Airframe and Powerplant

That First Annual

September 1, 2004

Doing the checks, writing the checks

The prepurchase survey mechanic said that the airplane was airworthy so AOPA members John and Jane signed the papers and bought their first airplane. They flew it for three months before they scheduled its first annual. J & J had noticed that pushing the starter button didn't always cause the prop to flip over with vigor, but once it started the engine ran strong. The climb performance, airspeeds, and fuel consumption numbers were in line with the pilot's operating handbook figures. The airplane did, however, use a quart of oil every three hours.

The landing gear went up and down, the airplane flew straight and level, and it was a lot of fun to fly. Except for the cost of gas and the higher- than-expected appetite for oil, an expense item J & J have learned to call a direct operating cost, the airplane has not cost an additional dime.

The avionics suite wasn't really a suite at all — it was more like a closet with one good Bendix/King digital nav/com and matching VOR head, a Bendix/King audio panel, and a Bendix/King transponder with altitude encoding. J & J were saving for more avionics but right now they owned under FAA flight-plan-filing parlance a "slash uniform" airplane. The "closet" has almost been trouble free — but there had been more than one time when an air traffic control facility had told J & J that the transponder secondary signal had been lost. Fortunately this had only happened when ATC was providing flight following services in VFR conditions.

The first airworthiness directive

J & J found the owners group through a link on AOPA Online, asked for maintenance advice, and found more than one member who recommended a mechanic in the next city.

J & J called the mechanic, asked if he was willing to take on the first annual, and when he said yes, they asked him if he would mind if they helped. He said that would be fine. He told them to show up early Monday with minimum fuel in the tanks. When J & J asked why, he said that there was a recurring airworthiness directive (AD) calling for inspection of the fuel bladders. So begins the education of two new airplane owners.

Day one

After spending the weekend flying around to burn off gas, J & J arrive at the airport at 8:30 a.m. Monday. Jim, the owner of the shop, thanks J & J for arriving on time and with minimum fuel, and asks them to sign a work order. He introduces them to Joe, who conducts the annual. With a clipboard, a checklist form, and squawk sheets, Joe asks a few questions. "Did you bring the logbooks and all other airplane records?" "Have you noticed anything wrong with the airplane?" "Do you fly the airplane in instrument conditions?" When he gets a no answer, Joe asks for the date of the last transponder check. J & J answer that they don't know and he makes a note on the squawk sheet.

The runup

Then Joe hooks a voltmeter to the main electrical bus, grabs his tachometer checker, and his clipboard, and asks if J & J want to come along for the runup.

At the run-up pad, Joe faces the airplane into the wind; checks to make sure his prop blast won't cause any grief; and works through the checklist. He records the rpm drop-off during the mag check, he checks propeller governor operation, and he checks the electrical system for regulated voltage and turns on the landing lights to load the charging system. He checks the operation of the carburetor temperature gauge and the carburetor heat system, the vacuum system gauge, and uses his portable tachometer checker to check the propeller rpm in the cruise rpm range. It turns out that the tachometer is 75 rpm low. He explains that this is typical for mechanical tachometers and that he will placard the tachometer so J & J can convert gauge rpm to actual rpm.

Joe then runs the rpm up to full throttle and checks the rpm. He asks John to check that the airplane doesn't start rolling. He does a mag check at cruise rpm. He explains that this is a "stress" test for magnetos, ignition leads, and spark plugs. He then eases the throttle all the way back and checks the idle rpm. He then turns the ignition key counterclockwise past the L and past the R to the Off position momentarily before returning it to Both. He again explains that there's a recurring AD note on Teledyne Bendix ignition switches that requires this test every 100 hours. If the engine continues to run with the switch in the off position the switch assembly must be replaced.

Just before engine shutdown he slowly pulls the idle mixture back — he explains that he's checking the idle mixture and that a properly adjusted idle mixture should cause a slight rpm rise (25 is ideal) before the engine stops.

The engine inspection

Joe asks if J & J want an oil analysis. He explains that the cost is relatively low — about $15 per every oil change — and that a series of regular analyses may help diagnose engine problems in the future, but that for this tool to be of value, samples must be taken often enough to establish a baseline of wear metals relative to engine hours of operation.

J & J agree to start an oil analysis program.

The rest of the morning passes quickly as Joe shows J & J which inspection panels to remove, and suggests that putting the screws from each panel in a cheap plastic bag will help when it's time to reinstall the panels. Joe does a compression test while the engine is at operating temperature (see " Airframe & Powerplant: The Pressure's On," June 2000 Pilot), removes the oil filter and cuts it open, removes the engine suction screen, and the carburetor finger screen. Happily, there isn't any contamination in the filters or screens, and the compression test shows that the rings and valves are sealing well.

What about the oil consumption?

J & J had asked Joe about the oil consumption. "Is it normal for airplane engines to use a lot of oil?" they ask. Within an hour Joe is back with an answer. "Your engine logbook shows that this engine is the original engine that was on the airplane when it left the factory in 1960, and that a field overhaul was done about eight years ago," says Joe.

