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Starting Power: Honeywell APUs Stronger Than Ever At 75

Starting Power: Honeywell APUs Stronger Than Ever At 75

No one remembers who first came up with the idea of using a small gas turbine engine to power aircraft electrical systems and provide airflow for cabin pressurization, air conditioning and deicing. But there is no doubt that talented engineers at Honeywell legacy company Garrett AiResearch ran with the idea and created the first turbine-powered auxiliary power unit (APU) 75 years ago.

That first APU was the Garrett GTCP85, which is still flying today. The GTCP85 was a derivative of the company's original small gas turbine engine, the GTC43/44, which entered production in 1948 and in 1950 provided compressed air to start the main engines and drive the electrical systems on a Convair P5Y aircraft.

More than 500 GTC43/44 engines were eventually manufactured for various applications, including onboard and ground-based power generation. More importantly, the company’s first successful turbine gas engine gave flight to the APU, a flight critical component that makes flying safer, more efficient and more comfortable for millions of people every day.

APU Technology Continues to Advance

APU technology has come a long way over the last 75 years, but some things haven’t changed very much at all. APUs still generate electric power to run the air conditioning, lights, communications systems, cockpit displays and more while the aircraft is on the ground. When needed, an APU can restart a main engine or provide power to the cabin and cockpit during flight.

The most famous example is the “Miracle on the Hudson” landing by Capt. Sully Sullenberger in January 2009. After his main engines were disabled in a bird strike, Sully fired up the Honeywell 131-9A APU on his Airbus 320. It provided the power he needed to use his avionics and fly-by-wire flight controls to execute the one-shot river landing and save the lives of 155 passengers and crew members.

Of course, heroic landings are the exception. Honeywell APUs usually live a much quieter “life,” reliably providing secondary power on tens-of-thousands of flights worldwide every day.

We’ve had a lot of experience in the field and have produced more APUs than anyone else – more than 100,000 altogether – since that first one 75 years ago. 

Today’s APUs Are Better and Greener Than Ever

Today’s APUs are more powerful, reliable and fuel efficient than ever. They also leave a smaller environmental footprint because they can run on sustainable aviation fuel (SAF) blends. In addition, the world’s best selling APU, the 131-9 for Airbus A320 and Boeing 737 series aircraft, can operate in a high efficiency mode (HEM) to reduce fuel consumption and environmental impact.

The 131-9 APUs with the HEM diffuser upgrade installed deliver a 1-2% improvement in fuel efficiency, which can amount to as much as $9,000 savings per year. They also reduce carbon dioxide emissions by as much as 22 metric tons and need less maintenance.

Our latest APUs, like the HGT1700 that flies on the Airbus A350, truly represent the state of the art and are much more powerful, efficient and reliable than previous generations of secondary power systems. The HGT1700 features variable speed capability to increase starting power while lowering specific fuel consumption by 6-10%.

Over the last 75 years we have seen a constant increase in the demand for power on all types of aircraft. This trend will likely continue as aircraft become more connected, electric and autonomous. With this in mind, Honeywell is already working on new secondary-power solutions that will meet the needs of the next generation of aircraft for APUs that are even more powerful, reliable and fuel efficient than the ones we have today.

To view our Auxiliary Power Unit Portfolio click below
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