First, congratulations on your purchase. 310s are awesome airplanes: fast, roomy, good-looking, and mostly easy to work on if you know what you’re doing. That’s the good news…
The bad news is that your “new” airplane is old.
The first 310 was built in 1955; the last was built in 1980. That means your new airplane is anywhere between 45 and 70 years old (as of 2025.) And I promise you, no one has been keeping up with the required maintenance. No matter how nice your new 310 is, you just bought a project…
“But… you say, “it’s had annual inspections, the gear has been swung, oil changed, control pulleys doused with oil… what else could it need?”
Ok… when was the last time the nose strut was removed from the aircraft and the trunnion bearings lubricated? Probably never. The Service Manual says to do this every 3 years but I haven’t seen a single 310 where this has been done. It’s difficult, heavy, and very awkward. And it will take a few custom wrenches or help from a 10-year-old girl with very small hands. It’s not a fun job.
When was the last time the main gear struts were removed and those trunnion bearings lubricated? Absolutely never because Cessna never provided a way to do that. It’s not even listed in the Service Manual. But those bearings are not sealed. How long do you think that grease will last? Not 45 or more years, that’s for sure. I’ve seen a few that were frozen solid. That’s why I invented and sell a tool for injecting grease into those bearings. (Shameless plug… You need this tool.)
Here’s another item: between the electric motor and the landing gear actuator, there is a baseball-sized gearbox. The Service Manual makes no mention of this gearbox, yet every one of these I take apart, the grease has turned to the consistency of candlewax… hard and dry. If one gear in the box breaks, your landing gear won’t come down. So it makes sense to grease this gearbox. (Note: this is not the large dinner-plate size actuator with grease fittings. The gearbox I’m talking about has no grease fittings and is between the actuator and the electric motor.) Oddly, the Service Manual does mention a similar gearbox for the flap actuator, and says that it should be removed and repacked with grease every 1500 hours. So I imagine the same interval would be appropriate for the landing gear gearbox. Has yours ever been done? Probably not.
Ok, so here is my list of what you should do with your newly-acquired 310:
(Landing Gear)
Jack the airplane and overhaul the landing gear system. I mean remove every single piece and make it all new again. Strip the paint off, inspect, replace bearings, replace all the hardware, and make every single part perfect. Definitely Magnaflux the main gear torque tubes and the fork-head bolts. These have been known to break. If the airframe has more than 5000 hours, you might want to think about replacing the torque tubes and fork-head bolts (very expensive.) Reinstall everything and rig it correctly.
(Flaps)
Remove the flap motor and gearbox. Disassemble and grease the gearbox.
Remove the flap scissors, clean, and lubricate.
Remove the flap mechanism from inside the wing (just aft of the main wheel wells.) Clean and lubricate the bearings that live inside the bellcranks.
(Flight Controls)
Remove the flight control surfaces and replace the bearings. All of them. Don’t forget the bearings under the floor and in the tail.
Remove the aileron bellcranks inside the wings. Lubricate the open needle bearings in there. The inner race will probably be badly worn (bad design.) Don’t lose the brass thrust washers.
Remove the 3 trim actuators. Disassemble and grease. Service Manual says to do this every 1000 hours but nobody does it because it’s a horrible job.
Replace all of the cable pulleys, even if they move freely. They are old and worn out. (Note: spraying the pulleys with oil is useless. They are sealed bearings and oil will not get into the bearing. Replace them.) Carefully examine the flight control cables. Replace any that have any sign of wear, rust or broken strands.
Remove the control column. Replace the pulleys and lubricate the chains inside.
(Engine Controls)
Disassemble the engine control pedestal; clean, lubricate… make it new again.
If you have the older Teleflex engine control cables, identified by the hard aluminum casing, remove the inner cables, lubricate with black moly grease and reinstall. A better fix is to replace all of the cables with modern flexible cables. The cables will have to be custom-made and brackets may need to be fabricated for the carburetor / fuel injection control valve ends.
(Brakes)
Replace the short hoses at the brake master cylinders. Overhaul the master cylinders while you have them out.
Replace the longer brake hoses on the main struts. Disassemble brake calipers and replace the O-rings.
(Engine)
Change oil and filters.
Adjust the carburetors or fuel injection system.
Overhaul the magnetos. Clean spark plugs and replace the ignition wires.
Overhaul the prop governors.
(Engine Hoses)
Replace all of the hoses in the engine nacelles. If you have oil and fuel pressure hoses under the instrument panel, remove them and replace with the proper 1/8-inch copper lines. (Those -2 hoses are not rated for oil or fuel. They will leak.)
(Wiring)
If you have the old-style circuit breakers that can’t be pulled, replace them with pullable breakers.
Replace all of the wiring between the generator / alternators and the regulators. Add a ground wire from the regulators to the negative post on the batteries.
(Fuel)
Remove the fuel control valves. Disassemble and replace the o-rings inside. They are probably bypassing internally.
(Avionics)
Remove the antennas. Clean off all of the corrosion that is there. Replace the antennas with new if they are more than 10 years old. Replace all of the coax cables.
(Seats)
Remove the front seats and FIX them so they move smoothly. Remove the rollers in the seat support structure, clean and oil. Flip the seats over and look at the rails; they are usually in terrible condition. File the rails so they are smooth and straight. Replace them if you need to. If you have Phillips head screws attaching the seat stops, replace them with socket-head (Allen) screws. Doing this makes the seats so much easier to remove. Nothing screams BAD MAINTENANCE like seats that are hard to adjust.
(Heater)
Remove the heater and have it overhauled. Or just replace it and do away with the ADs.
Install an hour meter for the heater. Replace all of the ducting.
(Corrosion Prevention)
Spray the wing spars (front and rear) and the nose wheel well with ACF-50.
Here’s the thing… as I said some of these planes are approaching 70 years old. They will not continue to fly indefinitely with only routine maintenance. At some point, the airplane becomes “timed-out” and it needs to be completely rebuilt. The airlines do this and call it a D-Check. You don’t need to do everything on this list all at once. Start with the landing gear overhaul and gradually work down the list as time and money allow. If you read something on this list and wonder “Why?” call me and I’ll explain everything.
So now you’re thinking about how much this will all cost; and you’re right… it will be a lot of money. But you need to realize that a 310 is not a $35,000 airplane. Years ago, Cessna said that if it were being made today, a 310 would cost over $1,000,000. So you need to understand that you might have paid $30,000 for your 310, but that’s a million-dollar airplane sitting in your hangar.