Notes 'Possible Service Difficulties' Including In-Flight Engine Failures

EASA has issued a safety bulletin for Rotax 912 and 914 engines installed on a variety of aircraft for exceedances of approved engine coolant temperature limits due to installation of an unapproved design.

According to the bulletin, the  reported conditions are the result of an insufficiently communicated engine design change which altered the engine/aircraft interfaces by substituting the previous cylinder head temperature (CHT) measurement (limit temperature 135°C/150°C) with a coolant temperature (CT) measurement (limit temperature 120°C).

EASA says that If affected engines or cylinder heads have been or are installed during production or maintenance without concurrent installation of an adequate aircraft TC/STC holder approved modification, thus altering the previous aircraft CHT indicator/indicator markings/aircraft flight manual limitations, then coolant temperature with a maximum engine operating limit of 120°C (valid for engines operated with water diluted glycol coolant) is displayed on a CHT indicator with a typical limit marking (red radial/range) of more than 120°C. The pilot is therefore not able to identify coolant limit exceedances, subsequent loss of coolant and impending engine failure during flight.

Also, for engines operated with approved waterless coolant, installation of the affected engines needs to be accompanied by adequate aircraft TC/STC holder approved modifications to assure safe aircraft operation.

Installation of affected engines and spare parts without concurrent incorporation of aircraft TC/STC holder approved modifications, even if unintended and unnoticed by production or maintenance, constitutes an unapproved aircraft modification.

Investigations are ongoing at BRP-Powertrain and with aircraft TC/STC holders to identify the extent of unapproved installations and to evaluate potential mandatory airworthiness actions.

(Image provided by EASA)

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