Home | How do I replace the seals on my doors, wings, etc?

How do I replace the seals on my doors, wings, etc?

How do I replace the seals on my doors, wings, etc.?
Search strings: root seals, door seal installation, replace door seals, door seal replacement, replace seals, replace the seals, door seal cement, adhesive remover, cement remover)

Seems like every A&P has his preferred method. Here is one worth trying, for the doors. I first advise that you download and read the applicable section of the shop manual. Even for tasks that are approved as owner-operator performed maintenance, you are required to have the approved documentation available for reference.

Purchase the following from a good auto refinishing supply story (not Pep Boys):
3M Super Weatherstrip Cement, in the black color.
3M Adhesive Remover
Some small disposable brushes to apply the solvent and cement.
Some Scotch-Brite pad material.
Some plastic, wood, or phenolic scrapers. No metal scrapers on your airplane, please!
A quart of MEK from Home Depot, Lowes, or a hardware store.

Remove the old seals, and all traces of the old cement. Normally, the special adhesive remover will not harm the paint. The MEK will, so don’t use that for the seal removal.

Eyeball the seals against the door area. The seals are designed to be applied around the perimeter of the door frame, not on the inside surface of the door face sheet. In other words, when properly installed, the seals face outward toward the door jamb with the door closed; they don’t face toward the interior of the plane. Most improper seals will be found to be quarter-round in shape, and glued into the corner junction of the door face sheet and the door frame. Again, when properly installed, the bulb portion of the correct seal faces away from the door frame, and toward the door jamb area, when the door is closed. The outer edge of the flat seal base is positioned tightly against the inside surface, of the outside skin of the door, with the one-inch flat seal surface glued to the outer perimeter of the door frame. Photos can be viewed on Page 3 under General Resources/Photo Gallery/Maintenance Photos/Door Handles, Trim, Seals. You will note that the seal has to be slightly notched where the aft center bolt and the top aft bolt extend from the door frame. Quickly apply two thin layers of the cement to the area that will be covered by the seal. If the glue gets so sticky that the second layer is removing the first layer, soften the surface with a bit of MEK.

Lay the seals out flat and straight, but avoid stretching them. Coat them with at least two coats of the same black 3M cement.

When you have everything ready, use a brush to put a fast, thin coat of the MEK over the cement on one door. Immediately position the seal on the door. I prefer to start an end right at the door hold-open brace, under the bottom of the door. The MEK will allow the cement coatings to bond, but it will flash off fast. You need to have the placement planned, and work fast at this stage. You can do the MEK painting in stages, but keep in mind that if the cement on the seal and door touch, they will bond immediately (it is a contact cement). Without the flash coat of MEK, you will have no ability to reposition the seal. It will make a mess if you have to use the remover to lift a mispositioned seal. Take care not to stretch the seal during installation; it is very easy to make this mistake. The seals shrink with age (like all rubber products). If they are stretched during installation, they will crack when they shrink with age.

When you have the two ends trimmed and butted, use a trace of quality Super Glue with matching Accelerator, to permanently bond the two cut ends of the seal. This will assure that they never pull apart in service. Quality cyanoacrylate cement and matching accelerator can be found at any good Hobby Shop.

Leave the doors open overnight; or if the plane is at an outside tiedown, do the work early in the morning, and let the cement cure all day before closing the doors. Coat the seal bulbs with a very thin layer of silicone grease, such as Dow Corning DC-4, before the first closing. Note that more is not better, on the silicone! All you need is a shiny film, not visible grease. If you are planning to re-paint your door jambs during this work, make sure it gets done before the silicone is applied to the seals.

Note that the traditional products for this job are AeroSeal cement and the matching remover. Those products have long been outclassed by the 3M product. Do not try to get by with cheaper copy-cat cements, or you will be disappointed.

