Why Do Pilots Say Niner?(How Pilots Count to ten)

In aviation, clear communication is essential to ensure the safe progress of flights, and efficient use of radio frequencies. As aviation English is the accepted standard throughout most of the world, it means the vast majority of pilots, air traffic controllers, and others involved in the industry, are speaking in a second language. To help eliminate confusion, some numbers are pronounced differently, and some words are avoided altogether.

So, why do pilots say niner?

Pilots and air traffic controllers say niner instead of nine to distinguish it from other numbers. Radio transmissions may not be crystal clear, and with any disturbances on the frequency, nine could be easily confused with five, given they are one-syllable and rhyme. Niner, however, cannot be confused with any other number.

Also, there was concern that the number nine may be confused with the german word for no, “nein”, and this helps to avoid that.

It would be easy to stop the discussion here, but Aviation English is full of examples of strange pronunciations and oddities. The phonetic alphabet, certain keywords, and phrases are all part of what needs to be learnt when becoming involved in the aviation industry.

How do pilots count to ten and beyond?

Aviation English is a key component of minimizing misunderstandings, and we touched on the topic of why much of the phraseology in aviation is done in English in this article.

Let’s discuss numbers, seeing as that is how we started this topic. Numbers are essential for communication and aviation, ranging from altitudes and flight levels, velocities, headings, frequencies and runway directions, weather-related information, etc. The list goes on and on!

This is normally vital information and an error can lead to catastrophic consequences (for example a pilot may climb or descends to an incorrect level).

Below is a list of how pilots and air traffic controllers pronounce the numbers zero to ten:

0 – zero

1 – one/won

2 – two

3 – tree

4 – fower

5 – fife

6 – six

7 – se-ven

8 – eight

9 – niner

10 – one zero

Most numbers are pronounced more or less as you would expect, but there are four, maybe five, big exceptions. The numbers 4 and 7 are the least changed in terms or pronunciation, with just a slight emphasis on the end of the words.

The number 9 is the most changed, and the similarly-pronounced 5 is changed as well. 9 is given an extra syllable, NINE-ER, and 5 is pronounced FIFE, in a short and abrupt way. 

3 is pronounced TREE, to limit confusion with 2. It might seem a little odd that two seemingly so similar numbers are confused, but that’s actually true! Really?

It is amazing how often, in my time as an air traffic controller, pilots and ATCOs will confuse a three with a two and vice-versa, even when pronouncing the words correctly. Two and three is by far the most confused pair of numbers in my 14 years of experience and you would not expect that to be the case. It is especially bad with radio frequencies that contain 2s and 3s, and flight levels like 230, 320, and 330. On a daily basis, the correct frequency and level need to be clarified.

Is clear pronunciation really so important?

The above serves to highlight how important clear and easily understood communication is, even between native speakers. And what most people don’t take into account, is that most pilots and ATC, when speaking English, are not speaking their native language, which makes misunderstandings even more likely!

Numbers that are fully understood only makes communicating between pilots and ATC, and thus flying, safer. It is also why numbers beyond ten are broken up into their individual single digits, like one-zero for 10, two-eight for 28, and so on. 

During the day-to-day business of communicating between pilots and ATCOs, shortcuts may be taken (“United 23 leaving two eighty-eight and on climb Flight Level three-one-oh”) and I have to be honest when I say this is not the highest level of radio professionalism, and it happens all too often. In this example, the correct phraseology would be “United 23 passing Flight Level two-eight-eight on climb Flight Level tree-one-zero”).

It is worth noting that from 1,000-onwards, the phraseology counts in lots of one-thousand, so for altitude the correct way to say 2,800FT is two-thousand eight-hundred feet, not two eight zero zero feet. 

How are misunderstandings reduced?

Most aviation communication is done via Very-high frequency (VHF) radio, because it is clear and relatively static-free.

However, VHF is line-of-sight so the range is normally restricted to about 200 nautical miles. This isn’t a problem over land because several radio antenna ground stations can be installed and used, and pilots are instructed to change to the appropriate frequency during flight.

Beyond VHF range, High Frequency (HF) radio is used, but its poor clarity makes it a laborious and difficult medium to use for communication in busy environments, and is normally used by ATC in oceanic sectors where VHF ground stations can’t be installed.

However, specially-trained HF operators are often used as a third-party between pilots and ATC to pass on clearances and requests, and their training and experience reduce wasted time and misunderstandings. I can tell you with little doubt that it is a highly-specialized skill to be an HF operator, requiring a great deal of patience and an attuned ear to master its use.

Controller-Pilot Data Link Communication (C-PDLC) is, by aviation standards, a relatively new technology that allows ATC and pilots to send written messages, eliminating almost all potential for confusion. It is almost like sending an SMS, and takes seconds.

More and more aircraft are equipped with C-PDLC and, speaking from experience, it has helped streamline communication with flight crews and allows for much greater efficiency; ATC can send multiple C-PDLC messages at once to several aircraft, and use the relevant radio frequency to transmit more complex instructions if and when necessary. C-PDLC will never eliminate radio communication, but it is an exceptional tool to have available for use.

What can happen if misunderstandings are not recognised?

One of the most-often referred-to incidents concerning a misunderstanding occurred at Tenerife North Airport (then known as Los Rodeos Airport) on 27 March, 1977. It is still the deadliest aviation incident we have ever seen.

Two Boeing 747s (KLM 4805 and Pan Am 1736) collided on the runway resulting in the deaths of 583 people, as a result of a misunderstanding by the flight crew of KLM 4805’s departure clearance from the air traffic controller.

While there were a number of other circumstances (fog causing poor visibility, busier than normal traffic conditions, aircrew fatigue, and time pressures, the lack of ground radar, and radio frequency congestion) that contributed to the incident, ultimately it was a pilot’s incorrect understanding of a non-existent takeoff clearance that was the major cause of KLM 4805 executing a takeoff while Pan Am 1736 was still taxiing on the active runway.

The following is the transmission from the air traffic controller (ATCO) to KLM 4805;

“KLM 8705 [sic] uh you are cleared to the Papa beacon. Climb to and maintain Flight Level 90 … right turn after takeoff proceed with heading 040 until intercepting the 325 radial from Las Palmas VOR.”

The incorrect call sign was just a mistake, but highlighted here is the word takeoff which led to the massive misunderstanding from the KLM flight crew.

The flight crew made a read back of the clearance, of sorts;

“Ah, roger, sir, we’re cleared to the Papa beacon Flight Level 90, right turn out 040 until intercepting the 325, and we’re now (at takeoff).”

The ATCO replied with an “Okay’, which suggests he didn’t fully comprehend that KLM 4805 was commencing the takeoff roll, and all the while Pan AM 1736 was still taxiing on the runway. However, the ATCO did follow up with another transmission directed to KLM 4805, which must have been missed by the KLM 4805 flight crew;

“Stand by for takeoff … I will call you.”

The Pan Am flight crew then also made a transmission;

“And we are still taxiing down the runway, the Clipper (Pan Am) 1736.”

And about 15 seconds later KLM 4805 collided with Pan Am 1736, as each flight crew made visual contact with each other through the fog far too late to take avoiding action.

What can we learn from incidents as a result of misunderstandings?

No safety system is perfect, and procedures, regulations, and training practices are constantly being refined, improved on, and added to, to reduce and eliminate the possibility of aviation incidents.

Vigilance, attention to detail, standardisation, and experience are key to ensuring the contoured safe and expeditious flow of air traffic.

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