What might be obvious to some people can be overlooked by others.
For example, the 10,300ft (3139m) long runway only provides a landing distance of 8,563ft (2610m) beyond the displaced threshold.
The approach path is slightly steeper than normal – requiring a higher vertical speed which adds to the already higher VS resulting from the high ground speed at the 10,000 ft altitude.
The ILS t’hold crossing ht (TCH) is higher than the visual ht, which together with the higher grnd speed tends to extend the flare before touchdown, probably resulting in a longer landing than with standard techniques (2500ft per 10kts, plus 200ft per 10ft above TCH; AC91-79).
There is no correlating visual glideslope when approaching on the ILS, – crews should not attempt to duck under as this can destabilise the approach – and an even higher VS.
Some not-so-obvious items are identified in a recent Norwegian report “
… incidents involving slippery runways occur because the involved parties do not realize that the existing rules and regulations are based on a simplification of the actual physical conditions.”
An example of this might be the erroneous assumption that wet runway performance is reasonably consistent. The wet landing distance is only an approximation and even with certification factors the actual safety margin in comparison with a dry runway may be less; and in some conditions very much so, even none. Consider the difference between wet and contaminated data; compare the wet landing distance on a 2.5 mm water depth ‘wet’ runway, with 3.0 mm depth – what if the reported conditions ‘overlook’ these details - "what if".
Then consider the condition of the aircraft tyres (
“… tread designs tend to lose their drainage capability when the tread is approximately 80 percent worn”. Horne NASA). There may be similar issues with the runway surface; it might be grooved but are the grooves worn, blocked, or the surface contaminated with rubber. How long does it take a runway to drain aftyer a heavy rain storm, how long can an aircraft hold-off before landing.
Of course, for those who have been off-the-end of the runway (now looking over the shoulder at the emergency vehicles arriving), all of the above is obvious, but why wasn’t it obvious during the pre landing briefing.
NASA Wet Runways (Horne)
http://www.skybrary.aero/bookshelf/books/1492.pdf (and 1493, 1494)