Originally posted by RobG: In other words, they have to go to a much higher altitude on a missed approach than on a successful approach?
No, not necessarily, although
that may also apply; it means that the decision point to
begin the missed approach may have to start higher or earlier than otherwise necessary simply to ensure the missed approach path can clear all obstacles. (Mmm, a 'successful' approach ends on the runway. I presume you meant the beginning of the approach?)
The criteria for performance-based phases of flight is extraordinarily complex. It includes some
smack-your-forehead-kinda-stuff that would never occur to you without an in-depth introduction to the material.
E.g., wouldn't it make sense that
any climb profile criteria be based on an engine-out scenario rather than normal power. Things like, there's no need for climb adjustments for a single-engine aircraft (no engine, no need!) but there's a difference between two-engine and multi-engine (more than two) criteria.
Or, the gate tells you you can't board 'cause the flight's '
weight-limited' then you see it take-off and climb out like a banshee -- on all engines. But the controlling limit's based on the potential loss of an engine beyond decision speed (V1) and still being able to safely fly the
engine-out profile.
Whenever you observe
two-engine performance you're seeing about twice as much extra margin than the operative limits require for a two-engine aircraft. A very reassuring thing indeed.
Quote: . . . spiraling down into a loop closer to the runway than the approach the jets were using
Could have been a visual approach mixed with someone flyin' the instrument approach. Or there's such a thing as a "Circling Approach" where the instrument approach converts to a visual circling landing on another runway that doesn't have a published straight-in procedure.
[ I'm on a bit of a roll here this evening, Rob. This morning I completed a required re-currency review that verified that a 76-year old guy and a 47-year old aircraft can still '
get it up'. Then I came home an' took a nap!
]