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Engine Mounts Explained

Engine Mounts Explained

The engine mount represents a crucial link between your engine and airframe, and it should be treated as a mission-critical accessory. STEVE ELLS visited Loree Air, an FAA-certified repair station, for insight into the engine mount repair process.

I have found no evidence that my engine mount—that web of steel tubes that supports the engine and nosegear on my 1960 Piper PA-24 Comanche airframe—had ever been overhauled or recertified.

It seems a bit hard to believe. After all, it’s been bolted onto my airplane for 57 years. You’d think one mechanic or owner along the way would question whether the mount had suffered the ravages of time or had any issues. But like I said, when I started digging in the logs, I found no maintenance record entry that showed me it had ever received specific attention.

I recently discovered a cracked tube, and when I scrubbed it with a wire brush, I found a gaping hole—the tube had rusted through from the inside. I removed the welded steel mount in order to send it in for repair and recertification. 

As it turned out, the tube with the rusted spot was only one of seven tubes that had to be replaced. I had no idea the mount was in such bad shape!

What engine mounts are made of

SAE grade 4130 steel, also known as chrome-moly, is a through-hardened chromium-molybdenum steel alloy that is used in the light airplane industry where light, strong tubing is needed. It’s strong for its weight, easy to work, easy to weld and provides a good cost-to-strength ratio. 

Chrome-moly steel is available from aviation parts suppliers such as PFA supporters Acorn Welding, Aircraft Spruce and Airparts Inc. Wicks Aircraft also supplies this tubing. (Another PFA supporter, Wilco Inc., carries SAE 4130 in sheets. —Ed.)

The seven tubes that were replaced on my engine mount consisted of one 1/2-inch diameter tube, two 5/8-inch diameter tubes and four 3/4-inch diameter tubes. 

Chrome-moly tubing is purchased by specifying the outside diameter (OD) in 1/16-inch steps and the wall thickness. The wall thickness of the 5/8-inch OD tubes in my engine mount is 0.035 inch, which is close to the thickness of a credit card. The wall thickness of the 1/2-inch OD tubes is 0.049 inch, which is approximately the thickness of a CD. 

The 1/2-inch and 5/8-inch tubes sell for $4.35 per foot at Aircraft Spruce; the 3/4-inch tube is $3.35 per foot. 

I needed 4 feet of 5/8-inch tube and 68 inches of 3/4-inch tube to repair my mount before it could be recertified as airworthy. The materials cost was less than $50 at retail prices. 

A chrome-moly steel mount is a sweet piece of engineering. My refurbished engine mount (as delivered to me) weighs 15 pounds, 11 ounces; yet it is strong enough to support the Comanche’s Lycoming O-360 engine (258 pounds), a Hartzell two-bladed propeller (51 pounds) and support and endure the shocks suffered by my retractable nosegear.

The refurbished engine mount of the author’s 1960 PA-24 Comanche weighs 15 pounds, 11 ounces. It is strong enough to support a 258-pound Lycoming O-360 engine and a 51-pound Hartzell two-bladed propeller, and will also endure the shocks suffered by the retractable nosegear.
Removing and sending the mount out for repairs

After I found the hole in the lower right tube, I removed the engine and nose landing gear assembly. Removing parts, like the demolition phase of a room remodel, always goes quickly. In this case, I knew I needed to label and sort the parts and engine accessories because it was going to be almost two months before I was going to be reinstalling the engine and nosegear. 

One trick I’ve used for years when removing an engine or other assembly is to take photos of everything before picking up the wrenches. When I first heard of this photo trick, shops were using Polaroid cameras. Today, a cell phone and/or tablet is more than sufficient. 

One of the decisions that I pored over was where to send the mount for repair and recertification. I wanted an FAA-certified repair station that had the capabilities to repair and recertify my mount. My favorite internet search engine turned up four options. They were, in alphabetical order: Acorn Welding Ltd., Aero Fabricators (a division of Wag-Aero), Aerospace Welding Minneapolis and Loree Air Inc. and I have no doubt that there are others. 

