Thread: Futaba GY401 Problems - In heading hold mode the servo is moved to extremity of range

You don't need step 1. You need to power up in hold mode. You are initialising inrate mode which is incorrect for a Futaba 401 servo. (Although it works on my gyro). The red led should be on all the time after initialisation.

Hi and welcome to the forum ... What tail servo are you using ? With 401's I have always powered them up in HH mode and never rate mode .

Have you tried another tail servo or gyro just to rule one of the other out ?? .. When in HH mode when the tx stick is moved the servo should creep one side or the other and if you let your stick back to centre the tail servo should stay at the extreme last stick position until an opposite stick movement in put in or until the heli is moved to counter act the initial stick input. power it up in hh mode and dont touch anything .. if the servo moved to one side or the other with no stick inputs put in then its lost its calibration or something else is up with it .. hope some of this helps

Sounds like its lost calibration ... Oh and what transmitter are you using ? as it might be your transmitter might want re-calibrating ..Certainly sounds like one or the other. Try reversing the gyro and see if the servo moves the same way but in the opposite direction . I had this a while ago and it was calibration lost and it ruled out the Tx

Originally Posted by tommcdonna

If I flip the dip-switch on the gyro to reverse it the servo moves from one extreme to the other. 'Creeping' behaviour is reversed.

This points to loss of calibration in gyro?

Certainly sounds like it unless anyone else has any other ideas . Sounds like the same thing as happened to one of mine a while ago. Never had to send a 401 back but I would think it would be easier to buy a second hand gyro off here as they are going cheap enough for ones alot better spec than a 401 . You could pick a 720 up for about £40 which imo is alot better gyro .. Just ring ripmax and ask them how much it will be roughly if its just to re-calibrate and check over and then weigh up how much its going to cost to say buying another gyro .. I am selling some 720's if your interested .. I know shameless plug while I am at it lol.

Creeping when in HH mode is normal. If you hold the rudder stick just a smidge off centre in either direction when the heli is on the bench, you should see the servo creep across to its full limit, and then you can make it go back the other way with the stick as well.

You should always start up a 401 in HH mode.

I'd be very surprised if there's anything wrong with it at all - they are bullet-proof really.

You should get it checked out by a local experienced flyer if you're really uncertain. Where abouts in Suffolk are you?

Back to basics - make sure the tail control is the right way around on the transmitter and make sure the gyro is sensing the correct way and adjust on the gyro body via the little switch if necessary.

Left ruder stick should pull the tail to the right (i.e. nose of the heli goes left).

Once the stick is going the right way, look to see which way the servo arm travels when you apply left rudder. Then hold the heli by the head button and sharply twang it to the right by the tail and watch the tail servo. It should try to compensate for the right turn and apply left rudder for you, so the servo should move sharply the same way as when you tested it for left rudder.

Hey.

Have you tried toggling the gain switch quickly 3 times, going from HH mode to rate mode, ending with the switch in HH mode? This teaches the GY gyros their neutral position.
The above can be used when trimming the tail to fly straight in rate mode when adjusting transmitter trim, but its best to adjust tail pushrod length.

All GY gyros like to be setup in rate mode first, adjust tail pushrod length to attain a trimmed tail rotor in rate mode. Them do the above gain switch toggle, to train neutral position ending in HH mode, leave the switch in HH mode and go fly with a great tail.

As already said, only power up the model in HH mode and then flick into rate mode if required.
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Does the red led come on when you power up in heading hold? Every gyro has different maths behind it and when the heli is on the ground the tail cannot rotate and so the gyro behaves in a different way on the ground to in the air. Some gyros do creep when on the ground in heading hold but my Futaba 401 does not. If the gyro is working correctly it should not creep. Creep is an error condition as the gyro thinks that the tail is moving and is sending a signal to correct the drift. It is possible that a gyro will hold correctly in the air even if it creep on the ground. You could test this by holding the heli and turning it in the direction to counteract the drift. If you have to keep turning the heli then the gyro hasn't initialised properly. This could be because you are not sending it the correct middle stick value. The 401 looks and remembers the yaw stick value during initialisation and as the heli is stationary it uses this vale as the zero rotation value. This value can be varied by a few clicks either way, but if you go too far the 401 will refuse to accept it and fail to keep the led on and give a fast creep.

The way a gyro works is fairly starightforward in principle. First of all it is not really a gyro, all it does is measure how fast the tail is turning. The sensor that does this is not very accurate and varies with age and temperature. To overcome this every gyro goes through an initialisation process which measures and remembers the output from the sensor. This is then remembered as the output for zero rotation. All gyros also have the ability to measure their temperature and as temperature changes after calibration they are able to adjust the expected output for zero rotation.

This gives the basic rate mode. A servo output is given to the tail which is proportional to the tail rate. For hold mode the gyro works out the angle of rotation by multiplying the rate by the time. Just like distance = speed X time. It then applies an opposite force until the angle is back to zero.

It does sound though, as your gyro is secondhand that the sensor has been damaged in a crash and that the gyro software is unable to complete calibration as the sensor output is probably out of range. Try the cheap Assan gyro for £10.