lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> A friend had this happen to his 360: On final one of the greens suddenly went out, and then on again. He made a go around, and after some thinking pulled the gear circuit breaker to deactivate the electrics, made sure there was 3 greens, and landed. Unfortunately, while he was taxiing in, he reactivated the circuit breaker and the gear retracted. The problem was that the gear up circuit was connected to a warning horn, which was also connected (via a separate input) to the header fuel low switch. When the header fuel low horn activated when dipping the nose on final there was a creep current through the horn activating the gear up circuit for short moments. Do you have anything else connected to the gear up circuit ? So a short to +12V definitely will cause the gear to go up. The way the hydraulic system is built, the fluid is released to the tank via a pressure valve, so there will be a pressure generated in the down side by the retracting cylinders. This is possibly enough to open the down pressure switch. Since the squat switch closes as you slow through 95 mph, a short will activate the gear up circuit at a time when the pilot is concentrated on final approach, or initiating flare, and certainly not checking the green lights. Increasing this to 110 mph would visualize a problem while you were looking at the lights, but would not allow you to retract during a Vy climb after start, if you ever need that, so I think the squat switch should not be changed. Another possibility is of course the mouse, or vibration abrasion. I wired the gear warning circuit of my 320 by connecting the NC terminal of all 3 gear microswitches together, and via a flap position switch to the gear warning horn. This way I will get an audible indication if any gear momentarily becomes unsafe. Something else to consider is the orientation of the relays, even if this shouldn't be the problem here. Sometimes the spring breaks, so they should be mounted to give the desired function in this case, i.e. main on, starter off, gear relays off. This can also happen when you fly into turbulence, you can get a couple positive G that will overpower the spring, and you don't want this to power on your starter! Sven Jerlhagen LNC2 SE-XOP >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>