Reply to Mike Jenvey
Thanks for that Mike,
I still haven't turned up the stuff I wanted (In paper form...)
In my case (at ZRH) there was a machine, making the protein (blood and guts) type of foam.
We just had a strip 12m wide about where the left wingtip would have touched, had the gear collapsed on that side. We didn't land "in" the foam but nevertheless the inquiries afterwards dredged up some interesting stuff on braking actions etc.
The problems with non protein based foam as mentioned in your link are:
Some of the problems are as follows:
• The difficulty of determining for certain the type of emergency that would lend itself to the practice such as the position and condition of landing gear.
• The time element available for accomplishing the production and distribution of the foam covering that may take up to an hour or more.
• The reliability of information on the landing techniques to be used relating to wind and visibility conditions, pilot experience and skill, visual and radio aids available and the aircraft operational problems.
• The foam-making capability and adequacy of the equipment available. Airports not having adequate equipment should not attempt to lay a foam blanket. If the runway is to be foamed, it is essential that additional supplies of foam are available and the ability of the ARFF service to deal with any concurrent or subsequent aircraft accident must be assured.
• The effect the foam laying and clean-up operations will have upon the aircraft movements at the airport and how this will affect the safety of all aircraft operations in progress.
• The weather conditions during and immediately after the laying of a foam blanket. Foam should not be laid during heavy rain or snowfall conditions.
They don't mention slipperiness and that was what the fire chief quoted.
As regards waiting, we had to wait quite almost an hour too - though the reason was that the spark plugs were out of the laying truck for maintenance reasons! Those guys raced to put the truck together again but never told us - they figured we had enough problems, bless 'em. We used the time to burn off fuel and plan our approach.
I don't think anyone rushes into a non standard approach like that - there is so much to decide - do we arm the spoilers? Have we got hydraulics for the rudder / brakes etc. How will we hold the wing (nose in this case) up and so on, in addition to having the cabin all prepared and the passengers well informed. So the foaming time is not really an issue.
The point about using up the fire fighting foam is also made here - though it begs the question whether it isn't better to avoid the sparks in the first place.
Cheers,
FC.