NTSB-AAR-72-18 TECHNICAL REPORT STANDARD Title PAGE
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SA-424 FILE NO. 1-0002 AIRCRAFT ACCIDENT REPORT WESTERN AIR LINES, INC. BOEING 720-047B,N3166 ONTARIO INTERNATIONAL AIRPORT ONTARIO, CALIFORNIA MARCH 31, 1971 ADOPTED: JUNE 7, 1972 NATIONAL TRANSPORTATION SAFETY BOARD Washington, 0. C. 20591 REPORT NUMBER: NTSB-AAR-72-18 TECHNICAL REPORT STANDARD TiTLE PAGE . Report No. 2.Government Accession No. 3.Recipient's Catalog No. NTSB-AAR-72-18 I. Title and Subtitle 5.Report Date Aircraft Accident Report - Western Air Lines, InC., Sune 7, 1972 Roeing 720-047B, N3166, Ontario International Airport, 6.Performing Organization Ontario. California, March 31, 1971 Code '. Author(s) 8.Performing Organization Report No. I. Performing Organization Name and Address IO.Work Unit No. Bureau of Aviation Safety 11 .Contract or Grant No. National Transportation Safety Board Washington, D. C. 20591 13.Type of Report and Period Covered 12.Sponsoring Agency Name and Address Aircraft Accident Report March 31, 1971 NATIONAL TRANSPORTATION SAFETY BOARD Washington, 0. C. 20591 14.Sponsoring Agency Code 15.Supplementary Notes I6.Abstract Flight 366, a Boeing 720B, on a proficiency check flight, yawed and rolled out of control, and crashed while in the process of executing a 3-engine missed- approach from a simulated engine-out ILS instrument approach. The five crew- members and only occupants died in the crash. The weather conditions at Ontario were 600 feet overcast, with 3/4-mile visibility in fog, haze, and smoke. The National Transportation Safety Board determines that the probable cause of this accident was the failure of the aircraft rudder hydraulic actuator support fitting. The failure of the fitting resulted in the inapparent loss Of left rudder control which, under the conditions of this flight, precluded the pilotk ability to maintain directional control during a simlated engine-out missed- approach. The existing weather conditions degraded external visual cues, thereby hampering rapid assessment of aircraft performance by the flight check Captain. 17. Key Words i8.Distribution Statement Descriptors: Aviation Accidents; Accident Investiga- tion; Instrument Approach, Asymmetric Thrust; Dihedral Effect; Sideslip-Roll Coupling Effect; Aircraft Simu- Released to the Public lators; Training Accident; Missed-Approach; FAA Air- Unlimited distribution worthiness Directives, Service Bulletins; Identifiers: Boeiw 720B 19.Security Classification 2O.Security Classification 21.No. of Pages 22.Price (of this report) (of this page) UNCLASSIFIED UNCLASSIFIED 41 NTSB Form 1765.2 (11/70) ii TABLE OF CONTENTS . Page Synopsis ........................... 1 1. Investigation ......................... 2 1.1 History of Flight ...................... 2 1.2 Injuries to Persons ...................... 4 1.3 Damage to Aircraft ..................... 4 1.4 Other Damage ........................ 4 1.5 Crew Information ...................... 4 1.6 Aircraft Information ..................... 4 1.7 Meteorological Information ................. 6 1.8 Aids to Navigation ...................... 7 1.9 Communications ....................... 7 1.10 Aerodrome and Ground Facilities .............. 7 1.11 Flight Recorders ...................... 8 1.12 Wreckage .......................... 8 1.13 Fire .......................... 10 1.14 Survival Aspects ....................... 10 1.15 Tests and Research ..................... 10 1.16 Other Information ..................... 15 2 . Analysis and Conclusions .................. 19 2.1 Analysis ........................... 19 2.2 Conclusions ......................... 26 [a) Findings ........................ 26 (b) Probable Cause ..................... 27 3 . Recommendations ..................... 27 Appendices Appendix A Investigation and Hearing ............. 31 Appendix B Flight Crew Information ............. 32 Appendix C Aircraft Information ............... 34 Attachments Attachment 1 Rudder Power Control Unit (Series Yaw Dunper) Attachment 2 Probable Flight Path Attachment 3 Wreckage Distribution ... u1 File No. 1-0002 NATIONAL TRANSPORTATION SAFETY BOARD Washington, D. C. 20591 AIRCRAFT ACCIDENT REPORT Adopted: June 7, 1972 WEfXERN AIR LINES, INC. BOEING 720-047B, N3166 ONTARIO lNTERNATIONAL AIRPORT ONTARIO, CALIFORNIA MARCH 31. 