Pilots Should Study Runway Condition Reports, Part 3

For obvious reasons it is important for a pilot to have an accurate report on the runway surface conditions to properly perform a Landing Performance Assessment. Unfortunately, the flexibility of business and EMS aircraft to operate into a wide spectrum of airports creates the distinct disadvantage of uncertainty in the runway surface conditions. 

The Flight Safety Foundation’s study of fixed-wing EMS accidents found that critical information regarding runway conditions was not transmitted to pilots in 14 of 36 accidents during landing. 

One of those accidents occurred on Jan. 31, 1995, as the pilot of a Cessna 421 attempted to land at the remote airstrip in Chinle, Arizona.  The airplane was dispatched in day VMC conditions and local police reported that the runway was dry, despite a recent snowstorm. 

On touchdown, the pilot discovered that the runway felt softer than usual, and shortly afterward encountered a dip in the runway that sent the aircraft slightly airborne then off the runway through a barbed-wire fence. The three occupants were uninjured but the aircraft was substantially damaged. The NTSB report noted that although the runway surface appeared dry, there was dry dirt about 1-2 in. deep with a soft layer underneath.  

A Flight Safety Foundation study of business jet safety reviewed 287 NASA Aviation Safety Reporting System (ASRS) reports in which pilots noted problems with runway conditions. Poor runway conditions were cited in 33% of the 287 reports; lack of adequate runway condition reports was cited in 18%. It should be no surprise that contaminated runway conditions were present in 71% of the runway over-run accidents and incidents reviewed in the sample.

Unreported or inaccurate weather conditions and braking reports were factors in a landing overrun at Ohio State University Airport (OSU) airport by the flight crew of a Learjet 23. Light drizzle was reported by ATIS.  No braking action advisories or reports were given. The Learjet touched down in the touchdown zone and the crew immediately applied thrust reversers and spoilers along with maximum braking. Much to their unwelcome surprise, the braking action was nil. As the jet neared the end of the runway, the crew secured the engines, and the aircraft came to a rest 75 ft. off the end. As the pilots waited for emergency vehicles to respond they noted that the ground became covered with clear ice due to freezing rain.
  
What can a pilot do to better prepare for a landing or takeoff given the possibility of uncertainty in the reported runway conditions? In an ASRS report, the Learjet pilot wrote: “If we had more information we would have acted differently. My recommendation is this: if there is any precipitation at all in the winter months, regardless of the temperature, plan on poor braking action at best, replan your landing distance and divert if necessary.” (NASA ASRS Report No. 293469, January 1995.) 

Experience can be an unforgiving teacher. The previous examples illustrate the pitfalls of relying on reports about the runway environment.   This conundrum also applies during dynamic changes in precipitation and winds during thunderstorms, or during heavy snowfall events.  Runway conditions and wind direction can rapidly change from the conditions used to conduct a thorough Landing Performance Assessment just 20 min. prior.
 
Consider The Uncertainties
Aviation training has failed to introduce pilots to the possibility of uncertainty in these reported values. In contrast, it is standard practice in engineering to include possible errors such as instrument error, position error, and reading error into a formal analysis of the uncertainty. A draft report would be (sternly) tossed back if an engineering apprentice failed to perform a formal analysis of the uncertainty.
   
It is also standard practice in engineering to include a safety factor for the unknowns. Our safety factors in aviation can quickly dwindle given the uncertainties and inaccuracies with reported runway environmental conditions. Yes, there are safety margins “sort of” built into the landing performance data for transport aircraft. I purposely use the caveat “sort of” due to the inherent differences in the techniques used by flight test crews to establish the landing distances versus the method used by proficient transport crews in normal flight operations. 

Thus, as you can see, the accurate prediction the effects of wind, temperature and runway surface conditions on takeoffs and landings can be prone to varying degrees of uncertainty. Furthermore, at uncontrolled airports there can be a lack of credibly measured conditions. This further complicates the task of a flight crew attempting to get the most accurate information possible.

Astute flight crews should scrutinize the possible sources of uncertainty when planning a takeoff or landing, contemplate the possibility that the runway environment could be worse than reported, and consider applying prudent safety factors into their decision making.

Pilots Should Study Runway Condition Reports, Part 1: https://aviationweek.com/business-aviation/safety-ops-regulation/pilots…

Pilots Should Study Runway Condition Reports, Part 2: https://aviationweek.com/business-aviation/safety-ops-regulation/pilots…