Maximum Elevation Figure (MEF) - Sectional Chart
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- Опубликовано: 11 сен 2024
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One of the most important numbers on a sectional is the Maximum Elevation Figure, or MEF.
The MEF depicts the lowest altitude you can fly and still be assured to clear every obstacle within that quadrant.
MEF's are calculated two ways, one for natural obstacles, and one for man made obstacles. Each method ensures the highest level of safety and that as long as you stay above MEF you will be clear of all obstacles.
When a man made obstacle is the highest obstacle within a quadrant, the FAA uses the following formula to calculate the MEF:
Obstacle height (MSL) + 100ft
Round up to the next highest 100 feet and you have the MEF. For example:
Obstacle 750ft + 100ft = 850ft - Round up to 900ft
When a natural obstacle is the highest obstacle in a quadrant the FAA uses a different formula for extra safety:
Obstacle Height + 100ft + 200ft
Again, round the result up to the next 100ft and you have the MEF. For Example:
Mountain 3250ft + 100ft + 200ft = 3550ft - Round up to 3600ft
The 100 ft addition to both altitudes to ensure proper clearance when there has been an error in measurement, a slight deviation from plans, or for any other reason that the obstacle may be a little taller than originally measured.
The 200ft addition for natural obstacles provides extra clearance due to vegetation growth as trees get taller, buildings or towers that may have been constructed, or other items.
In areas where the contour interval for that specific quadrant is greater than 200ft, half of the contour interval is added instead of 100ft. So if that specific interval is 300ft, add 150ft instead of 100ft. These cases are very rare and occur only where there is a very steep elevation change.
The MEF is great tool to ensure you clear obstacles. If you are flying below MEF, make sure that you know where all the obstacles are. Towers, wires, and other man made structures are difficult to see from the air.
The MEF is also a VFR only number. It can be used in an emergency for IFR flight, but it is strictly designed for aircraft flying VFR.
Please let me know if you have any questions, and add your comments below!
Thanks for the feedback! This is just the first in a series on the VFR Sectional
Fantastic video. Valuable information presented very simply. Thanks.
Thank you for the detailed explanation!
Again, learned new things thanks to you. Thanks a lot
This video really helped me,thank you
Great video! Thanks!
Great Explanation!
2:25 I would have liked a more clear “We always round up to the next hundred” because it the number will always go up to the next 100, and never down
Great vid thanks
Thank you!!!
Great video even after all this years
When you say this elevation is what you read at your altimeter it means the elevation it’s MSL so you add 100 feet for handmade and you add 200 feet for natural made but when the elevation it’s in AGL what I know that you should add 400 feet but I look this up in FAA and every official source possible to my knowledge, and I couldn’t find anything it says that you add 400 feet for AGL elevation but is spread of word
Does anyone have a source for that AGL 400 feet addition?
thanks
Thank you =)
I believe you said the MEF is expressed in terms of MSL. I don’t fully understand why it would not be expressed in AGL. Can someone explain?
because the altimeter reads msl, therefore you have the same unit when you are actually flying. for example lets say youre flying at 7500 feet (as indicated on altimeter) you look at your chart to make sure you wont hit anything and it says that the mef in that area is 8000. you are too low and must climb! if the chart had the mef in agl, lets say a man made tower was 100ft tall, well if it only showed 100agl to you on the chart that would be useless and you would have to to a bunch of calculations in the air ! hope this helps
@@kaiblue5660 I don't think that's it.
@@Sky_Burger88 if the MEF's were in agl, a 100ft tower at the beach (sea level) would show the same mef as a 100 ft tower in the rocky mountains (14,000ft).
in this case we would read a 400ft elevetain MEF at the beach as well as a 400ft MEF in the rocky mountains, and we know there is a 14,000 foot difference between the two. keep in mind the altimeter reads msl, so at the beach when we look at our altimeter and it reads 14,000 and we look out the window we will be really really high up. likewise if our altimeter reads 14,000 in the rocky mountains and we look out the window, we would be really close to the ground.
still not make sense?
@@kaiblue5660 Not really. Look at a sectional chart. Obstructions such as antennas have both AGL and MSL heights notated.
@@kaiblue5660 What type of plane do you own?
Your NPR tone puting me to sleep; so will go elsewhere...
Hi i am new to hang gliding but when i looked at your chart you say 2463 is the height to look for but is this ment to be 2477 just under your number and a little to the right is this the number to look for it is heigher than 2463 i am learning charts so please forgive me if i have this wrong many thanks chris
You are right!
Excellent vid
Really? I am not sure if I understand you clearly but.....Did you say that MEF is a minimum altitude on which you can fly and avoid the highest obstacle? I dont think so, MEF DOES NOT include marigin for clearance. It shows you only the Highest elev and obstacle + not more then 100 or 200 ft for instrument error so you have to determine the alt to stay clear of obstacles.MSA for IFR DOES include the safe marigin....
www.faa.gov/air_traffic/flight_info/aeronav/digital_products/aero_guide/
hmmm not according to the faa...
Great video, thanks!