by Dave Weiman
When it comes to aircraft maintenance and the annual inspection, most aircraft owners are keeping their fingers crossed that the compression will be good in all cylinders, and that they still have some time remaining on their ELT battery. Yes, we look at our propellers, and our mechanics file down minor nicks and paint the backside to prevent glare from shiny metal, but most of us seldom give our props a second thought.
While the manufacturers recommend a certain number of hours and years between overhauls, unlike Part 121 (air carrier) and Part 135 (commuter and on-demand operations), non-commercial operators (Part 91) are not mandated to overhaul their propellers, ever! However, aircraft technicians have a professional obligation to advise their customers when they suspect a problem.
At the recommendation of my aircraft technician about 10 years ago, I had the propeller and governor on my Cessna 182 Skylane overhauled, and it has been functioning well ever since. It was only recently when I began to get some oil sprinkling on my windshield that I realized that something needed attention. It tuned out that the aluminum piston in the hub had worn over time (a common occurrence, I was told). So we had the piston replaced and the propeller resealed. All work was completed at Aircraft Propeller Service LLC in Wheeling, Illinois – a suburb of Chicago – located across the street from Chicago Executive Airport at 290 Larkin Drive. However, had there been any indications of corrosion, they would have overhauled the propeller.
Aircraft Propeller Service has someone on staff who picks up and delivers propellers from airports in a five-state region of the Midwest, so shipping is never an issue. However, as soon as we received word that the propeller was done, I immediately drove down to Wheeling to personally pick up the propeller myself. Morey Airplane Company in Middleton, Wisconsin, removed the propeller and reinstalled it.
Sean O’Keefe is the service and sales manager for Aircraft Propeller Service’s general aviation division and was on hand to greet me upon my arrival and showed me around. A separate building next door is devoted to air carrier propeller sales, maintenance, and administration. This is where Mark Grant, President and CEO of the company, has his office. Aircraft Propeller Service takes up the better part of a city block, but it hasn’t always been that way.
Aircraft Propeller Service was founded in 1940 and originally located at Sky Harbor Airport in Northbrook, Illinois (KOBK). Later the business was moved to Palwaukee Airport (KPWK), now Chicago Executive Airport. John DeJoris and Bill Collazo purchased the business from Ernst Pultz (a submarine crewman during WWII) in 1980, and operated the business from January 1981 through July 2013.
The current facility was built in 1986 and expanded in 1991 to handle the air carrier business. The general aviation division moved to its present location in 2012.
DeJoris and Collazo started with five employees in 1991, and when they sold the business in 2013, the company had 62 employees.
Aircraft Propeller Service sells and services everything from a fixed-pitch propeller for a J-3 Cub to a propeller for an ATR airliner. Aircraft Propeller Service represents Hamilton Sundstrand, McCauley, Hartzell, Aero Technologies, Woodward, and MT Propeller.
O’Keefe says that it is their employees that distinguishes Aircraft Propeller Service from other prop shops. The company is certainly the largest commercial prop shop in the United States, and one of the largest in the world.
“We have been able to grow because of the people we have here,” said O’Keefe. “We have a devoted team of craftsmen and support people.”
Aircraft Propeller Service technicians follow strict original equipment manufacturer (OEM) guidelines.
“When a propeller leaves our shop, we try to blueprint the prop so it operates as smooth as possible, and satisfaction is job number one!”
Aircraft Propeller Service has its own “apprentice” program. The company hires people with a mechanical aptitude, and trains them from the ground up.
“Experienced employees become their mentors and take pride in passing on their knowledge,” said O’Keefe. “It takes years before a technician becomes a licensed repairman. An airframe and powerplant certificate is not required. In fact, we prefer to hire skilled machinists and drill press operators than airframe and powerplant mechanics.”
O’Keefe said that Aircraft Propeller Service will overhaul and service hundreds of propellers and governors each year. For general aviation alone, the company overhauls as many as six propellers a week, not counting governors, and they seldom get a callback. On the airline side of the business, they can complete up to seven blades per day.
O’Keefe joined the company in January 1987, responding to an advertisement in the local newspaper and worked there for two years before going to A&P school. He obtained his airframe and powerplant certificate at North American Institute of Aviation (NAIA) in Conway, South Carolina.
O’Keefe was an aircraft technician in Waukegan, Illinois for four years before returning to work for Aircraft Propeller Service as a salesman.
As an apprentice in the shop, O’Keefe started as a parts cleaner and worked his way up. Like the props that leave his shop, O’Keefe is as polished as they come, and knows the business very well.
O’Keefe’s interest in aviation started with his father – a career Navy man who served on aircraft carriers during World War II as an aircraft ordnance specialist and gunnery mate, then later trained as a ball turret gunner on a TBM Avenger before being wounded. After the war, his dad joined the Naval Reserves and was stationed at Glenview Naval Air Station in Glenview, Illinois.
A Growing Business
O’Keefe says that while the general aviation propeller fleet may be decreasing, Aircraft Propeller Service’s market is increasing as older shops go by the wayside. Aircraft Propeller Service currently serves a large swath of the Midwest, focusing in the northern half of Indiana, and all of Illinois, Wisconsin, Missouri, Iowa and Michigan.
