Ramping up the power

posted on 6th April 2018

Ground power unit (GPU) technology is changing, as airlines’ requirements for energy on the apron become more and more stringent. Can the equipment keep up with ever more challenging demands?

Meeting those needs within tight environmental restrictions and in a cost-effective way is the task of a wide range of GPU suppliers. ITW GSE, the group that incorporates the brands of AXA Power, Hobart, Houchin, J&B Aviation and ITW Military, provides “the biggest variety of point-of-use solid-state and diesel GPUs, as well as the world’s smartest pre-conditioned air unit (PCA)” – all based on a true modular design – says Poul Elvstroem, the group’s vice president, sales and marketing. Over the years, ITW GSE has delivered approximately 80,000 such units to customers all over the world, he notes, also observing that, last year alone, 2,500 units left its production lines.9. AS_Aut15 - Ramping_1

One of ITW GSE’s established goals is to remain at the forefront of new developments in the GPU technological arena, Elvstroem remarks. “We were the first to cope with the Power Factor 1 requirements of the ‘all-electric’ aircraft, the first to launch a combined 400Hz GPU and a cable retriever system and the first to bring the patented Plug & Play system to the market.

“The design of new equipment is a combination of market requirements and the broad knowledge that we have gathered during the many years that we have worked within this field of business,” he advises.

During this past year, ITW has made a number of additions and improvements to its product line. Taking advantage of the wide range of experience that is gathered together within the various operations of the ITW GSE group, it has brought a series of new products to market that are all nevertheless still based on a common ITW GSE design platform, as explained by the common designation of ‘…400’ within their various product names.

The products are: the 1400, a solid-state 28VDC GPU that is said to be both small and highly reliable; the 2400 solid-state 400Hz GPU that, thanks to its patented Plug and Play system, provides high voltage at the aircraft plug; the 2400 solid-state 400Hz power coil that offers power with a 90kVA converter and a cable retriever in one single housing, ideal for passenger boarding bridges (PBBs); and the 4400 engine-driven 400Hz GPU, a completely new product, described as a quiet, fuel-efficient apron power system that is ideal for supplying power to all kinds of aircraft.

Common to all these units is an icon-based user interface that is as easy and intuitive to use as a smart phone or tablet. Notes Elvstroem: “Airport staff, already familiar with one ITW GSE product, can easily operate another because the icons and the display are the same. In this way, the number of human faults on-airport can be minimised.

“Another feature that our customers are very happy about is the possibility of software upgrades by means of a USB stick without installation of any additional plug-ins,” he adds.

ITW GSE’s AXA Power has had a particularly good year in the Middle East. Such performance confirms its strong position within the civil and military maintenance, repair and overhaul (MRO) and airport markets of the Middle East, Elvstroem says, noting that in excess of 1,750 solid-state AXA units are in operation in the region.

He points, for example, to customers including Abu Dhabi International Airport, which has opted for 136 units of AXA Power’s 90kVA AXA2400 GPU. In June, the Factory Acceptance Test was successfully passed in Denmark, witnessed by consultants from Aecom and Deerns, plus contractor Larsen & Toubro and Abu Dhabi Airports Company.

ITW GSE AXA Power was also contracted to supply 10 90kVA GPUs for the New Presidential Hangar and 12 90kVA power coils for the refurbishment of the T1 Terminal at the same airport.

Such success is definitely “all about connections”, Elvstroem says, but is also thanks to the company’s widespread representative network and its own regional office that provides what he describes as “good service, innovative products and warranting the lowest cost of ownership”.9. AS_Aut15 - Ramping_2

“Each of the ITW GSE brands has good and loyal customers who want to stick to the brand that they know,” Elvstroem insists. “And we want to ease their choice and support their decision. Therefore, we have decided to conserve the well-known brands and let Hobart and Houchin offer similar engine-driven products, and let Hobart and AXA Power offer similar solid-state products. However, we still have a lot of commonality between the products. This makes it easy for the customer to switch from one product to another, while also helping reduce the spare part stock requirements, since some parts are identical.”

That being said, there are certainly market differences that have to be catered for, he points out. Equipment sold in the US usually has to be UL-approved whereas equipment in Europe needs CE labelling (CE relates to a manufacturer’s declaration that a product meets European health safety and environmental protection legislation, while UL is a US-based safety consulting and certification concern, particularly active in the area of electrical devices). Also, input voltage differs across the world, and the manufacturer must tailor its units to suit local requirements.

