American Airlines DC9 landing incident at O'Hare
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FOAMING OF RUNWAYS...definitive answers to:
This cert alert gives updated AFFF user guidelines in the following areas:
1. Aqueous Film Forming Foam (AFFF) - less than 3% Concentration
AFFF in concentrations less than 3% is not acceptable to the FAA for use on airports.
The 1% concentrate that is available should not be used in ARFF applications because of the difficulty in consistently providing an accurate mixture. Any attempt to use 1% foam would necessitate the installation of a computer-controlled system and each load would have to be checked carefully. There are other means of proportioning but they are not accurate at low percentage proportioning settings. Experience and testing have shown there is no consistency between different loads. Also, at low concentration, there is no room for error on the fire ground. If a mixture is discharged on the lean side, the result is plain water being applied to a fuel fire. The opposite of lean can be problematical also, because at 2% (only 1% off), you are consuming concentrate at twice the designed rate.
2. Use of Alcohol Type Foams
The FAA does not approve the use of alcohol type foams in ARFF vehicles on airports and part 139 does not provide for substituting Aqueous Film Forming Foam (AFFF) with alcohol type foams.
Alcohol type foams are typically used by city and industrial fire departments because they are effective on both hydrocarbons, such as gasoline, and polar solvents such as alcohol. They have to carry only one type of foam on their trucks if they use alcohol type foams. These foams are labeled AFFF/ATC or Alcohol Resistant AFFF, which gives airport operators and firefighters the impression that the foam is okay for airport use. We are aware of several airport ARFF stations using alcohol type foams because the foam was ordered using city fire department specifications for ATC/AFFF.
The following problems are associated with the use of alcohol type foams on an airport. Alcohol type foams are usually not compatible with AFFF currently in use at airports, and ARFF vehicles cannot proportion alcohol foams correctly without changes in the mechanical proportioning systems. Also, a special additive to the alcohol foam can produce, over time, a scale that can form in and obstruct the metering valves on truck foam systems.
3. ARFF Foaming of Runways for Emergency Landings
The FAA does not recommend the foaming of runways for emergency landings and warns against the practice with any foam other than “Protein” foam. Fluroprotein foam, film forming fluroprotein foam, and aqueous film forming foam are not considered suitable for runway foaming operations due to their short drainage time. It is recommended that ARFF personnel decline to foam a runway when requested by a pilot because they do not have the specialized equipment and protein foam
The effectiveness of runway foaming is not fully substantiated by the real evidence of operational incident studies. Neither the International Fire Service Training Association (IFSTA) nor the National Fire Protection Association (NFPA) recommends the practice. The International Civil Aviation Organization (ICAO) Airport Services Manual Part 1, Rescue and Fire Fighting, Third Edition - 1990, contains a chapter (Chapter 15) on foaming runways for emergency landings. The chapter addresses the theoretical benefits from foaming runways, but then describes the shortcomings of those benefits. It also describes operational problems that should be evaluated to determine the feasibility of foaming a runway.
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.
Techniques of runway foaming differ, depending on the numerous variables involved. Without the proper equipment, training and material, the desired effectiveness of the practice will be difficult to achieve. Foaming a runway can also result in the airport fire department being short of agent at a critical time, if the firefighters are involved in fire suppression after the landing.
This cert alert gives updated AFFF user guidelines in the following areas:
1. Aqueous Film Forming Foam (AFFF) - less than 3% Concentration
AFFF in concentrations less than 3% is not acceptable to the FAA for use on airports.
The 1% concentrate that is available should not be used in ARFF applications because of the difficulty in consistently providing an accurate mixture. Any attempt to use 1% foam would necessitate the installation of a computer-controlled system and each load would have to be checked carefully. There are other means of proportioning but they are not accurate at low percentage proportioning settings. Experience and testing have shown there is no consistency between different loads. Also, at low concentration, there is no room for error on the fire ground. If a mixture is discharged on the lean side, the result is plain water being applied to a fuel fire. The opposite of lean can be problematical also, because at 2% (only 1% off), you are consuming concentrate at twice the designed rate.
2. Use of Alcohol Type Foams
The FAA does not approve the use of alcohol type foams in ARFF vehicles on airports and part 139 does not provide for substituting Aqueous Film Forming Foam (AFFF) with alcohol type foams.
Alcohol type foams are typically used by city and industrial fire departments because they are effective on both hydrocarbons, such as gasoline, and polar solvents such as alcohol. They have to carry only one type of foam on their trucks if they use alcohol type foams. These foams are labeled AFFF/ATC or Alcohol Resistant AFFF, which gives airport operators and firefighters the impression that the foam is okay for airport use. We are aware of several airport ARFF stations using alcohol type foams because the foam was ordered using city fire department specifications for ATC/AFFF.
The following problems are associated with the use of alcohol type foams on an airport. Alcohol type foams are usually not compatible with AFFF currently in use at airports, and ARFF vehicles cannot proportion alcohol foams correctly without changes in the mechanical proportioning systems. Also, a special additive to the alcohol foam can produce, over time, a scale that can form in and obstruct the metering valves on truck foam systems.
