speedracer1407
Posts: 330
Joined: Fri Dec 24, 2004 4:19 pm

Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 11:28 am

I was shocked this tuesday when my flight aboard a CO 733 took off from ORD during a snowstorm with minimal delay. Whatever delay we had was due to the plane's late arrival from wherever it originated and deicing. Once we were covered in orange goo, we proceeded straight to the runway and took off.

I understand that planes can takeoff in all sorts of situations that render other, more mundane tasks like driving dangerous or even impossible. But what are the limits as far as snow accumulation and rate of snowfall (is there even a limit for that?) that determine whether a plane can take off or not.

On tuesday, for example, snow was falling pretty hard, causing very limited visibility, especially during gusts of wind, which whipped up the top layer of snow banks and blanketed taxiways and runways with a fog of snow. the runway itself was somewhat cleared, but plenty of snow had piled up in places throughout the runway's length, which was very evident during our take off run as it felt as though someone had installed huge speedbumps along the runway. An MD-80 ahead of us lined up for takeoff, sat for a few minutes, then simply made for the nearest turnoff.

Anyway are there published limits for this sort of situation? Is it plane specific? To certain types have greater/lesser difficulty with winter weather?

This, by the way, was somehow my first takeoff in snowy conditions despite having lived in chicago for 26 years. Imagine that.
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
corey07850
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RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 11:38 am

Quoting Speedracer1407 (Thread starter):

Anyway are there published limits for this sort of situation? Is it plane specific? To certain types have greater/lesser difficulty with winter weather?

It's more of a company procedure than a set limit by the FAA. Some operators won't take off or land with a runway that has thin LSR, or with mu values under .25 while others may choose to operate in worse conditions. It's a real subjective thing when it comes to braking action reports and operating during snow/ice...

Some things that are regulated are de-icing fluid holdover times, the "no flight into known icing" thing that seems to be causing a stir, braking action reports of nil will 99% of the time result in a runway closure, amount of contamination on wings etc.
 
highflyer9790
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RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 11:49 am

Quoting Speedracer1407 (Thread starter):
But what are the limits as far as snow accumulation and rate of snowfall

A lot of times runway/taxiway closure is determind by braking conditions: good, fair, poor, etc. most of the time, this will result in less than 1/4 inch of snow. Ice is a different matter, all you need is a glaze and the airport is chaos.
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CosmicCruiser
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RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 12:07 pm

To answer your original question...When you've been de-iced/anti-iced you go to a chart that plots temp and type of fluid and type of precip to give youm a conservative "hold over time". This gives you a reasonable idea of time of protection to taxi and t/o. .


Quoting Corey07850 (Reply 1):
Some things that are regulated are de-icing fluid holdover times

Hold over times can be adjusted for changing wx conditions by the capt.

Quoting Corey07850 (Reply 1):
"no flight into known icing" thing that seems to be causing a stir,

What? We can't be dispatched into known severe icing but other than that you're good to go. We can't do FZRA,GR,IP but that's about it.
 
Goldenshield
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RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 12:13 pm

Quoting CosmicCruiser (Reply 3):
What? We can't be dispatched into known severe icing but other than that you're good to go.

I think he's talking about an MEL. I can think of several that could cause that limitation.
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speedracer1407
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Joined: Fri Dec 24, 2004 4:19 pm

RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 12:29 pm

Quoting HighFlyer9790 (Reply 2):
A lot of times runway/taxiway closure is determind by braking conditions: good, fair, poor, etc. most of the time, this will result in less than 1/4 inch of snow. Ice is a different matter, all you need is a glaze and the airport is chaos.

So, is that a consistant 1/4 inch of snow over all or atleast the majority of a runway/taxiway? Because much of the taxiways and a good bit of the runway was covered in patches of 1-4 inch deep snow (an estimation from my window seat based on the depth of tire imprints through the snow as well as great big suspension oscillations as we bounced our way over big piles of packed snow).

Quoting CosmicCruiser (Reply 3):
When you've been de-iced/anti-iced you go to a chart that plots temp and type of fluid and type of precip to give youm a conservative "hold over time". This gives you a reasonable idea of time of protection to taxi and t/o. .

