page_title: Type 277 radar
section_title: Further testing
hierarchical_section_title: Type 277 radar / History / Further testing
caption_attribution_description: English: HMSC Copper Cliff, a Castle-class corvette, was used to test the Type 277 radar on escort vessels. Its Outfit AUJ parabolic antenna can be seen roughly centered in this image.
context_page_description: The Type 277 was a surface search and secondary aircraft early warning radar used by the Royal Navy and allies during World War II and the post-war era. It was a major update of the earlier Type 271 radar, offering much more power, better signal processing, new displays, and new antennas with greatly improved performance and had much simpler mounting requirements. It allowed a radar with performance formerly found only on cruisers and battleships to be fitted even to the smallest corvettes. It began to replace the 271 in 1943 and was widespread by the end of the year.
  The Type 271 was one of the first microwave frequency radars to enter service, when microwave electronics design was in its infancy. While it was still being fitted to escort ships during 1941 and 1942, great strides in technique were being made in cavity magnetron, waveguide, antenna design and general electronics. Those upgrades that could be easily combined with the existing systems became the 271 Mark IV models, while those that required longer to develop were originally known as the Mark V. Given the magnitude of the changes, in March 1943 the Mark Vs were renamed as the 277 series.
context_section_description: In March 1944, the 277 aboard escort carrier HMS Campania was used in a series of tests against the ship's Fairey Fulmar aircraft. Campania also carried the older Type 281 radar for air warning, which allowed the two to make comparative measurements. One problem with the 281 was that it did not offer altitude measurements, so a series of experiments started to use the 281 for tracking and the 277 for height finding. To do this, the 277 was locked in azimuth and then rotated manually through elevation to maximize the signal. The angle was then used to calculate the altitude.
  As part of these tests, a significant amount of attention was paid to the detection capabilities of the 277. This led to a series of probability charts which demonstrated that the detection was roughly linear with range for a medium-altitude target at 2,000 ft altitude, from 100 percent at ranges under 5 nautical miles (9.3 km; 5.8 mi) to about 80% at 10 nautical miles (19 km; 12 mi), to about zero at 40 nautical miles (74 km; 46 mi).
  As the Type 276 and Type 293 used the same fixed-speed 10 rpm mount, it had not been possible to perform significant testing of its ability to detect aircraft. Campania now turned its attention to the question of the best scanning speed, carrying out a series of runs at 10 and 16 rpm, and at a variety of much slower speeds using the variable-speed control. These revealed there was no obvious effect on detection probability when running at slower speeds between 2.25 and 2.5 rpm.
  Priority for the 277 was given to the larger ships, where the increase in performance was welcome, whereas the 271Q on the escorts was already performing adequately. In late 1944, the Navy became aware of the German efforts to fit the Schnorkel to their U-boat fleet. This led to the 277 being prioritized for the escorts to counter this threat.
  In September 1944, corvette HMCS Copper Cliff was fitted with the AUJ at the top of its 65 foot (20 m) mast, rather than the typical location on the bridgework. This gave it a radar horizon of 9.5 miles (15.3 km). In tests in Firth of Clyde and the North Channel, Copper Cliff was able to reliably detect a surfaced submarine at 11 miles (18 km) when only part of the conning tower was visible.  Against a Schnorkel, which was only 3 feet (0.91 m) high, the range was reduced to about 5.5 miles (8.9 km), and when closer to the surface it became lost in the radar clutter of the waves.
caption: HMCS Copper Cliff received one of the earliest fittings of the Outfit AUJ antenna, seen here facing away from the camera mid-way up the mainmast. Its relatively small size and convenient mounting is evident in this image.
exif: {"Image Tag 0x000B": "Windows Photo Editor 10.0.10011.16384", "Image Orientation": "Horizontal (normal)", "Image Software": "Windows Photo Editor 10.0.10011.16384", "Image DateTime": "2018:04:28 20:06:04", "Image ExifOffset": "2242", "Image Padding": "[]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "96", "Thumbnail YResolution": "96", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "4516", "Thumbnail JPEGInterchangeFormatLength": "5433", "EXIF DateTimeOriginal": "2018:04:26 18:07:02", "EXIF DateTimeDigitized": "2018:04:26 18:07:02", "EXIF SubSecTimeOriginal": "00", "EXIF SubSecTimeDigitized": "00", "EXIF ColorSpace": "sRGB", "EXIF Padding": "[]"}