Ask Pete!

by Pete Schoeninger
Published in Midwest Flyer – April/May 2018 issue

Q: With spring just around the corner, are there any hazards especially associated with spring that I should be reminded of?

A: Yes, birds and bees and crosswinds. Birds will be building nests to start new families with the arrival of warm weather, and sometimes they will build a nest in the engine compartment, or the tail of an airplane. Bird nests can completely block airflow to one or more cylinders, thereby damaging the engine or causing a fire hazard. Nests can also jam control cables in the tail of an aircraft. It is easy for a bird to get into the engine thru cowl openings, and thru the tail openings where the horizontal tail joins the fuselage. Look closely for nests with each preflight inspection you do because birds can build a nest in a day or less. Bird droppings on your propeller or tail area are signs that there may be a new resident in your airplane.

Bees (and other insects) can plug up your pitot system or fuel vents. A plugged pitot static system means no usable airspeed, altitude or rate of climb information. A plugged fuel vent often results in a forced landing due to fuel starvation. Your mechanic can show you what to look for on pitot and fuel vents, as they vary from model to model.

Spring also brings unstable air and strong gusty winds. Now would be a good time to practice crosswind techniques if you can find a good flight instructor and a good crosswind. The combination of rusty pilots (from little flying during winter) and strong spring winds have pushed lots of airplanes off runways resulting in embarrassing and expensive repairs.

Q: I noticed that the Piper Comanche was available with 180, 250/260, and 400 hp engines. How did Piper manage their empty center of gravity with such varied weights in the nose?

A: If you look at a Comanche 180 (4 cylinders) with the cowl off, you will see that the engine mount moves the engine far ahead of the firewall. The 250/260 hp (6 cylinders) model has a shorter engine mount, so the furthest aft two cylinders are closer to the firewall, so the CG change due to the additional two cylinders is not huge. The 400 hp (8 cylinders) is in many ways a different airplane. Among other things, Piper put a larger, heavier tail on it. Only about 150 400 hp air-planes were built. I did fly one a couple of times; it had lots of power as expected, but a massive fuel burn. Kind of like the old Pontiac I once owned. It could pass everything on the road except a gas station!

There are many things aeronautical engineers do to compensate for changing empty center of gravity from engine changes. One of many is that the airplane battery can be positioned in various places, such as in the rear of the fuselage, or on the firewall, or beneath rear seats as needed for a desired empty C.G. location. And the most famous C.G. solution of all was when the Piper J-3 Cub (two tandem seats) was found to have a very forward C.G. location when flown solo, so the instrument panel was placarded “Solo flight from rear seat only!” Not high tech, but it has worked well for 70-plus years on Cubs.

Q: I have a 1966 Cessna 172 and would like to do some off-airport landings with it, and to that end I am thinking about installing larger tires. Is that possible? Does it make sense?

A: Possible, yes. Does it make sense? I wouldn’t, but you judge, because it will be expensive, increase your empty weight, and add more drag, reducing cruising speed. You will have to install a new larger nose fork, and then three bigger wheels and tires, probably new brakes, and this assumes your mechanic can find an available STC to allow these changes. Figure probably at several thousand dollars to do it. For the cost and benefits received, I suggest you only consider it if you plan on keeping the airplane for a long time. Your mechanic can give you more specifics. An-other solution for off-airport work might be a tailwheel airplane like a Cessna 170 or 180, Maule, Super Cub or Citabria.

Q: A friend of mine had an alternator conk out on his Cessna 172 in flight. He told me as a precaution he turned his master switch off, and landed 20 minutes later without incident. Wouldn’t the engine quit when he turned off the master switch because of no electric power to the spark plugs?

A: No. Spark for most airplane engine spark plugs comes from magnetos that are driven by the engine turning, not a battery. A very old system, but it allows the engine to be run with no electric system (think old Cubs, Taylorcrafts, etc.). Depending on the year of your friend’s 172, he may have had a split master switch. That is, the switch is really two switches – one for the alternator and one for the battery. This allows you to take the alternator off line if needed, but still allows use of the battery for radio calls, lowering flaps (in newer ones), etc.

