Topic Category: AVI30419

Much of the material presented in this session is taken from the CASA publication shown.

The single biggest problem in communication is the illusion that it has taken place.

George Bernard Shaw

Each one of us is the sum total of our past life. We rationalise, analyse and interpret information through our own unique frame of reference.
What we perceive we have communicated may not be how the recipient perceives the same information – after all, two different frames of reference have been used.

Consider that:-

• WE write something down for someone to read.
• WE say something for someone to hear. George Bernard Shaw
• WE therefore have an obligation to communicate that information in such a way as to minimise the possibility of it being misunderstood!

Communication is a two-way process. A more thorough understanding of how English is used will enable more effective communication with both native and non-native English-speakers.

With a greater awareness of English, you will be better able to avoid communication problems or to rectify them quickly.

It is not sufficient for you, the Level 6 Expert Speaker, to argue that the other person had such a poor command of the language that the accident, incident or misunderstanding was not your responsibility.

This presentation is about raising your linguistic awareness.

ICAO has specified six criteria for assessing the level of language proficiency. These are:

• pronunciation
• structure
• vocabulary
• fluency
• comprehension
• interactions

ICAO requires that an Expert Speaker performs very well in all of these criteria.

Someone with a speech defect, which hinders their ability to say certain sounds or groups of sounds, does not meet the requirements for Level 6 Expert Speaker, nor does someone who performs poorly in any one of the criteria.

Australian English has three main varieties, each of which has its own accent and, to some extent, its own vocabulary:

• General Australian English. This is the most common in polite conversation. Most news readers, TV announcers and media personnel speak this variety.
• Broad Australian. This is the language typified by Crocodile Dundee and other Australian characters in movies. Sometimes referred to as ‘Strine’ (from the word ‘Australian’ spoken in this accent).
• Cultivated Australian. It is spoken by comparatively few Australians. It resembles a variety used in southern England and known to linguists as Received Pronunciation. To our ears, it sounds the most like British English.

The three varieties of Australian English are not linked to regions or to social backgrounds. All three varieties are used in the cities and the bush, and often by the same person at different times.

The Table below, which summarises the pronunciation skills of a Level 6 Expert Speaker.

Among all varieties of English, including the three varieties of Australian English, there is much more variation in the pronunciation of the vowel sounds (a, e, i, o, u) than there is between consonants (b, d, f, m, s, etc).

Our brains do a wonderful job filling in gaps and obtaining meaning, even when individual sounds may have been pronounced less than perfectly.

While our brains are good at filling in many gaps, they cannot always do so. A speaker who makes numerous mistakes in pronouncing consonants and clusters of consonants is more difficult to understand than one who confuses the length of a pair of vowels, such as in ship/sheep. This is because more information is conveyed by English consonants than by the vowels.

Consider the following exercise:-

The following two aviation-related expressions might be found in an airport. Letters missing – Can you fill in the gaps?

(There is a ‘/’ between each of the words in the two expressions.)
-st-m-t-d/ t-m-/ -f/ d-p-rt-r-
–i—/ i–o–a-io-

• Both expressions have 11 letters missing!
• The first expression is ‘estimated time of departure’.
• This sentence lacks vowels
• The second expression is ‘flight information’.
• This sentence lacks consonants.

Although these examples use written English, the same applies to spoken English: namely, consonants provide more information than vowels.

Say the following two sentences to yourself, paying attention the way in which you said the underlined word in each sentence.

• CASA kept a record of the incident.
• CASA will record the incident.

What was the difference in your pronunciation of the two underlined words?
In the first sentence, did you pronounce the word record like this: REcord (with the first syllable receiving the most emphasis or stress)?
In the second sentence, did you pronounce the word like this: reCORD (with the stress on the second syllable)?

Changing the stressed word in a sentence can totally change the meaning of the sentence. Consider the simple sentence – ‘I didn’t say I was born in Sydney’.

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

I didn’t say I was born in Sydney

……so what exactly does this sentence actually mean? What are you trying to communicate? How could you WRITE this to convey the meaning you intended?

Native speakers of English know which syllables to stress for their variety of the language, but this feature of English is difficult for speakers of other languages.

For example, Japanese speakers of English find English stress patterns difficult. The Japanese language gives each syllable similar emphasis. Just think of the pronunciation of the Japanese city, Osaka:

O-SA-KA

Many English speakers mispronounce the name of this city by trying to stress one of its three syllables, such as by incorrectly saying:

o-SA-ka

Japanese language does not stress individual syllables in the way English does.

In addition to emphasising some syllables, all speakers of English ‘swallow’ other syllables. These ‘swallowed’ syllables are unstressed syllables. They are usually shorter and softer than stressed syllables, and so are more difficult to hear.

The use of standard phraseologies means there is less opportunity for swallowed syllables in your radiotelephony communications, unless you are using ordinary, General English (including General Australian English).

Swallowed syllables are not a problem when one Level 6 Expert Speaker communicates with another, as both can fill in the blanks. However, they may be a problem for non-native speakers of English.

Part of the message may not be heard and, therefore, either not understood, or misunderstood.

Speakers of English not only stress certain syllables, but also squash up unstressed syllables so they maintain a rhythm.

