Aircraft Propeller Removal and Installation

Proper propeller removal and installation are essential to ensure safe operation, correct alignment, and reliable performance. Following approved maintenance procedures helps prevent damage to the propeller and engine components while maintaining proper mounting integrity. This section outlines the general procedures for removing and installing a propeller assembly.

Removal

The following procedure is provided for demonstration purposes only. Always use the current manufacturer’s information when removing and installing any propeller.

1. Remove the spinner dome in accordance with the spinner removal procedures. Cut and remove the safety wire (if installed) on the propeller mounting studs.

2. Support the propeller assembly with a sling. If the propeller is reinstalled and has been dynamically balanced, make an identifying mark (with a felt-tipped pen only) on the propeller hub and a matching mark on the engine flange to ensure proper orientation during reinstallation and prevent dynamic imbalance.

3. Unscrew the four mounting bolts from the engine bushings. Unscrew the two mounting nuts and the attached studs from the engine bushings. If the propeller is removed between overhaul intervals, mounting studs, nuts, and washers may be reused if they are not damaged or corroded.

CAUTION: Remove the propeller from the mounting flange with care to prevent damaging the propeller mounting studs. Using the support sling, remove the propeller from the mounting flange.

4. Place the propeller on a cart for transport.

Installation

A flange propeller has six studs configured in a four-inch circle. Two special studs that also function as dowel pins are provided to transfer torque and index the propeller with respect to the engine crankshaft. The dowel pin locations used on a particular propeller installation are indicated in the propeller model stamped on the hub.

Perform the applicable steps under Spinner Pre-Installation and clean the engine flange and propeller flange with quick-dry Stoddard solvent or methyl ethyl ketone (MEK). Install the O-ring in the O-ring groove in the hub bore.

NOTE: When the propeller is received from the factory, the O-ring has usually been installed.

With a suitable support, such as a crane hoist or similar equipment, carefully move the propeller assembly to the aircraft engine mounting flange in preparation for installation.

Install the propeller on the engine flange. Make certain to align the dowel studs in the propeller flange with the corresponding holes in the engine mounting flange. The propeller may be installed on the engine flange in a given position, or 180° from that position. Check the engine and airframe manuals to determine if either manual specifies a propeller mounting position.

CAUTION: Mounting hardware must be clean and dry to prevent excessive preload of the mounting flange.

CAUTION: Tighten nuts evenly to avoid hub damage.

Install the propeller mounting nuts (dry) with spacers. Torque the nuts in accordance with the specified values and safety wire the studs in pairs (if required by the aircraft maintenance manual) at the rear of the propeller mounting flange.

Quick Review: Propeller Removal & Installation

Why is it critical to mark the hub and engine flange before removing a dynamically balanced propeller?

If a propeller has been dynamically balanced on an aircraft, a technician must make matching alignment marks on the propeller hub and the engine crankshaft flange using a felt-tipped pen only. This ensures the propeller is reinstalled in the exact same relative orientation, preserving the precise weight distribution and preventing severe dynamic imbalance and vibration during operation.

What is the structural purpose of the two special studs found on a flanged propeller hub?

A standard flanged propeller uses a configuration of six mounting studs. Two of these are specialized studs that double as dowel pins. They are specifically engineered to index the propeller with respect to the crankshaft and effectively transfer engine torque to the propeller assembly.

What chemical solvents should be used to clean the mounting surfaces prior to installation?

Before mounting the assembly, technicians must thoroughly clean both the engine flange and the propeller flange using a quick-dry Stoddard solvent or methyl ethyl ketone (MEK) to ensure the mating surfaces are completely free of dirt, oil, and grease.

Why must propeller mounting hardware be kept completely clean and dry during torque application?

The mounting nuts and spacers must be installed completely dry. Any presence of oil, grease, or anti-seize lubricants on the threads will alter friction coefficients, leading to over-torquing and an excessive structural preload on the mounting flange. This can stretch the hardware or crack the hub. Nuts must also be tightened evenly in a cross-pattern to avoid physical hub damage.

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