The new Rnav SIDs for Chicago O’ Hare (ORD) and Midway (MDW) airports scheduled for release last week were declared “technically unusable” until further notice after a potential problem was identified at the last minute.
Previous SIDs used ground-based navaids that ensured crossing restrictions, such as “Cross 5 DME west of the ORD VOR at or above 3,000 feet,” could and would be met to ensure separation between traffic at the two busy hub airports. Somehow, the new SIDs were designed instead with instructions that require climb gradients be met. Under certain kinds of weather or aircraft load conditions the pilot-in-command, aware that the aircraft would be unable to meet the gradients, might refuse to accept the SID, threatening positive ATC separation and increasing workload for crews and controllers.
The FAA expects solutions will be found promptly to modify and reissue the Rnav SIDs with climb criteria acceptable to users, the FAA’s flight standards division and ATC.