MEL: avoid icing conditions?

[Typhoon1244]

Overheard a discussion on Delta radio a couple of days ago: a Delta flight had some sort of deferral that prevented them from flying in "icing conditions," and they were explaining to their dispatcher that they couldn't go into their destination because it was reporting 5 deg. C in rain. Obviously, the Delta pilots have the same definition of "icing conditions" that we do at ASA: 10 C or less with visible moisture. The dispatcher was arguing, though, because as far as he was concerned, "icing conditions" means that icing is occurring, i.e. has been reported.

I've done some unofficial asking around, and was surprised to discover that with respect to the MEL, the definition of "icing conditions" is not all that cut-and-dried. It seems to vary from company to company, and even from airplane to airplane. (Yes, I'll pursue it through my own chain of command as well.)

If I were in this Delta pilot's shoes, and if his dispatcher was correct, I'd have been in hot water because I've got a definition right in front of me that says 10 C or less, visible moisture.

Anyone else have any wisdom to share concerning this?

 

[Flechas]

Same here, 10 C or less and visible moisture, as far as being on the ground, cause it implies that you will be below 0 C at and above 5000 AGl.
Had that been my flight, I would not go either.

 

[jetexas]

At Eagle, icing conditions are defined as "10 C or less in visible moisture...rain, fog with vis less than a mile, snow, sleet, ice crystals". I'd go with what the company manual says, or whatever is most conservative.

 

[KeroseneSnorter]

Unless they have changed(Like maybe yesterday!), the FAA defines icing conditions as 10 and below vis moisture.


I would not have gone either based on the info you have provided. Of course a lot depends on the MEL and it's conditional requirements. That is probably what the dispatcher and pilot were arguing about. I have seen some of the MEL's that made the distinction between "known" icing and "forcast icing" or "icing conditions"

 

[Markm1811]

And we say............

10 degrees or less. visible moisture within the range of the field in question. We also have a 10 mins after take off or before landing that is in some MEL's.

Thats the red tail answer. FOM..

MidnightBrit..

 

[TurboS7]

You can beat that by flying at 330 knots wich will keep the ram temp up above 10C. The problem is that at some time you have to slow down so if you destination experiencing icing conditions then you just have to get the MEL fixed in order to go to that destination. Usually in an airline operation they can flow the "bad" airplanes to the warmer weather and the good ones to the icing weather. Most of the time the MEL items can be fixed pretty quickly as usually it is just a valve or whatever.

 

[atrdriver]

I have never had a dispatcher argue with me about flying into icing conditions with a MEL'd item. Have had a lot of other argurments, but not about that.

 

[avbug]

Icing ideally is five degrees to the plus through fifteen degrees to the minus.

Flight into known icing conditions means any conditions that are known to cause ice, or be conducive to icing...not just areas of forecast or reported ice.

 

[Ty Webb]

It would depend on whether they were talking about a MEL that applied to engine anti-icing, or wing de-icing.

It sounds like the Dispatcher was talking about airframe ice, versus engine anti-icing criteria.

If I had some sort of airframe de-ice MEL, I would be inclined to observe PIREPS, and be checking "representative surfaces" but if the MEL applied to engine anti-icing, then you would have less leeway, since your AOM and/or FOM probably defines when you must have the engine anti-ice on.

In our case, that would mean TAT less than +10C and in visible moisture, except in cruise and climb, when the SAT is less than -40C, whereas for airframe de-ice, it would be based on "representative surfaces" or the actual wings, if you can see them (you can in the 737, but not in the 717, at least not from the cockpit).

 

[atrdriver]

It would depend on whether they were talking about a MEL that applied to engine anti-icing, or wing de-icing.

When our MEL says ICE, it means ANY kind of ice. And our criteria for inflight icing conditions are 7 degrees TAT or below in any type of moisture. If our MEL says avoid icing conditions, that means no clouds with TAT below 7. Period.

 

[Ty Webb]

When our MEL says ICE, it means ANY kind of ice. And our criteria for inflight icing conditions are 7 degrees TAT or below in any type of moisture. If our MEL says avoid icing conditions, that means no clouds with TAT below 7. Period.

If the Delta aircraft was, say, a MD80 series aircraft, there are a number of reasons that they might not have had the ability to deice an airfoil, but had engine anti-ice available. The MEL for each might say "avoid icing conditions" but "icing conditions" for airfoils and for engines are not the same.

Let's put it in terms of your ATR. Would you still be able to takeoff from ATL if the weather was reported as clear skies, tower viz 3/4 mile and the temp was 6 degrees C.? I'm betting the answer is yes . . . . although engine deice would be required to be on, the boots would not have to be operational.

