Does the airport support the cockpit crew to carry out performance calculation?

A runway condition report (RCR) in global reporting format (GRF) is characterised by two distinct features:

  • runway conditions are reported by using runway condition assessment matrix (RCAM) surface descriptions
  • runway conditions are reported for every runway third

This may create a major problem for the cockpit crew. Take-off performance calculation must be based on one single ‘basic’ contaminant representing the complete runway.

Contaminant types used in aircraft performance calculation

In terms of aircraft performance data, seven ‘basic’ contaminants are supported by aircraft manufacturers:

  • ice (cold-dry)
  • compacted snow
  • wet (water equal or below 3mm)
  • water over 3mm depth
  • slush over 3mm depth
  • wet snow over 5mm depth
  • dry snow over 10mm depth

RCAM table contains 18 different surface description types. This creates situations where pilots are forced to convert the RCAM surface description to one of the ‘basic’ contaminant types. This is a potential safety risk.

Pilots may encounter problems

Runway conditions are reported by runway thirds. According to Nordic reports, 14% of runway reports do not present equal conditions on runway thirds.
In the worst-case scenario, pilots may encounter SNOWTAM or ATIS containing multiple surface descriptions for every whole runway. Furthermore, these may be RCAM descriptions not supported by aircraft performance data.

This may create a situation where pilots simply cannot correctly determine one single most significant contaminant to be used in aircraft performance calculation.

To collect original observation data in RCAM format may create a problem

If original runway observation data is collected in RCAM format using RCAM surface description types, the true ‘basic’ contaminant dispersion of contaminants on the runway is lost.
If ‘basic’ contaminant dispersion data is lost, it is not possible to validate one single takeoff significant contaminant representing the whole runway.

Conclusion regarding aircraft performance and RCAM reporting

If an airport is willing to help pilots in aircraft performance calculation, the best way is to provide one significant contaminant, which conservatively represents the whole runway.

To be able to provide this information, original runway condition observation data should be collected using ‘basic’ contaminant types. This allows a proper validation of each contaminant for every complete runway and the calculation of one single take-off significant contaminant (TOSC).

Furthermore, when observations are done by using ‘basic’ contaminant types, the runway inspector’s workflow will remain simple. The runway inspector may focus on observing the ‘old fashioned familiar’ seven contaminants. The RCAM surface description for each runway third can be derived from the input.

Global Runway Reporter application (GRR), TOSC and RCAM

To implement GRF reporting and RCAM assessment in such a manner, that pilots can perform aircraft performance calculation safely, can be accomplished by using the global runway reporter (GRR) application.

The GRR application has inbuilt ‘knowledge’ about aircraft performance. When using GRR, the runway inspector can focus on the essential, which is observing and reporting the seven familiar ‘basic’ contaminants. The GRR application will calculate RCAM contaminants for runway thirds and one single takeoff significant contaminant (TOSC) representing the complete runway.