I also searched for a used, serviceable mount. I found one on the East Coast and negotiated what I thought was a good price—but after learning that it would take more than $500 to ship it to me on the West Coast, the deal fell through.

Obviously, the cost of shipping a mount, as well as how to ship a mount, must be considered. Companies told me that the most common method is to bolt the mount to a piece of stout plywood, then either build a wooden or cardboard box around it for shipping by UPS or FedEx; or to bolt the mount to a pallet and ship it as truck freight. Since the repair facility has no control over handling after it leaves their possession, it’s critical to create a shipping container that protects the mount during shipping. 

PFA supporter Aero Fabricators quoted me $1,400, which included changing up to 10 tubes, and told me the turnaround time was two to three weeks. Aerospace Welding quoted a price of more than $2,500. 

Another PFA supporter, Acorn Welding, was unable to estimate their cost over the phone, but Paul Gyrko, head of sales, took the time to answer my questions and explain the full process when I called for information. 

Steve Loree Jr. at Loree Air told me that the cost to inspect, repair, normalize, paint and certify my mount would be $1,700 if it only required cleaning, inspecting, repainting and certification; and a maximum of $2,100 if work was needed. Loree also warned me the company had a five-week backlog. 

Given that Loree Air was only 278 road miles away from my home base—while the other three were all over 1,800 road miles away—and that I had good reports from friends that had used them, I decided to use the five-week window for other tasks and took my mount to Loree.

After another PA-24 owner offered to fly me up to Placerville to drop off the mount, I packed my sad old mount in the back of my buddy’s Comanche and flew it up to the Placerville, California airport (KPVF) where I left it with Nicole, who runs the office. 

Ready for pickup

Steve Jr. called on a Tuesday in late June to tell me that after cleaning and sandblasting all the paint off my mount, a thorough inspection revealed some surface damage to the exterior of a couple of tubes; bends in two tubes; and more tubes that showed evidence of internal rust. 

I asked him if it was OK if I drove to the shop once my mount was finished; I wanted to hang around and ask a lot of questions about mount damage and repairs. I figured this was an opportunity to pick up some hints and tips that a mechanic in the field could use to determine if a welded steel tube engine mount or landing gear support structure was airworthy. He said that would be fine.

Five weeks later I got the call; the repaired mount was ready. 

I arrived at Loree Air at 10:30 Monday morning. I met the entire staff: Steve Sr., Steve Jr. and Nicole (who is married to Steve Jr.). I was also sniffed up and down by Layla, the small four-legged office assistant and guard dog.

 

 Left to Right, Top to Bottom: Steve Sr.; Steve Jr.; Nicole; Layla (the hairy one).

Steve Sr. attained his welding certification at the San Diego shipyards and went to Sacramento City College for his A&P education at the suggestion of his flight instructor. He gained a wide range of reciprocating engine skills at the Sacramento Sky Ranch before spending 15 years working at the Sacramento Citation Center and at Aircraft Conversion Technology in Lincoln, California, with owner Bill Piper. 

Seeing the need for a certified aircraft welding shop in California and wishing to steer his own path, Steve Sr. opened Loree Air in 1992 in a small shop in the Swansboro Country neighborhood in the foothills east of Sacramento, near Placerville.

In 2011, Steve Jr. joined his father in the business. They decided that since the shop needed to grow in order to support two families, it was time to expand. To do so, Steve Jr. said, “I think we need a website,” but Steve Sr. wondered if it was necessary. Word-of-mouth advertising had been effective and the company had all the work it could handle. But Steve Sr. yielded, and today you can visit Loree Air online at LoreeAir.com. 

After consistent growth—thanks to the website—the Steves decided to move the company to a small warehouse and shop in Diamond Springs, another community near Placerville. 

With the help of many friends and family members, they planned and built a shop to fit the company’s needs. 