 

[atldc9]

Man, I knew that Boeing-o-sauras was different, but I didn't know it was that different. On the 717, there is no difference between structural and induction icing. We use the same criteria for both, 8 C or less and visible moisture, or OAT 8 C or less and the temp/dewpoint spread within 3 C.

Either way, for US on the 717, whether the MEL refers to structural or induction icing is irrelevant. We use one definition for icing, and if it says no go, we no go. I don't think the Feds would buy the reported vs. forecast argument when deciding whether to apply MEL restrictions with regards to the anti-ice system.

Also, on the 717, the stuff about 'representative surfaces' was added to allow use of anit-ice when the TAT was greater then 10 C, and you could acually see ice on the nut or wiper.

 

[atrdriver]

TY,

Maybe you should read the original post. The issue was a dispatcher arguing that the MEL refering to icing conditions meant actual ice accumulation, NOT icing conditions, which is what most of us have been talking about. Icing conditions exist whether you are in a Piper Cub or a 747, and whether I have props and boots on my wings is irrevelant in this discussion.

 

[Ty Webb]

Man, I knew that Boeing-o-sauras was different, but I didn't know it was that different.

As I pointed out in my previous message, there are certainly instances where the manual says you must use engine anti-ice, yet wing anti-ice may not be necessary.

FWIW, our AOM says to use the wing heat as a de-icer, not an anti-icer. We can see our wings in the 737 from the cockpit.


Happy Landings.

 

[Ty Webb]

TY,

Maybe you should read the original post. The issue was a dispatcher arguing that the MEL refering to icing conditions meant actual ice accumulation, NOT icing conditions, which is what most of us have been talking about. Icing conditions exist whether you are in a Piper Cub or a 747, and whether I have props and boots on my wings is irrevelant in this discussion.

Maybe you should get down off of your soapbox before you fall and hurt yourself.

Icing conditions for airframe ice are different than engine icing conditions . . . sounds to me like your only experience is in your french-made ice magnet, which would explain your ignorance on the subject.

 

[atrdriver]

Yeah, my experience is on the french made ice magnet, and I like it. Regardless, all the MEL's at ASA, for both my ice magnet and the pretty little jet refer to icing conditions, and for ASA that means conditions where ice is likely to form, not places where icing is known to exist. Relax.

 

[dispatchguy]

Every MEL I have ever worked on, to include the French Made Ice Magnet, has always said "known or forecast icing conditions".

If the conditions are conducive to icing, 10C or below and visible moisture vis below a mile, etc, thats forecast enough for me.

 

[bafanguy]

The MEL is a "dispatch" document that applies "...until the throttles are advanced for the purpose of taking off ( the takeoff event )". Once airborne, the POM ruled, but the MEL was always consulted as another source of info/ideas/planning. I can tell you how it was done at Delta from 1973 until I left in '03.

To depart with an MEL item involving anti-ice equipment ( window heat inop, bad TAI valve, etc. ) required a " no ice clearance" from the dispatcher per MEL. This was not a decision one, as captain, could make even if he wanted to. It involved meterologists and the dispatcher and was a legal parameter. Of course, one could always just refuse to fly inspite of the no-ice clearance because he felt it would be unsafe to fly...that's always the captain's call.

If the equipment in question went inop enroute, there were POM procedures in insure adequate anti-icing to complete the flight. Again, if the captain didn't want to procede to destination due to the nature of the problem ( maybe ALL wing, or ALL tail ice protection was inop as an example ), it was then HIS call and would not be questioned by DL Flt Ops management...I can assure you, unless DL has really changed in the last year or so.

Did this address your original question ? Without a lot more details, this is the best I can offer.

The legalities are a different matter from the parameters of temp and viz moisture which dictate WHEN one turns on engine TAI, for example.

 

[Typhoon1244]

If the equipment in question went inop enroute...

Ah, there's the rub. I came into the conversation too late to know if whatever-it-was was deferred prior to departure or broke enroute. Actually, my biggest surprise was the dispatcher's complete ignorance of the 10C/visible moisture thing. The pilot gave them the chapter and verse from his manual, but I don't recall what exactly he said.

Oh, and for Ty and atrdriver...easy, boys. No need to make this personal!

 

[bafanguy]

T1244,


I agree. It's hard to understand w/o all the particulars. But, I'm very confident of the DL MEL policy for such things, having been involved in countless deferrals of ice protection equipment over the years. In fact, there were times when dispatch couldn't give a "no ice clearance" due to the chance of icing enroute even though the departure and arrival airports were no ice.

I still think the MEL definition of icing conditions is more involved/scientific than POM parameters for when a crew would turn on the engine TAI. We didn't use airfoil TAI until we saw a buildup on the windshield wiper arm bolt. And the POM supported that.

This stuff may vary from acft type to acft type or company to company.