Recieved the following guidance from our local EC rep (Dave Dunstan). Dave asked me to share this with the community, so grab a cuppa and sit back...
AS350 CYCLIC CONTROL (Binding - Stiffness - Motoring)
1. Servo input linkage (PRIMARY CAUSE)
--->Spray lubricate the Sloppy Link area or input lever linkage.
2. Servo’s (SAMM Servo’s read SL 1446-67-00, Dunlop Servo’s read SL 1064-67-91)
--->Servo’s are the 2nd Primary cause of cyclic binding in one direction but check the preliminary items listed below first. Eliminate the less expensive items.
3. Swashplate guide tape balled-up
--->Look at the forward L.H. quadrant of the swashplate guide with the collective pulled up.
4. Swash plate shimmed too tight
--->Remove shims. The uniball should have 0.012” vertical movement and rotate with hand pressure.
5. Walking beam pivot bolts (located at the bottom of each servo input rod)
--->Caused by stiffness and the pivot bolt nut being over-torqued. Walking beam side play should be min. 0.015”
6. Servo input rods - left and right lateral
--->Realign with the collective up and install the 15 degree upper servo rod end locks. MWC Chapter 67.
7. Cyclic friction cup needs cleaning
--->Lift the cups and clean with alcohol.
8. Dual control coverplate
--->Inspect the underside for rubbing caused by the co-pilot’s cyclic stub.
9. Lateral control rod under the floor
--->Lateral binding only, predominately on older AStars. The rod which goes from the cyclic, left to the center bellcrank. (Spray lubricate the rod end if it is stiff.)
10. Control rod end bearings under the floor (the stamped type)
--->Spray lubricate although this is rare.
11. Hydraulic filter
--->Change, although it would be rare to have a filter so dirty as to create a restriction of the flow.
12. Hydraulic pump inlet filter
--->This inlet finger screen, if dirty, normally causes a restriction which results in a flow / volume problem and causes a Dim Hyd Light or a occasional “Beep” of the horn. Clean this screen periodically.
13. Hydraulic pump
--->Very rare that a pump would not produce the pressure and volume.
14. Mixing unit end bearings
--->Grease with hypo needle (very rare cause).
15. Servo inlet check valve
--->Disassemble and clean (very rare cause).
16. Long. torque tube mount
--->Grease end cap bearings or change (very rare cause).
COLLECTIVE CONTROL BINDING
Note: If the general hydraulic system, fluid, pump inlet screen or the pump is the cause, it should effect the cyclic stick also. Control coupling between the collective and the cyclic is caused by the Dunlop servos sloppy link which needs spray lubrication, or the MGB deck bellcrank pivot bolts being too tight.
1. Collective Friction
--->Check.
2. Anticipator spring
--->Check the spring is not extending with the collective up. The pilot sometimes states he has reached the upper stop when he feels the spring extend. This becomes a Governor rigging problem or a binding Gov. cable problem.
3. Governor cable:
--->Cable binding internally -> change the cable (very common).
--->Cable may have tie wraps securing it to the engine -> It should be free floating under the engine.
4. Swashplate guide or tape
--->Lift the collective and check the left front quadrant of the swashplate guide for balled up tape.
5. Co-pilots collective cover plate
--->The co-pilot's collective stub is rubbing the cover plate.
6. Snap-on connector of the Gov. cable at the FCU connection
--->Remove and grease.
7. Scissors (MRH) binding
--->Check for the proper side play and the pivot bolts for lubrication. Scissors' pivots points should be disassembled and greased each 500 hours and if necessary spray-lubricated at 100 hours to keep them free.
8. Mixing-unit torque tube end cap bearings
--->Inject grease (normally shows in forward flight as the rotor loads build-up and goes away at a lower airspeed).
9. Servo input rods to the servo’s are misaligned with the collective pulled up.
--->Install the upper servo rod end bearing new 15 degree lock per MWC Chapter 67
10. MGB deck bellcrank
--->The lateral bell cranks are just under the MGB deck and the longitudinal is on the top front left of the MGB deck. These bell cranks must have 0.010” to 0.020” side play and the pivot bolts must be clean and not over torqued. This is very important.
11. Mixing unit torque tube Teflon bushings
--->Rare cause.
12. Collective torque tube Teflon bushings at the base of the collective
--->Rare cause.
13. Stamped control rod end bearings
--->Rare cause.
TAIL ROTOR CONTROL BINDING
Note: Control problems caused by the hydraulic pump or the pump inlet screen should effect all the controls.
1. Tail rotor control cable binding inside its sheath (average life is 2000 hours).
--->The pilot will have to push hard to break thru the binding.
2. Tail rotor control cable 14 mm jam nuts have come loose
--->Located in the upper rear baggage compartment and under the R.H. front floor.
3. Tail rotor control tube binding on the tail boom mounts
--->The heat shrink may be rolling up where the tube passes thru the hangar mounts.
4. Tail rotor spider binding on the TRGB chrome shaft
--->Due to the split bushings installed with too much adhesive. Max pull of the spider on the shaft is 30 lb of force.
5. Tail rotor bellcrank expandable bolt
--->Lubricate and look for minimum 0.015” vertical movement of the bellcrank. Look closely at the bellcrank and TRGB ears to see if the bushing in the bellcrank or in the two ears has came loose and is limiting the bellcrank vertical movement.
6. Tail rotor pedal pivot point in the cockpit.
--->Rare cause.
7. Tail rotor servo or the servo input linkage
8. Yaw compensator (AS350 B2/B3)
--->It is rare for the yaw compensator to be the cause, although there is sometimes a misunderstanding of the compensator and it gets changed prematurely (can be expensive). When in doubt ask the Eurocopter Pilot section, as they teach the system and have a very good understanding of it. A yaw compensator document is available (send your email address).
I/C