Service Bulletin No. 671 A

DATE:

August 24, 2026

SUBJECT:

Fuel Pump Leak Inspection and Diaphragm Replacement, Hartzell Engine Tech (HET) Alert Service Bulletin No.233

MODELS AFFECTED:

All Lycoming engines using AN style fuel pumps manufactured by HET with P/N 063F-0001 diaphragms with a cure date of 02/25 through 02/26

TIME OF COMPLIANCE:

Before next flight

REASON FOR REVISION:

Revised language in Required Action. Added Tables 2, 3, and 4.