Is the decision to de ice an aircraft the captains decision or the decision of the airports? Can airports insist you deice before you depart if they think the conditions merit it? Is there a strict rule for when deicing must occur? I am thinking where the temperature drops to a few C but there has been no rain/snow at what temperature does it become compulsory or advisory?

Thanks,

J

afaik There are regulations which make De-icing mandatory below a certain temperature-depending on the dew-point.

I have never heard of Atc telling a crew to go and get De-iced but pilots should not need asking twice.

The ultimate decision on whether to de-ice or not rests with the captain.
However, a ground engineer (or other suitably approved person) has as much authority in that he/she can order de-icing before the crew arrive and can refuse to release an aircraft without it being de-iced, if he/she deems it necessary. I have never met a captain who did not not want to be de-iced if I deemed it necessary. I doubt I ever will. If I did, his plane ain't goin' nowhere.

Well when the temperatures drop to 4 or 3c is that a deicing time or does it have to drop to freezing point to be considered? Are there any "rules" for guidance of when to consider it?

Quoting Julesmusician (Reply 3): Are there any "rules" for guidance of when to consider it?

I'm sure most carriers have a book or procedure as we do. We have a section in our Ops Man. that references cold wx. ops and tables that compare temp, type of precip and type of de-ice fluid to give you an estimated holdover time. Some other mandatory procedures are inspection of the eng. inlets for ice or contamination, and control surface movement prior to taxi. The capt. makes the final decision at the runway that the a/c is still clean and good to go. We have a restriction that a t/o in light frz rain is permissable if type II or IV fluid is used. That's a brief summary of what's 20 pages in the book.

There are a number of "rules" about when to de-ice. The air temperature (as such) is not a deciding factor. De-icing, by it's very name, is only carried out to remove accumulations of snow, ice or frost.
In some circumstances, anti-icing may be carried out ahead of forecast icing conditions.

I flew through CLE twice today (early AM and evening) and both times only CRJ200s were being deiced. Various other Boeings, Buses, and Embraers were not being treated. Are the CRJ models especially vulnerable to icing problems?

This is something We never get to observe out here.
Can De-Icing be carried out with Pax on board.And how effective is Infra-red deicing comparatively.

Quoting CosmicCruiser (Reply 4): The capt. makes the final decision at the runway that the a/c is still clean and good to go

Why at the Runway & not before Start up.

regds
MEL

Quoting HAWK21M (Reply 7):

due to hold-over times of Type 1 deicing fluid, the a/c is almost always deiced when the passengers are on board as to keep from allowing the fluid, though extremely hot, time to freeze. hold-over times depend on the freeze point of the glycol/water mixture you are spraying.

the PIC makes the call at the runway because that is the point at which the a/c has been sitting the longest before TO.

Quoting CRJonBeez (Reply 8): the PIC makes the call at the runway because that is the point at which the a/c has been sitting the longest before TO.

What factors help the Pilot seated Inside the Aircraft decide before T/O that De-Icing is needed.
regds
MEL

Quoting CRJonBeez (Reply 8): the PIC makes the call at the runway because that is the point at which the a/c has been sitting the longest before TO.

That's not true, in the common sense. There are cases when de-icing has to take place after a long taxi, because of accumulation and ultimately, the expiry of the holdover time of the fluid. However, the call to de-ice is usually made at the gate, looking at the surfaces on the aircraft, and depending on meterological conditions.

The de-icing can take place just after pushback, or at airports with such a facility, at the de-icing pads. Both, I find, are quite efficient.

The engineers will usually give you what type of glycol/water mix the de-icing fluid is, along with the holdover times, as it isn't always a straight forward type I, II or IV fluid used, as explained above. If it isn't mixed properly, de-icing fluid may get into crevices near the control surfaces, and as it is a sticky fluid, it could become a maintenance nightmare. Haven't heard of flight controls not functioning properly because of this, but I could be wrong.

Quoting HAWK21M (Reply 9): What factors help the Pilot seated Inside the Aircraft decide before T/O that De-Icing is needed.

The aircraft I fly with are quite long, so we tend to walk to the back just before take-off to make sure there isn't significant accumulation. There are several points inside the cabin where it is marked as the best view you can get of the wings, for you to look out and get a better picture of the wing condition. There are lights on the aircraft which we can turn on specifically to shine on the wings, which definitely helps during the night.

