Airframe and Powerplant

Manufacturers' service information is a valuable resource for airplane owners

The Book of Great Books condensed Charles Dickens' David Copperfield down to eight pages. A current paperback version of this sentimental English memoir/novel fills 912 pages. Similarly, your airplane owner's manual or pilot's operating handbook is a condensed version of how to take care of your airplane (see " Out of the Pattern: Into the POH," May Pilot), and service information from the manufacturers of the airframe, engine, propeller, and other components is the unabridged version of the same book.

This information includes bulletins, letters, instructions, and advisories. There is service information that saves money, information that clarifies and amplifies procedures, and information that warns owners of critical maintenance issues.

Reading for dollars

I could set up a little bitty office, equip it with a couple of telephone lines, a fax line, and an Internet connection, charge general aviation owners and mechanics $5 per answer to their technical questions, and make a living. Many of those answers that people are willing to pay good money for are printed in manufacturers' service information publications.

Why don't owners have their own set of service bulletins? Part of the answer lies in the sheer number of them. The current catalog of Textron Lycoming service bulletins, service letters, and service instructions is more than five inches thick. Another reason may be cost — owners may think that they're too expensive. Yet are they? Paper versions of service bulletins, letters, and instructions from Textron Lycoming can be purchased for $100. If four or five owners band together for a subscription, the cost is less than a tank of gas for your car. Owners may think that the detailed information in service bulletins is too technical or that this information is aimed solely at maintenance technicians. Even if four out of five pages are not pertinent to the ave.age airplane owner, it's a good bager that there will be some information in the remaining pages that will make the purchase worthwhile. Think of printed service information as a highly qualified second opinion.

There's information for almost every situation. For example, suppose your airplane is damaged when a gas truck backs into the wing, and it's going to take four months to fix the damage. On a brighter note, perhaps you decide that it's time to stop flying for the summer so you can pursue your lifelong dream of hiking the Pacific Crest or Appalachian trails. Either way, your airplane is going to be out of service for a while. The most common cause of corrosion (rust) in our airplane engines is inactivity. Steps must be taken to protect the cylinder walls, camshaft, lifters, and crankshaft from corrosion. What's the procedure? Your local A&P will be able to give you some pointers. For step-by-step detailed information go directly to Lycoming service letter L180A titled Engine Preservation for Active or Stored Aircraft or Teledyne Continental's service information letter SIL99-1 with the same title. There's a $5 answer.

Operating clues

Many of the operating manuals for our airplanes are marginal at best. Engine operating instructions in some owner's manuals are very simplistic. Here's what one book says: "Primer — as required; Ignition switch — Start. Hold until engine starts but not longer than 30 seconds; Ignition switch — release to Both (immediately after engine start)." These crisp instructions are just about it. The slender thread of information contained in these books doesn't really help an owner make informed decisions about how to operate his engine or care for his airplane. Perhaps the theory was that owners don't need to know all that technical stuff. But today's airplane owners are likely to be interested in everything about their airplanes.

Lycoming information, in addition to being reasonably priced, has a lot of hints that owners can learn from.

Lycoming service letter L109 (March 12, 1959) applies to airplanes with Bendix-Stromberg PS-5 and PS-7 pressure carburetors. Beech Bonanzas with TCM E-185 and E-225 engines are equipped with these fuel-metering devices. This bulletin tells pilots, after shutting down their engines, to shut off the main fuel valve and move the mixture control from idle cut-off to a position that corresponds to one-third to one-half travel.

This bulletin then notes "higher fuel consumption for three or four hours duration can be expected if the mixture control is left in the full rich position." That's a pretty good hint.

Pilots who live in the wintery parts of the country should take steps to ensure that their fuel systems are as water-free as possible. Lycoming service letter N172B (January 25, 1980) notifies owners that Textron Lycoming has determined that adding Prist to the fuel is a safe way to make sure that fuel-borne water won't freeze. The bulletin warns that Prist will not work well if it's dumped into a full fuel tank — it must be mixed with the fuel when pumping the fuel into the tank.

Owners who change their own spin-on-type oil filters can avoid the hassle of trying to remove filters that have stuck to the mounting pad by using the gasket lubricant specified in Lycoming service letter L183 (January 2, 1976). This is a reprint of a Champion technical bulletin that specifies using Dow Corning DC-4 compound on the gasket instead of engine oil.

Spark plug fouling

As long as there's tetraethyl lead (TEL) in avgas, the possibility of spark plug fouling exists. Ethylene di-bromide is added to avgas to scavenge the lead from the pistons, valve stems, and combustion chambers. At temperatures over 900 degrees Fahrenheit, the ethylene di-bromide combines with the lead to form lead bromide, which is flushed out of the cylinders as a gas during engine operation.

Lycoming service letter L192B (January 19,1988) tells about the cause of plug fouling: "Low operating temperatures coupled with rich mixtures prevent the complete vaporization of the TEL." The remedies suggested in this bulletin are to set the correct idle speed and mixture, operate the engine at 1,000 to 1,200 rpm after starting and during initial warmup, use normal leaning techniques, keep the cylinder head temperatures in the normal operating range, and keep deposits from building up during engine shutdown by running the rpm to 1,800 for 15 to 20 seconds before reducing power to 1,200 rpm and immediately pulling the mixture control.

Valve sticking

When there are a number of bulletins or letters from a manufacturer about the same problem, this is a big clue to operators.