QUIETLY say and listen to the rhythm of these two familiar expressions:

• a) Ham and eggs
• b) Bacon and eggs

Using your pencil or pen, gently tap out the rhythm, giving a tap for each stressed syllable. You should notice that the interval between the two stressed syllables is the same. It takes just as long to say the three syllables in expression a) as it does to say the four syllables in expression b).

In English, the rhythm of the language is influenced by the stressed syllables.

• The shorter, unstressed syllables are pushed together to maintain a regular interval between the beat of the stressed syllables.
• The greater the number of unstressed syllables in the interval between the stressed ones, the more the unstressed ones are swallowed or reduced.

This way of speaking (this rhythm) is very different from the rhythm of languages which give each syllable equal stress. Such languages tend to sound to our ears like a steady rat-tat-tat-tat-tat-tat.

In addition to stress and rhythm, English speakers use variations in the level of their voice (or intonation) to show meaning.

Consider the following sentences:

• The co-pilot flew the plane. (Said as a statement)
• The co-pilot flew the plane? (Asked as a Question)

Say both sentences, listening to the change in the level of your voice as you contrast the statement with the question.

In the statement, the tone of your voice, or its level, generally drops towards the end, while in the question the voice tends to rise, or move to a slightly higher level.

In the following two expressions, we know that the first is grammatically correct, while the second is not:

Does he like flying?

Likes he flying?

Although the expression ‘Likes he flying?’ is incorrect, we can still understand it. Errors such as these are what linguists call local errors.

Local errors do not prevent comprehension.

Global errors are more serious because they interfere with meaning.

Consider the following example! (This is a global error):

The pilot was decided to land the plane.

We cannot tell from this sentence whether the pilot decided to land the plane or whether someone else told the pilot he had to land the plane.

Recognising global errors is an important skill; dealing with them promptly could be life-saving.

• How should you deal with global errors in RTC?
• Asking the other person to read back, or say again, is not necessarily going to solve the problem.

The most appropriate technique is to rephrase the message yourself and obtain confirmation that this is what was meant.

In the following, determine the errors and decide whether they are local (L) or global (G):

1. ‘After departure crimbe fife tousand’
2. ‘Fastair tree fower fife reduce spee now too wun zero knots.’
3. ‘Since monsoon was heavy, lot of flight delayed.’
4. ‘Air transport use much people’

Answers:

1. Local. crimbe = climb
2. Local. spee = speed
3. Global. We cannot tell whether this means ‘Lots of flights were delayed after the heavy monsoon’ or ‘Because the monsoon was heavy, a lot of flights were delayed’. There is also a local error in this sentence: lot of flight = either lots of flights or a lot of flights.
4. Global. We do not know whether this means Air transport employs ‘a lot of people’ or ‘A lot of people travel by air’. There’s also confusion with much/many, but this does not prevent comprehension, so it is a local error.

An aspect of language that is correct in a person’s first language but which is transferred to their second language and used there incorrectly is known as a ‘fossilised error.

For example, Italian has double consonants both of which are pronounced. The Italian word, casa means house; the Italian word cassa means cash desk or cash box. In Italian it is important to distinguish between the single s and the double ss in these two words, because the meaning is different.

English does not have such contrasts. We do not pronounce the sound ‘s’ twice in the word fossil, for example: we say ‘fosil’. But a speaker of Italian may pronounce that English word according to the rules of Italian and say, ‘’fos-sil’.

It is very difficult to totally replace the sound system of one’s first language with those of the second language.

Those elements of the first language which are incorrectly transferred to the second language and remain there are called fossils.

If they do not prevent understanding, they are treated as local errors.

As a Level 6 Expert Speaker, you should be able to use not only simple sentences but also compound and complex ones.

Simple sentence:  ‘I can’t extend the landing gear.’

Compound sentence:  ‘I can’t extend the landing gear and I’m nearly out of fuel.

Complex sentence:  ‘If I do a go round, would you visually check my landing gear?’

By definition, compound and complex sentences have more than one verb. They can be thought of as two or more simple sentences combined.

Compound sentences use ‘and’ or ‘but’ to combine two or more simple sentences. In the following examples, the verbs are underlined:

He flew to Brisbane and she drove to Sydney.

She flew to Paris but I stayed at home.

Compound sentences are not usually difficult for non-native speakers to say or understand, as virtually all modern languages use them.

Complex sentences (as their name implies) are often difficult, both to produce and understand. Non-native speakers of English with a limited command of the language may find them confusing.

In non-routine situations, you would be wise to avoid certain types of complex sentences.

Consider the following complex sentences – and how they may be misunderstood. (Note the comma separating the two parts (or clauses) of each sentence.)

Sentence A: If it had rained heavily, we would have diverted.

Sentence B: If it had rained heavily, we wouldn’t have landed there.

Sentence C: If it hadn’t rained heavily, we would have landed there.

Sentence D: If it hadn’t rained heavily, we wouldn’t have diverted.

Consider these sentences again in a grid to show their parts, and also to consider how many ‘not’ or ‘n’t’ words they contain.

(These ‘not/n’t’ words are called negative words in the table.)

Sentence A has no negative words in it, such as not or n’t;   but its meaning includes two negatives.

Sentence A: 

If it had rained heavily, we would have diverted.

What sentence A means:

It didn’t rain heavily, so we didn’t divert.

This sentence contains two pluses – meaning two negatives. Both parts, or clauses in this sentence are affirmative, but the meaning is the opposite.

