Originally Posted by
DFS346
Many thanks. I am writing a book on Northwest Flight 305 of 11.24.1971. One of my research tasks was to determine the margin of uncertainty of the three DME reports (14m south of SEA, 19m south of SEA, and 23m south of PDX. I had been wondering why they reported whole miles and whether the instrument precluded a more precise reading.
Don't know of the event but are the reports you refer to recovered data from a flight data recorder or radio position reports from the crew?
If its recovered data then you would expect the accident report to give the data as accurately as it was recorded - i.e to tenths if the display showed that.
If it's a radio transcript then it is unlikely that pilots would report their DME range in units of less than a mile, even if that was displayed to them. We'd round up or down to the nearest whole unit (or perhaps a half if it was a very short range - eg on short finals where the half mile might be relevant).
OH