The new power distribution system, which will be rolled out in airline fleets later this year, will tap power from generators in a plane’s engines and distribute 15 volts of DC power to outlets located in seat armrests. This should be a boon to travelers with notebook PCs who would like to make flying time more productive.
However, the initial deployment will only be in first-class and business-class seats on aircraft making international and long-range flights, and those who want to use the outlets will need to buy a special power adapter for their notebooks.
For the airlines, safety is the primary consideration, so the system is designed to provide convenience to passengers without robbing other plane systems of power. Primex Aerospace Co., of Redmond, Wash., has designed one of the first systems, the EmPower, which consists of three major components: an MCU (master control unit), an ISPS (in-seat power supply) and outlets (see diagram).
The MCU manages the power that comes from generators in the plane’s engines, distributing it to as many as 120 seats per MCU. The device monitors the system for faults and system load, as well as controlling the ISPS. The flight crew can turn off power to the MCU when necessary, including during takeoff and landing.
Ideally, each seat on a plane would have outlets that could be used as needed. However, because there is a limit on the amount of current available to the system, a load-limit select module is used to set that limit, and then the MCU monitors how much power is being used.
In normal operation mode, all outlets are enabled but not all are in use. As more passengers plug in notebooks, the system reaches the load limit. At this point, the MCU turns off the ISPS units not already in use. The master control unit continues to monitor the load until it is 10 percent under the maximum, at which point the remaining in-seat power supply units become available for use.
Although the engine generators supply AC power by default and notebook power supplies tap AC power, the airlines specified DC power at the seats for safety reasons.
Each ISPS unit converts the power supplied by the MCU from AC to DC and provides another level of fault tolerance to the system. These units monitor for faults and over/under voltage situations.
To conserve power, the in-seat power supply operates in standby mode until a notebook is plugged into an outlet. Once this happens, the ISPS unit begins supplying power, unless the notebook causes a fault in the system, in which case it cuts off power to the outlet.
Let there be light
Passengers can tell when in-seat power is available by looking at an LED next to the two outlets. The LED illuminates at half brightness to indicate that power is available and is fully lit when power is being supplied to a notebook.
Because of safety considerations, no power is supplied to either outlet at a passenger’s seat unless a cable is plugged in. The power adapters fit snugly enough to keep from being accidentally unplugged and to keep spilt liquid from getting into the outlet. The second outlet could be used either to charge batteries or to power a second electronic device, such as a handheld video player.
A formal standard for the connector type that will work in these outlets has not been ratified by the airline industry’s standards board, but of the nine airlines that have announced plans to deploy such a system, only American Airlines has proposed using a unique jack. The first airline to announce plans for in-seat power, American suggested using an automobile-type cigarette lighter jack because of its prevalence.
The proposed connector standard, ARINC-628, will likely be ratified later this year and uses a smaller connector than the one American Airlines has proposed. This connector would fit in the EmPower outlets.
For notebook users interested in buying connectors for the EmPower outlets, power adapter supplier Xtend Micro Products Inc., of Irvine, Calif., has announced adapters that will work with the EmPower system.