Niner Niner: The Importance of Communication

Pilots · 7 min read · Oct 13, 2022
niner niner

Aviation is a heavily regulated industry that has countless procedural and operational standards, a heap of different certifications, and, of course, specific aviation terms and slang. Needless to day, for an aviation outsider, much of the language used between the flight crew in the cockpit and the ATC tower, might sound like complete gibberish.

In this article, we will explain why aviation English is distinct and how it contrasts with the language we use everyday. So, if you want to learn some nifty phrases and understand why they are used by pilots, let’s get started.

Numbers in aviation

Have you ever had the chance to listen to chatter between a pilot and an air traffic controller? If you have, you must have noticed some strange pronunciation of numbers, such as niner niner.

As radio transmissions are often not crystal clear and could be easily confused, pilots spell certain words and numbers to avoid mistakes and misunderstandings during flight communication. This is done because many words in the English language – which is also the official language in aviation – share similar pronunciation, hence it is important to strongly distinguish them to prevent serious incidents and accidents.

So, for example, that’s why four is fower, five becomes fife and nine turns into a niner. It is much easier to understand a word consisting of a couple of different syllables than a single syllable word that can often get cut off by the radio com equipment.

Changing pronunciation is important for reducing confusion. In fact, counting is especially critical in aviation because it deals with information on airspeed, altitude, various flight data, directions and frequencies. It is essential information for the overall flight success.

An aircraft pilot with headset sitting in the cockpit and taxiing behind another airplane.

What what is ICAO phonetic alphabet?

The aviation industry also uses a completely different version of the alphabet to avoid confusion, as it happens every day in phone conversation.

The names of the letters of the English alphabet are “a”, “bee”, “cee”, “dee”, “e”, etc. These can be difficult to distinguish, particularly over a limited-bandwidth and noisy communications channel, hence aviation has been looking for a long time for unambiguous substitute names for use in electrical voice communication such as telephone and radio.

The International Radio-telephony spelling alphabet, also known as NATO phonetic alphabet, uses 26-word codes to name the alphabet letters and numbers. During radio transmissions between the flight crew and the control tower, A is spelled as Alfa, B as Bravo, D as Delta, M as Mike, Z as Zulu.

The code was developed by ICAO (The International Civil Aviation Organization) in 1955 after hundreds of thousands of comprehension tests involving over thirty different nationalities. The pronunciation of some words was a big challenge for non-native English speakers, especially terms with ‘th’, which drastically changed: ‘three’ is pronounced ‘tree’ and one thousand is pronounced ‘one tousand’

A standardized set to spell letters is mandatory to improve and boost the chance of communication success.

Zulu time

The use of the phonetic alphabet has spread past the runway signs and communication at the airport. Very often you will hear that commercial and military pilots also refer to something they call “zulu time”. So, what exactly is it?

Zulu time simply denotes Universal Time Coordinated or UTC for short. UTC or historically also known as Greenwich Mean Time (GMT) is the time zone at Zero Meridian and aviators use this time reference to stay clear of confusing time zone changes while crossing the globe.

But why zulu time? The answer is pretty self explanatory. GMT is measured at Zero Meridian so in the past it has also been referred to as zero time or z-time. However, since the aviation industry has accepted the use of the NATO phonetic alphabet, the term has slowly become “zulu time”.

A private pilot in his aircraft wearing headphones and communicating with ATC.

Aviation English

Aviation English is not only spelling numbers with more syllables or using the phonetic alphabet. Words and terms can profoundly diverge from the language of everyday people. This happens because much of the aviation terminology has to do with operations and maneuvers unfamiliar to non-experts.

The industry trains hobbyist and airline pilots, cabin crew, and aerospace engineers by offering courses in Aviation English with keywords, acronyms, different pronunciations, and other oddities. These studies certificate the proficiency of the trainees, who are involved in learning phonetics and clear pronunciations.

As ICAO states,

the sole object of ICAO language proficiency requirements is aeronautical radiotelephony communications, a specialized subcategory of aviation language corresponding to a limited portion of the language uses of only two aviation professions — controllers and flight crew.

ICAO Document 9835: Manual on the Implementation of Language Proficiency Requirements, Section 3.2.7

If you are a pilot or an air controller, manuals show how to learn the sky language and how to properly deal with communications. They even cover extensively these accidents of the past, in which unclear pronunciation led to fatal mistakes.

Communication failures

According to HighSkyFlying:

Clear communication is crucial when flying to ensure the safety progress and efficient usage of the Radio Frequency.

What happens if a mistake and a misunderstanding arise between two pilots or between a pilot and the air traffic controllers on land? Serious accidents, troubles, and clashes. Let’s take a look at some of them.

