1973 — July 31, fog, landing crash into seawall; Delta 723, Logan AP, Boston, MA — 89

lornajarrettblanchard July 31, 1973

–89 Celebrate Boston. Boston Disasters. “Flight 723 Plane Crash, 1973.”
–89 Kimura. World Commercial Aircraft Accidents 3rd Ed., 1946-1993, V.1. 4-11-1994, p. 2-14.
–89 NTSB. AAR. Delta Air Lines…DC-9-31, N075NE, Boston, MA, July 31, 1973. 1974.

Narrative Information

Celebrate Boston: “At 11:08 on July 31st 1973, a Delta Airlines DC-9 crashed into the seawall at Logan Airport while attempting to land, which was just short of the runway. 89 people tragically lost their lives….One person lived for about two hours. A second person, with terrible burns and traumatic injuries, clung to life for four months, and died on December 1st 1973….

“A huge fog bank enveloped Logan Airport on the day of the crash. Flight 723 was on an instrument landing approach. The crew was briefly distracted by an onboard instrument and an air traffic control instruction, and the plane flew right into the seawall in front of the runway at Logan. A plane on final approach behind Flight 723, unaware that Flight 723 had even crashed, aborted the landing due to weather, and later reported zero visibility at 216 feet. The air traffic control tower was actually unaware of the accident for several minutes due to the poor visibility….

“Some of the good results of the Flight 723 crash were recommendations on runway approach lighting systems, changes to a flight instrument, and a pilot advisory that electronic landing conditions may not match actual conditions near a touchdown point.” (Celebrate Boston. Boston Disasters. “Flight 723 Plane Crash, 1973.”)

NTSB: “About 1108 e.d.t. on July 31, 1973, Delta Air Lines Flight 723, a DC-9-31, crashed into a seawall while executing an instrument landing system (ILS) approach to runway 4R on the Logan International Airport, Boston, Massachusetts. There were 83 passengers, 5 crewmembers, and a cockpit observer on board. All occupants, except one passenger, were killed in the crash. The lone survivor, who had been injured critically, died on December 11, 1973.

“The aircraft struck the seawall about 165 feet to the right of the extended runway centerline and about 3,000 feet short of the runway displaced threshold. The aircraft was destroyed.

“The accident occurred during daylight hours. The weather was characterized by lowering ceilings and visibilities; sea fog of increasing density was moving across the airport from an easterly direction.

“The National Transportation Safety Board determines that the probable cause of the accident was 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.” (NTSB 1974, 1) ….

“…Flight 723…was a scheduled passenger flight from Burlington, Vermont, to Logan International Airport (BOS), in Boston, Massachusetts.” (NTSB 1974, 2) ….

“Pilots who were making approaches to runway 4R before and after the accident reported decreasing visibility caused by fog. Eastern Air Lines Flight 572 had completed its landing about 2 minutes before Flight 723 crashed. The first officer stated that the runway was visible from an
altitude between 200 and 300 feet. Eastern Air Lines Flight 1020 which followed about, 4 minutes behind Flight 723; made a missed approach. The captain of Flight 1020 stated that upon reaching the decision height (216 feet), he could see “nothing” and had initiated the missed approach.” (NTSB 1974, 5-6) ….

“The aircraft struck a seawall on the north shore of the Boston Harbor main ship channel. The seawall forma the south boundary of the airport. The elevation of the impact point was 11.45 feet; the elevation of the intended touchdown point was 16 feet. Aluminum scuff marks were found on the rocks 6.2 feet up the seawall. Pieces of wing tip navigation lights were found at each end of the scuff marks. Portions of wing and fuselage structure were found between the edge of the water and the base of the wall….” (NTSB 1974, 9) ….

“Three employees of a construction firm, who were working about 4,000 feet from the impact site, saw fire on runway 4R and drove to the crash site. After leaving his two companions at the crash site to search for survivors, the driver continued on to the airport fire station and alerted the fire chief that there had been an accident on runway 4R. The time was between 1114 and 1115. Airport firefighting equipment was dispatched immediately across the main ramp to runway 4R. The fire apparatus traveled an estimated 1 mile and arrived at the scene in approximately 3 minutes. Before crossing runway 4L, the crew of the leading vehicle requested permission from the tower to cross the runway; this was the tower personnel’s first notification of the accident.” (NTSB 1974, 11)

“Two passengers were found alive and were transported to Massachusetts General Hospital. One survivor died about 2 hours after the accident. The second survivor sustained third and fourth degree burns and traumatic injuries to his lower extremities. He stated that he had been seated in the last row of seats next to a window, and that when the aircraft stopped, he had been assisted in releasing his seatbelt by a passenger next to him. He said that he then had crawled through a window and away from the burning wreckage. He was found by construction workers who stayed with him until an ambulance arrived. He died on December 11, 1973.” (NTSB 1974, 12) ….

