Which statement correctly describes how MEA and MSA are calculated?

Which statement correctly describes how MEA and MSA are calculated?

• A. MSA is the altitude defined as the highest obstacle within 5 NM plus 1000 ft
• B. MEA is the altitude for an en-route segment that provides adequate reception of navigational facilities and ATS communications
• C. MEA equals Minimum Safe Altitude
• D. MSA is the altitude that provides 1000 ft clearance from the highest obstacle within 50 NM of the leg

Answer: (A)

In IFR planning, MEA and MSA serve different safety roles along and around a route. The minimum enroute altitude (MEA) is the lowest altitude you can fly between fixes on an en-route segment that guarantees two things: continuous reception of navigational signals (so you can determine your position) and sufficient obstacle clearance along that segment. It ensures you won’t lose nav aid coverage or run into terrain or obstacles between the fixes. The minimum safe altitude (MSA) is determined to protect you if you’re navigating near a specific navigation aid. It uses a defined radius around the facility (commonly 25 nautical miles) and gives you a altitude that provides at least 1000 ft of obstacle clearance within that area (2000 ft in mountainous terrain). The height is based on the highest obstacle within that radius and then adds the clearance. Looking at the statements, the one that correctly describes MEA and its role in en-route planning is the description of MEA as the altitude for an en-route segment that provides adequate reception of navigational facilities and ATS communications. The other descriptions misstate the radius (5 NM or 50 NM), confuse MEA with minimum safe altitude, or imply the wrong basis for MSA. The standard calculation for MSA uses a defined radius around the facility (not 5 NM or 50 NM) and adds 1000 ft (or more for mountainous terrain) to the highest obstacle within that radius.

In IFR planning, MEA and MSA serve different safety roles along and around a route. The minimum enroute altitude (MEA) is the lowest altitude you can fly between fixes on an en-route segment that guarantees two things: continuous reception of navigational signals (so you can determine your position) and sufficient obstacle clearance along that segment. It ensures you won’t lose nav aid coverage or run into terrain or obstacles between the fixes.

The minimum safe altitude (MSA) is determined to protect you if you’re navigating near a specific navigation aid. It uses a defined radius around the facility (commonly 25 nautical miles) and gives you a altitude that provides at least 1000 ft of obstacle clearance within that area (2000 ft in mountainous terrain). The height is based on the highest obstacle within that radius and then adds the clearance.

Looking at the statements, the one that correctly describes MEA and its role in en-route planning is the description of MEA as the altitude for an en-route segment that provides adequate reception of navigational facilities and ATS communications. The other descriptions misstate the radius (5 NM or 50 NM), confuse MEA with minimum safe altitude, or imply the wrong basis for MSA. The standard calculation for MSA uses a defined radius around the facility (not 5 NM or 50 NM) and adds 1000 ft (or more for mountainous terrain) to the highest obstacle within that radius.