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Comanche Stabilator Horn Inspection

Comanche Stabilator Horn Inspection

Piper PA-24 Comanches are subject to AD 2012-17-06, which requires inspection of the stabilator horn for cracks and corrosion. A&P/IA Steve Ells describes proper procedures for removal, inspection and reinstallation.

June 22, 2011, the FAA issued a Notice of Proposed Rulemaking (NPRM) that asked all concerned parties to comment on a proposed AD. The proposed AD would mandate an initial inspection of the stabilator horn assembly for cracks and corrosion on Piper PA-24, PA-24-250 and PA-24-260 Comanche single-engine airplanes. After the initial inspection, replacement or continued inspection would be required.

Since I am the happy owner of a 1960 PA-24, I followed this closely.

Comanche owners contributed many comments seeking to relieve and/or clarify the requirements of the original NPRM. Some suggested that the FAA make changes due to mitigating factors such as the wall thickness of the stabilator torque tube, nut-tightening torque values on the bolts that secure the horn to the torque tube and other concerns.

The NPRM was written because cracks had been found in several stabilator horns. The submitted comments were well-regarded by the FAA and raised valid points. After changes and updates, AD 2012-17-06 was issued Aug. 22, 2012. 

The review of the initial proposed rule, the comments, names of the commenters and the FAA’s responses to the commenters can be read in full on the FAA’s website. (A link to the page is in Resources. —Ed.)

AD 2012-17-06 and Piper Service Bulletin No. 1189 (April 29, 2010)

A little over five years ago, in early January 2013, I pulled the stabilator horn assembly on my Comanche and drove it over to Johnston Aircraft in Tulare, California, for the initial inspection. In my opinion, Johnston ranks right up there with three other Comanche shops in the country. 

I watched as Charles Gazarek at Johnston showed me how to remove the aluminum horn and then perform the inspection steps mandated by the AD. No cracks were found in the horn. 

This horn is an aluminum part that connects the stabilator torque tube to the cables that control aircraft pitch through the horn assembly. The horn assembly consists of the horn, a tube (Piper Part No. 22880-00) and a balance weight (Part No. 23175-00). The torque tube is secured to the aft bulkhead of the fuselage by four bolts that hold bearing block assemblies in place. The torque tube rotates in two large sealed bearings. The stabilators slide over the torque tube and are secured by two bolts on each side. 

The left bearing block and torque tube. 

The AD calls for an initial inspection, and then repetitive inspections every five years or 500 hours TIS, whichever comes sooner. The horn must be removed from the aircraft and inspected for cracks by dye penetrant or other means. 

The timeline for complying with the initial inspection requirement of the AD varies based on the age and origin of the horn. Refer to the AD for details, but the short version is that if a horn has not been inspected since the AD was published in 2012, it is likely due for an initial inspection.

The repetitive inspection can be terminated by installation of what’s known as the Aussie horn, which is a stronger replacement horn that was developed in Australia and is approved for installation by a STC. (For more on this alternative, see the sidebar on Page 28. —Ed.)

Pull those tailfeathers

Removing my left and right stabilators was easy. (The author, Steve Ells, is an A&P/IA. Repair work such as this must be performed or supervised by an authorized mechanic. —Ed.) I removed the two close-tolerance (AN175) corrosion-resistant bolts on each side that I installed to comply with a previous AD (AD 74-13-03 R1) and slid both stabilators off the torque tube. They slid right off since I had cleaned and polished the tubes and applied a light coat of LPS-2 prior to reinstallation five years ago.

The stabilator control cables attach to the torque tube assembly at the forward end of the tube at the balance weight. I cut the safety wire and slacked both cables, then removed the bolt that connected the cable terminations. 

Then I removed the two bolts that secured the balance weight on the tube, and slid the weight off.

Next, I removed the upper and lower tailcone fairings and the tail navigation light bulb socket after disconnecting the trim tab actuating arm assembly (Part No. 20828-00) and electrical wiring to get access to remove the torque tube.

After removing the two bolts of the yoke assembly that supported the trim tab drum assembly to the blocks that hold the torque tube bearings and lowering the yoke and drum assemblies, I removed the four bolts securing the bearing blocks and pulled the torque tube assembly out from the aft bulkhead. 

