<My experience is that it's the second large correction that leads to
trouble. In other words small corrections and smooth flying get good
results most of the time. When you get distracted just enough that you
feel the need for a larger correction it becomes far more likely that an
over correction will occur. Trying to lead someone else through MCP
setting changes introduces the time delay that Vince talks about and really
sets you up for large deviations. There is a time for automation and there
is time to fly the airplane. I have seen very few people successfully fly
non precision approaches with fully coupled systems. Having the pilot
monitoring replace George at low altitudes can get interesting real fast.>
Reply:
I was unable to open the attached download file, so I may be
repeating points already covered. Concerning Gerry's comment above, the
size of the correction is not the best precursor of a critical error. My
airline flies almost exclusively hand-flown finals. Now, with the HUGS,
our CAT AIIIs are all hand flown. I have some observations:
1. Smooth inputs are important, but adverse weather often requires
large inputs to hold the correct flight path. I've been flying out of the
desert airports for the past few days and strong thermal activity required
significant pitch and power changes for a `stabilized' final.
2. The approach and landing phase is not any more prone
to"errors". In fact, I can confidently state that more errors are made in
other phases of flight. The difference is that the approach and landing
phase allows the least amount of `reaction' and `correction' time. Also,
down drafts, micro bursts, wake turbulence, and mechanical turbulence are
more pronounced at very low altitude.
3. A better focus on approach and landing difficulties centers on
the "transition to landing phase". Visual illusions, especially in reduced
visibility and night, cause pilots the greatest potential for error. For
this reason, I personally use the flight director and/or the HUGS on all
approaches.
4. As Vince has already observed, non-precision approaches are the
most problematic. This is because the flight director is dependent on your
input, which may be wrong. If you spin a 3000 FPM descent from the FAF to
the MDA, the flight director will dutifully give you that guidance. This
is an area where HUGS is especially helpful since the flight path cues, de
sent rate, altitude, radar altitude and runway environment are all in the
same visual field.
5. Aside from Autoland, FMC programming on established final is
questionable. Often, I feel that it is far preferable to switch to raw or
flight-directed ILS data and ignore the close-in FMC data.
6. As a CRM technique, I brief a doctrine I call "One In, One
Out". I've been using it ever since I almost ran my F-4 into the dirt at
500kts. At that moment, both the back-seater and I were looking backwards.
From that point on, I always briefed the non-flying pilot/crew member to
watch me and look elsewhere. Cockpit distractions have led to numerous
accidents over the years as all crew members have focused on the
distraction and stopped `flying the airplane'. As the PF transitions to
the visual environment, the PNF has to increase his/she cross check to the
flight director. It is a natural desire to transition to the visual after
you have been flying in the clouds for a long time, but the
disciplined/trained pilot sticks to his/her role and makes that required
deviation call-outs.
I hope this helps,
Steve Swauger
Southwest Airlines