But the best view is always while the aircraft is at the gate. We peer out of airbridges, look at the fuselage during the walkaround, etc.

De-icing is carried out with the pax onboard, but care has to be taken to make sure all outside ventilation is closed. That includes the pack vents, the bleeds, and the outflow valves. Otherwise, the smell can permeate throught the cabin, and it isn't the most pleasant. The other obvious factor is that the engines have to be off while this is happening.

Quoting BuckFifty (Reply 10): The aircraft I fly with are quite long, so we tend to walk to the back just before take-off to make sure there isn't significant accumulation.

How would ATC react to that.Holding on Runway prior to T/O while the Crew walk in the cabin to check the Ice conditions,or are you referring to at the gate.
regds
MEL

If the conditions are bad (i.e. freezing rain or heavy snow), and we are at the holding point, sorry, everyone will have to wait. Safety first, there is no room for empathy in that.

There must be some fail safe system that insures de ice takes place even if you cannot see ice? Say the temperature is down to 3c or 2c and you do your walk around and cannot see any ice, would you not order deicing anyway on the basis that is cold enough for ice to start forming and it might not be seen?

Quoting HAWK21M (Reply 11): How would ATC react to that.Holding on Runway prior to T/O while the Crew walk in the cabin to check the Ice conditions,or are you referring to at the gate.

why would ATC care about that? if the flight crew is not sure about its safe to take-off they can take all the time they want to check the AC on the runway for ice. they can also chose to return to the gate for more de-icing/anti-icing..right?

after de-icing/anti-icing its important to get the AC quickly up in the air...before the effects of the treatment is starting to rub off...

At my company the decision to deice is made at the gate, when we (or really the FO) does the walkaround, we check to see if there is any frost or ice on the wings, control surfaces, engine cowlings and other locations. If we aren't sure, e.g. in the event of clear ice, we are required to use tactile means (take off the gloves and put our knubby hands on the airplane) of determining if there is ice or not. Temperature has no bearing on whether we deice or not. It is the presence of frost, ice, etc.

The actual deice procedure and location where the deicing occurs depends on the actual airport, but most airports we contact ramp for push clearance, and we tell them that we are going to the deice pad, they'll clear us to the deice pad, we call up the deice pad and they assign us a "slot" in the deicing pad, we taxi into the deice pad and shut down the engines. They spray the goop all over the airplane and after it's all done, they tell us what deice fluid they used, time they started, hold time and other particulars, and that their visual inspection of the plane shows the plane is deiced. We start up again, contact ground, taxi out to the runway.

Temperature, precipitation type, and deice fluid used does factor into hold time - hold time can be as short as 5 minutes in really bad conditions. If we get to the runway and the hold time is still valid, we'll look out onto the left wing to see if it's still clear of ice (our airplane is short enough that the captain can look out the left window) and if it's clear, we'll go. If the hold time has expired, then we are required to do a visual check for icing within 5 minutes of takeoff - we'll do the same thing look at the left wing-if it's clear, we'll go, if it's not, we'll contact ground and request to taxi back to the deice pad.

It seems like you're looking for a more "solid" procedure to determine whether to deice or not, but primarily it's a visual detection.

The only thing that is temperature dependant is the use of anti-ice equipment on the aircraft. If the temperature is less than 10c and visible moisure is present, we will turn on the engine cowling anti-ice. Once the temperature drops below 5c, then we turn on both engine and wing anti-ice. However, if we are deicing at the deice pad, we will turn on the engine anti-ice, but we won't turn on the wing anti-ice until we are cleared onto the runway for takeoff because the wing is supposedly protected by the deicing fluid.

Once you apply power for takeoff, the deice fluid loses its protective properties - after it is applied it is a sticky film that adheres to the aircraft to prevent ice formation, airflow over the wing disrupts/blows the film off the wing. So if you have a rejected takeoff and you accumulate ice during the taxi back, you need to deice again.

[Edited 2005-11-18 14:52:19]

Quoting HAWK21M (Reply 7): Why at the Runway & not before Start up.

