Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
joejohn
Topic Author
Posts: 2
Joined: Tue Jan 07, 2020 3:46 pm

Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 2:53 am

hello

this is my first post. I used to belong to a generic science forum and drove the people there crazy with all my airplane questions and they recommended that I join here. I was not happy there either because it was just people who had studied physics but didn't have real life experience with airplanes.

my first question to the forum:
there is a video on youtube, it's called
"We Are Going To Crash Land!" | Flights From Hell | Channel 5

flight from LAX to NY. the landing gear has rotated at the beginning of the flight so the pilots are trying to figure out what to do. They fly around for 4 hours to burn fuel. They land and the landing gear catches fire.

1) why fly around for 4 hours to burn fuel? why not just fly to NY to burn the fuel, and worry about the problem in NY?
2) why not put some foam on the ground, or water, before the airplane lands so the landing gear doesn't catch on fire?
 
GalaxyFlyer
Posts: 7004
Joined: Fri Jan 01, 2016 4:44 am

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 3:24 am

Is the gear retracted or hanging? If it’s still extended lots of considerations about continuing. Foam has proven to be not very effective at preventing fires in gear up landings and unnecessary. How, you ask? By studying unintentional gear up landings and there was no or negligible fire breakout.
 
User avatar
Starlionblue
Posts: 20483
Joined: Fri Feb 27, 2004 9:54 pm

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 3:52 am

This was the JetBlue A320 at LAX. .Flight 292. The nose gear had rotated to 90 degrees from center. It is designed to do so in case it loses alignment. That way when you land it won't be pointing in some random direction.

1) If you have a problem and you're near a major airport, leaving the area is not really clever. What if the situation worsens when you're en route? Besides, with the gear down your fuel burn is something like 180% higher, so you're not getting anywhere near New York. Plus you're altitude limited, which increases burn even more. Not to mention speed limited.

2) As GalaxyFlyer says, foam on the ground doesn't seem to do a lot. Also, in this case the gear was down. Putting foam on the ground would have severely impacted brake performance. You're basically contaminating the runway on purpose. Better to have the brakes.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
joejohn
Topic Author
Posts: 2
Joined: Tue Jan 07, 2020 3:46 pm

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 5:27 am

thank you guys, I literally have tears in my eyes because I have found the perfect forum for all my airplane questions. people who actually know what they're talking about.
warning: I will be annoying you with a lot of questions.
 
unimproved
Posts: 247
Joined: Sun Jun 22, 2014 7:14 pm

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 8:22 am

When you don't have nose gear steering you can only steer with differential braking at low speed. Foam greatly reduces that ability.

And gear fires, while unwanted, are pretty easy to extinguish once stopped.
 
TheSonntag
Posts: 4510
Joined: Wed Jun 15, 2005 7:23 pm

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 9:10 am

What happenes if you continue to your destination with a gear issue can be read here:

https://en.wikipedia.org/wiki/Hapag-Lloyd_Flight_3378
 
Woodreau
Posts: 2031
Joined: Mon Sep 24, 2001 6:44 am

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 1:05 pm

joejohn wrote:
warning: I will be annoying you with a lot of questions.


You aren’t the first, and you won’t be the last.

There is no stupid question other than the one that isn’t asked.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
GalaxyFlyer
Posts: 7004
Joined: Fri Jan 01, 2016 4:44 am

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 2:23 pm

TheSonntag wrote:
What happenes if you continue to your destination with a gear issue can be read here:

https://en.wikipedia.org/wiki/Hapag-Lloyd_Flight_3378


True but not a necessary outcome. That accident pilot did not recognize or ignored the FMS cannot do predictions of fuel burns under various drag indices. If you have the drag data and comply with AFM procedures, gear down ferries aren’t an issue.
 
User avatar
Starlionblue
Posts: 20483
Joined: Fri Feb 27, 2004 9:54 pm

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 3:27 pm

GalaxyFlyer wrote:
TheSonntag wrote:
What happenes if you continue to your destination with a gear issue can be read here:

https://en.wikipedia.org/wiki/Hapag-Lloyd_Flight_3378


True but not a necessary outcome. That accident pilot did not recognize or ignored the FMS cannot do predictions of fuel burns under various drag indices. If you have the drag data and comply with AFM procedures, gear down ferries aren’t an issue.


Absolutely.

I think the lesson is that the FMS is an excellent tool, but you can't trust it blindly. Always do at least a gross error check, even if only in your head, to see ft it all makes sense. In a non-normal condition such as this, I'd definitely get pen and paper out along with the QRH tables to check the figures.

