Lead Counterweights on B-models
Posted: Mon Apr 22, 2002 4:29 pm
Cleo Bickford is even pickier than I am! (If you can believe that!) He pointed out that the counterweights on my 170-B model is the only one he's ever seen that are attached like the Illustrated Parts Catalog shows. The Parts Catalog shows the lead weight attached with 4 rivets. (B-models only,...the 170 and 170A do not have counterweights.) The interesting thing about that is,...How do you fasten those rivets? Since you can't "buck" them in the traditional sense because they are embedded in solid lead, ...how are they fastened?
The Parts Catalog list them as two each NAS445-163C-4-2, and NAS445-163C-4-8 rivets. I've not found a hardware listing/description of those type rivets, but looking at my airplane, if that's what these are, they are very similar to "Cherry-Max" rivets, and appear to be self-expanding.
(That's what it appears on my airplane anyway.)
Looking at other airplanes on the ramp, if you allow the elevator to fall completely into the nose-down position the counterweight can be viewed. Look at the inside edge (vertical surface) of the counterweight area, alongside that full-length rib of the counterweight horn. You may find two screws, either MS or PK style, that screw into the lead weight to hold it in position. At least that's the way it's been described to me, and that's how other airplanes are typically found. The Parts Catalog do not show these. I suspect they've been added either by subsequent Service Letter, or by well-intentioned mechanics. Either way, I think there's a danger here.
DURING PREFLIGHT INSPECTIONS, be absolutely CERTAIN that those screws, if installed, are in-place and FULLY screwed in. (Don't strip them out in that soft lead or they'll work themselves out.) If those screws are there, and if they back out of that lead, not only can the lead become dislodged and send your elevator counterweight data into never-never-land,...but the screws could interfere with the horizontal stabilizer and LOCK YOUR ELEVATOR UP IN FLIGHT!!
The Parts Catalog list them as two each NAS445-163C-4-2, and NAS445-163C-4-8 rivets. I've not found a hardware listing/description of those type rivets, but looking at my airplane, if that's what these are, they are very similar to "Cherry-Max" rivets, and appear to be self-expanding.
(That's what it appears on my airplane anyway.)
Looking at other airplanes on the ramp, if you allow the elevator to fall completely into the nose-down position the counterweight can be viewed. Look at the inside edge (vertical surface) of the counterweight area, alongside that full-length rib of the counterweight horn. You may find two screws, either MS or PK style, that screw into the lead weight to hold it in position. At least that's the way it's been described to me, and that's how other airplanes are typically found. The Parts Catalog do not show these. I suspect they've been added either by subsequent Service Letter, or by well-intentioned mechanics. Either way, I think there's a danger here.
DURING PREFLIGHT INSPECTIONS, be absolutely CERTAIN that those screws, if installed, are in-place and FULLY screwed in. (Don't strip them out in that soft lead or they'll work themselves out.) If those screws are there, and if they back out of that lead, not only can the lead become dislodged and send your elevator counterweight data into never-never-land,...but the screws could interfere with the horizontal stabilizer and LOCK YOUR ELEVATOR UP IN FLIGHT!!