Wichita Falls, Texas: Sunday, 22 July 2001

Edited by Jeff Keaton and Jay Carter, Jr.

CCTD APPEARANCE AT OSHKOSH DELAYED UNTIL 2002

With hard work by the entire CarterCopter (CC) crew, the CC Technology Demonstrator (CCTD) was ready to fly again just 10 days after we blew the LS1 engine (see previous press release). The short turn-around time prevented the GAA from having a representative attend the recent five day flight-test session that ended Wednesday 18 July. The plan was to break the Mu-1 barrier and then take the CCTD to Oshkosh for AirVenture 2001. We felt the chances were sufficiently good that we could do this - that we also repainted the CCTD at the same time we were replacing the LS1 engine with a new LS6. It now looks very nice with new paint, numbers and stripes and all hangar rash repaired.

We made progress towards our goal but were unable to break the Mu-1 barrier in the time allotted. Four of us now plan to drive to Oshkosh, arriving Monday morning. Jay's forum at Oshkosh is at 10:00 AM Tuesday, July 24. He plans to leave Wednesday and be back in Wichita Falls on Thursday. Some members of the CC crew will remain at AirVenture the entire week. The CC exhibit in area 151 next to the Shell Plaza will display our new CCTD flight simulator, our data download system, a new 1:72 scale model of the CCH-T, video of the CC flight-test program and other CC components. We hope you will attend AirVenture and come see us.

PROGRESS CONTINUES: NEW RECORDS

The recent flight-test series began Saturday 14 July. The first day was limited to 12 flights down the runway to check out the new LS6 engine and a new engine-driven air compressor. At 5400 RPM (max takeoff, short duration RPM) the new engine produced nearly 40 more HP than the old engine (LS1) - which is consistent with GM claims. The mechanical air compressor worked great. Landing gear retraction time was cut in half (to 8 seconds) and extension time (including the time it takes to fully pressurize) shortened from 4 minutes to 20 seconds.

On the second, third and fourth day, we flew to 4000 ft MSL and cautiously and gradually increased the airspeed to 139 MPH. Rate of climb with the gear retracted exceeded 750 fpm. Both the airspeed and rate of climb were new records for the CCHT. We confirmed there were no vertical oscillations occurring over a large range of airspeeds and collective pitch settings. This had been a major concern due to a severe vertical oscillation that occurred at 125 mph on a flight in late 1999 by Don Farrington. The problem was addressed by changing the blade spring toggle point and putting blade pitch stops at the rotor head instead of at the collective arm in the cockpit.

A problem with prop controller hunting is almost gone, but there remains some tweaking to do. Short takeoffs and landings are slowly becoming routine. L anding rolls are now as short as 20-ft, which is another new record for the CCTD.

During one test flight on July 17, we observed a three-second oscillation that at first appeared to be a blade weave. After viewing the tail camera and analyzing the downloaded telemetry data, we determined that the oscillation and accompanying high stick loads was not the result of blade weave. It seems to have been caused by a combination of blade flapping, rotor RPM and a collective setting close to the b lade toggle point.

TWO FLIGHT TEST DISCOVERIES

During this testing, two things became apparent:

Although we knew the wings would be in a stall at lower airspeeds, we did not expect that the pilot would have to constantly make side-to-side stick corrections to keep the aircraft level. Most noticeable between 75 and 90 MPH, this instability and constant stick movement caused an oscillation that showed up in a number or telemetry parameters. It took a few days to determine what caused this varying low frequency oscillation in so many parameters.

The second unexpected discovery is that when the inboard wing stalls, it causes most of the airflow over the rear aft section of the fuselage to separate and create several additional square feet of equivalent flat plate drag.

Our drag is much higher than expected. We realized some time ago that the rotor needed to be moved back relative to the aircraft CG to reduce the amount the aircraft would be pitched up at lower airspeeds. At lower airspeeds the wing is in a stall that creates a considerable amount of drag. But once the wing is out of stall, the drag should drop enough to allow us to break the Mu 1 barrier with the available horsepower.

It is now clear that the angular relationship between the rotor, wing, and horizontal stabilator needs to be changed in order to further unload the rotor and allow the rotor RPM to drop. At 139 MPH and nearly full horsepower, the rotor was still at 220 RPM and producing excessive drag (at this speed we would ideally like for the rotor to be down to approximately 160 RPM.

ROTOR MAST TO BE TILTED 6° BACK

Before we fly again, we plan to cut the mast off where it joins the fuselage, tilt it back and reattach it to the fuselage so that the aircraft will hang 10º pitched down rather than the present 3½º. This modification will reduce the fuselage pitched-up angle and wing angle-of-attack about 6½º at 50 MPH, but cause no change at 150 MPH since the rotor will be basically unloaded. This should get the wing out of stall by 75 MPH and greatly reduce the aft rear fuselage separation at 100 MPH - all of which will significantly reduce the total drag and improve both climb performance and visibility over the nose at low airspeeds. It will also make vertical takeoff and landings much easier.

Additionally, we plan to modify the nose landing gear to have a much higher spring rate. This will minimize any deflection that could allow the nose to pitch over too far. We also plan to increase the main gear spring rate so the aircraft does not lean as much when torque is applied to the rotor during pre-rotation.

MU-FLIGHT IS CLOSE

We believe the rotor tilt modification will allow us to achieve airspeeds of 150 MPH at a rotor RPM of 160 or 160 MPH at a rotor RPM of 100, i.e. break the Mu 1 barrier.

We plan to resume test-flights in early August after Airventure 2001.