Thanks av8boy. Whilst I do not know if the crew were using this particular chart, it does illustrate many of the typical CFIT traps when flying NPAs.
This is not to speculate on the cause of the accident or give any reflection on the crew’s performance, but accidents as sad as this often enable improvements in safety through open discussion.
The airfield appears to be uncontrolled, ATC from Kansas center, but using local QNH?
MSA is 3100 ft but there is no chart shading indicating high ground.
The DME is remote from the airfield.
Two DMEs are used in the straight-in procedure; an opportunity for error, forgetting to change over from MCM thus descending at the incorrect range. Anyone done that before?
How far is MCM from IRK?
An open descent, only one check height at 2500 ft does not facilitate a stable constant angle approach.
No table of range against altitude.
Non std approach angle 3.41 deg, not coincident with VGSI. (why, procedure design?)
Minima 1320 ¾ nm; ie MDA 1320 (400 ¾) or (356 ft above threshold alt). At MDA the aircraft is just over 1 nm from the runway, or 1 nm from the beginning of the approach lights. Thus in limiting visibility the crew would not see the lights or the runway when at MDA.
Where is the MAP, at IRK 1.1 DME, i.e. at the runway threshold? Why not at 1 nm from the threshold for S-36 approaches?
Please bear with this one observation. The IAF/descent point is at IRK 10.2, which appears to be MCM 16.9. Thus if in error, the descent was commenced at MCM 10.2 (using the wrong DME) the aircraft would be approx 2100 ft below the procedure approach path. The aircraft would be at MDA just before the FAF, 4-5 nm from the field.