Grounding plate and bonding jumper to improve electrical bonds between pitot probes and airplane structure

FAA Aircraft Certification Service SPECIAL AIRWORTHINESS INFORMATION BULLETIN http://www.faa.gov/aircraft/safety/alerts/SAIB

SAIB: NM-07-36 Date: June 8, 2007 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) advises you, owners and operators of The Boeing Company Model 737-100, -200, -300, -400, and, -500 airplanes, to install a grounding plate and bonding jumper to improve electrical bonds between pitot probes and airplane structure.

Background

This SAIB is prompted by an operator report of fire and smoke from the flight deck lower left hand sidewall during approach. Investigation showed the probe heater had shorted to its case, and that a high bond resistance between probe and airplane let current flow through the flexible hose by way of the metal spiral hose reinforcement. Enough heat was generated to cause burning of the hose.

Recommendations

We recommend that you incorporate Boeing Special Attention Service Bulletin (SASB) 737-34-1710 Revision 2, dated August 31, 2006. This SASB provides instructions for installation of a ground plate, jumper, and ground stud, and replacement of alloy steel screws with CRES screws at each pitot probe installation.

For Further Information Contact

Paul Feider, Aerospace Engineer, FAA Seattle Aircraft Certification Office, 1601 Lind Avenue, SW, Renton, WA 98055-4056; phone: (425) 917-6467; fax: (425) 917-6590; email: [email protected]

For Service Bulletin Information Contact

Boeing Company at P.O. Box 3707, Seattle, WA 98124 or through the following website: https://www.myboeingfleet.com/boldweb/index.bhtml