Originally Posted by Wing Commander Fowler
Oh Joy - so all the data used to determine whether it's safe to land is cr*p then?
The most surprising aspect might be that so many pilots do not know this, or do not understand the risks that are currently accepted.
More recent research is here with links to the report TP 14273
Falcon 20 aircraft braking performance on wet concrete runway surfaces.
“On a smooth, wet concrete runway surface close to the minimum maintenance standard, … the current operational dispatch factor of 1.92 for turbojet aircraft landing on wet runways at destination or alternate airports would have to be increased to a value of 2.2 to 2.4 in order to achieve the same level of safety as that which is currently accepted for dry runway operations”.
I interpret the reported data as indicating that where with current calculations an aircraft should stop, using max braking, with 40% of the runway remaining. In reality on some runways, this safety the margin is significantly less. Then add to this the actual braking level used in wet conditions, the variability of runway surfaces and maintenance condition, rubber deposits, cross wind, water damming, long and/or fast landings, etc. Then we start to consider contamination … !
“For landings on wet runways, the excess distance between the landing field length, calculated using the current method, and the actual landing distance was considerably less than the excess distance on dry runways.
TheOddOne See the values of friction test measurements for wet runways in the report (table 2); note for a ‘tanker’
(a more realistic) wet runway, all values of mu are well below 0.7, then compare these with the actual, even lower values as experienced by aircraft (figures 10 & subsequent).
Short Approach? If data is “unreliable” then why broadcast it. The figures may only serve to bias the crew’s judgment.
Humans are the weakest link in winter operations, the pilots the last link. If due to lack of information or poor understanding, our judgment can be so flawed then there should only be one option in the decision making process; don’t consider landing.
We might seek to blame others or equipment for the hazards of winter operations, but do we (pilots) really consider the risks involved with landings on contaminated runways.
There are few if any hard limits, like a low vis approach ban. Perhaps the runways should be closed until cleared, or why not consider undersurface heating like sports grounds. I am sure that those operators who have suffered cost and disruption due to accidents would be prepared to pay a small premium to support these initiatives.
Also see thread
Good - Fair - Poor – Nil
”Attempts to land on heavily contaminated runways involve considerable risk and should be avoided whenever possible. If the destination aerodrome is subject to such conditions, departure should be delayed until conditions improve or an alternate used.
Operations from contaminated runways, by all classes of aeroplane, should be avoided whenever possible” (UKCAA AIC 61-99)
Flight Safety Foundation. Managing threats and errors during approach and landing.