Notes for new airplane pilots--finding a
"true" visual reference point in an aircraft with side-by-side seating
December 18 2005 edition
steve at aeroexperiments.org
When I transitioned from sailplanes to airplanes, I noticed
that when I was flying from the left seat of an airplane with side-by-side
seating, I tended to let the nose drop and the airspeed rise during left turns,
and I tended to let the nose rise and the airspeed drop during right
turns. I realized that I was
unconsciously using a point near the aircraft centerline, on the top of the
cowling, as a visual reference point to judge the aircraft's pitch attitude
during my turns. As an aircraft rolls
into a left turn at a normal cruising airspeed, a pilot in the left seat will
see the centerline portion of the nose or cowling rise well above the horizon. As an aircraft rolls into a right turn at a
normal cruising airspeed, a pilot in the left seat will see the centerline
portion of the nose or cowling drop well below the horizon. If the pilot consciously or unconsciously
tries to "correct" this asymmetry, or if he inadvertently chooses a
visual reference point that is too close to the centerline of the aircraft, he
will end up letting the nose drop during turns to the left, and letting the
nose rise during turns to the right.
Of course, this problem has a very simple solution: a pilot
in an aircraft with side-by-side seating should pick out a "true"
visual reference point on the upper edge of the cowling or nose that lies
directly in front of him, and is not displaced toward the aircraft
centerline. The pilot should ignore the
fact that the majority of the visible portion of the nose or cowling rides well
above the horizon during turns in one direction, and rides well below the
horizon during turns in the other direction.
Instead, the pilot should focus entirely on the "sight
picture" created by the "true" visual reference point and the
horizon. If the pilot puts this
"true" visual reference point in exactly the same position in
relation to the horizon during left turns and during right turns, he'll avoid
the problem described above, and his maneuvers will be perfectly symmetrical.
In flight, it can be difficult to determine--to within an
inch or so--exactly which point on the upper edge of the cowling or nose lies
directly in front of the pilot. Here's
a tip on the easiest way to the chose this "true" visual reference
point. This tip will be very helpful
when a pilot is first learning to fly in an aircraft with side-by-side seating,
or is transitioning from an aircraft with centerline seating to an aircraft with
side-by-side seating. This tip will also
be helpful when a pilot who usually flies from the left seat of an aircraft is
flying from the right seat, or vice versa.
This tip will also be helpful whenever a pilot is transitioning to a new
type of aircraft.
Here's the tip: it is much easier to find a
"true" reference point on the upper edge of the cowling or nose, lying directly in front of the pilot, while an aircraft is taxiing than it is
during flight. As you taxi to the
runway, keep the centerline stripe of the taxiway directly under your seat, so that the taxiway centerline stripe
projects straight ahead of you without slanting the slightest bit toward the
left or right, as seen from your perspective.
Then simply note and memorize the exact spot on the far forward edge of
the nose or cowling where the taxiway centerline stripe intersects the edge of
the aircraft and passes from view, as seen from your perspective. This spot is directly in front of you. This spot will probably be much closer to the
edge of the nose or cowling, and much further from the aircraft centerline,
than you would have guessed. If you use
this spot as your "true" visual reference point during turns and
other maneuvers, then your maneuvers will be perfectly symmetrical, and you'll
have no tendency to let the nose drop or rise when turning in one particular
direction. Be sure and choose a spot
that is as far forward on the aircraft as possible: this will minimize the
changes in your "sight picture" that would be caused by slight
changes in the position of your head.
Naturally, this technique of choosing the "true"
visual reference point while taxiing will not be work in many tailwheel
aircraft, because the aircraft's nose attitude will be so high that the
centerline of the taxiway will be hidden all the way to the far horizon when
the aircraft is travelling straight down the taxiway.
If you don't have the chance to fly very often, and you would like to see these relationships for yourself, just be observant the next time you are driving a car down an a straight, empty road. Position the car so that the centerline stripe passes directly under your seat, and notice how easy it is to pick out the exact spot on the far forward edge of the hood that lies directly in front of you. Notice also that if you move your head a bit to one side, your "sight picture" will change much less--i.e. you'll introduce much less parallax error--if you are sighting on a spot on the far forward edge of the hood, than if you are sighting on a spot on the windshield that lies much closer to your eyes.
Errors from choosing the "wrong" heading reference point are most likely, and most critical, during landings. During the initial take-off, the pilot has recently had his memory of the appropriate heading sight picture "refreshed" by the taxi phase, but this is not true during a landing.
In general, the larger the aircraft, the further from the aircraft centerline the "true" heading reference point is for each pilot, and the more likely it is that a pilot new to the aircraft will choose a heading reference point that is too close to the aircraft centerline. For example, when I transitioned from a Cessna 152 to a Cessna 172, I noticed that on my first landings, I tended to allow the nose of the aircraft to point much too far to the left during the landing hold-off and flare, because I was unconsciously sighting on a point on the cowling that was much too close to the centerline of the aircraft. This is undoubtedly a very common error.
When a pilot who usually flies from the left seat moves over to the right seat, he will very likely choose a heading reference on the nose or cowling that lies too close to the aircraft centerline, and as a result will likely allow the aircraft to point too far to the right during the landing holding-off and flare.