Expert: Jeff Davis - 10/26/2005

Question
What is the reasoning behind some class E airspace starts at 700 feet AGL, and some starts at 1200 AGL.  I know the rule and know how to identify which is which on a sectional, but what was the thought behind doing that by the FAA?

My only guess is at my home base we have an NDB approach which gets you down to 700 agl, thats why if our class E started at 1200 then on an IFR someone could go out in the pattern and using the "1 sm and clear of clouds" requirement for a class G airport and there may be some guy coming in on an NDB approach also, meaning a good chance for collision.  Whereas, if the class E starts at 700, he cant just fly around the pattern because now hes in class E and needs 3 sm and 500 below clouds?

But there are plenty of class G aiports with no instrument approach that fall under the class E 700 ceiling?

Answer
Thank you for an intelligent question.  Unfortunately, I don't have an intelligent answer.  You are correct in your reasoning about the conflict with instrument approaches necessitating the lower Class E limits around some airports.  As for those with no instrument approaches, my best guess is that the FAA wants to allow plenty of leeway for slow-climbing aircraft departing under IFR.  I used to fly a Cherokee 140 IFR, and if it was loaded I could use up a lot of miles looking at squirrels.  I don't guarantee that this is the right answer (hey, I'm an aerobatics expert, OK?) but it seems to make sense.