18th annual conference on manual control.pdf - Acgsc.org

"['he total number of messages transmitted between pilots and controllers
and messages specifically related to traffic may be seen
in Table 2. On the average._ nearly 200 messages were transmitted
by the two controllers and seven pilots during each set of
approaches. Although there were an approximately equal, number of
messages originating with the air" and ground_ the information
content was quite different. More than twice as many altitude,
speed, r:Iearance, and vector commands, queri es._ and responses
originated with ATC as from the pilots. Twice as many positionrelated
messages originated with the pilots as with the controllets,
and four times as many acknowledgements. All of the controller
acknowledgements were simple "rogers", where as the majority
of the pilots =' inw_ived a complete or partial, readback.
In general, there were fewer transmission with all CDTIs than
someCDTIs (200 versus 189). This was attributable to fewer vectors
issued from ATC and fewer position-related transmissions from
pil.ots (Table 2). For" those messages specifically related to
traff:ic, however, the reverse was true. There were more trafficrelated
messages when all pilots had traffi.r, displays (7.4) than
when only some pilots had them (I:|.2). It was apparent that ATC
did use the pilot's ability to see other aircr'aft on the CDTI when
it was available to involve pilots in maintianing "visual" separation
by giving traffic advisories and clearances to follow other
aircraft, and directing pilots to maintain separation from aircraft.
In general, the additon of VFR data tag information, had
less impaczt, although the number of position-related messages did
decrease from 31 to 25, on the average, with its addition.
Table 3 presents the communications analysis by e,rperimental condition,
air_.-.raft type, and topic, with messages to and from
pilots c:ombined. Pilots of single engine PP air'€_-raftwere given
and initiated the Tewest c'ommunic:ations. This is consistent with
the observation that ATC vec:tored these a:ir'craft out of the way
of the faster traffic and ignored tlnen until, other faster* air-
€..-.raft had passed. 'their most frequent type of rommunication was
a command to maintain present status or a readback.
Both PP and SP twin-engine aircraft were given more vectors than
any other" c:ommmand., and received and provided a number of position
queries. Both types of communications were most evident when
information about the altitude of the VFR aircraft was not known
and ther-e were no tr'affi_-_displays in the simulators. In addition,
there were a large number o,f "maintain..." c:ommands given to
these aircraft in the no]AG, aIICDTI condition.
The pilots of the jets part:_.-.ipated in relatively fewer c:ommunications
than did the pilots. In general., the presence or absence
of altitude information for' VFR a'.ircraft affected the frequency of
responses made by jet pilots differently deper_ding on whether or
not they had a CDTI. They were given more altitude and speed
changes than were the pilots of 'the twin-engine aircraft, but half
as many vectors., There were mor'e messages on the whole with CDTI
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