ICON A5, Maintenance Manual

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2-30 GENERAL / FASTENERS
ICON A5 / MAINTENANCE MANUAL CHANGE C3
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2.20 Fasteners
2.20.1 General
The A5 primarily uses stainless steel fasteners throughout the airframe for corrosion resistance. Coun-
tersunk Phillips fasteners are used in structural locations. Other hardware is AN aircraft hardware, but
of the stainless variety. To the extent possible, all bolts and screws shall be mounted with the heads
higher than the rest of the bolt/screw. This helps ensure that even in the event of a nut coming off,
gravity will still help hold the bolt/screw in place. All bolts and screws shall have at least one thread
protruding from the associated nut or nutplate. A calibrated torque wrench shall be used on any
fastener where the torque target is critical.
2.20.2 Flat Washers
The maximum total washer combination is four washers. The maximum number of washers under the
head or nut is two. If the minimum thread protrusion through the nut cannot be achieved due to varia-
tions in material thickness, a thin washer may be used. Thin washers may also be used in place of stan-
dard washers when castellated nuts cannot be aligned for safetying. A washer shall also be used if
rotation of the bolt head would cause wear or damage to the underlying structure. If these washers are
not sufficient to ensure appropriate thread engagement or avoid thread bottoming, a different grip
length bolt or screw shall be used.
2.20.3 Lock Washers
When using bolts or screws into blind tapped holes (no nuts), Nord-Lock washers shall be used unless
specified otherwise. Nord-Lock washers shall be installed per the Nord-Lock Washer Information
Document. Bolts and screws using Nord-Lock washers shall be torqued per this document.
Other lock washers (split, internal star, external star) are not recommended and shall only be used on
primary or secondary structures where failure will not result in damage or danger to aircraft or
personnel.
2.20.4 Locking Nuts
Locking nuts shall be used in all primary and secondary structure bolted or screwed non-blind hole
connections.
Bolts and screws shall be torqued per FAA Advisory Circular (AC) 43-13.1B, Chapter 7, Table 7-1 and
section 7-40 for either shear or tension applications. Torque shall be applied to the nut, with the bolt
head held motionless if at all possible. Torque required to run the nut down to a seated condition shall
be added to the required torque for the application and the TOTAL torque shall be the final require-
ment.
Any Stainless Steel bolts and screws shall use MS21043 or MS21046 Stainless Steel Silver Plated
locking nuts to avoid galling threads.
Lock nuts shall not be reused.