October 2014-
Q: Hi Steve,
I fly a 1972 Piper Cherokee 235. I’ve owned it for 17 years and it’s been a spectacular airplane that has fulfilled every travel need for our family, and it’s also helped me grow my business by cutting down on both travel time and costs to service my clients.
Over the years I’ve upgraded the avionics and my qualifications and now am very comfortable in my Cherokee during IFR conditions. I average around 150 hours a year.
I’ve always felt like I keep myself in good health, but recently an in-depth physical revealed a condition that’s going to require abdominal surgery. My doctor tells me this type of surgery is very routine and will, in all likelihood, completely clear up my condition.
Her postoperative instructions prevent me from lifting more than 10 pounds for six weeks. After that I can return to normal activity levels. However, I expect the FAA’s Aerospace Medical Certification branch will require quite a bit more time and more follow-up testing prior to restoring my medical. I’m guessing that process might take as long as six months.
This should help explain my question. Since I won’t be able to fly for an extended period, what do you recommend I do to preserve my airplane for the next six months? It is hangared.
—Tummyache Tom
A: Dear Tom,
Bummer about the need for surgery—but sometimes even humans require an extensive annual.
It’s good that you have your Cherokee in a hangar. Although hangaring does cost money, there’s nothing that will do more to preserve the quality of your airplane. It’s my opinion that just about the only real action you need to take right away is what’s called “pickling” the engine.
Both Lycoming and Continental publish Service Bulletins and Service Information Letters describing the actions required to prevent engine deterioration during periods of inactivity. The applicable Lycoming publication is Service Letter L180B. This bulletin defines an inactive aircraft as one that isn’t operated for a period of more than 30 days.
The Lycoming recommendation consists of draining the engine oil and replacing it with a preservative mixture. The preservative mixture consists of a mix of one part of corrosion preservative fluid and three parts aircraft mineral oil. This is the same mix found in AeroShell Fluid 2F and Phillips 66 Anti-Rust 20W-50 oil. Both of these brands are readily available from popular aviation parts houses.
After adding the preservative oil, the Lycoming letter recommends running the engine until normal operating temperatures are reached; preferred oil temp is 180 degrees F. Lycoming recommends draining the preservative oil—but both of the two oils listed can be used for a short period of time (10 hours or less) during and following the aircraft return to service.
Lycoming also recommends heating a small amount of the preservative oil (two fluid ounces per cylinder) to approximately 200 degrees F before spraying two ounces into each cylinder while turning the propeller through five revolutions.
Finally, one spark plug in each cylinder should be replaced with a dehydrator spark plug, and all openings to the engine (exhaust, crankcase breather, and carburetor or fuel injection air inlet) should be closed off with tape and a plastic bag containing desiccant.
Inspect the desiccant regularly to check to determine if it needs changing or drying out. Dry desiccant is bright blue; a pink color indicates it needs to be changed or dried out. The most common desiccant is silica gel. Pink desiccant can be dried out in a conventional oven by spreading out the material in an oven-safe pan and heating it to 250 degrees F for approximately 1.5 hours. You’ll know it’s fully dry when it’s again bright blue.
I checked with some engine shops and got varying opinions about how much corrosion protection these actions would provide over an extended (one year-plus) period of time. One foolproof engine preservation method mentioned was to install blank-off plates after removing the accessories, and fill the engine completely full of inexpensive motor oil.
Other tasks that will help preserve your airplane are applying a good coat of carnauba car wax to the windshield, filling the fuel tanks with fresh fuel, and, if possible, removing the tires. But these last three are optional. The most important is preserving the engine.
Happy flying,
Steve
Q: Hi Steve,
I fly a PA-28R-180 Arrow II. I’ve owned it for a long time and it used to be very easy for me to head out to the airport and enjoy a couple hours of flying, mainly because Avgas was so cheap. I think it was around $1.20 a gallon in the early 1980s. Then around 1990, the price dropped to less than a dollar a gallon. I was flying all over the place.
Now it’s over $4.00 a gallon and with my fixed income, I’m looking for ways to reduce my costs, or operate more efficiently—or share some of the costs.
What do you think of the idea of pulling the power back to, say, 55 percent?
—Old Flyer
A: Dear Old,
I certainly understand how much the cost of flying has escalated over the past couple of decades. I too find myself totaling up the cost of almost every flight nowadays. The days of the $100 burger are long past.
I took a look at the Arrow II power setting table in the Owner’s Manual, and it does list a number of different power settings that will provide a 55 percent power setting. For instance, at 5,000 feet pressure altitude, 55 percent is attainable at 2,100 rpm and 21.7 inches of manifold pressure (MP) and at 2,400 rpm and 19.3 inches of MP. Lycoming says that any combination of rpm and MP listed in the Piper charts has been flight tested and approved by both the airframe and powerplant engineers.
As far as deciding which combination works best, Lycoming recommends that each combination of rpm and MP be tested for at least five minutes in smooth still air; the combination that results in the least vibration and the lowest noise levels is the preferred combination.
One more piece of the puzzle that you’ll have to figure into flying at lower power settings: your Arrow will cruise when leaned for economy cruise at least 10 knots slower at 55 percent power than it will at 65 percent power.
Some pilots are under the impression that the MP number should never be greater than the rpm/100 number—in other words, that a power setting of 24 inches MP and 2,100 rpm is harmful to the engine.
That thought needs to be discarded now and forever. Running an Avgas-fueled piston engine “oversquare” (when the MP number is greater than the rpm/100 number) is the preferred way. At slower rpms, the propeller is more efficient and quieter, and at higher MPs the ring to cylinder wall seal is more efficient.
Experiment to find out the power setting that works best for you and your flying. After looking over all the variables, you may find the fuel savings garnered while flying at 55 percent power aren’t worth the loss in speed across the ground, especially if you fly to travel.
Happy flying.
Know your FAR/AIM and check with your mechanic before starting any work.
Steve Ells has been an A&P/IA for 39 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as associate editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Paso Robles, Calif. with his wife Audrey. Send questions and comments to editor@www.piperflyer.com.
RESOURCES
“Engine Preservation for Active and Stored Aircraft”
Lycoming Service Letter No. L180B, published Nov. 13, 2001
www.piperflyer.com/
AeroShell Fluid 2F
https://www.shell.com/global/products-services/solutions-for-businesses/aviation/aeroshell/products/fluids-and-preservatives/2f.html
Phillips 66 Aviation Anti-Rust Oil 20W-50
https://www.phillips66aviation.com/products/antirust_oil_20-50.aspx
