The Anonymous Widower

Airbus To Trial In-flight Auxiliary Power Entirely Generated By Hydrogen

The title of this post, is the same as that of this press release from Airbus.

Airbus UpNext has launched a new demonstrator programme to explore, on the ground and in flight, a new architecture for the generation of non propulsive energy through the use of hydrogen fuel cells.

On conventional airliners, the APU (Auxiliary Power Unit), a small additional engine that runs on traditional jet fuel, provides together with the engines the energy required to power a number of non-propulsive aircraft functions, such as air conditioning, onboard lighting and electric power for avionics. With this new technology demonstrator, led from its facilities in Spain, Airbus UpNext will replace the actual APU of an A330 with a hydrogen fuel cell system that will generate electricity. Known as HyPower, the hydrogen fuel cell demonstrator also aims to reduce the emissions of CO2, nitrogen oxides (NOx) and noise levels associated with a traditional APU.

New design features and integration techniques will also contribute to maturing the safety and operations of future hydrogen-powered aircraft and will demonstrate the stable operation of a fuel cell in-flight, including its restart.

This Airbus infographic describes the system.

This looks to be a well-thought out project and I suspect Airbus will learn a lot about hydrogen and how to use it.

I have some thoughts.

The Noise Factor

Reduction of noise is mentioned in both the text and the infographic, so it must be important.

Years ago, I remember a take-off from St. Lucia, where on the previous day, there had been an engine failure on the flight from London. This meant we were treated to the view of a rare site of a five-engined Jumbo Jet, as the next day’s flight brought in a spare engine on the spare mounting under the wing. Engineers then worked all night to put this engine on the previous day’s stricken plane, whilst we had an extra night in the Carribean.

When it eventually came to leaving, we were on the absolutely crammed-full rescue plane, which was an almost new 747-300.

I remember the plane being positioned at the very Western end of the runway and we waited a long time before take-off. From our position towards the rear of the plane, I couldn’t see if they topped up the fuel tanks but they may have done. The pilot then gave us the good news, that we would be going to Heathrow without the usual intermediate stop at Barbados to take on fuel.

We had no problems, but I suspect the airport’s neighbours on the island didn’t like the screaming noise of the APU (Auxiliary Power Unit) disturbing the peace, whilst we waited for take-off.

A hydrogen fuel cell-powered APU could have advantages in some take-offs from perhaps smaller airports. The plane would be towed into position for take-off by a battery-electric aircraft tug, with all aircraft systems running on the hydrogen-powered APU. When everything was ready, the first engine would be started by the power from the APU and then after all engines were started and everything was ready, the plane would take off.

It looks to me, that a hydrogen-powered APU and a zero-carbon aircraft tug, could work together to reduce pre-take off pollution, carbon-dioxide emissions and noise at airports.

The Inflight Restart

Two air incidents, illustrate the need for an inflight restart of the APU.

The Wikipedia entry for the flight describes the crash like this.

British Airways Flight 38 was a scheduled international passenger flight from Beijing Capital International Airport in Beijing, China, to London Heathrow Airport in London, United Kingdom, an 8,100-kilometre (4,400 nmi; 5,000 mi) trip. On 17 January 2008, the Boeing 777-200ER aircraft operating the flight crashed just short of the runway while landing at Heathrow. No fatalities occurred; of the 152 people on board, 47 sustained injuries, one serious. It was the first time in the aircraft type’s history that a Boeing 777 was declared a hull loss, and subsequently written off.

Wikipedia gives this as the cause of the accident.

Ice crystals in the jet fuel were blamed as the cause of the accident, clogging the fuel/oil heat exchanger (FOHE) of each engine. This restricted fuel flow to the engines when thrust was demanded during the final approach to Heathrow.

Suppose this problem had occurred earlier and shut the engines down in the middle of Russia. At the 40,000 feet, they were flying, they could have probably been able to glide into the nearest suitable airport and land without main engine power. But the APU would have been needed to power the aircraft’s systems like instruments and air-conditioning.

One of my favourite books is All Four Engines Have Failed by Betty Toothill, who was a passenger on BA 009 on the 24th June 1982.

The Wikipedia entry of the flight starts like this.

British Airways Flight 009, sometimes referred to by its callsign Speedbird 9 or as the Jakarta incident, was a scheduled British Airways flight from London Heathrow to Auckland, with stops in Bombay, Kuala Lumpur, Perth, and Melbourne.

On 24 June 1982, the route was flown by the City of Edinburgh, a Boeing 747-200 registered as G-BDXH. The aircraft flew into a cloud of volcanic ash thrown up by the eruption of Mount Galunggung around 110 miles (180 km) south-east of Jakarta, Indonesia, resulting in the failure of all four engines. Partly because the event occurred at night, obscuring the cloud, the reason for the failure was not immediately apparent to the crew or air traffic control. The aircraft was diverted to Jakarta in the hope that enough engines could be restarted to allow it to land there. The aircraft glided out of the ash cloud, and all engines were restarted (although one failed again soon after), allowing the aircraft to land safely at the Halim Perdanakusuma Airport in Jakarta.

In this incident, the APU would have been needed to start the engines.

These incidents show how important the APU is to safe flying.

Some might even argue that a hydrogen fuel cell-powered APU running on its own independent hydrogen supply would be preferable than an APU based on a small gas turbine using the same fuel as the main engines.

June 22, 2023 - Posted by AnonW | Hydrogen, Transport/Travel | Airbus, Boeing 777, Hydrogen-Powered Aircraft, Research