“Paragraph 1352 of the FAA Terminal Air Traffic Control Handbook 7110.8C, dated January 1, 1973, requires that whenever the reported weather is below basic VFR minima, an aircraft shall be vectored to intercept the localizer course at least 2 miles from the approach gate and at an altitude not above the glide slope.

“Paragraph 1351 stipulates that the maximum angle for localizer interception is 30 [degrees]. In the case of Flight 723, the interception angle was 45 [degrees].

“Paragraph 1360 of the handbook requires the approach controller provide approaching aircraft with certain arrival instructions or an approach clearance before the aircraft reaches the approach gate. To be included in these instructions are:

(1) The position of the approaching aircraft relative to the final approach fix;

(2) An approach clearance; and

(3) Instructions to the approaching aircraft to monitor the local frequency, to report to the tower when it is over the approach fix, or, alternatively, to contact the tower on the local control frequency.

“In the case of Flight 723, the approach clearance was not issued in accordance with prescribed procedures. Public hearing testimony revealed that at the time the approach controller should have issued this clearance, he was occupied with a potential traffic conflict between two other flights. As a result, an approach clearance was not given to Flight 723 until the crew inquired about it. Shortly thereafter, the approach controller experience communication difficulties with one of the aircraft involved in the potential traffic conflict; this delayed release of Flight 723 to tower control.” (NTSB 1974, 19) ….

“Analysis….the aircraft’s airspeed at the OM [outer marker] was about 206 knots. That speed was 46 knots above the maximum speed recommended by company procedures, and 63 knots above the minimum speed computed for the aircraft’s gross weight, which was estimated at 87,800 pounds…” (NTSB 1974, 21) ….

“The faster-than-normal airspeed during the approach, together with “the delay in initiating the descent, resulted in two other problems for the crew. First, it increased the difficulty they had in capturing and maintaining the glide slope. The aircraft passed over the OM at an altitude more than 200 feet above the glide slope. At normal approach speed the aircraft could easily have reached glidepath altitude by increasing slightly the rate of descent. However, a t the faster-than-normal air- speeds, a rate of descent of more than 1,300 feet per minute would have been required to intercept the glidepath before reaching decision height. If the flightcrew had attempted to capture the glide slope at such a rate of descent, they would have had difficulty decreasing airspeed to an acceptable approach speed.

“Second, through experience and exposure to instrument approaches during instrument meteorological conditions, pilots generally learn to pace their activities while flying such an approach. The faster-than-normal airspeed of Flight 723 during the initial and final phases of its
Approach required the crew to act more quickly than usual.” (NTSB 1974, 22) ….

“The before-landing checklist requires the pilot not flying the aircraft to monitor the approach and to call out, “200′ above, 100′ above, and minimum,” as the aircraft approaches decision height. These call-outs were never made in Flight 723, nor was any reference made to altitude after the aircraft had departed the OM….

“This accident demonstrated how an accumulation of discrepancies, none of them critical, can rapidly deteriorate, without positive flight management, into a high-risk situation. In this regard, the most significant factors were:

1. Vectors given by BOS AR-1 to intercept the localizer course were not according to standard operating procedures; nevertheless, the flightcrew accepted the vectors and continued the approach at an excessive airspeed.

2. Approach clearance and other required instructions first had to be requested by the flightcrew, before they were given to the flight, which delayed the flight’s descent to the correct approach altitude.

3. The first officer, who was flying the aircraft, was preoccupied with the information presented by his flight director system, to the detriment of his attention to altitude, heading, and airspeed control.

4. The captain divided his attention among the problem with the flight director system, the communications with air traffic control, and the weather and visibility information given by the local controller.” (NTSB 1974, 26-27)

Sources

Celebrate Boston. Boston Disasters. “Flight 723 Plane Crash, 1973.” Accessed 10-2-2009 at: http://www.celebrateboston.com/disasters/crash1973.htm

Kimura, Chris Y. World Commercial Aircraft Accidents 3rd Edition, 1946-1993, Volume 1: Jet and Turboprop Aircrafts. Livermore, CA: Lawrence Livermore National Laboratory, Risk Assessment and Nuclear Engineering Group. 4-11-1994.

National Transportation Safety Board. Aircraft Accident Report. Delta Air Lines, Inc, Douglas DC-9-31, N075NE, Boston, Massachusetts, July 31, 1973 (NTSB-AAR-74-3). Washington, DC: NTSB, adopted March 7, 1974, 78 pages. Accessed at:
http://libraryonline.erau.edu/online-full-text/ntsb/aircraft-accident-reports/AAR74-03.pdf