Ameri-King AK-451-ELT - Manual (Page 27)

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Following are the FAA guidelines for mounting a TSO-C91a ELT, per RTCA
DO-183 paragraph 3.1.8:
1. “The ELT shall be mounted to primary aircraft load carrying structures such as
trusses bullheads, longerons, spars, or floor beams.”
2. “The mounts shall have a maximum static local deflection no greater than 2.5
mm (0.1 in) when a force of 451 Newtons (100lbs) is applied to the mount in the most
flexible direction. Deflection measurements shall be made with reference to another
part of the airframe not less than 0.3 meters (3 feet) from the mounting location.”
In addition, RTCA Document number DO-182 recommends that “all ELT system
components which must survive a crash intact, should be attached to the airframe in
such a manner that the attachment system can support a 100g load…in the plus and
minus directions of the three principal axes of the aircraft.”
The ELT must be mounted with the arrow which is printed on the battery case
pointing in the direction of flight. The ELT should be mounted with its longitudinal
axis aligned within 10 degrees of the longitudinal axis of the aircraft fuselage. Avoid
mounting the ELT near sources of strong EMI/RFI radiation. (See Fig. 1)
If this is a new installation or if the current installation is unacceptable, find a location
per the following:
RTCA suggests the aft section of the fuselage. Statistically, this is the least likely
section of the aircraft to receive damage in a crash. It is also near the antenna
connection, minimizing cable length between the transmitter and antenna. Maintain
access for maintenance. If possible, avoid locating the ELT where it will be subjected
to chemical fluids such as deicing compounds, cleaning fluids, etc. Over time, these
may attack the plastic and metal components.
The mounting location must conform to the requirements of RTCA DO-204 and AC
43.13-2B. DO-204 Sec 3.1.8 states:
"The ELT shall be mounted to primary aircraft load carrying structures such as
trusses, bulkheads, longerons, spars, or floor beams (not aircraft skin). The mounts
shall have a maximum static local deflection no greater than 2.5 mm (0.1 in.) when a
force of 450 Newton's (100 lbs) is applied to the mount in the most flexible direction.
Deflection measurements shall be made with reference to another part of the airframe
not less than 0.3 meters (1 foot) nor more than 1.0 m (three feet) from the mounting
location."
Separate mounting-hole patterns are provided so that, if the AK-451 is replacing an
existing ELT listed below, the original mounting holes can be used. Remove the old
ELT holder or tray and install the AK-451 mounting tray in its place. Stainless steel
hardware is recommended. Use hardware conforming to an accepted standard such as
AN or Mil-Spec.