Six years ago, in an article titled Designed for Maintenance?, we looked at the typical modern GA airframe strictly through the mechanics eye. Our idea was to highlight ways to spark a new age in light airplane development by focusing on things that would make an airframe easier to maintain and thus cheaper to own.
We found that inadequate design features added a lot to the cost of owning an airplane and we imagined that ease of maintenance would do as much to bring down the cost of flying as would new fuels and engines and slick new airplane designs, which, frankly, are only now beginning to come off the drawing boards and onto the ramp.
Its time for another look. GA is indeed on the upswing but have the manufacturers listened to the blood curdling wails emanating from maintenance hangars across the land or have they given us more of the same?
Whats this? It appears that the product liability fiasco has been beaten back enough to allow our dream to once again emerge: The industry is cranking out new aircraft at a good clip. New designs are being certified, old ones resurrected and production facilities being built to assemble them.
How are the manufacturers doing on the issue of maintainability? Can we operate these new beauties with less money than their mid-1980s counterparts? Have lessons been learned?
Yes and no. Our informal review of some new models suggests that there have been some improvements but also some boneheaded repeats of the same old maintenance nightmares.
The Cessna 172 is considered by many to be the stalwart of the U.S. training fleet and possibly the world, with the 182 close behind as a favorite step-up airplane. These models were neither the best nor the worst with maintenance in mind but has Cessna improved things, given a second chance?
We examined three brand new 172s opened up for annuals in nearby shops and talked to the mechanics working on them. Two new 182s were also in for inspections and other work. With the only significant difference between the two being a couple of extra cylinders and a constant speed prop, well lump the two together for this analysis.
In the engine compartment, the first thing that jumps out at you is the automotive look of many components. The alternator has microgroove belts and pulleys. It looks just like the serpentine belts on newer cars, except its a lot shorter.
Since the engine is a Lycoming-nope, they didnt change the remove-prop-to-change-the-alternator trick-lets hope the new belts last longer than the old V-belts did, allowing for fewer prop R and Rs.
The airplanes we examined had accumulated only 350 hours so jurys still out. A side note on current reliability of alternators, if youll pardon the pun: All four 172s were on their second alternator and one was on its second starter, all of which are lightweight models. Still some bugs to work out here, it would appear.
The wiring harnesses in the engine compartment are routed in automotive-type ribbed plastic anti-chaff conduit. Suspicion has it that these will get messy and oily at about the same time the engine develops some oil seeps, a certainty as they accumulate more hours. We imagine many owners will then remove them.
The engine induction air filter in the new Cessnas was originally of the flat automotive type, which makes us wonder if the engineers popped open the hoods of their cars and took notes.
These were actually Fram filters with the automotive part number even listed in the parts book. Only $15, it should have been great, right?The mechanics we talked to said the first flight into significant rain just trashes the thing. This has been addressed by a Cessna service bulletin specifying a Donaldson paper filter costing $120. We knew it was too good to be true but nice try Cessna.
If you dont like or have trouble with electrical work, these arent your airplanes. All engine indicating systems, with the exception of the tachometer, are electric. The plug and socket connectors at the transducers are the same self-sealing type found in most cars.
On the top left hand side of the firewall sits an unfamiliar looking box with a big LAMAR molded into the cover. This box houses the alternator control unit-regulation, high volt trip and out indication, all in one unit-the battery contactor, starter and ground power contactors, plus all the fuses, all in one neat package.
It did take us 15 minutes to get the cover off, since the engine mount is right in the way. (Did these guys study at the Mooney factory?) Hold your tongue right, make the appropriate twists and turns and it will come off. Apart from the cranky cover, this centralized location for the electrics is a good idea in our view, and ought to save troubleshooting grief. Score one for owners.
