A320ajm
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Foaming Runways - Emergency Landings

Sun Oct 21, 2012 1:34 pm

After reading an avherlad article (http://avherald.com/h?article=4157d291/0001&opt=0) about an aircraft with landing gear failure, I noticed in the picture caption that the Airport FRS had foamed the runway. I remember seeing this in films about aircraft disasters when I was younger, but how common is it?

Thanks,
A320ajm
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tdscanuck
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RE: Foaming Runways - Emergency Landings

Sun Oct 21, 2012 7:06 pm

Quoting A320ajm (Thread starter):
I noticed in the picture caption that the Airport FRS had foamed the runway. I remember seeing this in films about aircraft disasters when I was younger, but how common is it?

They tend to do it as soon as the aircraft comes to a stop. A Lear came down at Boeing Field a few years ago with their nose gear stuck sideways. They came to a smoky stop about mid-runway, at which point the Boeing Fire department turned the place into a foam party for about 100m in every direction.

Tom.
 
arffdude
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RE: Foaming Runways - Emergency Landings

Sun Oct 21, 2012 7:33 pm

Overall I'd say it's fairly rare. There are several reasons for this.

First, foam is expensive. A five gallon drum is about $100 to $200 depending on the concentration (either 3% or 6%, 1% is not allowed for ARFF purposes). Note that that's the pure foam, which will yield much more than 5 gallons when mixed in with water. If I remember correctly, the Striker 1500 fire truck holds about 200 gallons of pure foam, so you're talking between about $4,000 and $8,000.

Also, it takes a long time to refill. So say that you foam one portion of the runway, but the plane doesn't land exactly there, or it skids off onto another unfoamed section. If you spent all your foam already, well now you don't have any left over for the actual crash.

This is an interesting quick read on the subject here. The FAA specifically warns against attempting to foam a runway with Aqueous Film Forming Foam (AFFF), which is the style of foam most widely used (by a very large margin, I would imagine), in ARFF trucks.
 
qblue
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RE: Foaming Runways - Emergency Landings

Sun Oct 21, 2012 8:27 pm

The other inconvenience would be the time required to clean the foam, you would need to wash the runway several times to get rid of the foam, Foam is slippery and not really environment friendly.
 
rfields5421
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RE: Foaming Runways - Emergency Landings

Mon Oct 22, 2012 2:43 am

Foam also isn't traction friendly to emergency vehicles or rescuers. The slippery stuff can make it more difficult to get help to the right place. Foam can make it harder for pax evacuating an aircraft to get away from danger.

If there is an actual fire or smoking metal, tires, brakes, etc - foam is great to smother it. And knocking down the fire or parts hot enough to smoke is the first priority.
 
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HAWK21M
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RE: Foaming Runways - Emergency Landings

Mon Oct 22, 2012 7:25 am

Reduction of friction is the bad side of foam.................
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L-188
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RE: Foaming Runways - Emergency Landings

Mon Oct 22, 2012 10:26 pm

No point in foaming the runway if you are just going to cause the airplane to run off the end into the apprach lights.

Its better to wait to see if you gave a fuel leak and then foam the puddle to keep it from lighting off.
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HAWK21M
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RE: Foaming Runways - Emergency Landings

Tue Oct 23, 2012 10:02 am

Quoting L-188 (Reply 6):
No point in foaming the runway if you are just going to cause the airplane to run off the end into the apprach lights.

Its better to wait to see if you gave a fuel leak and then foam the puddle to keep it from lighting off.

Also predicting the location where foam would need to be sprayed in advance will be very tough.
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