Yesterday, on the approach/landing phase, I noticed that I did not get my usual three-green lights.  For that matter, I did not get any green lights at all.  I broke off the pattern to troubleshoot.  With the landing gear switch on the down position, the hydraulic gear pump remained silent...  :-(    Time for the emergency gear extension procedure.  As soon as the pressure release valve was opened, I immediately got the green lights for the mains, but the nose gear light remained off.  I jerked the plane around a bit, with stuff from the baggage compartment flying around the canopy and I eventually got all my three green lights!  Landing was uneventful.

Upon close inspection, I noticed that the 'gear-down' relay was very, very hot..too hot in fact to touch.  'Gear-up' relay was warm but not hot.  My lancair has over 720 hours now and these relays are the ones that came with the kit.  I just ordered a pair from Lancair and also ordered a new continuous relay.  I decided to replace all my relays, except for the starter relay which was replaced recently.

So, anybody else had this problem before?  Should we be replacing there relays at 500, 600, or 700 hours? 

Rick,

 

As Chris says:

 

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

 I haven't had this problem, but I would suggest opening up the old relay to
see what exactly failed.  Did the coil fail?  Did the plunger get stuck?  Was
the problem actually in the pump motor?  I did find a brand new relay of this
type with a broken coil wire (manufacturing defect).  I still have it on
display here in my office.
  Chris Zavatson
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

We have inquiring minds.......................

 

Side note----

 

The most frequent cause of an intermittent relay going bad is its' selection for a long time - somehow, someway.  The Lancair wiring diagram and/or certain improvisations in the wiring have led to many relay failures.  Some have chosen to wire the relay coil thru some breaker that handles multiple circuits - thus, when the motor breaker is pulled for some service reason, the relay coil power remains engaged.  Others may not remember to pull the relay breaker whenever they pull the motor breaker.  In such cases, the pressure switch may be calling for the pump, thus selecting the appropriate relay (usually "down", sometimes "up") with no relief since there is no power to the pump and no indicator light that the relay was selected.  Sometimes this has occurred when pilots think the frequent activation of the pump is unnecessary because the dead band of the pressure switch is too narrow, so the  motor breaker is pulled during flight for long periods, yet the relay remains selected.  Master switch on testing whilst on jacks may also cause this problem because power still reaches the relay if the pressure switch and the gear switch are calling for pump activation.  Once overheated the coil wiring insulation may melt, re-congeal around the plunger and this can jam or otherwise cause problems with the plunger (stickiness, etc.) ultimately leading to relay failure.

 

The only way to fix these problems is to wire the relay fuse or breaker after (on the output side) the motor breaker - thus, when the motor breaker is pulled, all power to the hydro system is removed. Period.

 

Another LML contributor is correct in that there is a temperature driven breaker in the motor itself - thus the motor may stop but the relay is still selected.  This means there are other problems in addition to the intermittent relay being powered for long periods.

 

Replacing the relays is not the solution but only fixing symptoms.