A helicopter maintenance technician reported that the engine had abnormally high cht at normal cruis...

Narrative:

The owner reported abnormally high cht at normal cruise power settings. During investigation; we found binding in the fuel servo that prevented the mixture control arm from reaching the full rich stop. Further investigation revealed a very fine; ferrous sediment throughout the fuel system (in tanks; at the strainer; etc.). A fuel servo teardown at [another maintenance facility] indicated that the same ferrous sediment was the likely cause of the binding in the servo. We believe we have ruled out any possible on-aircraft sources of the sediment (e.g.; boost pump vanes; etc.). We believe that the helicopter was fueled sometime since its last annual inspection (march 2018) with a load of fuel that contained the sediment. We've notified the owner of the situation and have initiated appropriate maintenance and repair action on the helicopter. The owner is aware that we are filing this report so that he can assist with information; if needed.

Original NASA ASRS Text

Title: A helicopter Maintenance Technician reported that the engine had abnormally high CHT at normal cruise power settings most likely due to fuel contamination.

Narrative: The owner reported abnormally high CHT at normal cruise power settings. During investigation; we found binding in the fuel servo that prevented the mixture control arm from reaching the full rich stop. Further investigation revealed a very fine; ferrous sediment throughout the fuel system (in tanks; at the strainer; etc.). A fuel servo teardown at [another maintenance facility] indicated that the same ferrous sediment was the likely cause of the binding in the servo. We believe we have ruled out any possible on-aircraft sources of the sediment (e.g.; boost pump vanes; etc.). We believe that the helicopter was fueled sometime since its last annual inspection (March 2018) with a load of fuel that contained the sediment. We've notified the owner of the situation and have initiated appropriate maintenance and repair action on the helicopter. The owner is aware that we are filing this report so that he can assist with information; if needed.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1550467
Time
Date	201805
Local Time Of Day	0601-1200
Aircraft 1
Make Model Name	Robinson R44
Flight Phase	Parked
Component
Aircraft Component	Powerplant Fuel Distribution
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant
Experience	Maintenance Technician 4
Events
Anomaly	Aircraft Equipment Problem Less Severe Inflight Event / Encounter Fuel Issue

A helicopter maintenance technician reported that the engine had abnormally high cht at normal cruise power settings most likely due to fuel contamination.