All Piper PA-34 Seneca aircraft fitted with an Oildyne hydraulic power pack.
This Continuing Airworthiness Notice (CAN) advises operators of Piper PA-34 Seneca aircraft fitted with an Oildyne hydraulic pump of an incident which resulted in the landing gear failing to extend.
This CAN is prompted by a landing gear malfunction involving a Piper PA-34-220T Seneca III aircraft due to failure of the hydraulic power pack . The emergency gear extension was used.Investigation revealed that the motor brushes on the Oildyne hydraulic gear pump were worn below limits
The Oildyne hydraulic gear pump is a sealed unit and does not allow the brushes to be inspected nor replaced in the field . These pumps are replaced upon condition/as required. Piper Aircraft requires operational checks of the Oildyne pump and the landing gear system at the inspection intervals specified in the current aircraft Service Manual and Programmed Inspection Report.
The Prestolite hydraulic gear pumps were originally used in the PA-34-220T Seneca III aircraft. These pumps allow the inspection and replacement of the brushes. However, the Prestolite pumps were replaced with the Oildyne hydraulic gear pump from 1989 because Prestolite no longer supplied hydraulic pumps for Piper aircraft.
This CAN alerts operators of all PA-34 Seneca aircraft fitted with Oildyne hydraulic gear pumps of the landing gear system operational checks and inspection intervals specified in the current aircraft Service Manual and Programmed Inspection Report. (Refer to the landing gear detailed inspection/operational check requirements and intervals specified in the Progressive Inspection of the Piper Programmed Inspection Report).
All of the PA-34-200T Seneca IIs were manufactured with Prestolite pumps as original equipment. However, the replacement with Oildyne hydraulic pumps was extended to all PA-34 aircraft when a replacement pump was required.
