UNITED STATES AIR FORCE AIRCRAFT ACCIDENT INVESTIGATION BOARD REPORT KC-10A, T/N 83-0080 9TH AIR REFUELING SQUADRON 60TH AIR MOBILITY WING TRAVIS AIR FORCE BASE, CALIFORNIA LOCATION: NEAR MOUNTAIN HOME AFB, IDAHO DATE OF ACCIDENT: 1 NOVEMBER 2016 BOARD PRESIDENT: COL PERRY M. LONG III Conducted IAW Air Force Instruction 51-503 ACTION OF THE CONVENING AUTHORITY 1 0 JUL 2117 The report of the accident investigation board, conducted under the provisions of AFI 51-503, that investigated the 1 November 2016 mishap that occurred near Mountain Home Air Force Base, Idaho, involving KC-10A, T/N 83-0080, assigned to the 60th Air Mobility Wing, Travis Air Force Base, California, complies with applicable regulatory and statutory guidance and on that basis is approved. \\signed\\ fHOMA^J; Major General, U| Vice Commander United States Air Force Accident Investigation Board Report Class A Mishap, Near Mountain Home AFB, ID EXECUTIVE SUMMARY UNITED STATES AIR FORCE AIRCRAFT ACCIDENT INVESTIGATION KC-10A, T/N 83-0080 NEAR MOUNTAIN HOME AFB, IDAHO 1 NOVEMBER 2016 On 1 November 2016, at 1546 hours Zulu time (Z), a United States Air Force KC-10A Extender, tail number 83-0080, the mishap aircraft, assigned to the 60th Air Mobility Wing, departed from its home station of Travis Air Force Base (AFB), California, on a training mission in support of two flights of F-15s and a C-17. The scheduled flight profile was a formation departure from Travis AFB, refueling for approximately one hour with the F-15s, refueling training for approximately 1 hour 15 minutes with the C-17, and approximately one half hour of approach training before landing at Travis AFB. The mishap crew (MC) is assigned to the 9th Air Refueling Squadron, Travis AFB. At 1632Z, the MC prepared for aerial refueling (AR), and the mishap boom operator (MB) lowered the Aerial Refueling Boom (boom). Immediately after lowering the boom, it began to move erratically, oscillating to the aircraft’s right and left in a U-shaped pattern, well outside of its structural limits. After oscillating for approximately two minutes, the boom hoist cable broke. Approximately two minutes later, the gimbal separated from the A-frame gimbal mounts, but remained connected to the fuselage by hydraulic and electrical lines. At 1705Z, the boom completely separated from the aircraft and fell in an open field in Idaho. There were no injuries or fatalities reported with any portion of the mishap. After the boom separated, the MC landed the aircraft at Mountain Home AFB, Idaho without incident. The total monetary value of government loss was $6,529,845.71. The AIB president found, by a preponderance of the evidence, two causes for this mishap. The first cause of this mishap was a sheared Dual Rotary Voltage Transducer (DRVT) rotary crank that resulted from DRVT rotary bearing misalignment. This provided the aircraft’s boom control unit (BCU) with continuous, inaccurate roll position indications. As a result, the BCU compensated with lateral movement commands in both directions, driving the boom beyond its operational and structural limits. The second cause, related to the first, was the MB’s failure to turn off the boom flight control switch in a timely manner. Turning off this switch would have disabled the BCU. This would have neutralized the boom flight control surfaces, and prevented the boom from departing the aircraft. Additionally, the AIB president found, by a preponderance of the evidence, that the failure of maintenance personnel to comply with technical orders prevented the possible detection of an erratically performing D RVT, substantially contributing to the mishap. Under 10 U.S.C. § 2254(d) the opinion of the accident investigator as to the cause of, or the factors contributing to, the accident set forth in the accident investigation report, if any, may not be considered as evidence in any civil or criminal proceeding arising from the accident, nor may such information be considered an admission of liability of the United States or by any person referred to in those conclusions or statements. United States Air Force Accident Investigation Board Report Class A Mishap, Near Mountain Home AFB, ID SUMMARY OF FACTS AND STATEMENT OF OPINION KC-10A, T/N 83-0080 1 NOVEMBER 2016 TABLE OF CONTENTS ACRONYMS AND ABBREVIATIONS ...................................................................................... iii SUMMARY OF FACTS ................................................................................................................. 1 1. AUTHORITY AND PURPOSE ........................................................................................... 1 a. Authority ......................................................................................................................... 1 b. Purpose ............................................................................................................................ 1 2. ACCIDENT SUMMARY ..................................................................................................... 1 3. BACKGROUND .................................................................................................................. 2 a. Air Mobility Command ................................................................................................... 2 b. 60th Air Mobility Wing .................................................................................................. 2 c. 9th Air Refueling Squadron............................................................................................. 3 d. 660th Aircraft Maintenance Squadron ............................................................................ 3 e. 60th Maintenance Squadron ............................................................................................ 3 f. KC-10A “Extender” ......................................................................................................... 4 4. SEQUENCE OF EVENTS.................................................................................................... 4 a. Mission ............................................................................................................................ 4 b. Planning .......................................................................................................................... 4 c. Preflight ........................................................................................................................... 4 d. Summary of Accident ..................................................................................................... 5 e. Impact .............................................................................................................................. 7 f. Egress and Aircrew Flight Equipment ............................................................................. 7 g. Search and Rescue........................................................................................................... 7 h. Recovery of Remains ...................................................................................................... 7 5. MAINTENANCE ................................................................................................................. 8 a. Unscheduled Maintenance .............................................................................................. 8 b. Inspections .................................................................................................................... 10 c. Maintenance Procedures ................................................................................................ 10 d. Forms Documentation ................................................................................................... 11 e. Maintenance Personnel and Supervision ....................................................................... 12 f. Fuel, Hydraulic, Oil, and Oxygen Inspection Analyses ................................................. 12 6. AIRFRAME SYSTEMS ..................................................................................................... 12 a. Normal Operation of the Boom ................................................................................... 12 b. KC-10 Boom Normal Flight Procedures ..................................................................... 16 c. Structures and Systems post-mishap: Evaluation and Analysis .................................. 17 (1) Gimbal and Yoke Assembly with the Dual Rotary Voltage Transducer ............... 18 (2) Boom Control Unit ................................................................................................ 20 (3) Boom Control Assembly ....................................................................................... 20 7. WEATHER ......................................................................................................................... 23 a. Forecast Weather ........................................................................................................... 23 KC-10A, T/N 83-0080, 1 November 2016 i United States Air Force Accident Investigation Board Report Class A Mishap, Near Mountain Home AFB, ID b. Observed Weather ......................................................................................................... 24 c. Space Environment ........................................................................................................ 24 d. Operations ..................................................................................................................... 24 8. CREW QUALIFICATIONS ..............................................................................................