Is icing the only consideration? Actaully, now that you mention it, I was somewhat suprised to see that orange goo become pretty ice-like (like someone spilled an enormous orange-flavored snowcone) as it settled in the nooks and crannies such as the engine nacell's vortilons, where the pylons meet the wing, and indeed, on my window. I was also surprised that towards the end of our taxi, the front half of the wing was pretty clear, but the deicing fluid had settled over the aft half of the wing, and sure did look frozen. I'm sure I can't tell for sure, but, well, it just looked like icey orange goo. Not that this was unsafe, but I thought deicing fluid melted pretty much anything on contact. Guess I need to take more blizzard flights in the future.
Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.
 
doug_or
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RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 1:11 pm

Quoting Speedracer1407 (Reply 5):
Actaully, now that you mention it, I was somewhat suprised to see that orange goo become pretty ice-like (like someone spilled an enormous orange-flavored snowcone) as it settled in the nooks and crannies such as the engine nacell's vortilons, where the pylons meet the wing, and indeed, on my window. I was also surprised that towards the end of our taxi, the front half of the wing was pretty clear, but the deicing fluid had settled over the aft half of the wing, and sure did look frozen. I'm sure I can't tell for sure, but, well, it just looked like icey orange goo. Not that this was unsafe, but I thought deicing fluid melted pretty much anything on contact. Guess I need to take more blizzard flights in the future.

Two kinds of de-iceing fluids commonly used in the US type 1 and 4. Type one is applied hot and melts contaminant on contact. Type 4 is [almost] always applied cold, so it sticks to the plane. As snow falls it will either melt into the type 4 or accumulate a little on top of it depending on temp and rate its falling. As the aircraft accelerates for takeoff the type 4 and any contaminants are swept off the plane.
When in doubt, one B pump off
 
memphis
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RE: Takeoff/landing In Snowstorm--limits?

Fri Feb 16, 2007 9:54 pm

if contaminated, important to apply type 1 BEFORE type 4! Type 4 is only applied if precipitation is falling. De-Icing with type 1 i.e. DE-ICE (orange fluid) is loads o' fun. High Temperature, High Pressure, It has a nozzle temp of somewhere around 180, so when it is coming out, a "de-ice steam" may surround you and act as a deterrent to the cold, doesn't really work if it is really windy. Type 4 or ANTI-ICE, (green fluid) is like a jelly substance that is applied after the de-ice or in a pre-treat (if the plane is sitting in the gate and precipitation is coming soon, anti-ice may be applied to make the de-icing later, easier.) As pointed out, it is the purpose of this anti-ice to deter ice from building, yet the anti-ice is designed to come off the A/C durimg the take-off roll.
nocturnal
 
GQfluffy
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RE: Takeoff/landing In Snowstorm--limits?

Sat Feb 17, 2007 4:38 am

Quoting Memphis (Reply 7):
Type 4 is only applied if precipitation is falling.

Yeah, and for those of us who's aircraft can't be sprayed with Type 4, keeping an a/c clean with just Type 1 is a real bitch.

Quoting Memphis (Reply 7):
De-Icing with type 1 i.e. DE-ICE (orange fluid) is loads o' fun. High Temperature, High Pressure, It has a nozzle temp of somewhere around 180, so when it is coming out, a "de-ice steam" may surround you and act as a deterrent to the cold

Oh yeah, you forgot the sarcastic smiley here. Sure it's nice and warm...and sticky...and smelly...and...that shit gets on you and never comes off. I hate winter-ops...
This isn't where I parked my car...
 
A342
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Joined: Sun Jul 31, 2005 11:05 pm

RE: Takeoff/landing In Snowstorm--limits?

Sat Feb 17, 2007 5:48 am

Concerning snow on the runway, look at this pic:


View Large View Medium
Click here for bigger photo!

Photo © Markus Herzig



There are other nice, snowy photos from the same airport in the database.
Exceptions confirm the rule.
 
OPNLguy
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RE: Takeoff/landing In Snowstorm--limits?

Sat Feb 17, 2007 9:01 am

Quoting Speedracer1407 (Thread starter):
But what are the limits as far as snow accumulation and rate of snowfall (is there even a limit for that?) that determine whether a plane can take off or not.

There are various limits set by the manufacturer, and are too numerous (not to mention proprietary) to mention. Suffice it to say that there are maximum permissible depths for wet snow, dry snow, slush, and water on runways, and there are separate limits for takeoffs and landings. Runway plowing/brooming usually take place before these max "clutter" limits are reached, since the resultant takeoff (or landing) weight penalties would probably end up leaving people behind. Keep in mind that the above all concern what's on the runway surface. What's on the aircraft itself is another story, and others have already chimed in about the various types of de-icing fluid.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.

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