Unicom: 10/04


Your July 2004 article, Five Pattern Sins, includes the statement, The classic conflict is the straight-in approach that T-Bones an airplane on base leg which, technically, has the right of way. I dont think the FARs agree.

While the lower aircraft is usually the one with the right-of-way, an aircraft on final approach has the right-of-way over all other aircraft in flight. This means downwind, base and anywhere other than on final.

Final approach is not defined in the regulations; the AIM attempts to define as the leg of the pattern between base and the runway along the runway centerline, but its not a comonly accepted definition. The Pilot/Controller Glossary states that final is when you are aligned with the landing area, a more commonly accepted definition for both VFR and IFR traffic and ATC.

When two or more aircraft are approaching the airport for the purpose of landing, the lower plane has the right of way, but you cant use that rule to cut in front of another aircraft that is on final approach to land. An aircraft on a 2-mile final has the right of way over an aircraft on a 1-mile base per the regulation as I read it. Can you clarify?

-Aaron Michaels
Via e-mail

The articles author, Paul Bertorelli, responds: We agree that this issue is somewhat murky and that the finer points are defined in neither the AIM nor the FARs. The critical consideration is the notion that the aircraft on final shouldnt use the right-of-way to cut off another airplane in the pattern. The example is the aircraft entering a straight-in from three miles out. Does it now have the option of barging into the pattern and forcing everyone else to accomodate? Technically, yes. But common courtesy suggests its not so simple. Our view is that airplanes already in the pattern should enjoy the benefit of the doubt and should not be cut off by the straight-in.


A Probing Question
I agree with Marc Cook (Diagnose the Shakes, August 2004)that a failed engine monitor probe theoretically should display zero. In practice, however, a probe might read anything but zero while failing, as we learned first-hand. Weve had a CHT and an EGT fail on our GEM 602, and both times, the display went off scale just before dying.

The first time it happened, the CHT on #2 was showing 500 degrees passing through 4000 feet on climbout. Even though I immediately reduced power to 15 inches, the CHT stayed high. That should have been a clue, but after 1000 hours of the monitor always being faithful, it never occurred to me it might be lying.

The second time we had a failure, the #2 EGT went off scale, also on climbout. Again I reduced power, but after observing no change in the EGT, no unusual sounds or vibrations and having learned my lesson, I figured the probe was failing. Sure enough, a few minutes later, it dropped to zero.

These engine monitors are fantastic diagnostic tools, and my first impulse is to always reduce power when they indicate a problem. But if the display doesnt change when you reduce power, consider the problem might be with the monitor.

-Mike Palmer
Via e-mail

As someone much wiser and more experienced than me once said, It depends. Ultimately, a completely failed probe will show zero, as your experience demonstrates. What happens between completely working and completely failed is the question, which depends on the failure mode. A loose wire or intermittent ground can show all kinds of other nasty things. Changing power settings and noting the monitors response is the best way to verify a failing probe.


Maintenance Perspective
Regarding the story Top Ten Owner Tips (August 2004), I have to comment from the perspective an aviation maintenance technician. Your comment, Never leave your logs with a shop or mechanic … they are only needed for AD compliance…. is way off-base. Maintenance folks need logbooks for a myriad of issues during an inspection. The following items of importance come to mind: part numbers, model numbers, serial numbers, dates of installation of fuel and oil lines, missing Forms 337, ADs with multiple parts and compliance times, installation of unapproved parts, all sorts of tags, incorrect total times and times since overhaul, verification of work performed by repair stations (they can just list a work order number with no description), etc. Mechanics dont want to continually chase down an owner who is miles away for his logs. And the general condition of them, when brought in, is usually deplorable.

Owner-assisted annuals? Who came up with this idea? The only thing worse than that would be two two-year-old children running loose in a shop. If owners want to accomplish maintenance under the FARs on preventative maintenance, thats great, but they should do it in their own hangar.

-Al Dierdorf
Via e-mail

Well have to agree to disagree on some of this. Clearly, a mechanic must have some way to verify AD compliance, component times, previous work, etc., for which the logbooks are necessary. No issue. But Ive seen more grief over a shop misplacing logbooks or holding them hostage in a dispute than I have annoyance over an owners reluctance to leave the logs at the shop. Owners who want to learn more about their aircraft and how to maintain it should find both the time and the right shop to allow them to assist in their birds annual inspection. Period. They dont have to participate every year, but theres simply no substitute-from an economic or a safety standpoint-for an owner becoming fully involved in his aircrafts maintenance.


More On Learning Weather
I agree that The stormscope and weather radar … should be used only to verify what you already know visually (August Learning Experiences). However, if you fly weather in the summer, visibility may be poor or zero due to clouds.

Experience and ratings probably best determine whether you should be flying a particular weather pattern. If not Instrument-rated, you should not fly instrument weather. Equally important is your attitude-can this flight be delayed?

Being properly prepared makes GA even more enjoyable.

-Bob Eubanks
Via e-mail


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