Blip,
At least one operator of large aircraft with whom I am familiar specifically deals with the scenario you are pondering during every proficiency check and IRT.
First, a word of warning about relying too heavily on the take-off path planning or the straight ahead option.
Your normal large aircraft take-off planning in Oz is based on CAO 20.7.1B and commences at the departure end of the clearway with a total width of 500' or 152.4m expanding at 12.5% or 7.125 deg. That is not much more than a couple of wingspans in your 737-800 and given that the centre point of that splay is often 1-1.5 nm from your go-round point and is under the nose completely outside your field of view even in an OEI missed approach (during which I suspect you will predominantly be on the clocks maximising performance and configuration management), then there is a high probability that you will not be within the containment area. The normal survey is wider at 180m, but that is only an extra half a wingspan or so.
A better consideration would be to fly the missed approach flight path for a relevant runway aligned approach if available, simply because you are normally already contained within the lateral confines of the design area. How far you are below the relevant minima is then your major problem.
What are the vertical options?
Generally, but not always, your OEI approach climb gradient capability will exceed the take-off surface survey gradient at normal landing weights. However, it is worth consulting your AFM to get a handle on your aircraft capacity in various environmental conditions.
At Canberra for example, on runway 35 you would need a missed approach gradient capability of 2.5% from the ILS missed approach point and the DA minus sink-through allowance (2340-150=2190 or 320' AGL) or 3.2% from about 180' AGL or, assuming for simplicity a gradient capability increment of 0.1% per 20' above threshold elevation, about 4.1% from the flare.
These are approximations, since to do this analysis properly, you actually need to analyse the obstacles within the missed approach splay (a copy of which, by the way, the money-grubbing ar$$holes in AirNoServices will sell to you for $1500 per approach design!!). The above figures compare with about 3.9% if you could stay within the take-off splay, which excludes some significant terrain that is included in the missed approach splay. All this is approximated without provision for an acceleration altitude or consideration of go-round thrust time limits to reach a suitable MSA! However, it is a much better deal than the more generic cases described below.
What do we need to achieve if we want to abandon the missed approach at the circling minima and stay within the circling area?
Well, given that this is often the most commonly briefed plan (and performance delusion!), your climb performance needs to be good enough for you to achieve circling minima before the relevant circling distance minus your turn radius for the relevant speed so that you can remain within the containment area.
Continuing our Canberra 35 example, for Cat C you need to reach about 1600' AGL (for an OCH of 400') by about 3.5 nm from the runway departure end, a gradient of about 7.5% for the take-off case or about 5.3% from the flare (4.7% @ 180' AGL and 4.2% @ 320' AGL) at the landing threshold, both of which are fairly severe requirements, even if it were possible to satisy the circling manoeuvre requirements (which I totally doubt!!).
If you can't make those gradients, then you are going to end up having to consider the next safe height which is 10 mile MSA of about 3200' AGL in the general case but only 2600' AGL in the NE sector. The OCH is 1000' in both cases. In any event, if we arrive at, say for Cat C, 4.2nm from the departure end at 1600' AGL (the circling minima) we have no terrain clearance for the NE sector and minus 1600' for the general MSA. The gradient to get to that highly undesirable situation is about 6.3% for the take-off case or about 4.6% from the flare at the landing threshold. Even our previous gradients of 7.5%-5.3% for the circling provide us only with 240' of terrain clearance for the sector and 1360' underground for the general MSA.
If we want to get at least 400' between us and the ground, we need 7.8%-5.8% for the NE sector or 10.2%-7.5% for the general MSA. If we want the full Monty, then the required gradients are 10.2%-7.5% for the NE sector or 12.5%-9.2% for the general MSA.
Fortunately, most of our destinations are much less severe so the requirements are less limiting. My main aim was merely to highlight the need for good understanding of what you face, so that the resulting plan offers the greatest risk reduction.
Oh, and for those of you that like to forget that all missed approach procedures are three-dimensional, there is a sound reason for commencing missed approaches at or before the missed approach point if you wish to avoid some very complex mathematics and shetloads of uncertainty.
Stay Alive,
Last edited by 4dogs; 24th May 2004 at 10:58.