Wind effect on Obstacle and Climb Limited TOM

[raul.jetpilot]

I am still 2 subjects away from my ATPL(A) and there is a something that I am having trouble understanding. It is one of the question in the Bristol DB.
It has to do with Obstacle and Climb Limited TOM.
I just don´t see how can tailwind affect OLTOM and no CLTOM...as I see it they are almost the same. The first requires an Obstacle Clearance and in order to do that we need a certain Climb Gradient, and the other requires a designated Climb Gradient. So both should be affacted by wind...or not...:ugh:
Any help?????

Thanks

[Alex Whittingham]

The Climb Limited TOM is controlled by the requirement to make a still air gradient - hence wind cannot affect it. The Obstacle Limited TOM is controlled by a requirement to clear obstacles by a given margin, and this is affected by wind. Headwinds improve the aircraft's gradient relative to the ground (and thus increase the Obstacle Limited Mass) and tailwinds degrade it.

The Climb Limited TOM used to be called the WAT Limit, because only Weight, Altitude, and Temperature affect the still air climb gradient. I've always thought that a much less confusing name.

[raul.jetpilot]

Thanks for the prompt reply!!!!...I guess the gap was "in still air"...now it all makes sense.

I also liked that WAT limit thing...:D

Best Regards

Raul