Sentence B: 

If it had rained heavily, we wouldn’t have landed there.

The first part of this sentence has no negative words, and means:

‘It did not rain heavily.’

The second part of the sentence has a negative word, ‘we wouldn’t have landed there,’ and it means:

 ‘we did land there’

 …….therefore:

‘If it had rained heavily, we wouldn’t have landed there’

really means

It didn’t rain heavily, so we did land there.

or:

It didn’t rain heavily, so we landed there.

Negative questions are best avoided in RTC because the answer may be ambiguous.

Consider the following question and answer:

Aren’t you flying to Adelaide tomorrow?

Answer:

Yes

In Australian English the ‘yes’ means ‘Yes, l am’; but in many varieties it means ‘Yes, I’m not’.

Remember the ICAO Manual states: be clear, concise and direct!

In linguistics ‘register’ has several meanings, but the one we will use here relates to informal/formal language.

For example, when greeting friends or colleagues of similar status we might say:

‘G’day’, or ‘Hi, how’s things?’

  These are very informal greetings, commonly used by Australians.

  However, when greeting a stranger or a superior, we might say:

  ‘Good morning, how are you?’, or ‘Good morning, sir’.

Both of these are more formal than the greetings for our friends and colleagues.

Not only is the grammar different, so too is the vocabulary – which is called lexical choice.

Many cultures emphasise formality, and speakers from those cultures may seem to us to be ‘stiff‘ in their interactions. Alternatively, in their attempt to master Australian English, they may come across as too personal or even rude.

From the perspective of those whose cultures value formality, Australians may appear far too casual.

When we interact aeronautically, the best approach is to maintain a friendly but somewhat formal register. If someone inappropriately calls you ‘Sir’ or ‘Madam’ or inappropriately greets you with ‘G’day’, treat it as a minor matter.

Vocabulary which is nuanced has delicate shades of difference. (A variation in tone or meaning is called a nuance.)

Consider the following reply to a manager’s email summarizing a performance review in which the employee was advised his work was less than satisfactory and required improvement:

I do not agree with the remarks in your email. I find them very inappropriate. I do not believe you have reason to accuse me of unsatisfactory performance. I have never received negative feedback in my previous jobs. If you do not take back your comments, I plan to take this to a higher level.

The use of words like “do not”, “very inappropriate”, “accuse”, “never”, “negative”, and the short, clipped sentences – and a threat – the employee is sending a message that has a very confrontational attitude.

What kind of reaction from the manager might this message produce?

Most managers are aware that they need to provide “constructive criticism”, not outright condemnation, of an employee’s performance. Most managers will use indirect language in their written and spoken assessments.

 Had the individual softened his tone by beginning with a neutral opening statement like, I have read your summary in regard to my performance evaluation, and “I have to say that your comments caught me by surprise,” he would have left a very different impression.

In this way, his message would have matched that of his manager’s in terms of attitude.

While a Level 6 Expert Speaker is able to convey subtle differences of meaning, in your RTC interactions you need to state clearly what you require, and you need to respond clearly.

The use of indirect language and subtle messages can cause confusion and require “reading between the lines” to interpret the intended message – before an appropriate response can be formulated.

Before writing and sending any kind of business communication, make a conscious decision about what tone you want to deliver based on the purpose, audience and desired outcome.

The RTC environment is no place for subtle differences in meaning. These can lead to misunderstandings and safety hazards. Stick to being clear. If in doubt, seek clarification.

Although fluency is a difficult concept to define, most speakers have an ‘intuitive’ sense of what it is.

As radiotelephony communications take place in a busy environment, the communications of air traffic controllers and pilots must not only be clear, concise and unambiguous, but responses must be delivered efficiently and a rapid response time is expected.

For our purposes, “fluency“ is intended to refer to the ‘naturalness’ of speech production – the degree to which comprehension is impeded by any unnatural or unusual hesitancy, distracting starts and stops , distracting fillers (em…huh…er…) or inappropriate silence.

Discourse markers and connectors are words which help the listener to follow the flow of a conversation. Consider the following:

Speaker A: What would you do if shortly after take-off your colleague in the cockpit appeared to have fainted?

Speaker B: First, I would speak to him to try to confirm that he has actually fainted – and then I would….

The underlined words (or discourse markers and connectors) help the listener follow the flow of the message.

As an Expert Speaker fluency will not be a problem because you do not have to search for every word, nor worry about stress, rhythm, intonation and so on. You can produce speech with a natural flow’.

However, your natural speed of speech may be fast and so may be difficult for non-native speakers of English to understand.

We can help communication by speaking clearly and avoiding slang and colloquial expressions.

It is useful to remember that, in some cultures, loss of face is an important issue. Loss of face roughly means embarrassment, humiliation or a loss of self-esteem.

A loud, impatient tone of voice, when speaking to Vietnamese and Chinese speakers, for example, may contribute to a loss of face.

In many cultures senior, or older, people do not like to ask for information or help, particularly when they are expected to have that information or skill already.

Similarly, in some cultures, people try to avoid giving a direct refusal because this means the person who is asking could suffer a loss of face.

Verbal cues include behaviour such as speaking louder, putting more emphasis on certain words, or saying something twice, as in the ‘words twice’ request.

