Most of us like to use drogue chute. Some of us afraid of using it. As for me, the drogue chute is a good friend if you know how to use it properly. This time I will talk about the proper lenght of the bridle.
My drogue chute is my good friend. Not only because it gives me a chance to land on a very small field, but also because it is easier to make a spot landing. A drogue chute counters ground effect and the flight trajectory becomes impressively flexible.
I didn’t have any troubles with my drogue chute until I changed my harness, and the point where the chute connected to the harness had been shifted back by 30 cm. I never really thought much about how long the strap of the chute had to be. And, reading the notes about drogue chutes, I also didn’t see where anyone else had paid any attention to it.
Only the “tailed” glider pilots were concerned about drogue chutes straps getting tangled in the tail, so they usually make the straps shorter. The other pilots’ drogue chute straps length varied quite a lot, often depending on the manufacturers of the harness and the chute.
So, one day before the competition, I was approaching for a landing on a field, at the end of which there is a downhill slope. I have to land before the slope. I let the chute go, being on the trim speed at that moment (later I decided that was wrong).
And then something happened that has never happened before: instead of filling up with the air and opening, my drogue chute just fell back and got stuck on the keel tube. Probably because the rope is longer than usual now, and because the angle of attack of my glider at trim speed is so big, therefore the keel tube is not parallel to the ground, but dropped down.I’m trying to shake the chute free but I can’t push the bar much, as I am already at pretty much the minimum speed. Neither can I pull the bar, as the rope is holding me back. I’m trying to get up in the harness but can’t do it either, as the chute strap is pulling me back. Without the drogue chute and without an opportunity to pull the basebar, I am already flying over the downhill part of the field with no speed. Well, then – tydydysch (means, crash:). Broken upright – not a problem, and broken carbon fiber leading edge. As it turnes out, it is not so hard to break a carbon leading edge. And, well, there is a hole in the chute, in the place where the chute got stucked on the keel.
As it turned out, it is quite hard to find a carbon leading edge of a small glider fast enough, as there are just a few little carbon gliders in whole the world. I had to skip the event.
The incident made me think.
Landing with the drogue chute can be divided into three phases:
- throwing the chute out,
- flight with the chute,
- pushing the basebar.
After you push the basebar and stall the glider, it is very common to find a chute wraps around your keeltube. When we push the bar out for landing, we put the keel tube nearly perpendicular to the air flow, depending on where the drague chute flies at that moment. And we move back our body (and hence the point where the chute connects to the harness). It is normal then that the chute gets wrapped around the keel.
Another situation is when the chute gets wrapped on the keel during the flight.
This will not happen if the parachute rope is long enough or short enough. But if the parachute bridle has some marginal length, which at low speeds makes the chute longer than the keel, and at high speed – shorter than the keel, it may be a situation as Gerolf got in once. He tried to pull the bar and the chute strap just didn’t let him do it. Then instead of pulling, Gerolf had pushed basebar a bit, slowed down, and let the chute slide down from the keel. One would need to not be already too slow at that moment, and need to have some altitude and some brain, too!
After this incident, Gerolf shortened the strap of the chute, and this never happened again. But to get my chute wrapped around the keel tube right after throwing it out, I must have been really lucky:) Looks like the rope was longer than usual, and the angle of attack of the glider was big (therefore, the keel tube was quite low).
When the angle of attack is too big, the keel tube is quite low, as it drops down
At higher speeds the keel tube would be almost parallel to the ground, and it would be very difficult to catch it with the chute (in the pictures you can see my old harness with the short enough strap and the glider at the normal speed).
So I decided for myself:
- Do not throw the drogue chute out at low speed.
- Shorten the main bridle of the chute.
Perhaps you can also extend it. But somehow it seems safer to make it shorter.
I am sharing all this so some experienced pilots would maybe comment and share their vision, too. Or, at least, also would check their drogue chutes.
I personally think that the chute is a very useful thing, and one must love it and enjoy using it. So, I do not want to scare anyone with this post; just the opposite: we have to learn how to be friends with our chutes.