Understanding “WHAT IS REMOVE BEFORE FLIGHT?”

“WHAT IS REMOVE BEFORE FLIGHT?” asked my good friend Sam while flying to Boston last week. He was looking for answers and couldn’t understand why the Flight attendants told us there is a chance the aircraft might not fly again. No one explained the simple reason why that is – we have a hydraulic pressure regulator in the fuel lines, which allows us to reduce the thrust by reducing the pressure in the fuel tanks.

The thrust is due to lift created by the drag of the air over the wings. If you were to add weight to the aircraft, you could add drag force, but it would add thrust as well, just as adding weight to an automobile creates lift. We can add a drag chute and reduce the amount of thrust needed for our aircraft’s lift, but we would still have the same weight and performance. There are a number of ways to do this, but the main concept is lift adds drag. You can add a parachute at the end of the wing or forward to the fuselage and/or rear of the aircraft to create additional drag, which would lower the angle of attack and create less lift for the aircraft.

If the aircraft’s main structure was light, it would also decrease its weight and increase its lift, since lighter weight generally equals higher airspeeds. So, if the aircraft was only one light part (wing, fuselage, and engine) how much drag would it add? Well, for a short period, it would take more energy to raise that aircraft’s altitude, and the energy would need to come from somewhere, so it would stop at higher altitudes and slow down as it got closer to the ground. So, the more weight you added, the less vertical lift your aircraft would have remove before flight.

In order to create lift, the airspeed required needs to be greater than the aircraft’s weight. The only way to create more lift is to increase the airspeed, and the only way to increase the airspeed is to increase the angle of attack. However, increasing the airspeed and angle of attack simultaneously isn’t possible, and would defeat the purpose of the concept. It is for this reason that the most popular configuration of the wing is straight (no naps), which requires the least amount of energy to keep it going. When an aircraft isn’t moving, it stops moving – it can’t move at all.

Any energy that is spent to move the aircraft will always have a corresponding amount of energy that comes back as drag. The more energy you use, the more drag you will have. In fact, an increase in airspeed or even just a couple of knots can make a huge difference in the amount of drag on an aircraft produces. This can be compared to the difference between jogging on flat ground and running on a runway. Jogging has more rolling resistance while running on a runway has more rolling stability.

An increase in the lift also increases the angle of attack required to counteract the increase in weight. The greater lift allows the aircraft to turn more quickly and to pitch much better. It would therefore be easier for an aircraft to climb to a higher altitude with the same amount of energy spent. However, to counter this, a pilot would have to add a tail to his aircraft or maneuver the aircraft so that he is taking off at a high angle of attack, decreasing the amount of lift he is creating.

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