How to Annual Your Falco

by Stephan Wilkinson

This article appeared in the March 1993 Falco Builders Letter

The first thing you need to do is get an FAA repairman's rating, which allows you to maintain, inspect and sign off the airplane you've built (and only an airplane you've built). Get an application from your GADO or FSDO, fill it out and submit it; that's all you need to do. (My application form said I needed to appear in person at the GADO and submit three passport-type photos, but that's no longer required.)

The order in which you do things during an annual inspection is largely immaterial, it seems to me, other than making sure you remember to do the retraction test while the airplane is still up on jacks after doing the wheels and brakes, that sort of thing.

I tend to do things by "category"-i.e. all filters, or all greasing, or all control-system oiling-while other people work from area to specific area of the airframe. As long as you have a checklist, either method works. (I do preflights the same silly way-all the fluids first, then all the control surfaces, all the lights, etc. So I end up making about six laps around the airplane. But at least you won't look quite as foolish doing it that way during an annual.)

If for some reason you want a licensed shop to do your annual, you might be surprised by the reluctance of some A&Ps to undertake the job. Not so much because they don't know the airplane but because they have no interest in taking responsibility for signing off an airplane the build quality of which they have no way of determining.

In the case of my airplane, I did the entire airframe annual, changed the oil and filter, cleaned and gapped the plugs and then took the airplane, still uncowled, to a shop on the airport to inspect everything firewall forward, check the timing and compression and do whatever else they'd routinely do to an engine and prop during an annual. (No signoff required-I just wanted them to do the work.) I'm confident inspecting the airframe that I built, but I still feel a little leery of messing with an engine and prop. It also gave somebody who knows what he's doing the opportunity to confirm that my installation was correct in every detail.

For example, last time the same A&P looked at the engine, he noticed that I'd never installed the drain line and weep valve that clears the intake manifold of puddled fuel and prevents flooding during hot starts. The engine came from Mattituck with the hole in the oil sump plugged and no line installed, and I never knew such a thing was standard.

This time, he discovered that the shop that had dialed the crank and replaced the prop after the airplane's gear-up landing a year ago had refitted the starter ring-gear flange one stud off its proper orientation-supposedly impossible to do, but they'd somehow forced it into place-and as a result all the prop nuts had lost their torque, and I'd been flying around with essentially a loose prop. Nice, huh?

You might also want to consider establishing an annual-inspection schedule that puts your airplane down during a time when you wouldn't be flying much anyway-winter in New England, say-rather than having your airplane in pieces in the middle of July. Of course, that presupposes a hangar, but who leaves their Falco outdoors anyway?

I highly recommend, by the way, Kas Thomas's book Personal Aircraft Maintenance: a Do-It-Yourself Guide for Owners and Pilots, available through several mail-order aviation booksellers. [Check our the Kas Thomas's TBO Advisor website] Lots of hints, diagrams and photographs entirely applicable to a Falco.

FAR 43 Appendix D lists the scope and detail of items to be covered in an annual, and essentially it says to inspect literally everything in and on the airplane. It says nothing about lubrication, maintenance or servicing; that's up to you, unless it's required to bring the airplane into compliance. Elsewhere in Part 43, it says you have to use "a checklist while performing the [annual] inspection. The checklist may be of the person's own design, one provided by the manufacturer of the equipment being inspected, or one obtained from another source." Here's the one I invented. It certainly doesn't cover every nut, bolt, bracket and switch, but I think it hits all the big stuff:

Remove seats. Starting right here, it helps to have a bunch of plastic baggies (and a Magic Marker with which to label them) so you can keep the various categories of screws and fasteners separate.

Remove all floor and baggage-compartment carpeting.

Remove baggage-compartment rear bulkhead.

Remove baggage-compartment floor.

Remove center console. (Aft-most fiberglass section of console can be left in place, negating the need to remove the center seatbelts, and you'll still be able to lubricate the flap actuator.) Don't be surprised if you find a large bird's nest in the center tunnel. I did. The buggers apparently use the jackscrew opening in the wheelwell as their front door.

Remove cockpit flooring above control stick/aileron/elevator control mechanism interconnects.

Remove all inspection panels: tailcone, aileron-bellcranks, landing-gear-trunnions, autopilot if applicable, wheelwells if applicable.

Remove all removable rudder, elevator and aileron hingepoint fairings, if you have them.

Remove entire engine cowling.

Remove all asbestos heat tape from exhaust system, if applicable. Inspect entire exhaust system carefully for cracking. Inspect exhaust-gasket flanges for signs of leakage. (If you're Tony Bingelis and don't trust using hot rod heat tape on the exhaust system, don't replace the tape. Mine was on for 140 hours with no ill effects, so I think I'll renew it. You can't re-use the tape, by the way; it disintegrates once removed.)

Remove cabin-heat air muff. Inspect interior for cracking. Replace cabin-heat air muff. (Now's the time to do something that might give you more cabin heat on cold days, such as stuffing the muff with stainless-steel metal mesh or something.)

Check the alternator belt for proper tightness (about a quarter-inch of displacement possible with moderate thumb pressure) and adjust if necessary.

