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Honeywell Reminds 737 NG And MAX Operators To Order NGS Oxygen Sensors

Honeywell Reminds 737 NG And MAX Operators to Order NGS Oxygen Sensors

Boeing 737 NG and MAX operators will need to inspect or replace the oxygen sensor that is key component of the aircraft’s nitrogen generation system (NGS) by July 19, 2024, according to an airworthiness directive (AD) issued by the FAA.

AD 2021-11-24 requires operators to check or replace the oxygen sensor, PN 3522W000-001 or -002:

  • Within 18,000 flight hours after the original airworthiness certificate or the original export certificate of airworthiness was issued; or
  • Within 18,000 flight hours after the most recent replacement was performed; or
  • Within 36 months of the effective date, whichever is later. The AD was issued July 20, 2021, which means the 36 months is up in July. 


To avoid aircraft downtime, operators will need to order the new parts as soon as possible so the new sensors are ready to be installed when the old sensors are removed. Operators with existing contracts with Honeywell for the part should contact their Honeywell representative for more information. Others will need to reach out to Killick Aerospace, which has been Honeywell’s exclusive distributor for NGS components since 2020. Customers located in mainland China should reach out to Topcast Aviation Supplies Co.

Killick supports the sensor (part number 3522W000-002) from its global distribution centers in Dallas, Dublin and Singapore. For more information, operators should email the appropriate Killick customer service representative. 

Topcast (for customers in mainland China)

Developed by Honeywell, the NGS is a fuel tank inerting system that has all-but eliminated fuel tank explosions in commercial aircraft. It uses an air separation module (ASM) to separate oxygen from bleed air from the main engines to produce nitrogen-enriched air, which is then delivered to the fuel tank. This creates an in-tank atmosphere too low in oxygen to enable any fuel vapor to ignite. 

Danielle Richeti
Channel Customer Marketing Manager