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Maintenance & Technical (165)

Restoration on a Budget: A New/Used Autopilot

Restoration on a Budget: A New/Used Autopilot

I recently managed to take care of one of the items on my wish list, and I did so at a significant discount.

April 2015-

Back in the day, all I wanted was a new Nav/Com, a wing leveler and an engine that didn’t leak too much oil.
Times changed, and my wish list got more expensive. Now it includes a new GPS-based flight management system (FMS), a new autopilot with all kinds of GPS-enabled capabilities—and an engine that doesn’t leak too much oil. (Along with a new paint job!)

I’ve recently managed to take care of one of the items on my wish list: the replacement of a 37-year-old autopilot with something modern. I’d been using a Century III autopilot with altitude hold and Nav/GPS/localizer tracking—no glideslope coupler, no altitude preselect, no beep when the autopilot kicked offline. (On the other hand, when the Century III worked, it was amazing.)
After flying with Century III and Century 41 autopilots for over 40 years, I had grown accustomed to this quiet, invisible and completely reliable equipment flying the plane for long hours at a time.

The need for a reliable autopilot
For those of you that have never flown a Seneca, here’s my one-sentence summary of its flying attributes. It is highly stable, but it can be a bear to fly.

That is, it’ll fly for long periods of time on-heading and on-altitude with the autopilot offline, my hands in my lap and my feet flat on the floor. After a while it will slowly drift left or right, up or down. The drift is so slow that if I’m not careful, I’ll bust my altitude and have to account for my poor flying habits. Every few minutes you have to roll left or right a bit, or pitch up or down a bit.

Q&A: Stabilator Tip and Wingtip Replacement Options, Control Cable Assembly Inspection and Replacement

Q&A: Stabilator Tip and Wingtip Replacement Options, Control Cable Assembly Inspection and Replacement

April 2015-

Q: Hi Steve,
I fly a Piper Cherokee 180 and want to install new stabilator tips and wingtips. Mine are original, and they are in pretty sorry shape.

My mechanic said he could remove them and use off-the-shelf fiberglass products to fix them up, but I don’t think that’s what I want.

I’ve seen other Cherokees with tips that are much better looking than the originals. What are my options for new tips?

—Bad Tip Terry

A: Dear Terry,
A long time ago Piper manufactured wingtips out of aluminum, but later changed to using ABS plastic because it was lightweight, easy to manufacture and economical. And as long as it was well protected by good paint, ABS was pretty durable.

However, I wouldn’t recommend attempting a repair of your original ABS plastic wingtips or stabilizer tips with fiberglass. ABS plastic is a much more flexible product; although fiberglass can be repaired, in this case you’d be mixing a rigid product (fiberglass) with a flexible product (ABS). It’s better to use ABS repair products on ABS tips, and ABS repair components are available from various vendors.

Restoration on a Budget: Door Handle Replacement

Restoration on a Budget: Door Handle Replacement

Door Handle Replacement

Cost: Two-door Piper: less than $100
One-door Piper: Less than $50
Complexity: Simple
Time Required: 15 minutes
Applicable Airplanes: PA-28, -32, -34

Before I take my Seneca in for painting, the exterior needs to be in great condition.

This quick and inexpensive project was a piece of cake to accomplish.

March 2015-

I’m always restoring something on my Seneca II and talking about my experiences on the member forum at PiperFlyer.org. I just celebrated my 10th anniversary of owning this airplane and I’m slowly moving toward getting the airplane painted... but I’m rapidly running out of things to replace!
With the high cost of painting an aircraft I find myself doing all of these little projects first, but I’m finding that fewer people want to fly with me because—unfortunately and incorrectly—they equate airworthiness with paint condition. (Even more unfortunately, paint is about $15,000!) At least some of the other parts of my Seneca are new and shiny.
I did visit a paint shop once, where I received some sound advice. Before I take my PA-34 in for painting, I was reminded that the exterior of the plane better be as good as it can be. If the exterior isn’t in great condition, paint isn’t going to help it much. It would be like putting lipstick on a pig, as the saying goes.

