121 Deicing during light snowfall

smig

Well-Known Member
We all know that taking off with ice or frozen precipitation adhering to the aircraft is a no-no. But when exactly would you say that the snow accumulation has "adhered"? More importantly when does the FAA say that snow has adhered to the aircraft?

In situations where there is a very light flurry, and there are a few snowflakes on the wing that will blow off at 10kts of groundspeed, this is obviously not adhering to the wing. In contrast, if you had been sitting for a couple hours in a snowstorm, there will most definately be snow adhering to the wing.

Where do you draw the line during a light snow fall and get deiced? I guess what I really want to know is where does the FAA draw the line?
 

ZapBrannigan

Old School
You get paid by the hour. That system is designed to encourage you to be conservative. So get sprayed and thanks for playing "Deicing For Dollars!"
 

kellwolf

Piece of Trash
Where do you draw the line during a light snow fall and get deiced? I guess what I really want to know is where does the FAA draw the line?

Depends. Was there an accident or an incident? If so, I'm betting the FAA is gonna wanna know why you didn't de-ice. I always err on the side of caution. If nothing happens, well, I worked 15 minutes for free under my current contract, but I'm 15 minutes closer to that "magic" TPIC number. *grumble* However, if something DOES happen, I at least know I did the right thing by de-icing.

Example: It's -SN in DTW today, and we're de-icing. We're running late, but oh well. The XJ -900 next to us in the de-ice pad tells the ice man "Looks like it's slacked off, we'll just take type I." Well, I look outside my window and can see rather large flakes blowing sideways between him and us. No thanks, I'll stick with the type I and type IV, thanks. Holdover on type 1 isn't all that much, and they were doing IFR separation departures out of there. Long story short, we wound up right behind the -900 on takeoff. He had left the de-ice pad about 3 minutes before us. I ran some numbers and figured that if we had gotten Type I only....we'd be over the holding chart limit and have to go back. Based on that and our holding charts, the -900 was probably over his limit, too. That being said, they may have different charts than we do, so I can't honestly say. I can say that with the way the snow was coming down, there's no way in hell I would have gone with type I only.
 

zmiller4

Well-Known Member
Based on that and our holding charts, the -900 was probably over his limit, too. That being said, they may have different charts than we do, so I can't honestly say. I can say that with the way the snow was coming down, there's no way in hell I would have gone with type I only.
For what it's worth, there are companies whose 700's and 900's are authorized for "Pre-takeoff contamination checks" that can be conducted from the cabin after the HOT has expired but within 5min of takeoff. One of the two pilots goes back to the cabin (with a flashlight if it's dark) and looks at the wings to ensure the fluid hasn't failed. Maybe they did that?
 

Nick

Well-Known Member
Why does it matter what the FAA thinks? Deice for safety. Period.

-mini
Still though, there are those times when something is completely safe and the FAA still has a problem with it (though this snowfall scenario may not be one of them).
 

smig

Well-Known Member
Obviously when there is a safety concern we will deice. And since the "deice to screw the company" comments really don't ad value to this discussion, lets say we are on a fixed salary and the deice fluid is free.

When would you say snow is "adhering" to the aircraft. Would you deice anytime there is one single dry snowflake on the wing?
 

BobDDuck

Island Bus Driver
When would you say snow is "adhering" to the aircraft. Would you deice anytime there is one single dry snowflake on the wing?
My manual says that all critical surfaces must be free of contaminants before taking off. So yes, I would deice in the scenario you just gave.
 

smig

Well-Known Member
My manual says that all critical surfaces must be free of contaminants before taking off. So yes, I would deice in the scenario you just gave.
What do you do about the bugs that get squashed on the airplane in the summer?

Personally I would rather takeoff with that single dry snowflake on the wing. Knowing it would blow off at about 10 kts of speed, I don't consider it a contaminant. I would rather have it blow off and have a clean wing than have the performance penalty all that fluid on the wings will bring.
 

WalterSobchak

Well-Known Member
For what it's worth, there are companies whose 700's and 900's are authorized for "Pre-takeoff contamination checks" that can be conducted from the cabin after the HOT has expired but within 5min of takeoff. One of the two pilots goes back to the cabin (with a flashlight if it's dark) and looks at the wings to ensure the fluid hasn't failed. Maybe they did that?
That is infact what we are approved to do at XJ.

Adhering is a key word. it was +3C with a few flurries a week ago and there where a few red tail regionals getting deiced in the 22L pad at DTW while mainline and most every one was going to the runway due to the fact flurries have a hard time adhering if they melt on contact. To each his own and do what you have to to line your pockets as well as being safe.
 
What do you do about the bugs that get squashed on the airplane in the summer?

Personally I would rather takeoff with that single dry snowflake on the wing. Knowing it would blow off at about 10 kts of speed, I don't consider it a contaminant. I would rather have it blow off and have a clean wing than have the performance penalty all that fluid on the wings will bring.
What exactly do you fly where you have to apply a performance penalty for deice/anti-ice fluid? I am honestly curious.
 

B767Driver

New Member
There is no performance penalty for de/anti icing fluid. It shears off before reaching flying speed.

As far as adhering to the airplane...that is a judgment call that will be probably have to be challenged in court if you have an accident.

If it's a a dry snow that hits the fuselage and bounces off...I'm not going to deice.

If there are snowflakes sitting on the surface of the airplane...I'm going to determine that it's adhering.
 

kellwolf

Piece of Trash
For what it's worth, there are companies whose 700's and 900's are authorized for "Pre-takeoff contamination checks" that can be conducted from the cabin after the HOT has expired but within 5min of takeoff. One of the two pilots goes back to the cabin (with a flashlight if it's dark) and looks at the wings to ensure the fluid hasn't failed. Maybe they did that?
Yeah, we've got that, too. But one of the pilots would have had to have done that while a) the airplane was moving or b) while holding short #1 for the runway. I just personally thought it was an unnecessary risk.
 

zmiller4

Well-Known Member
Vr and V2 increase to compensate for fluid.
Sure about that? We increase V1 and Vr to compensate for reduced performance with anti-ice (wings and cowls) on, but we sure don't correct for anything if we just got de-frosted with type I.

Yeah, we've got that, too. But one of the pilots would have had to have done that while a) the airplane was moving or b) while holding short #1 for the runway. I just personally thought it was an unnecessary risk.
Gotcha. I'm uber-paraniod about deicing too. I had rampers in TUS yell at me for asking for a defrosting with "only a film" on the wings.
 
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