We are receiving many calls and emails from shops and mechanics that are taking on the job of the spar replacement on the 210. This article is in response to the questions we are being asked, but please don’t consider it a training manual or instructional procedure. I wrote an article back in late 2017 showing replacement of the carry through spar on a Cessna 177. It’s not exactly the same as a 210, but the process is very similar. For a structural shop or experienced sheet metal mechanic, it’s a very straight forward job. For the uninitiated, it can be very intimidating.
Wing removal is the first and most obvious step. The service manual actually has a good procedure for this process. The unknown would be any aftermarket modifications such as avionics, speed brakes, or tip tanks that would complicate the process. Overhead oxygen bottles is another complication that can add a full day to the labor hours. Be sure to label and take pictures of everything. You never know how important that one picture will be when you can’t figure out how to mount that green widget in the right wing.
The cabin forward top skin and the two bulkheads on top of the door frame between the main spar and the forward spar get drilled and removed. At this point the primary structure keeping the aft of the airplane from dropping to the floor is the belly structure. We recommend supporting the engine weight by lifting lightly at the engine lift loops. A tail stand at the aft tie- down ring is helpful as well. Very precise removal of all those rivets is critical so that replacement rivets won’t need to be oversized.
The primary attachment of the spar to the airframe are twelve large bolts. The holes in the spar and the airframe are all precision positioned and drilled. Any spar of the correct part number will bolt in place using these holes. Be sure to inspect the bolts closely prior to reinstallation or just install new ones. If installing a used donor spar, you can expect the rivet holes to not match 100%. New spars from Textron do not come with rivet holes predrilled, allowing them to be match-drilled in situation to the existing airframe rivet hole pattern.
Once the spar is bolted in place, all the other structures can be clecoed (temporary fasteners) in place. The more clecos used, the more solid the fit and alignment. There’s no need for jigs or alignment devices. With about 50% of the rivet holes clecoed, an assessment of the remaining holes for alignment can be performed.
I do recommend applying sealant between the skins and the underlying structures to protect from water intrusion. The mating between the spar and the cabin top skins in particular should be sealed. There will also be gaps around the ends of the spar and the attaching structure which should all be sealed. Standard fuel tank sealant works best and does a good job protecting whatever it sticks to from corrosion.
One would think it’s more complicated than that, but it isn’t. The real complication comes in all the other problems one finds with this much of the plane taken apart. There’ll be new corrosion places found, wires that go nowhere, headliners that fall apart, speaker cones that turn to dust when disturbed, fuel lines that leak, and so on. Just be prepared, and try not to get frustrated.
Copyright © Paul New 2021. All rights reserved.