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Honeywell Upgrade For Aircraft Auxiliary Power Unit Lowers Fuel Consumption And Co2 Emissions

Honeywell Upgrade For Aircraft Auxiliary Power Unit Lowers Fuel Consumption And Co2 Emissions

  • Improvements to the 131-9B APU enable more efficient operation and new savings for operators of Boeing 737 aircraft

PHOENIX, June 19, 2023 – Honeywell (NASDAQ: HON) has unveiled a new High-Efficiency Mode (HEM) upgrade for its 131-9B auxiliary power unit (APU) for Boeing 737 aircraft. HEM is enabled by an innovative and highly efficient diffuser, controlled by software that autonomously regulates airflow to the APU compressor section. The HEM capability upgrade is expected to provide fuel savings and efficiency as well as CO2 emissions savings of 1% to 2% (estimated reduction of 0.5 to 0.6 gallons per APU hour) and increase time-on-wing by up to 1,500 APU flight hours, lowering fuel and maintenance costs.

An APU is critical aircraft equipment that provides electrical power and air conditioning while the plane is on the ground to ensure increased passenger comfort. It also supplies the power source when a pilot is ready to start the main engines. The 131-9B is known for its reliability and lower maintenance costs over its entire life cycle.

“Globally, airlines are working to reduce their carbon footprint and every incremental step will help them achieve their net-zero carbon emissions targets,” said Heath Patrick, president, Americas Aftermarket, Honeywell Aerospace. “An airline with a fleet of 50 737s could realize as much as $450,000 in annual fuel savings and reduce its emissions by up to 1,100 metric tons of CO2, depending on operating conditions. A major airline carrier recognized a fuel savings of 2.46 percent from the use of the 131-9A auxiliary power unit. Additionally, increased time-on-wing can reduce maintenance costs by decreasing servicing events, providing average savings of $315,000 for each avoided service visit.”

The upgrade is intended for any aircraft already operating a 131-9B APU, including Boeing 737-600, 737-700, 737-800, 737-900 and 737 MAX models. It will be available to operators with 131-9B APUs in the second half of this year. This upgrade can be installed during any regularly scheduled maintenance event and does not require additional downtime to implement for newer 131-9B APUs (series 49 and above) delivered with the new diffuser, which enables an on-wing upgrade to HEM.

The HEM upgrade was previously introduced on the Airbus A320 Series aircraft in 2020 and is now installed on over 700 131-9A APUs.

Honeywell’s first APU took to the skies in 1950, and the company has built more than 100,000 since then. More than 36,000 APUs, including both fixed wing and rotary wing, are in service today across more than 150 regional, executive, commercial and military applications.


About Honeywell

Honeywell Aerospace products and services are found on virtually every commercial, defense and space aircraft. The Aerospace business unit builds aircraft engines, cockpit and cabin electronics, wireless connectivity systems, mechanical components and more. Its hardware and software solutions create more fuel-efficient aircraft, more direct and on-time flights and safer skies and airports. For more information, visit or follow us at @Honeywell_Aero.

Honeywell ( delivers industry-specific solutions that include aerospace products and services; control technologies for buildings and industry; and performance materials globally. Our technologies help aircraft, buildings, manufacturing plants, supply chains, and workers become more connected to make our world smarter, safer, and more sustainable. For more news and information on Honeywell, please visit

Ahjay Rai
Global Communications Lead

Ahjay leads communications for Honeywell Aerospace across Americas, Europe, Middle East, Africa and India.