17.7 Propeller Storage and Preservation Flashcards
The preservation and de-preservation procedures and storage periods for both serviceable and unserviceable installed propellers are found in the Aircraft Maintenance Manual (AMM)
while uninstalled propeller preservation, depreservation procedures and storage periods are found in the Propeller Maintenance Manual (PMM).
Storage periods for propellers are typically divided up into periods of up to:
3 months - short-term
6 months - long-term
12 months - long-term
3 years - long-term
Installed Propellers
periods up to 3 months
installed wooden propellers must be kept in a clean condition and inspected at regular intervals.
(Periods up to 3 Months)
Wooden fixed pitch propellers must be placed in a horizontal position to ensure that there is even moisture distribution. They must be cleaned with a mild solution of soap and water and inspected for damage.
The blades must be adequately ventilated and, if possible, the storage area must be clean, warm, dry, dark and well ventilated as well as free from corrosive vapours. Ideal storage temperatures are between 10°C (50°F) and 20°C (68°F).
To prevent rot, wooden propellers should not be wrapped in any way that would seal it off from the air.
(Periods up to 3 Months)
The procedure for metal fixed pitch propellers is similar to wooden but with the addition of regular corrosion inspections.
.
(Periods up to 3 Months)
Variable pitch propeller pitch change mechanisms need to be exercised to circulate the oil in the pitch change mechanism prior to engine shut down. On completion of the ground run, the propeller must be cleaned using a mild solution of soap and clean water and inspected for signs of corrosion.
.
Periods up to 6 Months
If the propeller is to be stored on the wing for periods in excess of 3 months then what must happen
the pitch change mechanism must be flushed using an inhibiting oil and then covered with waxed paper.
All external parts must be treated with lanolin or an approved anti-corrosive treatment and inspected regularly for corrosion
Ensure that lanolin does not come into contact with the de-icer boots
.
Preservation of Uninstalled, Assembled Propellers
(Short-term Storage up to Three Months)
If a wooden propeller has an automatic pitch change mechanism, the hub must be filled with oil. The propeller must be turned every two weeks to ensure that the internal surfaces of the hub are coated with oil. Regular inspections must be made for signs of deterioration
Variable pitch propellers must have been exercised prior to their removal. If they remain assembled, they must be cleaned and then stored in a warm, dry and dust free environment, free from corrosive vapours. Ideal storage temperatures are between 10°C (50°F) and 20°C (68°F).
.
Propellers with metal blades must be stored in an upright position on stands where the hub is supported by what
a mandrel
The external surfaces of the propeller must be coated with lanolin or an approved corrosion inhibitor.
.
The pitch change mechanism must be drained of oil and flushed with approved inhibiting oil. The pitch change mechanism surface must be coated in lanolin and the mechanism must be wrapped in waxed paper.
.
The oil transfer tubes and the propeller attachment parts must be cleaned, coated in lanolin and wrapped in waxed paper.
.
All parts used to secure the propeller to the engine, including the oil transfer tubes, retaining nut assemblies and the location cones are considered to be propeller parts and must accompany it both into storage and while in transit.
.
Long-term Storage up to Six Months
The procedure for wooden propellers remains the same as for short-term storage up to three months
.
Long-term Storage up to Six Months
For metal, variable pitch propellers the procedure is the same as for short-term storage up to three months, with one exception:
If the propeller blades have pre-loaded bearings, the blades must be rotated to prevent the bearings from brinelling. This must be carried out at the six months point.
The rotation procedure is carried out by marking the blade positions relative to their bearings prior to rotating each blade with an approved turning paddle. The blade is turned through its full range of travel at least three times
If the check is satisfactory, the blade must be left at a position at least one inch away from its original position.
Long-term Storage up to Twelve Months
The storage procedures remains the same as for the three and six month examples except that, for pre-loaded blades
the blades require exercising after six months and nine months. At twelve months, the bearings must be removed and visually examined for signs of ‘brinelling’ and corrosion. If satisfactory, the bearings must be cleaned, greased and reassembled on to the blades. The propeller must then be re-inhibited and re-protected.
Long-term Storage over Twelve Months
The storage procedure remains similar to that of the three, six and twelve month examples
However, each year, the blades require exercising at the six months and the nine months stage, followed by bearing removal and inspection at the twelve months point.
The propeller requires re-inhibiting at each twelve months point. At the three year stage the propeller must be sent for overhaul. The overhaul includes a hub/blade inspection as required by AWN75.
Long-term Preservation of Uninstalled, Dismantled
Long-term Storage up to Six Months, Twelve Months and Three Years (Uninstalled and Dismantled)
If the propeller is dismantled and remains in its original manufacturers’ packing it does not require re-inhibiting every twelve months
However, if the blade bearings are in a pre-loaded condition, they are still subject to the requirement for exercising at the six month and nine month periods each year and the annual dismantling and inspection procedure.
Providing these requirements are met, the propeller can remain in storage for up to three years, at which time it must be returned for overhaul.
All the propeller parts must be wrapped in waxed paper and packed into an approved crate. The crate must be labelled with
The propeller type and serial number
Component part numbers
The modification standard
Original date of preservation
The dates of the blade bearing exercise and inspections if applicable
Providing the propeller remains in its packing, it can remain in storage for up to three years prior to being overhauled
.
All parts held in storage require the appropriate Form 1 - Certificate of Conformity (COC), and a valid Certificate of Release to Service (CRS).
.