There had to be a large sandblast booth to clean mounts. There had to be a paint booth. There had to be an area for grinding and smoothing metal. The shop needed an area where mounts were put into jigs for alignment and buildup. A screened area was required for welding. A separate office and customer reception area were part of the plan as well.

There are also two lofts for storing parts and ready-to-ship mounts and nose strut welded tube support structures. 

While I had to take my mount to Loree Air to get in line due to the five-week backlog, the company does stock repaired and certified mounts for some popular aircraft. 

Problem areas

The Steves spent some time describing why my engine mount rusted out and passed on tips for determining if a welded steel engine mount is airworthy.

According to Steve Sr., “Piper mounts were not corrosion-proofed in the 1960s and early ‘70s.” He is referring to a practice of coating the inside of welded steel tube assemblies with a corrosion inhibitor. 

In the early days of aviation, linseed oil was used to inhibit corrosion. When I asked what else works, he replied that either LPS 2 or 3 heavy-duty lubricant works well and is readily available. 

The other Piper mount problem was the build sequence, which left small gaps at each firewall fitting around the bolt bushing boss. The gaps are small, but can allow moisture to get to the inside of the tubes. Loree has developed a build process that seals the mounts. 

Steve Sr. also pointed out that many Piper PA-28 Cherokee engine mount assemblies allow moisture to get into the tubes at the four engine support reinforcements, where the rubber vibration isolators—often called Lord mounts—are installed, because the two halves of the reinforcements are not sealed. This is also addressed when Loree repairs a PA-28 engine mount. 

Inspection tips and tricks

I asked the Steves for tips to help field mechanics determine if the welded steel mounts they inspect are airworthy. They said one test is to use an automatic center punch to put a small dent in the end of a tube that is believed to be unaffected by internal corrosion and compare that to the dent when the punch is used on the part of the tube that is suspected to be corroded. Usually this means comparing the dent at the highest part of the tube near a weld cluster to a dent in the lowest part of the tube. 

Any difference in the depths of the two dents is clear evidence the lower end of the tube has been weakened by internal corrosion.

Dents are repaired during the Loree Air rework. According to Steve Loree, the circular slot around the bolt hole is how moisture—a cornerstone of the rust process—enters the tubing in the mount. Loree seals this slot during rework.

While at the Loree shop, I also saw tubes that were dented during installation and removal by sloppy tool handling, and tubes that had been scratched or scored by abrasion.

Since these tubes are so thin, what may at first appear to be negligible damage usually needs attention. “Our standard for repair is 10 percent of the tube thickness,” said Loree.

One thing Loree was adamant about is avoiding the use of plastic tie-wraps (i.e., zip ties) to secure anything to a welded steel mount. He has seen it again and again: plastic tie-wraps will wear a welded steel mount tube faster than a pilot heads to a restroom after a cross-country flight. It takes longer to install properly-sized Adel clamps, but they are the only clamping device Loree wants used on an engine mount. 

You and your mount

I was surprised to hear Steve Sr. say that in all his years repairing mounts he had seen very few engine mounts pass through his shop that needed no repairs. 

I was also surprised when my mount needed seven tubes replaced. 

Then I saw pictures of the inside of those tubes. They were all rusted to one degree or another. I believe good fortune was smiling on me when I found the crack that lead me to remove my mount to send it for repair. 

Rust was clearly present in seven of the author’s engine mount tubes. They were all replaced by Loree Air.

Based on what I learned and saw, I recommend that owners send their engine mounts to a certified mount repair shop to get inspected, repaired-as-necessary and recertified whenever their engine is removed for overhaul.

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 >>>>>

SAE 4130 STEEL TUBING – PFA SUPPORTERS
Acorn Welding

Aircraft Spruce and Specialty Co.
aircraftspruce.com/catalog/mepages/4130tubing_un1.php

Airparts Inc.

SAE 4130 STEEL TUBING – OTHER SUPPLIERS

Wicks Aircraft and Motorsports
wicksaircraft.com/tubing.html

SAE 4130 STEEL SHEETS – PFA SUPPORTER

Wilco Inc.

