If you should happen to work in remote areas, onto beaches, undeveloped or compromised strips -or perhaps be tasked with a disaster recovery airlift, you may have need of a convenient means to establish the likely available length of a selected landing area. This table may help:
To use: If uncertain of LDG Distance Available, or if LDA may be compromised by obstruction or natural events, you will need to first fly down the strip at a known (GPS perhaps) Ground Speed and establish a time in seconds from crossing the upwind THR to the start of the LDA. Reference to the table below will give an approximate LDA. Always round your timing down to the nearest whole second and your GS up to the nearest 10Kts. This will give you the most pessimistic (shortest) LDA, which is the most likely to keep you safe!
For example, at 116Kts GS for 8.6 seconds, you would read the 120Kts line across to the 5sec value and add the 3sec value to that, to establish an LDA of 494m. If that value is sufficient for your aircraft at its current weight and with strip, slope, condition (wet/dry) and wind factors considered, you will be able to make a decision on whether to commit to an approach or not.