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The Boeing MD 520N is an advanced design as it dispenses with a conventional tail rotor in favour of the McDonnell Douglas' developed NOTAR (NO TAil Rotor) system.
McDonnell Douglas' original intention was to develop the standard MD 520N alongside the more powerful hot and high optimised MD 530N (both were launched in January 1989). Both were based on the MD 500. However the MD 530 N was suspended when McDonnell Douglas decided that the MD 520N met most customer requirements.
Development of the revolutionary NOTAR system dates back to late 1975 when Hughes engineers began initial concept development work. In December 1981 Hughes flew an OH6A fitted with NOTAR for the first time. A more heavily modified prototype demonstrator first flew in March 1986 (by which time McDonnell Douglas had acquired Hughes Helicopters).
Although the concept, known as the Coanda effect, took some time to refine, the NOTAR system is quite simple in theory and works the same way as a wing develops lift to provide directional control. Low pressure air is forced through two slots on the right side of the tailboom, causing the downwash from the main rotor to hug the tailboom, producing lift, and thus a measure of directional control. This is augmented by a direct jet thruster and vertical stabilisers.
The NOTAR system offers a number of benefits including far lower external noise (at the time of writing it was the quietest certificated helicopter in the world), increased safety due to the removal of the tail rotor, improved handling and performance, reduced vibration and easier maintainability.
From the 1997 merger with Boeing they were Boeing products and since 1999, the Boeing Company?s commercial light helicopter product lines, were purchased by MDHI. |
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| Seating (normal) |
3 |
Max Takeoff (lbs) |
3,350 |
| Seating (maximum) |
4 |
Certified Ceiling (ft) |
16,300 |
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| Engines |
Rolls Royce 250 C2-R |
To (Sealevel, ISA Temp) (ft) |
- |
| Output lbs ea. Flat Rating |
435shp |
Landing Distance (ft) |
- |
| Maximum Mach No. |
- |
Max Range (fuel) (nm) |
233 |
| High Speed Cruise (Kts) |
135 |
Max Range (payload) (nm) |
233 |
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| Flight Time 300nm |
- |
Flight Time 1000nm |
- |
| Flight Time 600nm |
- |
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| External |
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Internal |
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| Length (ft) |
25.50 |
Length (ft) |
9.00 |
| Height (ft) |
9.60 |
Height (ft) |
5.00 |
| Span (ft) |
6.20 |
Width: Max floor (ft) |
4.40 |
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