I see that at high altitude airfields you can use fap 50 to land.Are there any rules of thumb as to how high an airport is before using flap 50?Is it also down to runway length and weather conditions, rather than just the elevation of the airfield?

I see that at high altitude airfields you can use fap 50 to land.Are there any rules of thumb as to how high an airport is before using flap 50?Is it also down to runway length and weather conditions, rather than just the elevation of the airfield?

You can use flap 50 whenever you want, nothing to do with field elevation except a high altitude airport requires a higher vapp therefore depending on weight your more likely to be using flap 50 to reduce vapp as much as possible.Your main criteria for a Flap 50 landing1,Short runway2,At or near max landing weightSome also argue that the higher the flap setting on approach the better due to drag causing the engines to be spooled higher in the event of a go around, however on the MD11 I think Flap 50 is a bit much in that case.Regards

To add to what Rob has stated, Going by the example below, the take off from Narita will be a dial a flap 14. Landing in Auckland will be a flaps 50EXT. Arriving in Auckland nearly fully laden minus enroute fuel burn.LANDING NZAA/AKL RWY 05R LDA 3292M GH-PBY MCDONNELL DOUGLAS MD-11 CF6-80C2D1FAUCKLAND TEMP +19C QNH 1019 WIND 100/04 (02KT HW)-------------- INFLIGHT CONDITIONS -------------- ** 50/EXT ** DRY ** LDG AUTOLAND ** ** AIR COND ON ** ANTI ICE OFF ** ASSUMED LANDING WEIGHT 199250 KG VREF=150KT VAPP=155KT ---------------- MAXIMUM BRAKING ---------------- MANUAL 286631 KG 1367M (REM 1926M)-------------- AUTOBRAKE LDG DIST --------------- AUTO MAX 286631 KG 1569M (REM 1724M)//AUTO MED 286631 KG 1882M (REM 1410M) AUTO MIN 286631 KG 2195M (REM 1097M)***************************************************MAXIMUM STRUCTURAL LANDING WEIGHT IS 213869 KGNow the take off phase:TAKE-OFF RJAA/NRT RWY 34L TORA 4000M GH-PBY MCDONNELL DOUGLAS MD-11 CF6-80C2D1FNARITA INTL. TEMP +11C QNH 1023 WIND 040/09 (03KT HW)------------------ CONDITIONS ------------------- ** FLAPS 14 ** NORM T/O ** DRY ** ** AIR COND PACKS ON ** ANTI ICE OFF ** ASSUMED TAKE-OFF WEIGHT 278900 KG ------------------ FULL THRUST ------------------- +11C 290000 FIELD 170-175 180 187 851M 107.8%---------------- REDUCED THRUST ----------------- +40C 290000 FIELD 173-178 182 189 214M 104.5% +41C 284649 FIELD 173-176 182 189 174M 104.2% +42C 282953 FIELD 174-176 183 189 134M 103.8% +43C 281087 FIELD 174-175 184 189 75M 103.5%//+44C 279291 FIELD 175 184 189 15M 103.1% +45C NOT AUTH +46C NOT AUTH***************************************************DO NOT EXCEED MAX STRUCT TAKE-OFF WGHT OF 285990 KG***************************************************------------------ ENGINE OUT -------------------FOLLOW SID TO 2000'.***************************************************CheersJulian Evans

Some people might use F50 during CAT II and III approaches as this provides a lower pitch angle so its easier to spot the approach lights and runway.