Mitsubishi's Air Lubrication System blows a fine sheet of bubbles below the hull of a ship. The bubbles form a "carpet" on the hull, reducing friction. See Gizmag (yes, sorry) for some more information.

Let's assume that such a similar mechanism - something like the surface of an air-hockey table perhaps - would be feasible to implement on an aircraft.

What aerodynamic effect would it have? Could it, assuming it were feasible, provide any benefit to an aeroplane/helicopter/dirigible?


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NASA tested a similar concept. They call it Active Flow Control, or AFC.

A full-scale 757 tail, equipped with active flow control, has demonstrated increased rudder effectiveness in wind-tunnel tests by Boeing and NASA that could lead to smaller, lower-drag vertical tails.

"Sweeping jet" AFC actuators were mounted on one side of the fixed stabilizer, just upstream of the rudder hinge line to blow on to the leading edge of the deflected surface. The 37 actuators were supplied with variable mass-flow pressurized air from an external source and were individually addressable so that different spacings and zones could be tested.

Tail fins are huge to help compensate for engine failures. But with such system blowing pressurized air out of holes upstream from the rudder, manufacturers can design smaller tails to save on drag and weight.

Another system that works by suction (not blowing) at the leading edge is on the 787-9/10. It is used for both the horizontal and vertical stabilizers on the -9, but Boeing dropped the horizontal stabilizer system on the -10. There were plans to use it on the upcoming 777X, but Boeing dropped it. That system is called hybrid laminar-flow control (HLFC).

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    $\begingroup$ This blown flap technology was already used on the F-104 and is meant to delay separation, and drag reduction is only an indirect result because now the vertical can be made smaller. A better comparison might be supercavitation as used on Russian torpedoes. But this only works because water is 800 times more dense than air. $\endgroup$ – Peter Kämpf Dec 11 '16 at 9:02
  • $\begingroup$ If this proves to work as expected, would it be safe to assume the APU would be fired up to provide the air, since the only time it would really be needed is when the plane is down an engine at take-off, when the remaining engine(s) critically need all their power to keep the plane in the sky, and bleed-air reduces power? $\endgroup$ – FreeMan Dec 12 '16 at 21:20
  • $\begingroup$ The Wired reference seems to make no distinction between the two completely different systems. Is the 777 system like the 757 ecodemonstrator which used AFC, which is blowing from inside the vertical stabilizer, or like the 789 which used suction through small holes? $\endgroup$ – Pilothead Jun 8 '18 at 21:48
  • $\begingroup$ @Pilothead - See update, thanks for the heads-up. $\endgroup$ – ymb1 Jun 8 '18 at 21:56

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