What is INOP on Boeing 737? (Inoperative)

The Boeing 737 is a popular commercial aircraft that has been in service for decades. With the continuous advancements in aviation technology, these aircraft have become more reliable and efficient. However, like any complex machine, there are times when certain components or systems may become inoperative. Inoperable systems can range from minor inconveniences to more critical issues that require immediate attention. In this article, we will explore the various components and systems that can be inoperative on a Boeing 737 and how they are managed.

INOP Items on the Boeing 737

When we talk about “INOP” items on a Boeing 737, we refer to the components or systems that are temporarily nonfunctional or disabled due to maintenance, repair, or other reasons. These INOP items are typically addressed by maintenance crews before the aircraft is cleared for flight. Let’s take a closer look at some of the most common INOP items on a Boeing 737.

Electrical Systems

Electrical systems are critical for the operation of a Boeing 737 aircraft. These systems provide power for various functions, including communication, navigation, lighting, and cabin services. In the event of an electrical system failure or an inoperative component, redundant systems or alternate power sources are employed to ensure the continued operation of the aircraft.

One common INOP item related to the electrical systems is the Auxiliary Power Unit (APU). The APU is a small turbine engine located at the rear of the aircraft, which provides electrical power and compressed air when the main engines are not running. If the APU is inoperative, the aircraft can still be powered by the ground electrical supply or the main engines during ground operations.

Another important electrical system on the Boeing 737 is the flight control system. This system includes components such as the autopilot, yaw damper, and flight director. In the event of an INOP item related to the flight control system, the aircraft can still be flown manually using the control columns and rudder pedals.

Hydraulic Systems

The hydraulic systems of a Boeing 737 are responsible for controlling various aircraft operations, such as landing gear extension and retraction, flap movement, and primary flight control actuation. These systems use hydraulic fluid under high pressure to transmit force and movement to different aircraft components.

If a hydraulic system becomes inoperative, specific procedures and limitations must be followed to ensure safe flight. The Boeing 737 is equipped with multiple hydraulic systems (typically three), allowing for redundancy and the ability to function even if one system fails. This redundancy ensures that the aircraft can still be safely operated with an INOP hydraulic system.

Communication and Navigation Systems

Communication and navigation systems are vital for safe and efficient air travel. These systems allow pilots to communicate with Air Traffic Control (ATC) and receive important information regarding weather, traffic, and flight routes. They also provide navigational aids, such as GPS and radio beacons, to ensure accurate positioning and route tracking.

If a communication or navigation system becomes inoperative, pilots have alternative methods to ensure the continuation of their flight. For example, if an aircraft’s primary communication system fails, pilots can use secondary systems or relay messages through other aircraft in the vicinity. Similarly, if a navigation system becomes inoperative, pilots can rely on backup systems or use alternate means, such as visual landmarks or radio navigation aids, to navigate safely.

The Boeing 737 is equipped with redundant communication and navigation systems to minimize the impact of INOP items. This redundancy ensures that pilots have multiple options to maintain communication and navigate safely, even if certain systems are inoperative.


Inoperable systems or components on a Boeing 737 are not uncommon. However, these INOP items are carefully managed and addressed before the aircraft is cleared for flight. The aircraft’s redundancy and backup systems ensure that even if certain components or systems become inoperative, the aircraft can still operate safely and efficiently.

Ultimately, the management and resolution of INOP items on a Boeing 737 rely on the expertise of maintenance crews and the comprehensive procedures and guidelines provided by the aircraft manufacturer. Their diligent efforts ensure that passengers can enjoy a safe and reliable flight experience on board the Boeing 737.

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