The bearings, bearing blocks, torque tube and horn have been removed from the aft bulkhead. 
Preparing for inspection

After removing the assembly from the airframe, I slid the two bearings and blocks off each end of the torque tube, then slid the aluminum horn off the tube for inspection.

        

These two photos are from Piper Service Bulletin No. 1189, Fig. 1. The black lines on the aluminum horn assembly indicate the areas to be inspected.

 

None of this was difficult. Because the tube had been previously cleaned, the bearings slid off easily. I checked the bearings for ease of rotation. They were smooth and free. The left and right bearings had been replaced in the past. Newer bearings have a white Teflon seal; original bearings have a red seal. 

After I heated the horn for a few minutes with my electric heat gun (an electric hair dryer will work), it slid off the tube.

I stripped off the “rattle-can” primer paint I had applied after the last inspection with off-the-shelf paint stripper. 

Piper Service Bulletin No. 1189 shows two horns that had cracked. In each case, the cracks were through the bolt holes either at the front or aft side of the horn.

I looked closely at the horn with a very bright light but couldn’t see any evidence of cracking. The next step was the dye penetrant inspection.

It took me just over three man-hours to get to this point. 

Dye pen(etrant)

The AD requires an inspection in accordance with the instructions given in Piper Service Bulletin No. 1189. According to the bulletin, cracks start at the inner surface, so there’s no need to remove exterior paint from the horn to complete the inspection. Simply clean the inside of the horn with isopropyl alcohol prior to performing the dye penetrant inspection.

A dye pen inspection consists of cleaning the surface, then applying a coating of the penetrant, which is a very viscous red liquid. Leave the dye in place for a few minutes so it can penetrate any surface cracks, then clean the part completely. The dye pen kit I used consisted of a can of spray-on cleaner, a can of spray-on dye and a can of spray-on developer. 

As you can see by the photo, I sprayed a generous coat of dye onto my horn. After a few minutes, I sprayed the provided cleaner on a clean rag and wiped off all the dye. 

After drying the horn, I sprayed on an even coating of the developer. The dye is ruby red, while the developer looks a lot like spray-on talcum powder. The developer coated the surfaces of the horn.

I was looking to see if I saw red lines in the white developer which would indicate cracks. Luckily, there was no evidence of cracking. So, I cleaned the horn and started reassembling the torque tube assembly.

The stabilator horn, liberally coated with dye. 
Reassembly

I again smoothed and cleaned the outer surfaces of the torque tube with a Scotch-Brite™ pad before applying a light coating of LPS-2. Then I slid the horn into position. 

The most critical reassembly task was applying the correct torque to the two bolts that hold the horn in position on the torque tube.

I then slid the left and right bearings and blocks onto the torque tube. There was no need to remove the part called the stabilator torque collar. This collar, which appears black in the photos on bottom of Page 30, is part of the stabilator travel adjustment system. 

The service manual calls for a dimension of 8.620 inches between the left and right bearing block. If that dimension is not attained, shims are installed to achieve it. Mine checked OK.

The stabilator horn assembly is mounted to the rear bulkhead with four 5/16-inch diameter bolts, two in each bearing block. The nuts are torqued to the standard torque (there’s a standard torque table in the service manual) for 5/16-inch bolts loaded in tension. That torque value is 100 to 140 inch-pounds.

Once the bearing block bolts were torqued, I moved the trim tab drum yoke into position and installed and safetied those bolts. Then I slid the left and right stabilators onto the torque tube and secured and torqued those bolts. Checking stabilator balance and travel

After the tail was reassembled but before I reconnected the pitch system control cables, I followed the procedure in Chapter 4 of the Piper PA-24 Service Manual to check the stabilator balance. First, I leveled my Comanche. A stabilator is in balance when it can be moved to any position throughout full travel and not move once placed in any position. Mine was balanced.

I then connected the control cables and positioned and tensioned the up and down cables to provide the mandated control wheel travel and the stabilator travel. 

I rechecked my procedures and steps, then when satisfied that all was as specified, I reinstalled the tailcone fairings after reconnecting the power and ground wires to the tail navigation lights. 

