1955 — July 17, Braniff Air 560 hits sign on approach/crashes, Chicago-Midway AP, IL–22
–22 AirDisaster.com. Accident Database. “Accident Synopsis 07171955.”
–22 Aviation Safety Network. Accident Description. Braniff Airways Flight 560, 17 Jul 1955.
–22 CAB. AIR. Braniff Airways, Chicago Midway Airport, Chicago, Illinois, July 17, 1955.
–22 Eckert. “Fatal commercial air transport crashes, 1924-1981.” AJFM&P, 3/1, Mar 1982, Table 1.
–22 NFPA. “Summary of Large Loss Aircraft Fires.” Quarterly…NFPA, 49/3, Apr 1956, p394.
Narrative Information
Civil Aeronautics Board, Aircraft Investigation Report: “At 0624, July 17, 1955, while completing an instrument approach to the Chicago Midway Airport, Braniff Airways Flight 560, a Convair 340, N 3422, struck an advertising sign located at the intersection of 55th Street and Central Avenue, Chicago Illinois. The aircraft continued through the airport boundary fence and stopped inverted on the airport. Of the crew of 3 and 40 passengers, the captain, the hostess, and 20 passengers received fatal injuries, the first officer and 11 passengers sustained serious injuries, and the remaining 9 passengers received minor or no injuries. The aircraft was demolished by impact and fire.
“Flight 560 is a Braniff daily scheduled flight between Dallas, Texas, and Chicago, Illinois, with intermediate stops at Oklahoma City, Oklahoma; Wichita, Kansas; and Kansas City, Missouri….
“The commercial sign struck was located on the northeast corner of the intersection between 55th Street and Central Avenue where they bound the north-west corner of the Chicago Midway Airport. The sign was mounted near the top of a steel post 11 inches in diameter and 18 feet, 2 inches high. The sign was located approximately 82 feet from the nearest airport boundary fence and 1,000 feet from the threshold lights of runway 13R. Relative to the ILS glide path and localizer course centerlines the top of the sign was about 84 feet below and 122 feet left, respectively. The height of the sign at its location was also approximately 12 feet lower than the allowable height as determined by the obstruction clearance criteria. 2 The glide path intersects the runway l,600 feet past the sign. A single row of red high intensity approach lights are installed on the left side of the runway centerline and extend 1,300 feet outward into the approach area. These lights slope gradually higher toward the outward end and opposite the sign are nearly its height.
“The right wing of the aircraft struck the sign about 18 inches below the top…. The impact caused failure of integral wing structure just outside of its engine nacelle and the wing quickly separated upward and rearward into the right horizontal stabilizer. The aircraft then rolled progressively to the right as it crashed through the fence and struck several approach light installations. Nearly inverted, the aircraft slid through raised concrete runway identification markers onto the north-south taxiway where it stopped inverted…. Fire broke out during this time and rapidly increased in intensity until it was quickly extinguished by airport firemen who reached the scene less than a minute after the accident.
“Impact forces with the sign, ground, light installations, and runway markers were severe. They mutilated the nose section of the aircraft, caused extensive damage to the fuselage, and tore off the empennage. In several areas the top and bottom of the passenger cabin were crushed close together, preventing several passengers from escaping until freed by the efficient efforts of the emergency personnel….
“Many witnesses offered important information concerning the fog and its density. Many on the scene when the accident happened concurred that the fog there was very dense. They pointed out that the fog density rapidly increased a few minutes before the accident, then decreased after it. They pointed out that objects only a few hundred feet from them could not be seen at the time. Motorists stated that west of the scene the fog was quite dense and in several cases they used headlights while driving. Others approaching from the east said the fog did not hamper their driving but when they reached the immediate area visibility rapidly deteriorated until it became extremely poor. An air carrier flight crew testified that while taxiing on the north taxiway from the terminal to runway 13R visibility became somewhat poorer but remained at least one-half mile. One crew member noted several drifting fog patches while taxiing….
