Alenia’s EM test chamber nearly ready

By Paolo Valpolini

July 15, 2008
Aerospace Industry

Electromagnetic (EM) compatibility testing, which has become increasingly important with the advent of new technologies such as fly-by-wire controls, the saturation of airspace with high-frequency EM emissions and the decision by some airlines to allow mobile phone calls aboard their aircraft has prompted Alenia Aeronautica to build Europe’s largest anechoic chamber.

The chamber, located at the Italian group’s Caselle Sud flight test center near Turin, is in the final stages of testing. Large sliding doors allow the simulator to take the front ends of aircraft up to the size of Boeing 737s and the facility is the largest of its type in Europe. The chamber is completely shielded in zinc-coated steel panels and covered with radiowave-absorbing material.

The chamber is situated in the same building as the Sky Light Simulator, which artificially reproduces ambient natural lighting conditions to verify the extent to which instruments can be read once they have been integrated into cockpits.
The facility is equipped with a 32-foot diameter turntable that can carry loads up just over 66,000 pounds. The turntable can be tilted different angles to a precision of 0.02 degrees, allowing the underside of aircraft to be thoroughly tested. The facility also has a hoist system that can lift aircraft weighing up to 55,000 pounds to just over 50 feet with landing gear retracted.

For lower frequencies, from 30 MHz to 1 GHz, the facility is equipped with a movable arm with nine degrees of freedom. This has three different antennas according to the frequencies involved, while for higher frequencies from one to 18 GHz, a trolley equipped with numerous different horn antennas is used.

The chamber, which will become fully operational in September, will be used
for standard and radiated tests. Standard tests cover systems compatibility, emissions measurement and enhanced radiofrequency levels. Radiated tests comprise external radiated susceptibility of systems, as well as evaluations of low-level swept-frequency microwaves, and continuous- and pulse-radiated fields.
The low reflectivity level provided by the chamber allows users to accurately assess the parameters–such as radiation pattern and direction–of the antennas. Also available is near field-far field test equipment, which consists of a moveable trolley that positions a 20-foot diameter arch close to the antenna. The arch is equipped with 128 probes that gather the energy in a spherical environment around the antenna. This data is used to calculate the radiation pattern using complex mathematical algorithms.

The Caselle Sud site also features a reverberating chamber for field uniformity tests
at frequencies higher than 200 MHz, as well as an electronic warfare (EW) chamber, where measurements on classified EW equipment can be carried out. The facility is to be further upgraded to carry out other EW tests, as well as radar cross section measurements on aircraft components.

The new Alenia facility allows testing with much higher output power than
previous open-area test sites available. Its absorbent material converts the electromechanical energy into thermal energy. A thermal camera carries out continuous surveillance and a fire suppression system is ready to inject inert gas.
Alenia also has a flight test center at Decimomannu on Sardinia. Like the facility at Caselle Sud, the Sardinia facility features two connecting control rooms and is fitted with advanced telemetry systems to relay data to other locations. The facilities can test four aircraft at the same time, monitoring and recording some 10,000 parameters per aircraft for an information flow of about 1 gigabyte per second.

The Alenia facilities may now be used to carry out EM compatibility tests, as well as noise and navigation flying tests, on Russia’s new Superjet 100 regional airliner. The intention is to accelerate the aircraft’s certification to Western standards. Alenia is the majority partner in the Superjet International joint venture with Sukhoi that is responsible for marketing, deliveries and customer support.

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