Piper PA-42 Cheyenne 400 — Systems Description

This document is a service letter issued by Nichols Airborne Division of Parker Hannifin Corporation, detailing a mandatory upgrade for the Nichols Airborne Model 1H75-6 Pressure Regulator. The letter is applicable to all pressure regulators manufactured between January 1989 and July 2002, specifically those installed on the Piper PA-42-720 and PA-42-1000 aircraft, including the Cheyenne 400. The letter outlines compliance requirements, inspection procedures, and a Pro-Rata Upgrade Program for affected units. The document emphasizes the importance of maintaining the minimum de-ice pressure of 16 PSI, which may not be achieved by certain regulators under specific conditions. Pilots and maintenance personnel are advised to inspect and replace the affected regulators during the next scheduled maintenance inspection or after 50 hours of operation, whichever comes first.

• Mandatory inspection of Nichols Airborne Model 1H75-6 Pressure Regulators with serial numbers between 1AE and 7AV.
• Minimum de-ice pressure requirement is 16 PSI; some regulators may not maintain this under certain conditions.
• Inspection must occur during the next scheduled maintenance or after 50 hours of operation.
• Outright list price for the Model 1H75-6 is $2,713 with a core credit of $814.
• Discounted upgrade prices are available based on the serial number of the removed regulator.