Below is another method of installing front cabin door seals. The same method can be used for the large baggage door seals. Those narrower seals require the 1/2" wide tape, and (unlike the front cabin door seals) are applied around the outer perimeter of the inside surface of the door skin. That means that you have to make radius cuts in the tape, where it makes the turns. The large baggage door perimeter corner radius requires notching the 1/2" tape so it can turn the corners. The cuts should be on the inner edge, so that the adhesive line remains unbroken around the outer perimeter of the tape.
1. Go to an autobody supply store (not a Pep Boys kind of place). Buy the large roll of 1” wide 3M-brand black mounting tape (along with the 3M adhesive remover mentioned in the FAQ).
2. Remove the old seals, and all traces of the old adhesive. Wipe the surface down well with rubbing alcohol, and let it dry completely.
3. Apply the tape to the door frame, starting at the bottom just past where the door brace folds in under the door when it is closed. Take care not to stretch the tape. Wrap it around the frame, between the door skin and the door trim plastic (if present). Notch it anywhere needed for latch clearance. Press it firmly into place.
4. Peel off the cover film, and stick the seal into the tape. Get it right the first time. This tape is made to hold emblems and trim on the outside of cars, and it gets a good grip pretty quickly.
5. Put a very thin film of silicone grease (like Dow DC4) on the door jamb (not spray silicone), and try the door.

The only potential drawback to this system is that it adds about 1/32" to 1/16” to the thickness of the seal. If your doors are very tightly fitted, or are sagging on the hinges, they may be very hard to close with the new seals. This can be true even if the traditional cement is used, but the tape thickness will exacerbate it. If that happens, you can use a new snap-off knife (very sharp and long blade) to first trim the rounded bulb off the seal at the forward edge of the door, where the jamb is vertical. It will still seal plenty tight with no bulb there. Don’t trim the angled part where the window is; at least, not yet. If the door still refuses to close, and looks like it is being blocked on the bottom edge, trim the bulb off the bottom. This should enable you to get the door closed, by pushing on it both top and center. It will need to stay latched closed at least overnight, to enable the seal to take the proper conformance ‘set’ for your door and jamb. Some are fitted much more tightly than others. It will close easier and easier over time, as the new seal ‘breaks in’. Avoid trimming the new seal anywhere around the window and aft side of the door, unless there is just no alternative. Air leaks in those areas are what cause most rain leaks, noise, and cold drafts in winter.

The Sierra and Duchess have very large (full size) aft baggage doors. These doors use a narrow EDPM rubber seal. The traditional installation method is the black 3M adhesive. By far the best method is the half-inch wide version of the 3M double-sided tape. The same cleaning is required, but the final installation is a piece of cake if the tape is used. The seal does not wrap around the door frame, as it does on the front cabin doors. It instead is adhered to the inside of the door face, near the outer perimeter, with the seal lip toward the door jamb.

The wing root seals are far more work. They have usually been all gunked up with boot repair compound, wing-walk paint, and God knows what, over the years. After removing the old seals, you have to use Scotch-Brite pads, scrapers, Roto-Loc discs, etc.,and adhesive remover, to get all that old stuff off. You might also need to apply some touch-up paint, and let it harden, before installing the new seals. You’ll need something like heavy-duty Popsicle sticks to work in the new seals. For most of the length of the wing it isn’t too bad a job; but it will be a bear right at the nose of the wing. Beech made the fit tighter there, to make sure the wind blast could not get under the seal there.

One good aspect of the wing root seals is that they need little or no adhesive, as a rule; perhaps just a bit at the ends. You can apply rubber lube or Armorall, or 409/Fantastik to install them. Silicone grease (like DC4) works, but you’ll play the devil doing any gluing, or future touch-up painting, anywhere it touches.

The vertical stab seals are pretty easy to replace. The old ones come off pretty easily, and it isn’t very hard to clean the area. The new ones are installed using the black 3M adhesive, or you can use the narrow version of the double-sided 3M tape (as can also be used on the large baggage door seals on Sierras and Duchesses). Proper cleaning is critical. Depending on circumstances, you may also find that when the new seal is positioned for best security and appearance, you have a narrow strip of bare metal showing that will need to be painted with touch-up paint. Not a big deal.