Q&A: Spare Key Blanks, Cabin and Baggage Door Lock Replacement, Maintaining a High Performance Single and Solutions for Hard Starting

Q&A: Spare Key Blanks, Cabin and Baggage Door Lock Replacement, Maintaining a High Performance Single and Solutions for Hard Starting

March 2015-

Q: Hi Steve,
I want to make another set of keys for my Piper PA-30 Twin Comanche. I’ve decided to let my son buy a half share in the airplane and he needs keys.
My experience is that buying anything from Piper is expensive—and besides, this airplane is 48 years old. Do you think Piper still stocks key blanks for my airplane?
What do you recommend?

—Keyless Ken

Not Just a Bunch of Hot Air: Exhaust system inspection tips

Not Just a Bunch of Hot Air: Exhaust system inspection tips

Three defects can show up on exhaust systems; read on to find out exactly what they are and how to find them.

February 2015-

Light airplane exhaust systems don’t garner as much attention as a carburetor or induction air filter, yet these systems must be maintained as attentively as any other engine accessory, if not more so. That prosaic exhaust system is the only fire control system under your cowling.
Exhaust systems rarely rate a second thought. Why? Because unless your airplane is turbocharged or turbo-normalized, the exhaust system doesn’t have any moving parts—it just sits there.
Light aircraft exhaust systems are designed to collect hot exhaust gases from each cylinder and route these gases safely out of the engine compartment. Systems in single-engine airplanes also flow the gases through rudimentary metal heat exchangers that radiate heat to outside air that’s used to provide cabin and carburetor heat.
It’s common to mistakenly believe that these heat exchangers are mufflers because they look like an automobile muffler. Some heat exchangers include internal baffles designed to slow the exhaust gases in order to increase the amount of heat transfer. Twin-engine Pipers don’t have these heat exchangers; they utilize Avgas fuel combustion heaters for cabin heat. (For an in-depth look at combustion heaters, refer to the November 2014 issue of Piper Flyer. —Ed.)

Q&A: All about Comanches and wing stall strips on a pre-1989 Archer II

Q&A: All about Comanches and wing stall strips on a pre-1989 Archer II

February 2015-

Q: Hi Steve,
I just bought a sweet little Piper Comanche. I can’t believe how much the prices have fallen in the last five years. This one is a 1964 Comanche 250. I am planning to upgrade the avionics and get a new paint job and figured that all into my budget when I penciled out the numbers. So far I couldn’t be happier.
Since I’ve just entered the Comanche world, I need some guidance on how to keep my airplane alive and healthy. What are the big maintenance items? What parts do I need to buy now and stockpile for the day the parts pipeline dries up? Where can I learn all there is to learn?

—Comanche Newbie

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Flight Review Anxiety

February, 2015-

General aviation (GA) pilots enjoy a level of flexibility and freedom unrivaled by their aeronautical contemporaries. Airline, corporate, and military flight operations are all strictly regulated, and each uses a significant degree of internal oversight to ensure compliance. GA has relatively few of these regulatory encumbrances. As a result, safety depends heavily upon the development and maintenance of each individual pilot's basic skills, systems
knowledge, and aeronautical decision-making skills.

The purpose of the flight review required by Title 14 of the Code of Federal Regulations (14 CFR) 61.56 is to provide for a regular evaluation of pilot skills and aeronautical knowledge. AC 61-98B states that the flight review is also intended to offer pilots the opportunity to design a personal currency and proficiency program in consultation with a certificated flight instructor (CFI). In effect, the flight review is the aeronautical equivalent of a regular medical checkup and ongoing health improvement program. Like a physical exam, a flight review may have certain "standard" features (e.g., review of specific regulations and maneuvers). However, just as the physician should tailor the exam and follow-up to the individual's characteristics and needs, the CFI should tailor both the flight review and any follow-up plan for training and proficiency to each pilot's skill, experience, aircraft, and personal flying goals.