The air filter plenum and induction elbow to the fuel servo appear to be made of the same material as the cabin heat valve bodies in the old normally aspirated 182/207/210 series. These were notorious for collapsing when the clamp is torqued to anything more than snug. An aluminum reinforcement ring on the inside diameter of the hose connection point was usually required to repair the valve. Im sure these new induction parts will fall prey to the same problems and require replacement or repair. Its somewhat worrisome because loose parts in the induction system arent a good thing and have led to engine stoppage or damage.
The muffler system has changed much and two of three 172s were on their third muffler, the second since a very recent AD. And theyre still cracking. More bugs to chase.
As youve read in the pilot reports on the new Cessnas, the wings are now wet and each one has five, count em, five quick drains. With the belly and strainer drains, thats at least a dozen leak-prone drains on one airplane with only one engine and four seats.
Were all familiar with the annoyance of leaky sump drains and thats with only one in each wing. Give these babies a little time and youre in for a half-hour preflight just trying to stop them from dripping fuel all over the politically correct environment. Did I hear someone say EPA? Cessnas answer: Theyre easy to replace. ($$)
We hope theyve at least solved the trapped-water-in-the-tank problem of the older models and we didnt see any of the shake-the-wings-drain-the-fuel-or-die placards of yore. While fear of liability may be diminished, it hasnt become extinct.
These niggles notwithstanding, mechanics tell us there have been many improvements and some would say these are long overdue.
The engine fuel strainer, for example, has a different bowl but the techs tell us its basically the same as the old style. However, the drain is no longer the troublesome remote cable type but a spring-loaded job you simply jab your fuel tester into. Bravo. Access to the rear of the engines is still relatively easy and all of the components can be easily removed without having to detach something else to get at the broken part. The cowl fasteners are still the rubber mount camlocs but are now one or two sizes larger than the old ones, making them durable and more robust. This will pay off 20 or 30 cowl removals down the road.
On the older airframes, mechanics extolled the virtues of landing lights in the wing instead of the cowl. Cessna listened. Theyre back in the left wing, just outboard of the strut. Bravo again.
Replacement would be easier if the lens cover were held on with quick fasteners but we dont hear much complaining. Also, replacement will come less frequently now that the lamps are isolated from engine vibes.
One maintenance director we interviewed told us Cessna traveled the country soliciting customer input a year before production started. This seems to have done some good, especially in most areas of the airframe.
The interior cabin trim is made of a more structurally sound compressed foam and is much easier to remove and install. Insulation inside the airframe is fiberglass but is treated with resin to make it fluff resistant, thus the fibers stay in place. We hope this hair spray treatment holds up better than the old insulation did. (Not saying much, we know.)
The overhead lights and air vents can be quickly accessed in less than 10 minutes and are themselves easy to fix. Remove a few number 10 screws and the entire center light/vent panel just drops down. The instrument panel is now sectioned into five or six removable panels, allowing much easier access for instrument R and R.
A number of lightening holes have also been enlarged for easier access, including a large removable panel near the auxiliary fuel pump underneath the co-pilots knees. (Remember, both the 172 and 182 have injected engines now, so they have pumps and plumbing where none existed before.)
An interesting gotcha here, though. The fuel shutoff valve is located on the firewall, downstream of the auxiliary pump, making draining at least one of the fuel tanks necessary-and probably both-if you have to yank the pump for any reason. We found one wish come true: The seat rails are a different design and heavier duty than the old type, negating that awful seat rail AD. Each rail is attached with eight bolts-with nut plates on the other side-requiring no more than 20 minutes to change the part, if needed.
Whyd They Stop?
Obviously, Cessna got on a roll but they missed some stuff, too. The dimmer transistor and head sink assembly for the panel lights is still high under the panel. Access may be easier by removing one of these neat new instrument panel sections rather then wrenching your back lying on the floor.
And the vacuum regulator filter? You know, B3-5-1s? Thats still up high on the back side of the firewall and snugged tight up against it. Hello? Changing this every 100 hours or at annual, as recommended, will keep our chiropractic friends in business for a long time to come.
