Turn at an Altitude

28.10.2004

Submission:

The Missed Approach reads
"Climb to 1000'' then climbing right turn to 5000'' outbound via the MEM VOR R-323 to MREON INT/D18.0 and hold.

The above I just did in the simulator under direction of an instructor. I wanted to turn at 700 AFE which is 1000'' MSL for ILS 36L in Memphis with a TDZE of 321''. For our profile this would be right after selecting the Auto Pilot on at 600 AGL. The instructor said the Missed Approach procedure is only when the radios are out or if ATC says to execute the published missed. He said the "Climb to 1000'' MSL then climbing LEFT turn is only the minimum altitude to turn unless it says "MUST turn" for obstacle clearance purposes. In the scenario above I turned at or above 1300 - 1500 MSL which is just after selecting a climb on the Flight Director at VT speed approximately 170 kts. 1300 MSL is 1000 AGL which is our company's acceleration altitude.

My Question is: is what the instructor said correct that 1000 MSL is the minimum only for the turn and that I can turn a little later after the priority of taking care of the engine out profile?

MR. Robinson - USA

Answer or Commentary:

(I.W.

I personally have never seen an approach chart with a missed approach text that states "must turn", usually it is just "turn at..". Turns at a low altitude in a missed approach are almost always there for a reason (i.e. to avoid terrain, obstacles or other traffic). They are not put in lightly by the procedure designer.

A procedure designer calculates the exact position where an aircraft would reach the turning altitude using the minimum stipulated climb gradient (definitely the case with one engine out) and then after 6 seconds (3 seconds pilot reaction time + 3 seconds bank establishment) constructs the obstacle protection areas. Procedure designers do not take into account aircraft that climb straight ahead for more than the turning altitude. As you can see in the diagram, if you fly straight ahead to a higher altitude you are going to be a lot closer (or in) the terrain (i.e. an extra 500 ft at 2.5 % is an extra 6.1 KM).

I personally think that you instructor is wrong and it could potentially be quite dangerous.