Remove battery. Clean, top up electrolyte if necessary, check cells with hygrometer, replace and re-safety battery hold-down wingnuts. Replace the strip of baking-soda-soaked paper towel that you ought to have resting atop the filler caps to absorb outgassing.

Check the prop for nicks and any signs of oil leakage. If you know how to dress out nicks, do it. Otherwise, learn. It's more than just a matter of taking a big rat-tail bastard file and whacking away.

Remove and replace the induction-air filter element. It takes a Brackett 5805 element-same size as certain Cessna 172s and 177RGs, though oddly enough, you won't find it in the Aircraft Spruce or Wicks catalogues.

While we're doing filters, also replace the foam-rubber filter element for the vacuum-system regulator valve.

If necessary or advisable-500 hours is the normal recommended time-also replace the vacuum-system inlet filter.

Check the vacuum-pump outflow tube for signs of excessive carbonization, which would imply a pending pump failure. (A slight amount of carbonization-blackness-is okay, since this is how the pump lubricates itself, but the tubing should at least be unmistakeably translucent.) Check the vacuum-pump Garlock seal for leakage.

If you're anywhere near oil-change time, now's the time to do it, since you've got the engine uncowled anyway. Change the filter as well, of course, and open and inspect the can and element carefully.

After inspecting the engine compartment for any evidence of existing oil leaks or other anomalies, wash down the engine with Varsol or other appropriate solvent. (Remember to plastic-bag your vacuum pump, since introduction of solvent into the pump during an engine wash is the leading cause of vacuum-pump failure.)

Ideally, you'd now do a runup and leak check, but you might want to wait till you've got the airplane put back together. As long as you do remember to do it. FAR 43 requires a runup as part of an annual, whether you've changed the oil or not, and you're supposed to "determine satisfactory performance" of the static and idle-rpm power output, magnetos, fuel and oil pressure, and cylinder and oil temperature.

After you've done the runup, when the engine is warm, check and if necessary reset the idle and idle mixture. You check it by pulling the throttle back to idle, then slowly closing the mixture. You should get a 50-rpm rise just before the engine begins to die. If the engine flat dies with no rise, your idle mixture is too lean. If you get more than a 50-rpm rise-it can go as high as 300-400 extra rpm-it's too rich. If you don't know where it is, have somebody show you the idle-mixture adjustment. It'll be stamped with an "R" and an arrow showing the direction to turn the thumbwheel to richen the mixture. Adjust it a click at a time unless you're way too rich or lean. The idle speed itself, once you have the mixture right, should then be adjusted for about 600 rpm. An idle set too high will make it hard to do short-field landings-you'll have too much residual power with the throttle closed-and if it's too low, the engine can die on rollout. Or, worse yet, on short final.

Pull sparkplugs, clean and check gaps. Regap if necessary. Avoid sandblasting the plugs unless truly necessary; pick loose whatever deposits that you can, and remember that sandblasting does more damage to plugs than anything else.

Replace bottom plugs, carefully using thread lubricant and proper torque. Use new washers or heat-anneal and quench existing copper washers before reusing them.

If you have access to a compression tester and know how to use it, check compression of cylinders using top plug holes. (You should understand that interpreting a compression test properly takes a bit of skill; get an A&P to explain the vagaries of the procedure, if you can.)

Replace top plugs.

If you have a timing tester, check timing of magnetos.

Check entire engine compartment visually for fraying, rubbing, loose wires, leaks, protruding connecting rods, etc. etc.

Check for any airworthiness directives that might affect your engine and/or propeller. And, of course, comply with them. (Unless, like me, you have what the local GADO considers an "experimental" engine...)

Put the airplane on jacks with the tail on a jackstand and appropriate weights on the horizontal stabilizer-I put old Army blankets under three or four solid cinderblocks-and remove the main wheels, repack the wheel bearings with grease and replace. If this is the first time you've ever checked the wheel bearings, you may notice that the axle-nut adjustment was looser than when you'd installed the wheels. Apparently-at least on my airplane-the bearings and axle spacer took a "set" between the time I first snugged up the axle nut and then later rechecked it. The perfect axle-nut setting is exactly at the point where all play is taken out of the bearings-you can't rock the wheel laterally at all-yet you can spin the wheel and feel no physical pressure forcing the bearings against the races. But be careful; the adjustments available via the large axle nut are relatively coarse, and tightening the nut one castellation can move the bearings from too loose to too tight. Too loose is better; too tight will cause the aluminum axle spacer inboard of the wheel to gall. If you have high time on the airplane, you might want to do the nosewheel bearings as well, but I don't think it's necessary to regrease those bearings every 100 hours or so.

At the same time, check the brake discs for scoring and the brake pucks for wear. If the pucks are getting close to worn too thin but still have some life left, you might want to reline them anyway, rather than going through the whole jacking and wheel-removal procedure again three months later.

Check the level of fluid in the hydraulic reservoir. If your brakes have been getting spongy, now's the time to bleed them. Using a homemade "pressure pot"-it's quite easy to fabricate one-will allow you to perform the much easier and cleaner pressure-bleeding method (i.e. from the bottom up, rather than by gravity from the reservoir down).