Lycoming engine exhaust valves are cooled by transferring the heat up the valve stem to the valve guide area. Since this results in high temperatures in the valve stem/valve guide area, the possibility exists for reduced clearances between the valve stem and guide because of residue buildups from overheated oil (coking) or lead fouling. Reduced clearances in this area can result in valve sticking. Lycoming service instruction 1425A (January 19, 1988), Lycoming service bulletin 301B (February 18, 1977), and Lycoming service bulletin 388B (May 12, 1992) provide guidance for maintenance shops and pilots on this issue.

TBO time

Do you want to know what the time between overhauls (TBO) is for your engine? You have to go to the engine manufacturer's information. Can a TBO be extended or reduced by the manufacturer? Yes, and the change will be announced in a service letter. Service letter L213A (April 10, 1987) notifies owners of certain Lycoming O-235 series engines that the TBO of their engines can be increased by 400 hours — to 2,400 hours — after a higher- strength piston is installed in all four cylinders.

In 1977 the FAA issued airworthiness directive 77-13-03 on Teledyne Continental 100-horsepower O-200 engines. The AD was written to prevent cylinder head cracking and was co-issued with TCM service bulletin M77-12. The AD and bulletin said the same thing — retard the ignition (magneto) spark timing from 28 degrees of crankshaft rotation before the piston gets to top dead center (BTDC) on the compression stroke by 4 degrees. The new 24 degrees BTDC timing caused the pressure buildup from the expansion of the burning fuel-air mixture within the cylinders to be delayed until after the piston had moved beyond top dead center. To understand the effect of this slight delay in the ignition spark, imagine someone riding a bicycle. There's much less stress on a rider's knee and ankle if the pedal is pushed down after the pedal arm has moved past a vertical position.

Are service bulletins mandatory?

The TCM O-200 example above illustrates why some service bulletins are matched by AD notes. Service bulletins are not mandatory by law. It's prudent and wise to pay close attention to service bulletins that have a red border and are titled Mandatory, but private owners (who don't hire out their airplanes) are not required to comply with service bulletins unless mandated by an AD. The O-200 timing change bulletin is one that the manufacturer considered important enough to require compliance, hence the AD.

For all the O-200 owners out there, the AD and service bulletin referred to above have been superseded by AD 96-12-06 and mandatory service bulletin MSB94-8A (September 14, 1994). O-200 owners can restore the ignition timing to 28 degrees after installing a complete set of higher-strength cylinders (part numbers higher than 641917).

Money savers

Occasionally a bulletin can really save an owner some money. Cessna service bulletin 65-89 turned out to be a big money saver for owners of single-engine Cessnas built prior to 1966.

Contactors (sometimes incorrectly referred to as solenoids) are designed to connect the starter to the aircraft battery when the pilot turns the key for engine start. Starting aircraft engines requires a large amount of electrical power and these contactors are very durable, but they must be replaced when they start to stick or fail to close. The service bulletin let owners of these airplanes know that the original contactors could be replaced by newer-design, less expensive contactors, and gave them the new part numbers. In this instance, the service bulletin not only took the place of a parts book change, it is used as FAA-approved data for the change. In 1997 the difference in cost between the two contactors was $337. I told you there was money to be made by reading service bulletins.

Airworthiness directives

I've mentioned this before, but it bears repeating. The form and content of airworthiness directives have changed over the past 50 years. Some ADs don't have one word of accomplishment instruction information contained in the body of the text. In other words, all the AD does is tell the owner or maintenance facility to go to a service bulletin and comply with the bulletin's accomplishment instructions. One example would be Cessna AD 69-08-11, which applies to pre-1969 205s, 206s, 210s, and T210s. The text says, "To prevent complete loss of engine power when using the fuel boost pump, accomplish the following: Modify the fuel boost pump electrical circuit by installing a resistor in accordance with Cessna service letter 69-9, dated April 11, 1969." ThiU AD is impossible to accomplish without the bulletin. Visit AOPA Online ( www.aopa.org/members/files/airdirect/idxad.html) and read through the wording of various ADs to get examples of this.

Fortunately, this practice of issuing ADs with zero helpful information was short-lived and very limited. Today's ADs are informative and written in the FAA's plain-language format.

Make your own service bulletin file

Some manufacturers should be praised for making their service information very easy to obtain. Others act as if sharing service information is akin to giving away money. One of the blessings of living in the twenty-first century is the amazing amount of information that is available online. A few general aviation manufacturers provide online access to their service information libraries at no charge.

Teledyne Continental Motors leads the pack with its Web site ( www.tcmlink.com). A quick sign-in at the aviator services network is all it takes to gain free access to TCM's engine and electrical system (the company bought the Bendix line of ignition systems in 1989) service information. If paper copies of the bulletins are desired, the cost is $100 for the initial subscription, which includes updates for the remainder of the year. Renewal services cost $50. The ignition bulletins cost $10.

An index of all Textron Lycoming service information (bulletins, letters, and instructions) is similarly available online ( www.lycoming.textron.com/main.html). An initial subscription to paper copies of Lycoming's information is available for $125 plus $15 for shipping and handling. Renewals are $50 a year.

Lycoming and TCM are leaders in making service information available to aircraft owners. Owners who have a good relationship with their maintenance facility may be given permission to use the facility's service information library to create a list and build a library of information applicable to their airplane.

Many airplane type clubs (see " Airframe and Powerplant: The Techno-Fun Connection," June 2001 Pilot) also keep comprehensive service information libraries. A listing of type clubs is available on AOPA Online ( www.aopa.org/members/databases/).

Manufacturers' service information helps owners keep up with factory improvements, learn more about helpful operating techniques, and save money on the operation and maintenance of their airplanes.

E-mail the author at [email protected].