page_title: MD Helicopters MD 500
section_title: MD 520N
hierarchical_section_title: MD Helicopters MD 500 / Design and development / MD 520N
caption_attribution_description: English: A MD500N helicopter (G-SMAC, built 1992) at Kemble Airfield, Gloucestershire, England.
context_page_description: The MD Helicopters MD 500 series is an American family of light utility civilian and military helicopters. The MD 500 was developed from the Hughes 500, a civilian version of the US Army's OH-6A Cayuse/Loach. The series currently includes the MD 500E, MD 520N, and MD 530F.
context_section_description: The MD 520N introduced a revolutionary advance in helicopter design, dispensing with a conventional anti-torque tail rotor in favor of the Hughes/McDonnell-Douglas-developed NOTAR system. Exhaust from a fan is directed through slots in the tailboom, using the Coandă effect to counteract the torque of the main rotor, and a controllable thruster at the end of the tailboom is used for yaw control. Because the fan is enclosed in the tailboom, tail rotor noise—the major source of noise from most conventional helicopters—was significantly reduced. It also eliminated the vulnerable exposed tail rotor blades, eliminating the possibility of persons being injured or killed on the ground and the cause for many confined area maneuvering accidents.
  McDonnell Douglas originally intended to develop the standard MD 520N alongside the more powerful hot-and-high optimized MD 530N; both were launched in January 1989 and were based on the conventional MD 500E. The MD 530N was the first to fly, on December 29, 1989, and the MD 520N first flew on May 1, 1990. Development of the MD 530N was suspended when McDonnell Douglas decided that the MD 520N met most customer requirements for the 530N. Certification for the MD 520N was awarded on September 13, 1991, and the first was delivered on December 31 that year.
  In 2000, MD Helicopters announced enhancements to the MD 520N, including an improved Rolls-Royce 250-C20R+ engine with 3% to 5% more power for better performance on warm days, and changes to the diffuser and fan rigging, also increased range.
caption: A NOTAR MD 520N
exif: {"Image Make": "Canon", "Image Model": "Canon PowerShot S3 IS", "Image Orientation": "Horizontal (normal)", "Image XResolution": "180", "Image YResolution": "180", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2006:06:18 13:30:59", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "196", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "180", "Thumbnail YResolution": "180", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "5108", "Thumbnail JPEGInterchangeFormatLength": "4199", "EXIF ExposureTime": "1/640", "EXIF FNumber": "4", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2006:06:18 13:30:59", "EXIF DateTimeDigitized": "2006:06:18 13:30:59", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "3", "EXIF ShutterSpeedValue": "149/16", "EXIF ApertureValue": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "29/8", "EXIF MeteringMode": "Pattern", "EXIF Flash": "80", "EXIF FocalLength": "208/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2816", "EXIF ExifImageLength": "2112", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "Interoperability RelatedImageWidth": "2816", "Interoperability RelatedImageLength": "2112", "EXIF InteroperabilityOffset": "2772", "EXIF FocalPlaneXResolution": "112640/9", "EXIF FocalPlaneYResolution": "2112000/169", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Manual", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard"}