deploying de-icing boots

[puddlejumper]

Anti-Ice in Turboprops

Hey, I'd like to get everyone's opinions on turboprop anti-icing procedures. On a Cheyenne II, engine anti-ice is all on one switch. Turning it on heats the inlet boot, propeller blades and repositions the ice vanes and doors for the engines. I stay conservative and go by the book. Less than +5C and in visible moisture, everything goes on. I've been told that that isn't necessary until ice actually starts accumulating. The ice-door on the intake of a Cheyenne II is always open about an inch, although the deflecting vane is retracted. My concern is twofold. FODing the engines with the ice in the air or potential chunks off the lip I can't see and getting a buildup on the prop blades and banging up the avionics doors. During the day, accumulation is easy to see by looking back at the horizontal stab leading edge or keeping an eye on the windshield wipers.

What do y'all do? I'd like to hear what the SOP is with other TP operators. Thanks.

-PJ

 

[cvsfly]

In this aircraft, normally you will turn on engine anti-ice in any precipitation when the temperature is below +10 degree Celsius.

From the Southwest Airlines FOM:

"Warning: Do not rely on airframe visual icing cues to activate the engine anti-ice. Delaying the use of engine anti-ice until ice build up is visible from the cockpit may result in severe engine damage. Use the temperature and visible moisture criteria specified above."

Specified was +10 degrees Celsius and below, in visible moisture (clouds, fog with visibility less than 1 mile, rain, snow, sleet, ice crystals, mist).

So if ice is never adhering to the wings due to anti-ice, runback really shouldn't be a problem, most of the time.

That is for the B-737 series.

You are talking engine anti-ice here? That won't have much to do wing anti-ice or wing de-icing procedures. Engine anti-ice for the most part is protection against FOD. With minor accumulations and break-off of ice on an engine inlet lip I think there little concern of a flame out. But ice will abrade engine turbine blades. Not good for long life. On the PT-6 the ice vanes/inertial separators/engine-anti-ice are deployed anytime you are in visible moisture and < 5*C. Late model KA use engine inlet lip heat all the time as exhaust is routed through it.

 

[cvsfly]

Re: Anti-Ice in Turboprops

Hey, I'd like to get everyone's opinions on turboprop anti-icing procedures. ......
What do y'all do? I'd like to hear what the SOP is with other TP operators. Thanks.

-PJ

You are right. Everything to do with the powerplant - props, engine inlet, ice-doors - get them on early for everything you stated. With hot props if you wait to get it on you will definately put dents in the nose. What about alcohol props? Wing de-icing by virtue of the term requires some accumulation prior to boots being effective, just some aircraft POHs have adjusted the recommended amount of accumulation prior to inflation. Wing anti-ice (heated with bleed air) I would think it would be a "get it on early" deal, especially considering tail mounted engines, but I have no experience this. Then there is alcohol - weeping wings. I imagine that is classified as de-icing. On the Citations that have it, are the inboard sections of the wing (in front of the engines) equiped? What about the new technology of sonic/mechanical pulse de-icing systems?

 

[80/20]

JetPilot500 asks about 737 wing anti ice procedures and points out that different aircraft types may have various procedures. There is obviously not a single correct answer to our discussion.

Boeing gives this description in their current 737 manuals:
“Wing Anti–Ice Operation – Inflight
The wing anti–ice system may be used as a de–icer or anti–icer in flight only.
The primary method is to use it as a de–icer by allowing ice to accumulate before turning wing anti–ice on. This procedure provides the cleanest airfoil surface, the least possible runback ice formation, and the least thrust and fuel penalty.
The secondary method is to use wing anti–ice prior to ice accumulation. Operate the wing anti–ice system as an anti–icer only during extended operations in moderate or severe icing conditions, such as holding.”

In my experience the biggest 737 ice problem is engine fan icing; it's nasty and dangerous when it happens because it is difficult to remove and will quickly damage the engine. This phenomena is not caused by ice from the wings but other adverse weather conditions such as freezing fog.

 

[Deftone45075]

Hey, I'd like to get everyone's opinions on turboprop anti-icing procedures.

In the J31, any time there is visible moisture at an OAT of <10 C, the engine anti-ice, ignitors, and prop heat go on. The switch for the engine anti ice also turns on the Elevator horn anti ice pad to prevent the elevator from freezing in place.

As we have the older wing/tail boots, we wait until a little ice builds up before cycling them.

 

[El Bucho]

On the Mu2 there is an AD that in icing conditions you must hand-fly the aircraft and the boots placed in the auto mode. I think the auto mode blows the boots like once every 2 or 3 minutes. When to hit the switch will probabloy be debated until the cows come home. I've had the ice bridge the boots both ways whether I let it build up first or turn them on right away. The Mu2 has had extensive tests for icing. Flying behind the tanker and everything and I guess they found that even if the first cycle doesn't get it off, subsequent cycles will remove the ice most of the time.