The DA42 I’ll fly to get my MEP rating is equipped with an anti-ice system. This system sprays anti-ice fluid on the windshield and weeps some on the leading edges of the wings and on the tail, and on the propeller blades. The AFM supplement describing the anti-ice system is so full of warnings and cautions that it looks more like a legal paper… Basically, the system is made of four pumps. The first pair is used for the leading edges and propellers and the second one for the windshield. When the anti-ice system can be operated in three modes:

• Normal : both pumps run simultaneously and are on for 30 seconds and then off for 90 seconds.
• High: one pump run continuously
• Max: both pumps run continuously

The level of anti-ice fluid and functionality of the system must be checked before flight, but there is no rocket-science in that. Two “ice lights” are also part of the system. They are mounted on the outboard side of the engines and allow for visual inspection at night.

What is interesting is what this system makes possible. The AFM clearly mentions that this is not a de-icing system in the usual sense, as it can only remove small accumulations of ice. Its main purpose is to prevent the accretion of ice. The manual clearly states that the system can not prevent the formation of ice under all possible conditions and that if rapid formation and shedding of bars of ice of more than 6 millimeters is observed, the pilot shall immediately select the High or Max mode and leave the icing area.

Another important remark is that the use of autopilot is forbidden when ice is observed aft of the protected surfaces. This is because using the autopilot may mask tactile clues resulting from degradations of handling characteristics. While I understand it, I don’t fully agree. It is true that having to pull more and more on the stick to maintain altitude is a hint that something is going wrong. But with autopilot engaged, the same would occur and speed will bleed off. An IFR pilot with a good instrument scan will notice it and react to this another hint. Two clues are better than one, but depending of cockpit load, autopilot can help a lot. But if the manual says that it’s forbidden…

Icing is anyway a serious obstacle to light aviation travel, be it in a single or twin, with or without anti-ice system. Any encounter with more than light ice requires evasive action. Getting rid of those problems requires pressurization, and possibly a turbine engine. The anti-ice system of the DA42 is certainly a help, but it sounds to me exactly like the second engine. The second engine makes the descent controllable after loosing one, and the de-icing system makes the escape from the icing area more comfortable.

The landing gear system is just a breeze. If you know the Piper one, it’s essentially the same. An electrical pump controls the pressure in an hydraulic circuit, bringing the gear up or down. If the pump fails, pulling a lever releases the pressure and the gear falls out by gravity. It’s as simple as it must be, and I like it so. Another difference between the DA40 and the DA42 is that the 42 has nose-wheel steering, which I always missed on the 40. And use of more power on the external engine during turns also help.

This post was the last in the series about the DA42 systems. My first simulator session is scheduled in two days, and I polish knowledge of the checklists and flows. Never heard of flows ? More about that soon. And if you liked this post, use the links below to view the other ones I publised about the DA42.

DA42 Electrical System – DA42 Fuel System – DA42 Performances – DA42 V-speeds