PITOT/STATIC ANTI-ICE SYSTEM

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FAA Aviation Safety SPECIAL AIRWORTHINESS INFORMATION BULLETIN SUBJ: PITOT/STATIC ANTI-ICE SYSTEM SAIB: 2026-01 Date: January 8, 2026 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin advises owners and operators of The Boeing Company Model 737-200/-300/-400/-500 airplanes of the potential for air data probe heaters to remain powered while on ground.

At this time, the airworthiness concern is not an unsafe condition that would warrant airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR) part 39.

Background

After the incorporation of Boeing Alert Service Bulletin (SB) 737-30A1064, required in part by ADs 2019-09-01 and 2021-07-02, several operators have reported probe heaters remaining on when the heating system was expected to be off. Troubleshooting has revealed that probe heaters can occasionally remain on even after engine shutdown when coupled with a Thrust Reverser Sleeve Disagree fault indication on the Engine Accessory Unit (EAU). Maintenance personnel could potentially be at risk of burn injury when interacting with air data probes that are presumed to be unheated. The probable cause of the unexpected probe heater functioning is due to a shared electrical connection between the Engine Low Pressure Oil Switch and the EAU. This only affects airplanes that have incorporated SB 737-30A1064 and encounter a Thrust Reverser Sleeve Disagree fault.

To address this concern, Boeing has updated the Dispatch Deviation Guide (DDG) 78-01-01/78-01- 02 and Airplane Maintenance Manual (AMM) tasks to include Caution Notes or provide instructions to remove power to the probe heater system prior to starting the task. Boeing also plans to release a new SB with a prerequisite of SB 737-30A1064 that will give operators instruction to add 2 blocking diodes between the EAU and J18 Box to isolate the Engine Accessory Unit from the probe heat relays.

Recommendations

The FAA recommends that all owners and operators of affected airplanes incorporate the updated DDG and AMM tasks. The FAA also recommends reviewing and incorporating the new SB when it is released.

For additional guidance, refer to Boeing Fleet Team Digest, 737-FTD-30-22001, “Air Data Heating System May Not Turn Off Properly.”

For Further Information Contact

Joshua Baek, Aerospace Engineer, 2200 South 216th St., Des Moines, WA 98198; phone: (562) 627- 6725; e-mail: [email protected].