Approaches when VASI /PAPI not available
If your DME is working and the location of the DME is near the Aerodrome Reference point, then a 300 foot per nautical mile descent will keep you on the correct path.
If no DME then a pilot should be able to judge the descent (300 feet per nautical mile) by the apparent distance between the side markers ( In daylight) or the runway lights ( at night) .
At Broome in Western Australia, in the early days we operated Corporate Jets between Singapore and Broome in this manner, when the Broome runway was much shorter and VASI / PAPI was not yet installed.
Tmb