Causes of altimeter failure?

Right. And these alts are designed to sample with a specific amount of air. That's why they give you calcs for port sizing. Windshear, sudden changes of direction, etc., can cause an inrush of air that confuses the software. at least that's my understanding.

I think the alts are generally more forgiving as far as port sizes, but if the previous picture is correct, I'm betting the pressure wave coming off the front of the nose cone isn't going to give the altimeters anything good to read.

mpitfield said:

The whole thing is odd that the OP asked for advice and then when it was given he dismissed so quickly. I am not sure what to make of that, except I would say to him don't sweat it there likely isn't one rocketeer who has replied to this thread that hasn't likely made a silly mistake. Personally I enjoy my mistakes because I learn so much, but not so much from the successes. You could look at it as the mistakes feed the need for knowledge and growth, whereas the successes feed the need for validation or ego.

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I enjoy seeing my rocket successfully complete its flight plan and not auger into the ground. Call me an egomaniac!

Yes, the OP asked for help, made us play 20 questions, and then took an overly-simplified conclusion - blame a drained battery. I highly doubt that the altimeter powered up fine and reported good voltage on the pad, only to immediately go dead as soon as the flyer turned his back and walked to the flight line. Possible, but not likely. I don't think a fresh Duracell will change the outcome of the 2nd flight.

I agree with rcktnut's interpretation of the av-bay. Is this a good way to sample the air pressure? Maybe, I don't know. I do know that the av-bay is in a stubby nose cone and of unconventional design. I would have ground tested and flight tested (with motor ejection) the hell out of this thing before committing to dual deploy with it.

I don't disagree with previous posts, but I did loose my L1 rocket to what I consider a battery failure. In my case, the battery had a hard drogue only landing. I flew it again in a rocket where the voltage was good, the altimeter beeped everything correctly, but the altimeter never fired a match and the rocket lawn darted. I'm still using the altimeter so I think it was a battery problem from the first hard landing.