From Take Off to Landing: Understanding the Stages of a Flight

Introduction

Every aircraft journey follows a carefully planned sequence of events, from the moment the engines start to the final touchdown on the runway. While passengers may only notice takeoff, cruising, and landing, a typical flight is made up of several distinct stages, each with a specific purpose and set of procedures. 

This blog provides a clear overview of the different stages of a flight, helping you understand what happens from runway to runway and how each phase contributes to a safe and efficient journey.

The diagram has split a typical flight into various phases. Phases of specific importance to us are the take off, climb, cruise, descent and landing phases

Take Off

Takeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground (taxiing) to flying in the air, usually starting on a runway. Usually the engines are run at full power during takeoff. Following the taxi motion, the aircraft stops at the starting line of the runway. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine related problems. This makes a considerable noise. When the pilot releases the brakes, the aircraft starts accelerating rapidly until the necessary speed for take-off is achieved. The increase in velocity dramatically increases the lift force.

The takeoff speed required varies with air density, aircraft weight, and aircraft configuration (flap and/or slat position, as applicable). During take off an aircraft will typically deploy and extend the flaps by 10 to 15 degrees, increasing the wing area and camber and hence considerably increasing the lift generated. Air density is affected by factors such as elevation and air temperature, more lift is required when density is lower.

Climb

Following take-off, the aircraft has to climb to a certain altitude (typically 30,000 ft or 10 km) before it can cruise at this altitude in a safe and economic way. 

A climb is carried out by increasing the lift of wings supporting the aircraft until their lifting force exceeds the weight of the aircraft. Once this occurs, the aircraft will climb to a higher altitude until the lifting force and weight are again in balance. The increase in lift may be accomplished by increasing the angle of attack of the wings, by increasing the thrust of the engines to increase speed (thereby increasing lift), by increasing the surface area or shape of the wing to produce greater lift, or by some combination of these techniques. 

In most cases, engine thrust and angle of attack are simultaneously increased to produce a climb.

Because lift diminishes with decreasing air density, a climb, once initiated, will end by itself when the diminishing lift with increasing altitude drops to a point that equals the weight of the aircraft. At that point, the aircraft will return to level flight at a constant altitude. During the climb phase, it is normal that the engine noise diminishes. This is because the engines are operated at a lower power level after the take-off.

At this point, or just after take off aircraft will often begin a turn using a combination of ailerons to bank or roll and the rudder to combat adverse yaw. Aircraft may begin turning as early as possible in order to adhere to noise restrictions above urban areas or to avoid regions with high amounts of air traffic.

Cruise

Cruise is the level portion of aircraft travel where flight is most fuel efficient. It occurs between ascent and descent phases and is usually the majority of a journey. Technically, cruising consists of heading (direction of flight) changes only at a constant airspeed and altitude. It ends as the aircraft approaches the destination where the descent phase of flight commences in preparation for landing.

For most commercial passenger aircraft, the cruise phase of flight consumes the majority of fuel, as it is by far the longest portion of the journey. As this lightens the aircraft considerably, higher altitudes are more efficient for additional fuel economy. Typical cruising speed for long-distance commercial passenger flights is 475-500 knots (878-926 km/h; 547-578 mph).

Commercial or passenger aircraft are usually designed for optimum performance at their cruise speed. There is also an optimum cruise altitude for a particular aircraft type and conditions including payload weight, centre of gravity, air temperature, humidity, and speed. This altitude is usually where the drag is minimum and the lift is maximum. The aircraft will be in straight and level flight at this stage i.e not accelerating or changing altitude and so the thrust and drag force will be equal, along with the lift and weight.

Descent

A descent during air travel is any portion where an aircraft decreases altitude. Descents are an essential component of an approach to landing. Other partial descents might be to avoid traffic, poor flight conditions (turbulence or bad weather), clouds (particularly under visual flight rules), to see something lower, to enter warmer air (in the case of extreme cold), or to take advantage of wind direction of a different altitude. Normal descents take place at a constant airspeed and constant angle of descent (3 degree final approach at most airports). The pilot controls the angle of descent by varying engine power and pitch angle (lowering the nose) to keep the airspeed constant.

At the beginning of and during the descent phase, the engine noise diminishes further as the engines are operated at low power settings. Reducing the thrust of the aircraft and decreasing speed and therefore lift However, towards the end of the descent phase, the passenger can feel further accelerations and an increase in the noise.

Landing

Landing is the last part of a flight, where the aircraft returns to the ground. Aircraft usually land at an airport on a firm runway, generally constructed of asphalt concrete, concrete, gravel or grass. To land, the airspeed and the rate of descent are reduced to where the object descends at a slow enough rate to allow for a gentle touch down. Landing is accomplished by slowing down and descending to the runway. This speed reduction is accomplished by reducing thrust and/or inducing a greater amount of drag using flaps, landing gear or speed brakes (spoilers). During landing flaps can be fully extended to 20 degrees in order to drastically increase drag.

As the plane approaches the ground, the pilot will execute a flare (roundout) to induce a gentle landing. Although the pilots are trained to perform the landing operation, there are “Instrument Landing Systems” in most of the airports to help pilots land the aircrafts. An instrument landing system (ILS) is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument meteorological conditions (IMC), such as low ceilings or reduced visibility due to fog, rain, or blowing snow.

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