TM 1-6625-724-13&P
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recalculate a diagnostic solution, reducing the total adjustments by at least one (in some cases, the
system may remove more than one when two adjustments were working in concert). Each time a new
solution is presented, a new set of predicted results are calculated as well. Careful observation of the
predictions will indicate if the recent reduction in adjustment count still provides an effective solution.
Note that the CADU is considering the vibration and track levels of all airspeeds, so it is important to
review ALL prediction levels before deciding upon a specific adjustment set.
(c) While it is possible to manually edit out specific adjustments using the Edit Adjustables screen, it is
important to note that the selection of the recommended adjustments is based on a complex interaction of
multiple accelerometer channels as well as track. Manually ‘turning off’ the smallest adjustment (in terms
of quantity or ‘size’ of the adjustment) may not be the best course of action. Using maximum number of
adjustments will allow the algorithm to select an adjustment based on its effectiveness rather than size.
2.
Resolve to Limit (Selection Options: On / Off)
This option is intended to act as an ‘automatic best maximum number of adjustments’ with one major
difference. Whereas all other diagnostic routines are attempting to achieve vibration levels of zero, this option
allows the diagnostic a greater latitude when deciding if the solution is acceptable. In simple terms, the
diagnostic is attempting to use the smallest set of adjustments to get the aircraft below the vibration levels
defined as acceptable limits (typically 0.2 ips). This is often the most rapid method to get the aircraft within
limits with as little maintenance activity as possible.
3.
Weighting Mode (Selection Options: Default / Auto)
(a) Each aircraft script file contains a carefully established weighting structure. This is referred to as the
“DEFAULT” weighting structure. It is designed to act as a priority scheme, instructing the diagnostics
system, in cases where all Test States and vibration levels can not be reduced, what flight conditions and
vibration/track data points are to be targeted first.
(b) This weighting structure is determined by such factors as aircraft mission, type of rotor system, and
repeatability/effectiveness of adjustments at certain Test States.
(c) However, it is recognized that there are times when the system seems to be ‘disregarding’ a particular
data point, leaving out adjustments that might help tune the vibration to acceptable levels. One possible
reason for this phenomenon is that the default weighting has been ‘de-tuned’ or reduced in priority at that
particular data point for the benefit of others.
(d) Selecting the weighting mode to AUTO will instruct the system to review the vibration and track profile of
the current data set, and when necessary, modify the default weighting structure relative to the measured
data. This will allow the system to have more flexibility when calculating the optimal set of adjustments.
4.
Adjustment Sequencing (Selection Options: On / Off)
(a) This setting, when used, employs a recognition that some types of adjustment are more difficult to install
than others. A sequencing scheme enables the system to selectively enable an adjustment type based
on an effectiveness versus preference. When enabled in the aircraft script file, the diagnostic will
sequentially enable the various adjustments based on a predefined pattern until an acceptable diagnostic
solution is achieved.
(b) When the default is OFF, the operator can assume that there is no sequencing established in the aircraft
script file, and therefore there is no ON option. When the default is ON, a sequence has been defined
and will be used for each diagnostic solution, and can be disabled by setting this option to OFF.
e. Diagnostic DOs and DON'Ts
Each aircraft type has some unique characteristics and a customized setup file: however, there are some
common rules of thumb which should be followed when using the diagnostic editing function and making
corrections to the aircraft. For specific airframe instructions, consult the aircraft specific work package or
Maintenance Manual. The ability to use the diagnostic editing functions combined with the airframe knowledge
will greatly enhance the ability to make proper corrections to the aircraft quickly. The following are some DOs and
DON'Ts to observe when making corrections to an aircraft:
1.
DO verify that the aircraft needs corrections. The vibration and track levels should be reviewed after the initial
flight to determine if corrections are needed or if the aircraft is within required limits.
