Difference between revisions of "Unequal Collective Pitch"

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(Created page with "If you are struggling with achieving equal Collective Pitch range for positive and negative side, then the following procedure is for you. == Transmitter == First it is impor...")
 
(Mechanics and Geometry)
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== Mechanics and Geometry ==
 
== Mechanics and Geometry ==
 
Correct configuration is important to achieve good flight performance. Especially for beginners it could be unclear what are correct steps to do this well.
 
Correct configuration is important to achieve good flight performance. Especially for beginners it could be unclear what are correct steps to do this well.
If steps are performed in a wrong way it will usually lead to an incorrect configuration. Correctly you have to start with servo adjustment and go up step by step until you will reach blade holders. After each completed step do not touch what was configured previously.
+
If steps are performed in a wrong way it will usually lead to an incorrect configuration and eventually some odd behavior in the flight. Correctly you have to start with servo adjustment and go up step by step until you will reach blade holders. After each completed step do not touch what was configured previously.
  
#Move to the '''Servo tab''' and there toggle the '''Subtrim (tuning)''' - in this mode servos should be locked exactly in the center. This mode is recommended to be enabled each time you are configuring mechanical center of anything, including 0° between main blades.  
+
#Move to the '''Servo tab''' and there toggle the '''Subtrim (tuning)''' - in this mode servos should be locked exactly at the center (neutral) position. This mode is recommended to be enabled each time when you are configuring mechanical center, including 0° between main blades.  
#Set all servo arms as close to the center as possible - ''(usually perpendicular with respect to servo case) - this should be done with Subtrims in the Spirit Settings (when Subtrim tuning is enabled).''
+
#By moving with Subtrims move with corresponding servo to set all Servo arms as close to the center as possible (you can do this also for Rudder).
# put push rods/ball linkages perpendicular (as close as possible) with respect to servo arm and swashplate - in some models it is unfortunately not possible which always mean error, but you as pilot can't do much about it sometimes. (when Subtrim tuning is enabled).
+
''(Servo arms should be usually perpendicular with respect to their servo cases)''
# adjust 3 push rods to the same length (if model is constructed in this way). If not, then it adds usually another imprecision to the geometry. But again you can't do much about it. At the same time achieve position where swashplate is in the center of its collective pitch travel and at the same time to be perfectly level with a cyclic leveler. This mean to change length of all 3 rods equally (always). (when Subtrim tuning is enabled).
+
#Put push rods/ball linkages perpendicular with respect to the servo arm and swashplate (as close as possible). This mean you have to select which hole of the servo arm is the closest to the perpendicular position. It is always same hole on all cyclic servos. In some models it is unfortunately not possible perfectly which always mean additional error, but you as pilot can't do much about it. ''Note that also in this step Subtrim (tuning) option should be toggled''.
# mount the rotor head and change length of 2 upper push rods that are connecting blade holders so that they are again equal and at the same time they are configured to be at 0°. This mean when you put there a main blades and fold ends together, they must be exactly at the same level. And this level should be held at any angle/position/rotation of the main shaft. If not, usually swashplate is not levelled correctly or there is a big play in the mechanics.
+
#Adjust 3 push rods to the same length (if helicopter manual is suggesting same length for all 3 servos). If not, then it adds usually another imprecision to the geometry. But again you can't do much about it.
# At this point, if manufacturer of the model designed it correctly and your servos have equal servo travel, then you must achieve always same collective pitch travel in both direction. If not, then go to the Servos/Servo Travel Correction and move with a sliders (usually it is enough to move with all 3 values by same amount). When done correctly, you will get perfectly precise angles.
+
#Try to set length of the 3 push rods when swashplate is at the center of its Collective Pitch travel. This can be determined by looking at the '''Anti-rotation bracket''' of the swashplate where swashplate should be approximately at the center. Adjust lengths of all 3 push rods by an equal amount (so that resulting length is same).
 +
#Then use the Cyclic Leveler tool and fine-tune lengths of all 3 push rods (usually to be equal again). ''Subtrim (tuning) option should be still enabled''.
 +
#Mount the Rotor head and adjust length of 2 upper push rods that are connecting blade holders so that they are again equal and at the same time they are configured to reach 0°. This mean when you mount a main blades there and fold ends together, then both ends must be exactly at the same level. And this level should be held at any angle/position/rotation of the main shaft. If not, usually swashplate is not leveled perfectly precise or there is a big play in the mechanics.
 +
#At this point, if there is no other imprecision in mechanic your mechanics is configured perfectly. Now you can untick Subtrim (tuning) option and verify if Positive and Negative angles between main blades are equal. If not, then open the '''Servos/Servo Travel Correction''' window and move with a sliders (usually it is enough to move with all 3 values by the same amount). If collective pitch is a higher at one side, move the pitch stick to that side (the lowest or the highest position). Then decrease 3 sliders equally to get the same collective pitch. When done correctly, you should get precise angles in both directions.

