We now recommend that all rapid descent techniques should ideally only be used when high up, e.g. where the pilot is trying to avoid being sucked into a cloud. With plenty of height and space to play with, the various "downsides" of the Big Ears technique which have now been identified are of little consequence and the technique is effective, perhaps doubling the glider's usual sink rate.
However, British pilots often use big ears to vary height during a landing approach. In this situation, as recent experience has revealed, there are some dangers that pilots should be aware of. Let's look at the technique in more detail:
Getting in to Big Ears. There is a well known danger of leading edge collapse when pulling big ears. This can easily be avoided by using the correct technique of twisting the outer A-lines downwards by rotating the hand rather than pulling down where you inadvertently pull the entire a riser.
As the ears are pulled in there is a sudden increase in drag. Pulling both the ears in at once may rock the glider into a stall. For this reason, on most gliders we recommend that the pilot pull one ear at a time. (However, there are a few gliders where it is better to pull both ears in simultaneously: check your owners manual for advice.)
Whilst in Big Ears. The wing loading of the part of the wing still flying is increased, making it less susceptible to tucks. However, the glider adopts a steeper flight path with no change in attitude, so the wing is operated at a higher angle of attack and there is a possible danger of stalling. Using the speed bar to lower the angle of attack a little when in Big Ears can provide an increased safety margin.
The glider tends to have a reduced forward ground speed as the extra drag results in a steeper flight path. This effect is greater than the increase in air speed due to the increased wing loading. So Big Ears does not assist if you are trying to penetrate forward through a venturi zone (such as a windy hill top).
The pilot has reduced directional control. Weight shift works to a point, as does pulling more on one outer a-line than the other. However, neither is as effective as using the controls normally on a fully inflated glider! The pilot can not 'actively' fly the glider due to reduced feel through the brakes, thus making spotting the onset of a stall (or collapse) impossible. There is also less roll damping. This can lead to osscillations when weight shift turning near the ground.
The use of other maneuvers must be restricted due to dangers of excessive line loading. (The flying loads are taken by fewer lines - anything that might further increase these loads should be avoided.)
It is now clear that the well known danger of stalling whilst descending through a wind gradient may be exacerbated by the use of Big Ears, because the wing is already operating at a high angle of attack. This danger of stalling is further increased when flying from an area with horizontal airflow into an area of rising air, such as would be found just behind the crest of a hill.
Getting out of Big Ears. When the pilot pumps to Big Ears it may be possible to cause the glider to enter a mild stall or go into a deep stall. Whilst a full vigorous pump on both brakes is the quickest way to pop the ears out, we now believe this may increase the possibility of a stall. Letting the ears pop out on their own, with just a "tickle" of brakes if necessary to help the last bit, is preferable.
Conclusion. We now consider that there is a combination of factors which could dramatically increase the chances of a glider stalling when using the Big Ears technique. The worst case scenario appears to be when the pilot suddenly deploys or recovers Big Ears close to the ground, in terrain affected wind conditions. A stall in these conditions would probably leave insufficient height for recovery.
If a pilot does decide to use Big Ears on a top landing approach they should only be released when high enough to recover from an inadvertent deep stall, Below this height the better view is to keep them in and land in Big Ears - but be prepared for a PLF! You will then have the problem of collapsing the canopy - all the time be aware that most techniques will pop the ears out and possible lead to you being back into the air or dragged back. It would be preferable to find a less windy landing place - such as the bottom of the hill!
Extracted from Skywings, December 1998