Quiet Flight ANCS
After a long flight, it takes awhile before you really stop moving. The hours of absorbing vibration from the engine and propeller leave our bodies tired and our minds in a fog. Though we identify high-frequency noise as a fatigue-inducing culprit and use all manner of noise-reducing headsets and insulation to rid ourselves of it, we often fail to recognize the low-frequency vibration that also saps us of energy. When a teenager pulls up next to you in his car, radio booming, you feel the bass in your chest. In an airplane, another kind of heavy-metal band is rocking under the cowl, and you're sitting in the front row.
Quiet Flight, in conjunction with Cooper Tire and Rubber's Engineered Product Division, is installing a noise-reduction system in light aircraft that promises to reduce this low-frequency noise. In 1999, AOPA Pilot reviewed the system in its initial installation in a Cessna 210 (see " Pilot Products," October 1999 Pilot). The system quiets the cabin through the same process by which other active noise reduction (ANR) products attack noise.
A microphone samples the current ambient noise and sends the sound waves to a computer for analysis. The waves peak at certain low-end frequencies, between 75 and 300 Hz, which the computer identifies. Then the system generates a mirror image of the wave, effectively nullifying the wave at that frequency. Since there are only a few peaks that are relatively strong compared to the rest of the sound waves present, the system need only focus on a few frequencies in order to quash most of the noise. The nullifying waves are broadcast through speakers located near each seat, creating a quiet zone about three or four feet in diameter centered roughly on each headrest.
We recently flew in Quiet Flight's Cessna 310 with the active-noise canceling system (ANCS) installed. The system consists of a computer weighing roughly 10 pounds and several speakers, depending on the number of seats. The speakers are mounted in the headliner above the seats, in the cabin walls, or in the headrests themselves. For the 310, four speakers with a combined weight of about 20 pounds are installed in the headliner. The system is controlled by an On/Off switch on the avionics bus. After the pilot turns the ANCS on, that's it. All noise cancellation is automatically accomplished, much like using an ANR headset.
The ANCS is optimized for an individual airplane. Since all engines create a slightly different noise signature — as do props and exhaust systems — each ANCS is unique. The company has authorized several service centers nationwide to complete the installations. The ANCS in 310s takes about 30 hours to install.
Throughout the hour-long flight, we cycled the ANCS on and off, testing various headsets, both passive and ANR, to determine what benefit the system produced, and how it compared to headsets alone. Initially, when the ANCS is turned on, you cannot tell much of a difference. Dean Rushfield, engineer and demo pilot for Quiet Flight, compared it to how your eyes adapt to a dark room. All of your senses adapt in this way — when you cook dinner with a lot of garlic, you lose sense of its strength after awhile.
When Rushfield flicked the switch off, the change was dramatic — the engine and prop thundered again. Rushfield wears a nonattenuating headset regularly; we found that noise levels were acceptable in the 310 without a headset, even better with an old passive headset, and best with one of the ANR models. A perfect match is made in this case, as the ANR set cancels the high-frequency noise and the ANCS shuts down the low.
Another cool thing about the ANCS is that it's constantly working to optimize the nullifying waves that it generates. Say you fly through some turbulence. You can hear the wobble in the noise signature as the system adapts. Overall, Quiet Flight estimates an 8- to 12-decibel reduction — and keep in mind that a 6-decibel reduction equates to a 50-percent reduction in sound pressure or noise.
The ANCS on a typical Cessna 310 costs $6,995 and the system ranges from $4,995 for a Cessna 210 up to $14,995 for a cabin-class turboprop; systems have been installed on more than 16 models of single-engine, piston-twin, and turboprop airplanes. For more information, contact Quiet Flight LLC, 3901 Stanford, Dallas, Texas 75225; telephone 214/739-2688; or visit the Web site ( www.quietflight-llc.com).
How Radar Works
Airborne weather radar is probably the most misunderstood piece of avionics on the aircraft. Operated and interpreted properly, weather radar can be a vital tool in thunderstorm avoidance. But there's a flip side, and it's a big one: Most pilots never learn the right way to work radar. These pilots may have the means of avoiding storm cells, but they don't know enough to do so.
Those who study Capt. David B. Gwinn's How Radar Works shouldn't find themselves among that crowd. Available from Sporty's Pilot Shop, this product consists of an information-packed booklet and a 66-minute audio CD. The booklet discusses all the essentials in an easy-to-read, heavily illustrated format, and includes radar antennas, radar energy characteristics, antenna tilt control, and hazardous radar signatures. The CD provides a formal lecture that further details the concepts depicted in the booklet. It's like sitting in on an advanced ground school session on radar — Gwinn, a retired TWA captain, is a weather radar educator. You too can benefit from his decades of on-the-job experience.
Price is $49.95; save $2.50 by using your AOPA credit card. For more information, contact Sporty's Pilot Shop, Clermont County Airport, Batavia, Ohio 45103-9747; telephone 800/543-8633 or 513/735-9000; fax 513/735-9200; or visit the Web site ( www.sportys.com). — Thomas A. Horne
Navgps moving-map software
A number of good moving-map programs exist for personal digital assistants (PDAs), and one that just got a nice upgrade is Navgps.
Navgps comes in two flavors, Navgps Basic, version 2.4a, and Navgps Pro, version 3.0c. The Basic software offers a full-color moving-map screen displayed on the PDA that shows flight-planned routes, airspace, navaids, fixes, and airports. The pilot can choose from a 120-degree arc heading presentation or a horizontal situation indicator presentation with the present course as well as data blocks with altitude, distance, estimated time en route, and groundspeed. The Pro software adds worldwide topographical data, and the display has been optimized for a faster update rate. Flight planning with the Pro version also lets you use airways in your route. Both versions allow user-defined waypoints so that any airports or navaids not included in the database can be added.
The software requires a color PDA running the PocketPC operating system. The display is clear and attractive, and refresh rates are good enough so that you can use the heading information to fly a course well. The flight-planning functions are simple, and editing a flight plan once it is entered is straightforward. The fact that this is a mature product shows. The software is compatible with a variety of GPS antennas and in-panel GPS receivers; we had the best luck with a Garmin 35 unit that plugs into an auxiliary power source and has an antenna that can be mounted anywhere — handy for pilots who rent or switch aircraft often.
Navgps Basic retails for $74; the Pro version is $124. A current aviation database is available for $8; both versions use this data. The software is purchased through two PDA Web sites ( www.handango.com and www.pocketgear.com). For more information, contact Navgps via the company Web site ( www.gonavgps.com) or by e-mail ( [email protected]).
Unless otherwise stated, products listed herein have not been evaluated by AOPA Pilot editors. AOPA assumes no responsibility for products or services listed or for claims or actions by manufacturers or vendors. However, members unable to get satisfaction regarding products listed should advise AOPA. To submit products for evaluation, contact: New Products Editor, AOPA Pilot , 421 Aviation Way, Frederick, Maryland 21701; telephone 301/695-2350. Links to all Web sites referenced in this issue can be found on AOPA Online ( www.aopa.org/pilot/links.shtml).
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