Revised Special Airworthiness Information Bulletin Focuses On Engine Cooling

The FAA has issued a revised SAIB for aircraft with Bombardier-Rotax (Rotax) 912 A, 912 F, 912 S, and 914 F series reciprocating engines for a possible problem with the liquid cooling system. These engines are installed on, but not limited to, Aeromot-Industria Mecanicao Metalurgica AMT-200, AMT-200S, and AMT-300; Aquila Technische Entwicklungen GmbH AT01; Diamond Aircraft Industries (Austria and Canada) DA20-A1, HK36 R, HK36 TC, HK36 TS, HK36 TTC, HK36 TTC-ECO, and HK36 TTS; Iniziative Industriali Italiane 650 TC, 650 TCN, 650 TCS, and 650 TCNS; and Stemme GmbH S10-VT aircraft. They may also be installed on amateur-built and light-sport aircraft.

The European Aviation Safety Agency (EASA) has advised the FAA of possible loss of coolant and engine overheating on Rotax 912 and 914 series engines. Based on these findings, EASA published AD 2007-0155, dated May 29, 2007, that requires use of a waterless type coolant if the engine coolant exit temperature will exceed 120° centigrade (C). Use of waterless coolant may not apply to all Rotax 912 and 914 series engines because coolant exit temperatures are affected by the aircraft installation and operating  conditions. The maximum cylinder head temperature limits approved for these engines remain the same.

If a conventional ethylene-glycol/water coolant is used, and engine coolant exit temperatures exceed 120° C, loss of coolant, engine overheating, knocking, and engine damage can occur, which could result in an in-flight shutdown. The coolant exit temperature should be monitored to prevent engine overheating when using conventional coolant. Engine overheating can be prevented by monitoring cylinder head temperature if an appropriate correlation is established between coolant exit temperature and cylinder head temperature.

Rotax 912S

The FAA recommends following the coolant usage information provided in Rotax service bulletins SB-912-043 Revision 2, dated November 10, 2006, and in SB-914-029 Revision 2, dated November 10, 2006, and the applicable Rotax 912 and 914 installation manuals and operator’s manuals. They further recommend that pilots and owners comply with the coolant usage information and cooling system temperature limits defined by the manufacturer of your aircraft because of installation effects on engine cylinder head and coolant exit temperatures.

FMI: www.faa.gov