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The last few weeks have been spent thinking about a good topic for this issue and after talking with friends and co-workers, no notable subject jumped right out. I even ventured into the hangar, looked around at the various aircraft that were home and out of the fleet, and couldn’t come up with one significant event that was worth putting in print and that was an eerie feeling. There was however that sensation of impending doom that we all know well which occurs just as contentment sets in.

I then decided to go online and peruse a few web sites that have provided inspiration in the past but still, that perfect topic continued to be elusive.

Cabin communications
One of the things that did come to mind was the subject of cabin communications. Advancements in telephone technology are almost a daily occurrence. Cellular telephone service providers continue to bombard all forms of media with gadgets and operating enhancements. In the general aviation world, satellite phone service is ballooning much like its terrestrial counterpart. The long time alliance of Verizon service with Magnastar airborne equipment has been one of the most recognized marriages in the air to ground telecommunications business and provided a reliable phone network across the continental United States. Recent advancements to celestial communications systems have resulted in reliable and economical data and voice transmissions worldwide. The migration of aircraft operators from terrestrial to celestial systems has resulted in Verizon questioning the longevity of their service. At present continued operation is planned through the end of 2008.

The two leading space based competitors are the Iridium and Inmarsat satellite constellations.

Iridium is an orbital network providing voice and limited data features all over the globe. When an Iridium customer places a call from a handset or terminal, it connects to whatever satellite happens to be overhead, and is relayed among satellites around the globe to whatever satellite is above the appropriate Earth gateway, which downlinks the call and transfers it to the global public voice network or Internet so that it reaches the recipient.

The satellites are in a near-polar orbit at an altitude of 485 miles (780 km). The 66 active satellites fly in formation in six orbital planes, evenly spaced around the planet, each with 11 satellites equally spaced apart from each other in that orbital plane. A single satellite completely circles the Earth once every 100 minutes, traveling at a rate of 16,832 miles per hour, and traveling from horizon to horizon across the sky in about 10 minutes. As a satellite moves out of reach, the call is handed over to the next satellite coming into view.

In February 2007, Iridium announced a bold vision called “Iridium NEXT.” NEXT will replace the company’s current satellite constellation with an even more powerful system before the present level of service is ever compromised due to constellation age.

Aircell is one of the Iridium service suppliers and one of the more prevalent in business aviation. It was Aircell that, in mid 2006 won the Federal Communications Commission (FCC) auction granting it part of the frequency spectrum that had been used by Verizon and has established a broadband network across a large part of North America.

On Dec. 11, 2007, JetBlue Airways operated the first commercial U.S. airline flight with high-speed in-flight email access. Alaska, American, and Virgin America are the only other U.S. airlines to have publicly announced their plans to offer in-flight Internet access. The JetBlue service, which is complimentary, supports only email on two Blackberry devices and Yahoo! Mail and Messenger, using technology developed through the airline’s LiveTV subsidiary. American Airlines and Virgin America plan to offer full web access using Aircell’s air-to-ground system.

Even passengers and crew on business aircraft will soon be able to use their own 802.11b/g equipped WiFi data devices including laptops, PDAs, and BlackBerrys in flight. Aircell broadband is currently expected to be available to general aviation in the third quarter of 2008. This service will be available with Aircell Axxess equipment and is expected to provide DSL broadband speed in a wireless environment.

Inmarsat is another leading space-borne phone service provider and owns and operates a fleet of commercial mobile communications spacecraft, flying in geostationary orbit, 35,786 km (22,240 statute miles) above the Earth.

This includes two of the latest generation satellites, the Inmarsat-4s (I-4s), which were launched in 2005. They currently provide coverage to around 85 percent of the world’s landmass and 98 percent of the world’s population. This level of technology enables service providers to charge subscribers only for data sent and received via packets versus airtime. This makes the traditionally expensive service very cost effective. In some cases existing high-speed data (HSD) equipment can be upgraded to enable the broadband capability.

Inmarsat is also planning to launch a third I-4 satellite in 2008 which will deliver complete mobile broadband coverage of the planet, except for the extreme polar regions.

Data recorders
Data recorders were another thought that crossed my mind as a possible interesting topic.

The Federal Aviation Administration (FAA) has mandated significant upgrades to aircraft cockpit voice and flight data recorders. These improvements will enable investigators to retrieve more data from accidents and incidents requiring investigation.

Under the final rule, which affects manufacturers and operators of airplanes and helicopters with 10 or more seats, all voice recorders must capture the last two hours of cockpit audio instead of the current 15 to 30 minutes. The new rule also requires an independent backup power source for the voice recorders to allow continued recording for nine to 11 minutes if all aircraft power sources are lost or interrupted. Voice recorders also must use solid-state technology instead of magnetic tape, which is vulnerable to damage and loss of reliability.

