aircraft had recently undergone maintenance, during which the covers for the
indicator lights had been inadvertently
switched. The resulting indication when
the vacuum system failed caused the pilot
to get his mental wires crossed. Rather
than seeing a “Vacuum” failure indication,
he saw an “Oil Pressure” warning light.
Once he cross-checked all the instruments, he figured out the real problem.
He diverted to another airport where he
was able to have the failed vacuum pump
replaced. The sharks would have to wait.
The pilot of a Beech Model 35 (V-Tail
Bonanza) was beginning his initial
descent to his destination airport when
his confusion started. As he descended,
so did his airspeed. Thinking he had
inadvertently applied back-pressure to
the yoke, he trimmed the nose down to
accelerate to his normal descent speed.
Rather than increase, the airspeed indicator continued to unwind toward the
slow end of the scale.
Anytime an instrument responds
contrary to control inputs, a pilot is
bound to do some head-scratching. In
this case, relying on a single instrument
reading—the airspeed indicator—would
likely end up putting the aircraft in an
unusual attitude. The only way to sort
out what is wrong is to take a look at the
big picture. By cross-checking the
instruments (airspeed, attitude indicator, power setting, altimeter), we can
determine which instrument or system
is malfunctioning. The next step is to
readjust to the partial-panel situation
and continue to a safe landing.
The trouble is, in most of our training
it is obvious which instrument is incorrect; it’s the one the instructor covered
over. Unfortunately, when a real system or
instrument failure occurs, all the instruments may look like they are working.
Especially if we’re flying in other than
good VFR, it might be critical to sort the
problem out pronto, and the pressure can
build rapidly in the interim.
Fortunately, the Beech pilot reverted
to his training and was able to sort out the
issue. He configured the aircraft for the
descent with the proper power
setting and pitch attitude, and cross-
checked the altimeter. He got his head out
of the figurative clouds, recognized that it
was the airspeed indicator that was in
error, and covered it over to reduce the
distraction. Knowing the prescribed pitch
attitudes and power settings was the key
to overcoming the problem. It allowed
him to slow the aircraft below gear exten-
sion speed, lower the gear, and make an
uneventful descent and landing.
If our navigational
equipment gives us
“bad intelligence” the
situation can rapidly
spiral out of control.
Today we often rely heavily on precise
electronics to handle the navigational
details for us. Here again, if our navigational equipment gives us “bad
intelligence” about where we are and
where we’re going, the situation can
rapidly spiral out of control.
Consider the case of the two commercial pilots making a localizer approach to
their home airport in a Piper Archer (PA-
28-181). Undoubtedly, they were
comfortable with the approach, and
probably knew it so well they could draw
the instrument approach plate from
memory. Unfortunately, that didn’t prevent them from falling into one of the
oldest navigational pilot traps.
The first clue came when the approach
controller asked them if they were established on the approach. The PIC responded
in the affirmative; the localizer was dead
center on the dial, and the DME was clicking down at a reassuringly steady pace. A
short time later, ATC called again to ask the
pilot if he was on course. Now a bit irritated,
the pilot responded that he was on course
and approaching minimums.