The Jasco alternator upgrade for Beechcraft Bonanza A35 aircraft, specifically models A through G and the 35R (serial numbers D-1 through D-4865), represents a significant electrical system improvement. This upgrade replaces the original generator with a higher-output alternator, addressing limitations in electrical capacity and enhancing safety, particularly during nighttime operations. The upgrade, covered under STC No. SA999WE, requires careful installation and attention to detail, as the provided kit includes only the alternator, voltage regulator, and instructions; the installer is responsible for procuring all additional necessary components.
System Components and Specifications
The Jasco alternator system, Model 6560T-1, is designed as a direct replacement for the existing generator. However, the upgrade is not a simple swap. The system includes a new alternator and voltage regulator. Detailed specifications and installation diagrams are available from Skytronics Inc. The system overhaul documentation provides information on installation, wiring, cooling requirements, and maintenance procedures.
Installation Requirements and Considerations
Several key aspects of the installation process require specific attention. The STC kit does not include all necessary hardware, placing the onus on the installer to source additional components.
- Wiring: The original 12GA primary feeder wiring is inadequate for a 50A electrical system and must be replaced with 8GA wiring.
- Drive Coupling: The alternator includes a new drive coupling with rubber isolation blocks. Preload on the coupling assembly should be between .005 and .008 inches. Clarification regarding the proper procedure for checking this preload may be required from Skytronics.
- Mounting Bracket: The alternator utilizes the same mounting style as the original generator, but the included alternator is a different size. Therefore, a custom mounting bracket must be fabricated to ensure proper positioning.
- Terminal Strip: Due to the increased wiring requirements for the new regulator, a terminal strip is necessary. It is recommended to install this strip on the regulator mounting bracket to minimize wire lengths and facilitate future maintenance.
- Firewall Connector: The firewall connector offers available pins for the two 18GA wires that pass through the firewall. This connector utilizes a solder-pin design.
- Cooling Duct: The alternator requires a 2-inch diameter cooling duct, whereas the original generator used a 1-inch diameter duct. The aircraft’s cooling plenum must be modified to accommodate the larger duct.
- Prop Governor and Tachometer: Aircraft equipped with an older prop governor utilizing a T-drive for the tachometer cable may require repositioning of the T-drive due to the alternator’s larger diameter. Incorrect connection of the drive ends can cause the tachometer to function improperly.
- Electrical Breakers: The alternator system requires dedicated electrical breakers. One breaker is needed for the regulator, and another for the alternator field line. A switch/breaker is recommended for the field line, and a fuse is suitable for the regulator.
Electrical System Enhancements and Safety Improvements
The upgrade to the Jasco alternator provides substantial improvements to the aircraft’s electrical system. A Bonanza A35 owner reported the ability to operate both landing lights, navigation lights, the beacon, and radios at 1000 rpm without discharging the battery. The original 35A generator was unable to support even the radios at that speed. This represents a significant safety enhancement, particularly during nighttime operations, as the aircraft is more visible.
Wiring Diagram and Beech Wiring Discrepancies
The installation process requires careful attention to the wiring diagram. One installer cautioned against blindly trusting Beechcraft’s original wiring diagrams, noting that their aircraft’s wiring differed significantly from the documented schematics. Avionics engineering expertise may be beneficial in verifying and adapting the wiring configuration.
Regulator Mounting and Wire Management
Optimal placement of the voltage regulator is crucial for efficient wire management. Mounting the regulator close to the alternator minimizes wire runs and simplifies future replacement procedures. The terminal strip, installed on the regulator mounting bracket, further aids in organizing the increased wiring associated with the new system.
Additional Considerations
- Nut Specification: The documentation regarding the drive coupling check was described as “esoteric babbling,” prompting one installer to contact Skytronics for clarification on both the check procedure and the nut specification.
- Component Sourcing: The installer must provide all components not included in the STC kit, including wiring, mounting hardware, breakers, and the terminal strip.
- Compatibility: The upgrade is specifically certified for Beech 35, A35, B35, C35, D35, E35, F35, G35, and 35R models with serial numbers D-1 through D-4865.
Conclusion
The Jasco alternator upgrade for the Beechcraft Bonanza A35 offers a substantial improvement in electrical system performance and reliability. However, successful implementation requires meticulous attention to detail, careful component sourcing, and a thorough understanding of the installation procedures. The upgrade addresses limitations of the original generator, enhancing safety and operational capabilities, particularly during low-speed and nighttime conditions. The installer must be prepared to address potential discrepancies in existing wiring and fabricate a custom mounting bracket for the alternator.