- Minimum safety altitude
Altitude specified at the flight planning stage as the minimum altitude that can be descended to in order to maintain safe terrain separation.
Generally, for VFR flight, a safe margin would be;
Take a terrain elevation of 1,250 ft above mean sea level; Round up to nearest 100ft; 1,300ft amslAdd 1,000ft; 2,300ft amsl is the MSA.
On VFR charts (e.g. 1:500,000), obstacles less than 300ft in height may not be shown. Check the chart legend to find out. In this case, there could be an obstacle at 299ft not displayed, on top of terrain at 1,250 ft.
Therefore good practice in this instance would be to factor the obstacle into the above: 1,250 = 1,3001,300 + 300= 1,600 plus 1,000 safety margin= 2,600.
Throughout the flight, in the event of bad weather an ATC instruction, or the need for an early descent into the destination, the MSA must be continually observed and should not be descended under.
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