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Training Tip: Flight beneath the shelfTraining Tip: Flight beneath the shelf

A student pilot was flying solo in a Cessna 172 beneath an overhanging shelf of Class B airspace, climbing through 3,200 feet msl to 3,500 feet msl, when air traffic control pointed out traffic to the right.

Figure 14-45 of the "Pilot's Handbook of Aeronautical Knowledge" depicting vortex generation. Image courtesy of FAA.

This wasn’t the kind of traffic call that you resolve by spotting the opposing aircraft, reporting it in sight, and maintaining visual separation. The traffic was an Airbus descending through 3,500 feet msl and overtaking the Cessna.

“When I saw the large aircraft at my 3:00 I was instantly concerned about wake turbulence,” the student pilot said, sharing the learning experience with AOPA in an email.

The student pilot’s first impulse was to climb higher than his planned 3,500-foot-msl cruise altitude for some extra safety margin.

But that plan had a major glitch: The overhanging Class B airspace was an uncomfortable, prohibitive 100 feet higher than his intended altitude.

Already apprehensive about a possible wake encounter, the added complication of the airspace configuration threatened to overwhelm the student pilot’s ability to devise a solution.

Then the trainee recalled studying a graphic that depicted the flow field of wingtip vortices; it also noted that vortices descend at several hundred feet per minute. The Aeronautical Information Manual explains that vortices from larger aircraft sink and tend to slow their descent and diminish in strength “with time and distance behind the generating aircraft” and that pilots “should fly at or above the preceding aircraft’s flight path, altering course as necessary to avoid the area behind and below the generating aircraft.”

Recalling the information he had studied made the difference.

“It gave me the confidence to not panic since the Class B shelf in that area is at 3,600,” he wrote. Understanding that leveling off at 3,500 feet would be sufficient to avoid trouble, the student pilot “did just that and had a smooth and uneventful flight.”

Any pilot flying close to Class B airspace should be familiar with the rules for operations in that airspace, even if the flight won’t penetrate its boundaries. For student pilots not seeking a sport pilot certificate or a recreational pilot certificate, that means reviewing 14 CFR 61.95.

Don’t end your prep there. Ask yourself how you would manage scenarios you may have experienced before—weather, instrument or mechanical glitches, low fuel—with a chunk of busy, rigorously controlled airspace complicating decisions you must make.

Dan Namowitz

Dan Namowitz

Associate Editor Web
Associate Editor Web Dan Namowitz has been writing for AOPA in a variety of capacities since 1991. He has been a flight instructor since 1990 and is a 30-year AOPA member.
Topics: Flight Training, Student
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