VAL Avionics NAV 2000 Installation Guide download pdf (Page 201)

Autopilot Servo Installation, Configuration, and Calibration

SkyView System Installation Guide - Revision R 10-7

called out maximum linear travel specification. If too much slippage occurs during servo flight

testing, it may be necessary to use a stronger servo.

Each Dynon Avionics servo includes a precision-machined brass shear screw that

pins the servo arm to the servo arm attachment, providing an ultimate manual

override. Servo shear screws will break at the application of 100 inch-pounds of

torque, at which point the servo arm will travel freely. If the brass shear screw is

broken during autopilot installation or usage, do not replace it with a standard

screw– contact Dynon Technical Support (contact information at the beginning of

this manual) for a replacement shear screw. Instruction for replacing the shear

screw can be found at http://docs.dynonavionics.com.

A broken shear screw indicates an abnormal condition in the installation and/or

operation of the autopilot and servo, much as a blown fuse or a tripped circuit

breaker indicates a problem in the electrical system. Shear screws should be

replaced with proper parts only after any problems are corrected.

The servo shear screw should NEVER be removed

or adjusted in the normal process of installing an

autopilot servo. Instructions for both replacing a

broken shear screw and instructions for changing

or replacing the servo arm/capstan assembly can

be found at http://docs.dynonavionics.com.

Figure 60 - Shear Screw

There will be a variety of methods used to install the other end of this control linkage to the

existing mechanicals of the aircraft. Some systems will use a hole drilled into the bell crank as

the point where the servo push rod/rod end combination interfaces with the controls. Others

will use an attachment to existing linkage. Others may attach directly to the control stick itself.

It is up to the installer to decide which method is best in terms of safety and AP functionality.

Installers should always keep in mind the range of motion of the servo. Total servo arm travel

needs to be limited to prevent an OVER CENTER condition (see caution note above), while still

preserving the control surfaces’ full range of motion. Carefully consider the prevention of an

over center condition when selecting the mounting location and linkage attachment point for

any servo installation. The built-in control stops of the aircraft will limit the servo arm travel

when installed correctly. Again, Dynon strongly recommends that the included Range of Motion

Limiting Bracket be installed in order to absolutely prevent the possibility of an over center

condition. The Range of Motion Limiting Bracket should not be used as a normal stop; the

aircraft’s built-in stops should always be the primary range limit. The Range of Motion Limiting

Bracket can be installed in different orientations depending on the aircraft geometry. However,

it is important that it constrain the servo arm such that is unable to travel over center in either

direction. An example of how the Range of Motion Limiting Bracket can be installed is

demonstrated below. Use only the screws that are provided or specified in the Range of Motion

Limiting Bracket Kit Installation Instructions (include with the Bracket Kit).

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VAL Avionics NAV 2000 Installation Guide Page 201