Figure 17. ABSORBER/BOXABS Tuning Accel. Installation (View looking up)
PROCEDURE 3: IN-FLIGHT CHECK OF NOSE ABSORBER (Cantilever Spring Type)
If the aircraft is equipped with BOX FRAME type absorbers, proceed to procedure 5.
Nose absorber is tuned to an ips range instead of a specific Nr.
Tuning weight on nose absorber is adjusted based on ips reading from pilot heel vertical (PHV) accelerometer.
The forward cabin absorber must be tuned to 100% Nr at 145 knots before tuning the nose absorber.
Prior to tuning the nose absorber, make sure the forward cabin absorber is not blocked.
The goal for pilot heel vertical level is between 0.3 ips
and 0.6 ips, with 0.5 ips being the target. If the level
drops below 0.3 ips, nose absorber may interfere with
cabin absorber tuning and actually degrade cabin and
cockpit 4/REV vibration.
a. Perform task 4, procedure 2 (Acquire data in the FLIGHT plan).
Test States of 120K and 145K must be measured for the
in-flight vibration absorber test to be completed
b. After the measurement is completed, press DO on Finish, then press DO on Diagnostics.
c. If nose absorber is above limits the CADU will display the ips value and then suggest a weight change to bring
the ips level within the range of 0.3 to 0.6 ips.
d. If pilot heel vertical measurements are outside of recommended range, perform nose absorber weight
adjustments according to TM 1-1520-237-23-2 (Chapter 2, Airframe Maintenance AVUM).
e. Repeat FLIGHT plan and perform adjustments until no further adjustments are required to tune Nose
If the cabin absorber requires tuning, perform procedure 4: Tune Forward Cabin Absorber.