ADI switch

[Bluegrass1]

I downloaded the CV340 panel and it has an ADI switch. What is its function?

Thanks for the panel I am using it with the Martin 4-0-4

[Tom/CalClassic]

Hi,

Ah, ADI. That stands for Anti Detonation Injection, sometimes called water/methanol injection or "wet power". When that switch is thrown, about 1 gallon of a 1:1 water/methanol blend is injected into the carburetor each minute. The methanol is present only as an anti-freeze agent, BTW. This cools the cylinders and allows higher powers to be generated without causing premature detonation in the cylinders (i.e. it's so hot the fuel explodes before the plug sparks). You hear this as "pinging" in your car's engine. In a large radial it can get so severe that you will blow a cylinder head. Each tank (1/engine) can hold 22 gallons of fluid, and you must have 11 gallons of fluid to allow a wet takeoff. You turn it off as you enter Cruise Power (or during METO power if prolonged).

The Convair and Martin flight models assume you are throwing the switch (whether you do it or not) and thus the handling notes tell you to apply full throttle on takeoff. But in real life, if you either decided to use "dry power" instead (or just ran out of fluid), you would need to apply less than full throttle (59.5" MAP and 2800 RPM) - you would need to throttle down to 55" MAP and reduce RPM to 2700. Otherwise you would be risking a blown head.

BTW, if you are taking off at high weights, you should also throw the Autofeather switch, which in real life automatically feathers an engine if it fails. It's turned off at the same time.

On this panel both switches are dummies - they just light up a green light.

Hope this helps,

[Bluegrass1]

Thanks Tom.

I had googled ADI but all I got was "Altitude Direction Indicator" which made no sense.

Hope you and yours have a Merry Christmas.