Inappropriate interactions may indicate a message has not been understood, as in the following exchange:

Speaker A:  Can you tell me where you learned to fly?

Speaker B:   In 1993.

Non-verbal cues include facial expressions for example a frown, a smile or a puzzled look. These cues also include gestures and body language (a shrug of the shoulders, a shake or nod of the head, or movement of the hands). Inappropriate periods of silence may also be non-verbal cues; it is the only non-verbal cue between control and pilot after the aircraft is flying. Non-verbal cues also relate to communications between the flight crew, within the cockpit.

‘Fuel Lines’ Recording

When a message is not understood, it can be a waste of time repeating it at a louder volume, because this can alter the stress and rhythm and create different problems.

It is better to use short, common words. In other words, rephrase the message in a controlled way:

Pilot:  A.B.C. My FUEL-lines are FREEZing up.

Control:  A.B.C. SAY aGAIN

Pilot:  A.B.C. My FUEL is FREEZing. I MUST desCEND to FLIGHT LEVel TWO FIFE ZERO

Control:   A.B.C. aFFIRM desCENT to FLIGHT LEVel TWO FIFE ZERO.

Law set out by Civil Aviation Regulation 83 prohibits a person from transmitting on a radio frequency unless qualified to do so

• 50pu (Fine $10500)
• This prevents interference or over transmission of critical safety related transmissions

Hence you receive training and an AROC to qualify you

CASR 64.B Transmission on aeronautical radio frequencies

Eligible for AROC if:

• At least 17 years
• Received training and assessed (Part 61)
• Aviation English Language Proficient Assessment

While American, the following video is a good introduction to radio use.

In Australia the registrations all start with VH- followed by three letters. While flying within Australia the VH gets dropped and only the three remaining letters are used as the callsign.

Air Traffic Control:

• To operate within Controlled Airspace with approval
• e.g. above 400ft or within 5.5km of a controlled aerodrome
• Callsign: (Brisbane) Tower; (Brisbane) Approach; (Brisbane) Ground

Pilots of Manned Aircraft:

• Helicopters
• Ag planes
• Aircraft outside controlled airspace near aerodromes
• Callsign: In Australia registered callsign e.g. Foxtrot India November or Qantas 5 3 6.

Ground support crew on discrete frequency

• E.g. Car 23

RPAS operations will predominantly be VHF frequencies.

Frequencies are displayed on Aeronautical Charts and in AIP (Aeronatical Informantion Publication) publications such as ERSA (En Route Supplement Australia).

VTC (Visual Terminal Chart) chart which includes topographical information, airspace limits and frequency information

ERSA is a list of Aerodromes, with operating information.

HF frequencies vary depending on atmospheric conditions. Usually, a 4 numbered KHz frequency e.g. 6610 See location briefing

When you are online gaming, what happens when you all get excited and start speaking at the same time? Do you understand what has been said all the time?

Is it effective? Would this be safe flying around the sky?

Would it be appropriate to say…

Hello Brisbane Tower I’m the aircraft turning onto final approach path to runway 19 Right, who will be requesting permission to land. Awaiting your response…

Or could this be said more succinctly?

Brisbane Tower, Alpha Bravo Charlie, Final 19 Right, Request landing clearance.

The primary purpose is:

• Reduce the possibility of a misunderstanding
• Reduce the number of words spoken
• Reduce the time on the radio

Here’s a start with some common types of phrases:

• Affirm: YES (was once Affirmative, but with a clipped transmission there was confusion between affirmative and negative)
• Negative: NO
• Roger: I have received all of your last transmission
• Wilco: Understand all of your message and will comply with it
• Maintain: Continue in accordance with the procedures specified or in its literal sense (e.g. maintain VFR or 300ft)
• Correction: An error has been made in this transmission. The correct version is…
• Standby: Wait and I will call you
• Acknowledge: Let me know that you have received and understood the message
• Cleared: Authorised to proceed under the conditions specified

Remember communication and its how you say it that counts. Please note ‘over’ and ‘out’ rarely if ever used with VHF (used for UHF/ CB).

For further information, check the following link:

Try to match the correct word for the following examples:

ATC: Alpha Bravo Charlie _____ to Take off.

• Acknowledge
• Maintain
• Cleared
• Affirm

Pilot: ______ 1000 feet, Alpha Bravo Charlie

• Acknowledge
• Maintain
• Cleared
• Affirm

ATC: Alpha Bravo Charlie, Confirm receipt of information Delta.

Pilot: _______ with Delta, Alpha Bravo Charlie

• Acknowledge
• Maintain
• Cleared
• Affirm

Remembering them All!

Try to match the correct word for the following examples:

Callsign “VH-HYZ”:

• Hotel Yahtzee Zero
• Hospital Yellow Zulu
• Hotel Yankee Zulu
• Hospital Yankee Zorro

Callsign “VH-XFB”:

• X-ray Fantail Bureau
• X-ray Foxtrot Bravo
• X-ray Footsie Bravo
• X-ray Foxtrap Bongo

Australia uses Coordinated Universal Time (UTC) for all civil aviation operations (AIP GEN 2.1).

The term ‘Zulu’ is used when ATC procedures require a reference to UTC, for example: 0920 UTC is said as ‘zero nine two zero zulu’ 

The 24-hour clock system is used in radiotelephone transmissions. Time may be stated in minutes only (two figures) in radiotelephone communications when no misunderstanding is likely to occur. 

