BELL 412 EP Performance WAT vs Hover IGE vs Hover OGE

[ashfaq.ghori]

Hi,

I have a understanding WAT chart/Hover IGE performance to be used for takeoff from runway. Hover OGE performance for operations for helipads. And available takeoff Weight for WAT/IGE is more as compare to OGE.

I was checking IGE and OGE performance chart and was amazed to see hover limit for OGE (takeoff power with shaded Area B) were more as compared to WAT chart. (e.g IGE for 6000 ft @ 20*C is 10550lbs while OGE takeoff power with Area B is 11100 lbs)

Can someone explain it to me.... also when flying from high altitude say 6000 ft which chart to use for Runway takeoff and which chart for Mountain Helipad.

Regards
AG

[212man]

A WAT chart will be taking single engine performance into account, using the Cat A profile(s) whereas the OGE chart is purely all engines operating. I.e a WAT chart is not the IGE chart.

[malabo]

Use the WAT for both pad and runway, but don’t leave your brain and ops manual behind. There are reasons segments of the industry adopt different performance standards for specialized tasks.

Nick Lappos explained it perfectly last year. Here’s the link: https://www.pprune.org/rotorheads/592986-intent-behind-bell-205-212-wat-charts.html#post9726616