Differential flap settings and spoiler changes hold key for tackling hazard
Researchers are planning flight tests of an Airbus A340-300 testbed in mid-2006 to evaluate the effect of differential flap settings on wake vortex. The tests will attempt to generate a more benign vortex using differential flap settings and spoiler changes as part of the €79 million ($92 million), four-year European Union Fifth Framework research programme Aircraft Wing with Advanced Technology Operation (Awiator).
The A340 wing trailing-edge flap consists of two segments that can be extended down to 26˚ for approach. Originally the idea was to either increase the inboard loading or increase the outboard loading. Simulations and ground-based tests established that greater flap inboard and reduced outboard flap settings led to inboard loading that produced more benign large vortices. Small “vortex devices”, designed to accelerate the destabilisation of the boundary layer vortex, were mounted outboard of the flap section as well.
“We are trying to reduce the wake hazard on approach and landing by modifying the spanwise load distribution and by differential flap settings, so reducing the time to the onset of rapid decay of the vortex or making a more benign vortex with a broader core,” said Awiator programme wake vortex specialist Geza Schrauf, speaking at the American Institute of Aeronautics and Astronautics aerospace sciences meeting in Reno.
Earlier efforts to partially replicate the flap setting effect by rigging differential overwing spoilers (3˚ outboard/9˚ inboard) were not great enough to show any desirable effect.
Awiator began in 2002 with vortex hazard reduction a key goal as part of an overall aim to cut spacing on the approach by 30% or around 1.85km (1nm). Originally planned for flight testing in 2003, certification issues with flap mechanism couplings for differential settings delayed the tests.
GUY NORRIS / RENO
| Mini flaps offer solution The wake vortex reduction experiments with the Airbus A340-300 testbed are demonstrating several advanced features. Mini trailing-edge devices (mini-teds), which are small adaptive mini-flaps attached to the trailing edge of the flaps, is one.The mini-teds are designed to increase high-lift efficiency and low-speed performance, thereby allowing steeper approaches and reducing noise closer to airports. The devices, 10 per wing divided between the inner and outer flap sections, occupy only 2% of the chord. Earlier tests involved devices in a fixed configuration, but the next tests will look at moving devices.Another technology studied as part of the first flight-test phase from 2005-6 was sub-boundary layer vortex generators. These are small semi-streamwise surfaces attached to the flaps to add energy to the sub-boundary layer through vortex generation. |
Source: Flight International