Date and time are indicated in a combination of the date and time in a single six- figure group. However, a 10-figure group comprising the year, month, date, hours and minutes is used for NOTAMs and SUPs.

Try to match the correct word for the following examples:

ATC: Foxtrot India November, Required to hold at Boree, set course 0721 zulu

• Zero seven too one zulu
• Seven twenty one zulu
• Seven hundred twenty one zulu
• Zero seven two oner zulu

Clearances:

• Controlled Airspace
• Class C & D

Broadcasts:

• Outside Controlled Airspace
• Common Traffic Advisory Frequency (CTAF)
• Class G

Note: A Broadcast may start with either:

• [Location] Traffic – this refers to aircraft only
• All Stations [Location] – refers to aircraft and Air Traffic Services, UNICOM and vehicles on the ground.

Example Broadcast

• Listen Before you Transmit:
  • If you have just changed frequencies, pause, listen, and make sure the frequency is clear
  • Don’t broadcast until you know the frequency is clear or you will jam, or “step on” another call causing them to repeat their call
  • Keying a transmitter when someone is talking will be futile and you will probably jam their receivers causing them to repeat their call
  • Many times you can get the information you want through Automatic Terminal Information Service (ATIS), Aerodrome Weather Information Service (AWIS), or by monitoring the frequency
• Think Before Keying the Transmitter:
  • Know what you’re going to say before you say it
  • If it is lengthy; e.g., a flight plan or IFR position report, jot it down ahead of your call
• Key the Mic and Talk:
  • The microphone should be very close to your lips, but not touching, and after pressing the mike button, a slight pause may be necessary
  • Constant volume and even rate of speech (not exceeding 100 words per minute)
  • Be clear, concise, accurate, speaking in a normal tone
  • When you release the button, wait a few seconds before calling again as the controller or FSS specialist may be jotting down your number, looking for your flight plan, transmitting on a different frequency, or selecting the transmitter for your frequency

Transmission Tips:

• Use a normal conversation tone, speak clearly and distinctly
• Maintain an even rate of speech not exceeding 100 words per minute. When it is known that elements of the message will be written down by the recipients, speak at a slightly slower rate.
• Maintain the speaking volume at a constant level.
• A slight pause before and after numbers will assist in making them easier to understand.
• Avoid using hesitation sounds such as ‘er’
• Avoid excessive use of courtesies and entering into non-operational conversations.
• Depress the transmit switch fully before speaking and do not release it until the message is complete. This will ensure that the entire message is transmitted. However, do not depress transmit switch until ready to speak.
• Messages should not contain more than three specific phrases, comprising a clearance, instruction or pertinent information. In cases of doubt, e.g. a foreign pilot having difficulty with the English language or an inexperienced pilot unsure of the procedures, the controller should reduce the number of items and if necessary these should be passed, and acknowledged, singly

Which Frequencies will you hear this on?

• ATC frequencies
• Area frequencies
• CTAF frequencies
• International Guard Frequency 121.5
  • Distress Beacon alert
  • Emergency Calls
  • DO NOT TRANSMIT ON THIS FREQUENCY

You can listen now at: https://www.liveatc.net/

Search e.g. YBAF (Archerfield), YBBN (Brisbane) Ground, Tower…

Light Signals:

ATC or Aerodrome Reporting Officer (ARO) – callsign (Emerald) Safety Car advise aircraft via light signals if there is an issue with radio communications e.g. Frequency jam

Each light has a meaning for if airborne or on ground: Red; Green; White; Steady & Flashing

Only select ‘ident’ if asked by ATC

Select:

• Standby on ground at aerodromes that do not have ground radar,
• ON is without altitude mode and
• ALT is operated in most operations in CTA.

• Squawk code 7600 on transponder
• Continue with Radio Calls with Prefix “Transmitting Blind”
• Maintain visual lookout
• Listen out on ATIS or NAVAID frequency

In the event of an emergency 2 radio calls can be expected, either:

• mayday (repeated three times) for a distress call
• pan-pan (repeated three times for an urgency call

Distress signals (CAR 192):

• The distress signal shall be transmitted only when the aircraft occupants are threatened with grave and immediate danger and require immediate assistance.

Example:

Mayday, Mayday, Mayday
[agency being called]
[aircraft identification]
[nature of distress condition]
[intention of the person in command]
[present position, altitude and heading]

Each frequency transfer will commence communication with ‘Acknowledge Mayday’.

Distress traffic have absolute communication priority until distress cancelled or transferral of frequency.

Imposed by Aircraft in Distress or ATC:

• ‘All Stations / [aircraft callsign to be silenced]
• Stop Transmitting
• Mayday’

Until:

• ‘Distress Traffic Ended’

Broadcast Mayday Mayday Mayday fuel:

• Fuel < Flight Fuel + Fixed Reserve
• (to nearest aerodrome)

This occurred after the investigation of 2 Boeing 737 (QF & VA) having to divert from AD to MIA due to fog and landing with low fuel.

