Part121: Can you fly through a severe icing sigmet?

[smig]

I saw this question posted on another forum, yet it was not answered. I thought it was a good question so I bring it here to debate. Like the title says: Can you fly through an area with a sigmet for severe icing?

 

[SpiraMirabilis]

I saw this question posted on another forum, yet it was not answered. I thought it was a good question so I bring it here to debate. Like the title says: Can you fly through an area with a sigmet for severe icing?

Maybe, this is a question where you need to know the difference between the phrase "known icing conditions" and "known icing."

 

[dashdriver]

Well, in a way, sure you can fly thru a sigmet for severe icing. Lets say the northern half of Arizona is under a sigmet for severe icing between 8000 feet to FL180. And you're cruising comfortobly at FL250, in the clear. You are in no way operating your aircraft in the icing conditions. This is probably not the answer you're looking for, I just thought I would give you something in the form of an answer.

 

[higney85]

Common sense must prevail. I have had severe icing (unforecast or previously reported) and don't want to deal with it again- I was in a jet. If you know its there you will avoid it. It also depends on if its a sigmet or just a pirep from a C-172.

 

[jake.durham]

I saw this question posted on another forum, yet it was not answered. I thought it was a good question so I bring it here to debate. Like the title says: Can you fly through an area with a sigmet for severe icing?

I think the key word is "severe icing". For the most part 121 aircraft are certified for flight into known icing. A sigmet for severe icing is not something you want to fly into. It was my understanding that a/c were prohibited from flying in severe ice conditions. However, it was also pointed out that if the sigmet was for an altitude that does not apply to you then you should be ok.

 

[seagull]

Common sense must prevail. I have had severe icing (unforecast or previously reported) and don't want to deal with it again- I was in a jet. If you know its there you will avoid it. It also depends on if its a sigmet or just a pirep from a C-172.

What kind of jet?

 

[dashdriver]

For some reason this has stuck into my head from instrument ground school a few years back. That aircraft certified for flight into known icing conditions are certified for light and moderate conditions only. And yes common sense would prevail that if you're about to go into an area that is severe icing, best to go around it or start heading for an alternate. Last December we were going into Durango at night, and another company plane infront of us shot the approach as we were approaching Durango. When they got on the ground and cancelled IFR, Denver center asked them about icing conditions on the approach, because a few pilots before them had reported moderate rime. Well they reported it to be moderate to severe the last 500 feet of the approach. So the Captain and I started to discuss it, both of us decided that since the wx was getting worse and that there was an airmet for icing, but not a sigmet. And we talked to the other crew on ops frequency about what they had encountered. The Captain and I, along with our dispatcher came to an agreement, that it would be in the interest of safety to divert to Grand Junction.

 

[higney85]

What kind of jet?

CRJ-200.

 

[Yank&BankmyRJ145]

AIM Ch.7-1

c. SIGMET (WS)

1. A SIGMET advises of nonconvective weather that is potentially hazardous to all aircraft. SIGMETs are unscheduled products that are valid for 4 hours. However, conditions that are associated with hurricanes are valid for 6 hours. Unscheduled updates and corrections are issued as necessary. In the conterminous U.S., SIGMETs are issued when the following phenomena occur or are expected to occur:

(a) Severe icing not associated with thunderstorms.

(b) Severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms.

(c) Dust storms or sandstorms lowering surface or inflight visibilities to below 3 miles.

(d) Volcanic ash.

2. In Alaska and Hawaii, SIGMETs are also issued for:

(a) Tornadoes.

(b) Lines of thunderstorms.

(c) Embedded thunderstorms.

(d) Hail greater than or equal to 3/4 inch in diameter.

3. SIGMETs are identified by an alphabetic designator from November through Yankee excluding Sierra and Tango. (Sierra, Tango, and Zulu are reserved for AIRMETs.) The first issuance of a SIGMET will be labeled as UWS (Urgent Weather SIGMET). Subsequent issuances are at the forecaster's discretion. Issuance for the same phenomenon will be sequentially numbered, using the original designator until the phenomenon ends. For example, the first issuance in the Chicago (CHI) FA area for phenomenon moving from the Salt Lake City (SLC) FA area will be SIGMET Papa 3, if the previous two issuances, Papa 1 and Papa 2, had been in the SLC FA area. Note that no two different phenomena across the country can have the same alphabetic designator at the same time.

EXAMPLE-
Example of a SIGMET:
BOSR WS 050600
SIGMET ROMEO 2 VALID UNTIL 051000
ME NH VT
FROM CAR TO YSJ TO CON TO MPV TO CAR
MOD TO OCNL SEV TURB BLW 080 EXP DUE TO STG NWLY FLOW. CONDS CONTG BYD
1000Z.




Sigmets are issued for Severe Icing. And part 121 flys into them all the time. So, Yes to your Question.

 

[dashdriver]

Hahah! You beat me to it. I was just getting ready to put up the same info regarding sigmets from the aim. I'm just waaaaaay to slow at typing

 

[SIUav8er]

Well, in a way, sure you can fly thru a sigmet for severe icing. Lets say the northern half of Arizona is under a sigmet for severe icing between 8000 feet to FL180. And you're cruising comfortobly at FL250, in the clear. You are in no way operating your aircraft in the icing conditions. This is probably not the answer you're looking for, I just thought I would give you something in the form of an answer.

umm, that would mean you didnt fly through the sigmet!

 

[seagull]

CRJ-200.

Thanks, makes big difference, no wonder it was such an issue for you.