tribo your question is at the centre of this accident and of many similar incidents.
There are industry wide problems with communication, assumption, and lack of knowledge.
Will the FAA’s failure to conform to ICAO Annex 14 be a contributory factor, or is it the general lack of standardisation for runway condition terminology involved? See
Good - Fair - Poor – Nil and
Braking Action Table.
There appears to be a similar disparity in terminology between ATC, Operator, Dispatch, and Manufacturer (OPC), thus it should not be surprising that there are opportunities for error. In addition there are major issues relating to the accuracy of the runway friction measurement.
There appears to be a lack of knowledge as to what exactly is used to determine landing distance on contaminated runways and what safety margins exist or are required.
Historically the FAA has progressed from dry runways to factored wet, and now recommends an allowance for contaminated. JAA require measured or calculated contaminated data, but the safety margins may not be any better than for wet runways (JAR-OPS 1.520).
The Canadians have identified that a margin of 2.2 or 2.4 might be required to maintain an equivalent level of safety as opposed to the current 1.97 wet factor.
Aircraft Braking Performance on Wet Concrete Runway Surfaces and also see
Benefit-Cost Analysis of Procedures for Accounting for Runway Friction on Landing. The latter PDF document includes the CRFI table and discusses risk and risk assessment (section 4), this is a ‘must read’ for all pilots.
Both the authorities and manufacturers place great responsibility on operators for interpreting the guidelines on landing distance.
Boeing
- If runway is reported to have slush/standing water covering, the flight crew should be suspicious of braking action reports and measured friction
- For landing, Boeing recommends the use of the data labeled ‘poor’ for slush/standing water due to the possibility of hydroplaning
- If runway conditions warrant, review the performance data to ensure the runway length exceeds the expected stopping distance by an adequate margin
There are also many human factors issues. The pilot is normally considered the last point of defense after all other defenses have failed, but for overruns there appears to be very few active defenses upstream of the pilot; it appears that the management of these or opportunity to implement them has already failed.
How to make corrections for landing at a RWY contaminated with snow and ice (more than 25%)? For contamination with wet/slush/risk of aquaplaning, pilots should be balancing their choice of options on at least a safety factor of 2, i.e. double the sum of a ‘sporty’ 1000ft airborne distance from 50ft (landing at the correct speed), plus the published ground roll distance for the conditons. In addition there should be no tailwind or credit for reverse.