In all, the removal, inspection, reinstallation and rigging and travel checks took very close to a full day of work, or 8 man-hours. (For reference, AD 2012-07-16 estimates the entire inspection process, including removal and replacement, takes 12 man-hours. —Ed.)

After completion of the steps in the AD, I entered a maintenance record (logbook) entry that is signed and reads similar to this: “October 29, 2018: Airframe total time 3,255. Complied with AD 2012-17-06, dated Oct. 22, 2012 (g) (2) (i) and (5) and Piper Service Bulletin 1189 Instructions 1 through 6. No cracks found. AD is next due October 29, 2023 and 3,755 aircraft total time.”

Now my stabilator horn is airworthy for another 500 hours or five years. 

No cracks were seen after applying the white talcum-like developer. 
Not too tight; it’s a shear load

Paragraph 5 in the “Inspection/Replacement” section of AD 2012-17-06 mandates that the bolts that go through the horn and torque tube be torqued to 120 to 145 inch-pounds or 10 to 14.5 foot-pounds. It doesn’t sound like much, especially for bolts that may at first seem to hold the tail together!

There are two reasons for what seems to be a low torque value. The first reason is because overtorqueing the nuts has been determined to be the cause of the cracking. There’s no need to apply a hefty torque since the nuts don’t need to do any more than prevent the bolts from falling out. 

The second reason is because of the bolt loading. This bolt-nut combination is loaded in shear, not tension. The bolts transfer the up and down motion of the horn/tube and balance weight into rotary motion of the torque tube. 

To apply the correct amount of torque, the friction drag of the nut’s locking element first must be determined. Common aircraft-quality self-locking nuts “lock” in position due to either a fiber insert in one end of the nut or by a slight out-of-round section of a steel locknut. 

How many inch-pounds of turning force does it take to overcome that locking component? The easiest way to determine the friction drag is with a deflecting-beam torque wrench. The following is the equation as published in the AD: 

The stated torque value of 120–145 in.-lbs. includes friction drag from the nut’s locking element, which is assumed to be 60 in.-lbs. The installation torque can be adjusted according to the actual, measured friction drag. For example, if the friction-drag torque is measured to be 40 in.-lbs. (20 in.-lbs. less than the assumed value of 60 in.-lbs.), then the installation torque will be adjusted to be 100–125 in.-lbs. of torque.

The steps are to first determine the friction drag of the nut’s locking element in inch-pounds and then adjust as necessary to get the final torque.

A reliable torque wrench is crucial for reinstallation of bolts on the stabilator horn.

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

Steve Ells has been an A&P/IA for 44 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 Templeton, California, with his wife Audrey. Send questions and comments to .

RESOURCES >>>>>

AIRCRAFT MAINTENANCE, “AUSSIE” HORN
Johnston Aircraft Service Inc.
AD 2012-17-06
Federal Aviation Administration
PIPER SERVICE BULLETIN NO. 1189
Piper Flyer’s Magazine Extras 
PDF available at PiperFlyer.org/forum
Q&A: Adding Toe Brakes to a Cherokee, Hand Controls for Wheelchair Aviators

Q&A: Adding Toe Brakes to a Cherokee, Hand Controls for Wheelchair Aviators

Q: Hi Steve,

I just bought a 1968 PA-28-180 Cherokee 180 B. So far, it’s been wonderful, but there’s one thing that I haven’t yet gotten used to. I trained in a newer Cherokee and it had toe brakes. My airplane just has a brake handle that I pull on to apply both main brakes at the same time. 

How can this be a good idea? Every airplane I flew in my training had toe brakes and whenever I wanted to turn sharply, I used the brake to sharpen my turn. I can’t do that in my “new” Cherokee and I am hoping you can point out how I can install toe brakes in my airplane. 

 

A: When I looked in the PA-28 and PA-28R Parts Catalog (Piper Part No. 753-582) for the PA-28-180, the way I read it, toe brakes were available on the left side on the PA-28-180 from Serial No. 28-1 up through 28-7305611.

The serial number range for your airplane, the Cherokee 180 B, includes serial numbers from No. 28-671 through 28-1760.

Toe brakes were an option from the factory. All Cherokees were equipped with hand brakes, but only the ones that were ordered with toe brakes also got the factory-installed toe brakes. 

