The X-Cell Custom Graphite SE was the state of the art helicopter from Miniature Aircraft in 2000. Designed and built using graphite for the frames and tail boom along with anodized machined aluminum for the majority of the construction.
This helicopter was originally built in 2000 and equipped with JR radio equipment. Flown with a YS 61ST-2 engine, it flies with a very fluid style and is able to deliver performance in a wide range of forward flight speeds. It was designed for traditional maneuvers and acrobatics and was used prior to the surge in the 3D flying style so commonly seen today.
The model originally was flown with a JR 8103 radio system and equipped with a JR 9 channel PCM receiver, using JR 4131 Ultra Precision servos for the cyclic and throttle controls and a JR 810 G servo for tail rotor control. This was updated in 2003 to being flown with a JR 10x radio system, using JR DS8231 Ultra Precision Digital servos for the cyclic and throttle controls and a JR DS8317 Digital High Speed MG servo for the tail rotor. It is also equipped with a CSM ICG 540 Heading Lock Gyro.
The current work that is being undertaken for this project is in 3 phases to update the helicopter's electronics and flight worthiness.
The first phase is the overall mechanical inspection and review of flight worthiness. This included checking all mechanical parts such as the rotor head, tail rotor assembly, and main frame assembly. It also included removing the engine for detailed inspection and maintenance.
The specific groups and parts of the helicopter that were inspected included the following:
The frames and internal assembly structure (primarily constructed out of carbon fiber/graphite layup and assembled with aluminum hardware with metric steel cap screws and related nuts). Overall the framework and structure is in excellent shape. A support for the engine fan housing was found to have cracked and it was replaced. The cause of the crack is most likely due to a high speed vibration caused by an imbalance in either the cooling fan alignment on the engine or the main rotor head assembly (discussed in later sections).
The engine assembly for the YS 61ST-2 was removed, including removing the Hatori tuned pipe assembly and engine fan housing. Upon removal of the engine it was cleaned and checked for signs of improper use. The engine shows minimal signs of wear with little build-up of varnish internally. The bearings are in excellent condition as is the carburetor assembly and overall looks to be in very good working condition. After inspection and minor cleaning the fan assembly was removed and cleaned and checked for balance, then reassembled and aligned with minimal run out using an indicator during reassembly. Locktite was re-applied to metal to metal threaded parts to assure they will not loosen due to mechanical vibration while in use. Both fuel tanks (the main fuel tank and the 2 oz. reserve tank) were inspected. The main tank is in excellent condition and full usable. The reserve tank showed signs of shrinkage and dry out of the internal fuel tubing for the clunk and has been replaced.
The main rotor head was then inspected as were the existing main blades. The main blades in use are sport carbon fiber/graphite blades and they were found to be out of balance from each other by 1 gram. This would certainly be cause for concern and could account for the high speed vibration that may have caused the crack in the fan housing support. The blades were balanced using self-adhesive monokote trim tape and cg of the main blades was also checked and balanced for the set. The mechanical assembly of the main rotor head was found to be in excellent condition. The flybar assembly did show a 1mm play side to side and this was corrected by the adjustment of the set screw on the flybar, using locktite on the set screw during reassembly to prevent loosening. All other parts of the main rotor head are in excellent condition and required only minor cleaning.
The tail rotor assembly was removed and inspected and found to be in excellent shape. The gear assembly internal in the tail rotor box was found to be well greased and clean, and reassembly was completed with minor cleaning as on other areas of the helicopter.
With the completion of the mechanical inspection the helicopter was ready for electronic inspection and updates.
The second phase is the update of the helicopter's electronic systems. This included replacement of the receiver, power supply/flight battery, and the heading lock gyro.
The existing JR 9 channel PCM receiver has been replaced with a Spektrum AR7100r Rev Limiting 2.4GHz Helicopter receiver. This particular receiver was chosen due to its ability to use higher power battery packs for running the electronic systems of the helicopter and also the ability of the Rev Limiting function for managment of rotor head speed. It is designed to used Nickel Cadmium (NiCad), Nickel Metal Hydride (NiMH), Lithium Ion (Li-ion), or 2 cell Lithium Polymer (LiPo) battery packs. The battery packs can have a voltage of 6 to 10 volts. In addition the Spektrum AR7100r receiver has an internal voltage regulator for the gyro, rudder, and throttle servo, reducing the main voltage down to 5.2V for use of all 4.8V servos without issues of possible damage or failure due to excess voltage. The Rev Limit Sensor comes with an adjustable plastic bracket for attaching it to the backplate of the engine. This was replaced with a CNC Machined aluminum bracket for durability.
The power supply for the flight pack has also been updated from a 5 cell 2400 mAh Nickel Cadmium battery pack to a JR 2 cell 4000mAh Lithium Polymer battery pack. A Spektrum VR6010 Voltage Regulator was chosen to reduce the voltage from 7.4V to a constant 6V for the receiver and servos.
Finally, the existing CSM ICG 540 Heading Lock Gyro has been replaced with a CSM SL720 Heading Lock Gyro. This was chosen as it will function in a similar manor to the ICG 540 gyro, but has substantial upgrades in software, operational programming and flight abilities.
The third phase involves the transition from a JR 10x transmitter to the JR 12x transmitter for flight control. This included full review of the existing programming of the JR 10x transmitter and transfer of these settings to the JR 12x transmitter. After transfer and programming was completed, full inspection and measurement of all flight control movements and deflections were completed to insure the helicopter will operate safely as well as provide full range deflection for flight control.
The project has taken approximately 2 weeks and is currently ready for initial test flights and adjustment. Additional test flights and final adjustment will be completed prior to conclusion of the project.
This helicopter is in the inventory of Morrow Creative Associates LLC. Please contact Robert through the Contact Us page if you have questions or would like further information regarding this project or the availability of the helicopter.