Urgency signals (CAR 193):

• Used by an aircraft for the purpose of giving notice of difficulties which compel it to land without requiring immediate assistance:

‘Pan-Pan, Pan-Pan, Pan-Pan’
[agency being called]
[aircraft identification]
[nature of urgency problem]
[intention of person in command]
[present position, altitude and heading]
[any other useful information]

Each frequency transfer will commence communication with ‘Acknowledge Pan’

Aviation radios are transceivers. They both transmit and receive radio waves. (They send and receive communication)

• Sound Waves are converted to an electric message via a Microphone
• There are different types of microphones, that vary in how they convert sound and the quality that they achieve.

A radio transmitter consists of several elements that work together to generate radio waves.

• Microphone (Transducer): Converts voice (pressure in the form of sound waves) to an electrical information (voltage).
• Oscillator: It creates an alternating current at the frequency on which the transmitter will transmit. The oscillator usually generates a sine wave, which is referred to as a carrier wave.
• Modulator: It adds useful information to the carrier wave. There are two main ways to add this information. The first, called amplitude modulation or AM, make slight increases or decreases to the amplitude of the carrier wave. The second, called frequency modulation or FM, make slight increases or decreases the frequency of the carrier wave.
• Amplifier: It amplifies the modulated carrier wave to increase its power. The more powerful the amplifier, the more powerful the broadcast.
• Antenna: It converts the amplified signal to radio waves.

A radio receiver is the opposite of a radio transmitter. It uses an antenna to capture radio waves, processes those waves to extract only those waves that are vibrating at the desired frequency, extracts the audio signals that were added to those waves, amplifies the signals.

• Antenna: It captures the radio waves. Typically, the antenna is simply a length of wire. When this wire is exposed to radio waves, the waves induce a very small alternating current in the antenna.
• RF amplifier: A sensitive amplifier that amplifies the very weak radio frequency (RF) signal from the antenna so that the signal can be processed by the tuner.
• Oscillator: It creates an alternating current at the frequency on which corresponds with the tuned frequency. This carrier wave will be used as a base for the removal process by the detector.
• IF Amplifiers: A two stage amplifying process.
• Detector: It is responsible for separating the audio information from the carrier wave.
• Audio amplifier: This component’s task is to amplify the weak signal that comes from the detector so that it can be heard. A squelch circuit controls the Audio amplifier, to remove undesired noise.

Different antennas for different functions (eg HF, VHF, VOR, GPS, ELT). The length of the antenna must be ½ the wavelength, often they can use the aircraft itself to supply ¼ of this wavelength.

VHF antennas (1/4 wavelength) are low drag stub units placed on the top (and bottom) of the aircraft fuselage (body). Larger aircraft have more VHF radios (usually 3) and will have at least one antenna on the bottom of the fuselage.

If shielded by buildings or other parts of the aircraft, the reception will be reduced or not received.

For most aircraft, antennas are used for both transmitting and receiving.

This animation shows a half-wave dipole antenna receiving power from a radio wave. The antenna consists of two metal rods each one-quarter of the wavelength long, attached through a parallel transmission line to a resistance R equal to the characteristic impedance of the antenna, representing the receiver.

The electromagnetic wave, coming from the right, is represented by its electric field (E, green arrows) (it should be kept in mind that the drawing only shows the field along one line, while the radio wave is actually a plane wave and the electric field is actually the same at every point on a plane perpendicular to the direction of motion). The wave’s magnetic field is not shown.

The oscillating electric field exerts force on the electrons in the antenna rods , causing them to move back and forth in currents (black arrows) between the ends of the antenna rods, charging the ends of the antenna alternately positive (+) and negative (−). Since the antenna is a half-wavelength long at the radio wave’s frequency, it excites standing waves of voltage (V, red) and current in the antenna.

Amplitude Modulation (AM)

Frequency Modulation (FM)

Pulse Modulation (PM)

• The aim of pulse modulation methods is to transfer a narrowband analogue signal, (for example a phone call), over a wideband baseband channel or, in some of the schemes, as a bit stream over another digital transmission system.
• In music synthesizers, modulation may be used to synthesise waveforms with an extensive overtone spectrum using a small number of oscillators. In this case the carrier frequency is typically in the same order or much lower than the modulating waveform.
• In terms of what we are looking at – Pulse Modulation can be something as ‘simple’ as ON/OFF encoding!

The squelch controls the strength at which a received signal must be before it is passed to the audio amplifier.

For maximum reception sensitivity you would ordinarily turn the squelch control all the way down at which point you will hear a hissing sound from your receiver (also ignition and alternator noises, if present). This setting, with the squelch disabled, allows you to receive the weakest signals.

It also causes that hiss when no signal is being received . . . it is not an atmospheric noise being picked up by the antenna. As you turn the squelch control up, there will be a point where the hissing noise disappears. This is the correct setting for your squelch control. Turning the squelch any further than this will prevent the receiver from picking up weaker signals.

All aviation headsets have the ability to transmit and receive.

Some are better at protecting from hearing loss. (eg David Clarks)

Some are noise cancelling (doesn’t protect from hearing loss). (eg Bose)

Some are not required to protect from hearing loss or noise cancelling. (e.g. seinheiser headsets are commonly used in jets.)

To turn a handheld radio on turn the Power/ Volume switch clockwise.

Includes:

• Battery
• Aerial
• Power/ Volume Switch
• Press to Talk (PTT) Switch
• Microphone
• Speaker
• Squelch Control Switch
• Frequency Display
• Keypad/ Frequency Selector
• Charging Station

Avionics = Aviation + Electronics

Avionics refers to all the aircrafts electronics, this can include Navigation Units, GPWS, Autopilot systems, Flight Management Guidance Systems / Computers etc. Avionics Engineers are specialists who maintain these electronics.

