WASHINGTON, D.C. 20594 . z AIRCRAFT ACCl ENT REPQRT .I AMERNAN AIRLIWES, INC., $1 DC-10-10, NllOAA E CHICAGO-B'HARE INTERNATIONIIL AIRPORT CHICAGO. 1ltfMftS UNITED STATES GGVERNMENT i ,. TECHNICAL REPORT WCUMKNTATION PAGE . Report No. 2.Government Accession No. ).Recipient's Catalog No. mSB-AAR-79-17 . Title and Subtitle Aircraft Accrdent Report- 5.Report Date Ameriean Airlines, Inc. DC-10-10, December 21. 1979 NllOAA. Chicarro-O'llare International Airoort 6.Peiforming~. Organization Chicago; IUinoik Mav 25. 1979 I Code . Authorts) I 8.Performing Organization Report NO. Performing Organization Name and Address IO.Uork Unit No. 2662-E National Tnmsportation Safety Board II.Contract or Grant NO. Bureau of Accident Investigation Washington, 20594 D.C. 13.Type of Report and Period Covered 2.Sponroring Agency Name and Address Aircraft Accident Report May 25, 1979 NATIClNAL TRANSPORTATION SAFETY BOARD Washington, D. C. 20594 14.Sponsoring Agency Code I 15.Supplementary g'otes . z i6.Abstract About 1504 c.d.t., Nlny 25, 1979, American Airlines, Inc., Flight 191. a McDonnell-Douglas DC-10-10 aircraft, crashed into an open field just short ,of a troiler park about 4,600 ft northwest of the departure end of runway 32R at Chicago-O'Haru International Airport, Illinois. Flight 191 was taking cff from runway 32R. The weather was clear and the visibility was 15 miles. i takeoff rotation. the left assemb!v an- 2 ft owinn left wine separated huathc wndfell to the runway. Flight 191 continued to climb to about 325fft above the ground and then began to roll to the left. The aircraft continued to ro to the left until the wings were past the vertical position, and during the roll, thee aircraft's nose pitched down below the hcrizon. Flight 191 crashed into the open field and the wreckage scattered into an adjscent trailer park. The aircraft was destroyed in the crash and subsequent fire. Twnedand seventv-on? oersons on board Flight 191 were killed; two persons on the ground were killed. and two others were injured. An old aircraft hangar, several automobiles, and a mcbile home were destroyed. The National Transportation Safety Board determines that the probable cause of this accident was the asymmetrical stall and the ensuing roll of the aircraft I7, , ..You .- , YnrAc.. -. - - Ii8.0istribution Statement his document is available to DC-10; loss of control; asymmetrical stad; stal! warning system; slat disagreement warning he public through the ational Technical Informa- light; structural separation; No. 1 engine and Pylon;.. design criteria: maintenance Drocedureg bonServk?:?pringfield, FAA regulations; industry communications procedures. vlrglnla ZZI~I 19.~~~~~i~~~~~~~ifi~~ti~~20.Security C:assification 21.No. of Pages 22.Price (of this report) (of this page) UNCLASSIFIED UNCLASSIFIED 103 NTSB Form 1765.2 (Rev. 9/74) I because of the uncommanded retraction of the !eft wing outboard leading edge slats and the loss of stall warning and slat disagreement indication systems psu'ttx from maintenance-induced damage leadina to the scparation of the No. 1 tin2 takeoff. The separation rehed frogdemage by hproper mainteiance procedures which led to failure of the pylon'structure. Contributing to the cause of the accident were the vulnerability of the design of the pylon attach points to maintenance damage; the vulnerability of the design . ' of the leading edge slat system to the damage which produced asymmetry; deficiencies in Federal Aviation Administration surveillance. and reporting systems which failed to detect and prevent the use of improper maintenance procedures; deficiencies in the practices and communications among the operators, the manufacturer, and the FAA which failed to determine and disseminele the particulars regarding previous maintenance damage incidents; and the intolerance .. of prescribed operational procedures to this unique emergency. z CONTENTS 1 Synopsis ................................ 1 I 1.1 History of the Flight ...................... 2 s to Persons ....................... 3 I Y.3 Damage to Aircraft ....................... 3 Other Damage ......................... 3 1.5 Fersonnel Information ...................... 3 k .6 Aircraft Information ...................... 3 1.7 hleteorological Information .................... 3,' 1.8 Aids to Navigation ....................... 3 unications ........................ 4 1.10 Aerodrome Information ..................... 4 . 'S ........................ 4 -12 Wreckage and Impact Information ................. 6. 1.13 Medical and Pathological Information ............... 11 1.14 Fire .............................. 11 1.15 Survival AspecLs ........................ 11 ....................... .. n ~~ 1.16.3 Stress Tgsting of the Pylon Aft Bulkhead. ............ 