3. ARFF Foaming of Runways for Emergency Landings
The FAA does not recommend the foaming of runways for emergency landings and warns against the practice with any foam other than “Protein” foam. Fluroprotein foam, film forming fluroprotein foam, and aqueous film forming foam are not considered suitable for runway foaming operations due to their short drainage time. It is recommended that ARFF personnel decline to foam a runway when requested by a pilot because they do not have the specialized equipment and protein foam
The effectiveness of runway foaming is not fully substantiated by the real evidence of operational incident studies. Neither the International Fire Service Training Association (IFSTA) nor the National Fire Protection Association (NFPA) recommends the practice. The International Civil Aviation Organization (ICAO) Airport Services Manual Part 1, Rescue and Fire Fighting, Third Edition - 1990, contains a chapter (Chapter 15) on foaming runways for emergency landings. The chapter addresses the theoretical benefits from foaming runways, but then describes the shortcomings of those benefits. It also describes operational problems that should be evaluated to determine the feasibility of foaming a runway.
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.
Techniques of runway foaming differ, depending on the numerous variables involved. Without the proper equipment, training and material, the desired effectiveness of the practice will be difficult to achieve. Foaming a runway can also result in the airport fire department being short of agent at a critical time, if the firefighters are involved in fire suppression after the landing.
N244AA does suffer with nose gear collapses - it has a previous incident at ORD when, after a complete hydraulics failure, it landed and veered off the runway, hitting a manhole cover which collapsed the nose gear. 12 September 1989 I saw it happen (NTSB site has more details)
ex-Tanker
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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.
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.
Originally Posted by paulc
N244AA does suffer with nose gear collapses - it has a previous incident at ORD when, after a complete hydraulics failure, it landed and veered off the runway, hitting a manhole cover which collapsed the nose gear. 12 September 1989 I saw it happen (NTSB site has more details)
Would you happen to have a link to this specific incident you mentioned?
I went to the NTSB site and was unable to locate the report. I'd really like to read the details of that.
Thanks.
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ORD landing
I was flying the CBS news helicopter and have to hand it to the crew for getting their ship on the ground successfully. All of the news helicopters were held outside the surface area by the tower which explains the long distance picture (5 miles). Fly safe.
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Originally Posted by jondc9
I read somewhere that some planes had a ground sensing mechanism on the nose strut to make sure the nose wheel was on the ground prior to thrust reverser deployment? do you know if AA had it that way?j
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captjns:
the question was specifically meant to determine whether the version of the super 80 that american flys is so equipped.
the dc9 was not equipped.
the 737 is equipped.
the question is about the md80 as operated by american
the question was specifically meant to determine whether the version of the super 80 that american flys is so equipped.
the dc9 was not equipped.
the 737 is equipped.
the question is about the md80 as operated by american
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Originally Posted by EAL747
I am not potshotting the crew of AAL; my comment is just to always evaluate any possibility outside what the FAA and company manual dictate. That's what we're paid for......
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Originally Posted by jondc9
hi justanotherwindscreen:
I flew the nine but never the -80. in the 9 we could deploy thrust reversers inflight ( not legally of course!!!!) is there any logic or interlocks to prevent that in the super 80? also, I read somewhere that some planes had a ground sensing mechanism on the nose strut to make sure the nose wheel was on the ground prior to thrust reverser deployment? do you know if AA had it that way?
j
I flew the nine but never the -80. in the 9 we could deploy thrust reversers inflight ( not legally of course!!!!) is there any logic or interlocks to prevent that in the super 80? also, I read somewhere that some planes had a ground sensing mechanism on the nose strut to make sure the nose wheel was on the ground prior to thrust reverser deployment? do you know if AA had it that way?
j
Last edited by JustAnothrWindScreen; 24th Jun 2006 at 13:16.
Originally Posted by JustAnothrWindScreen
It is my understanding that nothing prevents the thrust reversers from being deployed in the air other than the pilots not doing that.
That's why you pull c/b s-28 or t-28 for three seconds when you get a reverse accumulator low message/light in flight. To bypass ground shift, open the isolation valve and allow sytem pressure to briefly recharge the system.
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bafanguy
Not laughing at you but with you bafanguy. Maybe when I was younger I might have added more details, well, I don't know if I would even have done it then. But, really the only thing that stops them from going into reverse in the air are the pilots not doing it. I remember the World War II ace and Viet Nam fighter pilot Robin Olds said that one of the main reasons he shot down so many aircraft was that he never looked at the instruments. I have about 18000 hours on the DC-9 variants but have always found it annoying to talk about valves and CBs and such. One of the great things about this biz is that it is made up of so many different types of folks that all seem to get the job done amazingly well.
Not laughing at you but with you bafanguy. Maybe when I was younger I might have added more details, well, I don't know if I would even have done it then. But, really the only thing that stops them from going into reverse in the air are the pilots not doing it. I remember the World War II ace and Viet Nam fighter pilot Robin Olds said that one of the main reasons he shot down so many aircraft was that he never looked at the instruments. I have about 18000 hours on the DC-9 variants but have always found it annoying to talk about valves and CBs and such. One of the great things about this biz is that it is made up of so many different types of folks that all seem to get the job done amazingly well.
Originally Posted by JustAnothrWindScreen
bafanguy
but have always found it annoying to talk about valves and CBs and such. One of the great things about this biz is that it is made up of so many different types of folks that all seem to get the job done amazingly well.
but have always found it annoying to talk about valves and CBs and such. One of the great things about this biz is that it is made up of so many different types of folks that all seem to get the job done amazingly well.
I hear ya...never gave the valves & c/b thing much thought. It was just part of the game.