When a holdover time is calculated you are assumming that the precip is still falling. Therefore, according to our man., FAR 121.629(c)(3) requires a pre-takeoff check. Based on flight crew observations of wx. conditions at the runway the capt. will make an evaluation from inside the cockpit and decide to t/o or return for another de-icing. Accumulation on "representative surfaces" such as windshield wipers, edge of windshield and top of radome indicate worsening conditions and should be considered as indicators of what may be occurring on critical surfaces. We also may use a Pre-Takeoff Contamination Check which is done at the end of the runway by a certified team of maint. or flight crew personnel.

This is the time to be reviewing all these winter ops procedures and now this post has made me pull out the book. Maybe I'll bid SYD!!

Once at CDG the a/c I took out had just arrived an hour or so later and since the snow had stopped didn't need de-icing. All the pax carriers that had been sitting at the gate most of the day needed a trip to the carwash. For some reason CDG ground, learning that we didn't need de-icing, let us sit at the end of 09R for about 30-40 min. while all the pax jets left the carwash and went straight to t/o. Thinking I'm sure of holdover times only and not that the precip had stopped hours earlier!!

Generally, the decision to de-ice is made long before departure. If there is precip and the temp is low enough, it's a "no brainer". The biggest worry is having the "hold over" time expire before you can take off. However, the only good thing is that everyone is in the same position and usually ATC will do a good job at getting everyone out.

In reality there is no "fail safe" system. De-icing isn't only dependent on the temp, you need precip there too.

At the end of the day, it's the Captain's call as to de-ice or not. I have asked to be de-iced only to have MX tell me it isn't needed. That's great, but they're not going on the aircraft, I am.

Quoting PhilSquares (Reply 17): The biggest worry is having the "hold over" time expire before you can take off. However, the only good thing is that everyone is in the same position and usually ATC will do a good job at getting everyone out.

What happens at places like PHL, EWR, ORD, etc. where there is almost always a take off line to some extent, which sometimes can be upwards of an hour +?? Hold over times in a heavy-enough event are well under an hour, right? Do they have a deice truck waiting on the taxiway right before the runway for a final rinse, or how do they work it with the long lines during a snow, or worse, light freezing rain day?

Quoting D5DBY (Reply 14): if the flight crew is not sure about its safe to take-off they can take all the time they want to check the AC on the runway for ice

Quoting Woodreau (Reply 15): At my company the decision to deice is made at the gate

Why not check it prior to entering the Runway.Why "on" the Runway,will lead to delaying Arrivals & other departures.Hence ATC would be concerned.
regds
MEL

Mel, think you are wondering why they would need to check for ice on the runway - they would only do so if the time they have taken since being de iced as gone past the time they are allowed to be on the ground without a re-check - Any check on the runway sounds like it will be purely a visual check - although perhaps the pilots could answer would they ask ground crew/staff to do a look at the aircraft while it is holding on the taxiway?

[

Quoting HAWK21M (Reply 19): Why not check it prior to entering the Runway.Why "on" the Runway,will lead to delaying Arrivals & other departures.Hence ATC would be concerned.

I don't know if you're referring to my post regarding the pre-takeoff check or not but for us it's not ON the runway but prior to entering the runway and should not create any ATC delay. Nobody said you must come to a complete stop, hold the checklist and do the pre-t/o check. You just make the observation and decide if you can go or not.

What height are the deicing switches turned off when ascending out of a snowy airport? I assume there is a height where the air doesn't hold enough moisture for icing?

Quoting Julesmusician (Reply 22): I assume there is a height where the air doesn't hold enough moisture for icing?

Not necessarily, Most jets will use antice as long as in "icing conditions' which is for us in the -11 TAT +6 or less and invisible moisture and/or the "ice detected" alert is illuminated. In the 727 we used to add the mach and TAT and if the total was greater than 90 then the OAT was lower than -40 so no antiice was used. The DC-10 and MD-11 do not follow this procedure.

It is interesting to know whether most jets now have an "ice detected" alert or whether it is still down to seeing it or working it out?

i have read that ACs with leading edge devices can take alot more ice than ACs without leading edge devices, dont know if thats true?

also, if the pilot wants even more safety in frosty conditions, he could be conservative with the take-off speed...calling "Vr" at a higher IAS than normal...perhaps any pilot here calls "Vr" a bit later than normal in frosty conditions?

Quoting D5DBY (Reply 25): i have read that ACs with leading edge devices can take alot more ice than ACs without leading edge devices, dont know if thats true?

