Avro Lancaster pagesAM 05/07/2012 16:29 Page 117
TARGETS
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3. Photographs of P.P.I.† Presentation During several flight tests, photographs were taken of the P.P.I. tube showing different targets at various ranges, a special attachment being used for this purpose. Photographs of the gap and backward presentation were also taken and these are shown on the attached photographs [not included here]. For reasons of security, no annotation is shown on the photographs, the references being as follows:– Fig. 1.Birmingham 9 miles ahead; Coventry to the left. Fig. 2.Birmingham dead ahead, 20 miles, Coventry left 13 miles. Fig. 3.Leicester 6 miles (10 mile range). Fig. 4.Leicester 6½ miles (10 mile range). Fig. 5.Leicester 4¾ miles (10 mile range). Fig. 6.Showing gap behind and in front of A/C.
4. Summary of Flight Tests 4.1. The first flight test was carried out on the 24th October in the immediate vicinity of the Bristol Channel. Maximum range appeared to be good, towns showing up at 30 miles, but a gap, extending from 0–7½ miles, was observed in a dead ahead position. Returns were observed in a reciprocal heading (i.e. behind aircraft) between 0–4 miles. Further flights were carried out on the same day over Leicester, Northampton, Reading, and Oxford and on each occasion the target disappeared at a range of 7½ miles. Both these flights were carried out at 20,000 feet. 4.2. Owing to the wooden structure of the nose it was decided to fit copper sheeting on the floor immediately above the scanner in an effort to simulate conditions obtaining with a standard metal nose. On a subsequent flight the gap was still visible at the same range and no improvement was observed. 4.3. The standard 7º wedge was replaced by a 12º wedge, but when this was fitted in position, it was discovered that the corners of the scanner fouled the perspex cupola. In order to overcome this difficulty, the corners of the scanner were cut off, and this resulted in a decrease in the gap width of approximately ½ mile. 4.4. It was then decided to fit a copper tilting plate, 17 cms. wide, immediately under the existing tilting plate, the angle of tilt of the former being about 15º greater than that of the existing plate. During the flight test which †
Plan Position Indicator