I ran across a nice-looking, low-time Sundowner. In fact, it has been sitting up for several years (possibly as long as ten; the owner first lost his Medical, and then died). It almost sounds too good to be true, with so few hours on a relatively old plane. Is there anything in this situation that I should be worried about?. Search fields: Pre-buy inspection; pre-purchase inspection
I’m skipping some of the common-knowledge stuff, such as getting a pre-buy inspection and title search. This note focuses on the less-obvious factors related to the lack of flight time on the plane.
The engine will almost certainly require overhaul due to corrosion; this may be true even if it was properly “pickled” for storage, unless it was re-examined and re-pickled at the specified intervals. Both of these are highly unlikely; it is not likely to have been pickled per the manufacturer’s instructions, much less re-pickled. Not only is this aspect expensive, but there may be many more parts within the engine that are found to be completely unserviceable due to corrosion; things like the crank, rods, pushrods, and accessory case gears (and shafts) may all be found pitted, in addition to the normally-expected things like cylinders, cams, lifters, etc.
All the engine accessories (mags, etc.) almost surely have bad seals, corrosion in key places, etc. This includes the carburetor. Virtually every single ball bearing on the plane (wheels, alternator, gyros, whatever) will probably have some degree of pitting from recurring condensation that has formed, sat, (and even occasionally dried out), in the same place, time after time, because nothing has moved.
The exhaust system is probably rusted in places such as welds, even if it was made of stainless steel, and the engine mount itself would need a close inspection. Normally an oil vapor film protects it from most corrosion. The mount cushions would be bad, as would be nearly anything else made of rubber in the plane (not just the engine compartment and brake system hoses). All these parts require regular usage to retain their plasticity and to prevent hose liner cracking. Ten years is even beyond the allowable shelf life of non-Teflon hose tubing, before it is assembled into a hose and placed in service. Once placed in service, the standard materials in hoses, fuel pumps, etc. will not tolerate extended disuse without later disintegration (after having been allowed to dry out or stiffen). This effect can even occur on an engine-driven diaphragm fuel pump that is only a few months old, if it is removed from an engine for something like a top overhaul, and left so that the diaphragms are exposed to air on the bench for a couple of weeks.
Particularly if the plane has been tied down outside, corrosion could also be a major airframe issue. Stationary aircraft develop corrosion in places that are normally drained and dried through in-flight operation. This can happen due to condensation even if the plane is kept hangared. The in-flight combination of aircraft attitude, lowered humidity at altitude, vibration and friction, airflow, and forced drainage all keep an airframe dried out. Hidden corrosion can range from spar caps (hard to see all of them), to a corrosion ring inside the fuel tanks, where it can’t readily be seen in these planes. The vertical stabilizer is often a problem area for this as well, in areas that are very difficult to see in a normal inspection; ditto for the stabilator.
The entire aircraft interior would have to be removed, to check for the near certainty of interior skin corrosion under any insulation and trim panels. The area under the windshield would be a critical corrosion check area, including the radio equipment. The wing tips, stab tips, and removable fairings would all have to come off, to look under them and down into the airframe. The Anti-servo tab wire would need to be checked for corrosion, and polished; or better yet, just a new one lubricated and installed, to reduce the risk of “eating up” the aluminum stab-to-tab hinges. If there are any trim or autopilot servos, they would have to be checked. A coupled aileron servo can’t be very easily checked for “hunting” on the ground. It will probably “hunt” in flight due to a commutator oxide film, even if it passes a left-right check on a roll selector knob.
It is almost a certainty that all the hydraulics will need at least an overhaul, if not replacement (master cylinders, brake hoses, wheel brake cylinders, brake disks and pads). The landing gear cushion biscuits have almost surely all hardened up. The tires and tubes are probably all bad. There is probably corrosion inside the wheel bearings, and inside the wheel halves themselves. Assuming a fixed-pitch prop, there could be hidden corrosion not found until the prop is removed from the crank, and the blade repairability is probably unknown. I don’t know whether the Lycoming crank nose AD will apply to this application. If it does, though, and has not been complied with, there may be unairworthy pitting by now in the nose of the crank.
Presumably the avionics could be tested, but with the results unlikely to be very good. Antenna connections have probably deteriorated. Bearings in things like gauge needle movements and gyros have probably been affected. The instrument air hoses and gauge hoses for oil, fuel, and fuel vent are probably all stiff as boards. A piece (or pieces) may come off on the first engine start, or may just wait to haunt you well down the road. Instrument air fitting screens may at first help protect the main gyro instruments (if they are there); maybe the first failure will just be the vacuum pump. Oddly enough, while vibration is often viewed as the enemy in our aircraft, it just as often goes a long way toward keeping things dry, lubricated, and flexible. When large aircraft first transitioned to jet engines, using the same avionics installed in their piston forebears, vibrators had to be installed in the instrument panels to keep the gauges working right.
In my opinion, it would cost so much for the level of inspection that will be required to determine the safety and repairability of this plane, that it would have be almost given away to take the risk. You would have to find out whether the seller is willing to pick up the tab for this, using your mechanic, not the seller’s. I believe that it will take dramatically more time than any normal annual inspection, much less a simple pre-buy on a local known entity.
This seller will almost surely have to either find an unwary buyer, or set a giveaway price to enable some A&P to buy it as a year-long (or more) project plane. Even the latter would still require enough inspection to rule out unairworthy corrosion in the fuselage, wings, and empennage. An A&P could also locate, buy, and install a good used lower-time engine with good logs, or a higher-time one with more likely repairability. Things like crankshafts are pretty expensive. What is more likely (failing a sucker that falls in the seller’s lap), the seller will eventually find that it has to be sold as salvage, worth more as parts due to being of uneconomic repair.
Do you know why it has remained out of service, despite the owner’s illness? Are the conditions of storage known (tied down in the weeds, tied down on a ramp, parked in a shed hanger, parked in an enclosed hanger, parked in a climate-controlled hanger, etc.)? What part of the country is it in? Homestead, FL, or Arizona? What does all the interior material look like (upholstery, plastic parts, air vents, headliner, carpet)? Have they apparently held up, or have they been affected by the long storage? How about all the acrylic windows and windshield?
I know that this sounds like terrible gloom and doom, and I am actually an optimist at heart. As an A&P, if I were interested in this, I would probably spend a week going over it. I would remove at least one cylinder, to look inside the bottom end. I would probably pull both magnetos, to look inside the accessory case with a borescope or light and mirror (and to examine the magnetos). The mag capacitors have probably gone bad from disuse. If not regularly charged and discharged, electrolytics tend to go bad. The mags would probably require overhaul.
Well, I guess I could go on like this for a long time. Without a great deal more info about the story of its disuse, if I were you I would rule this plane out. It’s just too huge a gamble. You are far better off paying $40,000 for a perfect and premium-equipped example of a $30,000 average-price plane, than you are paying $20,000 plus $30,000 in strung-out repair and upgrade costs, to achieve the same premium example of that $30,000 plane. The former avoids all the maintenance down-time, and is also likely to have far fewer long-term expensive surprises. None of us can do a perfect pre-buy inspection; we just can’t do that level of disassembly, and haven’t the equipment for it. Even a very thorough annual inspection would not be adequate in this case. An eventual nasty economic surprise would be highly likely, assuming you actually took the chance of flying it without certainty of condition of all the things I have mentioned.