Class C Airspace


JWVideo
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Came across the attached question on a quiz in the course and am wondering if someone can help me understand my mistake.  The course defines Class C as "generally from surface to 4,000 ft AGL." The outer ring in the image shows 41/13, so I thought that meant 1,300 ft AGL. Does the outer ring always represent MSL? Am I not seeing a notation that tells me it's MSL? Something else?

Thanks in advance.

Class C Question.jpg

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2 hours ago, JWVideo said:

Came across the attached question on a quiz in the course and am wondering if someone can help me understand my mistake.  The course defines Class C as "generally from surface to 4,000 ft AGL." The outer ring in the image shows 41/13, so I thought that meant 1,300 ft AGL. Does the outer ring always represent MSL? Am I not seeing a notation that tells me it's MSL? Something else?

Thanks in advance.

Class C Question.jpg

I quote from the course, "Class C airspace is generally airspace from the surface to 4,000 feet above the airport elevation (AGL) (charted in MSL) surrounding those airports ..." (review the "Know Your FAA Airspace" lecture)

Confusing? Yes. But always think in MSL unless specifically noted on a chart. This will be on the test in one form or another (hint hint)

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  • 1 year later...

In aviation the altitude of the aircraft is always measured and expressed in terms of above Mean Sea Level (MSL) or Flight Level (FL)  These charts were made for aircraft altimeters set to a local altimeter setting based on pressure read from a calibrated mercury tube. This is why it is described as inches of mercury. 

This keeps everyone flying using the same reference level. 

You will notice the same thing for class D airspace. The radius is generally 4 nautical miles, (it use to be 5 statute miles but changed because most pilots use nautical miles for navigation) The class D airspace generally goes from the surface to 2500 ft AGL. 

As a UAV pilot your readings will be based on GPS altitude. And that altitude may not be the correct ground level for your area. Always cross check your data and don't scrape the top. 

 

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