Sweeping jet technologies are being evaluated to increase the sideforce (lift coefficient) of vertical fins on airliners to enable reduction in size and drag of these components. This would allow the vertical tail to be reduced in size sufficiently to reduce the fuel burn of the aircraft by 1 to 2%. The technology would likely be employed on the shorter version of a family of aircraft that have a small tail volume. It may not be needed on larger, longer variants of the same aircraft type.
The technical challenge is to incorporate existing civil aircraft safety margins into systems that have their origins in the neutral or unstable characteristics of fighter aircraft.
A full-scale 757 tail, equipped with active flow control, has demonstrated increased rudder effectiveness
in 2013 wind-tunnel tests by Boeing and NASA that could lead to smaller, lower-drag vertical tails. (see notes)
- Failure of the air supply system during critical flight regimes
- Degradation of the flow characteristics of the small channels along the hinge line due to weather and other contaminants
- Resulting loss of lateral control