To turn a fixed radio on:

• Turn the aircraft Master Switch ON
• Turn the Avionics Master Switch ON
• Ensure the Radio/ Volume Switch is ON @ approx 12-2 o’clock position

Frequencies are generally selected in the Standby (right hand frequency display):

• There are 2 knobs within the radio (red circle) they are place one inside the other
• To change frequency increase with clockwise rotation / decrease with anti-clockwise rotation:
• the larger outer knob will change the numbers to the left of the decimal point
• The smaller inner knob will change the decimal numbers
• To make this standby frequency active press the white Frequency Transfer button <->

• Includes:
  • Power/ Volume Switch
  • Squelch Control Switch
  • Frequency Displays
  • Frequency Selectors
  • Frequency Transfer Button
• Attached to:
  • Aircraft Battery via an Avionics Master Switch
  • Aircraft Aerial
  • Audio Control Panel
  • Press to Talk (PTT) Switch
  • Microphone
  • Speaker

Radio interfaces in more advanced aircraft will look similar to these.

Garmin combine radios and GPWS navigation in this example.

Airbus radio frequencies are selected via a Radio Management Panel (RMP) – not shown
Airbus Audio is selected via an Audio Control Panel (ACP) – bottom left

• Select and illuminate pushbutton to select speaker volume
• Select and illuminate mic pushbutton to speak on VHF, HF radios, or INT intercom, or CAB cabin, or to make an announcement on the PA public announcement
• An additional option for the intercom and radio is a selection switch which makes the mike live, this is similar to what is on General Aviation (light) aircraft.

Use a logical sequence to problem solve radio problems:

1. Antenna (handheld check secure)
2. Audio Panel:
   1. Check selected correct radio
   2. Try another audio selection: speaker, headsets
3. Radio:
   1. Check volume
   2. Check frequency
   3. Use another radio
   4. Disable squelch
   5. Check that your microphone is not stuck on….
4. Speaker:
   1. Check your headset is plugged in
   2. Try another headset
   3. Try another headset jack

Communications failure checklist

• Check volume.
• Check audio panel switches.
• Change to an active frequency and listen.
• Switch radios.
• Reset the microphone and headphone plugs.
• Try an alternate headset or speaker.
• Disable squelch and listen for receiver hiss.
• Transmit and listen for sidetone.
• Use another microphone.
• Use a handheld transceiver.

Essential for communication to ensure:

• Separation standards are maintained.
• High Situational Awareness.
• Well informed Decisions.
• Safety is maintained.

• When we speak, our vocal chords create pressure waves or sound waves.
• These dissipate as they move further away, like ripples in a pond (attenuation).
• Human hearing detects frequencies between 20 – 20000 cycles per second (Hertz)

• A radio wave is generated by a transmitter and then detected by a receiver.
• An antenna allows a radio transmitter to send energy into space and a receiver to pick up energy from space.
• Transmitters and receivers are typically designed to operate over a limited range of frequencies.

Sound waves are the movement of energy (not molecules):

• Air is compressed and expanded
• Sine wave / curve shape

Sound waves don’t move the molecules, similar to a Mexican wave at a sporting stadium, the people don’t move but the wave energy does.

• Wavelength is the distance between each cycle
• Amplitude is the ½ height of each cycle
• Frequency is the number of cycles per second

Radio Waves use excitement of electromagnetic waves:

• Can travel through space
• No air or water required

What determines which frequency to use?

The ionized part of the Earth’s atmosphere is known as the ionosphere. Ultraviolet light from the sun collides with atoms in this region knocking electrons loose. This creates ions, or atoms with missing electrons. This is what gives the Ionosphere its name and it is the free electrons that cause the reflection and absorption of radio waves.

https://sciencestruck.com/ionosphere-facts

Sun’s UV light collides with atoms knocking electrons loose:

• Ions are atoms with missing electrons

Free electrons cause reflection and absorption of radio waves.

Interesting facts about the Ionosphere:

• One of the most noted and interesting facts would be the formation of aurora. The aurora is an illusive natural phenomenon, which usually occurs near the Northern (Aurora Borealis) and Southern (Aurora Australis) Hemisphere.
• It is associated with a magnificent display of chromatic lights swirling in the northern and southern skies. They were considered to be indications of an approaching adversity or catastrophe in ancient Greek and Roman cultures.
• They occur in the ionosphere due to the exchange of photons from unstable nitrogen and oxygen atoms, destabilized by collision of the solar wind particles.
• It is also considered that auroras are the result of emission of atmospheric gases.
• What causes lightning could be a question which might intrigue us. Lightning is said to take place in the ionosphere.
• When liquid and ice particles clash with each other, they form massive electrical fields, dissipating an electric spark, which we refer to as lightning.
• The temperature inside a lightning bolt reaches around 50,000º C, which is even greater than the surface temperature of the sun!

Think about visualizing water waves, then consider how we know light behaves too – to help understand these behaviours.

Ground Wave Propagation:

• Refraction – Follows the contour of the earth
• E.g. Radio below 2MHz frequency

The strength of the groundwave is inversely proportional to frequency, being strongest at low frequencies. As frequency is increased, the distance covered by the groundwave decreases.

