On Thursday, June 11, 2015 at 5:38:16 PM UTC-7, wrote:
The only caveat I'll add (again repeating something said already) was that I'm using G-loading to mean lift force / weight.


Maybe this is a clearer system of terminology:

Total g-loading = net aerodynamic force / weight

Lift-wise g-loading = lift / weight. This is the g-loading component that acts in the direction of the lift vector, i.e. perpendicular to the flight path. A conventional panel-mounted g-loading measures something very close to this. Excess amounts of this kind of g-loading is usually the reason pilots pull the wings off in clouds.

Drag-wise g-loading = drag / weight. This is the g-loading component that acts in the direction of the drag vector, i.e. parallel to the flight path. This component of g-loading is large in very steep dive. This component of G-loading has little effect on a conventional panel-mounted g-meter.

In unbanked steady-state flight in a glider, L D and W form a closed vector triangle. Thus the magnitude of L is dependent on the L/D ratio, and increasing the drag coefficient by opening spoilers or lowering landing gear does decrease L and also does decrease the lift-wise component of g-loading.

I don't know if the recent reference to trolls was aimed at me, but see my June 3 post and my June 4 post presenting the table of lift/weight at various bank angles and L/D loadings-- I was responding directly to Dan Marotta's question. I was not trolling for contradictory responses. Nonetheless several people disagreed with these posts, and away the discussion went in a typical internet spiral.

For high L/D ratios, we can substantially increase D and cause only a tiny decrease in L, unless the bank angle is really extreme. I never said otherwise-- the table I posted on June 4 shows it-- yet there is still SOME reduction in L, and to say otherwise is to ignore the L D W vector triangle. For much poorer L/D ratios, increasing D makes a much larger reduction in L, especially when the bank angle gets above 45 degrees or so. The terminal-velocity dive is an interesting extreme case where L/D is zero, and thus either L is zero or D is infinite. It the real world it is always the former case.

All this is kind of peripheral to looking at the immediate effects of deploying the spoilers, because the decrease in L is quite small when we deploy the spoilers starting with a typical sailplane L/D ratio, and I said as much in my June 3 reply to Dan. If folks hadn't wanted to argue, the discussion wouldn't have spiralled so far away from the original topic.

S