Many times I had heard people talking about the airplane's
autopilot system ( AP ) as if it's a magic button. press one button
and the aircraft flies the plane from take-off to landing. This is
a misconception. I would like to clear this up as layman as I can.I
am sure many had heard of the following joke : Pilot's job is to
feed the dog in cockpit who will inturn bite the pilot if he
attempts to touch anything. The autopilot system is designed to
assist pilots in reducing most of the mundane workload of flying.
It cannot do an auto-take-off, that is still a manual human action.
THink of it as your secretary or personal assistant, they cannot
make decisions for the bosses but will assist in completing most of
coordination, typing, administrative functions. the pilots still
monitor, perceive and COMMAND an action, to either allow AP system
to take over or DISENGAGED to do do hands on flying because certain
actions are beyond what the AP system is designed to do. For
instance, AP can assist to hold an aircraft at an assigned altitude
as well as speed and also to warn of abnormal actions so crew can
make a decision to respond . AP does not work alone, it works with
others computers to make decisions n usually they vote to see who
has majority votes. Most modern airplane has 3 AP system, meaning
one for Captain side, one for Co-pilot and one backup. usually only
one AP is in control. When both AP are engaged, or what we called
DUAL, then it can perform autoland function on its own. Main
functions of the AP was to reduce crew workload there by reducing
fatigue which could lead to errors, flying today is so stressful in
comparison, airspace are conjested, slots are back to back,
separations are 15mins, there are so many restrictions n
requirements from ground to airspace performance that without the
AP , crew would have stressed out at Top of Climb, imagine flying
nowadays for 18 hours up there. The Trident was the first airplane
to have a triplex Auto pilot system because it was designed to land
in foggy conditions in UK. There are Dual Active failure, Passive
failure AP systems , meaning when the AP system gives up it will
show Fail Passive, when there is a problem n the AP can take
recovery functions because it is within its parameters, it will
show Fail-Active. ( crew to monitor n finger on red button to take
over ). Airbus is at the forefront with its Alpha Floor protection,
etc. I am sure if one is to google, one may find some notes on it.
too long for me to write it. Now, the AP system is only as good as
the Flight Data Computer brain. if the Nav DB has a stored
waypoints n company routes built-in, the AP system can fly the
aircraft together with the INS and other flight control systems
after airborne to landing. However, AP systems has its limitations.
n crew must know its limitations. for example, while AP or autoland
system can land an aircraft in thick fog, or what we call a CAT 3
landing, ( i will spare the details about Autoland Minimums ), it
cannot be initiated in tailwind or crosswinds conditions. Usually
not all airports will allow autoland. Usually when airplane is
lined up ( meaning straight on runway at final approach phase )
crew will disengaged AP ( there will be a crickety aural warning )
n land hands-on. So I hope folks will not think AP is just press a
button n do all. The human intervention will still be in place for
many years to come. As simple as I can, I hope it clears up the
misconception. I do welcome comments from other pilots or forumers
to add in accordingly. I have a pic of a Flight Director Control
Panel with AP instrumentations but I do not know how to upload it.
Perhaps some kind souls can help?
