Ground Power Units are battery-powered generators that supply energy to the aircraft allowing the electrical systems to be operated when the aircraft is on the ground. GPUs are connected to a normal three-phase main power source and switch on when an aircraft requires it. The electric energy is carried from a generator to a connection on the aircraft via 3 phase 4-wire insulated cable capable of handling 261 amps (90 kVA). These connectors are standard for all aircraft, as defined in ISO 6858. A so-called "solid state unit" converts power from AC to DC along with current separation for the aircraft power requirements. Solid state units can be supplied stationary, bridge-mounted or as a mobile unit.

GPUs may be added to existing equipment or used as stand-alone machines. Depending on the size and model of the aircraft, ground power units can be used with both gas-powered and diesel-powered aircraft. GPUs are used on all aircraft from large commercial airplanes to small jets and helicopters.

• Airplane electrical systems vary in their complexity, however, some of the critical functions include
  ·        Electric starters
  ·        Lights
• ·        Electric flight instruments
• ·        Navigation aids
• ·        Radios/Communication systems
• ·        Passenger entertainment systems

Aircraft electrical components also include system monitoring and warning provisions that are incorporated into the electrical system. These warning systems are presented to the pilots when appropriate. Warnings may include but are not limited to a generator malfunction/failure, TRU failure, battery failure, bus fault/failure and circuit breaker monitoring. The aircraft manufacturer also provides detailed electrical system isolation procedures to be utilized in the event of an electrical fire.

While most aircraft are direct-current-powered, not all aircraft operate on that standard. Therefore, it is important to find a GPU that can operate on both systems. General aviation and smaller jets generally operate on a 12-volt system, while turboprops and jumbo jets use a 24-volt system. A GPU must be compatible with the different voltages and ensure that it can meet the specifications of both systems.

The most common form of an AGPU is the electrical one. It provides continuous electrical power for an aircraft's systems. These are also often used on the ground before pushback. Once an aircraft has landed, it will be disconnected from the airport's ground electrical system and a mobile or fixed electrical power unit. If it fails to start, it will be reconnected to the fixed type of AGPU. A fixed-type unit is also a good backup.

The biggest disadvantage of auxiliary power units is their limited duration. The capacity of battery banks determines how long the GPU can work. Both PowerAll System GPUs, the PA-2400 and the PA-2400-50 deliver more than 2400 peak amps for starting using groundbreaking AGM battery technology designed for use in extreme conditions.  

By using an AGPU, the aircraft's onboard systems can be powered, thus allowing the pilot to perform interior and electronic system testing without a problem. Moreover, the use of a GPU is safer than using the aircraft engines for routine systems testing and maintenance. It is a good choice for pilots who are in the process of planning their next flight. While some airports do provide power for parked aircraft, they are often noisy, cumbersome, and inconvenient.

Auxiliary battery power GPUs are more costly than electrical ones, however, they are worth the investment. If installed properly, they can last for decades and will be a highly efficient and reliable option.

GSE (Ground Support Equipment)
Most ground services are not directly related to flying the aircraft but involve preparing the aircraft for the next flight. GSE activities include cabin services for passenger comfort and safety. These tasks include the following.

·        Cleaning and sanitizing the passenger cabin

·        Replenishment of on-board consumables

·        Removing trash

·        Potable water storage

·        Replacing items such as soap, pillows, tissues, blankets, and magazines

·        Lavatory tank waste drainage

·        Food and beverage catering

·        Aircraft refueling, engine and fuselage examination and maintenance

·        Safety and security checks

As you can see, airport GSE comprises a wide and diverse range of vehicles and equipment necessary to service aircraft during passenger and cargo loading and unloading, maintenance, and other ground-based operations.
 

In addition to the above noted aircraft preparation and maintenance tasks, ground airport personnel are also responsible for baggage, cargo, and passenger loading, as well as checking aircraft storage areas for lost items, and to assure that all seats and storage bins are equipped with the proper comfort items and safety materials.

Some airlines employ outside GSE contractors to support all these operations; however, electrical power and conditioned air are generally required throughout gate operational periods for both passenger and crew comfort and safety.