I had an experience a few years ago. I had a 4" diameter, 5' tall rocket, with a central 29 surrounded by 3 more 29's, those were to be airstarted soon after liftoff. I had the rocket on the pad, with all the igniters hooked up, and armed the G-wiz LC-800. As I was looking into the vent hole to check the LED status, I heard a noise, and realized that a motor had lit. I spun around, and the rocket took off, about 2 or 3 feet away from me.
At first, I thought that the LCO had either launched it, or there was a fault with the launch controller. The rocket went less than 100 feet up, and nose dived to the lakebed. I discovered that the airstarts had fired on the pad. All 3 igniters had lit for the airstarts, but only 1 of the G-64 motors lit. The central H220 had not lit.
I had extensively ground tested this before flight, and everything checked out. When I go this home, I thought maybe I'd messed up on wiring this, but that was not the case. I tested this again several times, and it checked out perfectly.
I sent the altimeter back to G-wiz, with a letter explaining what happened, and told them I did not want it back.
A "g" motor is pretty loud from only a couple feet away. Here's a photo of how the rocket landed.
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