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Asked by: Dan Chitty
Airspace, FAA Regulations
When conducting a circling approach and when actually turning during the prodedure, does TERPS predicate the ABCDE categories and radii (protected airspace) assuming at the very least a standard rate turn?
Thank you for the feedback.
Wes Beard on Sep 18, 2013
The obstacle clearance plane or the protected airspace is a fixed radii from each end of the runway based on circling altitude (MSL) and aircraft approach speed.
You should never need to exceed a standard rate turn to remain within the protected airspace and make a normal approach and landing on the landing runway.
The FAA has recently revised the circling protected airspace and the new radii based on category and altitude can be found in the latest release of the AIM. Approaches that use the nee circling protected are indicated by an inverse C by the circling minima. See KSFO for an example.
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Dan Chitty on Sep 19, 2013
Thank you for the response and your mention of the new TERPS rules.
After review, I see that for A and B categories under the new TERPS circling guidelines that A and B cats. is assuming a 25 degree turn of which is at a rate greater than standard. I hope I have read correctly.
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Wes Beard on Sep 19, 2013
Where did you find the reference for 25 degree bank for Cat A/B minima? I can’t seem yo find a reference after a cursory look.
Most autopilots use a max of 25 degrees of bank and any bank in excess of standard rate will keep you inside the protected airspace.
There is a circling approach article in the Sept. 2013 issue of IFR Refesher magazine. The 25 degree reference is in this article. The article discusses the new circling criteria. I discoverd the article after you mentioned the new TERPS criteria.
Let me know your thoughts.
John D Collins on Sep 19, 2013
Change 21 of the TERPS in 2009 included an updated method for calculating the circling protected areas. This change was not put into effect until last year and it shows on approach charts as a white C icon inside a black background. Both the old and new methods will be on approach charts until the approach chart is updated to the new standard. This process will take several years. The old holding radius values were fixed and did not take into consideration the altitude of the airport. At higher altitudes, aircraft have a higher TAS at a given IAS and therefore turns are wider. The new criteria calculates the TAS and adds 25 to it. For category A and B aircraft the radius is based on an angle of bank of 25 degrees, for C and D it is 20 degrees and category E it is 22 degrees. To the calculated turn radius, a fixed amount is then added and for Category A, B, C, D, and E is respectively .4, .4, .5, .6 and .7 NM. These values won’t affect many approaches circling minimums for Category A and B, but are likely to increase the others. The TPP front material legend has a section on the new circling radius values that are used.
on Sep 19, 2013
The 25° bank for categories A-B, is referred to in the chapter on TERPS general criteria. It’s paragraph 260 in the Circling Criteria section (Vol 1, Ch. 2, Sec. 6). See Table 4 and the calculation above it.
I don’t pretend to understand TERPS (as Dr. McCoy might say, I’m a pilot, not an approach designer). Just passing on what I was able to find. It’s all yours 🙂
Wes, John, Mark
Thank you all for the feedback. All comments are greatly appreciated.
on Sep 19, 2013
When I got home I was going to check the TERPS documentation. You saved me the work. Thanks I appreciate that.
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