What is MSA (minimum safe altitude)?
When you plan cross-country navigation how do you pick MSA?
Thank you very much for great answers. Sorry I missed an important detail. I need MSA for a VFR PPL cross-country flight plan on a half a million map.
- Anonymous9 years agoFavorite Answer
You can use various things to pick an altitude. Generally you will either have a specific departure plan (SID--Standard Instrument Departure) that will take care of safe altitudes or if there is no specific SID and the airfield has been assessed, you maintain a climb gradient of 200ft/NM to enroute altitudes. Obstacles are assessed as being below 156ft/NM in that case. Some SIDs require higher climb gradients or a portion to be completed visually (which requires a higher ceiling and visibility).
Enroute there are the MEAs (Minimum Enroute Altitudes) for a specific portion of airway, Safe Altitude 100NM (usually from you destination), Minimum Sector Altitude (25NM away and sometimes divided into different quadrants), and then the altitudes presented on the STAR (Standard Arrival) and the Approach Plate itself.
Additional safe altitudes are vectoring altitudes when under radar control and Area Safe Altitudes marked on a LO Chart.
Your altitudes are also dictated by cruising directions (ODD East), traffic, and the capabilities of your aircraft (pressurization, RVSM, etc) and can be amended for better weather (to get out of icing or for better winds, etc).
- Anonymous9 years ago
depends from your type of operations ANDlegal requirements.
on of general applied rules is that for IFR / inadverent IFR, stating that you have to maintain at least 1000 ft above the highest elevation [including structures on top] that is less than 3000 ft AMSL, OR 2000 ft above the highest elevation that is more than 3000ft AMSL, rounded up to nearest higher IFR cruising flight level. you scan for this elevation within 5NM off your planned route.
added to that, we use the "recommended" night VFR, which is 500ft above the highest elevation along your flight route.
like lowlevel said, you often meet the MSA as minimum SECTOR altitude on approach plates. that one is based on terrain obstacles within the 25NM radius, broken down to sectors from the airport reference point.
minimum radar vectoring altitudes are infnluenced by radar coverage rather than influenced by terrain features.