Va and a G-Meter

[alpinelakespilot2000]

Having never flown with a G-Meter before, but now having one built into the Dynon, I'm curious about how I might use it to determine when/if I need to use maneuvering speed. Previously, any time I flew through chop, I began to get nervous because I really didn't know how many g's that chop represented, so I was probably much more quick to go to Va than I really needed to be.

So, assuming the chop/turbulence is relative constant in degree, at what g-level reading would you go to Va? Or, more generally, how can I use the g-meter to manage my flight speeds? I'm asking this question from a RV-9 perspective where the load limits are +4.4/-2.2.

[Wayne Gillispie]

I slow down to 1.6-1.7 X clean power off stall speed which for me is 102-109 kts and less if I am solo or light. I prefer not to see less than 0 G or greater than 2.0 G's for my family or plane. Remember Va is to protect the structure at no power, full deflection of one control only, and in one direction only.

Thunderstorms or severe turbulence can destroy our planes at Va or less, hence the reason I stay much slower. Of course we all try to stay out of TS but it still happens VFR and IFR. Check out the ntsb reports for this years TS season here in the SE. I found three that were destroyed and one lucky guy bent up bad.

[alpinelakespilot2000]

Yes, I think anything more than 2.0 g's and I'd be slowing down, just for comfort if nothing else. Still just wondering if there's any rules based on the g-meter for when I really should be slowing down to Va.

[Vac]

Hi Steve,

Consider using the quality of the ride to determine when to to slow down in turbulence. As you said, Va is a great target speed under turbulent conditions.

The purpose of the g-meter is to work "maximum performance" at speeds above Va (corner velocity). Below corner, max performance is lift-limited, above corner it's g-limited. So, below Va, buffet provides a "max performance" cue, above Va it's a matter of reading the g-meter. Think of the g-meter as an "energy management" tool rather than a "ride quality" tool.

Turbulence may or may not register on a g-meter depending on the direction of the acceleration. A 2-G vertical acceleration as a result of turbulence is fairly significant, so slowing down at that point would be a good idea.

Another good rule of thumb is to concentrate on maintaining ATTITUDE, not altitude in a rough ride. Accept the altitude excursions. RV's have a light wing loading and are fairly quick, a recipe for a rough ride at high cruise or descent speeds in turbulence. "Fish tailing" (yaw excursions) are common with two-seat RV's under turbulent conditions.

Fly safe,

Vac