Much of the craft of prototyping is interpreting what parts come from the line drawings. One can get fairly detailed with the model if all the elements pictured are used ,but this is up to the modeler. As always the line drawings are the beginning to the end. Some line drawings are not as accurate and need some tweaking. This is all part of the fun… I’ll attempt to show you how I make models. It is hard to articulate carving. these models serve no real purpose other than to remind one of their job or maybe just the love of collecting. This project is inspired by the aircrafts look Tarmac apeal and the versions which can be made from one set of templates. 
I like to use two or three good angles of the subject to give the minds eye basic information on shape. This is a good photo.As always I’ll post as I make progress on this helicopter.I might as well make the 6 seat version while I’m at it.All I need is the side view and another jig as the skids are longer. Also the door detail will fit nicely onto the 520. Then you compare the two as the project progresses. 
I use brazing wire to work up the landing struts so I can get a hotter soldier joint.It is plain to see that as the model finishes the wire will have a fairing as per the referenced photo. There are three templates minimum in any model project fixed or rotor the early on in fabrication is the same. 
Most who have soldiered know that if you don’t make a jig things tend to be rather difficult and to be fun there shouldn’t be a lot to set me back.So this jig will make a dozen or so skid sets. 
I like to apply the detail to help carve the model after all it is really hard to position carving strokes without them. 
Art, do you use a band saw or scroll?
Watchmann I use a ( Rockwell Blade Runner ) with very fine wood blades. I use a scroll saw sometimes and belt sander to sand the top view. I use a coping saw in some cases. Thanks for your intrest.
Thanks Art. That’s a nice looking machine.
Thank You Watchman. 
Progress
Impressive work as always!
There is a lot to straighten out on this project but it’s ready to begin carving. The rotor blades are sub flooring from a 100 year old home. 
I think I may work up the 600 version to have in the cue. MD has a line of NOTAR helicopter to collect. 
There is one more in the series of NOTAR helicopters but the MD 900 explorer is so much different from the original airframe which was the Cayuse or HUGHES 500 C This 600 is as fine a look as I’ve seen in along time. I have yet to find a decent plastic model in a scale that is workable. 
You can see the difference in both aircraft. The MD- 600 version has many of the same elements as the 520.difference being length and a 6 blade rotor hub. 
This project has been interesting as I didn’t know how powerful these Notar tail booms work to cancel out tourque… 
This block model was based on a side view. Many of the parts from the other model would prove useful on the latest 6 seat version you see here. 
The sides of the rotor housing do detach from the model as its easier to shape the fuselage only to be glued back later. [URL=http://s1028.photobucket.com/user/ArtworksIII/media/20150218_114310_zpsqqfmbfod.jpg.html][IMG]http://i1028.photobucket.com/albums/y342/ArtworksIII/20150218_114310_zpsqqfmbfod.jpg[/IMG
I’ve only see one of these fly over never got out to Felts Field to see who owned the machine. Still have the MD Explorer in the work if I can figure it out. There is also a tilt rotor WIP up and in coming. Stay tuned. All Models you see are proof of concept. The templates are sound and able to create a model.