Periodically you should inspect your helicopters and ensure that they are in tip-top shape. To make sure something isn’t missed during the following inspection, I recommend starting from the nose. Certainly this list isn’t complete depending on your particular helicopter and the degree to which you do the inspection, so modify it as needed.
CANOPY
Remove and check for any cracks or splits, especially at the seams if it’s the type that has been glued together. The mounting rubber grommets, latches, etc., should be in good condition and not worn from previous vibration.
SERVO TRAY
Check for cracks and loose mounting bolts. Twist and push-pull gently to check for a solid tray and ensure it is well mounted to the frame.
PUSHRODS
Check ball links for wear and an overall snug fit. Balls and links can wear very easily if they get dirty or have fuel on them from being near the engine/exhaust. If in doubt, replace both. Then, disconnect all pushrods from their servos and push-pull with your hand to check for slop or binding. Ensure all pushrods are straight.
BEARINGS
Although you should have given all bearings a coat of oil when the helicopter was put up for the winter, oil them again or pack them with bearing grease as needed.
LANDING GEAR/SKIDS
Check that they’re secure and straight. If they’re made of metal, they may need to be bent back into proper position to keep the helicopter straight and level as it sits on the ground.
FRAME
Check that all nuts and bolts are secure. Check for vibration or stress cracks, especially around the engine and skid mounts.
HEAD
Although not really necessary, it would be a good idea to remove the rotor blades and head. If it has been a while since the thrust bearings have been greased, now would be the time to do it. This will also enable you to check the head closely and inspect it for bent links, pushrods or flybar. Check the balance of the head/flybar using a High Point or Du-Bro balancer. 
The head is the highest stress point on the helicopter and should be disassembled, inspected and lubricated at regular intervals. Then, rebalance and check all moving parts for freedom of movement.
The main rotor blades should receive special attention since they are the most dangerous part of the helicopter if they should fail. This especially applies to wooden blades. I hang my helicopters from a small hook attached to the ceiling, and I have had a wooden rotor blade fly off the helicopter on one of its first flights of the new year. Since I had been flying that helicopter the entire previous year with no problems, I can only guess the dry heat near the ceiling during the winter dried out the wooden blades and root reinforcements causing them to weaken. If there is any doubt about their condition, remove the covering and inspect the wood itself; the covering can hide a lot of potential problems. I certainly don’t like discarding a questionable set of rotor blades, but the alternative is losing the entire helicopter and endangering everyone else at the field.
Even if you believe the rotor blades are in suitable condition for another season of flying, give them a close inspection. Are the tips in good condition or have they been scraped on a near tip-over? Are they still straight and true without any warps? Check the blade reinforcement at the root for any signs of fatigue or the mounting hole being enlarged.
Wooden rotor blades deserve special attention. Check that the blade reinforcement is secure and there are no cracks in the wood. Covering can be tightened with a hot air gun.
TAIL BOOM
If you have not already done so, drill a small hole from the mounting bracket into the tail boom and insert a small self-taping screw. This will keep the tail boom locked in place. If the tail rotor is belt driven, check the belt for signs of wear and adjust tension. Then, apply a small amount of silicone lubricant to the belt to reduce drag. Lubricating the tail rotor belt on my Thunder Tiger Mini Titan has added up to a minute of flying time.
Lubricate tail rotor belt drives to reduce friction and prolong belt life. This has added up to a minute of flying time to my Mini Titan.
TAIL ROTOR GEARBOX
All gearboxes should be disassembled, inspected and re-lubricated. Be especially careful to check the security of the tail rotor and associated linkages; they take a lot of stress and the high rpm causes bolts to loosen.
SET SCREWS
Now that you are sure everything is lubricated, add more Loctite to all of the set screws. I understand they were tight when you put the helicopter up for the winter, but remember that this is a safety check and just a little more diligence may prevent an accident and the loss of a helicopter. Look at the plans for the helicopter to make sure you remember where all the set screws are located, and disassemble as required to get to them.
My technique is to remove the set screw, and then clean both the hole and screw as well as possible. Using a removable type of Loctite I place a drop in the hole with another drop on the set screw, and then screw it in place. This little extra Loctite placed in the hole will fill any small air gaps securing everything in place. I have used this technique for years and have virtually eliminated set screws coming loose. Try it!
FUEL TANK
You should not have stored the helicopter with fuel remaining in the tank, but if you did, now is the time to remove that old fuel and clean the tank. Fuel lines can get soft with age so it’s best to replace all fuel lines inside and outside of the tank. Check that the clunk weight is secure to its tubing and free to move to all corners of the tank, especially if you plan to fly inverted.
RADIO
Cycling both transmitter and receiver batteries after storage is a good way to check each cell’s ability to hold a full charge. Also, closely check the connectors and wires for any breaks, frays, etc. Look particularly close to where the wires go into the connectors. If they have been pulled on it’s possible for the wire to become dislodged from the connector.
The rubber servo grommets should be secure between the servo and tray, but not so tight as to prevent their vibration protection. Also, check the foam rubber that protects the receiver, battery, etc., and replace as needed. Servo arms also take quite a stress load from a season’s flying, so make sure they aren’t cracked or have enlarged holes. Replace as needed. I also like to disconnect the servo arms from the servo and inspect the shaft output splines. As a final check of the servos, operate each throughout its full range of movement and look and listen for any signs of abnormal operation.
Check that the antenna is free from cracks, rubs, etc. Any minor problems with the wire covering can be corrected by placing a small piece of heat-shrink tubing over the bad spot. Accidentally tugging on the antenna could also have weakened the wire or solder connection to the receiver circuit board. If in doubt, take the receiver case apart and check the connection to the circuit board.
When everything looks as good as it can get, give the entire system a range check. To get an accurate range check, have the canopy in place and route the antenna away from the side frames or other electrical components. Compare this range check to the distance you were getting last season and make sure it’s more than the minimum recommended by the radio manufacturer. If your radio does not pass this check do not even start the engine. Have a qualified technician check it out.
Battery and electronics should be secure with all wiring neatly routed and protected. Check servos, output horn, pushrods and balls/links for wear or slop. If in doubt, replace.
GYRO
Again, check the wiring and connectors. Also check for proper servo movement with the radio turned on as if flying. As the helicopter nose is moved gently right and left the gyro should be giving smooth commands to the tail rotor servo. Even if the gyro mounting tape looks good, remove it and replace it with new tape. The old glue could be weak and dried out, and the foam could be weak and ready to split from heavy maneuvering.
ENGINE AND MUFFLER
Take off the carburetor and glow plug. Disassemble the carburetor as much as possible and check for foreign matter or dried fuel, oil, etc. Clean with solvent and lubricate. If the engine has a caked-on black oil residue, it can be brought back to a near new condition by cleaning with Demon-Clean engine cleaner. However, be careful because it’s quite corrosive to paint, table-tops, etc.
Disassemble, clean and lubricate the carburetor. The rest of the engine and muffler can be cleaned with Demon-Clean to make them look brand new.
I’m sure you can come up more inspection points to suit your particular helicopter, but this checklist should get you on the right track. Although this may seem like a time-consuming check, once you get started it should not take long to do the entire helicopter unless you find some other problems. And it’s a lot better to find these problems on the workbench than at the flying field.