Thus, ITW GSE has started introducing a UL version of the power coil in the US, where the market seems to particularly value a small and neat unit that is ideal for installation under a PBB. The unit combines a 90kVA converter and a cable retriever in one single unit that comes fully tested from the factory. It only requires installation under the PBB and connection of the input cables before it is ready to supply 400Hz power for aircraft at the point of use.


One of the strengths of ITW GSE is said by Elvstroem to be the group’s close relations with its customers and with the major aircraft manufacturers. London Heathrow, one of the world’s busiest airports is amongst the users of a range of ITW GSE GPUs. By way of example, explains Ian Smith, asset engineer – electrical at the London gateway: “We have a longstanding relationship with AXA and have been installing their static converters for over 20 years. We currently have circa 300-350 AXA converters on-site, which are either 2200 series, 2300 series or 2400 series converters.”

Smith continues: “We also have some PBB-mounted AXA power coils on our Multiple Apron Ramp System (MARS) stands and a few Cavotec power coils with AXA converters. We are due to replace the 2200 series converters within this regulatory period and we are currently going through the design process for Terminal 3 (T3) and Terminal 4 (T4) stands.

“With regard to the number of converters on a stand, we tend to use 90kVa blocks, so: 90kVa (one converter) on a code C stand, 180kVa (two converters) on a code E stand; and 360kVa (four converters) on a code F stand. If these are MARS stands, there is an additional PBB-mounted power coil on the left-hand centre line,” he notes.

Smith considers the most notable benefit of using the AXA cubicle is its modular design and high reliability of the converters. This, he says, enables Heathrow to limit the amount of down time on its converters and allows the airport to get faulty cubicles quickly back into service.

“We keep our converters as standard products so as to avoid any lead time issues when procuring new converters and spares,” he adds.


Changing emissions requirements have had a fundamental impact on the GPU market and on the work of the manufacturers making these units. For environmental reasons, more and more airports are banning the use of onboard aircraft auxiliary power units (APUs). Instead, the switch is made to external 400Hz solid-state power units and pre-conditioned air (PCA) units while the aircraft is parked at the gate.9. AS_Aut15 - Ramping_3

This configuration – coined ‘Go Green on Ground’ by ITW GSE – offers significant environmental benefits, reducing carbon dioxide emissions while aircraft are at the gate by as much as 85%. Furthermore, it means reduced noise levels, benefiting the operator, passengers, flight and cabin crews, as well as all other nearby ramp workers. Moreover, for airlines it means reduced cost with respect to fuel and APU maintenance. All together, the savings may amount to being worth as much as 100,000 Euros (US$115,000) per year per gate, Elvstroem estimates.

In terms of engine drive units, new and more stringent emissions regulations have come into force in the US. Traditionally, the ITW GSE diesel units sold in the US have been provided with Tier 3 engines. Due to environmental concerns and current legislation, this is now changing fast. Elvstroem explains: “Like other manufacturers, we are switching to Tier 4 motors that are believed to be greener, although it still has to be proven.” This is expected to lead to a healthier environment but there will also be an increase in the price of the product as a result, he says.

More than one GPU manufacturer is of the opinion that environmental pressures have radically shaken up the ground power business. Derek Rose, director and vice president, sales and marketing, at AERO Specialties, believes that as a result of changing emissions standards there have been more fundamental changes in the GPU world over the last couple of years than there were in the preceding couple of decades.

As noted above, the increasing stringency of US Environmental Protection Agency (EPA) restrictions has led the change. And where the US and the EPA has gone, Europe and other countries will – over time – almost certainly follow. Meeting Tier 4 requirements has added complexity and cost to GPU design and manufacture, requiring, for example, greater computerised control over systems and their emissions. GPUs now need to be much more efficient to meet these emissions requirements and they need the computer oversight and micromanagement to ensure that efficiency.

AERO Specialties’ JetGo GPU units have smaller engines but achieve the same power output as units with larger engines because they benefit from hybrid battery power support kicking in during peak starting applications. As a result, they fall below the emissions requirements pertaining to the larger engine GPUs and have not had to be redesigned in the wake of Tier 4 standards’ introduction.


AERO Specialties is a relatively small company, “but we’re always trying to do something a little different and a little better”, Rose says. It is an authorised distributor of some other GSE manufacturers’ products, including Unitron, TLD and Eagle Tugs, but it is also an OEM (original equipment manufacturer) in its own right, offering towbars, lavatory and potable water service units, maintenance stands and oxygen and nitrogen service systems as well as its JetGo range of GPUs.

As evidence of its constant product development, Rose points to AERO Specialties’ latest offering in the GPU space, the JetGo 800AL-RJ, which was only launched earlier this year. The 800AL-RJ is a 28.5V DC diesel-electric GPU that features both a four-cylinder diesel engine and hybrid battery systems designed for the regional aircraft market. A higher powered development of AERO Specialties’ popular JetGo 550Mti-RJ GPU that has served the business and executive jets market well, the 800AL-RJ is intended for more powerful turboprops such as ATR-72s and Q400s.

The unit’s continuous steady power output can be supplemented by the hybrid battery system for peak power to allow for a cooler aircraft engine start and significant fuel savings. The unit is, Rose says, very easy to use, requiring only plugging into the aircraft and the flick of a couple of switches before it starts offering power to the aircraft (the aircraft will ‘pull’ the power it demands from the unit). Its design allows for easy maintenance and repair, with the unit’s generator, the part of a GPU perhaps most likely to go wrong, being readily accessible for easy change out – something that is not the case with other GPUs, he argues.

Its galvanised steel frame, fibreglass case and stainless steel components protect the unit from rust and corrosion, while its low-profile, soft-edge, streamlined design helps minimise damage to both the unit or an aircraft should the two collide.

The 800AL-RJ is particularly quiet. Plus, the unit is “very competitive on price”, Rose insists, maybe 20-25% cheaper than comparable models offered by competing manufacturers. And, finally, it is both powerful and ‘green’; with an EPA Tier 4 rating for low-emission non-road diesel engines, it meets the ever tougher emission requirements governing GPU and other GSE emissions.


Red Box International manufactures a comprehensive range of DC ground power units to provide both start power and continuous power at a range of voltages and current ratings for aircraft of all sizes requiring DC power on the ground (it also markets a range of aviation tool kits, tool control systems, aircraft moving equipment, inspection cameras, cable assemblies and portable coolers).

Over the course of the last year, explains sales director Ashley Marshall, Red Box has been reviewing its range of products, not only its own manufactured products but also those it represents, in order to “add value based on our experience”. It has developed a special digital transformer rectifier unit to support aircraft on offshore rigs, for example. The quality of the output voltage and current needs to be particularly accurate on these units.

Red Box has enjoyed an increase in sales into the Asia Pacific region of late – especially into China. The company didn’t previously have a significant footprint in the country. However, since the relaxation there of the ban on using low-altitude airspace and the appointment of what Marshall describes as “a hard working in-country distributor”, Red Box’s presence in China has grown substantially and it is now “a recognised brand in the general aviation industry” there.

One particular customer of note is Regional Express in Australia. Regional Express contacted Red Box about finding a solution to support its fleet of Q400 Dash 8 aircraft on the ramp. Electrical power wasn’t always available on-site and as such an independent power source was required. Red Box’s HybRED 170/6 was the answer, says Marshall; this unit can provide up to 170 amps continuously at 28V DC, allowing the aircraft to perform all the required pre-flight checks before take-off.

Red Box GPUs offer a number of significant advantages to users – amongst them, high power-to-weight ratios, high-quality components and purpose-designed components, Marshall insists. “However, the added value is in our recommendations,” he continues. “We understand that each customer is different, with a different requirement – as such we take all information into account and create a solution that ticks all the boxes. We also have a metal fabrication company, so we can create bespoke solutions when required.”

Marshall is not of the opinion that the GPU market is likely to change fundamentally in the near term – an aircraft requires ground power for ground operations or for starting and, he says: “This will always be required.” Of course, as we saw above, national and international environmental regulations are becoming more stringent, being relevant to on-airport noise and emissions. But, Marshall informs, Red Box predominantly manufactures efficient, quiet solid-state systems such that noise and emissions “don’t play a major role for either Red Box or its customers”.


TLD, the France-headquartered supplier of a wide range of GSE, has been improving its GPU product line of late. Its entire ground power unit range has been modified and modernised, says TLD EMEAI (Europe, Middle East, Africa and India) CEO Valentin Schmitt.

In particular, its GPU-409 and GPU-418 models have been redesigned to make them even more compact (for easier manoeuvring around aircraft) and to improve their fuel efficiency. The -409, which meets all the latest US and European emissions requirements, has been streamlined and operates off a highly efficient generator running at 1,846 RPM. This is said to allow not only fuel savings but also less noise, while still ensuring “rapid transient response and exceptional frequency regulation”. The -409 meets US Tier 4 requirements. According to Schmitt, TLD’s range of GPUs represent the most fuel-efficient ground power units in the market.

TLD has paid a special attention to the maintenance cost of its GPUs and to the ease of operation by designing a new and improved version of its electronic GCM (Generator Control Module). The GCM2 makes the TLD GPU extremely simple to use, featuring an attractive colour display and interface available in any customer’s language.

TLD is now manufacturing GPUs in Europe, as well as in North America and China.


Guinault Lebrun is another of the many suppliers that offers a ready alternative to using an aircraft’s own APU on the ground, providing 400Hz power supply for cabin air-conditioning and engine air starting. Indeed, it has a “very special position in this market, being an expert in the refrigeration industry and electrical power, as well as being a GSE specialist”, says a Guinault Lebrun spokesperson.

Its expertise in these various fields, backed by the long-term strategy of a family-owned organisation, allows it to deliver what it describes as “a complete solution” for aircraft power provision on the apron. Indeed, Guinault Lebrun insists that it markets and sells aircraft power, aircraft engine starting and aircraft cabin comfort, rather than GPUs, ASUs and ACUs.

Other selling points include Guinault Lebrun’s claim to offer the lowest total cost of ownership (TCO) on the market, basing this on its GPU units enjoying the most efficient engine rpm of 1,714 – “the best compromise between performance, response time and fuel consumption”, the company says; the highly efficient Guinault alternator, manufactured in France and optimised for the low-load operations that typically represent 70% of the operating time of GPUs; and Guinault Lebrun’s own electronic control system that is resistant to sandy, dusty windy, humid and otherwise corrosive atmospheres.

Having both the electronics and alternator designed in-house offers great advantages in terms of obsolescence management. Moreover, Guinault Lebrun’s units are compatible with the latest aircraft in use – its 400Hz power supplies, solid-state converters and diesel-driven GPUs have all been validated on the latest A350s at Airbus’ own facility, for example.


JBT has released details of a new diesel-powered, trailer-mounted, 180kVA GPU it is now offering. The D-180 is designed to continuously supply the power that the manufacturer notes is required of the latest jet aircraft like the B787, A350 and A380. “Reliable 400Hz power is produced from a diesel engine-generator combination available in either Tier 3 or Tier 4 configurations that meet the most stringent environmental requirements,” the supplier observes.

The frame and shell of the unit are said to be made of robust, heavy-duty materials to withstand the vibration and wear of use on a busy apron, while it is able to provide critical operational and diagnostic information to its operators and maintenance personnel. “Gone are vulnerable, unreliable analogue gauges,” a JBT statement insists. Instead, digital displays record engine performance data, relevant maintenance and diagnostic data, as well as key operational metrics such as fuel status, voltages, amperages, frequencies, kilowatts, run times and unit status.


“We constantly monitor shifts in the aviation industry and new developments from the aircraft manufacturers,” explains Mark Marar, director of operations at Las Vegas-based GPU supplier Start Pac. “Our process is one of constant improvement of our product line wherever possible to better meet the demands of the market.

“During the last year, we have developed 26V GPUs for fleets with voltage sensitivities, in order to provide them with the most power possible but at a voltage that can still be accepted by the various aircraft. This line of 26V ground power units utilises our safe lithium technology and to protect the battery chemistry we have developed a low voltage protection system that prevents deep discharge when the unit is being used for avionics.”

Furthermore, Marar continues: “Our patented Quick Change technology and all-in-one design makes our units extremely user-friendly in the field all over the world. Battery changes can be completed in the field in seconds without tools or training and our chargers are always built in so that the end user does not have to keep track of additional charging equipment.”

Start Pac primarily serves business jet and helicopter markets. It can meet the requirements of most electrically started aircraft engines, as well as on-board APUs for pneumatically started aircraft.