Tailwheel links
Tailwheel links
LAA Inspector Trevor Reed says set up that break-out tailwheel correctly…
T
he majority of taildraggers use tailwheels that are linked to the rudder, always moving with it, but automatically disengaging to allow full castering on the ground. Setting the tension in the spring linkage is critical for successful operation and there is often an inclination to set the linkage too tight, believing that taking out any slack will make it easier to steer on the ground. Such belief is erroneous – too tight a setting can induce serious problems such as the tailwheel being reluctant to unlock, which can overload the rudder bearings, leading to premature failure of the bearings and pins. If the system is very slack, it can give vague steering with the possibility of tailwheel shimmy. So, what we have to achieve is a setting that gives full movement of the tailwheel in normal operation, but which allows breakout of the internal locking mechanism when full castering is needed but is not so slack that shimmy is likely. However, it can be tricky to get it right and I am indebted to Mike Mold who has kindly sent me a link to a YouTube posting (https://youtu.be/QtokU8mIDQk) which gives the clearest procedure that I have encountered to date. It comes from the US, but our ‘country cousins’ do things like this so well! However, please don’t copy this chap’s jacking methods, you should never work on an unsupported aircraft; balancing the tail on top of a trolley jack is not acceptable! The method shown for setting the springs is very straightforward. Raise the back of the fuselage on a trestle, so that the tailwheel is clear of the ground and disconnect the links and springs from the arms on the tailwheel. Move the tailwheel gently one way, say to port, until you feel the resistance of the unlocking detent. Then, making sure that the tailwheel stays put, move the rudder in the same direction until it is fully deflected. Now, with your third hand, connect up the starboard spring so that it is just snug. The length of the tailwheel steering chains should be adjusted to get the desired tension by either removing or adding chain links and the screwable shackles should be secured by either split pins or locking wire. OK, that’s one side done. Repeat the process with the other side and the work is almost complete – you need to check a couple of things. Make sure that rudder travel, stop to stop, isn’t impaired by the spring set-up and that the tailwheel arm can’t approach an over-centre situation at full travel, i.e., it cannot go so far around that
28 | LIGHT AVIATION | April 2021
Above The correct setting of the tailwheel break-out spring tension is critical for good ground handling; too tight and it will strain the rudder hinges, too loose and steering can be vague and may cause shimmy. The use of asymmetric ‘Maule’ style springs also helps.
it will not return to straight ahead as the rudder is moved back to centre. And don’t forget to carry out a taxi test, with weight on the tail spring the geometry may change slightly, so make sure that the steering breaks only at full rudder deflection, just as it did when setting it up. Finally, make your logbook entries, including duplicate checks, as you have disturbed a primary control, and get your Inspector to approve your work.
Duplicate checks
Technical Leaflet TL2.05, explains all you need to know, as a pilot/owner, about carrying out one of the two independent checks necessary after a control has been disturbed. The rules are quite clear and unambiguous, if an engine or flying control has been disturbed, the checks are mandatory, and both should be carried out by LAA Inspectors. However, if only one Inspector is available, it is acceptable for the second check to be carried out by the owner/pilot or a licensed aircraft engineer. So, what should you do if called upon to carry out a duplicate check? Firstly, you must remember that
