takeoffs and landings; raise and lower the landing gear in flight; fly the airport pattern; and explore the airspeed range between 100 and 125 MPH.

SUN 'N FUN FLY-IN AT LAKELAND, FLORIDA:

Jay Carter, JR will give two forums for NASA. The latest flight videos will be shown and Jay will try to answer all questions. Models of the "CarterCopter Twin-jet" and "Ultra Long-range CarterCopter" will be displayed. The CarterCopter will not be present.

OSHKOSH 1999:

The CarterCopter will hopefully make its first public flights at Oshkosh this summer. The goal is to demonstrate zero-roll takeoffs and landings, and flights down the runway at 150 MPH or greater. At this speed the rotor will be basically unloaded and the wings will be carrying most of the aircraft's weight. The rotor will be slowed to between 100 & 150 RPM and the retreating rotor blade will have 100% reverse airflow over the airfoil. No other rotorcraft has been able to achieve this.

We hope we will see you there.