ENGINE MOUNT REPAIR – PFA SUPPORTERS
Acorn Welding Ltd.
acornwelding.com/products/engine-mounts.html

Aero Fabricators
(a division of Wag-Aero)
wagaero.com/repair-station/engine-mount-repair.html

OTHER ENGINE MOUNT REPAIR FACILITIES
Aerospace Welding Minneapolis
awi-ami.com

Loree Air Inc.
loreeair.com

ANTI-CORROSION SPRAY
ITW Pro Brands
lpslabs.com 

Read more...
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
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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

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PA-24 Comanche Buyer's Guide

PA-24 Comanche Buyer's Guide

What you need to know about buying and owning a Piper Comanche.

When some pilots think of Piper, they think of the Cherokee line and its derivatives which are still in production today. The Piper Comanche is a different design and preceded the first Cherokee by three years.

While Cherokees were designed and built in Vero Beach, Fla., the Comanche is a Lock Haven, Penn. aircraft. Lock Haven was Piper’s original factory. The Comanche was the first all-sheet-metal, semi-monocoque aircraft that Piper designed and produced.

Piper opened the Vero Beach facility to devise and assemble a line of aircraft that were less expensive to produce than the Comanche. A combination of design choices for ease of manufacture and the lower labor rates in Florida led to the Cherokees eclipsing the Comanches. Comanche production ceased in 1972.

Strong airframe, good performance

The Comanche is said to have about 50 percent more parts than does the Cherokee. I believe it.

It clearly took more manpower to build the parts and assemble the aircraft. One result was a particularly strong airframe.

The Comanche was designed to withstand 7.5 gs rather than the 5.7 gs required by FAA regulations.1 Though the aircraft was only officially certified in the normal category for 5.7 gs, the reserve of strength allowed for bigger engines and increased gross weight as the design was refined over the years.

So why is there any interest in an aircraft that has not been produced in almost half a century? The answer is in the specifications.

When a pilot starts to look for an honest four-place traveling aircraft with good speed and range, they usually find the performance numbers of a Comanche attractive. I developed this guide for those who are not immediately repelled by the idea of an older airplane and are intrigued by the performance.

The Piper Comanche is a classic. It’s one of the nicest planes to fly and own—and also one of the hardest to try and find a truly nice one for sale.

Comanches tend to be loved to death. By that I mean that owners hang on to them long after they should have sold them. So many have been sitting idle for too long because the owner keeps hoping to get that medical back and just can’t bear to sell the plane that he or she has had for decades.

Designed to compete

Piper designed the Comanche to compete with the Bonanza. Arguably Beech won that competition, but Comanche owners are every bit as dedicated to them as Bonanza drivers are dedicated to the various models.

The “Bo” generally wins on fit and finish. They are both nice flying, with the “Bo” generally faster down low, and the Comanche often faster in the low teens where the Comanche wing starts to strut its stuff.

The “Bo” is nicer landing, but the Comanche is cheaper to buy and maintain. I have well over a thousand hours in various Bonanza models, and prefer the Comanche—especially when I am paying the bills to keep the plane running.

The cabin is roomy and comfortable, and the wing is optimized for operation at higher altitudes which increases their efficiency and range.

In its 14-year production run, Piper made numerous changes to the Comanches. Initially the Comanche was certified and produced as a 180 hp version powered by a Lycoming O-360-A1A. The first 100-plus aircraft produced were all Comanche 180s.

Comanche 180


The 180 had a maximum gross weight of 2,550 pounds, and today typically have a useful load of between 900 and 950 pounds. (Keep in mind that these specifications are approximations based on my experience.) Comanches are often very highly modified with speed kits, etc., so each aircraft really has to be treated as its own design.

The Comanche 180 demonstrates the soundness of the aerodynamic design. A stock 180 in good condition will typically outrun an Arrow, carrying the same load on 20 less horsepower—a 75 percent cruise of 140-plus ktas on 10 gph or so.

