FAA Aviation Mechanic Airframe (AMA)Airframe Electrical and InstrumentsHard
An aircraft's electrical system is designed with an essential bus and a non-essential bus, connected through an isolation relay. During single-engine or single-generator operation, non-essential loads are automatically or manually removed to conserve remaining electrical capacity. What is this design and procedure called?
- ASplit bus system with load shedding
- BRing bus distribution system
- CDual-fed bus tie system
- DParallel generator paralleling system
Show answer & explanationAnswer & explanation
Correct answer: A. Split bus system with load shedding
A split bus (isolated bus) electrical system separates essential and non-essential loads onto different buses connected by an isolation relay. If generating capacity is reduced, load shedding removes non-essential equipment to ensure critical systems remain powered.
Why the other options are wrong
- B. Ring bus systems are used in ground power distribution, not typical aircraft essential/non-essential bus design.
- C. A bus tie connects two buses together for redundancy, but doesn't describe the essential/non-essential separation.
- D. Paralleling refers to synchronizing multiple AC generators to share a load, not bus isolation.
Split Bus System / Load Shedding
An electrical architecture separating essential and non-essential buses via an isolation relay; during reduced generating capacity, non-essential loads are shed to protect essential equipment.
- Essential bus powers flight-critical equipment
- Non-essential bus can be isolated during generator failure
- Load shedding may be automatic or manual to conserve battery/generator capacity
Memory trick: Split the buses, shed the extras, save the essentials.