Subject: NAS2-99090 December monthly report

Date: January 2, 2001

Work completed in December prior to December 13th flight:

1. Finished gearbox
2. Added scoop to front and modified cooling duct for better airflow.
3. Reinstalled rotor, rotor head, prerotator including new gearbox.
4. Tested rotor system and prerotator in the pit.
5. Recalibrated some of the data collection sensors.

Flight-testing of the CC prototype resumed at Olney on Wednesday, 13 December (the day before the Popular Mechanics award presentation). The pilots made 12 flights down the runway. During the takeoff and climb portion of each flight the pilots' effort was directed towards understanding how best to use the stored energy in its rotor. They also wanted to see how quickly rotor rpm would increase during flight once the collective was reduced. Both pilots were delighted with the results. The first few landing sequences were used to confirm the ease of performing zero-power landings with the incredible amount of rotor inertia available. The pilots were more excited than ever before about the aircraft's responsiveness and the obvious potential for performing zero-roll landings. They felt the first zero-roll landing would come before the end of the day. They commented that the prototype flew so smoothly they could not tell by feel that they were flying in a rotary wing aircraft. They compared the sensation to flying in a sailplane in smooth air. There was a complete lack of rotorcraft-type vibrations or shake of any kind. This perception of smoothness included the controls. There was absolutely no stick shake. This is very unusual -- especially in a direct control rotorcraft with no boost.

At the conclusion of the 12th flight, the totally unexpected happened again. The CC landed gently at 30 MPH with plenty of runway remaining. For reasons unknown to the pilots at the time, the brakes were not effective. The CC slowly ran off the end of the runway at 20 MPH.

Rolling slowly off the runway at 20 MPH would have been a non-event as the pilots hoped except for the fact the ground was very soft from recent rains. As a result, the front landing gear sank to its axle. The intense drag this created caused the (long) front landing gear to fold back as though it was retracting. Even with the gear folded back the incident would have remained a non-event except for the 4 feet long nose boom (part of the ballistic chute system) that speared the ground with the 3,000 lb aircraft pushing. The sudden stop from 20 MPH caused the CC to pitch over on its nose to a near vertical position -- allowing the rotor to strike the ground. The wing prevented the aircraft from rolling over to one side. Moments later the aircraft fell back onto its landing gear.

If the nose gear had not folded under -- the nose boom could not have speared the ground and nothing serious would have happened. The nose gear had folded under during the December 1999 accident with similar results. That time it had folded due to the forward pitching moment cause by the hard landing and the brakes being applied hard. To prevent the same thing happening again, additional oil was added to the front gear. This allows the front gear to bottom out before it can compress enough to allow the nose boom to (again) dig into the ground. Every time the gear is retracted (either fully or partially) the current oil-air separator permits a fine mist of oil to escape into the air. The oil is automatically replaced from a reservoir, but only when the gear is fully retracted in flight. During each of the numerous trips to and from the pit to proof-test the rotor and gearbox, we had to partially retract the front gear to clear the top of the door opening at the CC shop. Apparently enough oil escaped into the air from these numerous retractions to let the nose gear compress too far -- again. During our subsequent flight-testing, the flights down the runway were too brief for the pilots to retract the gear which would have automatically replaced the escaped oil.

Damage to the CC prototype includes the following: (1) the rotor was destroyed, (2) the rotor mast was damaged, (3) both rudders were clipped off near the top by the rotor, (4) the right wing was broken about 5 ft from the tip and (5) several parts of the rotor head and prerotator drive will need to be replaced. The reinforcement we added to the rear wing spar attachment after the December 1999 accident kept the wing from failing again at the root. The damage to the aircraft can be repaired in 3-4 weeks. It will take 2-3 months to build, balance, & install a new rotor and then proof-test everything in the test-pit.

Looking at the data transmitted from the CC during flight-tests solved the mystery. Once reaching 400-ft. altitude the pilots had progressively lowered the collective a little more than they did the previous flight. This allowed the rotor to speed up before they started the landing flare. The pilots were surprised at how slowly the rpm dropped as collective was pulled to keep the aircraft in the air -- and how far they were able to float down the runway. As they got closer to the end of the runway, they decided to let the aircraft settle onto the runway by not pulling any more collective. At this point the rotor rpm was 180, the airspeed 30 mph and the collective 8.5 degrees. At touch down, the pilots were discussing the beautiful flight and the energy remaining in the rotor. Collective was inadvertently not lowered before applying the brakes and with the rotor still providing a lot of lift, the wheels just slid lightly down the runway without providing the needed braking action.

An alternative braking solution (beside the brakes) was available but was not used soon enough. The rotor on any gyroplane can be tilted back to provide a rotor brake during the landing procedure. The method was used in this case but only after rotor rpm and lift had dropped off -- permitting the brakes to become more effective. The aircraft is normally tilted forward 3.5 degrees, so the rotor has to be tilted back 3.5 degrees just to be level with the runway. To provide enough rotor tilt to be effective at stopping the aircraft, the CC must be rocked backwards onto its tail boom training wheels. In this case it was not tilted back far enough or soon enough to overcome the forward pitching moment of the brakes.

This is the second time the aircraft has suffered major damage as a result of the nose boom digging into the ground after the nose gear compressed (the December 1999 accident was the first). In this case if the nose boom had not dug into the ground, the nose of the aircraft would have slid across the ground and little if any damage would have been done. To prevent the possibility of this happening a third time, the boom will be shortened so it cannot dig into the ground.

A new oil-air separator has been designed for the nose gear minimizes oil from escaping when the gear is retracted. This should prevent the nose gear from being able to compress and fold under due to a shortage of oil -- should a similar emergency occur in the future.

A Pilot Operating Handbook (POH) for the CC gyroplane has been under development for some time by our pilots. Now they intend to include a new section on fast stop procedures while taxiing. An effort will be made to brainstorm as many other emergency scenarios as possible and work out the best procedures in advance. At some point in the future when finances permit, the ideal solution might be to develop a CarterCopter flight simulator and incorporate these scenarios for training purposes.

Work completed since the accident.

1. Removed engine, prerotator drive and rotor head from aircraft.
2. Shorten nose boom.
3. Repaired fuselage mast and reinstalled ceiling supports for 15,000 lbs. mast proof tests.
4. Prepared spar mandrel for next lay-up.
5. Finished machining rotor spinner plug.
6. Completed inspection of aircraft and determined damage.
7. Ordered materials to build new rotor.
8. Started making new metal parts to replace those lost in accident.

Major items yet to be completed before next flight - est. mid March

1. Modify blade molds to incorporate T.E. trim tab extensions.
2. Fabricate spar, blade skins and bond blades together.
3. Repair right wing, rudders and vertical stabilizers.
4. Complete mods to landing gear.
5. Rebuild cooling air cowl flap to reduce internal pressure drop and provide better suction from propeller.
6. Change prerotator ratio to provide enough torque to proof test rotor at 450 RPM.
7. Test rotor and prerotator in pit.