73-006 - Robinson R44 II helicopters - Fuel System Electric Fuel Pump and Pressure Relief Valve (PRV) (Revision 2)

ATA Chapter: 73

Subject:

This Continuing Airworthiness Notice (CAN) at Revision 2 is revised to clarify the component maintenance requirements below and add a recommendation to replace parts which have reached the manufacturers recommended replacement interval, and inform aircraft operators and maintainers that Robinson Helicopters Corporation (RHC) have revised the component maintenance requirements in Chapter 1.102 of the R44 Series Maintenance Manual dated December 2021. Refer: https://robinsonheli.com/r44-maint-manual/ The revised component maintenance requirements: Electric Fuel Pump P/N D743-1, -2, -3 and -4 must be replaced with a new P/N D743-3 pump at 2200 hours TTIS; and Fuel Pressure Relief Valve P/N D321-1 must be replaced with a new or overhauled part at 12 years, or before 2200 hours TTIS.

Applicability:

Robinson R44 II helicopters fitted with the Lycoming IO-540 engine.

Purpose:

This Continuing Airworthiness Notice (CAN) at Revision 2 is revised to clarify the component maintenance requirements below and add a recommendation to replace parts which have reached the manufacturers recommended replacement interval, and inform aircraft operators and maintainers that Robinson Helicopters Corporation (RHC) have revised the component maintenance requirements in Chapter 1.102 of the R44 Series Maintenance Manual dated December 2021. Refer: https://robinsonheli.com/r44-maint-manual/(external link)

The revised component maintenance requirements include:

• Electric Fuel Pump P/N D743-1, -2, -3 and -4 must be replaced with a new P/N D743-3 pump at 2200 hours TTIS.
• Fuel Pressure Relief Valve P/N D321-1 must be replaced with a new or overhauled part at 12 years, or before 2200 hours TTIS.

Background:

CAN 73-006 originally issued in August 2021 highlighted a CAA finding with the Fuel Pressure Relief Valve (PRV) fitted on a Robinson R44 II involved in an accident on 12 June 2021.

The PRV on that aircraft was found to be bypassing an excessive amount of fuel at a much lower pressure than specified.

The CAA is aware of another Robinson R44 II helicopter which the pilot could not start. The PRV on this aircraft was also found bypassing an excessive amount of fuel, due to an internal leak.

RHC provide a method for checking the PRV in situation. Refer to page 12.27 in the RHC R44 Maintenance Manual. This check is not included as a scheduled maintenance activity in the RHC Maintenance Schedule.

The failure of the PRV is not considered likely to cause an engine failure. It appears that a combination of a failed PRV and a failed electric fuel pump could result in a loss of engine performance. For that reason, CAA are advising operators to ensure that those components are replaced at the manufacturers recommended replacement interval.

Recommendation:

CAA recommend that R44 operators assess their aircraft records and ensure that they meet the maintenance requirements in the revised RHC R44 Maintenance Manual. Components which have exceeded their manufacturers recommended replacement interval should be replaced as soon as practicable.

The CAA would like to know if operators have any issues related to their fuel systems, including if they have any findings from PRV inspections (RHC R44 Maintenance Manual). Please report findings to the CAA by completing a CA005 Defect Report form. Please provide as much engineering detail as possible. This will enable us to determine the extent of any issue with the PRVs and the R44 fuel system. The form can be obtained from https://www.aviation.govt.nz/assets/forms/CA005D_Form.pdf The completed form can be emailed to the CAA at ca005@caa.govt.nz