Nose Strut Experience
 

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Nose Strut Experience

After my fourth nose strut replacement I think the time has come for me to share my experiences. I lay the blame for these failures at my own doorstep. Here is why....

The original Brock parts was of good quality, but the MKNG-15 was made with smaller attachment ears that would eventually start crack lines caused by the stress of over tightening the 4 AN4 Bolts that secures the MKNG-2. The MKNG-2 as supplied by Brock was of good quality and sufficiently thick (.090") 4130.

After my landing accident on March, 2006 I replaced the manual nose gear extension with a Jack Wilhelmson Nose Lift. This is a great piece of work and worked well. My only concern was the replacement MKNG-2 with the "foot" that Jack supplied was thinner and made out of Stainless Steel. Tightening the 4 AN4 blots revealed distortion and bending of the plate, but I took it that this is how it should be. I also omitted the retaining bolt that is supposed to be installed cross wise through the MKNG-15 ensuring retention of the assemble to the strut should the epoxy/flox bond come loose. This is suggested in the installation instructions that came with the Nose Lift. It just didn't seem right and It bothered me that his bolt would cause the strut to split. I left it out.

This is then the reason I lost the nose wheel as described in my incidents section.

Here is a picture of what the strut looked like after the lost nose wheel incident. Tarmac is a great piece of sand paper.

So back to FeatherLight and getting a new strut and this time I was determined to do it right as suggested by Jack and install the cross bolt to retain the MKNG-15.

For a couple of flights all went well until some day taxiing to my hangar I went over a rough bumpy patch. On the rebound the nose gear recoiled back to it's fully extended stop and I heard a loud crack. On inspection I found that he strut was split from the hole where the retention bolt was to almost the MKNG-3 & 4. see picture. Luckily I hadn't painted the strut yet and the crack was easily seen through the BIB layers.

So, back to FeatherLight for yet another strut. This time round I was not so lucky and the strut went missing in action and my impatience forced me to make my own strut. I could  not get S-glass and I opted to use normal UNI as I still had some left over. This strut should not split since there is a 10% cross weave in the UNI.

The lessons learned got me into the following installation method.

  • Only fully fix the MKNG-15 & MKNG-2 assembly after making sure that you have the prescribed castor angle as per Chapter 13 page 1. This angle should be between 82 and 87 degrees to make provision for a loaded situation.
  • Put the retainer screw at the back of the MKNG-15 and only tap it to a maximum depth of 1/4"into the strut.
  • Use the original Brock MKNG-2 that is made out of 4130 Chromalloy. I made a foot out of 1/2"alluminium and screwed it from the inside of the MKNG-2 with counter sunk 3/16" screws.
  • Fill the gap between the MKNG-2 and MKNG-15 with flox and encase the AN4 Blots with flox as well.
  • Ensure that you have at about 9 Lbs side load force measured at the tire extremes to twist the pivot. Proper pre-load will dampen shimmy.

After a severe shimmy incident I can gladly confirm that the above described method held together well.