Airplanes that sit for extended periods tend to develop problems over time that may go undetected until you really need the airplane for your next flight. It is common to think that less flight time on an airplane leads to less maintenance problems, but that is only partially true. Low overall time is good, but extremely low or intermittent usage can be detrimental to your airplane and engine.
Ground Run-Up vs. Actual Flying
Some pilots believe that they can take their airplane out once a month and do a ground run-up on the engine to make up for lack of use. This approach; however, does not get the airplane up to full operating temperatures and power settings. Airplane engines actually benefit the most from going through a full flight cycle, including takeoff at max power, flying in cruise and normal power settings, and getting the oil warm enough to boil out any water or condensation that may have formed.
In addition to the engine, the airframe and other parts benefit from the regular use and flight of the airplane. Oleo struts get exercised; the batteries get charged; avionics are warmed up; wheels get turned; flaps get tested; gear gets exercised; and cables, pulleys, springs, and other flight control components are exercised.
The magic formula: 1 hour flight every 7 days
Ideally, I would recommend flying at least one hour per week on average. This is sufficient to keep the airplane in good shape for flying, and gives you a good reason to take a friend out for a $100 hamburger.
Continental’s IO-550 Installation and Operation Manual states the following: “Environmental conditions (humidity), seasonal changes, and engine usage influence susceptibility to corrosion. Engines that are flown occasionally (less than one time per week) are more vulnerable to corrosion under these conditions. The best method of reducing the risk of corrosion is to fly the aircraft weekly for at least one hour. The owner/ operator is ultimately responsible for recognizing corrosion and taking appropriate corrective action.”
Storage More than 30 Days – “Flyable Storage”
If you need to store the airplane for an extended period without use, this can be done if proper guidance is followed. Most manufacturers offer recommendations in the AFM for “flyable storage” procedures. This may include replacing the oil with special preservative oil, and other additional procedures as specified by the manufacturer. The guidance can typically be found in the “Airplane Handling, Service and Maintenance” section of your Airplane Flight Manual, with references to your engine and airframe maintenance manuals for additional maintenance-specific procedures.
Some climates may require additional preservation considerations:
- Close to oceans, lakes, or rivers
- Humid regions
Top Off the Tanks
It is also recommended to keep the fuel tanks topped off when storing the airplane for any length of time. This helps minimize the chance of condensation forming in the tanks.
Benefits of Frequent Flights:
- Engine warm-up
- Oil heated sufficiently to boil out the water/condensation in the oil (typically around 170-200˚F)
- Less susceptibility to corrosion
- Batteries recharged
- Avionics and electrical system actively in use and warmed up
- Oleo struts, seals, hydraulics, and other moving parts get exercised or checked
- Prop and prop governor exercised and oil cycled through system
- Landing gear gets exercised (if retractable)
- Flaps exercised
- Pilot proficiency, of course!
- Fuel and oil get used. When additional oil is added, it helps dilute the used oil making the oil incrementally cleaner between oil changes.
- Helps control the bug population!
- Flight control cables, pulleys, springs, etc exercised
Remember, 1 week = 1 hr flying
Ideas to Keep Your Airplane Flying
Not everyone has time or reason to fly one hour every week. If not, you should consider some alternative ideas for keeping your airplane flying or some other good ways to put the time to use.
Keep the airplane flying when you’re too busy:
- Hire a pilot to fly the airplane for one hour and evaluate the systems of the airplane
- Let a qualified pilot friend use the airplane
- Offer your flight instructor free time in the plane in exchange for keeping it flying regularly
- Find someone to manage the airplane and track the flight time and give them guidelines for how often you want the plane flown if you aren’t using it.
If you want to do the flying yourself, but want to make the most of the time, consider these ideas:
- Training – Probably the number one best use of the flight time if you have no other reason for the flight
- Practice – Fly practice approaches and maneuvers on your own, but have a plan
- $100 hamburger – Take a friend out for lunch at an airport restaurant
- Volunteer – These turn your flights into tax-deductible and rewarding experiences. Angel flights and PilotsNPaws are some examples. More ideas here: https://www.flyhpa.com/2015/06/volunteer-opportunities-for-aircraft-owners/
- Give someone their first airplane ride and help inspire future pilots
Remember, your airplane wants to fly!