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AOPA Online Members Only -- AOPA ePilot Custom Content --Vol. 5, Issue 38AOPA Online Members Only -- AOPA ePilot Custom Content --Vol. 5, Issue 38

The following stories from the September 19, 2003, edition of AOPA ePilot were provided to AOPA members who expressed an interest in the particular subject areas. Any AOPA member can receive information customized to their areas of interest by updating their member record file online.

My ePilot - Own/May Own Interest
An aircraft owner who strips the paint off a metal propeller to get a shiny polished prop may end up with an aircraft that's deemed unairworthy instead. That was the unwanted news one pilot got in a recent call to the AOPA Pilot Information Center (800/USA-AOPA or 800/872-2672). Federal aviation regulations require that virtually everything on an aircraft, including propellers, be maintained "at least equal to its original or properly altered condition." Stripping paint off a propeller may alter its corrosion maintenance plan and, therefore, negatively impact its airworthiness according to propeller manufacturers. However, the companies added that a propeller that arrives from the manufacturer with polished metal can remain in that condition. See AOPA Online.

My ePilot - Jet Interest
Bombardier Aerospace said it expects the fleet of Learjet 45 aircraft to be flying again soon. A jet operated by FedEx took off recently at Memphis International Airport. It was among the first to reenter service after being equipped with a new horizontal pitch trim actuator following an airworthiness directive that temporarily grounded the fleet. The entire fleet of some 230 jets will receive new actuators within two weeks, said the company.

My ePilot - Student Interest, Training Tips
Stable air-sounds nice, doesn't it? The mere mention hints at a smooth ride, serene conditions, and the exact opposite kind of atmosphere than the one usually associated with such nasty developments as convection and the turbulence or thunderstorms it can bring.

But not always. In extremely stable air, some interesting things can happen. One is a temperature inversion, for which the National Weather Service offers a definition. In an inversion the air, instead of cooling at or less than a standard lapse rate, actually becomes warmer with altitude. Lapse rates and their relationship to airmass stability are discussed by the AOPA Air Safety Foundation in AOPA's A Pilot's Guide to Mountain Flying . "Most pilots know that an inversion-relatively warm air atop colder air-is stable. It's normally the most stable condition. But, an inversion can actually help to create strong thunderstorms," writes meteorologist Jack Williams in " The Weather Never Sleeps," from the June 2000 AOPA Flight Training. "A day that begins with an inversion but also has the other needed thunderstorm ingredients present is somewhat like holding the lid down on a pot of boiling water."

At the other end of the bad-weather spectrum, stable air and an inversion are often implicated in the development of fog. A good example is valley fog forming in moist conditions in cold air that has flowed downslope and become trapped under warmer layers. "Many times valley fog will hang around for days until the winds of a new storm arrive to scour out the valley," Williams explains in the December 2000 issue of AOPA Flight Training.

Wind and temperature aloft forecasts (FD) may be of some help in predicting inversion conditions over broad areas, when they are used in conjunction with other weather products such as area forecasts (FA). However, FDs do not prognosticate temperatures at 3,000 feet above mean sea level or less than 2,500 feet above a reporting station. Click here to review FDs in Chapter 11 of the FAA's Pilot's Handbook of Aeronautical Knowledge ( click here to download).

Like most weather phenomena, there is both good and bad about temperature inversions as explained in these suggested readings. Stay on the ground when the weather pot is boiling under the inversion. Then enjoy the smooth air of a cool morning-an ideal time to fly!

My ePilot - Training Products
Autopilot Systems, a new CD-ROM from ElectronicFlight Solutions' CompleteLearning Avionics Software Library, is designed to educate users about autopilot systems in general and three in particular: the Bendix/King KAP-140 and KFC-225, and S-Tec 55/X. A goal is to instill conceptual knowledge rather than rote memorization, the company says, so that use of the autopilot can become second nature to the pilot. The CD-ROM costs $195. For more information or to order, see the Web site.

My ePilot - Student Interest, Final Exam
Question: Two months ago I got my private pilot certificate. I recently went up at night for the first time alone. At an unfamiliar airport with no moon, and trees below, the VASI was all I had to tell me I was not going to hit the trees. How do I know I can believe it?

Answer: According to Section 2-1-2 of the FAA's Aeronautical Information Manual, "the visual glide path of the VASI provides safe obstruction clearance within plus or minus 10 degrees of the extended runway centerline and to 4 nm from the runway threshold. Descent, using the VASI, should not be initiated until the aircraft is visually aligned with the runway. The basic principle of the VASI is that of color differentiation between red and white." When you are aligned with the runway's centerline, the VASI indicates your position relative to the glidepath with one of three light combinations-red over white, which means you're on the glidepath; white over white, which means you're above glidepath; and red over red, which indicates you're below the glidepath. Most VASIs are set for a 3-degree glidepath, but at some airports it may be as high as 4.5 degrees to give proper obstacle clearance.

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