6 October 2003, Wichita Falls, Texas

We apologize for the length of time since the last update. We have been very focused on repairing the aircraft and getting it ready for flight testing. We will try to make future updates more routinely.

CarterCopter Rebuilding Update

It has been almost 6 months since the CCTD suffered significant damage in a wheels-up landing on 8 April, 2003. The interrupted flight test program to break the Mu 1 barrier will resume shortly with hopeful expectations. A special thank you goes to the many donors to the OSAC Mu 1 club. Their generous donations provide emotional and financial support as well as welcome reaffirmation of our efforts. Anyone still interested in contributing is very welcome. We will proudly write the names of all donors on the aircraft.

 

Repaired CCTD

During the rebuilding program, we incorporated improvements that took much longer than expected (mapping the turbocharged engine is one painful example) and added some improvements to the project (total overhaul of the data collection wiring). Many of the known weaknesses of the aircraft were corrected (landing gear retraction system, communication system) and we believe we are in good shape to proceed. The following list details the tasks accomplished in the past 5 ½ months.

Airframe repair: Repaired the co-pilot rudder, both tail booms where they attached to the wing, the rotor, the upper rear fuselage and its attachment points. Made a new shaped lower rear fuselage section to decrease air-flow separation and decrease the drag. Made a new fiberglass cross-over beam to support the prop bearing , a new prop drive shaft and bearing support, 2 herringbone prop drive pulleys, belt idler, engine support plates, prop collective shaft and hydraulic actuator, 2 belt accessory drives with dual redundant water pump drive, and a new propeller same design as before.

New Engine: Installed a new turbocharged 427 cu in Bow Tie LS 6 engine. This engine uses the C5-R block with the best racing components and special CNC ported heads. It should produce 400hp reliably and deliver 600hp for short periods. The turbo is sized to maintain 42 inches of boost up to 20,000 ft. Also added turbo cooler and auto controlled waste gate. Increased the size of both the turbo oil suction pump (1.6 times) and the hydraulic boost pump (2.3 times). Incorporated a 10 micron high pressure filter on the boost pump. Mapping this turbocharged engine was a major obstacle since we had great difficulty finding an available knowledgeable expert willing to work on an aircraft application. This engine is used routinely in the same configuration in racing cars. The belt idler force had to be increased to handle the higher torque. A second reason for increasing the belt idler force is that the quieter herringbone belt drive has a rounded tooth profile which has more of a tendency to push the belt away from the pulley under load.

 

New Engine & Turbo Being Installed

Aircraft Control Systems: Modified the cyclic boost control so that if boost pressure is lost when the rotor is at a very high mu and unstable, the irreversibility feature is maintained long enough for the rotor to speed up to a stable rpm. Tests will determine just how long the irreversibility will last. The cyclic boost has also been set up so that the boost pressure can be turned on and off to permit us to test how the cyclic functions in flight without boost. The cyclic spool valves were modified so that there is about .009 of dead band before the valve starts to open. For the last flight the spool valves had been modified for zero dead band. With zero dead band, there was excessive leakage and there was no irreversible feature possible. Collective in manual mode has been changed so that the pilot has to push on the button on the end of the collective and then apply approximately 20# (adjustable) force to move the collective. The collective will then move at a slow, but mechanically adjustable rate. If the pilot applies approximately 40# of force, the collective will move at its fastest rate. There are 3 new switches added to a separate switch panel located on the end of the collective. The left switch of the three is a kill switch for some of the new auto controls (flapping, rotor rpm, and pylon position). It does not kill the prop auto pitch/rpm control or the waste gate control. The center switch is a momentary type switch that controls the up and down movement of the collective. Pushing or tapping the switch forward moves the stick down and pulling or tapping it aft moves the stick up. Tapping moves the collective slowly and will be used for a fine trim control. Any time the collective is operated, either with the center switch or by pulling/pushing the stick or by the controller in auto mode, both the air and hydraulic boost are activated. If either the air or hydraulic boost were lost, the other system could still move the collective without the pilot first having to determine which system failed. The right switch on the collective switch panel is a momentary switch that turns on the engine cooling water spray. Pulling the switch aft turns the spray on.

Landing Gear: The landing gear extension and retraction system was unnecessarily complex and unreliable. This was one of the reasons it was not used frequently during the flight-testing. An entirely new and much simpler landing gear extension and retraction system was installed. This system uses a special oil gear pump, which is basically 3 pumps in one, one for each of the three landing gear legs. The pump transfers the oil from one side of the landing gear cylinder to the other to cause the gear to extend or retract. This eliminates the need for a lot of compressed air and about 15 solenoids, several accumulators and an oil / air separator. The air in the top of the cylinder creates the spring action. This air is captured and does not need to be replaced unless there is a leak. The new design should be much more reliable than the last design but we did have to be creative with the gear motors. We were not able to find an off-the-shelf 12 v motor the size and hp needed. We had to use a 24 v motor with relays to convert 2 batteries back and forth between a 24 v system for operating the motor and a 12 v system so the batteries can be charged.

 

New Landing Gear Being Bench Tested

The Fuel System: The fuel system still has 2 separate fuel pumps and filters, but we now use 2 larger high pressure pumps that do not require a separate low pressure pump to first suck the fuel out of the tank. The fuel system now has a fuel flow meter so we can determine engine efficiency (BSFC) and aircraft efficiency (MPG). The fuel system is simplified in that there is now only 1 fuel line to the engine instead of 2.

Electronics and Wiring: The communication radios and hot mic set up were rebuilt. New cables, connections, ground plane and antenna are expected to improve reliability and quality dramatically. Over the years, the sensor system had accumulated numerous additions and deletions, many of them poorly documented. We believe that the required data set is now understood so all unnecessary wiring was removed. All the sensors have been rewired with shielded cables and connected to a common ground. The computers are now tied together in a more direct fashion and considerable effort has been made to reduce the electrical noise getting into the system. The rewired system is now much more likely to remain calibrated and we expect a large amount of reproducible data from the upcoming flight test series.