It might also be advisable to contact ops and engineering via ACARS or satcom so they can run numbers for you, and just generally support you with diversion options, available runways, RFF capability and so forth.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Lukas757
Posts: 61
Joined: Sun May 08, 2016 11:59 pm

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 3:47 pm

Starlionblue wrote:
It might also be advisable to contact ops and engineering via ACARS or satcom so they can run numbers for you, and just generally support you with diversion options, available runways, RFF capability and so forth.


They actually tried this via HF in that case, but were not able since the equipment at the company didn’t work. That’s no excuse of course.

I‘m actually more amazed that they came so far. If the drag penalty is +180%, that means they used almost 3 times as much fuel.
 
GalaxyFlyer
Posts: 7004
Joined: Fri Jan 01, 2016 4:44 am

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 6:53 pm

Funny story, sorta. In the Gulf with a C-5 gear problem, what a surprise. Flight planner says it’s impossible to get to ETAF without a stop. Crew argues, but caves, sort of. They fill it up til fueling stops, depart, using the Alternate Gear Retraction to Non-Standard Configuration, retract four paws leaving the problem gear hanging in the wind. Almost 12 hours later, land at Frankfurt with about four hours of fuel remaining. Gear speed turns out to be close the max range cruise for level flown due to gear Mach limits. Just get an idea of flight time remaking, fuel on board divided by fuel flow will (and would have in the Hapaf case) give you a good guess if you can make it.
 
mxaxai
Posts: 2324
Joined: Sat Jun 18, 2016 7:29 am

Re: Why not put some fire extinguisher foam on the ground?

Tue Oct 27, 2020 8:31 pm

joejohn wrote:
2) why not put some foam on the ground, or water, before the airplane lands so the landing gear doesn't catch on fire?

The only thing that can easily exit the aircraft and burn are fuel and hydraulic fluid. Metal can spark but does not burn. Tyres can burn but it takes a lot of effort.

Extinguishing (or preventing) a fuel fire is done best by covering it with foam. So in a gear-up landing the fire brigade will meet the stopped aircraft and spray it so that any potentially leaked fluids are covered in foam. In the case of a hot or damaged gear but otherwise intact aircraft there's no real risk of a fuel leak so usually they'll only spray the gear to cool it (to prevent the tyres from catching fire) and cover potential leaked hydraulic fluid.

For some gear-up landings they cover the runway anyway, for example LO 16: http://avherald.com/h?article=4456bd6b/0022&opt=0
And here's an example without a foamed runway, LH 288. Lots of sparking but no fire. http://avherald.com/h?article=41fbf5b9&opt=0
 
User avatar
Starlionblue
Posts: 20483
Joined: Fri Feb 27, 2004 9:54 pm

Re: Why not put some fire extinguisher foam on the ground?

Wed Oct 28, 2020 12:58 am

Lukas757 wrote:
Starlionblue wrote:
It might also be advisable to contact ops and engineering via ACARS or satcom so they can run numbers for you, and just generally support you with diversion options, available runways, RFF capability and so forth.


They actually tried this via HF in that case, but were not able since the equipment at the company didn’t work. That’s no excuse of course.

I‘m actually more amazed that they came so far. If the drag penalty is +180%, that means they used almost 3 times as much fuel.


Just to clarify, +180% is the drag penalty listed in the A330 QRH. It would vary by type but would probably be in that ballpark.

HF is dodgy at the best of times. The good thing nowadays is that ACARS and Satcom are so common. Of course, not being able to contact the company for guidance is yet another reason to be conservative.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
e38
Posts: 790
Joined: Sun May 04, 2008 10:09 pm

Re: Why not put some fire extinguisher foam on the ground?

Wed Oct 28, 2020 2:37 am

joejohn (Topic author), with reference to your second question:

"2) why not put some foam on the ground, or water, before the airplane lands so the landing gear doesn't catch on fire?"

The following information is from wikipedia. I don't usually put a lot of credibility into information from wikipedia, but in this case, it pretty much supports what other members have posted above:

(quote) "A foam path is the now-discouraged aviation safety practice of spreading a layer of fire suppression foam on an airport runway prior to an emergency landing. Originally, it was thought this would prevent fires, but the practice is no longer recommended.
The U.S. FAA recommended foam paths for emergency landings beginning in 1966, but withdrew that recommendation in 1987, although it did not bar its use. In 2002, a circular recommended against using pre-foaming except in certain circumstances. In particular, the FAA was concerned that pre-foaming would deplete firefighting foam supplies in the event they were needed to respond to a fire. Also, foam on the runway may decrease the effectiveness of the landing airplane's brakes, possibly leading to it overshooting the runway." (end of quote)

Foaming runways was used by the U.S. Air Force until about 1985; discontinued because it was expensive to store and maintain for very little benefit.

e38
 
User avatar
HAWK21M
Posts: 30114
Joined: Fri Jan 05, 2001 10:05 pm

Re: Why not put some fire extinguisher foam on the ground?

