NTSB/AAR-84-09 - AirDisaster.Com

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The approach emtroller said that there were no other beacon targets or
prlcnary targets near the 0662 code. He said he was aware of the altitude difference, but
h? also was aware that Flight 797 had declared nil emergency and was probably
uescending. Therefore, the mode C altitude data might be lagging. At the time of the
handoff, he had not been told the flight's assigned heading. Believing he had identified %e
correct airplane, he assigned a radio frequency and waited for Flight 797 to cor,tact him.
The approach controller stated that after he had requested the 090' turn and
saw no response from the target he had been obscving, he observed a partial data. block
containing an Air Canada 797 identification tag in the vicinity of the secondary target he
had initially identified as Flight 797; the TRACON supervisor also stated that he had seen
this data block. Pbout 1911, the Evansville/Nabb D controller had "forced" an amended
flight pla? for Flight 797 into the Cincinnati ARTS III equipment. The flight plan, as
amended, contained Flight 797's assigned transponde: code, changed its destinstion to
Cincinnati, and stated that the flight was Gescendi~g to 10,000 feet. Had Flight 797's
transponder been operating, the "force" would have configdred the Cincinnati AriTS III
computer to accept an automated handoff at the geographic point where the computer
was programmed to accept handoffs from the EvansvUelNabb sector. However, since
Flight 797's tramponder was inoperative, the ARTS 111 computer could not loeaze a beacon
target to associate with the :'forced" data block and the .'force" merely placed the data
block on the approach controller's radarscope. The data block, because it did not match a
properly mded beacon target, was displayed only for about three radar sweeps.
The approach controller was asked, based on his emergency arccedures
training, how far from the threshold of runway 36 he would have had to have p:aeed Flight
797 in order for it land on that runway. He testified that it would depend on the weather.
If the descent :vas conducted in visual flight conditions, he thought that "the pilot might
be able to descend from five or six thousand feet from a point ten miles swath of the
airport at a slowe? speed and complete a landing. If it were an IFR (instrument flzht
rules) approach, he'd want to be level at twenty-five hundred feet or three thousand fe,et
maybe seven or eight or ten miles from the airport. In this situation, it was difficult for
me to judge how quickly the aircraft could descend (and) how tightly he could turn." The
controller testified that he wanted to avoid vectoring Flight 797 to runway 36, have it
arrive too high anl too close to the runway threshold to complete the landing, and ?hen
have to circle the airport in order to lard on another runway.
The controller was not familiar with nor was he required to be familiar with
either the indicated airspeeds or ?he dcscent rate capabilities of a DC-9-30 airplane
diiring an emergency desctn:. He also said that even if he had identified Flight 797's
primary target earlier he would not have turned the Fight away from the airport and
towat-d the soath in order to space it to !and on runway 36. He would have "kept him
goiq for the airport at all times."
1.17.6 ATC Radar Data
Data .4nalysis Reduction Tool (DART) radar data information was obtained
from the Indianapolis ARTCC. The data included airplane position informtion and
available mode C altitude information for Flight 797 and for Continental Airlines Flight
383, which was transmitting on eode 0662. The Safety Board's laboratory reconstructed
the ground radar tracks of both Flights 797 and 383. Runways 9K-2;L and
- 12/ A movable position identification device available to the controilm to identify radar
terz-pts on his radarscope.
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