To better accomplish these objectives, this guide, intended for use in conjunction with AC 61-98B, offers ideas for conducting an effective flight review. It also provides tools for helping that pilot develop a personalized currency, proficiency, risk management, and "aeronautical health maintenance and improvement" program. A key part of this process is the development of risk management strategies and realistic personal minimums. You can think of these minimums as individual "operations specifications" that can help guide the pilot's decisions and target areas for personal proficiency flying and future training.

Click the link below to download PDF.


Magnetos: Engine Shop Perspective

February 2005

Thirty-two years ago my start in the engine business was as chief pilot test flying, delivering engines, airplanes and customers. Since that was in the sun-drenched wonderland of eastern Long Island at Mattituck, N.Y., I needed a rainy/snowy day job in the shop where I could fill my time between flights and storms. Assignment to the accessory shop was the answer and magnetos became my game.


How To Survive an STC

February 2005-

After receiving several phone calls regarding STCs I was selling and comments about their high costs, I decided to write this article. With the hope it will enlighten the reader about the process of obtaining an STC and aircraft owners about the rationale behind the cost of an STC, I will cover in depth the steps I went through to obtain Multi-STCs.
In the small aircraft category there are four different processes available: Type Certificate, Multi-STC, One Time Only STC, and Field Approval—in this order and difficulty.

Q&A: Replacing a worn starter ring gear, and the proper use of carburetor heat

Q&A: Replacing a worn starter ring gear, and the proper use of carburetor heat

January 2015-

Q: Hi Steve,
I am the proud owner of a 1967 PA-28-235 and I like to do real good preflight inspections, but I sometimes run into something that puzzles me.
At my last preflight I discovered a tooth missing on what looks to me like a flywheel. I think the teeth are engaged by the starter to start the engine. As far as I can tell, the missing tooth hasn't caused any starting problems. It starts just like it always has.
Will the missing tooth cause a problem? What do I have to do to fix it?

—Eagle-Eyed Ed


A: Dear Ed,
Taking the time before each flight to perform a detailed preflight is one of the most important risk-reducing tasks entrusted to a pilot, and many owner's manuals and all POHs include a detailed preflight checklist in a walkaround format. Printing a copy and referring to it during the actual walkaround helps.
The broken tooth you found is one of 149 teeth on the part that's listed as a "gear, starter ring 12/14 pitch" in the Lycoming parts manual. (Mechanics just call it a ring gear.) The part number is 72566. The same gear is used on a wide range of Lycoming engines including -290, -320, -360, -435, -540, and -541 series engines.
Lycoming Service Instruction (SI) 1141A dated May 9, 2014 outlines the procedures for removing the old ring gear and installing a new one. (This recent instruction supersedes SI 1141 dated Oct. 20, 1967. —Ed.)
The first step it to inspect the holes in the aluminum support assembly to see if they are worn or out of round. If the support assembly is airworthy, the ring gear is removed by grinding. (Do not grind into the support assembly.) With only a thin ring of steel holding the ring gear, simply insert a chisel into the gap and tap it to break the gear loose.
Heat the new ring gear to approximately 450 degrees in an oven or with a torch. The heated gear will have expanded so much that it will be easy to drop it into position on the support assembly. Make sure that the chamfered edge of the teeth is on the aft side (generator or alternator pulley side) of the support assembly.
Inspect to make sure it's securely seated against the flange of the support assembly—there's no indexing needed. As the ring gear cools, it will shrink to provide a tight fit.

Happy flying.

Q: Hi Steve,
The latest discussion around the home 'drome coffee shop revolves around the use—or misuse—of carburetor heat.
Like most of the gang, when I first started flying I was taught that carb heat is an all-or-nothing affair. Either put it fully on, or leave it fully off. As I've gained experience, and flown with more experienced pilots and instructors, the "all-or-nothing" rule has become muddied.
One of the locals insists that airplanes with Continental engines are very prone to induction (carburetor) icing, therefore pilots in Continental powered airplanes have to be extra careful to watch for loss of rpm when flying an airplane with a fixed pitch prop—or loss of manifold pressure (MP) when flying an airplane with a constant speed prop.
The same guy says that Lycoming engines are rarely subject to carburetor ice since the carburetor is bolted onto the oil sump which heats the carburetor throat, thus preventing icing.
Finally, a new guy has shown up and he says it's okay to fly around with partial carburetor heat. He claims that increasing the temperature of the air flowing through the carburetor causes better atomization of the fuel. This, he claims, results in a more even distribution of the fuel/air mixture to the cylinders.
Would you like to weigh in on this?

