Engine cooling hoses

DAILY INSPECTION ENGINE COOLING HOSES

Owners/Operators, Pilots and Maintenance personnel should make themselves aware that It is a requirement under RAAus Airworthiness Notice AN270810-1 that all engine cooling hoses are inspected at each daily inspection.

If this means taking the cowls off to perform this inspection then please do so. Loss of coolant whilst in-flight can be a hazard to flight safety.

RAAus Airworthiness Notices are MANDATORY and are available on-line via the Members Portal under the “Maintenance” menu. We encourage everyone to review them all to determine if they affect you, your aircraft or your operation.

Recently, during the 3rd Pre-flight inspection of the day, a student identified a coolant leak from the #4 Cylinder head, upper coolant hose mating inlet fitting. The o-ring was replaced and an EGR carried out with no leak evident.

Following a short test flight, the fitting was again inspected and found to be weeping. The seat of the cylinder head that houses the o-ring was inspected with a magnifier and a crack was found on the inner shoulder.

The aircraft was removed from service and a serviceable cylinder head assembly was obtained from Bert Flood Imports. Cylinder Head replaced IAW the Rotax Maintenance manual and test flown serviceable. So what went wrong??

Hard to say but possibly in the history of this aircraft, we think that someone may have removed the o-ring with a screwdriver or some

other metal device which could have scored the shoulder and then over time the crack has appeared.

What can we do to prevent things like this in the future? Always use plastic or some other soft tooling when working with mating faces. The flight school operating the aircraft has now adopted a standard practice that the cowlings are to be removed adequately to inspect the cooling system component prior to EACH FLIGHT.

Remember, the aircraft was inspected prior to the first flight of the day as required by the RAAus AN, but the defect was detected prior to the 3rd flight of the day. The school had scheduled another 3 flights following the discovery which could have continued unnoticed. Worst case was complete loss of coolant and possible engine failure. Most cowls are designed for easy removal so be safe and take the time to ensure all systems are functioning correctly before each and every flight. FLY SAFE - HAVE FUN

Article supplied by Paul Strike – Flight Safety Solutions