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Sunday, June 15, 2014

Nose and nose gear - part 9

Stashing the nose wheel (9.7 hrs)

Given the state of drafting technology of the late ‘70s and the complexity of airplane design, it should come as no big surprise when at times there are differences between the plans and reality. These issues would usually get fixed in later editions of the plans, but in the Long EZ’s case there is only edition #1, so you gotta work with what you’ve got. 

One such discrepancy seems to have occurred in the nose wheel retraction system department.

One could be excused for assuming that the nose wheel should retract completely into the fuselage, and indeed this seems to have been the designer’s plan.


Designer intentions


However, a little while ago I received an email from my friend Ary complaining that nearly 1/2” (1.5 cm) of his nose wheel stuck out below the fuselage. 


Ary's moment of discovery


At first, I thought he might have made some kind of mistake putting things together, but two weeks later, when I temporarily mounted my nose gear, I was shocked to see that my wheel hung about 1/2” below the fuselage as well.


I'm starting to detect a pattern...


Something was amiss, but I just couldn’t put my finger on it. Talking to everyone I know, I discovered that apparently everybody has had this happen to them (casting issue perhaps), but they all chose different ways to address it.


Burt Rutan's own plane


Yep! It's definitely a pattern!


Given that the gear leg follows the outline of the fuselage perfectly, I’ll just assume that this is the way things normally fit in a properly put together Long EZ, and move on to how to deal with it, but that really depends on what you want your nose to look like.

The way I see it, there are three principal ways of approaching this issue:

  1. Leaving it alone, and living with it.
  2. Adding a wedge to the bottom rear of the gear leg in order to correct the casting angle, and tuck the wheel into the fuselage.
  3. Cutting through the floor panel behind F22, and also raising the F22 notch in order to bring the whole leg (nose wheel included) further up into the fuselage.

Every option has its pros, and cons. 

Option 1 is the easiest, but it does not really address the issue. 


The half door does a pretty good job at covering the protruding wheel


Option 2 requires minimal effort, but it completely addresses the shortcoming. Though there might be some minor nose wheel geometry changes, the spirit of the plans is retained.


This plywood wedge is about to get covered in BID


Option 3 has major impact on many structures which will need to be reworked to retain strength, but it creates enough room to allow the addition of full size nose gear doors, hiding the nose wheel into the fuselage, and creating a perfectly streamlined nose.


Beasley's awesome engineering


Since I’m a sucker for good looking yet difficult things, I will go with the last one, hoping I won’t regret it.


Floor needs to be cut. It will be re-covered later.


Floor BID excised



F-22 notch raised about ¼" (6.4mm)


Surgery completed

Gear leg going roughly ¼" further into the fuselage




Nose wheel barely visible (at an angle)



Nose wheel completely contained in the wheel well (about 0.030" clearance from bottom)

Critical to the nose wheel ability to retract into the wheel well, is the proper geometry of the retraction mechanism. The normal hand operated system comes with precise measurements as to where the NG-3/NG-4 brackets should go, but since I am using a completely different system, these might not work for me.



Plans' directions

In order to make sure the electrical actuator will retract the front gear all the way up, I decided to do a little reverse engineering and the disregard all given measurements. I will test fit NG-3 while NG-1L is in retracted position, and make sure it extends/retracts properly, then I'll have a look at what my measurements turned out to be.






Looking for right NG-3 location




This geometry looked to be working quite well, even though the distance between the hinge point and the bracket bolt hole came up to about 6.15", which is much different from the 6.71" (± 0.05") the plans showed.


Your measurements might vary


I then added one layer of BID and flox.



NG-3 and NG-4 brackets getting floxed

Gear leg cured

Back side


When I get back from my trip, this leg will need a little cleanup, and new holes in NG-4 drilled to match the ones in NG-3.


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