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McDonnell Douglas 520N
in the colour scheme of 'WINWARD AVIATION', Hawaii, USA.
Copyright Ian Standfast 1999
Designed by Ian Standfast 25.8.99 using Abacus' AF99.
Moving parts produced using Konstantin Kukushkin's superb Aircraft Animator.
The Hughes 500 shape has got to be one of the most recognised (along with the JetRanger) by most people. Developed for the US Army as a Light Observation machine in 1961, the 500 is one of the most compact machines relative to it's size and capability. This machine is regarded as the E-type Jaguar of the helicopters due to it's speed and maneuvrability and is a real favourite with the pilots who fly it.
The most recent development of the 500 has resulted in the 520N and the 600N. Both helicopters use the NOTAR system of torque management and this has resulted in yet another very distinctive looking machine, the most obvious features being the rather stout looking boom and the absence of a tail rotor.
I do not know a lot about the NOTAR system, so I have included and extract from an article by Derek Jones in the January 1998 issue of Pilot magazine about the stretched version of the 520N, the 600N
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The first commercial application off the NOTAR (no tail rotor) concept was the McDonnell Douglas MD520N. Introducing this feature completely altered the shape of the rear fuselage and boom, but not the cabin, which retained the two seats in the rear.
Why replace the tail rotor anyway? Well, tail rotors are vulnerable to damage from flying debris and hitting obstacles. Unwary people are prone to walking into them,and they are inherently noisy. Designers also look for ways to minimise the power wasted on driving them.
The problem is that they are relatively efficient at the job of providing an anti-tourque force. Any concept which reduces the size o the tail rotor, like the Fenestron system, is less efficient in the hover, simply because it has to accelerate a smaller mass of air to higher velocity to achieve the same effect.
The notar idea is clever in that it makes use of the downwash from the main rotor to generate a sideways force from the tail boom. Air from a fan driven off the main gearbox pressurises the boom, and some of it exits from two longitudinal slots on the right side of the boom. This keeps the airflow attached and generate sideways lift, rather like a swinging cricket ball, shiny on one side and rough on the other. On the MD600N, the roughness is achieved by a strake on the left side of the boom which causes the air to break away. Thus, higher power generatesmore downwash and more anti-torque force - clever. The pitch of the fan is controlled by the pilot's yaw pedals, so at low power, less air pressure is generated by producing less force.
Fine control of heading in the hover is provided by a rotating can at the end of the boom, also connected to the pilot's pedals. Rotating the can opens ports in the side of the boom, thus varying the thrust.
In forward flight the airflow does not flow around the boom, so most of the anti-torque force has to be provided by the twin fins.
All this sounds rather long-winded, but no doubt covers only a fraction of the developement effort in actually making it all work in an integrated fashion.
Derek Jones
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INSTALLATION, this ship is for FS98 only.
This aircraft comes already configured for FS98. Unzip the file and place the aircraft folder in the aircraft directory of FS98.
The MD520N comes with it's own panel and sounds.
This ship does have a higher forward airspeed than the default Bell206. However, the earlier airfile had a tendancy to let the nose rise on a rapid lowering of the collective at high forward airspeed, and this could not be corrected until the AS had dropped below about 120kts. I have managed to stop this happening, but only at the cost of some of the additional forward airspeed I had originally added. So this file is a bit of a compromise, but it still handles reasonably well, and you can still travel faster than the default FS JetRanger.
I have modified the air file to remove the unrealistic cross couple effect between the lateral cyclic and yaw pedals. (The original Bell model in FS98, although very good, produces a very unrealistic fuselage roll when pedal is applied in either direction.) However, here is a downside to this, you will find that you have a lot more yaw authority in the hover, and it only diminishes at speeds approaching 60kts, but I find this more realistic. So you may end up doing a bit of a Huey shuffle on your first few flights, but you should get the hang of it pretty quickly. The only real problem with the airfile is that if you hold in huge amounts of pedal for a few seconds, the ship will go into an irrecoverable rotation, then break. For the best handling, I suggest you turn all your control sensitivities to their full value, and reduce the null zones to their minumum.
Unlike some of my recent ships, you cannot do a simulated shutdown, as it takes a lot of parts to duplicate the static elements, but you can run down to ground idle and see the blades become visible.
All my ships are available on Keiths Virtual Helipad)
http://members.aol.com/keitht777/helipad.html
If you have any comments about any of my aircraft,
Please E-mail me at
106071,2027
or 106071.2027@compuserve.com
Ian Standfast
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Copyright C. Ian Standfast 1999
Legal stuff:
THIS IS FREEWARE.
THIS AIRCRAFT IS THE PROPERTY OF THE AUTHOR, AND CANNOT BE
RE-SOLD OR PACKAGED WITH ANY PRODUCT FOR SALE, WITHOUT THE
EXPRESS WRITTEN PERMISSION OF THE AUTHOR. THIS TEXT FILE MUST
ALWAYS BE TRANSPORTED WITH THE AIRCRAFT IF IT IS RE-ZIPPED.
THIS AIRCRAFT MUST NOT BE UPLOADED TO ANY FORUMS OR WEB SITES
WITHOUT THE PERMISSION OF THE AUTHOR.
THE AUTHOR IS NOT LIABLE FOR ANY LIABILITIES THAT YOU MIGHT
INCUR AS A RESULT OF USING THIS PRODUCT. YOU ASSUME THE RISK
OF USE.
