<<Instead of slowing to 80 kt before opening the dump valve,  pull the pump breaker(s) and slow to 120 kt.   Open the dump valve and gradually let the speed bleed off.  Note when the nose gear down light comes on.   As the spring gets weaker you will have to go slower before the light comes on.   >>

 

This is a much better approach to testing the gas spring than using the nominal 100 lb check.  I started using this method about 7 years ago.  It is much easier to perform and gives a much better picture of the health of the system.  I can still lock the gear at 102 KIAS on a seven year old strut using the technique Bob describes.  One important variable in this installation is how much friction is present in all the nose gear linkages and pivots.  My CFI was testing another Lancair when something went wrong with the hydraulic pump.  He could not get a green on the nose despite all the aerobatics he tried.  The gear didn't collapse but hadn't quite made it over center either.  He stopped on the runway and pulled the link over center by hand.  Inspection revealed that the linkages were binding during travel.  In this case even the nominal 100 lb strut was not sufficient.

Chris Zavatson

N91CZ

360 std.