Do aircrafts have horns?

Do aircraft have horns?

In a machine which has evolved over time to be as sophisticated as the modern day aircraft, you’d expect there not to be annoying horns like the ones that exist on its ground cousins. (no disrespect to cars but it had to be said). But they do exist.

Why? Why do they exist? – a sincere question from a concerned migraine

For one, It’s to communicate to the ground crew. An alert like a horn could get them to put on their headset.
Also, an aircraft is pretty big. It can be as long as 60 m which are 60 adult human legs put together.

 F-16 looking fly 

The cockpit needs to communicate the essential information received from the various parts of the airplane. Contrary to popular belief, it can’t be achieved by having monitoring minions in the engine yelling THE PLANE’S GOING DOWN. That’s not going to sit well with the anxious aunty who brought her own snacks in the economy cabin. So a series of sensors are set up at various critical parts of the aircraft and they transmit information via cables to light and sound signals on a panel in the cockpit called the master annunciator panel.

 master annunciator panel 
This panel has a set of lights – red, amber and blue. When a system has a fault, depending on the magnitude of the problem, the appropriate lights illuminate.

Red- Caution, needs immediate action (YOU.)

Amber- Warning, needs crew’s immediate awareness

Blue- advisory, to let crew know that something is working as it is supposed to

But it’s not just visual cues, the (CAS) crew alerting system sets up auditory and tactile cues as well just for good measure. Hold up, what cues?

Auditory cues or in simpleton's tongue: Horns. And Other stuff.
"Delta four five one, winds two eight zero at eleven, cleared for takeoff." Young pilot grant just having been given permission, takes off from JFK and heads east towards Heathrow. After cruising at 14,000 ft, he climbs to 15,000 ft and is given a single chime of validation. Grant sighs taking in a deep breath. Working on little sleep and overwhelmed with exhaustion he switches over to autopilot. Maybe a little shuteye? PULL UP! PULL UP! Woken with a jolt, he gains control of his senses enough to know that Delta 451 was fast descending to a nearing hill. Just as he begins taking action, CLIMB! CLIMB! As if a series of unfortunate events were to follow, a timed beep beep beep beep and a series of horns successively bombard his auditory cortex. Hanging on to the single thread which holds his sanity, Grant realizes he can’t do it alone. As the co-pilot, you need to step up to the occasion (considering you were watching in awe as almost every system was gloriously failing before your eyes). But how can you help, if you don’t know what the sounds stand for?
TCAS and GPWS- voice warnings like pull up! Climb! For traffic or impending collision, or warning the closeness to ground.

goddammit grant, you had one job

 (Cool fact: TCAS and GPWS have been nicknamed bitching betty and the first ever voice to be digitized for this system was Kim Crow)

Pressurization: A continuous horn is noised when there are cabin pressure issues.

Configuration: A horn at intervals or a beeping sound when the control surfaces like flaps, slats, stabilizer trim, or speed brakes are not properly configured before takeoff.

Landing gear: A horn sounds and appropriate gear position indicator lights illuminate when an unsafe gear configuration exists.

Altitude: A single chime, along with a visual cue, alerts pilots when they are leaving the current altitude or approaching a new one.

Autopilot disconnect: Various kinds of siren, klaxon, or chime sounds, accompanied by red warning lights, signal that the autopilot has disconnected.

Engine or APU fire: FARs require that engine and APU fires be indicated by a bell accompanied by red fire warning lights.

Overspeed: An over speed "clacker" sounds when a limiting mach or airspeed is exceeded.
There you have it. No time to waste, young pilot grant needs you. Godspeed.

Thanks for reading!

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