Multiengine aircraft are typically thought of as being safer than singles because they have an extra engine. But this issue is often debated. Ask a group of pilots whether two engines are better than one and you may hear some use the phrase “the good engine will take you to the scene of the crash,” while others maintain that continual training on engine-out procedures is essential to realizing the safety of engine redundancy.
While a second powerplant is the most obvious advantage of flying a Baron, there is more to redundancy than just the engine. One such example is the electrical system. Some single-engine aircraft are equipped with redundant electrical systems, but as discussed in my November 2016 BPPP column, even an aircraft such as the G36 Bonanza can’t provide total redundancy in the case of a main alternator failure. The availability of a second engine to drive a full-size, second alternator, and room and weight-carrying capability to host a full-size second battery, permits a fully redundant electrical system in the G58 Baron.
G58 Electrical System
The G58 electrical system consists of two independent systems, each powered by its own 13 amp-hour battery and 100-amp alternator. The alternators are gear driven and attached to each engine ahead of the right, forward cylinder. Each alternator provides power to its respective buss, with power equipment that generally have a “left” or “right” oriented purpose. For example, the left buss normally powers items such as the left engine’s fuel boost pump or the left engine’s starter relay. The HOT BATTERY BUSS is powered by the right electrical system and generally consists of equipment that requires power while the aircraft is shut down, such as the courtesy lights and the clock. There are many systems that don’t have a left or right designation, and there are no cockpit indications that show which piece of equipment is powered by which buss. So it would be wise to study Section 7 of the Pilots Operating Handbook, where you will see charts illustrating equipment and their relationship to each buss.
Busses Tied Relay
The G58 handles electrical loads and routing of power differently than older Barons when there is a malfunction or alternator failure. In the event of an alternator failure, the operating alternator is able to support the load of the whole electrical system, although this does not happen automatically. If one of the alternators, voltage regulators, or current limiters fail, or any number of abnormal or emergency conditions exists where one of the busses is affected, that alternator must be manually switched to the Buss Tied position to allow power to flow from the other alternator. If you have a situation that requires a shutdown of the left engine, for example, you will need to move the left alternator switch to the Buss Tied position. This enables current to flow from the right alternator to the left buss. The buss tie relay will engage and the left and right busses will connect together so the remaining alternator can power the entire electrical system. A BUSS TIE indicator will illuminate on the G1000 panel indicating this condition.
This process is quite different than the G36 Bonanza’s function. As I wrote in the November issue, it’s normal and expected to see the BUSS TIE annunciator on the ground in a G36, but this would indicate a system failure in a G58. In pre-G58 Barons with alternators, the left and right alternators are tied together to the same buss. If there is an alternator failure in pre-G58 Barons, no action is required by the pilot to maintain electrical continuity. As already noted, in a G58 the pilot must manually tie the busses if one alternator fails. There is one scenario in which the buss tie relay will engage automatically: application of external power to the aircraft while on the ground. Once external power is applied, the buss tie relay connects both left and right systems together so that power can be delivered to both buses.
Failure Scenarios
The most obvious situation requiring the alternator to be switched to the buss tie position is engine failure. The windmilling propeller will continue to allow the alternator to produce electrical power, but once the engine is secured and the propeller feathered, the alternator should be switched to the buss tie position so power can be made available by the operating alternator. Other situations that may require the busses to be tied are:
- Precautionary shutdown of the electrical system (erratic voltage or amperage indications from the alternator)
- A voltage regulator shutdown (overvoltage or undervoltage)
- The alternator not delivering enough amperage
Summary
The G58 Baron can provide total redundancy to the various electrical busses if there is an alternator failure or precautionary shut down. When transitioning to the G58 from an older Baron or a Bonanza, it is imperative for the pilot to have a full understanding of the electrical system. It is also important to cover the differences between the G58 and the other aircraft a pilot is transitioning from. Exploring various failure scenarios with your instructor will help identify appropriate reactions to various situations. Make sure you find an instructor that is well versed in the systems of the G58 Baron. There are many BPPP instructors that are qualified in the G58, and it will be time well spent.