What is the aircraft family with the highest maximum glide ratio whose manufacturer is Grob Aircraft ?
select ?ent where { ?ent wdt:P31 wd:Q15056993 . ?ent wdt:P1470 ?obj . ?ent wdt:P176 wd:Q561036 } ORDER BY DESC(?obj)LIMIT 5 
aircraft family: Q15056993 grob aircraft: Q561036