Yes, this is another aging aircraft article but don’t quit reading yet because this one is just a bit different. We (CPA, FAA, etc.) have been preaching for years about the perils of ignoring the problems that come with owning and operating an airplane that is forty years old. The topics often focus on corrosion, worn out parts and other similar items related to flight time or just aging in the weather. There is another issue that comes with aging aircraft which we don’t usually consider. Your thirty, forty, fifty plus year old Cessna is the sum total of a lifetime of maintenance, both good and bad.
According to the FAA, you the owner-operator, are responsible to ensure the airplane maintenance is properly performed (FAR 91.403). They also require that you get the plane to its scheduled inspections and get repairs performed between scheduled events (FAR 91.405). The FAA also requires that the plane be maintained using methods, techniques, and practices prescribed by in the manufacturer’s maintenance manuals and acceptable industry standards as acceptable to the Administrator (FAR 43.13).
The first thought taken away from these regulations is to note that the manufacturer’s service manual must be available and used during any repair work. The second thought is that if everyone uses the same manuals then all the planes should be maintained in the same manner using the same approved parts. This would also imply that regardless of the age, the plane will always have the proper parts installed using the proper methods. Unfortunately, this often isn’t the case.
The 150 Inspection
This 150 arrived at our shop and the owner informed us the plane was in excellent condition and the ensuing annual will surely be a mere formality. He had just purchased the plane and was assured by the seller that the plane would need only minimal maintenance; after all, it’s “just a 150”.
At the beginning of the fourteen hour inspection it became obvious that this poor airplane had endured many years of improper maintenance and neglect. Much of what we found was a result of maintenance performed with little regard to the factory service manuals, industry standards, or even basic safety in some areas. The following findings support this observation:
Control cable tension checks should be performed at every annual. When adjustments are needed they must be done correctly to maintain proper rigging of the flight controls. In many controls systems there is one turnbuckle that is easier to get to than the rest and will be the one that always gets adjusted. After a few annual adjustments, this results in a system that is out of rig. It happens gradually over a series of adjustments so the change may not be realized. Proper cable tensioning must be followed by a check of the control rig and probably adjustment of at least one other turnbuckle.
FAA Type Certificate Data Sheets are FAA documents that give certain specifications for the plane as it was originally designed. The airplane must be compared to this standard to ensure it still conforms to that original design. If it differs from this standard, there must be some Supplemental Type Certificate that gives FAA approval for the variation. This helps determine if that propeller the last owner found on E-Bay is airworthy for installation on that specific plane.
Placards age whether you read them or not, Just having one missing or faded to the point of unread ability renders the airplane airworthy.
Every airplane has two distinct personalities; the aluminum one and the paper one. It is very important that they match. Many years of removing this radio, adding another then taking it out, installing skis then removing them, etc. may leave the paper airplane in shambles. If a 337 was used to install an item, it is expected that another 337 is required to show its removal. You should be able to find a continuous paper trail of all additions and removals.
New customers bring their planes to our shop knowing it has no damage history. Apparently, our definition of damage history differs from theirs. It’s rare to find a forty year old plane with no damage history, but it’s very common to find no record of any major repairs. Any major repair found on the plane must have a corresponding FAA form 337 filed with the FAA. If the documents can’t be found in the aircraft records then they may be recovered from the FAA archives.
A good test to perform at annual, on a plane with a fixed pitch propeller, is a max power static rpm check. After making the proper adjustments for density altitude, the static RPM check gives a good indication of engine and propeller performance. If the engine is capable of making higher than the maximum RPM limit, one would certainly suspect the propeller. One probable cause is a propeller that’s been shortened below the minimum diameter or is simply the wrong propeller.
The gascolator is the last line of defense for water contamination. It should be drained prior to each flight, but that may not be often enough if the plane sits for prolonged periods. The gascolator drain is difficult to get to with a sample cut while pulling the drain valve cable, so the fuel usually just ends up on the ground with no real determination if there were any contaminants. There is a fuel filter screen in the gascolator that is required to be inspected at every annual. Unfortunately, many mechanics just drain it and assume all is well inside. The fact is that many of the gascolator bowls corrode severely because water sits in them for very long periods without being cleaned. When that corrosion finally makes it all the way through the bowl, a lot of fuel can escape in a short period of time.
Induction air filters are not usually given much attention except to change them from time to time. In fact, there is an FAA Airworthiness Directive that requires replacement of paper air filters every 500 hours. Paper filters are pricey, so many have been replaced with various aftermarket filters. There has been ADs issued against some of those as well. The air filter is the primary prevention against debris in the engine. There’s no good reason to allow something so inexpensive to cause so much damage to your cylinders.
