Formation flying and Aerodynamic efficiency

[Nickos86]

Hey there!

Is there any kind of aerodynamic modeling that connected to air flow behind the plane? Is there an algorithm that handles plane’s drag factor in regard of his relative location to another plane- for instance- every flying plane creates behind him a half sphere sector devided to 4 sub-sectors (45 degrees each).The drag factor of every object that enteres that sphere will be subtract according to the appropriate sphere section…

This makes the formation flying not only tactically beneficial but also aerodynamiclly efficient and helps saving precious fuel…
So, is there something like that already/WIP?

Thanks!

[molnibalage]

Is there any kind of aerodynamic modeling that connected to air flow behind the plane?

No, as I know. There is no medium (air) in Falcon modeling. Velocity and AoA and other factors are used to calculate the areo focres with FM data, but there is no interaction between AC and air. Forces are simply “summoned” on AC airframe, there is not real airflow calcuation. I do not know how many simulations are available which are calculating RL the airflow and aerodynamic forces, but I know only one, the X-Plane.

[sthalik]

Even if airflow isn’t modelled over the airframe, dynamic pressure as a function of base temperature and altitude sure is something.

[Blu3wolf]

no, you cannot do it in BMS. yes, IRL you save fuel in very close trail formations. doing that in BMS will have you burn as much fuel as you would with no plane ahead.

also the exhaust for a jet is deoxygenated… which would hurt engine performance at the least.

[Dee-Jay]

In BMS ATM, only engine’s jet wash for heavies.

This makes the formation flying not only tactically beneficial but also aerodynamiclly efficient and helps saving precious fuel…

No benefits at all if you are considering the risks and pilot’s tiredness.

[molnibalage]

No benefits at all if you are considering the risks and pilot’s tiredness.

For fighter AC maybe, but I read some months ago that USAF will consider - if it is possible - to ensure flying in such formation with C-17s and C-5s to save fuel.

[Amraam]

@Dee-Jay:

In BMS ATM, only engine’s jet wash for heavies.

Nope mate, for all

[Nickos86]

"No benefits at all if you are considering the risks and pilot’s tiredness. "

What should be the min/max distance between the fighters for fuel saving? Have you ever made experiments to check this out? Is there any research that have been conducted by (or for) your Air force to verify that?

some articals:
“http://www.guardian.co.uk/environment/blog/2009/aug/13/commercial-aircraft-formation”
“http://www.aviationchatter.com/2009/12/formation-flying-with-airliners-to-cut-fuel-costs/”
“http://www.gizmag.com/vortex-surfing-usaf/24582/”

Thanks

[Blu3wolf]

mythbusters did it with prop planes. I dont know of any other research or experiments…

[Dee-Jay]

@Amraam:

Nope mate, for all

Well! good! … I’ve never noticed the jet wash when changing wing! … (maybe because I’m doing it right ) as during fighting wing. I remember one day, IRL, I’ve passed through the jet wash of my leader following him under a high AOA maneuver, my a/c initiated a roll departure… just had the time to counter act it … but byby leader! (wasn’t able to close him up after that energy lost)

[Dee-Jay]

@Nickos86:

"No benefits at all if you are considering the risks and pilot’s tiredness. "

What should be the min/max distance between the fighters for fuel saving? Have you ever made experiments to check this out? Is there any research that have been conducted by (or for) your Air force to verify that?

some articals:
“http://www.guardian.co.uk/environment/blog/2009/aug/13/commercial-aircraft-formation”
“http://www.aviationchatter.com/2009/12/formation-flying-with-airliners-to-cut-fuel-costs/”
“http://www.gizmag.com/vortex-surfing-usaf/24582/”

Thanks

Only thing I know, is that we are a little bit “tired” after that : http://www.youtube.com/watch?v=NKXeuyfpCvk

… personally, I do not imagine staying in that position 5 hours long or more.

EDIT: after having a look to your links … C-17 are not so close. But even at that distance, keeping that position for long cruise need a 100% attention during all the flight (may requirer reinforced or doubled crews depending on flight duration) and/or a good (reliable) AP.

Concerning the sim, personally I do not think it would change things a lot on a 2 or 3 hours F-16 mission (?) … I would simply prefer an AAR before entering hostile area.

[Dee-Jay]

What should be the min/max distance between the fighters for fuel saving?

IMO, very close. (?) because turbulent airflow increase the drag… so if not at the right position, you will certainly burn more fuel.

[Guest]

If there is no “air” modeled, why is there “turbulence” when caught in the tanker’s wake?

[Frederf]

Dee-Jay, the proposed “flock of C-17” formation would use special automated equipment to maintain formation distances for long periods of time. It wouldn’t be hand flown.

[molnibalage]

@Dee-Jay:

IMO, very close. (?) because turbulent airflow increase the drag… so if not at the right position, you will certainly burn more fuel.

The wingtip vortex trails exist 60-120 sec depending on AC size on the ground this is why required spacing between landing AC. In the air even at high altitude if the vortex trails are existing 30-40 sec with traveling speed means km of spacing.

[molnibalage]

@-Ice:

If there is no “air” modeled, why is there “turbulence” when caught in the tanker’s wake?

My guess it is made be “hand”, it does not come from calculated airflow. Fly close to any fighter you will be fly as smooth as silk…

[Dee-Jay]

@molnibalage:

The wingtip vortex trails exist 60-120 sec depending on AC size on the ground this is why required spacing between landing AC. In the air even at high altitude if the vortex trails are existing 30-40 sec with traveling speed means km of spacing.

But this vortex is moving away from a/c. How can you predict the trajectory of the vortex.

[molnibalage]

@Dee-Jay:

But this vortex is moving away from a/c. How can you predict the trajectory of the vortex.

As the birds knows where are the vortexes. You can measure where they are or with today CFD modeling it is not a big issue to predict their locations.

[Mav-jp]

@molnibalage:

No, as I know. There is no medium (air) in Falcon modeling. Velocity and AoA and other factors are used to calculate the areo focres with FM data, but there is no interaction between AC and air. Forces are simply “summoned” on AC airframe, there is not real airflow calcuation. I do not know how many simulations are available which are calculating RL the airflow and aerodynamic forces, but I know only one, the X-Plane.

this is wrong and true

Wrong because there IS air modeling

temperature
pressure
humidity
volumetric mass
mean speed
rotation speeds
heat/mech turbulences
jetwash

are modeled , are evoluitive parameters and have real actions on aerodynamics

True that there is no real Navier Stokes 3D calculation around airframe, simply because it is impossible with 2013 computation power and that would be useless because our modeling for F16 is VERY accurate (based on wind tunnel testing from NASA ).

i would add some specific stuff when AC is behind another, like i did for Jetwash…but jeeeeez …

[molnibalage]

Wrong because there IS air modeling

I know*, but there is no medium between aircraft. The parameters of the air what you listed are counted for aerodynamics calculation but airframe does not generate vortexes, etc. and do not fly “in the medium”. There in no real air, that is why i wished to say only its parameters. The parameters of air is counted (I guess) for thrust (modify the thrust which is defined by FM) and density of the air I guess also different.

*When I tried to reproduce the climbing record of Streak Eagle - with well set EW - in Falcon the F-15 at high the acceleration always were slower as in RL as long a I did not set temperature which is typical in a cold winder morning. The climbing records of Streak Eagle can be reproduced with 2-3% accuracy. This means a very good FM/thrust model, because the acceleration of F-15 is well modelled from 0 to 40k feet.