A workplace in the sky
By Jim Sparks
Photo By Jim Sparks
Aircraft have often been recognized as one of the primary achievements in making our world smaller. It is now possible to travel virtually anywhere on the globe within a 24-hour time period. When this phenomenon first came into existence, it was a real challenge for the airlines to figure out how to keep the passengers occupied for extended periods of time. If nothing else, people could settle back and listen to the drone of the engines while staring into the vastness of what is the world of aviation.
A workplace in the sky
In the past, a day of travel meant reading the paper or a good book along with AMT Magazine, then taking a nap or getting a deck of playing cards from the flight attendant only to be disturbed by a first-class food service, and then resuming the nap until landing. Today, air travel means not interrupting business as usual. Both airlines and manufacturers of business aircraft have adjusted to this fact. The pomp and elegance associated with lounging and relaxing is rapidly making way for a workplace in the sky.
Cabin noise control is often an issue where enhancements are needed over and above standard insulation packages. Generally, the larger the cabin, the greater the ability to naturally dampen sound. In smaller aircraft, this can be achieved through vibration damping interior attachments. Still, some passengers are sensitive to elevated decibel levels and may require special techniques such as "Black" or "Negative Noise." This is most effectively provided on an individual basis through a "Noise Canceling Headset," a device that senses ambient cabin noise in specific frequency ranges and then produces a frequency the same as the offending sound — only 180 degrees out of phase. This effect will negate the noise. In addition to the standard audio input, this specialized device requires a dedicated power supply, typically accomplished by supplying a separate electrical plug that installs in a receptacle located within close proximity to the audio jack.
Communications capabilities and challenges
Communications capabilities are most often the paramount factor in maintaining a successful business. This one factor is with out doubt recognized by airlines and business aircraft manufacturers alike. It has been possible now for some time to place telephone calls from an aircraft to virtually any other telephone on the ground or in the air. This capability has posed many challenges to system designers. First of all, a high speed aircraft operating six or seven miles above the earth at nearly any point on the globe will not be conducive to the standard cellular telephone technology. Satellite Communications (Satcom) provides one answer. Inmarsat (International Mobile Satellite Organization) operates a series of four operational communications satellites operating at high altitudes over the earth’s equator.
The principle here involves the aircraft locating and then establishing communications with a satellite within the same quadrant of the hemisphere as the aircraft. A link is in place from each satellite to strategically located ground stations. Once the downlink is complete, the ground station couples the communication from the aircraft into the local ground based telephone system. The first challenge is for the aircraft to locate the appropriate satellite. This requires the use of computers that can calculate the satellite’s coordinates. Once this is achieved, the aircraft needs to know where the target is relative to the aircraft and involves the onboard navigation systems coordinating with the satellite communication equipment and then positioning a directional antenna to locate and then lock on to the satellite transponder. When a lock on is established, transmissions can occur. The high altitude trajectory of the satellite requires the aircraft to communicate with a high power amplifier. This type of communication is rather costly on a per minute basis and up until recently, the data transmission speeds were such that it was not an economical means of retrieving email.
Inmarsat has just announced that by the end of the year, a high-speed data transmission service will be available. Users will now be able to access the Internet on Satcom-equipped aircraft at 64,000 bits per second now and up to 432,000 bits per second by 2004. Although this system will work using existing equipment with minimal change, an onboard computer server may be required. There is still some concern that an abrupt maneuver of the aircraft may cause a disruption of the data link with this type system.
In addition, Honeywell Avionics has teamed with Thales Avionics to produce a new seven channel Satcom system. It is advertised to produce enhanced long range voice and data communication with the ability to interact with alternate satellite constellations. This includes the future Aeronautical Telecommunications Network (ATN) — a segment of the plan to prevent overtaxing communication radio frequencies by replacing voice communications with digital messages.
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