Wichita Falls, Texas: Monday, June 12, 2000

Edited by Rod Anderson

FLIGHT TESTING TO RESUME IN EARLY JULY

We have been very busy the past several months trying to complete the repairs, make improvements and do the proof testing. The repairs and improvements took longer than hoped, but the proof testing on the wing, prop and rotor head structure were completed with only a small void problem on the leading edge (L.E.) of one prop blade. The new rotor system is completed and is undergoing testing in the test pit (see status below). Between debugging a new data-collection system for the test stand, chasing down some hard to explain vibration frequencies, and adding L.E. weight to the rotor blades to fix a blade weave, we lost a precious 3 weeks. We expect to be flying approximately 3 weeks after the rotor tests are completed. Unfortunately, insufficient time remains to do everything that is needed and still fly to Oshkosh. We decided last year that we would not take the aircraft back to Oshkosh until we could fly it there and show off.

NOTABLE BENCHMARKS FOR APRIL

• Completed the new 96" diameter prop, which weighs 10% less than the previous prop (27 lbs. total, including hub, pitch horn and linkage).
• Completed the prop test program. Total of 12 minute run time @ Mach 0.63, 0.71, 0.79, 0.87, 0.95, & 0.99.
• Completed torque proof test on the rotor drive.
• Completed installation of co-pilot flight controls in the cockpit.
• Finished a design study of the CarterCopter Heliplane. The VTOL has full hover capability and is similar in size, performance and cargo capacity to the C-130 Hercules. A press release describing its features, performance, and with drawings showing how it might look will be released soon.

New prop static performance:

*Drive ratio will be 2.75 for aircraft vs. 2.387 used for test stand. Engine RPM is limited to 6500 maximum as set by the engine computer.
**0.85 Mach is max resultant tip speed limit in-flight as set by the prop computer.

NOTABLE BENCHMARKS FOR MAY

• Completed fabrication of the new rotor. The new rotor, hub and blade pitch horn weigh 274 lbs., which includes129 lbs. of L.E. weight (inertia & C.F.). The rotor is 43.5 ft dia. x 40.5 ft2 area. The original rotor, hub and blade pitch horn weighed 240 lbs., which included 110 lbs. of L.E. weight. (33.5 ft dia. x 27.6 ft2 area).
• Selected 3 new pilots (see website for resume)
• Moved the prop pitch computer and some data collection hardware from behind the instrument panel to a more accessible location at the rear of the cockpit.
• Completed 16,000-lbs. proof load test on the new rotor head (from mast attachment to rotor spar).
• Completed 12,000-lbs. proof test on the rotor head mast attachment, including an additional moment load of 7500 inch-lbs.
• Completed 4-g proof test on the repaired wing (based on a max gross weight of 3000 lbs.).
• Filed additional patent improvements and new patents relating to the CarterCopter Heliplane.

WORK REMAINING BEFORE NEXT FLIGHT

1. Finish the rotor test.
2. Remove the engine from the test stand and re-install it in the CarterCopter.
3. Complete the installation of the new oil cooler, two new radiators and the two air coolers for the low and high-pressure turbo (the turbo will not be installed at this time).
4. Complete the installation of all electrical systems (including the voice alarms).
5. Complete the installation of the variable-opening cooling air duct.
6. Fabricate a new, larger diameter prop spinner.

STATUS OF ROTOR TESTS

The goal is to verify that the rotor system can operate smoothly to an over-speed proof RPM of 465 (tip speed of Mach 0.95) without blade weave, flutter or divergence. If 465 RPM is unattainable, the tests will go to the maximum RPM possible at flat pitch with maximum HP available from the engine. Maximum jump takeoff RPM is expected to be 425. The procedure is to increase RPM by smaller increments at each increase in rotor RPM speeds. At each RPM increment the rotor is excited with progressively larger collective pitch jabs until collective is at its maximum or the lift reaches 5000 lbs. If the loads are satisfactory and any oscillations that occur dampen out quickly, then the tests proceed to the next higher RPM level. Once the maximum RPM has been reached, the rpm will be lowered to 425, the clutch disengaged, and the collective pulled as required to first hold 3500 lbs. as long as possible (record the time), then 4000 lbs., 4500 lbs., and finally 5000 lbs.

During testing, the following information is recorded on a strip chart recorder:
 

1. blade pitch
2. flapping
3. blade pitch link load
4. cyclic loads
5. rotor RPM
6. rotor lift
7. collective stick force
8. pylon movement fore & aft and side-to-side

At 375 RPM, the rotor experienced a blade weave, which did not fully dampen out until the RPM dropped to 250 RPM, which took 7 seconds. The new rotor was built with the same chordwise balance weight of 55 lbs. (depleted uranium) per blade as used in the previous, shorter rotor. It was calculated that by making the trailing edge lighter on the new blades by using honeycomb and carbon prepreg, it might be possible to mass balance the blades without additional L.E. weight. In the event additional weight was needed however, the blades were fabricated with two hollow L.E. cavities in which lead shot mixed with resin could be added. To resolve the blade weave problem, the smaller outboard cavity on each blade was filled with 9 ½ lbs. of lead shot mix, bringing the total L.E. weight in each blade to 64 ½ lbs.

We tried to increase the pylon dampening to reduce an oscillation that occurred at 100 & 200 RPM. The change did more to increase the spring rate than increase the dampening and made matters worse. To solve this problem, so the rotor can operate continuously at any rpm, additional instrumentation was installed. Several consultants were invited to observe the tests and help analyze the data. During one of the following test runs, the rotor head got into an oscillation that bent the cyclic control rods (required a load greater than 2400 lbs.) and cracked the spindle housing where the cyclic rods attach. We believe we understand what happened. While a new spindle housing is being made, the pylon attachment to the (very rigid steel) test stand will be modified to provide a lateral softness more closely matching the aircraft. Also, the blade-teetering bearing supports will be stiffened in the lateral direction. Further testing will confirm if these changes solve the problem. There is always a certain amount of trial and error with any new design, so the time factor for completing the rotor tests is uncertain.