Date: July 31st, 1973
Type: McDonnell Douglas DC- 9-31
Operator: Delta Air Lines
Where: Boston-Logan IAP, MA (USA)
Report No.: (NSTB-AAR-74-3)
Report Date: -
This is not an accident investigation report.
As Delta Flight 723 was descending, the approach clearance was given by the
controller after a delay, because the controller was preoccupied with a
potential conflict between two other aircraft. This caused the flight to be
poorly positioned for approach. The aircraft passed the Outer Marker at a
speed of 385km/h (80km/h too fast) and was 60m above the glideslope.
The flight director was inadvertently used in the 'go-around-mode', which
led to abnormal instrument indications. This caused some confusion. The
first officer, who was flying the approach became preoccupied with the
problem. The DC-9 continued to descend and struck a seawall 3000ft short of
and 150ft to the right of Runway 04R, crashed and caught fire.
RVR at the time was 500m with 60m overcast.
PROBABLE CAUSE: "The failure of the flightcrew to monitor altitude and to
recognize passage of the aircraft through the approach decision height
during an unstabilized precision approach conducted in rapidly changing
meteorological conditions. The unstabilized nature of the approach was due
initially to the aircraft's passing the outer marker above the glide slope
at an excessive airspeed and thereafter compounded by the flightcrew's
preoccupation with the questionable information presented by the flight
director system. The poor positioning of the flight for the approach was in
part the result of nonstandard air traffic control services." (NSTB-AAR-74-
Source: Air Disasters / D.Gero (118-120)