OT Safety Bulletin

Dealing with failure

ATS systems have multiple layers of protection to ensure that power is always available. Normally systems will operate on mains power, backed-up by a generator with a final back-up of battery power. Transfer from mains to generator or battery power is normally seamless using Uninterrupted Power Supplies (UPS) connected to critical equipment.

However, experience has shown that sometimes both the primary and secondary means of power can both fail leaving the ATS systems just running on battery power.

Battery power can only sustain ATS equipment for approximately 20 – 45 minutes, depending on the load. So, when batteries are being used as the sole source of power a controlled shut-down of air traffic services should commence.

All ATS providers should review their operational procedures to ensure that:

• A risk assessment has been completed that considers the impact of ATS multiple power failures;

• The maximum time on battery power for each piece of equipment is known;

• This information is used to establish the time after a primary and secondary power failure by which the ATS shutdown must have been achieved;
• The process to be followed to in the event of such a failure; and
• The process to be followed once power is restored.

It is also worth checking up on:

• When was your generator last checked?
• When did it last take the full load of your ATS systems and prove itself?