787 Uses Flaps in Cruise

You read that right - but let me explain:

While in-game, after hours of experimenting, I found that the fuel burn is lower (range longer) at almost all weights, altitudes, and speeds with 1-5 degrees of flaps. This is in fact realistic, and accurate because:

In real life, 787 has electronically actuated variable trailing edge camber which is “completely transparent to the flight crew”. This was not re-created in IF’s 787 - so it is not completely transparent to the pilot - but must be manually controlled by the pilot to mirror something similar to what would be happening in real life.

After diving into the World Wide Web, and digging through presentations, articles, and academic papers: here are the best 3 sources I have found to explain the use of flaps in cruise on the 787

  1. Boeing’s chief aerodynamicist in 2011 created this presentation. Please reference page 17
    The Next Decade in Commerical Aviation Aerodynamics

  2. Green Aviation: Green Aviation
    Google Book so I’ve taken screenshots for those who wouldn’t have access

  3. Boeing unveils plans for trailing edge variable camber on 787 to reduce drag, save weight

In summary - while a pilot selecting certain degrees of flaps while in cruise is unrealistic - the actual effect is similar to what would be occurring in real life with some minor extension of the trailing edge flaps by the flight system. The biggest difference being that the slats on the leading edge would not change position.


Wow! Great post, I’ll have to try this on my next long haul!

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Woah, and that’s why it’s nearly impossible to fly lax to lhr without flap 5

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Been there done that :)

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I’m going to do this for long hauls! :)

The a350 does this too if I recall correctly

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You are correct

I am going to advise against you guys putting the flaps down in IF to try and simulate this. The system uses very small corrections often aided by the outboard spoilers to reduce flexing as needed. When you select flaps, you get slats as well and a larger deflection of flaps which will greatly add to drag, not to mention you’d rip the flaps off the wings.


A350 does this variable camber and leading edge droop as well. I believe it’s all computer controlled on both vs the pilots selecting the flaps to a particular setting. It’s quite amazing! Almost like the 787 and 350 have a “living wing”

Edit: wanted to agree wholeheartedly with what @Ryan_Vince says above-this is very likely a bad idea to try in IF as the sensors and systems that calculate fuel burn/local wind and aerodynamics in the real world aircraft aren’t modeled in IF

Because they are not modeled in IF - I’ve found that the performance is significantly better when they are manually activated. AOA is lower and more realistic, and drag is reduced (proven by lower fuel burn and less power needed), which results in longer range capabilities.

If in-game performance was worse with flaps at 5 degrees I would definitely agree that it shouldn’t be done - but it is actually (proven to be) materially better and (in my opinion) closer to a real life configuration - so I’m not sure why it shouldn’t be accepted (if not suggested).

Ok, no, unless you can show me photographic evidence I can assure you no airline will use flaps during their regular operations

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Please reference the textual evidence from multiple sources in the original post. It’s also been established by several others here that they are in fact used in flight at cruise on the 787 and a350.

Explains the crazy nose up pitch during cruise

Didn’t know this! I guess you learn new things every day!

Interesting. I think I know of one plane that actually can use flaps in cruise and that’s a Maule which have a negative flaps seting

I was wondering about this last week and thought it was some sort on anomaly! Thanks!!!

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How many degrees of flaps do we need to use? 5 degrees?

So if I am doing lets say a 6 hour flight, I would use 1 degree and a 12 hour flight I would use 5 degrees? Like what angle would be best for minimizing fuel burn? Also very interetesting topic thanks for sharing!

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Just as a disclaimer, I wouldn’t say this is something you “need” to do. It’s not a perfect simulation of the wing configuration IRL.

However, I have found that using 5 degrees of flaps at almost all FLs (+18,000ft) produces a lower fuel burn, assuming any normal load up to MTOW.

1 degree of flaps does create a minimal reduction.

I will often retract my t/o flaps and set them to 1 degree until passing through ~FL240 at which time I’ll set flaps 5 degrees for the remainder of my cruise (and any step climbs).

One final disclaimer: This is by no means a standard operating procedure that needs/should be used in IF. It is only based loosely off of the real world. I personally have found that I prefer to use flaps while climbing/cruising because I like the lower nose angle, and of course, the more efficient fuel burn.


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