1.16.4 Wind 'runnel and Simulator Tests ................. ;' 22 1 Information ........................ 1.17.1 Air Carrier Maintenance Procedures ................. L 1.17.2 FAA Reporting & Surveillance Procedures .............. " 1.17.5 Msnufaciurer's Production kina Procedures .......... .,. .. 1.17.7 DC-10 Electrical & Hydraulic Systems............... 42 . 1.17.8 Flightcrew Procedures ....................! . 44 2 . Analysis ............................ 3. Conclusioris .......................... 1 3.1 Findings ............................ 1 3.2 Probable Cause ......................... 1 4 . Safety Recommendations .................... 70 Appendixes ........................... 74 .. Appendix C.. Aircraft Information ................ 76 Appendix D.. ISreckage Diagram ................. 77 Appendix E.. Pertinent Airworthiness Regulations .......... Appendix F.. Applicable Airworthiness Directives .......... 86 . Appendix G.. Suspension and Kestoratioll of DC-10 Type Certificate . 89 . Appendix H.. DFDR Readout ................... 98 NATIONAL TRANSPORTATION SA.FETY BOARD WASHINGTON, D.C. 20594 AI3CRAFT ACCIDENT KEPORT Adopted: December 21,1979 AMERICAN AIRLINES, INC. DC-10-10, NIIOAA CHICAGO-O'HARE 1NTEKNATIONAL AIRPORT CHICAGO, ILLINOIS MAY 25, 1979 SYNOPSIS About 1504 c.d.t., May 25, 1979, American Airlines, Inc., Flight 191, a McDonneU-Douglas DC-10-10 aircraft, crashed into an open field just short of a trailer park about 4,600 It northwest of the departure end of runway 32R at Chicago-O'Hare International Airport, Illinois. ', Flight 191 was taking off from runway 32H. The weqher was clear and the visibility was 15 miles. During the takeoff rotation, Me left engine and pylon assembly and about 3 ft of the Icading edge of the left wing separated from the aircraft and fell to the runway. Fhght 191 continued to climb to about 325 ft above the ground and then began to roll to the left. The aircraft continued to roll to the left until the wings were past the vertical position, and during the roll, the ~. , aircraft's nose pitched down below the horizon. Flight 191 crashed into the open field and the wreckage scattered into an adjacent trailer park. The airet'aft was destroyed in the crash and subsequent fire. Two hundred and seventy-one persons on board Flight 191 were killea two persons on the ground were killed, and two others were injured. An old aircraft '* hangar, several automobiles, and a mobile home were destroyed. The National Transportation Safety Board determines that the probable .. cause of this accident was the asymmetrical stall and the ensuing roll of the aircraft because of the uncommanded retraction of the left wing outboard leading edge slats and the loss of stall warning and slat disagreement indication systems resultingfrom mnintenance-induced damage leading to the separation of the No. 1 engine and pylon assembly at a critical point during takeoff. The separation resulted from damage by improper maintenance procedures which led to failure of the pylon structure. Contributing to the-cause of the accident were the vulnerability of the design of the pylon attach points to maintenance damage; the vulnerability of the design of the leading edge slat system to the damage which produced asymmetry; deficiencies in Federal Aviation Administration surveillance and reporting systems which failed to detect and prevent the use of improper maintenance procedures; deficiencies in the practices and communications among the operators, the manufacturer, and the FAA which failed to determine and disseminate the particulars regarding previous maintenance damage incidents; and the intolerance of prescribed operational procedures to this unique emergency. -2- 1. FACTUAL INFORMATION 1.1 History of the Flight At 1459 c.d.t.,- 11 May 25, 1979, American Airlines, Inc., Flight 191, a McDonnell-Douglas DC-10 series 10 aircraft (DC-10-10) (NLIOAA), taxied from the gate at ChicagwO'llare International Airport, Illinois. Flight 191, M regulnrly I scheduled passeoiger flight, was en route to Los Angeles, Californie, with 258 passengers and 13 crewmembers on board. Rlaintenance personncl who monitored the flight's engine start, push-beck, and start of taxi did not observe anything out of the ordinary. The weather at the time of departure was clear, and the reported surface wind was 020"at 22 kns. Flight 191 was cleared to taxi to runway 32 right (32K) for takeoff. The company's Takeoff Data Card showed that the stabilizer trim setting was So aircraft noseup, the takeoff Gap setting was loo, (ind the takeoff gross weight was-379,000 lbs. The target low-pressure compressor (N ) rpm setting was 99.4 percent, critical engine failure speed (V ) was 139 ',k& indicated airspeed (KIAS), rotation speed (VK) was 145 KIM, and takeoff safety speed (V,) was 153