Subject: NAS2-99090 May monthly report
Date: June 1, 2000

The following list of items was completed in the month of May.

• Completed rotor blade fabrication and installation on test stand. New rotor, hub and blade pitch horn as completed weighed 255 lbs (43.5 ft dia. x 40.5 ft² area) vs. original rotor, hub and blade pitch horn of 240 lbs. (33.5 ft dia. x 27.6 ft² area). Both rotors have the same 110 lbs. of depleted uranium inertia and mass balance weights.
• Completed 16,000-lbs. proof load test on new rotor head from mast attachment to rotor spar.
• Completed 12,000-lbs. proof test on rotor head mast attachment with additional moment load of 7500 in-lbs.
• Completed 4-g proof test on repaired wing based on a gross weight of 3000 lbs.
• Selected 3 new pilots - See website for resume.

Rotor testing

The completed rotor blade is currently under test in the test pit. The goal is to verify that the rotor and system can operate up to an overspeed proof RPM of 465 (tip speed of Mach 0.95) or maximum RPM possible at flat pitch with maximum HP available from the engine without blade weave, flutter or divergence. Maximum jump takeoff RPM is expected to be 425. It is expected the pylon will go through several natural frequencies as the RPM is increased. The ability of the elastomeric pylon bearing/dampers to keep the amplitude from being excessive and how rotor lift affects the amplitude will be monitored.

The following are monitored 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

The test procedure will be to increase the RPM in smaller increments as the RPM is increased. At each RPM increment the rotor drive clutch is disengaged, and the system 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 dampen out quickly, then before proceeding to the next RPM level, the rotor clutch is disengaged and the collective is pulled as required to first hold 3500 lbs. as long as possible, then 4000 lbs., 4500 lbs., and finally 5000 lbs.

Test results through June 1^st

The pylon has a fore and aft natural frequency at 100 and 200 RPM. The elastomeric bearings keep the amplitude and loads within acceptable limits, however continuous operation at these RPM will be avoided. By accelerating the rotor rapidly through these RPMs, the oscillation is barely noticeable. A slight amount of rotor lift also reduces the oscillation amplitude. At 375 RPM, the rotor experienced a blade weave, which did not fully dampen out for 7 seconds until the RPM had dropped to 250 RPM. Additional chordwise balance weight over the 55 lbs. of uranium was not used in the new blade. It was determined that by making the trailing edge lighter on the new blades (use of honeycomb and carbon prepreg) it might be possible to mass balance the blades without any additional L.E. weight. In the event weight was needed however, the blades were fabricated with 2 hollow L.E. cavities in which lead shot mixed with resin could be added. The smaller outboard cavity on each blade has been filled with 9-1/2 lbs. of lead shot mix. Rotor tests are expected to resume on Monday, June 5^th.

The following items need to be completed before the aircraft can fly again. The next flight is expected 3 weeks after completion of the rotor test.

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