Fri Nov 06, 2020 4:50 pm

Tough to know where the Aircraft would halt over the foam.
Better to spray the base of the flame after the Aircraft has stopped.
I may not win often, but I damn well never lose!!! ;)
 
User avatar
TOGA10
Posts: 272
Joined: Thu Dec 01, 2016 8:49 am

Re: Why not put some fire extinguisher foam on the ground?

Fri Nov 06, 2020 5:09 pm

Starlionblue wrote:
Lukas757 wrote:
Starlionblue wrote:
It might also be advisable to contact ops and engineering via ACARS or satcom so they can run numbers for you, and just generally support you with diversion options, available runways, RFF capability and so forth.


They actually tried this via HF in that case, but were not able since the equipment at the company didn’t work. That’s no excuse of course.

I‘m actually more amazed that they came so far. If the drag penalty is +180%, that means they used almost 3 times as much fuel.


Just to clarify, +180% is the drag penalty listed in the A330 QRH. It would vary by type but would probably be in that ballpark.

180% is also correct for the A320 family. And fully agree, there is no real need to contact anyone on the ground, as the QRH will tell you exactly this.

Also you would expect the crew to make a decision without anyone on the ground pointing them to a diversion, it's a nice help and good to get assistance, but in the end, it's up to the crew to make the call, imho!
I wanna go back upstairs!
 
m1m2
Posts: 246
Joined: Sat Dec 31, 2011 3:39 am

Re: Why not put some fire extinguisher foam on the ground?

Sun Nov 22, 2020 1:54 am

"The only thing that can easily exit the aircraft and burn are fuel and hydraulic fluid."

Fuel easily burns but hydraulic fluid (LD4 or more commonly known as Skydrol) does not support a flame. If it is sprayed into a very hot fire (such as a torch), it will burn, but when you take away the fire (turn off the torch), it goes out, in other words, you cannot burn it without a very hot fire to get it started. That's why this awful fluid is used on airplanes...any engineer or mechanic here can attest to what Skydrol feels like in your eyes, or know that it melts paint off of anything that it sits on very long.

Oh, one more thing, welcome to airliners.net joejohn
 
VMCA787
Posts: 156
Joined: Fri Sep 04, 2020 9:31 pm

Re: Why not put some fire extinguisher foam on the ground?

Sun Nov 22, 2020 5:16 pm

m1m2 wrote:
"The only thing that can easily exit the aircraft and burn are fuel and hydraulic fluid."

Fuel easily burns but hydraulic fluid (LD4 or more commonly known as Skydrol) does not support a flame.


I think you will find Jet fuel is very much the same. In fact, you can put a match in a bucket of JetA-1 and the match will go out. However, if the fuel is sprayed over the flame, you have a very nice flamethrower. Since, in the cracking process, jet fuel and diesel are both produced pretty much the same way, they have very similar ignition properties.
 
User avatar
fr8mech
Posts: 8108
Joined: Mon Sep 26, 2005 9:00 am

Re: Why not put some fire extinguisher foam on the ground?

Sun Nov 22, 2020 5:42 pm

mxaxai wrote:
joejohn wrote:
2) why not put some foam on the ground, or water, before the airplane lands so the landing gear doesn't catch on fire?

The only thing that can easily exit the aircraft and burn are fuel and hydraulic fluid. Metal can spark but does not burn. Tyres can burn but it takes a lot of effort.


Certain metals can burn. Some older engines have magnesium gearboxes, and present a very real threat of fire. They’re very difficult to get going, but the friction created, say from an engine being dragged along the runway, is sufficient to get it going. As for foam, you may as well be pissing on a forest fire, as much effect it’ll have extinguishing a magnesium fire.

I do confess, I don’t know what materials are used on more modern engines.

VMCA787 wrote:
I think you will find Jet fuel is very much the same. In fact, you can put a match in a bucket of JetA-1 and the match will go out.


Jet fuel, or diesel, is not very much the same as Skydrol, or LD4. Remove the heat source from misting or vaporized LD4 and it will cease burning. Remove the heat source from fuel, and it will continue to burn just as happily.

https://m.youtube.com/watch?v=oE-Xzib1hj4

I can assure you, the ignition source is long gone from this Jet Fuel/Diesel training fire.
When seconds count, the police are minutes away, or may not come at all.
It’s hard to win an argument with a smart person, but it’s damn near impossible to win an argument with a stupid person. ~B. Murray
Ego Bibere Capulus, Ut Aliis Sit Vivere
 
VMCA787
Posts: 156
Joined: Fri Sep 04, 2020 9:31 pm

Re: Why not put some fire extinguisher foam on the ground?

