Aircraft power at the stand

posted on 22nd June 2018

With the two concerns of austerity and environmentalism becoming increasingly important at airports and other air installations, the need for and the use of ground power units (GPUs), auxiliary power units (APUs) and alternative power is changing. Buyers and operators are moving towards lower noise, lower emissions, lower fuel consumption, smart power conversion technology and alternative power such as fixed electrical ground power (FEGP).

The view from a gateway

Copenhagen Airports (CPH), which operates three terminals on Amager Island south of Copenhagen, says that it is the largest and busiest airport of the Nordic countries. In 2011, CPH it served a record 22.7 million passengers from its four terminals. However, mindful of the ongoing battle to attract new routes, CPH launched a strategy in March 2012 called ‘World Class Hub’, both to secure the airport’s current position and to enable future growth.

Part of that strategy and slotted into previous planning are better facilities for airlines, including ground power. CPH’s asset manager, Karsten Jørgensen, says that as part of the ongoing replacement of 28 passenger bridges at the airport between 2009 and 2013, the GPUs will be replaced at six to seven stands each year.

“If possible, the new GPU will be placed on the ground, so that the GPU and the passenger bridge can operate independently of each other,” Jørgensen informs. Aircraft stands without bridges are being replaced at the rate of around two to three per year as par of standard maintenance, he adds, with the GPUs at stands A25-A34 all having been changed over the last three years.

“The splitting of the bridge and the GPU will help to reduce the use of APUs,” he said. Furthermore, Jørgensen says: “Cable transmission from the GPU to the aircraft will be carried out through wells in the ground according to a request from the working environmental organisation.”

Going forward, he notes that converters will have to be replaced. “It is estimated that a converter has a lifespan of 12-15 years. Then it will be difficult to obtain spare parts,” he points out. AXA Power signed an agreement with CPH early in 2010 for the delivery of GPUs for the Copenhagen Airports Bridge Project.

Already the changes in power at the gateway’s stands have yielded results. CPH’s director technical service and operation, Claus Hincke, enthuses: “We have estimated that the GPU upgrade has led to an 80 per cent reduction in the use of mobile diesel GPUs; mobile diesel GPUs have a large carbon emission.” CPH seems to be comfortable with the route it is taking with aircraft power at the stand, and Hincke confirms that there are no plans for central GPU plants. CPH has previously attempted central facilities but has learned that decentralised systems give greater operational stability, he adds.

Move towards change

In order to comply with stricter regulations at the aircraft stand in the provision of power, operators and manufacturers are working towards smarter, more efficient and more environmentally friendly usage and deployment of power units, especially the use of APUs. A spokesperson for Virgin Atlantic explains: “Our aim is to reduce APU use to minimise fuel burn and limit any environmental impacts. We work closely with the airport authorities in the UK and comply with all regulations as well as having high-level discussions on infrastructure with all our airports around the world to ensure we have the facilities we need.

“Most recently, we have refocused our efforts to further reduce the time the APU is turned on before take-off and after landing, whilst balancing this with the need to keep the aircraft cool for customers on-board.”

New generations of GPUs can help achieve savings and compliance with regulations. However, there is a move towards FEGP at the stand, too. Virgin has said that in some airports, it is simply plugging aircraft into the mains electrical supply on the stand, thus replacing noisy APUs on the aircraft while allowing on-board interior lighting and air conditioning to function.

With regulations tightening towards the conditions of use of an aircraft’s tail-mounted jet engine, APUs major airports are adapting. London Heathrow International airport says that over 90 per cent of its stands are fitted with mains electricity connections – and similarly London Gatwick airport, as part of its noise reduction programme, is also using FEGP

Of course, just because it is mains power does not necessarily mean that it was generated in an environmentally friendly way but at least at its point of use, the aircraft stand, FEGP could make a substantial beneficial difference.

A manufacturer’s perspective: AXA Power

Denmark-based AXA Power ApS says that it launched its first 400Hz GPU in 1987, and product development continues to be an ongoing process; the company says that it is a leading manufacturer of power units and pre-conditioned air units on the world market.

The company’s modular designs include its patented ‘Plug and Play’ voltage compensation system launched in 2003, the AXA Power Coil introduced in 2005 and in 2009 what AXA calls the world’s first modular pre-conditioned air unit that AXA says allows for a quick change of cooling modules was launched.

Later this year, and available for sale in spring 2013, the company says that it will be introducing another series of 400Hz GPUs to the market that incorporate a better interface for integrating with building management systems (BMS) and that will also allow improved data monitoring and analysis with the option of being able to download data on to a USB stick.

Furthermore, AXA explains, the new GPUs will have a lower line current distortion at input, with the ability for the GPU to go below 5 per cent of on line current distortion. However, right now it is AXA’s power flagship model the 90kVA (kilo Volt Amperes) that it believes makes up around 50 per cent of the company’s annual production. These units have AXA’s Plug and Play system that AXA says ensures excellent voltage quality at the plug and also a feature that facilitates longer cable distances than other GPUs without Plug and Play.

The company considers this is a valuable feature, because the voltage tolerance at the aircraft tends to narrow down. “If you install a GPU greater than 90kVA with more outlets or a centralised system, you most often need to double or triple the cable, which is an expensive part,” remarks Vibeke Bo Hansen, AXA’s marketing manager. “To compensate for the voltage drop in the cable therefore, with those solutions you risk investing more in cables than in power.”  

Power Systems International

An Anglo-Swiss-owned company of the W & A Technology Group, UK-based Power Systems International (PSI) is a custom-engineered power conversion specialist. The company has a range of solid-state GPU 400Hz frequency converters that includes outdoor all-weather frequency changers such as the SD series that can be deployed on passenger loading bridges, hung under the walkway or near to where the aircraft is parked.

“As a point of use system they can be used exactly where the power is needed, particularly useful in medium-sized hangars,” declares a spokesperson for PSI, Katie de Silva. “The other angle is of course that they have none of the cons of a diesel set, no fuel costs or spillages or storage space, no fumes or pollution and far less noise, all advantages in this day and age.”

The company also says that the SD series can have an optional, built-in “NBT (narrow bandwidth technology) feature that allows the converters to synchronise with the onboard aircraft power system so that the lights, air-conditioning system and avionics continue operating during the change over from aircraft power to the external converter power”.

PSI says that a major benefit of a point of use frequency changer is efficiency, as the GPU need only be switched on when it is actually required; this means that the aircraft’s engines do not then need to run and nor does its onboard turbo generator auxiliary power unit (APU), thus saving fuel, reducing the environmental impact and maintenance on the APU, generators and batteries.

Market insights

PSI is adapting to new market requirements, as airports push forward with stricter environmental demands but economic constraints continue to be felt. “With the current economy pinching airport budgets and fixing long-term cuts, it is no surprise to us that we are experiencing an increase in enquiries for our 400Hz frequency converters and the market is moving away from diesel gen sets, with their increasingly expensive ongoing costs for fuel and fuel storage,” says de Silva.

In response, the company has expanded its product range for point of use systems. “This trend change, in providing point of use power, has provided us with the opportunity to expand our range of product features. We can offer the user wireless monitoring of power usage by the connected aircraft to meet the growing interest by the airport operators to identify their costs of providing ground power for aircraft,” de Silva reveals.

“While solid-state 400Hz GPUs have always been a key product area for us, this expansion of our range to include service pits and cable handling systems has ensured that we have been able to respond to the increased demand for comprehensive and project-specific requirements for convenient and innovative solutions and satisfy the wide range of enquiries we receive,” de Silva declares.

“Looking towards the future, we hope to continue to develop our GSE range to ensure we can respond to each and every unique application with a flexible approach. Additionally, we anticipate that the beginnings of an increased demand we are seeing for 400Hz/28VDC (volt direct current) combination-converters and 28VDC Helicopter Start Systems is going to continue to develop, along with the growing offshore market.”

