As you wish. I'm not. I had to go online this evening to make sure I wasn't crazy.
You initiated this portion of the discussion by saying: "What exactly is a low G dive? Does that mean you can do a High G dive? Do you mean that you performed a low G pull out from a dive?" Your tone was such that I, at least, thought you were belittling Sunka's post ("I lost my wings in a low G dive..."). So I responded that you can do a high-G dive, either positive or negative; and this is so. I tried it tonight, achieving approximately negative-4 Gs and positive-3 Gs in a G6 starting from 10k. The dives were not straight-line, obviously, because stick pressure is required to incur the Gs. Nonetheless, the plane plummeted down and hit the ground during the course of the experiment. Most people would consider that to be a dive. I'll be pleased to post the films here if you can guide me through the process; I made certain to adjust my head position so as to show the G meter throughout. It is quite possible - easy, even - to maintain a zero-G dive.
Now it may be that you assumed that the dive must maintain a constant angle (your post, "Please do it and film it. 5K will be enough alt to start from, say a 45 degree dive angle, to the ground, at 0G," suggests that this is what you have in mind). Probably you're correct in that case, because maintaining a constant dive angle will ultimately put you at 1 G. But that wasn't Sunka's post, and it wasn't mine, either.
- oldman
Traveler and you are both correct, actually.
The problem is that G's are actually a measure of acceleration, while the G-meter in the cockpit measures acceleration as it pertains to the load the wings have to bear (or rather, it measures how much the plane is "opposing" the forces its encountering).
In a "0G" dive (as measured from the G-meter), you're still under the influence of 1G of acceleration (gravity, aka "God's G"), but since the plane isn't opposing that G, the airframe experiences 0 load factor. Since you've unloaded the aircraft, your wings no longer have to produce lift, therefore the plane is functionally weightless (again, in terms of lift required to keep the aircraft in flight). The G meter will measure that the airframe doesn't have any opposition to the G-forces its encountering. However, you are still accelerating towards the earth at 1G.
The accelerometer/G-meter is measuring the
relative number of G's the airframe in experiencing, not the absolute number of G's present. When it shows as being under 0 G's of influence, it's simply stating the wings don't have to produce any lift (and all of the performance implications that comes with). It doesn't measure the actual pull of gravity, however. If it did, it would still read at 1G. If you level out into straight and level flight, you are now opposing God's G (it's trying to pull you down, while your lift vector is pulling you up) and the G-meter will show your airframe is undergoing 1G of acceleration (you're accelerating away from gravity at the same rate its pulling you down).
You are always undergoing 1G of acceleration in some aspect, it's just not always measurable from the cockpit.
So, again, you're both correct. A zero-G dive, as measured from the instrument panel and in terms of lift performance, is possible, but the plane itself is still under 1G of acceleration from God's G.