—Het-Up Hal
A: Dear Hal,
I'd be happy to. The statement about carburetor icing in Continental versus Lycoming engines is semi-correct, and for exactly the reasons you cited. But all pilots need to memorize this fact: any carburetor-equipped engine—of any make—will, under the right conditions, form carburetor ice.
Factors such as vaporization of fuel and the expansion of air as it passes through the carburetor throat (i.e., the Venturi effect) can cause the inlet air to drop as much as 70 degrees F. This is why carburetor icing occurs when outside air temperature (OAT) is well above freezing.
Since Continental engine carburetors aren't warmed by heat from the engine oil sump, carb ice occurs in Continentals at a higher ambient temperature than it does in Lycoming engines. Warmer air can hold more moisture than cooler air, and the potential for severe carburetor icing is greater in Continental engines.
If carburetor ice is suspected, full carburetor heat should be applied. If there's no ice present, the warm, less dense air ducted into the carburetor air box by the carburetor heat system will cause a slight loss of power. It's normal to hear and feel a change in the engine.
FAA certification rules mandate that carburetor heat systems must be sufficient to produce a temperature change of 90 degrees F. According to one engine expert, full application of carb heat may reduce power by as much as 13 percent.
If ice is present in the carburetor throat, the application of carb heat will result in engine roughness and a loss of rpm or MP before power is restored. It's a little disconcerting to feel the engine getting rougher when the carb heat is applied, but that's normal.
The application of partial carburetor heat during cruise flight is mentioned and approved by Lycoming Service Instruction 1148C, provided the aircraft has a carburetor temperature gauge. The Service Instruction specifies that aircraft with a carburetor temperature gauge may be used to keep the mixture temperature above the freezing point of water (32 degrees F).
A number of companies including Electronics International, JP Instruments, Mid-Continent Instruments and Avionics, UMA Instruments and Westach manufacture carburetor temperature gauges. Many of these products are available through Chief Aircraft and Aircraft Spruce as well as directly from the manufacturers.
Applying partial heat in accordance with the Lycoming SI eliminates carburetor throat ice. It also has two other effects. The first effect of using carb heat in cruise is slightly less power. Secondly, the warmer air causes the fuel metered by the carburetor to atomize more completely. This creates a fuel/air mixture that flows better and is more evenly distributed to the individual cylinders.
You can test the "better distribution with heat" effect if your airplane has a carburetor temperature gauge and EGT probes installed in each cylinder. In cruise (below 75 percent power if Lycoming-powered; below 65 percent power if Continental-powered) and after leaning for cruise, wait five minutes for the engine to stabilize, then slowly start applying carburetor heat.
Add enough heat to get a reading of 50 degrees F on the carburetor temperature gauge. You will need to lean the mixture slightly due to the less dense air (same amount of fuel), but you should see the EGT spread lessen as the fuel/air mixture is more evenly distributed. Theoretically, the engine should run smoother. It's up to you whether you adopt this practice.
Don't forget that whenever carburetor heat is applied, the engine inlet filter is bypassed and any airborne dirt will enter the engine.

Happy flying.

Know your FAR/AIM and check with your mechanic before starting any work.

Steve Ells has been an A&P/IA for 43 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 .

Ring gear replacement
"Replacement of Worn Starter Ring Gears"
Lycoming Service Instruction 1141A

Carburetor heat
"Use of Carburetor Heat Control"
Lycoming Service Instruction 1148C

Carburetor temperature gauges
Electronics International Inc.

JP Instruments

Mid-Continent Instrument Co. Inc.

UMA Inc.

Westberg Manufacturing Inc. (Westach)


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