Reacting to Engine Failure in Flight – Glide Approach

By

Home / Reacting to Engine Failure in Flight – Glide Approach

In an engine failure during flight, the aircraft loses its forward motion and falls through the sky. Photo Credit: Razvan Caliman

Whether you’re a novice, an experienced pilot, an engine failure in flight is a pilot’s worst nightmare. If it occurs in a single-engine aircraft, such as the commonly used Cessna – 172, or even a single-engine jet plane, there are only two ways out: trying to restart the engine, or making a forced landing.

An engine failure in flight requires a swift reaction by the pilot in command to maximize the flight of an airplane after the event has occurred. Pilots do this by acquiring a glide attitude and a glide speed at which the aircraft will remain in flight for a predictable period of time.

What Happens in an Engine Failure?

Lift, weight, thrust and drag are the four forces that primarily enable an aircraft to fly. In the event of an engine failure during flight, the force of thrust produced by the aircraft engine is reduced to zero. Consider an aircraft flying straight and level maintaining a certain speed and altitude. In the event of an engine failure:

  1. The force of thrust produced by the airplane engine goes down to zero.
  2. The force of drag (reactional force to thrust) produced by the plane dominates, and slows the speed of the aircraft.
  3. Decreased airspeed results in a loss of lift.
  4. The aircraft’s weight pulls it down in response to gravity.
  5. The airplane plummets to the ground and crashes.

The above listed happens if the aircraft attitude is maintained as it was before the engine failure occurred. However, practically, a pilot always tries to keep the plane flying at all costs, resulting in a change of attitude.

Understanding Engine Failure and How to Counter it

Without thrust, the plane cannot move forward. When an engine failure occurs during flight, thrust attains a zero value. The aircraft still moves forward for a little while due to its inertia, however, its forward motion will dissipate when the force of drag completely negates this inertial motion. There is, however, another way to move the aircraft forward without the force of thrust produced by the engines.

The weight of the aircraft is the only force that can somewhat propel the plane after an engine failure has occured. Photo Credit: Bryan Davidson.

Thrust Without Engines

Moving the airplane forward without thrust is done by lowering the pitch of the aircraft. Lowering the pitch of the plane counters drag, airspeed develops, and lift is produced. The amount of lift produced is, of course, not enough to support the weight of the airplane; nonetheless it is sufficient to increase the plane’s flight in air.

Glide: Why Do Pilots Glide?

When an engine failure is recognized (in a single engine aircraft), the pilot’s primary action is to put the plane in a glide configuration. Following are a few points in this regard.

  • The key is to attain a considerable horizontal component of weight that counters drag.
  • The required horizontal component of weight can only be attained at the best lift to drag ratio (L/D ratio).
  • Best L/D ratio is attained at an angle of attack roughly around 4 degrees.
  • Since angle of attack indicators are not available in most aircraft, the best option the pilot is left with is to achieve the “recommended glide or descent speed mentioned in the operating handbooks.”

Pilot’s Reaction to Engine Failure in Flight

As soon as an engine failure occurs in flight, a pilot must necessarily attain the recommended glide speed. Operating at the optimum glide speed, a pilot can maximize the time an airplane remains airborne, increase its glide distance, and steepen the aircraft’s approach to the ground. In this manner, an aircraft in distress due to engine failure can glide to a nearby runway or any clear ground to make a relatively safe approach. This process also provides the pilots with time to try and restart the airplane engine, analyze the cause of its failure, or prepare the aircraft and its passengers for a forced landing.

Resources

Federal Aviation Administration, Flight standards Service. Pilot’s Handbook of Aeronautical Knowledge. (2008).

Trevor, T. Aeroplane General Knowledge and Aerodynamics. Aviation Theory Centre. (2004).

Leave a Comment