Thank you for your responses. The situation I'm thinking of is flying into short runway having had blue elec hydr pump fail. You elect to continue as ldg dist not increased by much but the on gear extension you lose green system. Gear stuck down. You recover blue system by using RAT but ldg dist now increased a bit more due to 140kts to keep the RAT going. You then have dilemma of short runway with very tight figures or divert to somewhere with long runway 30mins away fuel depending.
Very good point about leaving slats out in icing conditions certainly one to watch. I can certainly see the logic in flying slower with slat out. The ref is FCOM procedures/norm procedures/ supplementary procedures/ l/g flight with ldg gear down.
Looking in the QRH fuel penalty section I think first line it says these are conservative penalty factors. I always understood as mention to essentially your trip X 2.8 but looking at the tables I mentioned is this figure too conservative?
Pineteam, your are quite right. Best to see what your actual burn rate is doing with the gear down at that moment. The fuel flow not prediction should be accurate. So for a diversion 30mins away a very ball park figure would suggest 2tons to get there. You would want at least a ton when you get to your alternate so really at least 3 tons in the tanks before diverting.