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Q&A: Damage to a Comanche airbox coupling, primer lines for a Lycoming engine, and a noisy gear extension

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Q: Hi Steve,

One of the other Comanche owners stopped by as I was working on the engine of my 1960 Comanche 180 and asked if I knew where he could get one of the black accordion-style flexible ducts that goes between the carburetor airbox and the cowling.

He said that his had a hole in it and he was looking for a replacement; he also asked me about patching the hole with silicone bathtub caulk. I told him I thought he could probably get a new duct at Webco.

How do these ducts get damaged? Where can I get one? And should I get one now in case my Comanche needs one in the future?

—Comanche Man      

 

A: Hi Comanche,

The duct you’re referring to is called a “coupling-carburetor air filter” and the part number is 16559-00. Piper has this duct listed at $1,189. Fortunately, Webco sells an approved replacement—it’s W16559-00—for around $250. I spoke to someone at the company yesterday and they said that they’re getting a new stock of these in soon.

As an A&P myself, I never want to see one of these ducts sealed by using a gob of silicone sealer in a hole. I fear that the sealing goop will clog the carburetor when it flakes off the coupling material.

These couplings most often get damaged if they aren’t removed from the airbox when the engine is run up with the cowling off. If the coupling is left on the airbox, the prop blast deflects it downward, stressing—and often tearing—the upper aft corners near the airbox. It only takes a minute to remove.

I would give your airplane’s present coupling a good inspection. If it looks weakened or if the fabric is worn enough that the reinforcing wire between the fabric layers is exposed, then I would go ahead and get a new one. They’re not going to get any cheaper and that coupling is a critical part of your engine inlet air filtering system.

Happy flying.

 

Q: Hi Steve,

I am replacing the engine in my Cherokee PA-28-180 and all the tubes of the primer system are in pretty bad shape.

In addition, it looks like someone decided to build the tubes out of copper. Where do I get the lines I need?

—Primer Paul

A: Dear Paul,

There are two different types of primer lines. The primer lines shown in the Lycoming engine parts manuals are stainless steel. Lycoming part numbers for the stainless steel lines in the four-cylinder Lycoming engines such as the one in your PA-28-180 are LW12098-1-284, LW12098-1-170, LW12098-1-116, and LW12098-1-100. Street costs for these lines average $75 to $120 each. In addition to the lines, a number of clamps, LW 18959-175-25 ($15 each) and “T”s are needed to complete the installation.

However, I also took a look at the Piper Parts Manual for your airplane and it lists different part numbers. The Piper part numbers for your airplane are 63807-00, 63795-00, 63824-00 and 63825-00. These are copper lines, and I recommend that you install the lines called out in the Piper manual as I believe they will better fit your exact airplane.

One way you may be able to lessen the cost is to go to one of the big salvage yards such as Wentworth Aircraft, Air Salvage of Dallas, White Industries, Dawson Aircraft or Fast Aviation Florida and tell them what you need.

All the big salvage yards provide their customers with a short inspection period along with a return-if-not-satisfied, money-back guarantee—so make sure you and your mechanic inspect any parts you buy from a salvage yard as soon as you get them.

The primer lines must be clamped in the manner shown in the Piper parts manual. Lycoming Service Bulletin 342G is titled “Fuel Line Support Clamp Inspection and Installation,” but it does not apply to these primer lines; it applies to stainless steel fuel lines installed on fuel-injected Lycoming engines.

Happy flying.

 

Q: Hi Steve,

I went for a ride in another Comanche on my field last week and I didn’t hear anything when the pilot put the gear up and down. In other words, I noticed it was a lot less noisy than my airplane when the gear is going up and down.

Now that I have heard how quiet his landing gear is, I’m a little worried about mine. Mine always goes up and down, but I can hear it, and I always wear a headset.

What do I need to do to get my system checked out?

—Noisy Gear

A: Dear Noisy,

The Comanche landing gear is extended and retracted by a bidirectional electric motor controlled by the landing gear selector switch. This motor drives a rotating shaft.

As the shaft rotates, a tube moves forward and aft on the shaft. The tube has a quick release sleeve that locks down on a pair of conduits that transmit the motion of the shaft out to the left and right main landing gear retraction mechanisms.

The motor, shaft and tube are disconnected from the conduits and nosegear extension linkage by the quick release sleeve during an emergency extension of the landing gear.

In order to “help” the electric motor, each landing gear (both mains and the nose) is equipped with springs. Each main landing gear is also assisted by a big rubber band called a bungee. These bungees must be changed every 500 flight hours or three years (whichever comes first) in accordance with Piper AD 77-13-21. If the springs are tired and the bungees haven’t been replaced recently, the loads on the motor are higher than if all the parts are in good shape.

The best source for Comanche landing gear advice and help is Matt Kurke at Comanche Gear. Kurke has a wide range of information about maintaining this gear system and can also inspect, service and overhaul landing gear motors and transmissions.

I recently sent in the transmission and motor from my Comanche to Kurke. Like yours, mine was working but also seemed noisy. I was surprised when Kurke report that my transmission and motor were in very good shape.

He did replace a bearing and some other parts and completely serviced the unit for what I considered a very reasonable cost. Kurke also advised me on an easy method for setting the landing gear down limit switches.

Now my landing gear extensions and retractions no longer sound like a load of gravel sliding off a dump truck; in fact, I can no longer hear any noise from the system.

The other maintenance chore required by AD 77-13-21 is a comprehensive inspection of the gear system in accordance with Piper Service Letter 782A at every 1,000 hours time in service.

The Comanche landing gear system is dependable, but does require periodic maintenance by a knowledgeable technician.

Happy flying.

 

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 .

 

RESOURCES

Coupling-carburetor air filter

Webco Aircraft Co.

webcoaircraft.com

 

Primer lines and associated parts

Air Salvage of Dallas, Inc.

asod.com

 

Dawson Aircraft, Inc.ircraftpartsandsalvage.com

 

Fast Aviation/FL Aircraft Salvage & Transport

FastAviationFlorida.com

 

Wentworth Aircraft

wentworthaircraft.com

 

White Industries, Inc.

whiteindustries.com

 

Comanche landing gear

Comanche Gear

ComancheGear.com

 

 

 

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