Icing limitations on commercial aircraft

[bookworm]

What restrictions for flight in icing conditions apply to various turboprop/jet aircraft by virtue of manufacturer's and/or ops manual limitations?

Clearly it varies with type -- I'd just like to get a cross-section, from, say, commuter turboprops up to wide-body jets.

[BmPilot21]

Boeing 737:

Engine ANTI-ice has to be on when the total air temperature (ambient temperature plus the rise due to friction - aka skin temperature) is 10 degrees c or less, and visible moisture is present (cloud, rain, mist with viz less than 1 mile). HOWEVER, it can be turned off in the climb or cruise (not descent) if the ambient temperature is
-40 degrees or less.

The wing protection we generally use as DE-icing. This vents hot air from the engines through the leading edges of the wing.
We use this whenever we see a build up on the wings. If you are entering an area of known icing it is sometimes prudent to put the wing anti-ice on shortly before entering it.

It is not recomended to fly around with leading edge slats or flaps deployed for extended periods in icing conditions (eg holding).

[bookworm]

Thanks BmPilot21.

Is the 737 approved for continued flight in severe icing conditions, or are there, for example, time limitations applied for length of exposure? Are there any icing conditions that are considered 'no go' (rather than just 'prefer not to be here')?

[BmPilot21]

No restrictions that I know of as such, but obviously we keep an eye on it and good airmanship might dictate not staying there if the ice build up was excessive.

We have to add 10 kts to the final approach speed for ice formations on the surfaces, plus there is a large performance penalty (up to 4 tonnes off MLW) for 'residual ice'
-any part of flight in icing and land temperature less than 8 degrees).

[ 19 August 2001: Message edited by: BmPilot21 ]

[Bally Heck]

With respect to BMPilot

I think that few if any civil aircraft are certificated for flight into severe icing conditions. Most are certificated for flight into moderate icing. Severe icing conditions can quickly turn an aircraft into a lollipop and lollipops have poor aerodynamics. Turn around and get out!

Jet aircraft handle icing better than turboprops due to their higher speed and consequent kinetic heating. I have had to descend in a turboprop in moderate continuous icing as it just didn't have the balls to overcome the additional drag.

There was a Shorts 360 several years ago that was forced below MSA due to ice accumulation. Several accidents have resulted from it even in modern types.

[BmPilot21]

You're probably right, though I haven't ever seen anything written down about it for the 737. I've edited my above post.

[Bally Heck]

BMPilot

From memory, the definitions of various icing conditions are in the AIP MET section. Don't have one to hand to check though. Also the definition of severe turbulence, a much misused term. Read it and quake!

[Bally Heck]

Found it! Does this make me officially sad?

AIP Table 3.5.6.2

Moderate Icing: The rate of accumulation is such that even short encounters become potentially hazardous and the use of de-icing/anti-icing equipment is necessary.

Severe icing: The rate of accumulation is such that de-icing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.

Slightly off topic but for all the guys and girls who report they are in severe turbulence, the definition is: Turbulence that causes large, abrupt changes in altitude and /or attitude. Aircraft may be momentarily out of control. IAS fluctuates more than 25 kt. (>1.0 g at the aircrafts centre of gravity) Occupants forced violently against seat belts or sholder straps. Unsecured objects are tossed about. Food service and walking impossible.

Yeeehagh :p

[BmPilot21]

Thanks bally heck. You're only sad if you knew exactly where to find it. If you had to search then I'll let you off! ;)

I guess flying in severe icing isn't such a good idea then. I'm surprised there's no mention of limitations relating to this in the Boeing AFM. Can't find any ref. in the tech. manual or AFM.

Severe turb. sounds fun. Get on your stetsons and big american hat!