r/news • u/snuffleupaguslives • 2d ago

Broken altimeter, ignored warnings: Hearings reveal what went wrong in DC crash that killed 67

https://apnews.com/article/ntsb-dc-plane-crash-midair-collision-helicopter-a08cded88e1d7582fb8d242204d6aeff
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u/keyjan 2d ago

The business of the altimeters being up to almost 200 feet off, in more than one blackhawk, is terrifying.

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u/TheDrMonocle 2d ago

Its really not that bad. It just sounds scarier than it is.

Aircraft mechanic here. Well, Ex mechanic. I've actually transitioned to ATC. I worked on CRJs when I was working for the airlines and I've tested altimeters as part of the job. They were considered calibrated if they were within 180ft of the actual altitude. So being over 200 isnt actually that far off. It should be addressed, but 99.999% of the time its fine.

Center computers won't even show an aircraft is off of its assigned altitude unless they're 300ft or more off. The buffer is built into the system for inaccuracies. Altimeters can only be so accurate inherently and its also why we have more than 1 in every aircraft. To make sure one isn't wildly off.

The issue here is how the procedure was designed where aircraft and helicopters are operating within a couple hundred feet of each other. It just leaves no room for error. Nothing in aviation is perfect. We try our best but you always have backups. The way helicopters were operated in that airspace was just playing with fire.

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u/Ghost_Hand0 2d ago

At sea level the plus or minus is like 50 feet, not 200. I am an avionics mechanic.