Revision G
October 14, 1996 19
3.6. ADJUSTMENTS
Figure 3-3 shows the location of the adjusting pots on the back of the TRI NAV.
When setting the TRI NAV level, remember correct level is VERY important. A too low
level will reduce range and reduce localizer deflection sensitivity; a too high level will cause
instability when flying near a VOR or Localizer facility.
Inject a “Standard Localizer Deviation Signal” at 1000 microvolts into the NAV receivers.
This is a signal in which the difference in the depth of modulation of the 90 and 150 Hz
signals is 0.093 ±.002 DDM. With Pin 5, NAV 1 fail, open, set the LEVEL ONE control
such that eight bars of deflection are showing on the Localizer display. To set the VOR/LOC
level control, first rotate the adjustment fully counter clockwise, the bars will blank at this
point. SLOWLY rotate the VOR/LOC level control clockwise until eight bars are
illuminated. Inject a localizer centering signal. Adjust the LOC 1 center control until the
bars are centered. Repeat the level adjustment with the "Standard Localizer Deviation
Signal" set to the opposite mid scale.
With Pin 5 grounded, repeat this procedure while adjusting the localizer center and level 2
controls. Setting the Localizer level automatically sets the VOR level. The bar display will
blank if the setting is either too high or too low.
Using a 1000 uV VOR RF signal, adjust the PHASE pots for a zero degree VOR error. After
each adjustment is made allow eight seconds for the TRI NAV to settle down. Phase is
adjusted with both function switches in the UP (to) position.
Using a 1000 uV “Standard Glide Slope Centering” signal, adjust the Glide Slope Centering
pot until the two center glide slope bars are on. While adjusting the glide slope, the NAV
inputs should be either Localizer of OFF.
After the unit has been calibrated, check the Localizer function at Left Standard Deviation,
Center, and Right Standard Deflection. There should be no error; that is Left and Right
deflections should have eight bars activated, Center should have the two Center bars on.
The VOR function should be checked at 45°, 90°, 135°, 180°, 225°, 270°, 315°, and 360°.
Maximum error should be ±1°.
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