Not just a simple manoeuvre!

Information and Advice from Bruce Goldsmith (Icaristics article, as printed in Cross Country magazine)

Article from Cross Country magazine

Generally, (and in Britain particularly because of strong winds and ridge soarable conditions), Big Ears is one of the first manoeuvres performed after school training, even sometimes during school training. For most, Big Ears is a safe and easy way to descend without reducing your forward speed.

0ut here in the Alps I frequently see inexperienced intermediate pilots using Big Ears to approach the landing areas in order either genuinely to achieve a quicker descent rate, or often I think just to practice the manoeuvre while over the landing field.

From my experience as a test pilot and having encountered recently a number of people who have had accidents due to this problem, I feel it is worthwhile pointing out that Big Ears is in fact a much more 'serious' manoeuvre than people in general tend to think.

Problems with Big Ears:
Sometimes gliders can have a 'hidden' deep stall problem, which in normal flight is not apparent, but can appear when the glider is put into situations outside the normal flight envelope. This problem can be caused by any one of the following factors:

1. Design - The flight characteristics of the glider could be on the very limit of certification regulations for deep stall recovery when brand new and flown with a pilot exactly in the middle of the weight range, but after just a few hours of use or with a pilot at the low end of the weight range the glider could show some deep stall problems. Doing big ears could just accentuate this problem.

2. Line distortion - Due to usage, lines can either shrink or stretch, again causing no problems in normal flight, but developing a 'hidden' deep stall characteristic whilst practicing manoeuvres outside the normal flight envelope.

3. Cloth depreciation The charactersitics of your glider may change due to usage, possibly causing problems when the glider is flown outside the normal flight envelope.

4. Trim Tabs Sometimes when on the 'slow' setting, and with the addition of one or more of the above examples, trim tabs can alter flight characteristics. Additionally, if some cowboy has added trimmers to a glider that is not certified with trimmers, the same effect can happen.

So it can happen that even your own trusted wing with which you have performed Big Ears many times without a problem, could develop a 'hidden' deep stall characteristic. On exiting Big Ears and especially if you 'pump out', the glider does not regain normal flight and instead slows down even more and then goes into parachutal mode. In this 'deep stall' you descend vertically at approximately 5 m/s (refer to previous Icaristics on deep stall).

The main problem with entering this parachutal mode on exiting Big Ears is not the actual deep stall itself, (a quick 'pump' on both brakes or stepping on the speedbar will 'rock' the glider out of it), but your not realising that fact. Your quick descent rate while in Big Ears will 'disguise' the consequent deep stall. More importantly Big Ears is usually used over landing fields or for top landing in strong wind soaring conditions, meaning that the pilot is vulnerably close to the ground, leaving very little time to react. Hitting the ground at approximately 5 m/s can cause some major injuries to the pilot, especially if the terrain is rocky or steep.

A friend of mine has recently broken his back doing this very manoeuvre. He was flying his wing that he had had for three years without any previous deep stall problems from Big Ears. He was trying to top land on his local flying site in quite strong wind, but soarable conditions and decided to pull in Big Ears to descend more easily for landing. As he exited Big Ears, his glider went into deep stall, and although he was aware of the problem, he was descending rapidly towards some chair lift cables. Not having time to 'pump out' the deep stall, he applied one brake to avoid the cables and hit the ground just next to them, going down wind and in deep stall. He broke his back on impact.

It is important to realise that on most occasions, Big Ears is a very safe method of increased descent but you should always be aware of this potential problem when using Big Ears close to the ground, not just assuming that the manoeuvre is a totally trouble free method. You should be acutely aware at all times of your rate of descent while exiting Big Ears, and be prepared to correct any sign of deep stall immediately and at a safe height above the ground.

My personal advice is to avoid using Big Ears altogether if you are less than 100 m above the ground. Above this height you will almost certainly have time to correct any deep stall development that might occur before being in immediate danger of hitting the ground.

From Cross Country magazine No. 47, October/November 1996.

Flying with Big Ears

More on Big Ears: Another Solution to the Problem

In the above article, Bruce certainly highlights the problems causing parachutal stall from exiting the Big Ears manoeuvre. Note the emphasis on the "exiting" the exercise.

In America it seems they have similar problems: in a recent talk (December 1997) with a lady pilot from that country, she informed us that pilots there are told NEVER to do Big Ears, due to accidents occurring from this manoeuvre. In South Africa we have had a number of accidents occurring from the same thing: broken arm, twisted ankles, injured backs, etc.

Parachutal stall usually occurs when releasing the Big Ears manoeuvre close to the ground. In addition to all the possible causes described by Bruce above (with which I wholeheartedly agree), there is also the added circumstances of wind gradient and even wind shadow. Often these accidents occur on areas where there are trees and/or buildings causing wind shadow or more than usual wind gradient. On top landings they are often slightly behind the take-off, perhaps in the area where wind shadow and/or even a degree of rotor may occur.

Let us jump back a step: when one comes in for landing without Big Ears, a certain amount of surge and dive is expected and countered due to the wind gradient effect on the landing, especially in restricted landing areas. Who has not heard of pilots stalling and falling out of the sky close to landing due to wind shadow? The feeling of the ground rushing up to him makes a pilot pull too much brake too early. The ground rushing feeling is caused by increased ground speed as well as the glider diving to maintain its air speed. Once the pilot realises what is happening, it is easy to allow the glider to maintain airspeed and land properly, with flaring at the right moment.

Now we can go back to approaching landing with Big Ears: when one pumps out the Big Ears, a certain amount of surge is required to ensure that the glider maintains flight smoothly, i.e. air flow over the wing is never interfered with. However, with wind gradient and wind shadow magnifying the feeling of diving and ground rush, it is easy for a pilot to pull even more brakes, adding to the high angle of attack, and not allowing the glider to maintain its airspeed. Although in most cases this does not happen too often, as is proven by many good landings after opening the Big Ears, sometimes it happens that the pilot gets it just right to cause parachutal stall. That is when the fan starts churning real nasty!

Pilots often release Big Ears at heights between 10m and 30m above the ground - just a nice height to get into trouble with, should the glider go parachutal. There has been enough serious accidents for this problem to be taken very seriously.

It is so easy to land with Big Ears on, that I am surprised that Bruce has not mentioned it. All that is required is a good flare at the normal height for landing. The wings usually pop open perfectly and stops the pilot softly. Even if they don't (and I have never seen that happen, unless the pilot did not flare properly), it is so close to the ground that only very bad luck can cause injury, such as stepping into a hole in the ground. Should the wind be strong, then one does not need to pull so hard, as there is a danger of being dragged after a hard flare (a completely different problem, and one which all pilots should be prepared for properly). The descent rate with Big Ears is usually slower in stronger winds, especially on top landings.

Bruce advises not to do Big Ears below 100m above the ground. I want to modify this: never RELEASE Big Ears below 100m above the ground.

Just land with them.

Laura Nelson
19 May 1998

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