In a message dated 2/5/2006 12:14:19 A.M. Central Standard Time, marv@lancaironline.net writes:

Gerard,

 

The answer to the first question is no.  The ordinary INTERMITTENT DUTY relays can give you years of trouble free service.  This is true if your aircraft landing gear system is wired as suggested by Lancair (See the Pilot Operating Handbook or construction manual) and the operational directions are followed:  If the master switch remains on and power is removed from the pump motor circuit, then power must also be removed from the relay coil circuit - both circuit breakers must be pulled (as identified in the circuit diagram), especially the relay breaker. 

 

The reason for this is that the relays are intended for short term use only, I.E. the time required to cycle the gear.  If left selected for extended periods of time the relay can be damaged internally and subsequently not operate properly.  This can happen if only the motor breaker is pulled while the main bus remains powered, thus either the up or down relay can remain powered, depending on the gear switch position, after the appropriate pressure switch calls for hydraulic pressure.  There will be no panel indication since the "transit" light is powered from the motor power circuit, not from the relay coil circuit.  Pilots can cause this by only pulling the motor power breaker to stop pump blips, whether in flight, on the ground taxiing or testing some electrical system component while the aircraft is on jacks.   

 

Slow to 87 KIAS.

Gear Switch Down.

Both Motor and Relay Breaker Pulled.

Gear Dump Valve Open.

Yaw if necessary to lock mains.

 

Once all electrical power is removed from the gear system and any hydraulic pressure is removed by the cross feed dump valve the gear will free fall with the nose gear assisted by the 100# gas spring.  As Lancair suggests, the emergency extension procedure should be tested in flight monthly.