Old 16th Nov 2014, 20:33
  #33 (permalink)  
Join Date: Oct 2010
Location: Styx Houseboat Park.
Posts: 2,053
Now that you mention it:-

One of the least mentioned parts of ATSB 200501977 is Appendix E, which deals with radio procedure and traffic. I have often wondered if some explanation for the last few minutes of the CFIT could not be drawn from this appendix. It seems, to me at least, to have been overshadowed by other events and the attendant hoo-hah. But IMO the 'conversation' between VH-PAR and the Metro is of interest.

From the report, the Aero Commander was inbound from the East and visual tracking for a left circuit to the same runway as the Metro; looking at the timing, it seems reasonable that the Metro would have been at decision height at or about the time VH-PAR could be expected around base or final. It is noteworthy that a discussion related to the ambient (cloud base) conditions was entered into, but establishing positive separation was not mentioned. Well, I can't find any reference to the aircrew attempting to establish positive separation from the opposing traffic. Potentially overshoot from the instrument approach would be conducted at low level, in poor conditions at about the time the aircraft VH-PAR would be in close proximity. The radio conversation leads me (for discussion purposes) to three speculative conclusions which are worth a moments thought, as an explanation to some of the questions.

(i) The crew had poor situational awareness related to conflicting traffic and had not considered, planned or briefed for a missed approach, including potential traffic conflict.

(ii) The increase in descent profile was triggered by a report of the cloud base from VH-PAR, that information prompting an increase descent rate on the expectation of becoming visual. (Radio call time line v Descent profile).

(iii) The determination to become visual and 'beat' the opposing aircraft into the circling area, thus assuring priority for landing had some bearing on subsequent command decisions.

The two aircraft were, potentially in conflict, the situation certainly worth more air time than it appears to have been given. From the report timing, the Metro was expecting the instrument approach minima at or about the same time as the opposing aircraft would be joining the landing pattern. Executing the missed approach procedure, the Metro would potentially be below and behind the conflicting traffic, the overshoot path being across the logical flight path of the inbound aircraft.

If LHR is to be discussed again then perhaps solving (discussing) some of the puzzles would be a much better use of time that time. I have always been curious about the ATSB report Appendix 3 and the lack of discussion related to it.

Any ideas, help me scratch a long standing itch?? Curse this curiosity bump.

Toot toot.
Kharon is offline