That's the theory behind the Challenger accident at Montrose that killed the guy from NBC (I forget his name) on that MTJ-SBN flight last November, also part of the theory of that Challenger at TEB in the spring on a frosty morning.

Quoting D5DBY (Reply 14): if the flight crew is not sure about its safe to take-off they can take all the time they want to check the AC on the runway for ice

Quoting CosmicCruiser (Reply 21): but for us it's not ON the runway but prior to entering the runway and should not create any ATC delay.

The Statement by D5DBY of Pilot checking for Icing "ON" the Runway,brought about my Doubt & involved ATC.

According to me.The check should be prior to Entering an Active Runway.
regds
MEL

Quoting BuckFifty (Reply 10): Otherwise, the smell can permeate throught the cabin, and it isn't the most pleasant. The other obvious factor is that the engines have to be off while this is happening.

C'mon man. Atleast its not USED DG-19 (toilet blue-juice) that we're spraying on the plane. The glycol tastes like cotton candy when you get used to it.   

Quoting HAWK21M (Reply 27): The Statement by D5DBY of Pilot checking for Icing "ON" the Runway,brought about my Doubt & involved ATC. According to me.The check should be prior to Entering an Active Runway. regds MEL

yeah...probably your right...the ice check is performed prior to entering the runway, i would guess.

i as my company's WOC (winter ops coordinator) am allowed to order deicing for all aircraft if i deem it necessary. however, by the time i say its needed the crew will have already called us. for my station, if there is any frost on the airplane and it spent the night then they get sprayed without question. we actually sprayed this morning, all 7 of our RON airplanes. there wasn't much frost, but there was condensation on the wings where the fuel bladders met the skin of the wings.

i don't know what is it about CRJ-200s but they do seem more susceptible to accumulating frost, especially overnight. they're also a pain in the ass to train new people to spray because they keep getting fluid into the APU intake. all in all, it's a badly designed airplane.

Quoting Tornado82 (Reply 18): What happens at places like PHL, EWR, ORD,

Generally, at airports such as the ones you mention, de-icing is carried out much closer to the runway. The delay involved is usually with the deicing so departure delays don't impact it that much.

Quoting Julesmusician (Reply 22): What height are the deicing switches turned off when ascending out of a snowy airport?

On the 744, there are two different things we're talking about. First there's engine anti-ice. That's turned on when there is visible moisture (vis less than 1 mile) and the TAT is less than +10 and above -40C.

Wing heat has the same restrictions, but on the Boeings wing heat is inop when the flaps are out of the up position. I think I can count the number of times I've used wing heat on one hand and still have fingers left over.

Quoting PhilSquares (Reply 31): but on the Boeings wing heat is inop when the flaps are out of the up position

Shouldn't it be while Aircraft on Grd & Engines shut down.No WTAI.
regds
MEL

Quoting HAWK21M (Reply 32): Shouldn't it be while Aircraft on Grd & Engines shut down.No WTAI. regds

On all Boeings there is no WAI on the ground and in the air while the flaps are out of the up position.

Quoting PhilSquares (Reply 33): On all Boeings there is no WAI on the ground and in the air while the flaps are out of the up position.

Apart from Grd Test mode.
What about the B737s.Whats the Sequence logic for WTAI.

The WAI switch logic is on the ground, bleed air for WAI will cut-off if either thrust lever is above the take-off warning setting, but will be restored after the thrust is reduced. This allows you to perform engine run-ups etc without having to check that the WAI is still on afterwards. The switch is solenoid held and will trip off at lift-off, this is for performance considerations as the bleed air penalty is considerable.

Note that on B737 early systems, ie those with a GND TEST position, with the WAI switch ON on the ground, the WAI is inhibited until lift-off ie "armed", This is opposite to the present system.
regds
MEL

Quoting PhilSquares (Reply 33):

Are you sure that holds true for all Boeings? I've been out if the 727 for about 10 yrs. but I don't recall that limitation. Yes to no WAI on the ground except for the grd. test.

Quoting BuckFifty (Reply 10): The engineers will usually give you what type of glycol/water mix the de-icing fluid is, along with the holdover times, as it isn't always a straight forward type I, II or IV fluid used, as explained above. If it isn't mixed properly, de-icing fluid may get into crevices near the control surfaces, and as it is a sticky fluid, it could become a maintenance nightmare. Haven't heard of flight controls not functioning properly because of this, but I could be wrong.