Airplanes (but not helicopters) operating under Parts 121, 125, or 135 of FAA regulations will have to retrofit some equipment by April 7, 2012. The rule also mandates these enhancements on all newly built aircraft and helicopters after April 7, 2010.

The new rule also requires that the recorders measure aircraft data more frequently and includes the aircraft’s primary flight control movements along with the pilots’ input to the controls. Compliant data recorders must be able to retain the last 25 hours of recorded information.

The final rule formalizes current FAA policy that voice and data recorders must be housed in separate units (excluding helicopters) and that no single electrical failure can disable the units. It does become acceptable for operators who install two combined voice and data recorders to mount one of those combined recorders in the forward part of the aircraft. Details of the final rule can be found at: http://www.faa.gov/regulations_policies/rulemaking/recently_published/.

Prescribed maintenance and testing of data recorders has been somewhat of a vague area especially for general aviation. Advisory Circular AC 20-141 defines a functional check as a quantitative check to determine if one or more features of an item perform within specified limits. When applied to a DFDR parameter, the functional check determines that the recorded parameter is within the limits (range, accuracy, sampling rate, and resolution) specified in the operating rule. The applicant for a Supplemental Type Certificate (STC) must accomplish a functional check for all mandatory parameters for the “first of type” installation testing then must perform the “first of type” installation testing for an FAA approval. During the “first of type” functional check, it may not be feasible to stimulate some sensors to their specified limits. In such instances it is acceptable to simulate the sensor output using suitable test equipment. The operator must include a different functional check in the maintenance program. This maintenance functional check applies to those parameters that can neither be read out during the flight data download, nor functionally checked as part of other aircraft systems. The maintenance functional check may simulate sensor or transducer outputs to check the range, accuracy, resolution, and sampling rate of the recorded data. However, the instructions for continued airworthiness and the operator’s maintenance program must prescribe a periodic functional check of each of these transducers or sensors for accuracy and range.

The Advisory Circular mentioned earlier is in the process of being superseded by AC 20-141A which provides Federal Aviation Administration (FAA) information on certification (design and installation) and continued airworthiness of digital flight data recorder systems (DFDRS). The intent is to enable the National Transportation Safety Board (NTSB) in the United States to conduct more thorough investigations of accidents and incidents. The data recorded is also available to industry to enable the prediction of trends that may be useful in determining modifications needed to avoid accidents and incidents.

Emergency locator transmitters
The Emergency Locator Transmitter (ELT) was another thought for an article topic that came to mind. After all, regulatory mandates have prompted an FAA recommended installation of 406 MHz ELTs because of the pending loss of satellite coverage of the older 121.5 MHz ELTs in 2009. The new 406 MHz ELT design has several advantages over the previous generation and includes more transmitter power, digitally encoded aircraft/owner identification and can provide position information which helps the Rescue Coordination Centers (RCC) either find the aircraft or resolve false alerts. If you install a 406 MHz ELT in an aircraft or purchase an aircraft with a 406 MHz ELT it is important that the device be registered with National Oceanic and Atmospheric Administration (NOAA). To help aircraft owners register their 406 MHz ELTs with NOAA, various FAA Headquarters Internet homepages provide a link to NOAA’s 406 MHz ELT registration web site.

When a distress beacon, whether a marine, aviation, or personal, is detected by a satellite in the U.S. area of responsibility, NOAA processes the alert and forwards the information to the appropriate authorities. In the United States, the U.S. Air Force Rescue Coordination Center (ARFCC) or one of the U.S. Coast Guard Rescue Coordination Centers (CGRCC) will be notified as appropriate.

NOAA has announced the termination of the satellite-based alert monitoring of 121.5 MHz distress beacons in 2009 due in part to the high false alert rate. After that date, the satellite system will only monitor and process 406 MHz distress alerts.

About 99 percent of the 121.5 MHz distress alerts are false transmissions.

Because of this high false alert rate, rescuers normally wait for either extra satellite passes over the alert area or some other verification of a real distress before activating a search and rescue (SAR) response. This delay can mean hours before a SAR mission is initiated. In contrast, the response to a 406 MHz distress alert can be a matter of minutes. The key to this responsiveness is the 406 MHz beacon registration requirement. Since a 406 MHz beacon transmits its own unique digital identification code, the registered owner can be contacted for verification of an actual alert or asked to turn off a faulty 406 MHz beacon.

Well, I hope some tangible ideas for an article come to mind soon as the submission deadline for this issue is rapidly approaching and the earlier feeling of impending doom is growing stronger.

Jim Sparks has been in aviation for 30 years and is a licensed A&P. His career began in general aviation as a mechanic, electrician, and avionics technician. In addition to extensive hands on, Jim created and delivered educational programs for several training organizations and served as a technical representative for a manufacturer of business jets. Currently when not writing for AMT, he is the manager of aviation maintenance for a private company with a fleet including light single engine aircraft, helicopters, and several types of business jets.