Julesmusician From , joined Dec 1969, posts, RR: Posted (7 years 7 months 4 days ago) and read 4317 times:
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?
Charliecossie From Germany, joined Oct 2001, 467 posts, RR: 10 Reply 2, posted (7 years 7 months 3 days 23 hours ago) and read 4299 times:
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.
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.
Charliecossie From Germany, joined Oct 2001, 467 posts, RR: 10 Reply 5, posted (7 years 7 months 3 days 18 hours ago) and read 4240 times:
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.
MasseyBrown From United States of America, joined Dec 2002, 4750 posts, RR: 7 Reply 6, posted (7 years 7 months 3 days 17 hours ago) and read 4227 times:
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?
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.
BuckFifty From Canada, joined Oct 2001, 1314 posts, RR: 21 Reply 10, posted (7 years 7 months 3 days 16 hours ago) and read 4202 times:
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.
Julesmusician From , joined Dec 1969, posts, RR: Reply 13, posted (7 years 7 months 3 days 12 hours ago) and read 4172 times:
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?
D5DBY From , joined Dec 1969, posts, RR: Reply 14, posted (7 years 7 months 3 days 9 hours ago) and read 4157 times:
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...
Woodreau From United States of America, joined Sep 2001, 895 posts, RR: 7 Reply 15, posted (7 years 7 months 3 days 9 hours ago) and read 4152 times:
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]
Good judgement comes from experience. Experience comes from surviving bad judgement.
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!!
PhilSquares From , joined Dec 1969, posts, RR: Reply 17, posted (7 years 7 months 3 days 9 hours ago) and read 4148 times:
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.
Tornado82 From , joined Dec 1969, posts, RR: Reply 18, posted (7 years 7 months 3 days 8 hours ago) and read 4141 times:
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?
Julesmusician From , joined Dec 1969, posts, RR: Reply 20, posted (7 years 7 months 3 days 5 hours ago) and read 4112 times:
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?
CosmicCruiser From United States of America, joined Feb 2005, 2222 posts, RR: 16 Reply 21, posted (7 years 7 months 3 days 3 hours ago) and read 4090 times:
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.
CosmicCruiser From United States of America, joined Feb 2005, 2222 posts, RR: 16 Reply 23, posted (7 years 7 months 3 days ago) and read 4064 times:
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.