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Speeds to Fly

Postby Bob Kuczewski » Sun Jul 05, 2020 2:07 pm

The topic of "speeds to fly" can get pretty technical, and there are a number of resources available. This topic will start off with some general thoughts and may include those technical details later.

When people in hang gliding use the phrase "speeds to fly" they are generally talking about choosing speeds for optimizing flight time and/or distance (as in cross country flying). These differ from the immediate choices of speed needed for launching, landing, glider control, and obstacle avoidance.

The basic idea can be easily remembered by a pair of simple rules (first described to me by Joe Greblo during my training with Windsports). The rules are:

  • Fly slow in good air.
  • Fly fast in bad air.
It's easy to remember theses rules because you want to stay in good air as long as possible (fly slow), and you want to get through bad air as quickly as possible (fly fast).

So what is "good air" and "bad air"?

Good air is air that is helping you. This is usually lifting air and/or a tail wind. Bad air is air that is opposing you. This is usually sinking air or a head wind. What about mixtures like lifting air with a head wind? That's where things get technical (and beyond the scope of this introduction). For now, just remember that you generally want to fly slower in good air and faster in bad air. The reasons and exceptions will be developed in this topic.
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Re: Speeds to Fly

Postby Bill Cummings » Mon Jul 06, 2020 10:39 am

One exception to flying faster in bad air is flying
extremely fast on some modern double surface
gliders that are new to the pilots.
When HG started and with little exceptions we used
to hear pilot say, “Speed is your friend.”
As the higher performance double surface gliders
were coming out the big thing pilots were discovering
as the made their switch from single surface to double
was that flying near top end speed no longer felt friendly.
Still, flying faster than minimum sink speed (more on that
in later posts.) while in bad air is the better choice.
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Re: Speeds to Fly

Postby Bill Cummings » Thu Jul 09, 2020 5:53 pm

Pilot Gene Stone could not figure out how I was able
to return over the starting point of our tow road
with so much altitude. I was flying a single surface
glider and he was flying a newer double surface
glider. He hadn’t read up on speeds to fly.
He was speeding back before he sunk out and
that wasn’t working well. At high speed he was
offsetting his advantage by creating parasitic
drag and decreasing his glide over the ground
on his downwind leg. After telling him to fly
downwind at minimum sink speed (just above
stall speed.) he returned above the starting
point higher than me.
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