Cobham’s Satcom System to Solve Rotor-Induced Packet Loss

By Frank Wolfe | March 8, 2019
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United Nations workers in Somalia disembark from an Mi-8MTV helicopter in November 2014. (United Nations)

United Nations workers in Somalia disembark from an Mi-8MTV helicopter in November 2014 (United Nations)

Ed. Note: Helicopter data transfer often suffers significant degradation as a result of the overhead rotor blades, but Cobham has a satcom solution aimed at avoiding this difficulty, extending range and reliability for rotorcraft operations. Read on for details from our sister site, Rotor & Wing International.


Inmarsat is set to approve satellite communication rates for a new waveform, developed by Cobham last year, that promises to bolster significantly beyond-line-of-light communications for helicopters in the air.

Moving rotors can drastically disrupt satcom signals, a signal degradation known as “rotor shadow” that leads to up to 40 percent packet loss for SATCOM data, according to Cobham. There have been some workarounds in the past, yet they are expensive, and the new system by Cobham and Inmarsat, the SB-Helo X-Stream, may prove to be just one-quarter the operational cost of those workarounds, according to Cobham.

X-Stream purports to increase the throughput of high-quality 1.5 megabit-per-second streaming from 60 percent to nearly 100 percent for helicopters in the air, offsetting the effect of “rotor shadow” almost entirely.

“We literally have no packet loss with SB-Helo X-Stream,” Shaun Schaper, a sales and support engineer for Cobham satcom, said here during Helicopter Association International’s HeliExpo.

Todd McDonell, the president of global government at Inmarsat, forecast that SB-Helo X-Stream, an enhancement of the Inmarsat X-Stream service, “will be greatly sought after in the growing government helo market.”

After developing the new waveform from May to November last year, Cobham said it successfully tested the waveform on a Russian Mi-8 that belonged to a Hungarian skydiving company. The company wanted to test the waveform on a large, big-bladed helo like the Mi-8, as the rotors on such helicopters are known to disrupt SATCOM signals more than the blades on smaller helos.

SB-Helo X-Stream will be free for operators that already have Cobham AVIATOR SP systems. A significant majority of AVIATOR SP users are government clients, including the military, border patrol, disaster management agencies, Medevac, firefighting units, and humanitarian/international organizations like the United Nations.

One of the largest U.N. aviation providers has been Ukrainian Helicopters with a fleet of more than two dozen Mi-8MTV1s. Several years ago, those aircraft became the first to comply with new U.N. helicopter requirements that helos on U.N. missions must have the United Nations Aviation Global Satellite Tracking Solution (UNAGSTS) — some satellite data link that can precisely geo-locate a given helicopter — and Enhanced Ground Proximity Warning System/Helicopter Terrain Awareness and Warning Systems.

To comply with the U.N. mandates, Ukrainian Helicopters installed a number of systems, including Iridium SkyTrac ISAT-200A Global Positioning System/Iridium transceivers, the Sandel ST3400H Helicopter Terrain Awareness and Warning System and the Honeywell TCAS-II CAS-67A Traffic Collision Avoidance System.

Eight of those helicopters from Ukraine recently proved of value in Mali where they transferred medical data on patients in rural areas to doctors in the United States who were able to examine the patients and treat them via video teleconferencing. Those helicopters were parked, however, during the data transfer so there was no “rotor shadow” effect. Helicopters in the air that can readily provide patient and other data such as intelligence, surveillance and reconnaissance through such systems as forward-looking infrared, will likely be of significant value to governments and aid organizations.

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