SELECT *
FROM (
SELECT 'A9t' AS sortField UNION ALL
SELECT 'A10t' UNION ALL
SELECT 'A11t' UNION ALL
SELECT 'AB9F' UNION ALL
SELECT 'AB10t' UNION ALL
SELECT 'AB11t'
)
t
ORDER BY LEFT(sortField,PATINDEX('%[0-9]%',sortField)-1) ,
CAST(substring(sortField,PATINDEX('%[0-9]%',sortField),1 + PATINDEX('%[0-9][A-Z]%',sortField) -PATINDEX('%[0-9]%',sortField) ) AS INT),
substring(sortField,PATINDEX('%[0-9][A-Z]%',sortField) + 1,LEN(sortField))