The Truth About Aerodynamics
(What Really Makes Airplanes Fly)
Most aeronautical engineers and the general public associate the lift generated
by a wing with the differential pressure between the upper and lower surfaces
of the wing. Nothing could be farther from the truth.
In reality, the lift required to cause a commercial aircraft to become airborne
is furnished by the passengers and is inversely proportional to both the wing
size and to the distance to be traveled. Furthermore, the distance to be
traveled has a nonlinear relationship to lift, as will become clear in the
following explanation:
1. How Passengers Provide Lift for Commercial Aircraft
The lift required for an aircraft to take off is furnished by the passengers
pulling up on their seat armrests.
2. How Takeoff Lift is Initiated by the Pilot
After the aircraft reaches the end of the runway preparatory to takeoff, the
captain will advance the throttles on the engines. This action has two
purposes: a) to provide horizontal thrust to propel the aircraft down the
runway, and b) to increase the Passenger Aggregate Fear Level (PAFL) by raising
the noise level in the cabin. The consequent rise in PAFL causes the passengers
to strenuously lift up on their seat armrests, thus imparting lift to the
aircraft. As you can readily see, the engines have two purposes - to move the
aircraft horizontally and to scare the bejeebers out of the passengers.
3. How the Duration and Degree of Lift Are Modulated by the Pilot
Once cruising altitude is reached, the pilot will throttle the engines back to
lower the noise level. The reduction in noise level results in a reduction in
PAFL, with a consequent decrease in lift. It is necessary for the pilot to make
only minor changes in noise level to maintain straight and level flight. In
some instances where the PAFL does not decrease sufficiently to prevent further
climbing, the captain may order that free drinks be passed around, thus further
relaxing the passengers and lowering the PAFL. One may observe that on most
aircraft, the first-class passengers are automatically anesthetized by the use
of free alcohol. Clearly, first-class passengers are a source of surplus lift
and must be dealt with accordingly.
While the airline industry will never admit it, passenger seating assignment is
governed by national characteristics. For instance, Italian males are hardly
ever upgraded to first class since they are easily excitable, respond very
quickly to outside stimuli, and cause abrupt and unpredictable changes in lift.
Clearly, one would not want to get the Italians drunk. One difficulty associated
with using Italians in this manner is their clannish nature; getting them
evenly distributed (left and right, front and back) within the cabin can
sometimes be difficult. Stewardesses will often resort to eyelash-batting and
hip-wiggling to move the Italians about the aircraft.
While at first blush, it may seem that the French would also be a good source
of lift, their uncooperative nature makes lift modulation difficult. One should
never fly on an aircraft containing more than 45 percent (by volume) Frenchmen.
Note that Lufthansa, SAS, and KLM fly only very large aircraft.
Raising the PAFL for the stolid Germans, Swedes and Dutch is notoriously
difficult, requiring as many people as possible in each aircraft. The British
never fly.
The high takeoff-accident rate for Aeroflot can be attributed to the fact that
Russians are generally drunk before they get on the aircraft and are not a
reliable source of PAFL-induced lift.
Descent and landing are accomplished using a combination of fatigue and passenger
discomfort. It is a happy coincidence that travel over greater distances takes
a correspondingly longer time. Even the most casual observer will note that
after the aircraft reaches cruising altitude the plane will begin a slow and
gradual descent for the balance of the trip. This descent is due to passenger
fatigue and discomfort. A detailed explanation of the fatigue factor is
unnecessary; suffice to say that with time one's arms get tired and the upward
pull on the armrests is reduced. By reducing leg and hip room, passenger
discomfort is increased with time; this distraction is also sufficient to
reduce the Passenger Induced Lift, (PIL).
The common airline practice of showing only the most boring of in-flight movies
is also a lift-modulation technique.
Note: The decrease in the amount and quality of airline food has not been found
to be an effective method of PAFL modulation; biogas production offsets any
decrease in lift. (See Hindenburg Disaster, reference no. 75.)
Several recent instances of sudden aircraft descent have been attributed to air
pockets. The air pocket explanation is clearly a feeble attempt on the part of
the aircraft crews to avoid blame. In reality, the crew neglected to closely
monitor passenger fatigue, discomfort, or degree of inebriation. Luckily,
sudden decreases in altitude are self-correcting due to the consequent rise in
panic levels and increase in PAFL-induced lift.
Most passengers and the general public believe that the oft-experienced
practice of circling the airport many times prior to landing is caused by the
weather. This is not wholly the case. During bad weather, the PAFL increases as
the aircraft reaches its destination. This undesirable increase in PAFL and
consequent increase in lift must be dissipated by prolonging the flight and
further tiring the passengers.
4. Historical Basis for This Theory and the Role of PAFL in Aircraft Design
As you may recall from early aeronautical history, the Wright Brothers'
aircraft had four wings with a very large surface area. The large surface area
of the wings inspired great confidence in Wilbur and Orville, decreasing their
PAFL and, as a consequence, decreasing the altitude and flight duration
capabilities of the Wright Flyer. As aircraft design advanced, it was found that
smaller wing surfaces inspired greater PAFL, with a resultant increase in
aircraft performance. Indeed it was not until the advent of the multi-passenger
aircraft (with a higher PAFL factor) that increases in range and altitude were
possible. The only reason wings (albeit very small ones) are still included on
aircraft is that they look nice.
It is a little-known historical fact that the general unpopularity and eventual
demise of the supersonic passenger aircraft were brought about by the fact that
as soon as the aircraft reached supersonic speeds and altitudes, the passengers
could no longer hear the engines, due to the high speed and thin air. No noise,
no PAFL--and no PIL. The aircraft would drop like a rock, causing the PAFL to
spike drastically, and the aircraft would then climb precipitously back to a
high altitude, with the consequent loss of engine noise. As speed once again
increased, the process would then repeat. The resultant sinusoidal altitude and
speed changes thus rendered supersonic travel impractical.
While further research by highly annoying and pedantic people may bring this
theory into disrepute, one must keep firmly in mind that, even with all of the
airlines' efforts to reduce personal space aboard commercial airliners, they
have yet to remove the armrests.
Art Lynch
Avid Aviator Pilot Supplies
www.avidaviator.com