There is no STC to install toe brakes on Cherokees. I have heard of owners who went to an aircraft salvage yard for the entire toe brake package—pedals, crossbar supports, links, firewall reinforcements, master cylinders and other parts that were available—and had these parts installed. Since all the parts are listed in the parts manual for the Cherokee 180, this is certainly doable. 

Some mechanics will say this change is a minor alteration for two reasons. First, Piper already approved the installation of the toe brake system at the factory and all the parts are Piper-produced. Second, it is not listed in the list of major alterations in Appendix A of Part 43 of the regulations. Minor alterations require only a logbook entry for a return to service.

Despite those facts, these days most shops will seek FAA approval in the form of a field approval sign off on a Form 337 (Major Repair and Alteration). This is despite the fact it’s becoming increasingly difficult to get a maintenance inspector at a local Flight Standards District Office (FSDO) to sign off a 337.

For what it’s worth, I did see a set of Cherokee toe brake pedals on eBay today. It lacked the master cylinders and the necessary firewall reinforcements, so you’d have to source those parts elsewhere.

My 1960 Piper PA-24 Comanche is the first airplane I’ve ever owned that does not have toe brakes. At first, I was skeptical too. 

I soon learned that I didn’t miss the toe brakes at all. Part of the reason is that I used to lock up and flat-spot tires when I had toe brakes. That got expensive. Yes, I had to learn to live with the turning radius of my Comanche, but now that I know about it, the larger turning radius hasn’t been a headache. 

Many owners with the handbrake controls, myself included, strongly suggest that you live with your hand-actuated brake system for a few months before you make your final decision. It’s a good system.

Happy flying,

Steve

A Piper handbrake, like this one installed in Steve’s PA-24 Comanche, is simple to operate. The brake system applies equal braking pressure to the main wheels. Just pull the handle to slow down.


Q: Hi Steve,

I expect my mechanic can answer this, but I haven’t asked him yet. I have a Piper PA-28 Cherokee that I’ve owned for years. This airplane has been a central part of our family trips and vacations. 

My son was severely hurt last year in a motocross accident and has lost the use of his legs. He gets around fine in his wheelchair and has expressed an interest in flying. I have heard something about wheelchair pilots, but don’t have any details. 

Is there a way to equip my Cherokee so that my son can take flying lessons?

Flying Dad


A: Hi Dad,

I’m sorry to hear about your son’s accident.

Yes, theoretically there’s a way to equip your Cherokee with controls that will enable your son to safely fly your airplane. But unless you can find a used set of hand controls to install in your airplane, it’s going to be tough.

Unfortunately, the two companies that developed hand controls for disabled pilots and had them approved through what’s called a Supplemental Type Certificate (STC) are no longer producing the hardware and paperwork for installation of the controls.

STC SA1741WE approves the installation of hand controls in PA-28-140, -150, -160, -180, -235 and PA-28R-180 and R-200 aircraft. This modification is sometimes known as the “Blackwood hand control” after the originator. The STC is presently owned by Mike Smith, but is not in production.

During my research, I spoke with Justin Meaders at International Wheelchair Aviators. Meaders is a pilot and uses a wheelchair. He was able to update me on the state of STCs for equipping Pipers for pilots who require hand controls to fly. 

Meaders told me he is working to get the FAA to recognize the Blackwood hand control for Pipers as a medical device that would not require an STC for installation.

Vision Air of Australia has Australian approval for a hand controls system for Cherokees, but it hasn’t been approved for use in the United States.

There is a similar STC for Cessna hand controls known as the Union control. The STC is in suspension now, but has been purchased by Linwood Nooe of Operation Prop in Brandon, Mississippi. 

I asked Nooe if he knew of a source for the hand controls. He told me that his nonprofit organization offers flights and flight training to men and women that can’t operate foot controls, and that people donate used controls to him from time to time. 

Nooe also invited anyone who needs hand controls to fly to come to his facility in Mississippi  for both introductory flights and flight training. (Nooe’s contact information is in Resources. —Ed.) 

You can view videos of hand-controlled flights using the Vision Air controls and Union control on the website of the United Kingdom-based nonprofit Freedom in the Air. (See link in Resources. —Ed.)

