Contaminated Runway Conditions

Mobility Forum, Sep/Oct 2004 by Meintel, Julie

Pop quiz - what is the object of this flying game we play ?

Answer: To get from Point A to Point B to Point C and so on, 'til the mission is complete, and to do it SAFELY!

There are so many facets to flying and operating safely, and they all warrant some consideration.

Landing on or taking off from runways with contaminated conditions are a few of those things that are not under our control as crewmembers. However, it is still crucial that we know what to do when the situation arises.

What is a contaminated runway? Although it sounds like it could be a lot of things, for our purposes here, "contaminated" relates strictly to weather phenomena such as rain or standing water, snow, ice or slush. All of these conditions can greatly reduce an aircraft's acceleration capability by increasing the drag as the tires run through it. This creates the possibility of the aircraft not gathering enough power to make a safe take-off, and it also creates the potential hazard, in the event that the crew would reject the take-off, of not having enough runway left to stop safely.

The FARs, or Federal Aviation Regulations, outline all the rules and safety limitations relating to all types of aviation. The Air Force must also abide by and comply with these rules. FAR 121.195(d) and FAR 135.385(d) both dictate that in the case of wet runways, the landing distance must be at least 115% of the distance required for a dry runway, unless a shorter distance is approved in the AFM (Aircraft Flight Manual). If a shorter distance is provided for in the AFM, it still may not be shorter than the prescribed distance for a dry, clear runway.

In addition, the FARs cited do not specifically refer to other types of contaminated runways, but instead discuss slippery runways. The rules dictate that no extra landing distance is needed over and above that of a wet runway.

What does this mean to an aircrew? And how do they get this information? Base Operations is the base agency that is responsible for reading and determining the level of contamination on a runway, and then relaying that condition, known as RCR or Runway Condition Reading, to crews.

Around the. world, different countries use different methods and measurements to determine the level of contamination, if any, on the runways. There is the James Branke Index, there is the MU-meter, the RCR and others. There is a table in the DOD Flight Information Handbook (pg B27) that puts it all in a clear and easy to read format. It shows how each type of reading relates to one another so that the crew can always understand the true value of the reading they receive.

It breaks down runway conditions into four categories: Good, which is any reading (RCR) above 17; Fair, which is a reading (RCR) 12-17; Poor, which is a reading (RCR) 6-11, and Nil, which is a reading (RCR) of 5 or less.

What do these numbers mean? Simply put, the Runway Condition Reading number correlates to the percent increase in the aircraft's landing roll. This means that based on runway conditions, the more contaminated the runway is, the more concrete you will need to stop your aircraft.

RCR's are reported by Base Operations and added to the hourly aviation weather observations in a coded format: Wet Runway - WR; Slush on Runway - SLR; Loose Snow on Runway - LSR; Packed Snow on Runway - PSR; Ice on Runway - IR; Patchy Conditions (ice, snow or water) - P, and Runway Sanded - SANDED.

Crews need this information so that they may compute and adjust their takeoff and landing data accordingly as the weather conditions dictate. Constant adjustments are sometimes necessary in order to accomplish a safe landing on a less than ideal runway surface.

Another point to consider when making landing preparations is that if a contaminated runway does exist, other factors are likely to come into play. The worse the braking conditions are, the more the crosswind limitations will be reduced. Crews must reference their performance manuals for their type of aircraft to determine exactly how much the limits are decreased.

Got it all figured out? Here's a true story: a pilot was on the last leg of his OME (Operational Mission Evaluation), also known as a checkride. It was an Aircraft Commander upgrade checkride, and the crew was landing at Dover AFB, DE. The pilot in question did not receive the complete weather report and based on incomplete information made a landing on an icy runway where the crosswinds were out of limits, due to the ice.

As a result, the aircraft slid off the side of the runway and the aircraft suffered substantial damage. Fortunately nobody was injured in the incident, but it is safe to say the pilot in question did not pass that particular checkride.

Moral of the story? Check and doublecheck all the information, and make certain you have all the information you need to make the correct decision. Read your manuals, know your aircraft's limitations, and be willing to be flexible enough to make last minute changes when conditions dictate.

Understand how to read the weather reports and know what the RCR readings mean. The most important part of that is to understand how those conditions relate to your aircraft and its capabilities so that you don't push your crew and your aircraft into a position you may not be able to recover from.