A vital piece of Honeywell technology, the 131-9 series Auxiliary Power Unit (APU), recently became the second from Honeywell’s family of APUs to surpass 100 million hours in service across more than 7,500 narrow-body aircraft around the world such as the Boeing 737, McDonnell Douglas MD-90, and Airbus A319, A320 and A321 models.

Honeywell invented the APU in the early 1950s and continues to be the market leader with more than 36,000 APUs currently in the field and more than 90,000 APUs produced for more than 150 applications in the commercial, business and military markets.

The 131-9 is the second Honeywell series of APUs to reach the 100 million hour milestone, with the first being the 85 Series, which was one of the earliest APUs to be installed on an aircraft. This second 100 million hour milestone continues Honeywell’s history of providing customers with reliable and easily maintained APUs that are proven to enhance operational efficiency for aircraft operators.

A flight begins and ends with the APU. From the moment a passenger walks on an air-conditioned plane on the tarmac, to the time when the plane parks at the gate, the APU engine is providing electrical air power to the aircraft for starting the main engines, enabling the air conditioning, running lighting and flight equipment, and more. The APU allows passengers to sit comfortably while awaiting takeoff.

The APU also provides primary or backup electrical power for environmental, cockpit and hydraulic systems during flight. In 2009, the Honeywell 131-9A APU on a US Airways A320 played a critical role in the emergency landing of US Airways Flight 1549 in New York’s Hudson River, ensuring the safety of 155 passengers onboard.

Honeywell is looking to the future to advance the 131-9 APU and continue to provide the best-in-class operational efficiency to customers. This next-generation APU will use new technologies to provide operators with up to 10 percent reduction in fuel burn, 25 percent reduction in nitrous oxide emissions and more than 30 percent increase in available electrical power.

In the future, Honeywell’s APUs will power more than just internal systems. For the Electric Green Taxiing System (EGTS), the APU will be tasked with powering the electric motors in the main landing gear, allowing an aircraft to push back autonomously and then taxi between gate and runway without engaging its main engines.

Jim Fusaro, Vice President of Marketing & Product Management, Honeywell Aerospace “Honeywell’s 131-9 model is the most reliable APU for single-aisle commercial aircraft in the world, with more than 100 million hours of in-service operation, and counting. The 131-9 model APU has proved to be highly reliable, fuel-efficient and quiet in the millions of hours of flight service recorded to date. We put our APUs through a number of extreme condition tests to ensure reliability for our customers, one of which requires our APUs to start at 41,000 feet and -100°F. High reliability and improved fuel efficiencies are the driving force for lowering our customers’ total cost of ownership”