There are few options when it comes to batteries for our planes and they are a vital part of reliable operation. Some battery models don’t quite fit the original battery boxes, so the battery manufacturer has devised approved ways to alter the battery in the field as needed. Leaving the lid off the battery is not a proper solution. A battery free to flail around the engine compartment is a high current disaster waiting to happen. It wouldn’t take but a few seconds of the battery positive terminal making contact with the engine mount to melt away precious structure. The battery is your standby electrical system but will only be ready to help if it’s in good condition.
The alternator is the primary electrical supply for your plane and should be cared for appropriately. During heavy loads this component can generate a good bit of heat as well as electricity. The air blast tube is one of its sources for cooling, so it’s critical that the tube not only be in the plane but be kept clear of restrictions.
Most alternators have some sort of fan blades attached to their shaft for cooling air movement as well. If it spins freely when touched during static inspection, there is a problem, but one wouldn’t find this by just looking at it. Hands-on inspection is required.
There are few flexible hoses on the 150, but they are critical. Everyone should understand the importance of changing these hoses every eight to ten years. It’s also important to change them with the correct hose material. An instrument air hose may look a lot like low pressure fuel hose, but that’s where the similarity ends. A review of the parts manual and knowledge of FAA AC 43.13-1A is a must. One might save a few bucks installing the wrong material hose, but that’ll seem a pretty foolish decision when the hose deteriorates from the inside out.
It’s becoming almost routine to find most, if not all, of the pilot’s instrument panel shock mounts failed on our old Cessnas. These little items ensure the old instruments are protected against the harsh vibrations of the engine. They also prevent the instruments from sitting on top of the flight control system behind the panel. It’s a very unsettling sensation when the control wheel won’t pull back on command because it’s hit the back side of a gyro.
When inspecting tires, it’s not just the amount of tread remaining that helps prevent a blowout. Those sidewalls are also a primary structural part of the tire. If the side walls are cracked all around from dry rot, they’re going to have a much more difficult time holding together when you apply heavy side loads on that next crosswind landing.
The extra collar around the pilot control yoke allows for installation of a control lock. If control locks are not used during aircraft storage, there can be significant damage to the system that won’t show during a pre-flight but might become abundantly obvious in flight.
The forward spinner bulkhead is nylon and will lose its ability to hold the spinner tightly in place over time. Lack of attention allows the spinner to wobble, which stresses the spinner and the aft bulkhead causing cracks. Eventually, the spinner will want to depart the plane.
The compass has seals that shrink as they age, allowing the fluid to leak out. This often happens while you’re not around, and a full compass looks a lot like an empty compass. A compass is an instrument, and must be repaired by a properly rated instrument repair station. Reworking the compass in the field with one of those neat compass repair kits is not legal.
The elevator trim cables make a small radius 90 degree turn inside the horizontal stabilizer just under the vertical fine. The two pulleys and the cables are often neglected and consequently rust. These should get some special attention at annual with appropriate lubrication.
There are several FAA Airworthiness Directives against different ignition switches. The recurring action called for by each AD depends on the specific make and model of the switch. It doesn’t quite accomplish the desired effect to repeatedly perform the required checks if they don’t apply to the switch in hand.
Conclusions
We don’t usually see these kinds of problems on the restart Cessna series as they are newer and the owners have more investment at stake. The purchase price for a legacy Cessna is far less than the restart planes, but the cost to maintain either is the same. The higher relative cost of maintenance to purchase price is a significant contributor to the likelihood of finding these legacy planes being maintained “on the cheap.”
Another contributor to this issue is the growing lack of mechanics that were around when these planes were new. It’s often difficult to tell how some assemblies were originally installed just by viewing the service and parts manuals. The old guy that worked on these planes when they were still coming off the assembly line has knowledge that’s just very difficult to come by for the younger generation of mechanics.
The FAA mandated annual inspection is designed to help keep our planes flying safely. That inspection includes verification that the airplane meets its type design and is in a safe condition for flight. Installing unapproved parts, leaving parts off, ignoring obviously worn parts, not ensuring the plane meets the original specifications (or as altered per properly installed STC) is simply unacceptable. When any aspect of this criteria is ignored, the pilot and his/her passengers become test pilots – don’t be an unexpected test pilot. Take control of your Cessna’s maintenance and be certain all is done safely. Hopefully, the fact that you’re reading this magazine and a member of the Cessna Pilots Association says that I am preaching to the choir.
Copyright © Paul New 2012. All rights reserved.
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