Moderate Freezing Rain Globals

[Chally604]

Hi all,

I was wondering if anybody could give me a hint to some official or deeper information in regards to BD700 in FZRA.

Did the Global drivers find any official statement wether you can operate in FZRA or not?
Not -FZRA but moderate.

Holdover Time Tables show only -FZRA values.
Moderate and heavy is not evaluated. Fair enough.

I looked at all the OMs that I collected over time. In most of them nothing was mentioned, in one it was forbidden to operate. But this was only stated for the take off. Thats OK for me. But what about the approach and LDG?

OMs usually direct you to the AFM limitations. But I searched through literally any book that BBD offers and couldnt find anything. Only that the BD700 is approved for known icing conditions, and that you are not supposed to hold there. Sure...

Anyone with some deeper knowledge?
Some experience?

Cheers
Chally

[safelife]

Freezing rain implies severe icing.
Approved for flight into known icing does not include severe icing conditions.

[733driver]

I am not aware of any aircraft "certified" to operate in freezing drizzle and rain (supercooled large droplets). This is, to the best of my knowledge, outside of the engineering standards used during icing certification.

Related reading: Icing Certification - SKYbrary Aviation Safety (http://www.skybrary.aero/index.php/Icing_Certification)

[dirk85]

In our airline we are not allowed to take off in:

Heavy snow (+SN)
Heavy snow pellets (+GS) 
Heavy snow grains (+SG) 
Heavy ice pellets (+PL)
Moderate/heavy freezing rain (FZRA, +FZRA) 
Moderate/heavy hail (GR, +GR)

This is a company limitation, not of the a/c.

And common sense, I would add.

[noneya]

604,

Maybe check the engine limitations put out by the engine manufacturer, not in the AFM. I know of another aircraft that "Officially" can not operate in Freezing Fog, due to the engine limitation, not the airframe... And the Global has the same engine manufacturer (RR)

J

[Chally604]

Hey all,

Thanks a lot.
Need to work a bit on that one, but thanks for the input!

[Mad (Flt) Scientist]

For TO, if you dont have HOT data then you bave no means of assuring the wing is protected, so you are violating the requirement to keep the wing and other critical surfaces clean. Not an OEM call, its a FAA/whoever ops rule thing.

Once in flight, its not considered freezing rain - its just "icing". But freezing rain will quite probably be observed as SLD, with the associated side window icing as an indication. I think if you look for SLD in the icing parts of the manuals you'll find it mentioned, and you're supposed to avoid it and/or get out of it asap.

[Chally604]

Haha, Thanks, That makes sense to me.
As freezing rain is defined as supercooled drops that freez on impact.
But you can have that in pretty much any cloud as long as you are low enough and have OATs around the freezing point.

But freezing rain limits on the ground and the SLD limit in the air does make sense to me. :D