Emergency Diesel Generators for Airports: Loads, Transfer and Testing

Airfield lighting and navigation aids

Runway, approach and taxiway lighting, along with instrument landing systems and other navigation aids, are among the most critical loads at any airport. Aviation standards such as ICAO Annex 14 and national civil aviation rules set requirements for secondary power and the maximum time allowed to switch over, which depend on the type of runway and approach.

Meeting those times often requires generators that run in parallel with the utility during low-visibility operations, or uninterruptible supplies for the most sensitive equipment, rather than relying on a cold start. The airfield lighting design and the generator plant must be designed together.

Air traffic services and communications

Control towers, approach control, radar, radio and data links need continuous power. These systems usually sit on uninterruptible power supplies backed by dedicated emergency generators, often with full redundancy so that one generator can be out of service without loss of cover.

Because air traffic services may be run by a separate authority, agree early who owns, operates and tests these generators and how their alarms reach the people responsible.

Terminal life safety and passenger systems

Terminals need emergency lighting, fire alarm and voice evacuation, smoke control fans, fire pumps, lifts for evacuation and security screening systems. Building and fire codes define many of these loads and the time within which they must be restored. Beyond the life safety tier, owners often add check-in, baggage and retail systems to keep the airport working through an outage.

Separate the life safety loads from optional business loads in the distribution design. That makes it easier to prove compliance and to shed optional loads if the generators approach their limit.

Baggage, fuel farms and airside services

Baggage handling systems are large motor loads with complex controls. Fuel farms and hydrant systems need pumps, valves and leak detection to stay powered for safe operation. Ground power for aircraft, apron lighting and de-icing facilities may also be on the emergency list depending on the airport.

Each of these areas may be some distance from the main substation, which shapes the decision between central and distributed generation.

Central plant or distributed generators

Large airports often use several generator plants distributed around the site: one for the airfield lighting vault, one for the tower, one or more for the terminal and others for remote facilities. Distributed plants reduce cable runs and avoid a single point of failure. A central plant with a medium voltage ring can be easier to maintain and fuel.

The right answer depends on site layout and ownership boundaries. Our article on installing emergency generators covers foundations, exhaust and cooling, which apply to each plant room.

Fuel storage and runtime

Airports usually require enough on-site fuel to run emergency generators for an extended outage, with a resupply plan that does not depend on the same roads or systems that may be disrupted. Fuel must be kept clean, rotated and tested, especially in tanks serving sets that run only for tests.

Runtime targets should be set with the airport’s emergency plan, not copied from another building type. Our page on how long a diesel generator can run explains the limits that apply during long outages.

Testing without disrupting operations

Regular testing is essential, but switching an airport’s airfield lighting onto generator power during busy hours carries operational risk. Plan tests in agreed windows, coordinate with air traffic services and use load banks where transferring live loads is impractical. Annual full transfer tests prove the whole chain from utility failure to restored supply.

Every test should check switchover times against the required limits, not only whether the generator started. A generator that starts but restores airfield lighting too slowly still fails its purpose.

Remote facilities across the airfield

Airports include many small facilities far from the terminal: localiser and glide path shelters, remote radar sites, perimeter security posts and pumping stations. Each may have its own small generator or battery system. Include them in the emergency power register, give each a test and maintenance schedule and monitor them remotely where possible, because a fault at a remote navigation aid can be as disruptive as one in the main terminal.

Records, inspections and maintenance

Aviation authorities, insurers and fire officials may all ask for evidence that emergency power is maintained. Keep records of each test, the measured transfer time, any faults found and the corrective action. Our article on emergency generator test records shows what a good record contains.

Maintenance on airport generators should be scheduled with operations, and critical spares such as batteries, chargers and control parts kept on site. A single missed fault on a tower generator can affect every flight in the region.