Flaps While Cruising lol


That 40kts headwind does affect flight time, but even with a 5kt winds I still get terrible flight time.

320 knots is waaayyyy too fast. Slow down.

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If you flew at just over the stalling speed of an aircraft then you would have so many many hours of flight time but you wouldn’t really get anywhere. If you flew at just below VNE your flight time would reduce but you are still going the distance

That’ll bring me below m0.77 with will make the plane fly way to slow. (747 with 73% load)

No. Flaps increase drag and generate lift.

320 kts below FL 280 corresponds to M.85 above. This is okay, but the upper limit of where you should fly.

@Jeffrey_Varga Early in a flight, the estimated fuel time will be lower than the actual time you have. This is because the airplane is heavier, so the engines work hard early on. You’ll be able to make it to 20 hrs on a 787 no problem. Airplanes naturally pitch up (particularly the 747). If they didn’t do this, no air would go under the wing to push it up (also Bernoulli). Adding flaps doesn’t really ‘solve’ anything, because there isn’t any problem to begin with. Cruise above FL300, at M .80 or so, and you’ll have no trouble. Happy flying!


I understand you are heavy early on, thats why I am at FL260… On a 787 I cannot make 20 hours. I step climbed, no other weight except fuel, and had tailwind and still did not make it cruised at .84

I gotta be doing something wrong.

What is your vertical speed when you climb? Anything more then 3000 feet per minute to start, slowing to about 1500 fpm near cruise is too much.

Start out at around 2500fpm, then above FL150 i do around 1000-1300.

Keep in mind that the estimated flight time until your fuel runs out will be several hours shorter during takeoff and the first parts of cruise than the actual time.

It could be good to try a flight on casual, so if you run out of fuel you won’t get violations, and you can test the flight time you’re getting.

Here’s a guide to step climbing if it helps:

I was very surprised to see this as a topic… lol

Additionally, this topic from DeerCrusher might be helpful.

It even uses the 787-9, which you mentioned.

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I also get that too, but as you suggested I have tested it through a whole flight. Anyways thanks for your help. Just interesting to see how flaps work at 30k feet.

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For sure! In the end, flaps are used to generate lift. They also induce drag (making them ineffective during cruise). Good luck getting things sorted!

Don’t forget in real life, at those speeds the flaps would literally break and fly off the plane if they were deployed, not to mention how the drag and change in the smooth aerofoil shape of the wing would upset the flight characteristics.

mate, this was a fun topic and remember if aint got those dank physics xD

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U Shoudn’t Be Using flaps when cruising but I tried it you were correct about what you said :)

250-320-0.8 is general climb profile of many aircraft like B737 a320 etc. it is not fast enough.

he must be facing with variable winds which is affecting his flight time. you can always check that with GS changing during flight. and as you go higher at a fixed mach no. your GS will decrease. because as you go higher OAT gets lower. decreasing the mach speed. flaps only affect your lift nothing else. with flaps on cruise you will see your aircraft will pitch down a bit for level flight. but it is not practiced. flaps induce lots of drag decreasing your fuel efficiency by upto 25%. further there is always a maximum flap extension speed in aircraft manual. at high speed like during cruise. flaps will put so much stress on wings that it may just seperate from the airframe.

Flaps INCREASE drag as they change the mean camber line of the airfoil thus altering the chord line and the effective angle of attack of the wing for a given physical pitch.

Most modern airliners will push slats first at the first flap selection point. After that the trailing edge flaps will start to extend into the airflow. Anything that extends into the clean airflow thus disturbing it will CREATE parasite drag (you will feel the aircraft pitch forward and a rumbling start as the airflow is disturbed).

The primary purpose of flaps is to allow a high speed, high altitude optimised wing design to be modified for lower speed take-offs and landings. Trying to land a 777 flapless requires a massive amount of runway!!! (I think you could just about stop on a 4000m runway with max manual braking)

Flaps also have limiting speeds as the aerodynamic loads on them can be pretty immense (have a look at the size of them and their actuators next time you fly!) At best if you extend them above the limiting speed you will get flap/slat load relief (a tech term for the aircraft telling you you’re being an idiot) and they won’t extend. At worst you’ll rip them off the wing.

I can only assume that the computer program is not expecting you to have the flaps out at FL200+ so is miscalculating you endurance. In ‘reality’ you are creating drag and therefore reducing your endurance considerably.


I didnt really ask what flaps were, already knew that. made this thread for fun because its fun to cruise at FL320 with full flaps.