Business & GA, Commercial

Wireless Cabin Security

By David Jensen | May 1, 2005

After locked cockpit doors were mandated and some airlines decided to install cabin surveillance systems, as well, Sun Country Airlines chose to explore a further step. With FAA funding from the Enhanced Airplane Security Program (EASP), the Minneapolis-based low-cost carrier--which also provides charter flights--opted to install and evaluate a wireless cabin security system.

Well, at least the Sun Country system includes an approved wireless component; a totally wireless system would probably be cost-prohibitive. The cameras on board one of Sun Country's seven Boeing 737-800s still are linked by wire to the overhead control unit, which also serves as a power supply and image brightness control. But the control panel is connected to an adjoining server that has been set up for the IEEE 802.11b wireless protocol. This allows the delivery of video imagery from the security cameras to the airplane's portable electronic flight bag (EFB) over a radio link at 2.4 GHz. Each of Sun Country's EFBs has an antenna "stick" protruding from its PCMCIA slot.

The B737-800 has been equipped for a trial program. As this was written, Sun Country was considering upgrades of both the server and its EFBs, according to Thomas (TJ) Horsager, the carrier's operations engineer.

Spirent's Aviation Information Systems (acquired by Teledyne Controls in July 2003) has provided Sun Country's EFBs and the modified docking station for use in the aircraft. The EFB's are ruggedized tablet computers from Florida-based Walkabout Computers. They have a 40-Gbyte hard drive and 933-MHz processing speed--typical of many laptops.

Along with cabin system monitoring, Sun Country pilots use the EFBs primarily for weight and balance calculations, runway analysis to determine performance settings for takeoffs and landings, and to view documents. The EFB incorporates types A and B software (not requiring certification), as described in the advisory circular AC120-76A. During certain phases of flight the pilots will stow the single, Class 1 EFB in a docking station that also serves to recharge batteries.

Decision Around EFBs

The EFBs were key to Sun Country's decision to incorporate the wireless component for cabin surveillance monitoring. "We already have the EFBs installed, and for cabin monitoring we wanted to consider using an available display source," says Horsager.

The server for the Sun Country aircraft was provided by Hollingsead International, which also amended the original supplemental type certificate (STC) for the wireless component in June 2004. The manufacturer claims it is the first wireless security system to receive FAA approval.

The server is a LynuxWorks-based system. "Anyone can write code for it," says Bill Weaver, Hollingsead's president. "We wanted to make the upgrade path as simple as possible for Sun Country."

Sun Country didn't jump headlong into wireless technology. Its program to incorporate cabin security systems was divided into two phases. The first phase involved the installation of a fully wired, Hollingsead Sentry One video system with ultra low-light cameras and a dedicated control display unit (CDU). "We wanted to start with a proven system that was relatively easy to certify, as soon as possible," Horsager explains.

Installation during the first phase quickly revealed one advantage to going wireless. "For phase 1 we had a dedicated monitor in the center console, and for that you had to run wires down through a conduit under the floorboard. It was a long process--about 70 hours--and this became an installation shortcoming, which is one reason why we looked into a wireless system," says Horsager.

Conversely, installing the server "took only eight hours," he adds. For FAA approval, Hollingsead conducted DO-160 tests of the equipment, and Sun Country and Hollingsead performed ground and flight tests to prove that the server created no eletromagnetic interference (EMI).

For the second phase Hollingsead was to work with the airline and Spirent (now Teledyne Controls) to upgrade the Sentry One system to incorporate the wireless video server. The server was installed for trial use in the B737-800 in June 2004.

Modifications Planned

Although the wireless system performed well, Sun Country is (as this was written, in early April) contemplating various equipment options. Should the carrier choose a wireless connection fleet-wide, it first would seek a modification, says Horsager.

Sun Country pilots have been using both the wireless and wired security systems side-by-side and they "currently prefer the wired version," he reports. Horsager explains that "the wireless server converts the video stream from analog to digital, and the screen refresh rate is approximately a half second, so the imagery can appear jumpy. That seems to bother the pilots." The analog video imagery on the wired version, conversely, appears smooth and uninterrupted. "It's just like watching TV," says Horsager.

Hollingsead is addressing the refresh rate issue with work on a new server that delivers cabin surveillance imagery at a much faster rate of 10 frames per second. The company also is proposing a "server that is compatible with EFBs with Ethernet connection or wireless link," says Weaver. This gives Sun Country options, for example, to have the monitors in the flightdeck wired and a monitor in the cabin--for use by a flight attendant or an air marshal--that is wireless.

Indeed, the proposed Hollingsead cabin security system could well complement the upgraded electronic flight bag that Teledyne Controls may propose. Admitting that his company must first mature discussions with Sun Country officials to determine their long-term EFB needs, Teledyne Controls' Dennie Schmitz, senior director-business development, nevertheless envisions a two-element system for the carrier. It would be comparable to the Teledyne Controls configuration chosen by Continental Airlines for its Enhanced Airplane Security Program trial. The two-element system would have the processor positioned separate from, but tethered to, a thin tablet-like display.

"The key advantage the two-element system brings is the display element would be so small and thin that it could be positioned or mounted in various flightdeck locations," says Schmitz. "That would make it more flexible" than the EFBs the carrier now uses. Horsager indicated, as well, that his company would like to have two EFBs in the cockpit and the ability to have them in operation during all phases of flight.

Playing a Bigger Role

Schmitz envisions a wired link between the EFBs and the Hollingsead server; however, he still sees benefits in having wireless connectivity. In addition to providing imagery to monitors stationed in the cabin, a server could allow the transfer of video and data to the carrier's flight operations via a gatelink.

"The wireless function forms a network environment within the aircraft," Schmitz explains, "and it could be incorporated into the [airline's] corporate network." Onboard data then could be distributed to the appropriate departments--dispatch, maintenance, flight operations, etc.--within the airline organization.

How Sun Country Airlines will outfit its fleet of new Boeing 737s has yet to be determined. However, the carrier appears convinced that electronic flight bags improve operations and that cabin surveillance improves onboard security. And they are proud of pioneering the use of a wireless element that links the two systems.

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