Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NM-07-36
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.