Whoopedo
Here is a flavour of real low visibility landing. I don't think the Trident or any aircraft have ever done 0/0 in line service.
The Trident was crewed by three pilots, (a Captain and two Co-pilots). The
Captain sat in the left-hand seat and the P2 sat in the right hand seat and
P3 in the center seat behind the center console. P2 and P3 were equally
qualified and swapped seats leg and leg about or by the day or tour of duty
(however the wished). The aircraft was Triplex equipped (three Autopilot,
three Radio Altimeters etc.). Each of the three monitored the other two and
if one saw that it was at variance with the other two then it would switch
itself off and the appropriate warnings would be displayed on the flight
deck.
In this description of an approach, the weather is assumed to be at the
limits for Cat 3b. For the Tridents in those days, that meant a minimum
Runway Visual Range of 75 Meters at the touchdown end of the runway and no
less than 50 meters and mid point and far end of runway. The decision height
for this approach is 12 feet (Radio Height from wheels to ground). The
approach starts with Radar vectoring onto the ILS at about 2000 feet and
about 10 miles out. In these weather conditions an automatic landing is
mandatory. Any failure of a system, which precludes an Autoland, means an
overshoot from the approach and a diversion to an airfield where the weather
is suitable for a manual landing.
With the three pilot system and monitored approach of those days it was
mandatory that P2 flew the approach (controlling the Autopilot). The Captain
was not permitted to fly the approach in this weather. P3 read out all the
checklists and monitored the other two pilots to ensure that each check was
carried out. P3 was also responsible for monitoring the panels with
particular reference to the Radio Altimeters and various "Doll's Eyes" and
other indicators that denoted any triplex malfunction. He was also
responsible for the various verbal Calls that necessitated precise responses
from the Captain. With the aircraft established on the ILS localizer and
descending on the glidepath. P3 would read the Finals checklist (Gear with
one dot to go, land flap at the outer marker etc. - just like in the
simulator). P2 would be operating the various Autopilot controls (APR etc.)
and closely monitoring the main flight instruments, ensuring that the
aircraft was behaving normally and following the ILS closely. The Captain
would be monitoring his own flight instruments to verify the same thing.
At three hundred feet AGL, P3 would do a final check of various indicators
on the glare shield and assuming that all was in order he would call
"AUTOLAND TWELVE FEET". The Captain would reply "AUTOLAND TWELVE FEET". This
meant that the Autopilot would be landing and the decision height would be
12 feet. The Captain would now be peering out through the fog looking for
lights. He would have his hands on the yoke feeling the Autopilot control
movements. A bug had previously been set at 42 feet on the radio altimeters.
As the needle hit this bug, P3 would call "THIRTY ABOVE". This meant that we
were only 30 feet above the decision height. As the needle hit the permanent
bug at 12 feet on the center radio altimeter, P3 would call "DECIDE". There
must be an immediate response from the Captain to this call. He must
immediately respond with either "LAND" or "OVERSHOOT".
If the Captain called "LAND", this meant "I have control of the aircraft,
the Autopilot is going to land". P2 would slowly close the center throttle
as the Autopilot closed throttles 1 and 3. P3 would sit tight! As the wheels
touched down the Captain would press the button on the stick, which
disengaged the Autopilot and lower the nose wheels gently onto the runway.
The autorudder would remain engaged and attempting to maintain the runway
centerline by following a buried wire. As the nose wheels touched P2 would
pull up the reverse throttles on engines 1 and 3. To give full reverse
thrust. At 60 knots the Captain would call "reverse out" and P2 would cancel
reverse.
The Captain would manually brake the aircraft using the toe pedals,
disengage the autorudder at about 40 knots and if necessary use the rudder
pedals to stop the Barber's Poles streaming. If they stopped streaming left
or right, it meant you were on the centerline. In very thick fog the Captain
might have to call for radar assistance to turn off the runway and find the
taxiway centerline lights. Going back now to P3's "DECIDE" call at 12 feet.
If the Captain's response was "OVERSHOOT" or if there were NO response from
the Captain, P2 would slam all throttles fully forward. The aircraft, still
under the control of the Autopilot would rotate and climb away, without the
wheels even brushing the ground!
Finally, you may wonder just what the Captain had to see, in order to make
that "LAND" call….. Well, I'll tell you… He just had to see ONE LIGHT.