Start Pac diversity

Las Vegas-based Start Pac has an extensive product line geared towards the lightweight and portable end of the market, including units suitable for remote locations and military applications. The company says that its GPUs are offered in either 24V or 28V models and its engineers are available for clients to make an informed choice.

Eve Storm, Start Pac’s vice president, says that the company’s best-selling GPU is “our 3328 with 175 amp power supply. This unit will start any electrically started engine and is used by operators like ERA in Alaska.”

Storm adds that the unit’s built-in 175 amp power supply is used for powering up aircraft systems, such as the onboard air conditioning. In terms of a newer GPU product, the company has just come out with “a micro GPU (the SUPER PAC), which provides engine starting as well as a 50 amp power supply. We released this unit in February and it is doing very well both domestically and globally; it comes in four different configurations, 2300QC, 6028QC, Li2700QC or Li2800QC.”


In tough economic times product innovation may not always be enough. “We have been very fortunate during the global economic crisis and have sustained our annual growth,” Storm considers. “Having doubled our advertising budget each year since 2009, the one thing we have noticed is that some customers spend a little more time gathering information before making purchasing decisions.

“While global economic health is still tenuous, we are very optimistic regarding the recovery of the international aviation industry.” The company says that it is environmentally aware and, she notes: “Our largest self-propelled GPU meets Tier IV EPA (Environmental Protection Agency) emissions standards consuming up to 75 per cent less fuel than traditional GPUs while running around 70 decibels.

Going forward, Start Pac is expanding “even more into military and new global markets. We have recognised industry gaps and have seven new very exciting patent-pending projects in the pipeline that span the automotive, aviation and locomotive industries, which will be in production during the next six months,” Storm concludes.


ITW, or Illinois Tool Works, is a large industrial corporation with nearly 100 years of history behind it. ITW produces a wide range of advanced industrial technology amongst a large number of decentralised business units located in more than 50 countries. Amongst its businesses involved in the power systems and electronics sector is AXA Power.


Houchin Aerospace, based in the UK, is one of the foremost names in the manufacture of diesel-driven 400Hz ground power units serving airlines, ground handling companies, military organisations and leasing companies in over 100 countries throughout the world. Its Model C490 and Model C690 GPUs are both EU Stage III A Emissions compliant and have optional 28VDC. The C490 offers 90kVA or 100kVA output while the C690 can also provide 140kVA output in addition. The company also manufactures a C690 for use outside the EU. Houchin is a division of ITW Limited.


UK-headquartered Hitzinger offers a range of rotary diesel UPS, airport GPUs, standby generators, frequency converters, alternators and tailored power solutions. Manufactured at its factory in Liz, Austria, products include 400Hz centralised and decentralised ground power systems, mobile ground power units (diesel or electrical driven GPUs) including data links for remote monitoring, automatic billing system, line drop compensation, failure recorder and cable management system.


French company Guinault is active in the GSE sector, producing GPUs and converters, ASUs and starter units. Established in 1949 and located near Orléans, the company supplies to both the civilian and military sectors, to airlines, ground handlers, airports and to armed forces.

GPU/frequency converters: Guinault offers a range of 90 – 180KVA frequency converters in different configurations, trailer, fixed and bridge-mounted. The technology used allows for reliable tarmac application and enables the equipment to be used in extreme climatic conditions.

Its GPUs continue to be introduced into the US market. Guinault currently delivers diesel GPUs to American Airlines and US Airlines, which have been attracted by the equipment’s reliability and ease of maintenance.

ASUs: Guinault ASUs are available in power ranges from 180ppm to 400ppm and offer variable speed technology. It can offer an ASU effective at -40 degrees and also developed an aero-transportable ASU for the Royal Air Force and French Air Force.

ACUs: Guinault’s ACU’s, developed in association with Lebrun, are available for both civilian and military applications. Lebrun adds the cooling expertise to Guinault’s GSE experience and know-how. Just recently, Guinault delivered three ACUs to Air France for the carrier’s A380s.