The Tenerife accidents

Do you know what happened in Tenerife? In 1977 one of the the deadliest accidents in aviation history was reported: two Boeings 747 collided on the runway, causing the death of 583 people among passengers and crews. The main reason for the crash was a fatal misunderstanding between the control tower and the crew of a KLM flight, which was deploying for a takeoff instead of taxing.

While other reasons could be added such as fog, causing poor visibility, and runaway busier than usual, recordings of the cockpit revealed that the crew and the tower spelled numbers and letters in different ways, which led to a horrendous catastrophe. Before the impact, the cockpit was still arguing if they received the information correctly or not.

Tenerife was the place of another deadly accident in 1980 when a Dan-Air Flight, flying from Manchester, wrongly executed a holding pattern while flying over the forest of Mount Esperanza.

The view of Tenerife and Tenerife airport runway from flight.

The accident was most probably caused by a single misheard word: the aviation controller spelled the word inbound, but the pilot understood outbound.

The control tower instructed the pilot to take a potentially dangerous and unscheduled maneuver over Los Rodeos airport. The flight actually took the opposite direction of the airport without the right altitude to avoid the impact with the mountains.

This misunderstanding doomed all 146 passengers and crew on board the flight.

The Milan accident

On another foggy day, miscommunication played a major role in the collision at Linate Airport in Milan (2001). A business jet was given the command to taxi and to attend for the takeoff. Because the airport had decommissioned their ground radar system and at that point in time didn’t have a new one properly installed, all communication had to be done precisely on voice.

Since the airport’s ATC did not correctly identify the airplane’s location according to the signs present on the taxi routes, the plane misinterpreted the clearance, taxied down the wrong route and subsequently entered the runway which then lead the aircraft to bump a Scandinavian Airlines flight at approximately 170 mph. In total, 118 were killed by the disaster.

The Bogota accident

Another major disaster was the accident that happened in 1990 when an Avianca flight traveled from Bogotà to New York. Due to the bad weather conditions, 33 flights were expected to land on a single runaway. The overworked air traffic controllers did not properly understand that the plane was running out of fuel, hence they instructed the flight to reach an alternative airport within the city limits. As a result, the engine flamed out with the plane slamming into the village of Cove Neck, Long Island.

According to Griffith Law, an American agency specializing in injury cases,

communication failures have contributed to the death of more than 2000 people in plane crashes since the mid-1970s.

The tarmac and parked aircraft at JFK airport in New York.

Radio transmission

The standard method of communication between an air traffic controller and a pilot is voice radio, using either VHF bands for line-of-sight communication or HF bands for long-distance communication. The latter is employed especially for oceanic communication, where VHF stations are not available.

One of the major problems with voice radio communications is that all pilots being handled by a particular controller are tuned to the same frequency. It can lead to an overlap of voices or an overload of the channels and while that does not often cause serious accidents, it can definitely lead to confusion which in turn has to be solved quite quickly.

How to improve flight crews’ communication success

While they were extensively used in the past for every kind of message, today most of the communication happen via written messages thanks to the Controller–pilot data link communications (C-PDLC) system.

The new technology allows pilots and the ground staff (a.k.a. as ATC, Air traffic control) to bypass all the potential disambiguation and confusion, exploiting the same technology of Wi-Fi. All the information is stored as data and sent by the airwaves in the same frequency of voice radio transmissions. Those data are lighter than voice and can travel more effectively without any kind of distortion. When the ATC sends a message, it is displayed on a monitor which enables the pilot to reply very quickly.

It is a greater improvement over the past since the air traffic increase could have led to an overload of VHF bands. Nowadays radio transmission is used only in fewer cases, such as in emergency cases.

Niner niner: A cockpit of a small aircraft and aviation headphones sitting on the panel.

Air traffic controllers are happier

Nowadays air traffic controllers can breathe a sigh of relief. As years of structural misunderstandings, due to language and pronunciation problems, led to air disasters, new technologies can finally offer a broader solution.

It must also be said that, even though radio broadcasting is used less than in the past, the use of English has also greatly improved among non-native speakers. More readily available resources to learn the language, encouragement to learn and past mistakes can all be attributed to better communication standards in aviation.

In fact, some aircraft crashes occurred precisely because the control tower and crew members had difficulty with English pronunciation. However, today the situation seems to be greatly improved.

Closing thoughts

Most of us will readily agree that clear communication is key in virtually all situations of our lives. In aviation concise and coherent transmission of data is of utmost importance as it serves the purpose of overall safety of passengers, crew and ground staff.

While cockpit and ATC communication has come a long way since people first started flying, there is still room for improvement and aircraft manufacturers as well as ground control keep working hand in hand to implement new tools and equipment for smoother data transmission.

Of course, since pilots and air traffic controllers are also human, they are bound to make errors, we will probably never reach flawless communication in aviation, however nowadays we have various other instruments on board to help the aviators make sometimes life-saving decisions when traditional voice com fails. So, fear not, aviation is still the safest way to travel.

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Jet pilot @NASA

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