GRF regulations demand knowledge on aircraft performance. Contaminant selection and runway condition code (RWYCC) assessment are based upon a trained person’s judgement considering the effect on aeroplane performance. In this context, the trained person refers to the runway inspector responsible for runway condition reporting.
Are you familiar with aircraft performance?
What is the difference between take-off and landing performance? Should runway inspector selection in the runway condition assessment matrix (RCAM) table be based upon take-off or landing-critical contaminant? Are these two choices contradictory?
Short lesson on take-off and landing performance
In terms of aircraft performance, take-off and landing are two totally different events. In the first, two scenarios must be considered: continued and aborted take-off. In continued take-off, contaminant drag must be taken into account. It plays the utmost important role and may have a significant effect on aircraft acceleration and thus required runway length.
In aborted take-off, low-friction impacts aircraft performance by lowering the aircraft’s stopping capability. Therefore, all ‘basic’ contaminant types have built-in regulatory friction coefficients. Aircraft manufacturers use these friction values when calculating aircraft behaviour in aborted take-off. RWYCC value is not used as a parameter in aborted take-off calculation.
Note: Take-off performance calculation is solely based upon contaminant type and depth and has nothing to do with the reported runway condition code RWYCC value.
In landing, contaminant drag is considered credit, which is not taken into account. In the flight planning phase, landing performance calculation is based on contaminant type and depth. When airborne, pilots are calculating landing performance shortly after the top of descent. This is called an ‘in-flight’ calculation. ‘In-flight’ calculation can be based solely on RWYCC value.
Note: One step too high RWYCC value report may ‘eat’ the 15% margin.
Conclusion regarding aircraft performance and RCAM table assessment
RCAM table was originally designed to support runway condition assessment from a landing performance point of view. That is why RWYCC value plays a major role in the assessment, but no role in take-off performance. To safely cover both take-off and landing, the runway inspector should choose the RCAM contaminant as having the greatest impact on take-off performance and the RWYCC value as having the correct effect on landing performance.
Note: The runway condition report (RCR), SNOWTAM and ATIS should serve both take-off and landing.
To safely cover take-off and landing, reporting may be required in certain runway conditions where the RCAM contaminant type and its respective (nominal) RWYCC value cannot be ‘locked’ and an RWYCC downgrade procedure should be applied.
Global Runway Reporter application (GRR), aircraft performance and RCAM
To safely implement GRF reporting and RCAM assessment requires a profound understanding of aircraft performance in respect of both take-off and landing. Global runway reporter (GRR) has built-in ‘knowledge’ about aircraft performance and GRR offers great relief for the runway inspector in respect of aircraft performance consideration during runway condition observation, RCAM assessment and reporting. When using GRR, the runway inspector can focus on the essential: observing the seven ‘good old familiar’ contaminants. Based on the runway inspector’s input, GRR will take care of take-off critical RCAM contaminant generation and landing critical RWYCC-value tracking. The best possible real-time guidance is given to the inspector to carry out a safe RWYCC assessment.