Chapter 13: Nose Bumper


 

If you study pictures of a gear-up landing, you'll come to four conclusions right away; (1) asphalt is the best sandpaper ever made! (2) the plans-built nose puck doesn't do diddly; (3) there's nothing substantial enough to protect the NG5 backing plate, screws, and nose gear strut from being irreparably damaged; and (4) it's true, "there are those that have and those that will."

 

Let's look at the dynamics of the gear-up landing.  The nose puck either departs the airplane immediately or gets ground away completely within the first few feet of the skid.  The wood puts up a good fight, but it doesn't last long.  The asphalt grinds away the bottom skin and urethane foam in the blink of an eye.  As the skid continues, the F0 and NG30 bulkheads are ground down.  The NG5 backing plate makes contact with the asphalt as the plane slides to a stop.  If you're lucky and its a short skid, only some of the backing plate is ground away and there's still enough of the screw heads still holding the backing plate to the nose gear strut.  If you're unlucky and it was a long skid, the backing plate is gone, the screw heads are gone, and the nose strut was grounded down big time.  The damage is done and you're not flying home today.  In fact, you'd be lucky enough to be capable of taxiing to a hangar to effect repairs. 

 

If you're going to fly away from a gear up landing, the nose gear strut must stay attached to the NG6 nose casting and the structural integrity of the NG5 backing must be maintained.  The only way for THAT to happen is to keep the screws and the backing plate from ever making contact with the asphalt.  If there's no damage to the backing plate, there won't be any damage to the screws.  But lose the backing plate, it's a good bet the screws are gone, too.

 

So I made a nose bumper of my own design.  As shown below, it features a primary, horseshoe-shaped skid plate under the nose cap and a thicker NG5 backing plate.  The primary plate is made from 3/8th-inch-thick aluminum plate, which should survive an extended skid.  It is bolted from inside the nose cap and alongside the NG30s.  I bought one of those white plastic cutting boards at Walmart.  I'm told the material is Ultra High Molecular Weight (UHMW) PolyEthylene (PE), or some other high density PE. I shaped a piece of it to fit over the primary plate.  It is held onto the skid plate with screws.  Although its job is to be the "rubber bumper" for parking nose down, it will provide the initial (and most likely "brief") skid protection as well.  The NG5 backing plate was made from thicker aluminum, too.  The screws are counter-sunk deeper into the material so that the material above the screw heads is sacrificed during a prolonged skid.  These diagrams are not to scale, but the other pictures should convey the idea.  Note that the primary plate is threaded and is bolted from the inside.  In this manner, the plate stays attached even as the plate is ground away!  Same idea for the NG5 backing plate.

 

  

I - Like - It.


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