Best wishes on helping your son fly,

Steve

These diagrams, provided by Linwood Nooe, show the Union hand control.
It is similar to the Blackwood control used on Piper Cherokees. 

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

Steve Ells has been an A&P/IA for 44 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 Templeton, California, with his wife Audrey. Send questions and comments to .

RESOURCES >>>>>

FAR PART 43, APPENDIX A
Federal Aviation Administration

BLACKWOOD HAND CONTROL STC FOR PIPER PA-28
Federal Aviation Administraton
rgl.faa.gov/Regulatory_and_Guidance_Library/rgSTC.nsf/WebSearchDefault?SearchView&Query=SA1741WE

INFORMATION FOR WHEELCHAIR AVIATORS
Able Flight
ableflight.org

Freedom in the Air (flight videos)
freedomintheair.org/hand-controls

International Wheelchair Aviators
wheelchairaviators.org

Operation Prop (Linwood Nooe)
operationprop.com

Vision Air
mirageair.com.au/vision.shtml

Rules For Owner-Performed Maintenance

Rules For Owner-Performed Maintenance

As an aircraft owner and pilot, you can legally perform some maintenance tasks, but you must adhere to strict guidelines when doing so. STEVE ELLS walks us through packing wheel bearings, while highlighting what’s important to stay legal.

As most readers of Piper Flyer know by now, all aircraft maintenance tasks must be overseen or performed by an appropriately-rated person. For maintenance tasks, this means an A&P mechanic—or a technician, as some like to be called these days—is frequently both performing and signing off on the work. This mechanic must (by regulation) have up-to-date versions of the appropriate manuals, bulletins, tools and equipment necessary to complete the tasks. 

However, there are also a number of maintenance tasks that owners may legally perform. These are termed preventive maintenance (PM) tasks. There’s a long list of them in Appendix A of FAR 43. 

What is considered preventive maintenance?

Appendix A is titled, “Major Alterations, Major Repairs and Preventive Maintenance.” Paragraph (c) lists preventive maintenance tasks. Type “Appendix A of Part 43” into your favorite search engine (or find the link in Resources on Page 33. —Ed.).

There is a surprisingly long list of tasks allowed. For instance, owners are permitted to remove and replace batteries, replace bulbs, reflectors and lenses of position and landing lights, and replace prefabricated fuel lines. 

They can also remove and replace panel-mounted communications and navigations receivers and update databases in panel-mounted avionics such as GPS navigators. 

Great news, right? It is, especially if a pilot has the time and a place to do these tasks. The potential for saving money exists, but much more important is the satisfaction to be gleaned from learning how to take care of your own airplane. (For further reading, see the sidebar on Page 32. —Ed.)

Are you permitted to perform preventive maintenance tasks?

FAR 43.3 paragraph (g) says that “…the holder of a pilot certificate issued under Part 61 may perform PM on any aircraft owned and operated by that pilot which is not used under Part 121, 129 or 135 of this chapter.” 

So, according to this section, if the owner and pilot is not using his airplane for hire, whether on a scheduled service, an on-demand service or as a foreign carrier operating for hire in the U.S., he/she can perform PM. 

But there’s a catch. It’s in 43.13. It’s titled “Performance Rules (General).”
43.13 Performance Rules (General)

The following three points—from paragraphs (a) and (b) of the performance rules—have been abbreviated to simplify the important points the maintenance performance rules for owners. 

1. Each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance shall use the methods, techniques, and practices prescribed in the current manufacturer’s maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques and practices acceptable to the Administrator.

2. He [or she] shall use the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices. 

3. Each person maintaining or altering, or performing preventive maintenance, shall do that work in such a manner and use materials of such a quality, that the condition of the aircraft, airframe, engine, propeller, or appliance worked on will be at least equal to its original or properly altered condition (with regard to aerodynamic function, structural strength, resistance to vibration and deterioration, and other qualities affecting airworthiness).

In other words, if you’re going to do PM, you must follow the procedures in the manuals. It’s as simple as that. 

It’s important at the outset to understand that airplane maintenance, while seeming to be like automobile or other gas engine maintenance in that it must be done right, is different in a very important way. In airplane maintenance, there is a published protocol for every operation, even the tightening of a nut or bolt. 

