What Happens When Reverse Thrust is Deployed Mid-flight?

Whenever I travel by plane, several questions linger in my mind. What if, what if, what if? One question, in particular, concerns reverse thrust: what would happen if it were deployed mid-flight? Would the plane crash? What are the possibilities that pilots might accidentally deploy reverse thrust mid-flight? These were concerns I had in my earlier days as a content creator. Anyway, that’s the beauty of my job; I get to learn more about aviation, which brings me more peace of mind.

So, returning to the subject, what happens if reverse thrust is deployed during mid-flight? Deploying reverse thrust on an airplane mid-flight disrupts the balance of forces keeping it airborne, potentially leading to a catastrophic situation. While reverse thrust is a crucial safety feature used during landing, its accidental deployment in flight can have severe consequences.

The Role of Reverse Thrust

Reverse thrust is a mechanism that reverses the direction of the engine thrust, essentially creating a braking effect. This is primarily used during landing to slow down the airplane after touchdown and comes into play in two main ways:

• In-flight thrust reversal: Some turbofan engines use a mechanism to redirect the exhaust flow through bypass ducts, directing it forward instead of backward. This creates a forward thrust opposing the engine’s normal forward thrust, acting as an airbrake.
• Thrust deflection: In turboprop engines and some turbofan engines, the propeller blades can be physically pitched to a negative angle. This deflects the airflow forward, again creating a braking effect.

Reverse thrust is a powerful tool for pilots during landing, significantly reducing the airplane’s landing roll and improving safety. However, its deployment during cruise disrupts the delicate balance of forces critical for flight. You can read more about reverse thrust here.

Mid-Flight Reverse Thrust

Deploying reverse thrust during cruise throws the airplane’s flight dynamics into disarray.

• Loss of Lift: The sudden reversal of thrust decelerates the aircraft rapidly, causing loss of lift. This disrupts the airflow over the wings, reducing lift and potentially causing the airplane to nosedive. Without sufficient lift, the airplane can lose altitude rapidly and enter an uncontrolled descent.
• Loss of Control: The disruption of airflow can also lead to a loss of control. The sudden change in forces acting on the airplane can make it difficult for the pilot to maintain control using the ailerons, rudder, and elevators. This can lead to erratic movements and difficulty in recovering from the situation.
• Engine Damage: The sudden reversal of thrust can put immense stress on the engines and their internal components. In extreme cases, it could lead to engine damage or even a complete engine failure.
• Structural Damage: The abrupt change in forces can also put significant stress on the airplane’s airframe. In severe scenarios, it could lead to structural damage or even a break-up of the airplane in mid-air.

The severity of the consequences depends on several factors, including the type of airplane, the altitude at which the reverse thrust is deployed, and the duration of the deployment. However, the potential for a catastrophic outcome is undeniable.

Safety Measures and Redundancies

Fortunately, modern airplanes are equipped with safety measures and redundancies to minimize the risk of an accidental mid-flight reverse thrust deployment. These include:

• Inhibitors: Many airplanes have interlocks or inhibitors that prevent reverse thrust deployment at high speeds or when the landing gear is not down or until the engines are in idle thrust. These systems ensure that reverse thrust can only be activated in a safe landing configuration.
• Pilot Training: Pilots undergo extensive training on the proper use of reverse thrust and the procedures to follow in case of an accidental deployment. This training equips them with the knowledge and skills to potentially recover from such a situation.
• Crew Coordination: Multi-crew airplanes typically have procedures for cross-checking each other’s actions, including the use of reverse thrust. This can help to identify and prevent any accidental deployment.

Just to give you an idea of what an accidental deployment of reverse thrust on cruise can do, in 1991 a Laudia Air Boeing 767 was flying from Vienna to Bangkok. Approximately six minutes after takeoff, the left engine’s thrust reverser deployed unexpectedly. The resulting loss of lift and controllability led to a steep dive and subsequent crash into a mountainside, tragically killing all 223 people on board. The investigation revealed a series of maintenance errors that contributed to the malfunction, emphasizing the importance of proper aircraft maintenance procedures.

I wrote this not to scare you, but to give you an idea of what could happen if reverse thrust were accidentally deployed. However, such incidents are ultra-rare today, as modern aircraft are equipped with safety redundancies to prevent the mid-air deployment of reverse thrust.