Challenged
Pattern Altitude
"More than 40 years ago, Bateman invented the "ground proximity warning" system that prevents pilots in poor visibility from flying a perfectly functioning airplane into a mountain or some other obstacle."
http://seattletimes.nwsource.com/html/businesstechnology/2017426408_bateman05.html
http://seattletimes.nwsource.com/html/businesstechnology/2017426408_bateman05.html