Piper Aircraft - PA-28, PA-32, PA-38-112 Diode Cooler Assembly

On July 23, 2020, a 1981 PA-28RT-201T Arrow IV experienced an in-flight fire near Basel-Mulhouse Airport, France. During cruise, the ammeter indicated an abnormally high alternator output of 70 amps—well above the typical 20–30-amp range—suggesting an electrical overload condition. The pilot and passengers detected an electrical odor, and the pilot declared an emergency. After landing, smoke and flames entered the cabin from the luggage compartment. The event was traced to an electrical failure within the Diode Cooler Assembly. The investigation also noted that the pilot did not follow the Aircraft Flight Manual (AFM) procedures for electrical overloads or suspected in-flight fires, which normally call for reducing electrical load, isolating the faulty system, and preparing to use the onboard fire extinguisher. As a general safety reminder, pilots are encouraged to review AFM emergency procedures related to electrical malfunctions and in-flight fire response.

Piper Aircraft, Inc. subsequently issued Service Bulletin (SB) 1428, Periodic Inspection of Diode Cooler Assembly, applicable to various PA-28, PA-32, and the PA-38-112 models equipped with this component. The SB calls for a detailed inspection of the diode cooler assembly and its installation. Mechanics performing this inspection would typically look for signs of heat distress, loose or damaged wiring, improper mounting, degraded insulation, and any evidence of arcing or component deterioration that could lead to electrical failure.

This notice highlights the importance of complying with SB 1428 and encourages pilots to remain familiar with AFM procedures for handling electrical anomalies and potential in-flight fire indications.

https://s3.amazonaws.com/pipercrm/Solution/21128/SB_1428.pdf

If you have any questions, please contact:

Bryan Long

Electrical Systems Aerospace Engineer SME – AIR 756

Compliance & Airworthiness Division

Aircraft Certification Service (AIR), AVS/FAA

Mailing Address: 1701 Columbia Ave, College Park, GA 30337

Email Address: [email protected]

Office Phone: (404) 474-5578