Applying all the possible speed mods has brought the cruise speed of a Comanche 180 to over 150 ktas and close to that of a Cirrus SR20, the latter of which has the benefit of composite construction and computer-aided design.

The Comanche 180 carries 60 gallons of fuel, of which 56 gallons is usable. This gives a four-hour endurance with a very comfortable reserve. It is also the nicest handling and nicest landing of all of the Comanches.

There is nothing from the outside that identifies a Comanche 180, save for the insignia. They have the identical appearance to the 250 and the early 260s. The hallmark of the early Comanches is the two windows on the side. The cowling is even the same for the four-cylinder 180s as it is for the six-cylinder 250s/260s.

Comanche 250

In the spring of 1958, Piper received its certification for the Comanche 250 and started making deliveries. The 250s had a maximum gross weight of 2,800 pounds. Stock airplanes commonly has useful loads around 1,100 pounds.

They are generally equipped with an O-540-A1A5 engine. The 250s would cruise at around 155 ktas at 75 percent power and burn about 14 gph at optimal altitude.

Like all Comanches, if you take it up higher, you’ll be rewarded with big fuel flow decreases with only small decreases in speed. Cruising above 10,000 feet will only cost a few knots in speed, but the fuel flow will drop to 12 gph or less. Keep climbing and the efficiency just keeps improving.

With 56 gallons of useable fuel, 500- to 600-mile flights with reserve is easily possible. Tiptanks are an STC’d option that increases the fuel capacity by 30 gallons and in most models, increases the gross weight.

The 180/250 came originally with the instrument cluster toward the center of the panel and the avionics on the left side. This was apparently so that the copilot would have easy access to the flight instruments. This configuration was fairly common in early aircraft, but was going out of fashion even in the 1950s.

Early Comanches had manual flaps and an arm that serves as the emergency gear extension lever that sticks up from the floor and lays down when the gear is raised. More than one unwary pilot has lost an iPad to that arm by putting the device on the floor in front of and between the front seats.

In 1961, Piper made significant improvements. The company increased the fuel capacity to 90 gallons with 86 useable by adding two optional 15-gallon auxiliary tanks outboard of the mains. This was only available for the 250 Comanches. That much fuel gives the Comanches a range of 900 to 1,000 nm. With tiptanks as well, 116 gallons of usable fuel could make a 10-hour flight a reality.

Also for the 1961 model year, toe brakes were added to the pilot side in addition to the handbrake, and the panel got a center stack configuration for the radios. To make sure that the additional fuel did not eat up too much of the cabin capacity, Piper increased the gross weight to 2,900 pounds.

For the 1962 year, Piper replaced the manual flaps that mostly just pivoted downward with Fowler-type flaps that moved back and down, thereby increasing the wing area. That in turn reduced the stall speed and takeoff roll.

At some point in 1962 or 1963, apparently with the 1963 model year2, fuel injection became an option.

By the end of 1963, Piper quit producing the 180 hp model except upon special order, and then stopped the 180 altogether in 1964.

Comanche 400, Comanche 260

Big changes were forthcoming in 1964. Piper introduced the 400 hp version of the Comanche, and by mid-year, started producing the 1965 model year—the first of the 260 hp Comanches.

The 400 Comanche was the brainchild of Howard “Pug” Piper who wanted a Comanche that would cruise in the high teens and low flight levels without the complication of turbocharging. The 400 has an eight-cylinder IO-720 engine that indeed will climb up and cruise in the flight levels.

The aircraft came out in 1964 powered by an IO-720-A1A engine with 400 hp. The fuel capacity is 130 gallons. Cruise speeds range from 190 ktas or so at 75 percent burning around 22 to 23 gph, to 160 to 170 ktas at higher altitudes burning 15 to 16 gph. (Again, speeds depend a lot on what speed modifications are installed.) The gross weight is 3,600 pounds, with a typical useful load of 1,350 to 1,400 pounds.

