1. UH-60 Mixing Unit, Electronic Coupling, & Stabilator
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UH Mixing Unit, Electronic Coupling, & Stabilator
Purpose: Develop the student IP’s understanding
of the components and functions of the Mixing
Unit, Electronic Coupling, and the Stabilator
References: UH and 23-1, Flight Line Supplement, Student Handouts, TC 1-212
LECTURE BUT WILL ASK FOR PARTICAPATION DURING SOME PORTIONS OF THE CLASS

2. Overview
Mixing Unit
Collective/Airspeed to Yaw (Electronic Coupling)
Stabilator System
Questions

3. Been there, done that, got the coffee cup...
, and a couple of shot glasses.

4. Mixing Unit Functions Collective to Pitch Collective to Roll
Collective to Yaw
Yaw to Pitch
MINIMIZES INHERENT CONTROL COUPLING WHICH REDUCES PILOT WORKLOAD
THE MIXING UNIT COMBINES, SUMS,AND COUPLES THE CYCLIC , COLLECTIVE , AND YAW INPUTS.
*COLL. TO PITCH: PROVIDES FORWARD INPUT TO THE M/R AS THE COLL.IS INCREASED AND VS./VS. CORRECTS FOR ROTOR DOWNWASH ON THE STABILATOR
*COLL. TO ROLL: COMPENSATES FOR THE ROLLING MOMENT AND TRANSLATING TENDENCY CAUSED BY T/R THRUST. LEFT M/R INPUT WHEN COLL.IS INCREASED AND VS./VS.
*COLL. TO YAW: COMPENSATES FOR CHANGES IN TORQUE EFFECT CAUSED BY CHANGES IN COLL. POSITION. INCREASES T/R PITCH AS COLL. IS INCREASED
*YAW TO PITCH: COMPENSATES FOR CHANGES IN THE VERTICAL THRUST COMPONENT OF THE CANTED TAIL ROTOR. AFT INPUT TO THE M/R AS T/R PITCH IS INCREASED.

5. Collective to Airspeed to Yaw
Electronic Coupling
Function of the SAS/FPS computer
Increases or decreases T/R pitch with the Yaw trim actuator
THIS ALSO HELPS TO COMPENSATE FOR TORQUE EFFECT PROVIDING INPUT TO THE T/R BASED ON COLLECTIVE POSITION AND AIRSPEED SIGNALS.
IT’S A SEPARATE FUNCTION OF THE SAS/FPS COMPUTER WHICH SENDS A SIGNAL TO THE YAW TRIM ACTUATOR TO MAKE INPUTS IN THE T/R PITCH.
PROVIDES MAXIMUM INPUT FROM 0-40 knots AT SPEEDSABOVE 40 THE T/R AND CAMBERD FAIRING BECOME MORE EFFICIENT AND LESS MIXING IS REQUIRED. INPUT DECREASES AS AIRSPEED INCREASES TILL 0 INPUT AT 100 knots.

6. Stabilator Components
Control Panel
#1 and #2 Stabilator Amplifiers
#1 and #2 Stabilator Actuators
Position Transmitter/limit Switch Assembly
Airspeed and Air Data Transducers
#1 and #2 Lateral Accelerometers
#1 and #2 collective Stick Position Sensors
Cyclic Mounted Stabilator Slew Up Switches
Stabilator Position Indicators
*CONTROL PANEL-MAN SLEW, AUTO CONTROL RESET, TEST BUTTON (Disabled >60 KTS)
* #1 AND #2 STAB AMPS ARE LOCATED IN THE REAR CABIN OVERHEAD. EACH HAS ITS OWN PITCH RATE GYRO
* POSITION TRANSMITER/LIMIT SWITCH IS IN THE TAIL PYLON , IT CONTAINS 4 LIMIT SWITCHES AND A POSITION TRANSMITTER
* AIRSPEED AND AIR DATA TRANSDUCERS ARE IN THE LOWER FRONT COCKPIT BULKHEAD (REPRESENTS FORWARD AIRSPEED 30 to 180 kts GIVES DC ELECT. SIGNAL)
* #1 AND #2 LATERAL ACCEL. ARE LOCATED IN THE FORWARD CABIN OVERHEAD. GIVE DC SIGNAL REPRESENTING RATIO OF TURN RATE TO BANK ANGLE
* COLLECTIVE STICK POSITION SENSORSARE LOCATED ON THE RIGHT SIDE OF THE MIXING UNIT.

