terminal velocity descent

I read somewhere that a recover from a terminal velocity descent must be deminstrated for the commercial balloon certification. How do you get to terminal velocity and how is it recovered?

1. Go high....... cool it off

2. Heat it back up before impact.

Better description:

I went to 10200 agl. stopped heating....... started descent. didn't burn.......... descent built up eventually to ~1300 fpm

fired it back up at 2500 feet agl

leveled out at ~ 1500

and thats the truth.

Doesn't the POH for the balloon state the minimum altitude to apply eat?

Interesting- that's a quite survivable impact velocity (my old sport parachute, a converted military emergency 'chute lowered me at about 22 fps, which is very close to 1300 fpm).

What size balloon was that, and is that a typical terminal descent speed for balloons? Was the envelope collapsed? (Of course not....but was it starting to? Would it? Was that *really* terminal velocity? I'm not challanging you, but I'm really curious....)

Craig Wall

It was a Raven AX7.

That is typical. It also depends on how much weight is being carried. If I had been alone, it probably have been around 1000 fpm. The envelope doesn't collapse, more air is going in the mouth than escapes. And, the vertical 'wind' pushes in on the sides, and it starts getting shaped like a mushroom. Yes that's really terminal. Terminal means as fast as it will go under the conditions, mostly determined by weight.

Yup, it's typical and survivable. I've terminaled AX-6 (56,000 cu ft) to AX-8 (105,000 cu ft) balloons of three different manufacturers and gotten similar results. Depending on the load, 1100 to 1300 ft per min. As long as the envelope stays intact, you have a very good chance of surviving, even walking away.

PLEASE NOTE! - I do NOT recommend flying into the ground at these speeds, just point out that in a bad situation, you still have a chance.

BTW, Fossett reported descent rates of at least 2500 fpm shortly before contact with the ocean. (Damaged envelope and thunderstorm)

Different balloon brands and models will develop different terminal descent rates. A sphere on a cone shape such as a Thunder&Colt will develop a much faster terminal descent rate than a Cameron Viva (8 bulbous gore) or a Firefly.

My Firefly 7 (older Flexnet design) with a normal load would get up to 800 to 900 fpm terminal descent. My Viva 77 did about the same. A T&C 12-gore 7 would develop closer to 1200 fpm. The newer shape Firefly envelopes with the higher load capacity will have slightly more drag.