The Importance Of Aircraft EMI Testing

EMI, or electromagnetic interference, is a serious task in the development of aircraft to assure the safe and secure operation of aircraft in flight. EMI is the primary reason why all commercial passenger aircraft request that passengers turn of their mobile electronic devices during critical operations in flight: take-off and landing.

These devices, laptops, smart phones, cell phones, electronic games, CD and other audio players, etc, all transmit variable intensities of electronic pulses. Of particular concern are devices that transmit electromagnetic signals as the primary purpose of their use: cell and smart phones. These devices are prohibited from use at all times during flight. The other devices are capable of passive transmission and are thus prohibited from use during critical operations of take-off and landing.

These devices have been shown to be suspect in causing certain events in flight such as flight deck indicators, auto-pilot disengagement, and sending aircraft off course with unintended turns.

Manufacturers and Operators of Commercial Passenger Aircraft are Addressing the Issues of Passenger Personal Electronic Devices in Three key areas of concern:

1. EMI testing of these devices. This testing is meant to detect and attempt to prevent EMI-affected events from occurring by increasing efforts to design the potential of EMI-affected events out of operational concerns. This testing addresses potential for four possible interference modes:

• Inductive interference, that is, when the transmitter affects receiver components or circuits by electrical or magnetic induction that is usually separated by less than a wavelength of the transmission.
• Conductive interference, that is, when the transmitter affects receiver components or circuits that are directly coupled by a conductive element such as a wire or cable. This is typically an internal systems design issue since passengers have no access to direct conductive interference.
• Capacitive interference, that is, when the transmitter affects receiver components or circuits that are coupled by electrical fields between adjacent conductors that may be separated by less than a wavelength of the transmission.
• Radiative interference, that is, when the transmitter affects receiver components or circuits that are coupled across a distance that is greater than the transmission wavelength.

2. Recommendation of regulations for control of use of personal electronic devices. Based on the above test modes, manufacturers and operators make regulative recommendations to prevent or severely limit the use of these devices by passengers in flight.

3. Review of actions to investigate and prevent EMI-caused events. When an event actually occurs in operational flight, the operator will contact the manufacturer and the regulative body, typically the Federal Aviation Administration, to report the incident and to begin investigation for cause and to initiate modifications, improvements, etc, to existing design and testing protocols. This is necessary due to the continuing advancement of innovation, design and manufacture of these devices.

By dedicated performance and innovative improvement of these three key activities, the commercial passenger aircraft manufacturers and operators will be equipped to continue to keep airline transportation the safest mode of transportation in existence.