Another peculiar-to-aircraft trait is this: the strength versus weight equation must always be kept at the forefront of every operation and decision. In other words, if you believe that more is better, whether it be the size of a bolt or the amount of torque, you’re going to do more harm than good. 

Gathering the manuals and bulletins to meet the requirements of the FARs is much easier and less expensive than it used to be. The secret is the internet. Manufacturers have come to realize that making their manuals and bulletins available at no cost or consolidating a double-shelf full of manuals onto a CD is a sound idea, simply because access to manuals makes it much easier for maintenance shops (especially smaller shops) to access the precise methods and techniques the manufacturer has developed for maintaining its product. 

So, step one for owners that want to start working on their airplanes is to have or have access to manuals, and either have the tools or be able to manufacture the tools required to properly perform each maintenance task. 

Let’s look at an example of why manuals are important.

Greasing wheel bearings: a “simple” preventive maintenance task

Greasing the wheel bearings on an airplane may seem simple. At its most basic, it can be described in the following steps: First, jack up the airplane or axle enough to get the tire off the ground, then remove the axle nut and pull the wheel/tire assembly off the axle. Next, remove each bearing, clean it and the bearing race, inspect for damage or corrosion, replace if necessary, pack with grease and reinstall. Finally, reinstall the tire/wheel assembly, tighten the axle nut and lower the tire to the ground. 

Not so fast. There’s more to it. In fact, there’s quite a bit more.

To remove the tire/wheel assembly (TWA), the brake assembly must be partially disassembled. This disassembly requires the removal of two or four bolts to release what’s called the brake back plate(s). The TWA can be removed only after the back plate(s) have been removed.

Assuming the airplane has been jacked up far enough to lift the TWA, a large cotter pin must be removed prior to removing the axle nut. Then, the TWA can be pulled from the axle.

There is an inner and an outer bearing. Does a Piper parts book refer to these bearings? No. Piper parts books don’t show an exploded view of the wheels. Piper parts manuals only provide the Cleveland part number for the wheels on its single-engine airplanes.

That means you also need a Cleveland manual for dimensions, wear limits and bolt torque specs when greasing the wheel bearings on your Piper single. 

Here’s another thing to know that is hard to find in any manual: Bearings and races are matched pairs. Don’t take the bearing assembly you removed from the race on the valve stem side of the TWA and install it in the race in the non-valve stem side of the TWA.

What grease to use?

The 2009 Piper Lance service manual suggests the use of Aeroshell 22 grease and Mobil EP 2 grease (also marketed at Mobilux™ EP 2), which is a lithium-based grease. 

Cleveland, the manufacturer of brakes and wheels used on Piper singles, suggests the use of Mobil SHC™ 100 grease. 

Bearing removal, cleaning and greasing

After the TWA has been removed, the bearings are removed. This usually requires the removal of a snap ring, a washer, a felt grease seal and another washer. 

Bearings are then cleaned with Stoddard solvent, applied by either an air-powered solvent sprayer or a brush. Air can be used to blow the grease out, but never spin a bearing by directing compressed air perpendicular to the rollers. 

Directing a stream of air across—not between—the rollers in roller bearings is dangerous because the bearing cage is designed only to maintain the spacing between the rollers. It’s not strong enough to contain the rollers when they rotate at a high rate of speed; in other words, directing air across when bearings can result in fast-moving projectiles.

After the bearing is clean and dry, look for corrosion and/or pitting. If found, replace the bearing and matching race.

Bearings are repacked by putting a gob of clean grease in the palm of either hand and forcing the grease up into the bearing. Press the bearing down into the grease until the bearing comes into contact with your palm. Repeat this procedure until grease appears at the top of the bearing cage.

You can also buy a bearing packer and use it to pack the bearing. Look up “wheel bearing packing tool” on your favorite search engine. YouTube also has wheel bearing packing videos. (See Resources for an additional article that discusses wheel bearing service. —Ed.)

The last step is to look at the grease seals. For decades, Cleveland, the manufacturer of most GA wheels and brakes, has used felt pads to seal against sand and fine dirt. These seals are inexpensive and work well. 

Recently, Cleveland has replaced the felt pads with molded rubber grease seals. These may be used in place of the felt seals.

