Policy change expands IFR alternate-airport choices

April 11, 2013

Pilots on IFR flight plans will be able to plan for a GPS-based instrument approach at either the destination or the alternate—but not both—under a policy change that drops the prohibition on choosing an alternate based on a GPS approach.

AOPA has long advocated for measures to expand IFR navigation options for general aviation, and welcomed the announcement as timely when satellite-based procedures now outnumber by 30 percent those using ground-based navaids. That gap is likely to widen with the federal budget sequester making it likely that fewer navaids will be repaired and those that are may take longer to repair after an outage.

The FAA said it based the policy change on a review of requirements for using GPS, and the availability of GPS and WAAS-enabled GPS approach procedures. It concluded that the change should “enable additional flexibility for users” while maintaining safety.

The FAA also broadened allowances for WAAS-equipped aircraft operators to address systems that incorporate a barometric vertical navigation input (VNAV).

Information about the changes was published in the Notice to Airmen Publication edition that became effective April 4. The agency said it was also revising advisory circulars, the Aeronautical Information Manual, and other FAA publications.

In essence, at an alternate airport pilots may now plan for “applicable alternate airport weather minimums using:

  1. Lateral navigation (LNAV) or circling minimum descent altitude (MDA);
  2. LNAV/vertical navigation (LNAV/VNAV) decision altitude (DA) if equipped with and using approved barometric vertical navigation (baro-VNAV)” as set forth in the notam.

“The FAA based this policy clarification on the facts that GPS-based lateral guidance is the same for LNAV, LNAV/VNAV and RNP 0.3 DA and approved barometric vertical navigation equipment does not rely on GPS information. Therefore, a loss of GPS vertical would not affect these WAAS users navigating vertically with baro-VNAV,” it said.

The FAA adopted the policy change and clarification after research showed a “satisfactorily low probability of a missed approach or diversion” and an “even more remote” chance of lost navigation.

The agency stressed that the change “does not alleviate” pilots’ responsibility to comply with regulations regarding instrument flight rules alternate airport weather minima guidance for non-precision approaches.