I’m afraid that it sounds like some owners have either used the wrong door seals, or installed them incorrectly. If you do a BAC search on ‘door seal installation’, you’ll find complete instructions. If you look in General Resources/Photo Gallery/Maintenance Photos/Door Handles, Trim, Seals, then view the last two photos (NewSeal 01 and NewSeal 02), you will see how they should look once installed.

The doors will initially be a bit snug with a new seal installed. You wipe a very thin film of DC4 silicone grease (not canned spray) on the new seal surface, and close the door. Make sure it is snugly pressed into the frame all the way around. Then you leave it that way for a few days. After that, it should close fairly easily, and should take no significant handle force to open. Most of those I have worked on will open and close just like a car door.

If you still have an area where the sealing is poor, due to a warped or poorly fitted door, you can go by Lowes or Home Depot and pick up a very small seal made of EPDM rubber. It is the Frost King brand, #V27W, SKU Code 077578012551. Identify the portion of the door perimeter where you need the additional sealing. Clean every trace of silicone off, using a commercial silicone removal product from an auto body supply store (follow the instructions exactly). Then apply a single-wide strip of the auxiliary seal (it is self-adhesive). This seal will offer no additional resistance to closing the door. It is very small (3/8” wide by ¼” thick, hollow-core), and is made of extremely compliant EPDM rubber. It is white, so it will blend in with the paint. If your door jambs are unpainted aluminum-gray in color, you can choose PN V25G instead (gray seal stock). Note that these tiny seals are not suitable for primary sealing; only for addressing any remaining problem gaps.

If your windlace trim is old, hard, or too small, that will be part of your sealing problem. That is the rounded trim that sticks up around the door opening, as a part of the interior upholstery. It is supposed to be flexible, and to cover the door gap with the door closed. The airflow being drawn out of the cabin pulls the windlace against any leaking areas.

Many of the doors have been damaged along the way, by people who installed the wrong seal material, or put in on incorrectly. This can spring the doors, and can even break the piano-style hinges over time. With the doors closed, they should be pretty flush with the outside skin; and it should take almost no more force to operate the handles, than it does when the doors are open.

Addendum December 2009:
The early -124 cabin door seals will also fit and work very well on many of the ME-prefixed Duchesses, and many of the 1979 and later Sports, Sundowners, and Sierras that came with the later Duchess lip-type seal. One caution, though. We have encountered a small number of 1980 and later airframes that have an uncommonly small door skin flange extending beyond the door’s inner frame. There must be at least a 3/4" wide ‘flange’, between the door’s inner frame and the edge of the door’s skin, for the Beech -124 seal to work well. If you have a 5/8" wide flange, or narrower, on the majority of the door’s perimeter, you need to stick with the slightly smaller AECI seal. If the flange is as narrow as 1/2" or less, you’ll have to stick with the later lip-type seal design, ordering it from Brown Aircraft as explained in the BAC FAQ, and hope for the best. Paying Beech more than $700 for the Duchess lip-type seal is out of the question for most of us.

If the door has the needed clearance in all areas but one or two, and the door’s overall gap really needs the original wider Beech seal, the seal can easily be trimmed as required for the narrower segments of the door skin’s flange. You just slit the outboard edge of the seal’s protruding bulb with a razor knife, after it has been installed, leaving a very slight ‘lip’ sticking above the seal’s base section. Then cut a sliver of rubber off of the cut edge of the bulb, tuck the cut bulb edge down, behind and against the small lib protruding from the base part of the seal, and see whether the seal height versus the door clearance looks correct. After removing the correct amount of bulb rubber, permanently reattach the cut edge of the seal, behind and against its opposite cut edge, using Super Glue and Cyanoacrylate Accelerator. If you prefer, you can reattach the cut edges; but this is usually more difficult as the cuts are hard to get exactly parallel. The cyanoacrylate rubber bond will be permanent within one or two seconds. The seal will tear before the cement fails. You must use the accelerator to get this quality of bond.

Thank you for adding to the resources available for your Fellow BAC Members.