We've known for years that the retractable nose gear assemblies on our Lancairs require careful inspection and maintenance--perhaps more that any other component of the airplane other than the engine! I was therefore surprised to read on LancairTalk about a Legacy owner that just discovered a problem with bronze bushings provided in Legacy kits and retrofitted to IV-series aircraft under Lancair SB077-0518. As we have written for more than a year now, these bronze bushings are not suitable for the application and should be replaced as soon as possible. They have been responsible for more than 10 nose gear collapses in the Legacy and IV fleets over the past two years. Repair costs for almost all these incidents has been north of $30,000, and required as much as a year to repair/obtain the needed parts.
There are two possible ways to improve the nose gear retraction assembly, and all start with a detailed inspection, including some dis-assembly, to verify the condition of the parts. A visual inspection is not acceptable for assessing component wear as they remain under high loads until the gas spring and hydraulic actuator are disconnected.
Lancair Incorporated has produced Service Bulletin (SB078-0722) to address this, and I strongly recommend you visually inspect your IV or Legacy IAW the SB immediately to determine if you have bronze bushings installed. (Availalble on-line at www.lancair.com; see "NEW SERVICE BULLETINS at the bottom of the opening page.) If you have these parts installed, take immediate action to replace them. If you don't have bronze bushings, perform the specified inspection at your next condition inspection.
SB078-0722 specifically details the installation of improved lower drag links, available from Roxanne Zavala at Lancair, Inc, that correct an engineering design issue with the original configuration and should provide a permanent fix for most causes of nose gear collapse that we've seen. (Broken motor mounts are the other major cause of collapse, and are not corrected/affected by this modification.)
There are two considerations to be aware if when ininstalling the new Lancair lower drag links. Some Legacy kits were produced with lower drag links having a pivot-hole center-to-center distance 1/8" shorter than the standard parts. This is a critical distance and affects nose wheel geometery and operation. Measure the new parts you receive to be sure the hole-to-hole distance is exactly the same as your existing parts. The second gotcha is that paragraph 7.2.3 specifies a torque value of 90-100 in/lbs for the new pivot bolt that's provided. This much torque will lock the upper and lower drag links together and prevent nose gear retraction. The correct proceedure is to tighten the bolt until slight resistance is felt in the pivot between the upper and lower link. (There are two such bolts/links.) Secure the bolt with safety wire per the SB when the links pivot with minimum resistance.
A second way to replace installed bronze bushings, or to correct wear in the pivot when no bushings are installed, is to carefully bore the pivot holes in both the upper and lower drag links to accomodate larger close-tolerence bolts (2), and install them with castle nuts and cotter pins to allow the pivot joints to flex freely. This will require complete removal of the upper and lower link assemblies, and boring in a machine shop. Close tolerance AN5 bolts will work for original/unmodified struts (no bushings ever installed); AN6 bolts will be required if the lower drag links now have bronze bushings installed.
I recommend installation of the new parts IAW Lancair SB078-0722 vice using the larger bolts. It's the better engineering solution...