Ask Pete!

by Pete Schoeninger
Published In Midwest Flyer – Oct/Nov 2016

Before I start answering questions, I wanted to take a minute to thank Mark Baker (AOPA) and Jack Pelton (EAA) and their respective staffs and members for keeping the heat on Congress for years until the recent medical reform was passed. And, shame on the FAA for not being more cooperative!

Q: Last winter at our small airport, the guy in charge of snow removal waited until the snow had ended before plowing the runway. I asked him why, and he said freezing rain was forecast in the next hour and he wanted to wait until the freezing rain came and left. Pete, you removed snow for many years as an airport operator… Why do you think the guy declined to promptly plow us out?

A: My guess is, had he plowed the runway clean just before freezing rain occurred, your runway could (if runway temperature was below freezing) be covered with a clear sheet of ice. (Remember, freezing rain is rain falling into air that is below 32 degrees.) Ice on a runway is dangerous and hard to remove, but if the freezing rain falls into the top of say 3 inches of snow, the whole mess usually can easily be removed with plows and possibly a snow blower.

Q: When snow arrives (I live in northern Minnesota), I remove the wheels on my Cessna 170B and put on skis. A friend said I really should amend the weight and balance info to reflect this change of equipment, and have new weight and balance computed as well. I don’t believe I legally could do the computations, although they would be easy to do, so would I have to have my mechanic sign off each change, in other words, twice a year?

A: What some mechanics will do is make an entry in the weight and balance paperwork to specify the empty weight and center of gravity (CG) on wheels, and when equipped with (name and model) skis.

Q: You answered my question about the prop pitch (Numbers 7653 mean 76 inches in diameter and 53 inches forward travel per one revolution, if no slippage) on my C-172L in the August/September 2016 issue of Midwest Flyer Magazine. Now answer this please…. Why, when I am approaching to land, with my throttle pulled fully back, does the engine idle at about 1000 RPMs, yet when stopped on the ground, the idle is at about 700 RPMs? Why the difference?

A: Your prop, with a 53-inch pitch, if 100% efficient, and if not attached to anything (in other words, in theory only), would move forward about 36 mph. (700 RPM X 53 inches/12 = 3100 feet per minute, or about .6 of a mile, or 36 mph). So when you are traveling at faster than 36 mph and your engine throttle control is set at idle, the prop is not pulling air; it is being pushed to a higher RPM by air approaching from the front (relative wind.)

Q: A friend and I are both certified flight instructors and we are thinking of starting a small FBO at our local airport to replace the current FBO who is leaving. Are FBOs good moneymakers?

A: In my experience, a small FBO is not going to make much money doing a small amount of everything, like the usual stuff… flight instruction, fuel sales, and maintenance  The folks that seem to be doing okay right now often have a specialty, such as lots of maintenance from based customers and customers from surrounding airports, jets to base with them which will buy a lot of fuel, or some other unique specialty.

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