Ask Pete!

by Pete Schoeninger
Published in Midwest Flyer – August/September 2017 issue

Q: Do pitch changes occur with power changes in an airplane with the engine mounted above the cabin like a Lake Amphibian?

A: There are significant pitch changes with large power changes. But in your checkout, you should learn how to handle these with trim. Lakes have large trim surfaces, and when trim tabs are properly positioned, pitch is easily managed.

Q: I am fascinated by the good looks of a new fixed pitch wooden prop a buddy had installed on his Aeronca Champ. What are the pros and cons of a wood prop versus a metal one?

A: Wooden fixed pitch props are 10-15 pounds lighter, look better, often cost less, and spool up quicker (because they are lighter) than metal props. They should never be stored outside, their prop bolts should be re-torqued a couple of times a year, and they will deteriorate faster than a metal prop. In my experience, performance suffers a little because the prop is thicker toward the tips and thus not quite as efficient as a metal one.

It is important to note that there are a very limited number of different props that can be legally installed on each airframe/engine combination. Your mechanic can check for applicability. There are resonances and harmonics issues between the prop and crankshaft which can cause catastrophic failures if the wrong prop (wood or metal) is installed on an airplane.

Q: Someone told me Cessna 140 and 170 airplanes have landing gears that are nicknamed “Leaping Lizzies.” Why would that be?

A: Their landing gears are well designed, tough, and “springy.” If you happen to screw up and get one bouncing (easily done – I know) during a landing attempt, especially a wheel landing attempt, it is often best to go around and try again.

Q: My local FBO has a fairly active rental and flight school business. They often run the engines in their C172s to 2500 hours or so with no problem according to their shop foreman.  But that same guy told me my engine (very similar 180 hp Lycoming) with only 1500 hours is due for overhaul. Is he a crook, or looking out for my welfare?

A: I suspect the latter. In busy flight school situations, airplanes fly several hundred hours a year versus perhaps 50 – 100 hours a year for privately owned airplanes. That means the flight school engine parts are pretty well covered with oil on start up, and yours are not after sitting several weeks between starts. Thus, your engine may well have more wear in less hours because of lack of lubrication on startup than more frequently flown engines. Remember that both Lycoming and Continental recommend engine overhaul at no longer than 12-year intervals, and also have hourly recommendations, usually 1500 – 2000 depending on model.

Q: I am new to aviation and recently bought a used Piper Warrior and learned to fly in it. I am happy with the airplane, but very frustrated by “The System.” I am fairly handy and have modified my cars and motorcycle engines with good results. But the local A&P mechanic at our field says there is almost nothing I can do legally to modify my engine. A friend (not a mechanic, but a pilot) suggested I change the registration of the airplane from Standard to Experimental so I could “play” with it more. Is that possible?

A: You’ll have to go through the local FAA maintenance people to change registration status. Their answer is going to be emphatically NO. The FAA has a very dim view of this, otherwise you would see it done frequently for the reasons you state. If you have time, I think it would be a great (and free) education to call your nearest FAA Flight Standards District Office (FSDO) and ask for an appointment with one of the maintenance inspectors. It would be a good eye-opening education for you to sit down with someone for 20-30 minutes. I have found most inspectors are congenial and happy to help.

Q: I have heard that landing on a runway with a significant rise, or drop, can be difficult judging height in the landing flare. Why?

A: When you land your airplane on a reasonably level runway, you are used to a certain perspective looking perhaps 200 feet ahead of the airplane when your wheels touch the runway. If you are landing on a runway that has a rise or drop of say 5 feet per 1,000 feet of length, that is one foot per 200 feet. So, the height above the runway of your wheels is going to be either one foot higher or lower than you are used to. Thus, landing uphill, your wheels are going to be a foot off the ground when you think they should be touching the ground, and your wheels will hit the ground before you expect if you are landing downwind. So not a crash, but a bit of thump on arrival.

Q: In the last issue of Midwest Flyer Magazine, you discussed the Cessna 177 Cardinal, which was supposed to replace the Cessna 172 Skyhawk, but did not. What do you know/think of the Cessna 172 Hawk XP and C172 RG Cutlass, each produced for a few years around 1980, but were not production survivors?

A: They are both good airplanes…I’ve flown and sold many of each model. The C172RG was Cessna’s answer to the Piper Arrow, an airplane that met FAA training requirements for a complex trainer. The Cutlass has 20 more horsepower than the C172 of the same vintage, but is heavier, so its takeoff and climb difference seems to me no better than straight C172s. The Cutlass is about 12 mph faster because of its retractable gear, and has large fuel tanks, but with full tanks, the cabin load is quite limited. With a lighter cabin load and economical power settings, the Cutlass has a range of almost 800 miles. In my opinion, the Cutlass is a great value if you can find a nice one with good maintenance history. As airplanes go, they operate fairly economically, as well.

The Hawk XP is one of my favorite airplanes. It has 195 horsepower, and can be easily converted to 210 horsepower. Takeoff and climb performance is impressive, but cruise is – like the Cutlass – only about 10 mph faster than a straight C172. Also, with higher engine overhaul costs and shorter engine life than straight C172s, operating costs for the Hawk XP is significantly more than the C172. Hawk XPs are sometimes found on floats because of their added power.

As single-engine piston sales dropped rapidly during the early 1980s, Cessna made the decision to stick with only one entry level four-seat airplane, the C172, which is still in production to this day. In production since 1956 (excluding a 10-year shutdown of all single-engine airplanes by Cessna), the C172 has always been a sales leader. Cessna got it right when they designed the airplane, and over the years have tweaked it only a little. It sort of reminds me of the Remington 870 shotgun, or the John Deere 4020 tractor, or Ford Mustang. When you have a winner, you keep building it.

EDITOR’S NOTE: Contact Pete Schoeninger at pete.harriet@gmail.com 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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