The purpose of this table is to determine the maximum allowed take-off weight from a slippery runway. It assumes that maximum reverse thrust is available in the event of a rejected take-off.
You have to start by knowing your airport and runway parameters and begin from 'dry' performance. This is then adjusted to allow for the actual 'slippery' conditions.
Two limiting weights will be calculated: the first to ensure that we can stop from V1 in the given length with the reduced braking action; and the second to ensure that the V1 is equal to or greater than the V1mcg. (Higher weights on a slippery runway may require a lower V1 to ensure stopping in the remaining distance.)
The 'slippery runway limited weight' will be the lower of these two weights.
a) Let's assume a sea-level airport with a 7,160ft runway. OAT is -6C. Reported braking action is POOR.
b) Start by calculating a 'dry' TOPL weight for the runway in question using the normal performance process. Let's assume this is 160,000lbs.
c) Enter the 'Weight Adjustment' table (the upper of the two tables) with the pressure altitude (S.L.) for the reported braking action (POOR) and the 'dry' TOPL (160). This yields a slippery runway weight adjustment of -18,300lbs, resulting in a 'slippery' TOPL of 141,700lbs.
d) Next we have to adjust the 7,160ft 'dry' available runway length for braking action and OAT. The note 2 at the bottom of the tables tells us to adjust the 'POOR' field length by +120ft for every 5C below 4C. Our OAT is -6C so we will add 240ft to the 7,160ft 'dry' length, giving 7,400ft.
e) Now we have to find the V1mcg limited weight. Enter the lower table with the adjusted field length (7,400) and pressure altitude (S.L.) for the reported braking action (POOR). This gives a weight of 179,300lbs.
f) The maximum allowed 'slippery runway limited weight' is the lower of 141,700lbs and 179,300lbs = 141,700lbs.
For another example, let's take an airport at an elevation of 5,000ft. The OAT is +9C, braking action is MEDIUM and the runway is 5,460ft long. 'Dry' TOPL is 146,000lbs.
Weight adjustment is -10,000lbs, giving a 'slippery' TOPL of 136,000lbs.
Adjust MEDIUM field length by -60ft, giving 5,400ft.
V1mcg limited weight is 134,500lbs. This is lower than the 'slippery' TOPL so the maximum allowed 'slippery runway limited weight' is 134,500lbs.