Landing Performance is in the FAA’s Crosshairs
- Dan Boedigheimer
When I downloaded the AC, the first thing I noticed was it did not grow in length. Identical to the original publication, AC 91-79A is still 39 pages long. My assumption based on the same page count was the changes were going to be minimal. A closer attention to detail reveals the changes were significant. Because the FAA does not provide a record of revision or change bars indicating what changed, it can be challenging to understand the intent of the revision.
Advanced Aircrew Academy personnel did a page-by-page, word-for-word review of the two documents, assessing what needed to be updated in our online courseware. Because of the unique and industry-leading content delivery system we use from Aerostudies, our Winter Operations / Surface Contamination and Runway Excursion online training modules have already been updated with the revised guidance from the FAA. If you are one of the hundred operators that will be receiving our Winter Operations / Surface Contamination module October 1st, rest assured you are receiving the most up-to-date relevant information of any eLearning provider.
Highlight of Changes to AC 91-79A
There is always the debate that Advisory Circulars are “advisory in nature” and the information in ACs is not regulatory. The FAA has attempted to narrow that gap with a new statement in AC 91-79A. “NOTE: This guidance pertains to the preflight planning requirements of Title 14 of the Code of Federal Regulations (14 CFR) part 91, §§ 91.103, 91.1037, and 91.605; part 121, § 121.195; and part 135, § 135.385.” Business aviation operators should take note that a review of your Operations Manual guidance related to information in the AC would be a prudent task. It is doubtful the FAA will come knocking on your door, but your Safety Management System (SMS) should identify this change as a proactive step to assess how it affects your operation.
There has also been strong language added to the AC “urgently” recommending operators develop a procedure for a landing assessment at time of arrival. That assessment should include a safety margin added to the adjusted landing distance that “the FAA considers a 15 percent margin to be the minimum acceptable safety margin” and “except under emergency conditions, flight crews should not attempt to land on runways that do not meet the assessment criteria and safety margins.”
Eight additional related reading material references were added, including 2 SAFOs, Flight Safety Foundation’s ALAR Tool Kit, and the Pilot’s Handbook of Aeronautical Knowledge.
Six additional hazards associated with runway overruns were identified and discussed, including High Airport Elevation, Landing Weight, Downhill Runway Slope, Excessive Height Over the Runway Threshold, Delayed Use of Deceleration/Maximum Braking, and Landing with a Tailwind.
There were two added definitions for Declared Runway Distance and Landing Distance Available (LDA) and 10 definitions removed that were included in the original AC 91-79. The table for Braking Action Definitions was changed for AC 91-79A to “Operational Runway Condition Assessment Matrix (RCAM) Braking Action Codes and Definitions.” They removed Mu values and added Deceleration or Directional Control Pilot Observation criteria to the table.
In the Stabilized Approach section, they made edits to each item and added two new ones, touchdown point and downhill runway slope. Two tables were added to the section, Rates of Descent Estimate Concept and a Sample Computation for a downhill runway slope.
The Discussion of Landing data section was revised to include information for small airplane operations on unpaved runways, minimum landing distance prediction, the effect of wind on landing performance, and use of flaps. The Landing and Braking Technique section had some edits to the braking section with discussion on aerodynamic braking, wet and contaminated runway surfaces, and autobrakes. The summary section was significantly reduced in the revised AC.
There were only minor changes to Appendix 2: Regulatory Considerations and Recommended Operational Practices. An example of how to apply the 60% rule in air carrier operations was removed.
Appendix 3: Certification Considerations – Landing Distance Data from the original AC 91-79 was removed in the revision. Appendix 3 in AC 91-79A is Operational Awareness of Wet and Contaminated Runways Landing Distance Data, which contains the information that was in Appendix 4 of the original AC. Most of the information remains the same. Some tables that were in the body of the original AC were moved to Appendix 3 in the revision.
Appendix 4 is new to AC 91-79A. It includes an unstablized approach case study.