1971 SYNOPSIS visibility in fog, haze and smoke, wind from 250" at 4 knots, and a Runway 25 visual range A Western Air Lines, Inc., Boeing 720-047B, of more than 6,000 feet. Similar conditions were N3166, operating as Flight 366, crashed on the reported 34 minutes prior to the accident, Ontario International Airport, Ontario, Cali- except the ceiling and visibility were 500 feet fornia, at 0633:29 Pacific standard time, on and 5/8-mile, respectively. March ,31, 1971. All five crewmembers, the only Investigation revealed that the rudder hydrau- occupants of the aircraft, were fatally injured. lic actuator support fitting had failed, resulting The aircraft was completely destroyed by in the complete loss of left rudder control impact and ensuing fire. shortly after commencement of the missed- Flight 366, a routine proficiency check flight, approach. The fitting failed due to a combina- was executing an Instrument Landing System tion of stress-corrosion cracking and high tensile approach to Runway 25 at Ontario with the No. loading. 4 engine reduced to idle power to simulate an The National Transportation Safety Board engine-out approach. The flight had been cleared determines that the probable cause of this to land or to execute a missed-approach proce- accident was the failure of the aircraft rudder dure at the pilot-in-command's discretion. At hydraulic actuator support fitting. The failure of decision height, approximately 100 feet above the fitting resulted in the inapparent loss of left the runway, a simulated engine-out missed- rudder control which, under the conditions of approach procedure was initiated. The aircraft this flight, precluded the pilot$$ ability to began to climb and the landing gear was maintain directional control during a simulated retracted. The aircraft continued to climb to an engine-out missed-approach. The existing altitude of about 500 feet above the runway weather conditions degraded external visual while rotating to the right about its roll and yaw cues, thereby hampering rapid assessment of air- axes. As the rotation continued, the nose of the craft performance by the flight check captain. aircraft descended to a near-vertical downward Based on evidence gathered in the initial position, and the aircraft crashed on a south- investigation of the accident, the Safety Board easterly heading approximately 3,140 feet west recommended to the Federal Aviation Admini- of the approach end and 420 feet north of the stration on April 9, 1971, that: (1) The inspec- centerline of Runway 25. tion time periods associated with the rudder The weather at Ontario about 3 minutes after hydraulic actuator support fittings on the accident was: 600 feet overcast, 3/4-mile B-707/720 aircraft be reevaluated, and (2) all , 1 7 B-707/720 operators be informed of the po- 1. INVESTIGATION W. tential operational hazards associated with low CO altitude, high-asymmetric thrust operations. 1.1 History crfFlight CC The FAA responded to these recommenda- Western Air Lines, Inc., Flight 366 (WAL ta tions by: (1) issuing a new Airworthiness Direc- 366), a Boeing 720-047B, N3166, was scheduled tive, on April 27, 1971, requiring more frequent re on March 31, 1971, as a training flight for the CI inspections of the support fitting, and (2) issuing purpose of administering proficiency flight an Operational Alert Notice on April 9, 1971, (1 checks to two Western captains. The crew con- th informing all B-707/720 operators of the fitting sisted of: (1) a check captain (the pilot-in-com- failures and advising that simulated engine ax mand), seated in the right-hand pilot seat, per- as failures not be performed at low altitudes until forming first officer duties, (2) a captain seated certain conditions had been met. fe in the left-hand pilot seat, flying the aircraft and fc After further inquiry into the support fitting receiving a proficiency check, and (3) a second S€ problem, Safety Board consultations with the officer performing flight engineer duties. Seated manufacturer and the FAA resulted in the es rz behind the left-hand pilot's seat on two tandem a1 tablishment of an earlier support fitting replace- jump seats were a captain who was to receive a ment (or modification) date. This was con- rt proficiency check later in the flight and a 11 sidered necessary to further reduce the possibili- captain who joined the crew shortly prior to ties of in-flight failures of the fitting. cl departure to observe flight check procedures. C Based on the evidence gathered in the inquiry, The check captain received a flight briefing the Safety Board further recommended to the tl from the Western flight dispatcher at 0520' on FAA that: (1)there is a need for more definitive tl the morning of the flight. The briefing included I< information or warnings in Airworthiness Direc- weather reports and forecasts, weight and w tives; (2) improvements are needed in pilot train- balance data, Notices to Airmen, fuel load, and w ing programs; (3) simulated engine($-out manu- clearance information. An Instrument Flight C evers be performed, to the maximum extent pos- had been filed with the Rules (IFR) flight plan a sible, either in flight simulators or at altitudes Los Angeles Air Traffic Control Center request- e that will insure safety if unexcpected aircraft ing clearance from Los Angeles International S