Piper made 147 of the 400s—all in the 1964 model year—and they are still prized as a niche aircraft. They climb like a homesick angel, but the engine is expensive to overhaul, running $60,000 to $70,000 for a quality rebuild.

The 1965 model was the first of the 260 Comanches which were delivered from late summer 1964 through 1965. With a new prop and a fuel injected engine (which was now redlined at 2,700 rpm instead of 2,575 rpm), an additional 10 hp was gained.

Piper also improved the aerodynamics by changing to a single-fork main landing gear which tucked the strut and the brake caliper into the wheel well, reducing drag.

Another desirable improvement was the installation of dual exhaust. These removed the muffler from the rear of the engine which had a tendency to overheat the cabin through the firewall. The new dual exhaust was also less prone to exhaust stack cracking which was, and still is, all too common, especially on the right side stack of the 250 Comanches.

Comanche 260B

Arguably the largest cosmetic and functional change in the Comanche took place with the 1966 B model Comanches. The fuselage was altered to make it possible to install a fifth and sixth seat in the baggage compartment. To accomplish this, Piper removed the back bench seat and replaced it with individual seats.

The baggage compartment seats are essentially three- to four-inch pads that attach to an anchor and sit on the floor. A padded back also attached and rested against the back bulkhead. Two little foot wells were placed under the rear/middle to accommodate these passengers’ feet. Piper was also required to move the baggage door to the left side of the fuselage so that it could act as an emergency exit, and added an additional window.

The B models and later are easily identified by the three windows down each side as opposed to the two windows for earlier Comanches. This made the fuselage appear longer, but in fact that is an optical illusion. The fuselage deimensions for all Comanches are the same. The overall length can change due to differences in prop and spinner. The B model was produced from 1966 through 1968.

Comanche 260C

For the model year 1969, Piper made a number of significant refinements. The main improvement was a much more modern-looking instrument panel in the standard six-pack configuration. Gone were the old toggle switches and the overall look that seemed to come out of an Ernie Gann novel. Lighted rocker switches and a power lever quadrant replaced the push-pull engine controls and made the Comanche C a more modern-looking plane.

Also gone was the classic Comanche “smiley face” cowling. In its place was the “shark’s nose” cowling with an extended prop hub. Cowl flaps were added in an effort to reduce cooling drag. The gross weight was increased 100 pounds to 3,200 pounds, but the majority of that was eaten up with the changes.

With the Comanche C, Piper also made factory turbocharging an option. The PA-24-260TC was actually the fastest of the Comanches when it was taken up into the flight levels. The manual wastegate controlled the manifold pressure once the aircraft could no longer maintain the desired power setting. These are the rarest of the Comanches with only around two dozen produced.

Turbocharging does provide significant altitude capability, but it comes at the expense of low altitude performance. The back pressure in the system caused by the manual wastegate means a reduction of about an inch in manifold pressure on takeoff. The turbos also come at a financial cost, as they increase the maintenance expenses and the engine overhaul expenses.

Knowledge sharing

Successful ownership and enjoyment of a Comanche generally requires the owner to take a role in the maintenance of the aircraft and take responsibility to obtain training from a knowledgeable instructor.

There are few shops in the country that truly know how to care for a Comanche and know what the current availability and lowest cost options are for parts. Most shops don’t see more than a few Comanches every decade, and their design is significantly different from the Cherokees and their derivatives.

When a known Comanche-savvy shop is not readily available, a partnership between a local IA and the owner can bridge the gap to help keep a Comanche in good airworthy condition.

There are online Comanche communities, such as the Airworthy Comanche Forum and the International Comanche Society, plus training programs by the Comanche Flyer Foundation.

One or more of these in combination with resources from your Piper Flyer Association can provide an owner with ready access to the information necessary to get any Comanche back in the air expeditiously.

Pre-purchase considerations

When purchasing a Comanche, it is important to have a pre-purchase inspection by someone who actually knows Comanches, not just one who claims to know them based on having done a few annual inspections over the years. There are a couple of areas where any old mechanic will not do.