Q: All of the Cessna 172s I have seen have an oil cooler. My friend has a very early 172; I think about 1960. He says he has NO oil cooler. Is this possible?

A: Yes, 1956 to 1967 Cessna 172s had the Continental O-300 engine rated at 145 hp. Like smaller Continentals, it did NOT have an oil cooler. In 1968, Cessna began installing the Lycoming O-320 150 hp engine, which had an oil cooler. I felt that engine change was an improvement, as the O-320 had more power with less weight, and in my experience, was reliable and long lived.

Q: What is the most affordable metal airplane to own and maintain that’s roughly 50 years old or less?

A: By most economical to own, I presume you mean buy? It would be a tossup between a Cherokee 140 and a Cessna 150/152 made in the mid to late 1970s. (The last Cherokee 140 was made in 1977.) Expect to pay around $25 -$35K for a nice version of either. They are humble mounts, but as airplanes go, tough, durable, and easy to fly.

In my opinion, the overall best buy available right now would be the four-seat Piper Warrior made in the 1970s. On the used market the Piper Warrior is roughly $10K less than a similar Cessna 172. Expect to pay $35K or so for a nice 1975 Warrior, and $45K for a nice 1975 Cessna 172. Their performance, reliability, etc., are just about the same. Please don’t forget my standing lecture: Be SURE to have an airplane mechanic check over any airplane before you buy it. Also, have a title search done to your satisfaction. I can tell you dozens of horror stories about owners who did not take these precautions.

Q: I have inherited a stash of airplane parts from my recently deceased father. He had completely disassembled an old Aeronca Chief, and bought some replacement parts, and he has a nice binder of receipts for everything. I am wondering if I should hire someone to complete the project, or sell it as is, and if so, what I might expect to get for the completely disassembled hangar full of stuff?

A: Your path of least resistance and my suggestion, would be to sell what you have. Do NOT expect to get anywhere near what your dad paid for the sum of the parts. The only exception to this would be if there is an engine with a very recent overhaul, that may be worth as much or more than your dad paid for it. If you have to pay someone shop rate of say $50 – $90 per hour to put everything back together, and cover and paint it, you will be buried in it and lose a lot of money when you sell it.

Q: I occasionally land my Cessna 150 on my dad’s hayfield. But now I notice the grass is dying where I have been landing and driving my pickup truck. The same thing happens on my lawn when I drive my truck on it several times. Why doesn’t this happen on turf runways at legitimate airports?

A: Dad’s hayfield probably has legumes like alfalfa in it. Alfalfa makes great hay, but it damages easily, as do other crop grasses. Turf runway grasses are often a mixture of Kentucky blue grass, rye, fescue, etc., which are pretty hardy. Drainage is also important, and clay soil is your enemy, and it turns to muck when wet. You can find lots of information by doing an internet search for “Turf Runway Construction.”

Q: Have you ever seen a ski plane land on grass? I mean on straight skis, not wheel ski combos or retractable skis?

A: The only time I have ever seen it done was by aviation legend, Dale Crites, who landed a Cub equipped with skis on grass that had just been watered down by the local fire department. Dale told me that landing on grass with skis is a delicate and dangerous undertaking because you can easily end up on your back, with major damage to the airplane and possibly its occupants. DON’T TRY IT!!!

EDITOR’S NOTE: Contact Pete Schoeninger at with your questions for this column or for consultation on aviation business and airport matters. Pete has four decades of experience as a line technician, airplane salesman (300 aircraft sold thus far), appraiser, snow removal supervisor, airport manager, and as the manager/co-owner of a fixed base operation.

DISCLAIMER: The information contained in this column is the expressed opinion of the author only, and readers are advised to seek the advice of others, and refer to the Federal Aviation Regulations, Aeronautical Information Manual, Pilot’s Operating Handbook for the airplane(s) they fly, and other instructional materials before attempting any procedures discussed herein.

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