Why are the CJ2+ anti-ice and de-ice systems separately controlled? Wouldn't it be easier for both systems to be controlled with one button/switch (minimize chance of error from occurring)? Are there any aircraft that have the two systems controlled by one button/switch that would be activated as soon as ice is detected?


Because they do two different things.

To quote FlightSafety's CJ2 Pilot Training Manual:

Anti-ice protection systems are incorporated into wing, engine components, windshield, pitot-static, and angle-of-attack systems, and pylon ram-air scoops. These systems should be activated prior to entering icing conditions.

The tail deice system consists of pneumatic boots on the horizontal stabilizers.

Basically, anti-ice is used to prevent ice from forming in the first place on the protected surfaces of the aircraft. This is done where it would either be "bad" to have it form in the first place (pitot-static, angle-of-attack, etc.), or where it would be "bad" to have the ice come off after it has formed (and then go through an engine, etc.).

Deice is used to remove ice after it has formed. In this case it is used on the tail which a) isn't critical if it has a little ice, and b) the ice can be broken off after it has formed and it will just fly off the back of the airplane without damaging anything.

Since they serve two different purposes (and protect different parts of the aircraft), there are two different controls/switches.


think of it from an MEL (Minimum Equipment List, manufacturer/governing body approved manual for working equipment & non-working equipment installed on aircraft) stand point if you have 1 switch controlling both systems and the fault lies within the switch, and you don't have a spare (or mx personnel) at the outstation with known-icing conditions probably means you aren't taking off. Yet if you separate systems you might be able to get airborne and play dodge cloud then, remaining clear of known icing.

As for specifics to that aircraft I am not privy as I don't fly it. Other aircraft that are controlled by logic and automated are pretty self explanatory if you understand the nature of its function.

  • $\begingroup$ The reason I brought up the question is because if the plane enters icing conditions and say the anti-ice system for the wings is engaged but the deice system for the tail is forgotten about it could cause the plane to become difficult to control and/or an increase in stall speed. I would think having both systems controlled by one button/switch would minimize a possible human error from occuring. $\endgroup$ Nov 9 '14 at 3:15
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    $\begingroup$ I see what you are asking... On the EMB145 it has separate buttons for Wing/Stab and each Engine has lip anti-ice on their respective bleeds. They are all automatic so there is nothing to do unless an EICAS msg is presented. On the EMB145 the overhead panel is designed in such a way that if the panel is not dark then something is open or wrong. If there something wrong in this case then we run the appropriate QRH checklist according to the msg. Normally all buttons are selected and it will function based on detectors then. $\endgroup$
    – mvermef
    Nov 9 '14 at 7:19
  • $\begingroup$ @mvermef "hey are all automatic so there is nothing to do unless an EICAS msg is presented" except on the ground with visible moisture and SAT <= 10C, in which case you'll manually turn on the engine lip a/ice until your after takeoff flow. (EMB-145) $\endgroup$
    – casey
    Nov 10 '14 at 21:40
  • $\begingroup$ @casey yep absolutely correct... $\endgroup$
    – mvermef
    Nov 10 '14 at 22:36
  • $\begingroup$ @mvermef What you say makes sense. Thank you for giving me the info about the EMB-145. Smaller planes with anti-ice and de-ice systems are advised to exit icing conditions as soon as possible.The thing about my question is that (according to research) sometimes pilots don't detect the icing conditions right away or they don't realize the severity of the conditions. It doesn't take long for ice to accumulate and effect the aerodynamic stability of a plane. I was wondering if the CJ2+ design was influenced by the belief in "ice bridging". $\endgroup$ Nov 22 '14 at 21:30

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