Sun Nov 22, 2020 7:11 pm

My comments were regarding ignition only. I never wrote about the presence of what happens after the ignition source.
 
mxaxai
Posts: 2324
Joined: Sat Jun 18, 2016 7:29 am

Re: Why not put some fire extinguisher foam on the ground?

Sun Nov 22, 2020 9:52 pm

m1m2 wrote:
"The only thing that can easily exit the aircraft and burn are fuel and hydraulic fluid."

Fuel easily burns but hydraulic fluid (LD4 or more commonly known as Skydrol) does not support a flame. If it is sprayed into a very hot fire (such as a torch), it will burn, but when you take away the fire (turn off the torch), it goes out, in other words, you cannot burn it without a very hot fire to get it started.

True, the only real hazard is if it comes into direct contact with brakes or engine parts, which can be very hot AND store a lot of heat to maintain that temperature for quite a while. The metal sparks a belly landing creates will not be enough to set it off but if a line ruptures and drips onto a hot item like a tailpipe, that can be an issue.

I realized I forgot engine lubricants, which are actually slightly easier to burn but are only found near the engines. For example, this caused the post-crash fire on OZ214.
 
m1m2
Posts: 246
Joined: Sat Dec 31, 2011 3:39 am

Re: Why not put some fire extinguisher foam on the ground?

Sun Nov 22, 2020 10:55 pm

I agree that engine oil is flammable but there isn't a huge amount of that available, same with hydraulic fluid really. And once the pumps stop running, very little fluid will continue to flow out. Now fuel, that's another story, unless the reason for the unintended union with the ground is lack of fuel, there's usually several hundred (to several thousand) liters depending on the airplane. Also remember, aluminum will not create sparks, just the steel parts will do that.

To touch back on the original question, I don't think foam would help much if a wing tank is ruptured and the fuel makes contact with the engines, or arcing from electrical wires being torn apart. Modern airplanes are generating enough electricity to run a small town.
 
User avatar
Starlionblue
Posts: 20483
Joined: Fri Feb 27, 2004 9:54 pm

Re: Why not put some fire extinguisher foam on the ground?

Mon Nov 23, 2020 12:54 am

m1m2 wrote:
I agree that engine oil is flammable but there isn't a huge amount of that available, same with hydraulic fluid really. And once the pumps stop running, very little fluid will continue to flow out. Now fuel, that's another story, unless the reason for the unintended union with the ground is lack of fuel, there's usually several hundred (to several thousand) liters depending on the airplane. Also remember, aluminum will not create sparks, just the steel parts will do that.

To touch back on the original question, I don't think foam would help much if a wing tank is ruptured and the fuel makes contact with the engines, or arcing from electrical wires being torn apart. Modern airplanes are generating enough electricity to run a small town.


The fuel also needs to vaporise. A puddle of jet fuel does not ignite very easily.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
m1m2
Posts: 246
Joined: Sat Dec 31, 2011 3:39 am

Re: Why not put some fire extinguisher foam on the ground?

Mon Nov 23, 2020 1:36 am

Indeed, that's why it's sprayed into the combustion can (within the engine) via fuel nozzles or injectors that produce a very fine mist in a very controlled pattern, I've cleaned and changed many of them. Thank you for pointing it out though, I forgot that many people think Jet fuel is a very flammable liquid "as seen on TV".
 
User avatar
Starlionblue
Posts: 20483
Joined: Fri Feb 27, 2004 9:54 pm

Re: Why not put some fire extinguisher foam on the ground?

Mon Nov 23, 2020 2:22 am

m1m2 wrote:
Indeed, that's why it's sprayed into the combustion can (within the engine) via fuel nozzles or injectors that produce a very fine mist in a very controlled pattern, I've cleaned and changed many of them. Thank you for pointing it out though, I forgot that many people think Jet fuel is a very flammable liquid "as seen on TV".


You mean I can't light a trail of jet fuel on fire like Bruce Willis in Die Hard 2? 8-) :D
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
m1m2
Posts: 246
Joined: Sat Dec 31, 2011 3:39 am

Re: Why not put some fire extinguisher foam on the ground?

Mon Nov 23, 2020 3:36 am

That would be awesome, if it were that volatile you could put afterburner on just about any jet. Would be quite cool to see a 777 with that option.

Who is online

Users browsing this forum: CrewBunk and 34 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos