Inter-Tech Overload

How GPU works in Aircrafts

December 13, 2014 by · Leave a Comment 

Written by Start Pac

Generally, most starter motors and generators operate on turbine engines that work alongwith 30 volts without causing any damage. The highest amount of amperage draw is felt at the moment when the starter is activated. The amperage figure could climb up to 1000 amps on certain gas turbine start up engines.

As the startup continues, requirements in terms of amperage drop down throughout the activation cycle. A battery would need to be in good state by this time in order to minimize a voltage drop as a considerable load is applied during the start up. Usually as a load is applied to a battery, the voltage would tend to drop if the load is increased. In order to effectively start turbines, the voltage drop would need to be kept to a minimum.

Lower battery voltage levels will exude a lesser amount of amperage. Certain starter motors might even pull batteries down to 15 volts at the first phase during the activation of start up. Most engines manufacturers would recommend a volt of around 28.5 at start if this is available in order to limit any voltage drop to a minimum.

In order to achieve this, external ground power units (GPU) are used. In this particular case, it can be beneficial to the turbine engine as 20% of the energy is sent to the starter motor which makes the start more rapid and generates less heat. This increases the turbine life.

Start Pac is a company specializing in starting and ground power units. Some of their products offerings also include portable battery packs and aircraft maintenance equipment.

How to Use a Ground Power Unit to Jumpstart an Aircraft

August 18, 2014 by · Leave a Comment 

Written by: Start Pac

The process of jumpstarting an aircraft is nothing like jumping a car battery. It’s true there is a battery involved, but everything about the process is different. From the kinds of connections you need, to the requirements for voltage, great care must be taken to ensure the power is transferred properly to the plane. These tips will help you to use ground power to jump an aircraft if you’re ever in the need.

Fixed Ground Power

There are basically two types of ground power unit. The first is a portable one that can be carried out into the tarmac. It’s usually on a trailer of some sort, and it’s often hauled by a small cart or a car that takes it out to the tarmac. The other is a fixed system, where all of the power is centralized before it is  distributed to the aircraft itself. The main power supply must be close to the aircraft itself.

Maintaining Voltage

Maintaining the level of voltage an aircraft needs requires precision. A power unit is capable of supplying too much power, which is why measurement wires are added to the main cable. These wires measure the aircraft’s total voltage, and assist in adjusting the level of output to match the proper voltage. In most cases the magic number is 400 Hz, which is based off old designs that allowed for more compact batteries and electrical units.

The equipment to synchronize the voltage on aircraft isn’t always the most reliable. It’s common for ground teams to employ frequency converters, which do a better job at detecting the problems involved with synching the power systems for an aircraft.

Delivering Power

If the power unit is not close to the aircraft, a portable GPU can be wheeled out onto the tarmac. These units function on diesel, and they are either towed or mounted to a vehicle. Whether the unit is fixed or mobile, bridge mounted devices are attached to the craft where the passengers disembark. Power is transferred over a cable that retracts automatically after the craft has received the jump start. Aircraft power units can require up to four different connectors to properly transfer power from the unit to the craft.

Final Thoughts

Sometimes, airports will use a pit system to charge the power of an aircraft. When pits are used, they must be able to support the weight of the craft that is being serviced. These spaces are confining, so it’s important that crews are able to handle the cables themselves within these tight quarters.
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