Big ears and stalling

Hairy Dave's picture

This winter I saw another glider stall in big ears and analysed an accident where that was the likely cause. That makes 3 I've seen and several more I've heard about. All on modern, sensible gliders in good condition. In the last two the pilots were badly hurt.

The problem is that in big ears you have about normal forward speed and plenty more downward speed (a much reduced glide angle). As paragiders maintain normal attitude in big ears, the result is a significant increase of angle of attack. The result of that is it doesn't take much for the glider to stall; a bit of turblence, a shear layer, brake, some rain, line skrinkage or cell stretch could all do the trick.

Current advice is that big ears should be immedialty and smoothly followed by application of full speed bar to get the angle of attack somewhere sensible again.

I suggest that big ears + bar should only ever be used when actually necessary and I can only think of two possible scenarios:

1. If you're in a cloud, or have made a mistake and are about to enter, and are following a compass bearing to escape in the right direction (without a compass you might just go round and round or hit something).

2. Possibly when bottom landing in wind much more than trim speed to avoid landing going backwards, thus gaining speed with extra collapse resistance. But entering a slower and/or turbulent boundry layer near the ground is one of the causes of big-ear stalling. I'd favour just enough speed bar and rear riser control if it's bumpy.

Clearly, both of these scenarios are to be avoided in the first place.

I think any other situation is better handled with speed bar, spiral dive or just patience. B-line is solely for if you're in a cloud and have forgotten the compass.

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Frank_O's picture

Re: Big ears and stalling

Frank Ogden of the slightly gay pink/grey Aspen...

Thank you Dave. Most thought-provoking. I kind of knew that big ears were not always a good idea but have never heard the reason clearly articulated before.

My power wing is too stiff to pull in big ears. If there is the slightest hint of wind gradient on approach, everything gets set to fast, which is fine, except that you often have to bleed off a whole load of speed - and landing field - before touchdown. Perhaps there is a case for effective trim tabs on free-flight wings!

F

big ears and bar

"Current advice is that big ears should be immedialty and smoothly followed by application of full speed bar to get the angle of attack somewhere sensible again."

never heard that one. surely you mean half bar at most?

EDIT

Er, actually, having picked up my calculator and thought about it for a few minutes, that's not quite so dramatic as it sounds. even full bar, especially on lower rated wings, will not return the angle of attack fully to normal.

The only time i've ever been personally alarmed was on a wing that actually slowed down below normal flight speed in big ears. i decided against purchase of this otherwise superb glider (gin bonanza) for this reason alone.