Why Don't Military Jets Have Reverse Thrusters or Brakes Similar to Commercial Airliners?

Many people wonder why military jets do not have reverse thrusters or brakes like commercial airliners. In fact, some military aircraft such as the Convair Delta Dagger F-102 and Delta Dart F-106 did have reverse thrusters in the past. However, there are several reasons that have led to the current design choices.

History of Reverse Thrusters in Military Jets

Historically, military jets did possess reverse thrusters. The Convair Delta Dagger F-102 and Delta Dart F-106 are two examples. These thrusters served a purpose but were later phased out due to certain drawbacks. Thrust reversers add weight, increase complexity, and are not compatible with the variable nozzles currently used in modern fighter aircraft.

Instead of thrust reversers, these fighter aircraft often rely on drogue parachutes for land-based operations. On aircraft carriers, multiple arresting cables are used to decelerate the aircraft upon landing.

Braking Systems on Military Aircraft

It's worth noting that not all military aircraft lack reverse thrusters. Aircraft carrying cargo and even some combat aircraft do have them. However, for fighter jets, drag chutes are typically more practical and efficient for decelerating during landings, as they help save weight and simplify design.

Why Reverse Thrusters Are Not Used in the Air

Despite the benefits of reverse thrusters on the runway, they are not employed in the air for safety reasons. Using reverse thrust while airborne is highly dangerous for several reasons:

It robs the plane of forward momentum, as engines cannot work in both directions simultaneously. The plane needs to move forward relative to the air to maintain flight. Reverse thrust in mid-air would slow the plane down, making it difficult to keep in the air. Reverse thrust would push air under the wings, potentially causing loss of lift, which is essential for keeping the plane airborne.

For these reasons, military jets regularly use drag chutes for deceleration on landing, while in the air, they rely on their aerodynamic design and other methods to slow down during maneuvers.

Special Cases

There are exceptions, such as the Swedish fighter JAS 37 Gripen (though not officially called the Viggen, this fighter was a previous model), which was designed with reverse thrusters for short landings on normal roads.

Other aircraft, like the Panavia Tornado and SAAB Viggen, have conventional reverse thrusters. The Harrier aircraft, being capable of vertical takeoff and landing (VTOL), can rotate its vectored nozzles past 90 degrees, effectively functioning as thrust reversers.

While reverse thrusters can be beneficial in certain scenarios, their use in modern military jet design is limited due to weight, complexity, and operational safety. The strategic use of drag chutes and other aerodynamic features ensures the safe and efficient operation of fighter jets.