Criteria for circle approach

[BGSM]

Looked an approach for 8A0 Albertville AL they have an NDB to runway 23 the inbound course is 230 which is not 30 degrees or more but aligned with the runway its listed as circle only. What other criteria is there ?

 

[avbug]

The approach shows arrival over the FAF at 1,900' which puts it 868' above field elevation at 1.6 miles from the runway threshold, or 543'/nm if flying straight-in.

The criteria for establishing a straight-in approach with respect to TERPS, as found in FAA Order 8260.3B, with respect to descent gradient in feet/nautical mile is:

DESCENT ANGLE/GRADIENT. The OPTIMUM nonprecision final segment descent gradient is 318 ft/NM which approximates a 3.00° angle. The MAXIMUM descent gradient is 400 ft/NM which approximates a descent angle of 3.77°...When the maximum descent gradient is exceeded, straight-in minimums are NOT authorized; however, circling only minimums may be authorized if the maximum circling descent gradient is not exceeded.

What that boils down to is there's too much altitude to lose after you cross the FAF. This doesn't prevent you from executing a straight in approach if you see the airport and can get down using normal maneuvers and a normal rate of descent, but it does prevent the designers of the approach from publishing straight in minimums.

Identification of this fact is given in the use of the letter associated with the proceedure, NDB-A.

CIRCLING PROCEDURE IDENTIFICATION. When an approach procedure does not meet criteria for straight-in landing minimums authorization, it shall be identified by the type of navigational aid (NAVAID) which provides final approach guidance, and an alphabetical suffix starting with the beginning of the alphabet. The first procedure formulated shall bear the suffix “A” even though there may be no intention to formulate additional procedures. If additional procedures are formulated, they shall be identified alphabetically in sequence, e.g., VOR-A, VOR/DME-B, NDB-C, NDB-D, LDA-E, RNAV-A, etc. A revised procedure will bear its original identification.

 

[BGSM]

Info

Thanks for the info