“The available evidence indicates that Flight 560 was well planned and conducted in a normal manner until it was near a position approximately one-half mile from landing….
“As previously shown the sign was about 20 feet high. With respect to the ILS glide path and localizer course centerlines it was approximately 84 feet below and 122 left, respectively. It was 12 feet lower than the allowable obstruction height at that position established by the obstruction criteria. Although the Board considers construction of the type exemplified by this sign below an approach area undesirable, it believes this accident resulted primarily because of the extremely low altitude of the flight rather than the height and position of the sign….
“After passing the one-half mile from touchdown position the aircraft departed from the glide slope and descended rapidly. Considering the various factors involved this descent averaged at least 2,000 feet per minute between the one-half mile position and the sign.
“It is believed that as the flight approached the middle marker the pilots probably established visual contact with the outward end of the approach lights and proceeded visually….
“Without doubt the accident area was engulfed in dense fog which would limit flight visibility to near zero. It is believed that this was confined to a relatively small area and was unknown to the pilots or to ground personnel in a position to alert them.
The importance of more precise and accurate weather reporting for the normal breakout area of an ILS approach has resulted in an endeavor, for several years, to develop instruments to measure the conditions in this area. As a result end-of-the-runway electronic equipment is becoming available. The U. S. Weather Bureau has obtained 20 sets of end-of-the-runway instruments consisting of a rotating been ceilometer for ceiling measurement and a transmissometer for visibility measurement. Installation of these instruments is being accomplished on a priority basis with high volume traffic airports receiving first consideration. As a result a ceilometer has already been installed and is in operation at the Chicago Midway Airport; the transmissometer has also been installed but was not yet in operation as of October 31, 1955. The program for the installation of the balance of these instruments at various airports will continue during this fiscal year, with 45 additional sets programmed for the fiscal year 1957 as received from the manufacturer. The Board wishes to endorse this program and recommends that it progress as expeditiously as possible.
“Based upon available evidence the Board does not believe (1) that the pilot continued below the prescribed minimum altitude without having had visual references, or that (2) as he descended visually he saw the heavy fog before entering it. Although it cannot be positively stated on the available evidence and without the first officer’s recollection, it is believed that after visual contact had been made and the aircraft adjusted for landing the flight unexpectedly encountered the area of fog which reduced the flight visibility to zero. During the necessary transition back to flying the aircraft by reference to instruments it is believed that the pilot experienced momentary disorientation during which the aircraft descended more rapidly before corrective action could be taken….
“The Board determines that the probable cause of this accident was momentary disorientation caused by the loss of visual reference during the final visual phase of the approach resulting in an increased rate of descent at an altitude too low to effect recovery.” (CAB. AIR. Braniff Airways, Chicago Midway Airport, Chicago, Illinois, July 17, 1955.)
Sources
AirDisaster.com. Accident Database. Accident Synopsis 07171955. Accessed at: http://www.airdisaster.com/cgi-bin/view_details.cgi?date=07171955®=N3422&airline=Braniff+Airlines
Aviation Safety Network. Accident Description. Braniff Airways Flight 560, 17 Jul 1955. Accessed 2/21/2009 at: http://aviation-safety.net/database/record.php?id=19550717-0
Civil Aeronautics Board. Accident Investigation Report. Braniff Airways, Inc., Chicago Midway Airport, Chicago, Illinois, July 17, 1955. Washington, DC: CAB, Nov.15, 1955, 11 pages. At: http://dotlibrary1.specialcollection.net/scripts/ws.dll?file&fn=8&name=*P%3A%5CDOT%5Cairplane%20accidents%5Cwebsearch%5C071755.pdf
Eckert, William G. “Fatal commercial air transport crashes, 1924-1981.” American Journal of Forensic Medicine and Pathology, Vol. 3, No. 1, March 1982, Table 1.
National Fire Protection Association. “Summary of Large Loss Aircraft Fires.” Quarterly of the National Fire Protection Association, Vol. 49, No. 3, April 1956, pp. 393-295.