Originally Posted by
73qanda
I tend to agree with Porter. Crappy design.
A few rough estimates;
At 400 ft they’d be about 1200m from the MAPT as the crow flies.
They’d be doing maybe 82m/sec.
Time how long it takes you to say
ATC : “Qantas 123 this isn’t going to work, carry out the standard missed approach procedure”
QF: “ Ahhh understood standard missed approach procedure, Qantas 123 going round”
PF “ Righto, we’re gunna go round”
PM “ Yip”
PF “ Going round Flap fifteen”
three second pause for the actions
PM” positive rate”
PF “ gear up”
It takes me between 17 and 20 seconds if I do it at a pace I think is realistic/likely.
So now you’re 400m past the MAPT climbing back through 400ft and doing exactly as the procedure calls for, tracking 335 waiting for 600ft where you’ll begin your turn onto 070. How long does that take? 200ft at 1000fpm is another 12 seconds and 980m. So now, after flying the machine nicely, you’re 1.4km past the MAPT.
So my thoughts are that if everything goes really well, you’re going to be over the runway when you turn but very likely is that you’re going to be well down the runway as things rarely go exactly to plan. All it would take is one drawn out communication and you are turning where this aircraft turned having done the job very nicely.
Not to be pedantic, but there is a bit of a flaw with your theory. Your 17-20 second run of prep assumes the G/A around instruction was given at 400ft. The report shows they commenced the actual G/A at 400ft, which means all that stuff you've listed has already taken place by that point, and can't be included in your calculation of a reasonable position.
As for the debate about the G/A procedure. I too believe that ones pretty clear. You must commence the MAP from the MAPt, which is clearly defined as the intercept of the glidepath with the DA, about 0.5nm IKN. You cannot turn before then. Surely if ATC want you to do something in contravention to the AIP, they don't have to issue the published missed approach and can simply give you an alternative instruction.
Lastly, what are peoples thoughts on the readback of a G/A instruction? Typically I perform the G/A actions first, then read back later, especially if it is a time critical defensive action. I figure ATC can see what I'm doing, (similar to a PRM breakout where no readback is given).. Do people delay the G/A to make the radio call? I suppose if there is plenty of time there is no harm.