Safety Publications/Articles

Beyond Pushing Buttons

What pilots really need to know about IFR GPS

We received a thought-provoking telephone call from a designated examiner the other day. He voiced a familiar concern: "How can I evaluate an applicant for the instrument rating who brings an airplane equipped with an IFR-certified GPS?" That's a very good question that pertains to flight instructors as much as it does to examiners.

Some flight instructors are proficient operators of at least one approach-certified GPS, and GPS training is increasingly in demand. But many more instructors have little or no experience with satellite navigation.

Trust me on this: GPS is not like VOR. A substantial commitment to study and practice is required before a pilot can safely use a GPS under instrument meteorological conditions. You can't figure out how to operate these receivers by looking at the panel, and proficiency with one brand by no means guarantees proficiency with any other. The receivers all do essentially the same thing, but how they operate varies greatly among brands and models. As the products evolve and pilots gain experience, GPS should become more intuitive, but, for the moment, flight instructors should specialize in teaching one manufacturer's product. When you're proficient in teaching one unit, you can do a credible job of evaluating performance on the others.

Here's what I told the examiner to help him construct his evaluation plan. CFIs teaching the use of IFR GPS receivers should cover the same points. Instrument pilots should demonstrate understanding of the following basics of GPS:

  • Great-circle track navigation
  • Receiver autonomous integrity monitoring (RAIM)
  • Turn anticipation
  • Flyover and fly-by waypoints
  • Charting differences between NOS and Jeppesen

Instructors must be certain that their students understand how GPS works, how to know whether the navigation information is reliable, and how to comply with approach and missed approach procedures.

Instrument pilots should demonstrate proficiency in the following GPS operations:

  • Programming a waypoint and flying directly to it. This is the core GPS pilot operation. It's surprising how many IFR GPS owners can't - or don't - do anything but fly direct.
  • Holding at a waypoint. GPS is designed to navigate directly from one place to the next in a sequence of waypoints. Once a waypoint is reached, the receiver sequences to the next waypoint. In order to hold, waypoint sequencing must be interrupted. Avoid using published holding points when evaluating pilot performance.

Instructors should simulate ATC instructions to hold on a specific course at a designated fix.

  • Programming an instrument approach procedure. GPS approach procedures consist of a sequence of waypoints stored in the receiver's memory. Pilots must know how to select and arm the approach.
  • Flying a GPS approach procedure from an initial approach fix. This involves selecting the appropriate initial approach fix, navigating to it, and - through a series of waypoints -flying to the missed approach point.
  • Abandoning the procedure prior to reaching the missed approach point and flying vectors to the final approach segment. This is where things can get interesting. Some GPS receivers require considerable button pushing to repeat the approach. You'll want to know that your student can maintain situational awareness, communicate, navigate, and aviate while close to the ground.
  • Flying a missed approach procedure that requires navigation other than direct from the missed approach point to the missed approach holding fix. GPS receivers automatically suspend waypoint sequencing at the missed approach point, so pilots must take some action to sequence the receiver to the missed approach holding point. You must be assured that your students can "Fly runway heading and climb to 4,700 feet before turning left direct to the MAP and hold."

There are many more GPS functions available on today's receivers. Flight plans can be programmed and stored, nearest airports and navaids can be seen, moving maps can be displayed and scaled, and a wealth of airport and frequency information can be accessed. That's all nice-to-know information, but the core operations are the ones that are essential. Proficiency in these will ensure safe GPS navigation.

By John Steuernagle

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