“Service is a big thing,” said O’Keefe. “To be able to pick up and deliver a prop is convenient and important to customers. Shipping companies can destroy a prop, and we would rather not have that happen.”
O’Keefe told me that I wasn’t alone in wanting to pick up my prop and he actually encourages it.
“We like to show off our shop with the nickel tour,” said O’Keefe. “When an aircraft owner shows up, we can tell them face-to-face what we did and why we did it to make their prop like new! And we like to give tours to EAA chapters and others. We have an open-door policy at Aircraft Propeller Service and are proud of it.”
In addition, O’Keefe is a regular speaker at IA (Inspection Authorization) technician renewal clinics around the Midwest.
Proper Propeller Repair & Certification
Step 1: The first thing Aircraft Propeller Service does when your propeller arrives is to “log” the propeller’s identification and serial number and assign it a work number. The work number form is retained on file for future reference and the customer gets a copy for their records. Included in the record is the date and hours on the propeller since new or major overhaul.
Most general aviation propellers can generally be overhauled three times before they need to be replaced. Reversing blades get one or two overhauls and that’s it.
Step 2 is the “tear down.” All components of the propeller are taken apart and broken down in detail. Damaged or worn parts are discarded and all work performed and parts requiring replacement are noted on the work form.
Step 3 is “cleaning” the propeller. All of the components are cleaned using safety solvents to remove grease and dirt. The blades are stripped of paint down to the bare metal. This is an essential preparation for future inspection and finishing, such as special coatings.
Step 4 is the “preliminary inspection.” Non-destructive and dye penetrating methods, such as Magnaflux, Zyglo, and Eddy Currents are used in searching for otherwise undetectable flaws. No pilot ever wants to experience a total propeller failure in flight and this procedure helps to prevent that.
Step 5 is to get “blade measurements.” A machine called an “Aero Scan” measures the prop’s thickness and width at the same time. A propeller can also be measured the old fashion way by hand to determine if there is any material available that can be removed. After the blade measures up as serviceable, it is time to “grind” the propeller. This is where skilled craftsmanship comes into play and is essential in achieving the required shape to meet specifications.
Step 6 is “coating” to put the finishing touches on your propeller’s personality. The final coatings are especially formulated to be non-glare and nick resistant. All steel parts are cadmium plated to be corrosion resistant.
Step 7 is the “assembly.” A library of manuals and specifications, together with a large inventory of parts, ensures proper alignment and assembly. All parts go together with clockwork precision.
Step 8 is “testing.” Aircraft Propeller Service tests every stage of your propeller’s function, short of an engine-mounted run-up. No hydraulic fluids are used. For cleanliness, all operations are performed pneumatically on lathe-type, tabletop, precision equipment.
Step 9 is “balancing.” The balance must be perfect and non-compromising for successful and safe propeller function. All propellers serviced at Aircraft Propeller Service are precision balanced to guarantee a smooth performance at any RPM.
Step 10 is the “final inspection.” Ultimately, Aircraft Propeller Service inspects the propeller to ensure that all stages of assembly are finished and proper. When the inspector is confident that the work performed meets the manufacturer’s and FAA’s standards, the propeller is certified airworthy and returned to service.
NOTE: All steps described above are being provided here courtesy of and with permission of Aircraft Propeller Service LLC.
Aluminum Props Versus Composites
You can get two to three overhauls out of an aluminum propeller, and material can be added to composite propellers, but this is labor intensive and twice as expensive than overhauling an aluminum propeller, says O’Keefe. “Repairing a composite propeller is a lot like doing bodywork. There’s a lot of filling, sanding, and painting involved.”
Propeller Balancing
While Aircraft Propeller Service does not “dynamically balance” propellers when the propeller is reinstalled on the aircraft, O’Keefe says that dynamic balancing can help make an engine operate more smoothly.
An Operating Tip Worth Remembering
There seems to be disagreement among pilots as to how many times a high-performance/variable pitch propeller needs to be cycled prior to takeoff.
O’Keefe says that the whole purpose of cycling a propeller is to bleed all of the air out of the system before takeoff. Otherwise, there is a chance that the propeller will over-speed with air only inside the cylinder, putting a major strain on the engine, not the propeller.
Cycling the propeller replaces air in the propeller cylinder with engine oil.
To ensure that the oil is well circulated, O’Keefe recommends cycling the propeller three (3) times, and getting between a 100 to 150 RPM drop. He does not recommend pulling the propeller control all the way back, as it is a major strain on the engine, not the propeller.
O’Keefe says that you need to operate your engine at least 1 hour at full engine operating temperature to get contaminants out of the system. Another way to help rid the propeller of contaminants is to cycle the propeller twice before shutdown when the oil is hot and clean. This will prevent sludge from building up in the propeller cylinder.
No matter how you look at it, a propeller is a major aircraft component and well worth the owner’s time to maintain.
For additional information about Aircraft Propeller Service sales and service, contact Sean O’Keefe at 1-800-323-4130 (www.aircraftpropeller.com).
