Summary

• Airliners have horns similar to cars but sound more like an alarm than a traditional horn.
• Pilots rarely use the horns, but ground crews use them to get attention during maintenance.
• The horn is not used in flight, but modern planes have other signals to warn of system failures.

While many have never heard an airliner's horn, they indeed do exist. However, they are nothing like cars' horns, as they cannot be used to instruct other aircraft to get out of the way.

The Boeing 737 is well-known to have a horn switch on the overhead panels in the cockpit, and pilots can use it to generate a loud sound. Primarily, this is used to alert maintenance crews of certain situations and can also serve some other purposes. In this article, we will take a deeper look at aircraft horns and their roles.

Beep beep

The first thing one should know about aircraft horns is that they sound nothing like a traditional car horn. Instead, a horn sounds significantly closer to a car alarm. In 2019, Royal Dutch Airlines (KLM) released a video demonstrating the bizarre sound of a car horn, which can be seen below:

Furthermore, all airplanes have a ground call button performing the same role as the horn. This small switch is located on the overhead panel and is placed right next to the switch pilots use to contact cabin attendants.

How are airliners' horns used?

The tiny switch on the overhead panel says "GRD CALL" or "GND." It depends on the aircraft model. As explained by KLM, the pilots use the switch only when they seek the attention of someone on the platform. They do not use it to call someone from the cabin crew because, most likely, they will not hear it at all or would not know what to do, according to a pilot on Quora.

Aircraft horns are used only during specific emergencies, and pilots are not the ones who use the horns the most. Instead, ground crews use the switch the most when performing maintenance in the cockpit, as it is how they seek the attention of their colleagues on the ground. In a statement, KLM described the horn's purpose as follows:

"Whereas horns in cars are mainly used as a warning system, the horn aboard an aircraft is primarily a form of functional technology, which is indispensable when the aircraft is undergoing maintenance in the hangar."

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How are airliners' horns not used?

Pilots seldom use horns because they do not need to do so. Moreover, as posted by some pilots, if they try to use the horns while preparing for departure, they most likely would not be heard over the noise of the aircraft itself and the airport activities surrounding it. The horn system also cannot be used in flight as it is turned off automatically after takeoff.

So, while the horn is primarily a means of communication, it is not the only way the aircraft can send a signal warning of failure. Modern airliners are equipped with several systems to ensure proper communication in the event of a safety-critical event.

Aircraft can also emit a signal that sounds like a siren to warn engineers when a system breaks down, or there is a fire or another kind of failure. Moreover, signals vary so that engineers and mechanics know exactly which system is under threat.

Did you know airliners have horns? Do you know of any other use for them than the ones described here? Let us know in the comments below.