Revision as of 20:17, 10 December 2017

If you are struggling with achieving equal Collective Pitch range for positive and negative side, then the following procedure is for you.

1 Transmitter

First it is important if your transmitter was configured correctly in terms of channel travel range. It can be verified in the following way. Start the Spirit Settings and go to the Diagnostic tab.

1.1 Collective Centering

  1. Put your Pitch stick at the center as close as possible.
  2. Verify what value you can see in the Diagnostic tab at the Pitch bar.
  3. Make sure you will see 0%. If value is different by more than +/- 2% it is recommended to use the Subtrim function in your transmitter and adjust Pitch channel to achieve 0%.

1.2 Collective Pitch Low and High position

  1. Make sure that your Collective Pitch curve in the radio is configured to be -100% to 100% (Linear curve). NOTE: In some radios the lowest position starts at 0% but this is not a problem.
  2. Put your Pitch stick at the lowest position - at this point you have to see -100% in the Diagnostic tab at the Pitch bar. If value is diffrent by more than +/- 2% it is recommended to check your
  3. Do the same verification for the highest position - at this point you have to see 100% at the Pitch bar.
  4. If this point are correct and you can see +/- 100% then your radio is configured correctly and you can move at the mechanics configuration.

2 Mechanics and Geometry

Correct configuration is important to achieve good flight performance. Especially for beginners it could be unclear what are correct steps to do this well. If steps are performed in a wrong way it will usually lead to an incorrect configuration and eventually some odd behavior in the flight. Correctly you have to start with servo adjustment and go up step by step until you will reach blade holders. After each completed step do not touch what was configured previously.

  1. Move to the Servo tab and there toggle the Subtrim (tuning) - in this mode servos should be locked exactly at the center (neutral) position. This mode is recommended to be enabled each time when you are configuring mechanical center, including 0° between main blades.
  2. By moving with Subtrims move with corresponding servo to set all Servo arms as close to the center as possible (you can do this also for Rudder).

(Servo arms should be usually perpendicular with respect to their servo cases)

  1. Put push rods/ball linkages perpendicular with respect to the servo arm and swashplate (as close as possible). This mean you have to select which hole of the servo arm is the closest to the perpendicular position. It is always same hole on all cyclic servos. In some models it is unfortunately not possible perfectly which always mean additional error, but you as pilot can't do much about it. Note that also in this step Subtrim (tuning) option should be toggled.
  2. Adjust 3 push rods to the same length (if helicopter manual is suggesting same length for all 3 servos). If not, then it adds usually another imprecision to the geometry. But again you can't do much about it.
  3. Try to set length of the 3 push rods when swashplate is at the center of its Collective Pitch travel. This can be determined by looking at the Anti-rotation bracket of the swashplate where swashplate should be approximately at the center. Adjust lengths of all 3 push rods by an equal amount (so that resulting length is same).
  4. Then use the Cyclic Leveler tool and fine-tune lengths of all 3 push rods (usually to be equal again). Subtrim (tuning) option should be still enabled.
  5. Mount the Rotor head and adjust length of 2 upper push rods that are connecting blade holders so that they are again equal and at the same time they are configured to reach 0°. This mean when you mount a main blades there and fold ends together, then both ends must be exactly at the same level. And this level should be held at any angle/position/rotation of the main shaft. If not, usually swashplate is not leveled perfectly precise or there is a big play in the mechanics.
  6. At this point, if there is no other imprecision in mechanic your mechanics is configured perfectly. Now you can untick Subtrim (tuning) option and verify if Positive and Negative angles between main blades are equal. If not, then open the Servos/Servo Travel Correction window and move with a sliders (usually it is enough to move with all 3 values by the same amount). If collective pitch is a higher at one side, move the pitch stick to that side (the lowest or the highest position). Then decrease 3 sliders equally to get the same collective pitch. When done correctly, you should get precise angles in both directions.