Thunderbird Crash Colorado Springs (2nd June, 2016)
Introduction
A Thunderbird jet F-16CJ, tail number 92-3890 was crashed on 2nd June 2016 at 1 pm local time after the pilot of the jet got ejected at approximately 5 miles south of Peterson AFB (Air Force Base). The Jet's pilot ejected safely at 13:00L and got some minor injuries but no other casualties and damage to the property of the civilians were reported. Exactly 8 seconds after the pilot got ejected from the aircraft, it impacted the ground. The aircraft having the value of US dollars 29,466,037 was destroyed in the accident which was a huge government loss. The clean-up costs of the environment initially were around US dollars 2181.22.
The thunderbird flight had six F-16CJs. The aircraft's mission was to perform a flyover for the graduation ceremony of the Air Force Academy where president Obama and Air Force Academy Cadets were present and then return to the Peterson AFB. As a part of preflight checkups, it is required that the throttle cutoff release is checked by the pilot. According to throttle cutoff release check also, it is instructed that the throttle is rotated fully outboard by the pilot and then the throttle must be pulled back to the cutoff position without pressing the trigger of the throttle. In the case of any issues, the throttle is to be left in the cutoff position by the pilot and the maintenance is to be notified.
Summary of the Accident
The Flight had to start from Peterson AFB for the flyover and due to longer graduation ceremonies, it was delayed on the ground and hence the fuel consumed was negligible. After the flyby, the air-show went safely and after that, the aircraft was prepared for landing by the pilot when it had around 1000 pounds of fuel left. The pilot then moved the throttle initially to the cutoff position at 12:59:38L as reported by the DAS (Data Acquisition System). Prior to the movement of the throttle initially to the cutoff position, it was positioned at a level above engine cutoff i.e. idle position for around 15 seconds.
Normally, the full rotation of the throttle cannot happen until and unless it's trigger is pressed. But, accidently the trigger remained stuck in the actuated position. When the throttle was placed initially in the cutoff position, the energy state of the aircraft was too low that engine could not be restarted before the ground impact. Normally, between an altitude of 4000 feet and 10000 feet, the aircraft can be restarted before the minimum altitude recommended for ejection. The aircraft at this point was at such a low energy that even it could not move to the runway. The pilot tried to restart the engine at 12:59:44L. He then radioed on the inter-flight frequency that he was experiencing some problem.
The Emergency Power Units (EPU) got activated automatically at 12:59:47L and the aircraft got hydraulic pressure and electrical power enough to run its flight controls. The Jet Fuel Starters were activated by the pilot at 12:59:52L which provided more airflow so that aircraft could be started. But, at 12:59:53L Turner, the pilot radioed on the radio frequency of the Peterson AFB that the engine had been switched off and on and that he was taking it away from the civilian area and then getting out. Since the aircraft was at low altitude, the engine restart procedure could not work. According to Air Combat Command, there were no reasons of low fuel levels when the aircraft crashed as it had 900 pounds of fuel when it touched the ground.
The accident investigation report indicated that in the trigger of the throttle, debris had been accumulated and had worn on the assembly of the trigger as well. It was stated in the report that the malfunction happened because of the metallic wear on the trigger and also its movement was restricted because of the debris that was gathered there due to the presence of the lubricant.
Nothing wrong on the part of the pilot was found in the accident investigation report and he was lauded for his actions as he brought the plane down in open fields at the cost of delaying his ejection. The main contributing factor was the issue in maintenance technical orders that did not have sufficient details that the problem in the trigger of the throttle could be identified. According to the report " Historic throttle trigger sticking in F-16s was identified,”. Since the throttle was stuck in its position, the engine cut off and lost thrust immediately.
Recommendations
According to Maj. A.J. Schrag, the build-up of the debris has been described as a 'maintenance issue'. The aircraft's preflight inspection was carried out just before two days of the flight and no red flag was raised by them. It has been recommended by the investigation team that possible changes should be made to the maintenance procedures as right now there are no instructions for the pilots to swab the trigger of the throttle before each flight which should be made a mandatory step. Certain mechanical and hardware changes should also be made in the future.
Accident Investigation team also pointed out that in all the maintenance procedures: Aircraft forms and documentation, Inspections, maintenance personnel and supervision, Fuel, Hydraulic, and oil inspection analysis, and Unscheduled maintenance, it was mentioned that the aerospace vehicle was safe for flight and no red flag was raised was them. The issues in maintenance procedures led to such huge loss of the government and it is therefore recommended in future that all the maintenance procedures are carried out properly and any issue whether hardware or software should be highlighted before the actual flight.
References
Kamp, B. J. (2016). United States Air Force Aircraft Accident Invetigation Board Report . EL Paso County: Department of the Air Force.
Paul, J. (2016, December 14). Thunderbirds jet crash near Colorado Springs was caused by malfunction that led to engine shut off, report says. Retrieved from The Denver Post: http://www.denverpost.com/2016/12/14/thunderbirds-crash-cause-colorado-springs/
Pawlyk, O. (2016). Faulty Throttle Contributed to Thunderbirds Crash: Report. Colorado: Military.com.
