Lest anyone think I am picking on them about this, let me make it clear that there are going to be a lot of guys read this and laugh and cry right along with me because they have also been there.

One of the areas we had a lot of problems with in the olden days was with the position switches which must be out in the gear wells. The owners of any kind of certified seaplane will tell you of how much trouble gear position switches are. Even the supposedly sealed switches which are required on certified planes just can’t hack the environment they have to work in for very long. I tried them on my Seahawk. Nothing but problems. Most automatic type circuits meant to control the gear depend on the gear position switches to control the pump. Whether through a solenoid or direct, this makes the entire system dependent on 6 separate switches to operate correctly at all times! SIX things to possibly go wrong. And the kinds of switches folks normally use for this application are PROVEN not up to the task. And I’m talking about the best sealed switches you can buy. The kind required by certification to be used on certified seaplanes! If the gear position switches are not a part of the circuitry for controlling the hydraulic pump and they are only operating gear position lights, then they can be switches which are capable of carrying only the current required by the single small position light they each operate.

This means that a very small encapsulated magnetic reed switch can be used. Since the switch is totally sealed from the elements and is activated by a magnetic field, it has no moving parts and water can not get into it to short it out. In all the years since I started using these switches, and through all the hundreds of water landings and takeoffs I have made, and through the plane sitting for as much as a week in the water at times, I have NEVER had one fail on me! Every other sealed switch I ever used gave me

Another approach that has been tried (and is still being tried) to controlling the gear pump is to use pressure switches which shut the pump off automatically when the pressure in the system reaches a certain preset point. The theory is that this way all the pilot has to do is flip a selector switch to make the gear go up or down and the pressure switch knows when the gear has reached it’s destination because of the pressure increase, and turns the pump off until the pressure goes back down or the pilot selects the other direction. This eliminates the burdensome task of using one switch to select the direction of travel and another to turn the pump on and off. Until this was explained to me, I just couldn’t understand why I was having all these terrible pains in the fingers I use to switch those 2 switches twice on every flight? I’m sure that this is responsible for all my arthritis problems and probably pretty soon I’ll be impotent as well! And all just because I was having to switch those 2 little switches!

That’s enough levity. Seriously now, I tried pressure switches 10 or 12 years ago and had the same problems I know other people are having that try them. Most of the pressure switches are just too sensitive to work in our application. They have a fairly narrow operating range. In our system, once the gear has retracted, and the pump is shut off, there will be a slight drop in pressure. This is caused by the slight delay in the check valve closing and other factors. Say the pressure switch is set to cut the pump off at 1700 pounds and the switch has a 10 pound range in which it is either off or on. If the pressure drops back 10 pounds when the pump shuts off, the switch will turn it right back on and the pump will cycle over and over until a human does something to stop it! Since you can’t necessarily hear the pump running when in flight, if this condition develops in flight, the pump can cycle on and off through the whole flight, or if there is a light that indicates when the pump is running and the pilot notices what is happening, he can trip the breaker to shut off the pump. I guess that’s comforting, but it doesn’t seem so to me.