A ground wave is considered to have 2 components: a surface wave (travels entirely along the earth’s surface) and a space wave.

Sky Wave Propagation:

The Ionosphere reflects the electromagnetic waves, this zigzag pattern will vary depending on the atmosphere.

Reflects off the Ionosphere, e.g. HF Radio.

The Ionosphere reflects the electromagnetic waves, this zigzag pattern will vary depending on the atmosphere.

For HF radios note the reception created by where the wave is meeting the ground. There are areas of no reception for HF radios, yet at greater distances from the source, the reception improves again. This is normal for HF radios.

Space Wave (Line of Sight) Propagation:

E.g. VHF Radio & Mobile Phones.

While the distance between towers is not so relevant, it is more relevant to consider how far from the VHF transmitter we can operate.

D and R calculate the distance between towers for effective communication

To work out the exact distance a VHF signal will travel, you can use the following equation:

So, with an aircraft at 36,000 feet and the ATC radio tower at 100 feet, communication will be possible up to 250 nautical miles away. However, this is the theoretical optimum and will be much less in practice due to transmitter power and receiver inefficiencies.

Ionosphere affects HF Radio:

During the day, energy from the sun causes the D, E and F layers to become heavily ionized, making the layer more active. At night, with less energy from the sun, only the E and F layers are active. As a result, lower frequencies are better quality during the night and higher frequencies are better during the day.

However, what HF gains in distance, it loses in quality. Quite often, the quality of the signal is so poor that it’s impossible for either station to hear each other.

Terrain – VHF Radio:

Just like your mobile phone if there is terrain between you and the transmitting tower, you will not be able to send and receive messages via your VHF radio.

Sunspot activity – HF Radio:

The level of sunspot activity has an enormous effect on the ionosphere and hence on HF radio propagation conditions.

These sunspots are areas where there is intense magnetic activity. 

Around the sunspot there is an area called a plage. This is slightly brighter than the surrounding area and it is a large radiator of cosmic rays, ultra-violet light and X-rays. In fact it results in the overall level of radiation coming from the sun to increase. In turn this increased radiation level from around the sunspots causes the ionosphere to become ionised to a greater extent. This means that higher frequencies can be reflected from the ionosphere.

The higher the levels of radiation received from the Sun, the greater the levels of ionisation in the ionosphere and in general this brings better propagation conditions for HF radio communications.

It is found that over a period of approximately eleven years over which the sunspots vary. At the peak of this cycle conditions on the bands at the top of the short wave spectrum are very good. Low power stations can be heard over remarkably long distances. At the bottom of the cycle bands around 30 MHz will not usually support normal propagation via the ionosphere.

Thunderstorms and Atmospheric Static – HF & VHF:

What is thunderstorms and atmospheric static, and what it means for radio:

• Discharge of static electricity in the Atmosphere
  • Lightning from Thunderstorms is the most visual source
    • Lightning scatters radio waves for a fraction of a second
    • Brief noise burst makes frequency unusable
  • Non-Lightning discharges also occur regularly
• HF – Noise is louder on lower frequency bands
  • Can be heard several hundred miles from the source
• VHF – Noise also occurs on lower frequencies when storms close to the receiving antenna 

Atmospheric noise, caused by lightning discharges in thunderstorms, is normally the major contributor to radio noise in the HF band:

• Thunderstorm occurrence is greatest at low latitudes and varies seasonally.
• Atmospheric noise can be impulsive when storms are proximate to the receiving antenna, or display a broad continuum when storms are remote.
• This noise may display some directionality depending on the location and spread of storms with respect to the receiving antenna.
• Atmospheric noise effects are greater at lower HF frequencies so are likely to affect signal quality during the night and solar minimum when lower frequencies are in use.

Lightning scattering has sometimes been observed on VHF and UHF over distances of about 500 km. The hot lightning channel scatters radio-waves for a fraction of a second. The RF noise burst from the lightning makes the initial part of the open channel unusable and the ionization disappears quickly because of recombination at low altitude and high atmospheric pressure. Although the hot lightning channel is briefly observable with microwave radar, no practical use for this mode has been found in communications.

Static/noise also occurs from other Atmospheric Static sources:

• Rain Static
• Snow Static

Installation of Static Dischargers or Wicks:

Static dischargers, or wicks, are installed on aircraft to reduce radio receiver interference.

Static dischargers are normally mounted on the trailing edges of the control surfaces, wing tips and the vertical stabilizer. They discharge precipitation static at points a critical distance away from avionics antennas where there is little or no coupling of the static to cause interference or noise.

Interference from electrical equipment – HF & VHF:

Just like your car radio receives interference from electronic devices, so does your Avionics Radio – HF & lower frequencies most affected.

Any other device creating an electromagnetic wave could create interference:

• Electrical motors
• Power lines
• Mobile Phones

Attenuation is the reduction of signal strength.

This can be caused by:

• Distance from the transmitting station.
• Atmospheric conditions:
  • As a radio wave passes through the atmosphere the electrons in dust and water droplets absorb some of the energy causing atmospheric attenuation.
  • In a vacuum there is no attenuation as the radio wave has nothing to give up its energy to.
• Physical Blockages by obstruction, creating shadowing:
  • Buildings
  • Trees
  • Terrain