Wouldnt it have been just as easy to place it lower? How about an access panel behind the windshield? One last thing we noticed on the new Cessnas is the plastic composite rudder pedals. They look like theyre made of some sort of polymide. It remains to be seen how long theyll last with excited instructors and students stomping on them.
Not to single out Cessna, we also took a mechanics eye view of the Diamond Katana, a clean-sheet airframe enjoying some success as an entry-level trainer. The engine on the A1 version of this airplane is a dual-carbureted Rotax design, while the newer C1 has a TCM IO-240B.
The technicians we talked to didnt like the balancing that occasionally has to be done on the Rotax carbs. Dust off your motorcycle and road racing maintenance skills for this one. Other engine maintenance items on the A1 are about as easy as a 152 or Cherokee 140, so not too bad there.
The C1 has some minor changes in the airframe to accommodate the newer engine but is otherwise the same basic airframe as the A1. Diamond made their own oil filter adapter for the C1 that angles the filter out to the left, making it a breeze to change and not much of a mess either.
It was such a good idea, scuttlebutt has it that TCM might even buy it. Access to the rear of the engine is simple. Any component can be removed without having to remove another.
The C1 has English standard wheels, tires and brakes, making parts availability a non-issue as opposed to the A1, which has metric tires and wheels. Tire changes and wheel bearing lubes are easy because the wheel pants are easy to remove, some say easier than the Cessnas.
Accessibility to all components is relatively easy on both models. The rear of the instrument panel, for instance, is accessed by opening the canopy/windshield (hinged in front) and removing the screws which hold on the glareshield. You can then stand in front of the wing and remove instruments to your hearts content. Wonderful!
The wing has one inspection panel in it, on the bottom, for the aileron bell crank. Its removable but is also made of clear plastic if only an inspection is required. The technicians we talked to said that 100-hour inspections were mostly a breeze.
As with all new designs a glitch or two has shown up. The early model nosewheel fork on the C1 was too weak for the heavier TCM engine and cracked or broke on occasion. This was fixed by the manufacturer who gets high marks for tech support. Customer input is encouraged and some changes have come quickly because of that.
Input or not, the C1 turned out not to be the airplane for the University of North Dakota, a major collegiate flight operation that recently sent its fleet of C1s back to Diamond. UND found the C1s unsuitable for the daily grind of flight training, due to fuel problems and, especially, shrinkage of the wooden prop. Diamond is working on fixes for those problems.
Diamond has a lot riding on the C1, since the Rotax version of the airplane is no longer being offering. The airplane was tested with a metal prop and, presumably, that will be an option.
Other minor notes on the C1: The airframe hardware is metric standard and the engine is English standard. That creates some interesting maintainability problems where the engine meets the airframe. Mostly hardware mix-ups but not a huge problem, so the techs say.
Neither a plus nor minus so far is the wooden propeller. Theyre painted but some operators might have to pull some old books off the shelves to bone up on wood prop care and maintenance. The air filter is paper and therefore subject to AD84-26-02 but at 500-hour intervals, this shouldnt pose much of a problem.
Airframe repairs are simple enough if you have a little composite experience or training. Send a picture or good drawing of the damaged area to the manufacturer in London, Ontario and the engineers will draw out a repair procedure.
The kit to perform the procedure is sent complete with instructions and all materials required, even the gloves. The only drawback here is the cure times put the airplane out of commission for at least a day or so.
Composites are more sophisticated than they used to be so it doesnt quite feel like gluing the airplane back together and its somewhat cost effective. However, if the repairs dont work out, a new component is the only solution.
So, are we ahead of the game here? Yes, it would appear so. Although the real maintenance headaches often dont show up until an airframe has accumulated 1000 hours and five years or so.
The overall opinion on the Katana was a resounding well done while Cessna gets credit for definite improvements tempered by a few oversights. With any luck, theyll keep listening and next years models will be improved.
-by Tom Ehresman
Tom Ehresman is an A&P and experienced test pilot for a major engine shop.