Hi,
Just wondering, in the July 2011 edititon (IREX), CIR Revision Set Ten Question 3
The answer says that I should use the Grid LSALT but I thought the book said that we only use this if unsure of our exact position. The question states that I have just passed over Clark, which means I know my exact position. Why am I still applying the Grid LSALT vs the Route LSALT?
Thanks
Grid lowest safe is safe for any position within the latitude/longitude grid. As long as you are sure that you are in the grid, you may descend to grid lowest safe. You probably would not use grid lowest safe if you were going to eventually leave that grid before arriving at your destination - it would make more sense to use LSALT for the route in that case.
If the AIP refers to LSALT, it is referring to the route lowest safe. For example if you are considering whether or not you need to plan an alternate to an aerodrome with no published instrument approach, you check the ARFOR to see if there is more than four eighths cloud below LSALT for the last route segment plus 500 feet. That is referring to the route lowest safe.
