A Battle Against Time
October 1, 2020
Time always works against you, and it’s the job of your mechanic to reduce the impact of time on your plane. One of the larger issues I’ve seen in general aviation is inactivity. Wear and tear will occur as aircraft total time climbs, but not flying your aircraft seems to be the real killer. The impact of inactivity over the years outweighs the normal wear and tear you get flying your plane regularly. Normal wear and tear can be easily managed by your mechanic, but major component replacement is where big money is spent. Inactivity disproportionately affects these more expensive components and maintenance items. Engines and accessories, constant speed props, older avionics, and any type of dynamic seal suffer from not being exercised.
Both hours flown and calendar time can take a heavy toll on aircraft. Most manufacturers of aircraft products have recommended maintenance intervals and overhaul times in both hours flown and calendar years. Both of these time categories need to be considered when making decisions on how best to care for an aircraft or component. The amount you fly in a year directly impacts how well your aircraft will hold up.
I have worked with many aircraft owners who pulled a plane out of storage to either sell or make it airworthy again, and I have been a part of buying and restoring these older low time planes. We always include the cost of an engine overhaul into our budget for buying an aircraft with low hours per year. These engines will have a low time since overhaul, but they will often start making metal after a couple hundred hours of flight. Similarly, we will see failures of dynamic seals after they have been actuated or cycled a few dozen times. Once all of the inactivity issues get worked out, they do return to a normal operating well exercised condition.
So how much should you exercise your aircraft? The five hundred hours a year we put on our planes is probably too much for your average owner. You do see an increase in operating costs as you get into the multiple hundreds per year. I would say an ideal number would be one hundred hours per year. That way, your six-month recommended oil change would perfectly line up with your 50 hour oil change and your annual inspection. Of all the aircraft I have maintained, aircraft that fly around one hundred hours per year seem to have the fewest problems. Anything close to one hundred hours per year (60-120) should keep your plane healthy. Aircraft that fly ten or less hours per year don’t fare well once they start flying regularly again.
Most of my interaction with aircraft owners boils down to the question of how much time do you want to buy. Everything can be fixed or replaced. It’s up to the owner/operator to make the best informed decisions for the desired operations. Let’s consider the factor of times in our troubleshooting, decision making, and potential value calculations.
Here’s to blue skies and smooth engines!