B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 185; Flight Crew Type 11000
Workload; Troubleshooting; Distraction; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Company Policy; Chart Or Publication; Procedure
STL NATCA 2 SID (Runway 30L/R) requires a climb gradient of '500 feet per NM to WOLTR.' The Performance Chart ALL ENG data does not show fixes such as WOLTR. This situation requires the Pilot to notice the 'Direct distance from Lambert to St Louis International (Runway 30L/R) to: WOLTR 5 NM' in the fine print to the left of the SID ground track. And then the Pilot must do a lot of mental math.Minimum crossing altitude at WOLTR is 2500 feet. The field is approximately 600 feet MSL. Difference about 1900 feet. The track distance to WOLTR is slightly more than 5 NM since the chart says the 'direct distance' is 5 NM; but there is no way to actually calculate this difference. 1900 feet divided by 5 NM is about 380 feet per NM. Then the Pilot can check the Performance Chart ALL ENG data for 380 feet per NM up to 2500 feet.This process unnecessarily increases RISK. There are many opportunities to make a mistake in the above thought process. Further; many Pilots may fail to realize how to figure it out; or blow it off.Please try to have all SID required climb gradients expressed in simple feet per NM to a final ALTITUDE; and eliminate those that require feet per NM to a waypoint.
B737 First Officer discussed the complexity some aeronautical charts present when pilots are required to mentally calculate the required climb gradient in feet per mile on SIDs. For example; the STL NATCA2 RNAV did not have the calculation charted but did have a required departure waypoint minimum crossing altitude.