TM 1-1520-238-10 2-46 Change 4 b.   ASE Control Panel. The ASE control panel (fig 2-27)  located  in  the  pilot  left  console,  has  five  single- throw,  two-position  magnetic  switches  labeled  PITCH, ROLL,  YAW,  and  ATTD/HOVER  HOLD  and  a  BUCS TEST (BUCS TST) switch. The BUCS TST switch on the ASE control panel per- mits the pilot to perform a go no-go check of the BUCS. The NOE/APRCH switch is part of the stabilator system. The ASE release button at the base of each cyclic stick grip,  when  pressed,  causes  the  three  channel  switches and the ATTD/HOVER HOLD switch to drop to OFF. The ASE control panel receives 28 vdc from the No. 3 essen- tial dc bus through the ASE DC circuit breaker on the pilot overhead circuit breaker panel. M01-290 ASE YAW BUCS TST PLT CPG OFF ROLL NOE/APRCH ATTD/HOVER HOLD PITCH OFF OFF OFF OFF Figure   2-27. ASE Control Panel c.   Automatic Stabilization. The DASE has a sta- bility augmentation system (SAS) and a command aug- mentation system (CAS). The SAS reduces pilot workload by  dampening  airframe  movement  caused  by  external forces such as in air turbulence and weapons recoil. The CAS augments helicopter response by mechanical con- trol inputs and commands to the longitudinal (pitch), later- al (roll), and directional (yaw) flight control servoactuators. CAS signals are generated by movement of crew station flight controls which are sent to the DASE computer. The DASE computer sums the SAS/CAS information with in- puts from the heading and attitude reference set (HARS) and the air data sensor system (ADSS). The DASE computer   provides   positioning  commands   to  a  two- stage  electrohydraulic  SAS  servo  valve  on  the  primary side of the longitudinal, lateral, and directional flight con- trol servoactuators. The position of the SAS servo valve determines the amount and direction of movement of the SAS actuators. The position of each of the SAS actuators is transmitted to the DASE computer by the LVDTs. The motion of each SAS actuator is summed with the mechan- ical input to each flight control servo, but the SAS actuator authority is limited to 10% bidirectional motion in all axes except the longitudinal where the authority is 10% aft and 20% forward. The DASE is engaged through the pilot ASE control panel. d.   Attitude/Hover  Hold. The  hover  augmentation system (HAS) or HOVER HOLD mode of the DASE uses SAS actuators to maintain position and damp external dis- turbances to the helicopter. HAS is set by engaging the ATTD/HOVER HOLD switch or by using the momentary OFF (up) position of the pilot FORCE TRIM REL switch. HAS provides the pilot with limited station-keeping or ve- locity-hold during hover or low speed flight. Position-hold accuracy is a function of inertial velocity drift errors of the HARS which can vary with time. The SAS authority mar- gin will be biased from its center position as these errors build  with  time.  The  attitude  hold  is  a  limited  authority mode of the DASE in pitch and roll axes. This mode pro- vides the pilot with limited hands-off flight capabilities in cruise  flight.  Attitude  hold  will  only  function  if:  (1)  the ATTD/HOVER HOLD, PITCH, and ROLL switches on the ASE panel are engaged; (2) force trim is on, and (3) longi- tudinal airspeed of the helicopter is greater than 60 KTAS. CAS is removed when the attitude hold mode is engaged. CAUTION HAS  should  not  be  used  as  the  sole method  for  station  keeping.  Cross- checking obstacle clearance using visu- al or NVS means shall be accomplished. Do  not  activate  HAS  on  the  ground  or land  with  HAS  on.  Uncommanded  air- craft attitude changes may result. The initialization and stability of the HAS is affected by the HARS velocity drift. A HARS velocity error at HAS initiali- zation will cause initial aircraft movement (at a rate pro- portional to the HARS velocity error) that may be trimmed using  the  cyclic  force  trim.  Subsequent  changes  in  the HARS velocity accuracy, during prolonged engagement of the HAS, will cause additional aircraft movement that may be re–trimmed.