Honeywell Upgrades Aircraft APUs to Lower Fuel Consumption and CO2 Emissions

Advanced-technology company Honeywell 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 latest 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.

“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 realise as much as US$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 US$315,000 for each avoided service visit.”