7. Stabilator Components
* THE TEST FUNCTION MOVES THE #1 ACTUATOR 10 deg. UP TO CHECK FOR AUTOMATIC MODE SHUTDOWN WHEN THERE IS A ACTUATOR POSITION ERROR. DISABLED ABOVE 60 kts.
* FOR AUTOMATIC MODE OPERATION EACH STAB AMPLIFIER RECIEVES AIRSPEED, COLLECTIVE POSITION, AND LATERAL ACCELERATION, AND PITCH RATE SIGNALS. AIRSPEED SIGNALS ARE CROSS MONITORED AND USES THE HIGHER SIGNAL IF .80kts ANDIT’S OWN <80. THE COLLECTIVE POSITION AND LATERAL ACCELERATION SIGNALS ARE FADED IN BETWEEN kts.
* MANUAL MODE 4 SETS OF CONTACTS 2 TO THE STAB AMPS DISENGAGE THE AUTO MODE AND 2 DRIVE THE STAB ACTUATORS
* #2 STABILATOR ACTUATOR USES 28vdc FROM THE #2 DC PRI. BUS AND THE #1 ACTUATOR FROM THE DC ESS. BUS (35deg TRAVEL)
30 - COULD START PROGRAMING / LATT ACCEL AND COLL POSITION SIGNALS
40 - MANUALLY SLEW STABILATOR
50 - ABORT T/O
60 - DISABLES “PRESS TO TEST”
70 - MAX AIRSPEED IN AUTO MODE AFTER MULTIPLE FAILURES
80 - LOW A/S STARTS PROGRAMMING DOWN / SLOW-TO SPEED BEFORE RESTORING AC POWER
120 - MAX AUTOROTATION

8. Stabilator Functions S.C.A.L.P.
Sideslip to Pitch coupling
Collective Coupling
Angle of Incidence Decreased w/ Increased Airspeed
Low Speed Flight it Aligns w/ Rotor Downwash
Pitch Rate Feedback
S = REDUCES SUSCEPTIBILITY TO GUSTS OR OTHER PITCH EXCURSIONS. Slip or Skid
C = MINIMIZES PITCH EXCURSIONS DUE TO COLLECTIVE INPUTS.
A = ANGLE OF INCIDENCE DECREASES WITH INCREASED AIRSPEED TO IMPROVE STATIC STABILITY
L = LOW SPEED FLIGHT ...
P = PROVIDES PITCH RATE FEEDBACK TO IMPROVE DYNAMIC STABILITY.

9. Stabilator Malfunctions
STABILATOR MALFUNCTION - AUTO MODE FAILURE
UNCOMMANDED NOSE DOWN/UP PITCH ATTITUDE FAILURE.
WARNING: IF ACCELERATION IS CONTINUED OR COLLECTIVE REDUCED… IF A HARDOVER SIGNAL IS PRESENT AN ACTUATOR COULD MOVE DOWN 4-5 deg IN 1 sec…IF IT FAILS REPEATEDLYFLY 70 kts MAX OR TAKE MANUAL CONT.
If you have a stabilator malfunction, it may be prudent to slow your airspeed before pressing the Auto Cont. reset. There may be a miscompare that is sensed just greater than 4 deg. And at 120 or 130 kias it would cause a failure but wouldn’t at 90 or 100.
UNCOMMANDED DOWN, CYCLIC ADJUST AS REQUIRED
COLL MAINTAIN OR INCREASE
SLEW UP AS REQUIRED
UNCOMMANDED UP, CYCLIC ADJUST AS REQUIRED
COLL REDUCE AS REQUIRED

10. QUESTIONS?
DOES THE STABILATOR PROVIDE COLLECTIVE COUPLING PASSING THRU ETL?
AT WHAT AIRSPEED?