"Roy,

You're certainly correct in that in the unbalanced force case (when the vehicle is still accelerating and drag forces are negligible), the accelerometer will measure an acceleration along the body-z axis of a magnitude (g / cos(theta)).…"

"Yep - I can confirm the U-Blox LEA-5H actually solves at up to 4Hz. The solution rate can be set independently to the reporting rate, and dead reckoning (interpolation) can be disabled if required.

I'm using it on a board which I've developed for a…"

"Then again, rocket pods are probably the last thing you want failing because of a faulty connector, right? In the military business you don't really get a second chance."

"In order to get roll/pitch information from a 3-axis accelerator, you need to assume that the only force acting on the accelerometer is that of gravity. For example, if the pitch was actually level and you accelerated the helicopter forward rapidly,…"

"Yes, that's true. I guess what I meant to say is that MEMS gyros generally have more sources of error which you need to compensate for (earth's rotation, linear acceleration effect, generally more sensitive to temperature), and often just have a…"

"I think the fundamental problem is that MEMS gyroscopes will always be perhaps an order of magnitude more expensive than MEMS accelerometers simply because of the greater complexity involved.

I've been working on an navigation solution of my own…"