bickford frederick wrote: ↑Mon Nov 20, 2017 3:32 pm....I haven't ever flown with a drogue chute or seen one in person, just videos. What I'd like to know is how well you'd be able to recover airspeed if you lose it on final near the ground.
This is a important question. I'm glad you asked it and have phrased it well.
Although I have used several different types of drogues since 2008, I am only going to answer with respect to the 60" drogue that Dustin Martin sells and is manufactured by Free Flight Enterprises, who build the LARA reserve chutes for Wills Wing and the huge BRS chutes for the Cirrus airplane.
There are two modes of descending with this drogue: Waked and Clean.
If the drogue is being waked by an upright pilot and harness then its power decreases dramatically and this can be a very good thing if you need to accelerate quickly such as when dropping through a surface gradient or have hit a low-level wind shear, tree rotor or tree shadow.
If the drogue is running clean which is typical with a fully prone pilot its power is dramatic as in a 3:1 L/D at 38mph on a Sport 2 155 or T2C 144 in zero VG. So, let's say I'm going to land in a vacant lot surrounded by trees and buildings that create a very sudden gradient. But it's blowing 15-20mph at 300'AGL. Let's say I deploy the drogue just downwind of the field at 300' and pull the bar in and fly clean. I often find myself dropping at 1,000FPM and going backwards. Now I have two choices. I can slow the glider down while flying clean (and slow) which greatly improves my glide angle and penetration but my airspeed may be lower than I want it in turbulence. Alternately, I can go upright and wake the drogue while keeping my airspeed which will also improve my glide and penetration but my sink rate will be high. (It's fun the pull out the drogue at a few thousand feet AGL and just go thought these scenarios and get used to your glider's dynamics under each mode and any degree in between.)
So I'm dropping fast into this headwind and look down at the weeds in the vacant lot and don't see much motion. I know there is some combination of wind shadow and gradient waiting for me. At this stage I want to be at the downwind end of the field but not so far that if I stuff the bar I go backwards off the field. Typically what I do myself is bend my knees up while staying semi prone and dive for the ground. The airspeed of my vertical speed is less affected by shadow or gradient than my horizontal airspeed. Depending on different factors I will either transition both hands to the down tubes before I make this final dive or I will wait until I am in skim and near trim speed. I don't have a pat answer for this decision.
If I suspect that I may experience a sudden decrease in airspeed at round-out height, I will have my hands on the downtubes and be ready to flare in an instant. I have hit some strong surface gradient/shadows where I had to flare the glider as I was rounding out. The landings were lovely but it was weird diving down to the deck and just flaring rather than skimming first.
Now, if I have plenty of field ahead of me then I'd be more inclined to come in semi-prone with legs extended and wake the drogue. It's little different than coming in with the same posture and no drogue.
So there's this counter-intuitive paradox than users of a truly effective drogue have to get accustomed to. When coming up short you must do the opposite of what you would do without the drogue. You either need to get upright far enough to wake the drogue or you need to slow down enough that the drag from the drogue drops off and you can float your way upwind. In the latter case it's no different than landing a single surface glider. In the case of relying on body wake it becomes a new skill or habit to become familiar with.
The really great news is that these drogues tend to be so stable and predictable that your maneuverability is not affected. Do all the 360's, S-turn and figure 8's you like. It's just like throwing turns without a drogue except you may be descending several times faster than you would be doing without it. By practicing at altitude, the mystery in the glider handling goes away and you can focus on glide path angles and things like planning for preserving airspeed when dropping through a shear. You can actually do full patterns at altitude and simulate an entire approach all the way to a gentle flare-entry stall. Obviously, don't do a whip-stall into a tail slide except when actually landing.
I haven't found any video showing anything like this. There's math to do the calculations but I don't know the equations to make any estimate.
I have various aspects of this in different videos but not enough time to do a good edit.
Thinking about McClure, it might be best to go ahead and forget about shade in the LZ and get permission to cut down all the trees. Doing that would open up the area and there would be a lot less turbulence generated for safer landings. Also, no more pitch from the pines on gliders..
We are lucky at Crestline to have this large, open dirt aircraft carrier deck to land on. We can still have a bad gradient at the foot of the training hill and a wind shadow from our shade structure but it's tolerable.
The benefits of having a good drogue and being comfortable with using it are numerous. One downside is that landing can be easy like shooting fish in a barrel. When it's too easy, unassisted skills start to slip. I try to mix it up by landing with a drogue when I'd prefer it but can still land safely using prudent practice. Then I'll use it when I don't need it in order to stay current. See if you can borrow one from a local pilot or just get together with someone and buy one and take turns with it. Then decide if you want your own.
In my case I like to push my gliders to the limit and I want to be able to land okay in any of the many small lots or on roads and even downhill if needed. I prefer for others to think of the drogue as insurance. I think of it as a frequently used piece of gear that gives me new flying options. But I prefer that pilots do what right for themselves and there's a lot of variation and diversity.