Hi Im flying a 1963 250 and trying to find a way to have the Landing gear horn come on at a lower throttle setting or manifold setting. I am at 4,000 msl and when I pull the throttle back to 15 inch's for landing I can't keep from having the gear horn go off. And as I go lower I get more manifold pressure and I cant back it off anymore or the horn goes off. It should be set about 10" manifold pressure is there anyway to adjust this on the throttle control? I don't like to extend the gear above 130 indicated airspeed. Thanks for any help with regards to this matter. Ed G

Ed, check out the recent post in airframes under the heading Gear Waring System Micro Switch adjustment.
viewtopic.php?f=94&t=7170&start=0#p57105

Gary

Ed,

Don't know if the single gear warning horn works the same as the Twin's already under discussion. Is there something in the single service manual on this?
http://www.comancheflyer.com/NS/index_serv_manuals.php

It is not a difficult adjustment. It is a mechanical switch attached to the throttle cable and can be move to affect a change in the MP trigger point. That said we have ours set to go off at 15 inches and we don't have a problem with that but everyone is different. 10 inches would make it worthless for me.

Don

Well thanks for the input on the Landing gear audible horn for a 250. I think its quite different from the twin comanche setup. Im in the middle of an annual so will see if the A&E knows anything about an adjustment. I looked at it and couldn't see an adjustment of the contact switch attached to the throttle. I will look at it again. Thanks Ed

Edwin,

Adjusting the switch is really easy on the single. I suggest you measure the throttle position when the engine is producing the desired manifold pressure and then use that measurement to make the adjustment on the ground. The adjustment is right behind the panel on the throttle cable.

That said, I have my 180 throttle set to blow the horn at 15" also and think that 10" is way to low. I believe the horn should be blasting any time I'm in the pattern for landing and not just when the throttle comes completely off during the flare. Be careful!

PatD

If the throttle has been replaced with a venire control type the switch and adjustment is on the carburetor arm. Easy to get to. I have mine set at 14/15" MP. I agree with Pat, 10" is way too low. Ray B

Edwin,

I echo Pat D and Ray's thoughts on setting it too low. In my Twin the recommendation is for 12 inches. I don't get to 12 inches until I'm so slow on final, it would be difficult to go around. I have the warning horn set at 14-15 inches so it would sound on the initial part of final. I fly the pattern at 17 inches so the 2-3 inches are an adequate buffer.

As you may have seen from my other post, I'd like this to be more consistent. At items the warning horn comes on when I'm entering the pattern at 17 inches. I can up the inches and bring the throttle back more slowly and that sometimes works but by the time I finish that process, it is time to lower the gear anyway.

BTW, I also normally do power on descents - as recommended by the guy that did the engine overhauls. It was my style already so no change for me but it might help in your situation. I cans see where that might be a bit more challenging in Utah. Since I've raced at max power into several mountainous areas, I know it can be done, just takes more planning and some practice. Can't always do that though - even in the flatlands around Tulsa steep descents can be required, I had a controller leave me at a very high altitude with few miles to the airport. I wasn't interested in circling so I pulled the power, raised the nose, dropped the gear, dropped the flaps and sank like a stone - not the power on descent I prefer but really great for dropping altitude fast. It is one of the techniques taught at the Comanche Pilot Training Program.

Hope sharing these thoughts helps in your situation.

I have a 260B with a vernier throttle and the switch is on the throttle cable just behind the FI throttle body. Very obvious.

Don

Ok, Thanks for all the input, I will try an adjustment and we will first try 14", that will probably do the trick. Ed

Just replaced my throttle cable with a new one from McFarlane. Setting the gear switch was super easy - I have it coming on at ~14.75" - mechanic and I took off, flew to several thousand feet, pulled the throttle back to ~14.75" and measured how far out from the panel the throttle knob was. He adjusted to that setting on the ground and it works great. I normally descend at 15-16" so I wanted the horn to come on just below that setting so I have plenty of warning if I forget the gear.

The way switch works is pretty simple: The metal shaft of the throttle handle extends in through the friction lock and turns into a metal cable. There the shaft tapers down to the cable is there a little switch arm sticks. When the switch arm is laying on the shaft, it silences the horn; when the switch arm drops because it's laying on the cable it activates the horn. You just move the switch assembly fore and aft to the right spot to activate at the desired setting. If you move the throttle in and out with the engine off, you can hear and feel it tripping that switch on and off. That all being said, it's not a super high-precision thing so another good reason to have a little safety room built into when it comes on.

Matt, I'm interested in why you changed out your throttle cable, was it worn out?

The leather friction lock pooped out last spring and I got advice from Webco for a brass ferrule as an owner-produced part but that essentially was either "locked" or "unlocked" rather than being able to provide just the right amount of friction.

As it got colder this winter I began having trouble with my prop lever getting really stiff, almost to the point of putting my foot on the panel to pull it out. Since my prop, mixture, and throttle cables were all original I decided to bite the bullet and replace them all with new McFarlane cables. The Mix/Prop were off the shelf but throttle is custom-made with a 337. They are all Teflon coated and the mixture and prop controls are verniers. Night and day difference. I love them; they work great!