Speech Acts and Aviation Topics

Aviation Topic and Speech Act Taxonomy (ATSAT) was found to be suitable for coding the radiotelephony messages (Searle, 1969; Prinzo and Britton, 1993; Prinzo, Britton, and Hendrix, 1995; Kanki and Prinzo, 1996; Prinzo, 2002). The latest update to ATSAT was the inclusion of complexity measure in a document titled The Communication Data Dictionary and Procedures Manual (Prinzo and Hendrix, work in progress). Table 4-7 contains the Speech Acts categories used for radiotelephony transcript coding. Each speech act is associated with relevant aviation topics to further classify the phrases.

Table 4-7 : Definition of Speech Act Categories and Codes

Speech Acts Code Definition

1 Address / Addressee _{Rid / Sid} Identifier of station as speaker or receiver for example facility name or aircraft callsign 2 Courtesy _C Word(s) or phrase(s) spoken as an act of

courtesy. Eg. Good morning. 3 Instruction /

Clearance - readback / acknowledgement

I

Phraseology used by a controller in issuing instructions to an aircraft. Eg. Climb to flight level one four zero

4 Advisory / Remark – readback /

acknowledgement A

Communication required as part of

controller’s responsibility to issue pertinent information eg. Traffic, altimeter setting and altitude. It also includes pilot’s responsibility in reporting position, altitude or speed. 5 Request – readback/

acknowledgement R

Initiated by pilot or controller for the purpose of acquiring information or authorisation 6 Non-codable

N

Remarks or comments that do not fit into the other speech acts, or unintelligible due to delivery technique or technical.

Some additional topics had been added to the list used by Prinzo & Britton (1995) which was based on approach control communications. The data used in this research includes area radar and tower control radiotelephony, thus additional topics were needed to accommodate the wider scope. Table 4-8 show the aviation topics and related codes, as used for processing the radiotelephony data in this research.

Table 4-8 : Aviation Topics, Codes and Explanation

AVIATION TOPIC Code Explanation Speaker identification Sid identity of the speaker

Receiver identification Rid identity of the intended recipient

altitude / level alt Altitude assigned by a controller or readback by a pilot

approach

app Clearance by controller to make an approach to airport or to assigned runway; or readback by a pilot

circuit

cct Clearance related to positions in aerodrome circuit eg. Downwind, base.

communications

com Radio frequency used for communication as assigned by a controller or readback by a pilot

flight details fld Fuel endurance, POB, etc

general gen Okay, roger, alright or words used as acknowledgement heading hdg An assigned vector or readback by a pilot

holding

hol Holding instructions issued by a controller or readback by a pilot

landing

ldg Authorisation to land on assigned runway or acknowledgement by a pilot

repeat/ verify ver Say again, confirm restriction rst Eg. Crossing time, levels

route / position

rpo Instruction by a controller pertaining to assigned course of aircraft or readback by a pilot. This also applies to positioning on ground for aircraft taxying.

speed spd Speed assigned by a controller or readback by a pilot start stt Engine start-up

takeoff tof Cleared for takeoff and runway designation

traffic

tfc Information on conflicting traffic eg. Aircraft type, altitude, position

transponder

ssr Beacon code assigned by a controller or ident instructions or readback by a pilot

visual / sighting vis Declaration of visual contact, in sight.

weather info wxi Altimeter setting, cloud, wind, weather warning, turbulence Apology apo Sorry, apologies

Greetings grt Good morning, hello, good day Thank you tq Words showing appreciation delivery dlv unintelligible

Speech acts and aviation topics codes were used in pairs, for example ‘Ialt’ to indicate an instruction/readback (I) of an altitude/flight level (alt). These paired codes will be referred to as an ‘element’. Only the speaker and recipient identity will use unique codes of Sid and Rid respectively. Transcribed radiotelephony was parsed into speech acts and aviation topics, and then coded by ATSAT elements in the order that these were used. The types of elements were organised in the database corresponding to the messages. The full list of elements is shown in Appendix H.

The following example in Table 4-9 is a message from Indonesian 856 to Kuala Lumpur area radar controller, addressed as Lumpur Control. The message consisted of 5 elements which were listed as T1 to T5. The first element was a courtesy (C) with a greeting (grt), coded as Cgrt. Rid is a recipient identification or who the message was for, which was Lumpur Control. Sid is speaker identification, in this case, Indonesian 856 that transmited the message. ‘Flight level three four zero’ was altitude information provided by the speaker, coded as Advisory (A) and altitude (alt). The last element was a request (R) for change of altitude, coded as ‘Ralt’.

Table 4-9: Identifying Speech Acts and Aviation Topics

Message T1 T2 T3 T4 T5

GOOD EVENING / LUMPUR CONTROL /

INDONESIAN EIGHT FIVE SIX / FLIGHT LEVEL THREE FOUR ZERO / REQUEST DESCEND Cgrt Rid Sid Aalt Ralt

The total numbers of elements used in each message, as well as number of Instructions and Advisory were noted. In the last example, there was one Advisory and one request but no instruction as the message was transmitted by the pilot.

An example of a controller’s message containing 7 elements;

“Malaysian One Two Eight Nine (Rid) Approach (Sid) Good Evening (Cgrt)

Descend Seven Thousand (Ialt) QNH One Zero One … One Zero Zero Seven (Awxi) Fly Heading Two Three Zero (Ihdg) Radar Vector for Final (Arpo) ”.

There were two instructions, two advisories, a courtesy greeting and two for speaker and recipient identities (the elements shown in brackets).

The processing also included word count for each message which could be used to calculate speech rate in words per minute. Numerals were also counted separately as these are used very frequently in ATC. As in the message above, twenty eight words were transmitted in ten seconds, making the speech rate equivalent to 168 words per minute. Out of 28 words, 16 (more than 50%) were numerals. 6 words were used for identification purposes, 2 in greeting, 12 for advisories and only 8 for instructions. There was also a noticeable pause in the middle of the transmission after which the altimeter setting (QNH) information was corrected. Pauses are considered as disfluencies and will be coded accordingly.