The Propeller, That Spinning Disc Attached to the Engine

Q. How do I grease a propeller hub?

A. Regardless of what you may have been told, do not pump grease into an aluminum hub until it comes out the other side. On older Hartzell steel-clamped props there is a procedure to grease certain hubs by pumping grease in one grease fitting until it came out of the opposite removed fitting. This is not for aluminum hub propellers. The correct procedure is in the propeller owner’s manual.

Q. Is an engine teardown inspection required following a propeller strike?

A. This isn’t a question for the propeller manufacturer. Many technicians think that our repair or overhaul criteria “forces” the customer to tear down his/her engine. The answer to this question needs to come from the engine manufacturer.

Q. What are the proper procedures for propeller installation?

A. Propeller installation and removal questions are quite common such as correct torque and correct clocking angle. Generally speaking, the prop doesn’t care about clocking, but the engine might. If replacing a two-blade with a three-blade, for example, if there are no directions in the STC installation instructions, ask the engine manufacturer about prop position on your particular engine model. Nut or bolt torque can be found in the propeller owner’s manual.

Q. Where do I find propeller maintenance and troubleshooting data?

A. In the propeller owner’s manual. Such information includes: installation procedures, lubrication, troubleshooting, and much more. Technicians in the field need to be more aware of owner’s manual content, and manual availability. In our case all of the owner’s manuals are on the Hartzell web site.

A lot of the technicians call requesting data they could easily find on the web site. Our web site contains all of the propeller owner’s manuals including revisions. It also contains service bulletins, service letters, and airworthiness directives relating to our propellers. We provide almost all technical information needed by aircraft mechanics and end-users for care and feeding of our propellers. We do not provide overhaul manuals free on the web site, as they are specific to propeller overhaul and major repair, which may only be accomplished by a certificated propeller repairman, usually at a propeller overhaul facility.

Q. What are the propeller overhaul requirements? Is my prop unairworthy if it hasn’t been overhauled on time? What are the overhaul requirements for a Part 91 operator?

A. These are very common questions also, particularly from Part 91 operators. As far as Hartzell is concerned, propeller overhaul per Hartzell Service Letter HC-61-61Y is required, even for Part 91 operators. However, FAA regulations can be interpreted to indicate propeller overhaul is optional for Part 91 operators, so it is frequently done well past Hartzell recommended limits.

Our propeller overhaul recommendation on most modern GA propellers is six years or 2,400 hours of operation, whichever occurs first. Unfortunately, many people recognize the hourly requirement, but ignore the calendar limit. What you really need to consider is how many hours a year the aircraft is flown annually. If your customer is a typical GA pilot who flies 100 hours per year, are you and he/she both comfortable with not looking at the propeller for 24 years?

Q. Should I overhaul the prop governor at the same time as the propeller?

A. This is a great question because prop governors often get neglected as they are out-of-sight and out-of-mind. Here’s the situation that all too often exists: An engine comes time for overhaul and it is removed and exchanged. Many times the accessories are removed from the old engine and held in the shop or hangar and later reinstalled on the exchanged engine when it is installed on the aircraft. Our advice is to not forget about the prop governor. Hartzell recommends governor overhauls be performed in conjunction with the engine overhaul. Remember that a neglected governor can fail, and when governors fail the result is metal makes its way into the entire oil system fast. Such contamination can lead to sudden and severe engine damage, as well as a complete loss of propeller rpm control.