Check tire pressure, all three tires; it should be 30 psi cold.

If your main-gear struts need replenishment and you're near enough to a shop that has a high-pressure bottle, get them to bring it over and give you 600 psi in each strut, which must be done with the airplane on jacks. Or at least with the wheel off the ground, which you can do, if you have a strong back, by getting under each wing and acting like Atlas. Nosegear strut takes 115 psi-normal air-compresser or shop-air bottle pressure-but this also requires that the nosewheel be off the ground, else you'll get a faceful of hydraulic fluid. Trust me. I did.

While the airplane is on the jacks, run a retraction test. (I like to do this by first placing the gearhandle in the up position with the master switch off, then activating the master switch while standing in front of the left wing root. Then I can watch the gear in progress.) Ideally, to do an accurate test of the gear and doors, you should swing the gear while the airplane is being powered by not only its own battery but the battery of a running automobile, to simulate the power of a battery in flight, and you should push against the nosegear with what you imagine to be the pressure of the slipstream helping it retract.

Do you need a static-system and/or transponder check for legal IFR flight? Now's the time to get it, while the systems are exposed.

Oil all external control-system hinges and pushrods with Tri-Flow.

Oil and grease (Mobil 28 red grease), as appropriate, all pivot points and rod ends at the aileron bellcranks, accessible through underwing inspection hatches.

Grease all three landing-gear jackscrews lightly with Aero-Shell 17 black grease.

Apply greasegun to all main and nose-gear grease fittings, using Mobil 28. Remember that there's one on the nose gear that requires removal of the nosegear door.

Use your finger to slather a little Mobil 28 grease on all other appropriate landing-gear and gear-door pivot points. Use Tri-Flow on small, light-duty rod-end bearings.

Oil all control-cable and control-system pivots, bushings and pulleys inside the airplane with Tri-Flow. While you're at it, rotate each phenolic pulley 90 degrees, just in case the pulley hasn't been rotating and has taken a set with the control cable sliding back and forth across it, creating a flat rub point.

Check both fuel tanks for leaks, particularly around the bottom seams and welds. Pinhole leaks will be made obvious by blue fuel-dye stains and can be patched externally, after being carefully cleaned with denatured alcohol, using a two-part fuel-tank sealant compound that you should be able to buy for about $20 from any friendly maintenance shop, for mechanics use it frequently.

Lubricate the flap-motor pivots (Tri-Flow), actuator jackscrew (Aero-Shell 7) and flap torque-tube pivots (Tri-Flow).

Replace the ELT battery if its two years are up. Again, it might be your choice to replace it slightly prematurely-or, if you're not big on regulations, to let it go till the next annual-if it's a matter of doing that versus opening up the tailcone again several months later. Check the ELT for proper operation.

Put it all back together.

Do the required runup, leak check and idle-mixture check if you haven't done it already.

Put the following certification in your logbook, date and sign it and you're done: "I certify that this aircraft has been inspected in accordance with the requirements of an annual inspection and was determined to be in airworthy condition."

Wasn't that fun?

From "Construction Notes" Falco Builders Letter, March 1995

Steve Wilkinson sent this report: "It occurs to me that one very important item I forgot to include in my March 1993 Builder Letter summary of how to annual your Falco was the need to grease the prop. Any builder who uses my checklist-silly fool-should add the following paragraph:

"Remove the spinner and grease the propeller hub bearings. This should be done at least at every annual. The most important thing about the procedure is to remove the second grease fitting on the opposite side of the hub from the one to which you're applying the greasegun. If you don't do this, there's nowhere for the grease you're displacing with clean grease to go, and you'll blow out the prop seal. Grease should come out of that threaded hole pretty quickly, say after a stroke or three. If it doesn't, stop greasing: there's something wrong, and you may blow the seal anyway. If grease is coming out the hole freely, examine it; what you want to do is push out the dirty grease and any corrosion-causing water that might have found its way into the prop. If there's substantial water, that's another sign of a problem. Replace the removed Zirk fitting, check the prop for signs of missing static-balance fittings, and replace the spinner."

From "Construction Notes" Falco Builders Letter, June 1995

Stelio Wilkinson faxes, "If anybody out there is scrupulously following my how-to-do-an-annual summary-poor fools-here is one more item that I have discovered properly should be done at an annual. I understand that this ultimately is discretionary, but Bendix recommends that at least every 100 hours, the fuel strainer in the Bendix RSA fuel-injection body be removed, washed in solvent (MEK, typically), blow-dried and replaced. I assume that virtually all of us have fuel-injected engines with Bendix fuel servos mounted. The fuel screen is accessed on the side of the RSA opposite from the throttle linkage, down low, next to the pivot point of the mixture linkage.

September 2003

I was thinking about the accident with N33LW last night, and I thought I would mention to you that you may want to add to the check lists that or on the website for annual inspection "Inspect the intake filter and frame for cleanliness and integrity." There could be some more planes out there with filter frame problems. -- Glyn Russell

Thanks, also since the accident was apparently caused by the collapse of the internal spring structure of the engine air intake duct, we are also adding "Inspect internal spring structure of engine air intake duct."