The landing gear is the chief area where lax maintenance can cause a significant problem—and a significant expense—for a new owner. Failure to ensure that the landing gear has been properly maintained can be a $10,000 mistake if the entire system needs to be restored.

The Comanche landing gear is robust and perfectly safe, but it is not idiotproof. It does not have mechanical down-locks, which means the system needs to be rigged properly to keep the drag links overcenter so that no bounce or side load will allow the retraction of gear.

Because mechanics often do not have a good feel for how much play in a landing gear system is too much, Piper came up with a detailed inspection with Service Letter No. 782, and the FAA mandated that inspection to be done every 1,000 hours with Airworthiness Directive (AD) 77-13-21, paragraph (a).

That same AD also mandates the replacement of the landing gear bungees which help unload the landing gear transmission as the gear comes up. Replacement is every 500 hours or three years, whichever comes first.

AD 77-13-21 creates one of the first gotchas for potential owners, because it mandates two actions at different intervals. Mechanics rarely miss the paragraph (b) requirement to replace the bungees, but not so the 1,000-hour inspection which calls for partial disassembly of the landing gear and checking the bolts and bushings for excessive wear. This wear inspection is often overlooked—or even occasionally signed off without having been performed.

An experienced Comanche mechanic can tell in less than an hour what the condition of the landing gear is, but that is knowledge that comes from having performed a number of the 1,000-hour inspections to learn the before-and-after condition.

AD 2012-17-06 on the stabilator torque tube horn requires a 500-hour repetitive dye penetrant inspection for each horn with more than 1,000 hours time in service. The inspection takes about six hours. There is an STC to permanently comply with that AD by installing a new horn.

The STC’d horn runs close to $1,000 and will take eight to 10 hours to install, and then is subject to a 100-hour visual inspection that requires no disassembly.

Piper Service Bulletin No. 1189 provides more information, but fortunately, the AD is not as strict as Piper’s Service Bulletin. Thanks to some dedicated Comanche owners, one of whom is an aeronautical engineer, the FAA was convinced that longer inspection intervals were appropriate.

The two ADs detailed above are only a few of the ADs that may apply to a particular Comanche. In my experience, maintenance logs may state an AD has been permanently complied with, when it was only partially complied with—and repetitive inspections are, in fact, required. Research and verify the status of every single AD on the airframe before buying.

 

The Comanche is a great traveling machine. It hauls a good load, quickly, over a long distance. Comanches have been prominent over the years in racing circles, and numerous Comanches and Twin Comanches have circled the globe.

If are looking for a airplane that can haul a family, a Comanche is worth a look. It is frequently the last plane someone buys—and it could be the last plane you ever need to buy.

 
A&P/IA Kristin Winter has been an airport rat for almost four decades. She holds an ATP-SE/ME rating and is a CFIAIM, AGI, IGI. She has over 8,000 hours and owns and operates a 1969 C model Twinkie affectionately known as Maggie. Send questions or comments to .

 March 2017

1Author Ted Durosko is quoting Piper Chief Design Engineer Fred Strickland in “Check Pilot Report: The Piper Comanche.” Flying, Feb. 1958.

 2Piper followed the same protocol as automobile manufacturers who usually started the next model year in the fall of the previous year.

 

RESOURCES >>>>>

Owner information and assistance

Piper Flyer Association
Airworthy Comanche Forum

 

Safety and training

Comanche Flyer Foundation

cffpilot.com

 

Maintenance documents

AD 77-13-21, “Prevent Landing Gear Collapse”

rgl.faa.gov

 

Piper Service Letter No. 782A
“Landing Gear Manual Extension System Inspection and Nose Gear Down Lock Spring Installation”

 

Piper Service Bulletin No. 1189

“Stabilator Horn Assembly Inspection”

 

AD 2012-17-06

“Stabilator Horn Assembly Inspection and Replacement”

 

All three documents are available at PiperFlyer.org/forums under “Magazine Extras”

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