As has been already mentioned, the amount of sick leave needed to get to long-term disability is different for each pilot and is based on many variables. The following is just one example:

Assumptions
-12 year Captain payrate: $259/hr
-75 hours of monthly pay
-Excess disability insurance benefit (Additional 20%): $300 per week
-Maximum Washington State STD benefit (12 weeks): $1,500 per week
-Monthly income: (75*259) = $19,425
-40 days of vacation value cash out: 140 hours
-STD begins 30 days after injury

Month 1: $19,425 (75*259)

Vacation used: 75
Vacation remaining: 65
Sick Leave used: 0

Month 2: $19,425

STD benefit: $6,800
Income shortage: $12,625 ($19,425 - $6,800) or 49 hours of vacation
Vacation used: 49 hours
Vacation remaining: 16
Sick Leave used: 0

Month 3: $19,425

STD benefit: $6,800
Vacation Used: 16
Vacation Value: $4,144
Income shortage: $8,481 ($19,425 - $6,800 -$4,144)
Sick leave used: 33

Month 4: $19,425

STD benefit: $6,800
Sick leave used: 49
Sick leave value: $12,625

Month 5 & 6: $38,850

STD benefit: 0
Sick leave used: 150


Total sick leave needed to last 6 months: 232 hours.

Obviously this is a senior Captain at top of scale with 140 hours of vacation pay, excess STD insurance who desires 75 hours of pay. Those with less accrued vacation or those who wish to be payed up to 85 hours of monthly pay will need more sick leave to make up difference.

YMMV