FES Propeller Manual Version 1.0
February 2013
Page 8 of 9
- inspect propeller as per instructions given under 5.2. If any crack is found, the
propeller must be removed from service immediately. Send propeller to the manufacture
for inspection.
5.4 Over-speed: Up to 15 % above the rated maximum rotational speed RPM
inspection per 5.2 and 5.3 is required. At more than 15 % over-speed the propeller should
be sent to the factory for inspection.
5.5 Service time between main overhauls is 50 flight hours. Main overhaul can be
performed by propeller manufacture only.
7. Possible damages and allowables
6.1 No structural cracks or de-laminations of composite structure are allowed for the
propeller.
6.2 Small cracks up to 10 mm of length in a lacquer are allowed. Make sure cracks
are in a lacquer layer only and not going into the composite structure. Fine cracks in the
lacquer surface across the blade axis are indications of bending vibrations. Such cracks
mostly occur in the outer part of the blade. No sudden blade failure can occur due to
these cracks. If such cracks do occur, the factory should be consulted regarding
airworthiness, if possible together with a photo and information about operating time.
6.3 The erosion occurs due to the peripheral speed of the blade and is normal.
However, always take care that the erosion never becomes so deep that FRP-coat is
damaged and there is a possibility that moisture may enter into the blade body. In this
case the blade must be repaired/overhauled immediately.
6.4 Stone damages. If stone damages are visible, mark them and check them
periodically. Maximum size of stone damages permitted for operation is 2x4 mm large and
0,7 mm deep. Maximum number of damages allowed is one damage per 4 cm
2
. If bigger
or more damages exist on a blade, send propeller to manufacture for inspection and
overhaul.
6.5 Cracks or deformations in a center part of the propeller are not allowed. If such
occurs, send propeller back to manufacture for the overhaul.
8. Maintenance and repair
Note:
Serious cracks which originate from the inside of the blade, are extending
through the lacquer and so are visible from outside. These cracks are radial
cracks or tangential cracks. Fine cracks in the lacquer as described above,
are considered of serious character, although they usually start at first in the
lacquer and not in the composite structure.
7.1 Clean propeller if necessary with water.
7.2 Normal small stone nicks are unimportant as long as there is not obvious
structural damage. Scratches and nicks should be filled and protected during routine
maintenance with a coating of water resistant lacquer. Allowables for damages are given
in a Paragraph 6 of this document.
