This post is inspired by the front page article today regarding the use of analog or digital altimeters. For some background - I only recently got my A license (hooray!) but I have been flying for years in private aviation and with the military. Many of our flight operations are conducted in the low level environment which has allowed me to enter the sport with an already modestly developed sense for altitude awareness and sight picture. Understanding this I'd like to tell you what happened to me on a recent jump and get some feedback. It was my first jump off of the AFF and coach program from full altitude. While for the most part it was a beautiful day, the sky was pocked with an approaching storm front. We were jumping on what was to be the last load of the day. The aircraft climbed up to 12.5 over the DZ and entered the jump run. I was #8 to exit behind a 4 way belly and a 3 way coach and I was followed by solo. The exit went fine and I spent my jump practicing some turns since it was my first full altitude by myself in awhile and I knew I was rusty. At about 5000 feet I ran out of things to do and started checking my airspace for when I pulled at 3500. I scanned the horizon real quick and looked back at my altimeter, it read 4.5. I looked around again and looked back at the altimeter, this time it read 4.0. I looked down at the ground and the eerie feeling that something wasn't right started tingling. The ground was way too close and I decided that my altimeter was the limfac and did what was beat into my head by the instructors at the DZ when something isn't right. I waved and pulled. As I did so I saw that the guy who had gone out after me had managed to track into my airspace and deployed probably about 300 feet in front of me. I grabbed the riser and banked it hard towards the DZ and managed to get a glimpse of my altimeter pointing to 2500. I sincerely believe there is no way that I had descended 1500 feet between pulling and being fully open because that sucker had popped fast. Sine I had the guy that had pulled in front of me as a frame of reference for my deployment altitude I met up with him on the ground and asked what he had seen when he pitched. He said he threw it at 3500 but that was the time I was reading 2900. We were both using the same system and had a 600 foot split with the variables being our rate of fall which caused me to not suspect the device on my arm but the pressure change as a result of the approaching storm system. My question then, is this something that any of you have seen? How do atmospheric conditions outside of meteorological phenomenon affected your equipment? Is there a digital system that posts your descent rate in real time that would have clued me in to crossing a pressure boundary like that?
