Just sat here wondering what factor is it that determines flap deployment for take off? I have been 'flying' flight simulators since Flight Unlimited 1, but outside using tutorials I just set the flaps from none to flaps 15; depending upon 'how the maggot bites' :) Now I can't really see the Captain of a B747 greeting his flight crew saying " morning chaps, what flap setting shall we use today? then getting a reply from his P2, "well, Bob, we haven't used flaps 20 lately, how about that?" ..... Not likely is it!Looking at the Data in my Manuals concerning Take off conditions all I notice is that the more flap deployment used the slower the TO roll needs to be? More comfortable for the Pax maybe, but not very plausible, is it :)What is the correct answer?KenSomerset, England

Common is one to 15 degrees.... Really no fixed answer but in real life it depends on gross weight, Altitude of the airport, Outside temp, Air density,,,,so on so on ...... I seen 20 degrees or better in real saturated air.....Diz

Ken,There is a terrific little takeoff data calculation booklet for the ATR here:http://atr.flight1.net/forums/forum_posts.asp?TID=1942&PN=1IIRC, there's a pretty good explanation there for why one might choose one flap setting over another. My guess is that company policy has a great deal to do with it. Back when I was flying 757s for AWVA (now MidCon), company policy was that flaps were either 5 degrees or 15 degrees, with 15 being used for shorter fields and heavier weights, though I don't recall ever needing to use more than Flaps 5.In reality, you'd look at the distance required to clear any obstacles at the departure end of the field and make your decision based on that. Unfortunately, the tables that show this in real aircraft POHs are seldom recreated for MSFS. Kurt "Yoda" Kalbfleischwww.simulomundusrex.blogspot.com

Take off flap settings are set by the manufacturer, so consult the 'POH' from the manufacturer to determine what flap setting to use for take off.Light aircraft usually use no flaps or one notch of flaps for take off. Large turbine aircraft have a variety of flap settings that can be used. The pilot picks the flap setting that minimizes takeoff roll for the aircraft's weight and outside air temperature. The POH for large, turbine aircraft will have a chart that shows takeoff speeds as a function of flap setting, aircraft weight and outside air temperature. To use the chart, first determine the aircraft gross weight, then determine the outside air temperature, then select the flap setting that gives the lowest takeoff speed.

> Now I can't really>see the Captain of a B747 greeting his flight crew saying ">morning chaps, what flap setting shall we use today? then>getting a reply from his P2, "well, Bob, we haven't used flaps>20 lately, how about that?" ..... >What is the correct answer?>>Ken>>Somerset, Englandhahaha.. I had a good laugh about this. I am sure thats the way they pick the flaps! ROFLMAO!Flaps lower the stall speed, and add lift. Thats when they come in use. The situation determine the usage. Weight of the plane, runway lenght, SOP's.. you name it.You can however imagin on a short runway, with flap 20, the Vr is lower, so one can make it easier without running out of runway(hence the name).Johan[A HREF=http://jdserver.no-ip.com]Personal Server[/A]A LITTLE LESS CONVERSATION, AND A LITTLE MORE ACTION PLEASE!

Thank you gentlemen for your helpful response, it does seem that quite a lot of factors are involved when deciding the TO Flaps deployment. I guess it helps if you have a 'kindly' Airline SOP to work from :0. In future I will look at the MTOW, Fuel ecconomy, Pax comfort, weather, Rwy condition, length and altitude; then err on the side of a positive roll and liftoff.Johan, earlier this week I did a TO with flaps 20, the aircraft lifted off gently on it's own (no joystick input) with about 5.5% up trim. Maybe the way to go?KenSomerset, England

Any aircraft will t/o with flaps or without them given a fair ammount of trim up.However, the goal is to do it at the right speed, to be able to abort while on the runway if needed, and without running out of runway to brake.From the net:The Flap About Flaps(using a Cessna 172 as an example)Flaps # Increase lift # Increase drag # Reduce stalling speed (about 5 knots or 10% in a C-172)General Characteristics # First increment of flaps increase lift more than drag # Last increments increase drag more than lift # Partial flaps increase lift without as much drag penaltyIncrease Flaps When you want to # Get down # Slow downDecrease Flaps When you want to # Go up # Speed upAdvantages of Flaps # Greater rate and angle of descent without an increase in stall speed # Better visibility over the nose # Reduce floating in the flare # Make for a less extreme nose-up touchdownMore Advantages of Flaps # Slower touchdown # Use less runway # Less wear and tear on brakesDisadvantages of Flaps # Use on landing makes for slower speeds and tends to direct the airflow away from the tail, resulting in less elevator and rudder effectiveness and slightly more difficulty in crosswinds (you will lose rudder effectiveness first)Disadvantages of Flaps # Make the tires skid more easily, reducing control and braking effectiveness on the groundMore Disadvantages of Flaps # Slightly reduced stability on the ground by increasing the area for crosswind to work on # Require more trim changes # Reduce the gust-load tolerance # Make a go around more difficult

Hi Johan,That's a splendid tutorial on the use and misuse of flaps, with a touch of airmanship for good measure. I'm going to print it and pin it to my cockpit noticeboard.When I started this thread I thought I was asking the 'sucker' question; but as I have always had doubts about take off flap settings I asked it anyway :) - the replies have been thoughtful and educational.My thanks to everyone,KenSomerset, England