Putting it all back together

The newly-greased bearings are reinstalled in the side of the wheel which they came from. Slide the TWA onto the axle. If it doesn’t slide all the way on, you’ve got the large steel washers on each side of the felt seal in wrong. Swap the washers around until the TWA slides all the way onto the axle.

Thread the axle nut onto the axle. 

How tight should it be? I couldn’t find definitive information on how tight the axle nut should be. Field experience suggests to tighten the nut up well to seat the bearings, then loosen it until you can feel a slight movement of the wheel in and out on the axle, then snug it back down until the TWA spins without resistance and no in-out movement is felt.

Now, to reassemble the brake. Two or four bolts were removed so the back plate could be removed to free the brake disc from the inner and outer brake pads. 

Whenever I have a TWA off the axle, I clean up the brake guide pins with a Scotch-Brite pad. I also clean the guide pin holes in the torque plate. These guide pins must slide in and out to allow the brake to self-adjust as the brake pads wear. 

The devil is in the details

The last step is often missed as it’s not in the Piper manual. It’s found in the Cleveland Wheels and Brakes Component Maintenance Manual, Appendix A titled, “Wear Limits and Torque Values.” This manual, and all of the Cleveland wheel and brake manuals, are available for free on the Cleveland website. Start by downloading the Technician’s Service Guide. (See link in Resources. —Ed.)

Piper parts books don’t have all of the information needed to service a tire and wheel assembly. The Technician’s Service Guide from Cleveland Wheels & Brakes can be an essential companion for owner-performed maintenance.
Oftentimes, similar-looking parts call for different torque values. It is crucial to use the correct value for your part. 

This critical step in reassembly is applying the proper torque to the two or four back plate tie bolts. Overtorqueing the bolts can deform the brake housing. 

The proper torque on almost every Piper single engine brake is 75 to 90 inch-pounds (6.25 to 8.5 foot-pounds). That ain’t much. It doesn’t need to be much since these bolts aren’t in a compression application. They are loaded in shear, and as long as these bolts are snugged down to the proper torque, that’s sufficient. 

Sign off your work

The good news is that owners can legally do a lot of work on their airplanes. However, as mentioned, there are catches. Catch No. 1 is that you must own or have access to the manuals. Catch No. 2 is that you must enter the work you performed in the aircraft records in a manner that’s acceptable to the Administrator. That’s FAA talk for the head of the agency. 

The requirements for these entries are listed in FAR 43.9. It says if you perform PM, you shall make an entry in the maintenance records containing the following information:

1. A description of the work performed.

2. The date the work was completed.

3. The name of the person performing the work.

4. If the work was performed satisfactorily, the name, certificate number and signature of the person performing the work. The signature constitutes an approval for return to service only for the work performed. 

(This is a summary of FAR 43.9. Please refer to Resources for a link to the complete text. —Ed.)

Notice that the regulations do not require the entry to include the aircraft total time or tach time, but it’s extremely helpful to include that information. 

An example1 of an entry for the work described above would read:

Month/day/year. “Greased left and right main landing gear wheels in accordance with information in the Piper (model number) service manual and the Cleveland Wheel and Brake Component Maintenance Manual, Appendix A, paragraph A3.”

Signed: Joe Pilot Cert # 1245654

The point of this article is to make sure owners understand the freedom and the limitations that are part of owner-performed PM. Go ahead and do it, but make sure you do it right; by the book. 

1For more about complete and detailed logbook entries, see “Deciphering Logbooks: Pre-purchase Maintenance Record Review” by Kristin Winter in the December 2017 issue. 

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

Steve Ells has been an A&P/IA for 44 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 Templeton, California, with his wife Audrey. Send questions and comments to .

RESOURCES >>>>>

FURTHER READING

Part 43.3, Part 43.9, Part 43.13, Appendix A to Part 43

Electronic Code of Federal Regulations

Technician’s Service Guide AWBTSG0001-1

Cleveland Wheels & Brakes– PFA supporter

Component Maintenance Manual AWBCMM0001-12

Cleveland Wheels & Brakes– PFA supporter
“Wheel Bearing Service: Why and How” by Jacqueline Shipe 
Piper Flyer, July 2016 

 

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