He goes on to explain that the original cylinders were rebuilt at that time. He shows J & J an orange stripe on each of the cylinder barrels that signifies that the cylinder bore has been chrome plated. The process used on these cylinders is called channel chroming. Channel chroming has its pluses and its minuses. The big plus is that it's extremely hard and cylinder bore wear is nonexistent. The big minus is that because chrome is so hard, and the chrome is not oil wettable, the ring-to-cylinder wall break-in process is unpredictable. If the break-in process is not done exactly right there's a good possibility that the rings won't seat in to the cylinder walls. The first few minutes of the first flight after engine installation are critical. There's even the possibility that when the entire process is followed to the letter, the rings may not completely seat. The result is always higher-than-normal oil consumption.

Joe goes on to explain that the oil consumption will probably stay stable for hundreds of hours because it's not caused by increasing wear, but by less-than-ideal oil ring sealing. Short of removing all the cylinders and sending them back to an overhaul facility to have the cylinder walls ground to a ring finish, and then attempting to break in a new set of rings, there's nothing that can be done except to keep on adding oil.

Joe went on to point out that each cylinder had good compression readings, and that a borescope inspection of the cylinder combustion chambers didn't show any unusual wear in the valves, pistons, or cylinder walls. He said that if J & J could live with the oil consumption the engine was healthy.

J & J then asked if there was a limit for oil consumption. Joe pulled down a copy of Lycoming Service Instruction 1427B. It gave this formula for maximum oil consumption for all Lycoming engines expressed in quarts per hour: 0.006 times horsepower times 4 divided by 7.4.

J & J plugged in the numbers for the 180-horsepower O-360-A1A engine and found that the maximum oil consumption for this four-cylinder Lycoming is 0.58 quarts per flight hour. (Teledyne Continental Service Information Directive 97-2 notes that a compression test and a borescope inspection should be conducted whenever oil consumption exceeds one quart every three hours. The TCM formula for maximum oil consumption in pounds per brake horsepower per hour is: 0.006 times percent power divided by 100.)

Pesky placards and AD searches

The next task J & J are given is to check for placards. A complete set of placards is required for the airplane to be airworthy. The required placards and their location are specified in the aircraft type certificate data sheet (TCDS), and/or in the approved pilot's operating handbook if one has been issued. J & J find that the placard on the fuel selector valve is defaced and unreadable. They also find that the baggage compartment placard is missing. New placards are ordered.

J & J had heard about ADs but had no idea there were so many, nor that they applied to so many products. Their "new" 45-year-old airplane turned out to have a load of them (see " Airframe & Powerplant: ADs for the Owner," December 2001 Pilot).

There are 32 airframe ADs, 17 engine ADs, 13 prop ADs, there is an oil line AD, four carburetor ADs, two ignition switch ADs, two altimeter ADs, there is a transponder AD, four fuel pump ADs, there is a cigar lighter AD, there are muffler ADs, there are circuit breaker ADs, there are ADs that need one inspection and there are recurring ADs — some recurring ADs are calendar-based (every annual) and some are hours-based while still others are calendar- and hours-based.

J & J are surprised to learn of an extensive AD on the landing gear that mandates exactly the same dimensional and operational inspections that are called out in the landing-gear section in the airplane service manual. If the instructions for maintenance in the service manual had been followed, there wouldn't have had to be an AD.

Many of the ADs only require a one-time inspection. There are a number of recurring ADs that require ongoing regularly performed maintenance. One thing about owning a 45-year-old airplane is that by now the maintenance Achilles' heels have been found and addressed.

Maximum visual progress

Removing the inspection panels and interior allows Joe to verify AD compliance. J & J ask why he needs to verify the things the previous mechanic had already signed off. Joe cocks his head, raises his eyebrows, and stares intently at first J and then J, apparently looking for clues that they still believe in Santa Claus. Then he shows them the landing-gear motor, which had extended and retracted the gear while on jacks only a few hours hence.

"See that?" he says, pointing at what looks like a magnet near the landing- gear transmission. "That's the motor brake and the contact plate has been worn out for a long time, yet the whole airplane was signed off as airworthy less than 30 flight hours ago. That's an example of why I have to check everything," he says.

Joe goes on to explain that first annuals always take longer than subsequent annuals because each authorized inspector (AI) has to determine, to his satisfaction, that the airplane is airworthy when he inspects it. He continues that once he is satisfied that every AD has been properly addressed, that AD compliance is up to date, and the required compliance action has been correctly completed and noted, then the rate-determining (and time-consuming) part of the first annual is complete.

The one-piece windshield

Joe points out another problem when he tells J & J that there isn't any supplemental type certificate (STC) paperwork for the one-piece windshield that had been installed sometime in the past. "It may be installed perfectly, and it may provide a quantum leap in safety because of improved visibility, but if there isn't any paperwork this airplane is not airworthy," says Joe.

He explains that the only avenue open to J & J is to appeal to the companies that hold STCs to install one-piece windshields and attempt to negotiate a reasonable price for the paperwork. This is less costly than J & J expected, and within a few days the paperwork arrives with the airplane model and serial number across the title page.

The local avionics shop performs a transponder check and explains that the transponder had been intermittent because it wasn't fully seated in the tray.

Finally J & J's "new" airplane is truly airworthy. The first annual cost more than they expected it would. Nevertheless, they feel secure knowing that the weak points and problem areas that others had discovered — sometimes with tragic results — have been thoroughly checked for, repaired, and upgraded as necessary to provide a safe airplane for their flying adventures during the coming year.


E-mail the author at steve.ells@aopa.org.