Has been reported some troubles with the flight controls on the BAe 146 due to de-icing. specially type 2 and 4

Quoting BuckFifty (Reply 10): De-icing is carried out with the pax onboard, but care has to be taken to make sure all outside ventilation is closed. That includes the pack vents, the bleeds, and the outflow valves. Otherwise, the smell can permeate throught the cabin, and it isn't the most pleasant. The other obvious factor is that the engines have to be off while this is happening

in almost all the airports where I went we do the de-icing with the engine running

Quoting Julesmusician (Reply 13): There must be some fail safe system that insures de ice takes place even if you cannot see ice? Say the temperature is down to 3c or 2c and you do your walk around and cannot see any ice, would you not order deicing anyway on the basis that is cold enough for ice to start forming and it might not be seen?

Quoting PhilSquares (Reply 17): In reality there is no "fail safe" system. De-icing isn't only dependent on the temp, you need precip there too.

Well, there are procedures, and they aren't failsafe but they normally work if the crew and mechs are well trained.

Quoting Tornado82 (Reply 18): What happens at places like PHL, EWR, ORD, etc. where there is almost always a take off line to some extent, which sometimes can be upwards of an hour +?? Hold over times in a heavy-enough event are well under an hour, right? Do they have a deice truck waiting on the taxiway right before the runway for a final rinse, or how do they work it with the long lines during a snow, or worse, light freezing rain day?

Or deice pads close to the runway. I've been in planes on the taxiway which happen to wait longer than anticipated. Nothing to it but go back to the pad...

Quoting Julesmusician (Reply 20): Mel, think you are wondering why they would need to check for ice on the runway - they would only do so if the time they have taken since being de iced as gone past the time they are allowed to be on the ground without a re-check - Any check on the runway sounds like it will be purely a visual check - although perhaps the pilots could answer would they ask ground crew/staff to do a look at the aircraft while it is holding on the taxiway?

Not sure about this but the stuff BuckFifty is referring to is how the deice fluids have been applied, not the actual ice. But I might be wrong.

Quoting Julesmusician (Reply 24): It is interesting to know whether most jets now have an "ice detected" alert or whether it is still down to seeing it or working it out?

You can have all the sensors you want, but a hand on the wing is still your best bet. The SAS MD-80 crash at Gottröra proves this out. Procedures at SAS were changed after that to mandate a hand on the wing, since clear ice wasn't detected with any other method and sheets of it flew into the engines.

Quoting CosmicCruiser (Reply 35): Are you sure that holds true for all Boeings? I've been out if the 727 for about 10 yrs. but I don't recall that limitation. Yes to no WAI on the ground except for the grd. test.

CC, I've been off the 727 for longer than that!!! But, I do remember that one of the things about the 727. IIRC when the flaps are out of the up position, ie Flaps 2, the WAI is dumped overboard.

Quoting Ba299 (Reply 36): in almost all the airports where I went we do the de-icing with the engine running

What in case the Inlet is Iced up.Would you risk running the Engine.
regds
MEL

Quoting Tornado82 (Reply 18): Do they have a deice truck waiting on the taxiway right before the runway for a final rinse, or how do they work it with the long lines during a snow, or worse, light freezing rain day?

At the new AMS runway there are special pads right before entering the runway, about 3 of them next to each other. At MUC there two (I think) next to each other near the beginning of each runway.

The AMS remote pad:

View Large View Medium Photo © Rob van Ringelesteijn

View Large View Medium Photo © Rob van Ringelesteijn

Some other pads in AMS:

View Large View Medium Photo © Alastair T. Gardiner - WorldAirImages

View Large View Medium Photo © Alastair T. Gardiner - WorldAirImages

Yet manual inspection is also done  

View Large View Medium

Photo © Andreas Stoeckl

Nice Pics.
How many trucks for DeIcing & what Capacity.What about the People carrying out the DeIcing. Any Protective Equipment.
regds
MEL

View Large View Medium

Photo © Erik Sleutelberg

This pic really gives a close look at the Deicing operation in progress.Thought I'd share it.
regds
MEL