garysuperpilot Posted July 6, 2014 Report Posted July 6, 2014 Just got my first annual on my M20 F model with no major problems. Plane did have a gear retraction issue for the second time,however since I've owned it. I took off, everything looked good and the gear did not go up when I put the wheel up. I put the wheel down and back up again and it retracted properly. The plane did the same thing once last year and I had the mechanic check it out and we could find no faults. Of course it retracted properly when it was on the jacks. Flying up to a little mountain airport in New Hampshire for a wedding next month and would hate to fly 700 miles with the gear down. Any ideas what to look for? Maybe the switch itself? We didn't remove it last time. Quote
tony Posted July 6, 2014 Report Posted July 6, 2014 There is a pressure switch, If you gently blow into the pitot tube your gear will go up. Quote
garysuperpilot Posted July 6, 2014 Author Report Posted July 6, 2014 Now that you mention the pressure switch I wonder if I am retracting the gear sooner than the switch is allowing the gear to go up. Is there an adjustment on the switch and what airspeed would it normally allow the gear retraction? Quote
Hank Posted July 6, 2014 Report Posted July 6, 2014 The only times I've had trouble with gear not retracting was during cold weather. The unanimous decision here and on the MAPA lists was that I needed new gear pucks. Swapped them out and had no further problems. My gear is usually fully retracted by treetop level; I rotate at 70 mph and climb at Vx to clear the trees, but on long runways I accelerate directly to Vy. Quote
DaV8or Posted July 6, 2014 Report Posted July 6, 2014 OK. You got me. Why would the condition of the gear pucks make any difference? Quote
Hank Posted July 6, 2014 Report Posted July 6, 2014 OK. You got me. Why would the condition of the gear pucks make any difference? Old pucks get hard and lose resiliency. Both Maxwell and LASAR chimed in that old pucks don't retract well in cold weather. But if I had time, I could put a heater on each main gear for ~30 minutes before flight [or move into a heated hangar, rarely an option] and they would retract just fine. Nothing like hearing that buzzer for 20-30 minutes as one wheel is stuck partially extended [6-8"], and suffering ~10 knots loss from drag. With new pucks, departures well below freezing present no retraction issue; with my old pucks, problems began in the high 40s, and an extension and second retraction on initial climb would sometimes work at these higher temps but not at freezing or below. There was a lot of that along the Ohio River . . . Quote
garysuperpilot Posted July 6, 2014 Author Report Posted July 6, 2014 Never thought of the pucks presenting a problem either. I live in North Carolina and both events happened when it was well in the 80s so don't know if that would be relevant or not. I was also told the logs said, and my mechanic agreed the pucks look a year or two old. Quote
Marauder Posted July 6, 2014 Report Posted July 6, 2014 OK. You got me. Why would the condition of the gear pucks make any difference? The F models can have either an air switch or a squat. If he has the squat switch, old donuts may not expand enough once the weight is off the wheels to allow retraction. The issue is more pronounced in cold weather. Quote
garysuperpilot Posted July 6, 2014 Author Report Posted July 6, 2014 Don't know for sure what type of switch I've got but I know you have to blow into it to have the gear retract. Does that mean it's an air switch or is it a safety they have in common? Quote
jnisley Posted July 6, 2014 Report Posted July 6, 2014 Our 1969 F has an air switch, how do I know? 10 years ago we had our plane in the shop to do a panel upgrade along with some "under the cowling work", as usual after someone works on our plane we do a test flight, my partner and I did several run ups and double checked everything, I even remember confirming that the green gear down light was lit, what we failed to notice is the gear lever in the up position. At takeoff, around 60 mph, while still on the runway the gear retracted.....well, you can guess the rest of the story. We soon discovered what happened, the mechanic put the gear lever up and forgot to put it down again, two pilots that had more pressing things to think about didn't see it, the air speed safety switch (that was supposed to make this a non event) was set too low allowing the gear to retract before the plane was flying.....I hate when that happens! Quote
garysuperpilot Posted July 6, 2014 Author Report Posted July 6, 2014 Wow. Now I feel happy the gear Didn't go up! If all I have to do is go a little faster to have the gear go up I could live with that. Still, I'd like to be more certain what's going on. At least it always goes down. Could be worse. Quote
Marauder Posted July 6, 2014 Report Posted July 6, 2014 Don't know for sure what type of switch I've got but I know you have to blow into it to have the gear retract. Does that mean it's an air switch or is it a safety they have in common? Depends on the year. I think a good part of the electric gear fleet from the 60s are on air switches. My 1975 has the mechanical squat switch. Sounds like you have the air switch. Quote
Hank Posted July 6, 2014 Report Posted July 6, 2014 My 1970 has the squat switch, thus trouble retracting in cold weather with old, hard pucks. New ones not only retract better, they land smoother and make for almost magically nice taxiing. Quote
Guest Posted July 7, 2014 Report Posted July 7, 2014 Before you even consider blowing into the pitot head please raise your plane safely on jacks. Testing is simple, once on jacks, roll a long piece of surgical rubber tube ont to the pitot head. If you can't get it on far enough you may have to tape the small vent hole on the lower surface of the pitot tube. Place a cloths pin about 3-4 feet from the pitot head sealing the hose, , start slowly rolling the hose around the clothes pin, the air speed will increase on the indicator. Verify that the gear retracts at the correct speed for your model. With a second clothes pin trap the pressure in the hose, if it leaks down find and repair the leak. Clarence Quote
garysuperpilot Posted July 7, 2014 Author Report Posted July 7, 2014 That sounds like a good plan I can try with my mechanic. I know the gear retracted when tested but I don't think we checked the airspeed indicator for correct speed obtained to let it retract. I'll try that next. Thank you Quote
DaV8or Posted July 7, 2014 Report Posted July 7, 2014 Before you even consider blowing into the pitot head please raise your plane safely on jacks. Testing is simple, once on jacks, roll a long piece of surgical rubber tube ont to the pitot head. If you can't get it on far enough you may have to tape the small vent hole on the lower surface of the pitot tube. Place a cloths pin about 3-4 feet from the pitot head sealing the hose, , start slowly rolling the hose around the clothes pin, the air speed will increase on the indicator. Verify that the gear retracts at the correct speed for your model. With a second clothes pin trap the pressure in the hose, if it leaks down find and repair the leak. Clarence This is exactly how they do it every year on my plane at LASAR. Really simple and effective test of the switch. Quote
rbridges Posted July 7, 2014 Report Posted July 7, 2014 OK. You got me. Why would the condition of the gear pucks make any difference? glad you asked. I was wondering the same thing. Now I can pretend I knew all along. 1 Quote
Ron McBride Posted July 8, 2014 Report Posted July 8, 2014 My 69F has the airspeed switch. the maintenance manual calls for 75 to 80 MPH. If it is higher, you will really wish it was lower in a high density altitude takeoff. Ron Quote
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