Mod 7-8-9 Flashcards
vibration ranges 3 types ?
-Low
Vibrations less than 500 Hz Example: Main Rotor
-Medium
Vibrations between 500 Hz and 2000 Hz Example: �2 per Rev� Main rotor or airframe vibrations
-High
Vibrations above 2000 Hz Example: Tail Rotor, Drive Shafts, Fan Shafts, and cooler blowers
They will be low frequency because of the RPM of the main rotor (less than 500 RPM). Main Rotor vibrations can show up in two forms:
Lateral
Vertical
The blades are considered aligned when the_________________________ of the blade is aligned with the feathering axis for the blade.
center of pressure
which balance should be adjusted first?
chord wise as it will have an effect on the span wise balance.
Never sweep a blade________ of the alignment position. A move of the alignment position may cause the rotor system to become unstable.
forward, forward
where you add weight for Chord wise Balance:
Blade can be swept aft of alignment position
Weight may be added to the main rotor hub
where you add weight for Span wise Balance:
Weight is added to the blade bolts
track is adjusted two ways:
Pitch Links
Blade Tabs
If a low frequency vertical vibration is consistent from a hover to high-speed forward flight, it indicates that a ________ should be adjusted.
pitch link
If a low frequency vertical vibration increases with airspeed, it is an indication that a ___ should be adjusted.
tab
Static balance of the tail rotor is commonly done one of two ways
Horizontally (Marvel Universal balancer)
Vertically (Knife Edge Stand)
vibration management static balance ?
part is fully assemble but not installed
vibration management dynamic balance ?
part is installed and aircraft is running and sometimes flying
vibration management final acceptance ?
autorotation RPM adjustment
what is target ?
the reference blade or point
what is blank?
opposite to the target
what is clock angle ?
location of the vibration
what is ips
inches per second. level of vibration
helicopter stability Dynamic stable means ?
the helicopter will recover to its original position , oscillations decrease to nothing
helicopter stability Dynamic unstable means ?
the helicopter will not recover from its original position, oscillations get worse
helicopters are naturally ?
Dynamically unstable
_________ change the tip path plane of the blades through out all speeds
pitch links
_________ change the tip path plane of the blades at higher speeds
tab
if the vibration changes with speed we called that ?
speed sensitive -adjust with tab
vibration non speed sensitive are adjusted by ?
pitch link
flight directors are for __________
navigation
autopilots are for ________
stability
Basic autopilot modes are
SAS, ATT and CPL
The autopilot cannot couple to the _____________
flight director in SAS
Flight director commands can be______________ while the autopilot is engaged in the ATT mode
flown manually
SAS is a _________ mode and ATT is a ________mode
hands-on, hands-off
Coupled (CPL) Mode
the autopilot(s) follow flight director lateral and vertical steering commands to achieve the pilots desired flight path. In coupled flight, the AFCS computer is truly flying the helicopter.
ATT (Attitude Retention Mode)
designed to be a hands-off mode. In the ATT mode, the autopilot pitch and roll channels are engaged to maintain the attitude existing at the moment of autopilot engagement.
SAS (Stability Augmentation System)
it supplies short-term attitude and attitude rate stabilization for use in hands-on flying.
what would mean that the center of mass of the rotor system is not in line with the center of rotation?
In industry a lateral vibration may be referred to as a �shuffle�
what is the name of the movement when blades are allowed to move on a vertical hinge.
This movement is known as �hunting�.
Vertical Vibrations are?.
an out of Track condition and are referred to as a �Hump�
The weights on the pitch horns are used to correct for ________on non-hydraulic tail rotor systems.
�pedal creep�
a condition where aerodynamic twisting force or centrifugal twisting force will attempt to change the pitch of the tail rotor, causing the tail rotor pedals to move away from the neutral position.
PEDAL CREEP
