FlightFollowerPilot’s Delayed Decision Making | Ends up crashing near Runway
The Engine Problem Was Intermittent — Until It Wasn't
Pilatus PC-12 N477SS departed Dallas-Fort Worth on April 23, 2020, when the pilot almost immediately reported losing engine power.
The official record
This occurrence was investigated by the National Transportation Safety Board under accident number CEN20LA159. The Board records the event as occurring on 23 April 2020 at Mesquite, TX. The aircraft is identified as a Pilatus PC12, registration N477SS. The highest injury level recorded is serious.
The Board’s record additionally lists phase of flight recorded as enroute; emergencydescent, weather conditions recorded as Visual (VMC); Visual (VMC), operating under 091.
The investigation is closed. The Board determined the probable cause to be:
The loss of engine power due to a mis-rigged beta control cable (propeller reversing cable), which resulted in a loss of thrust inflight.
NTSB, accident CEN20LA159
A probable cause is the Board’s determination of what brought the occurrence about. It is reached after the investigation closes and supersedes any earlier account, including contemporary reporting and anything inferred from the recording alone.
The full record can be retrieved from the NTSB’s public case system, CAROL, by searching accident number CEN20LA159.
Research and reconstruction
Flight Follower Editorial Team
This reconstruction was researched from official investigation records where they exist, the original air traffic control recording, and contemporary reporting. The aircraft movement, timeline and written account were assembled independently by Flight Follower. Where an investigation is open or no probable cause has been published, the account says so rather than offering one.
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Accident Facts
- Date
- 23 April 2020
- Aircraft
- Pilatus PC-12, N477SS
- Location
- Near Mesquite, Texas
- Operation
- Part 91 positioning flight
- Outcome
- Pilot seriously injured; aircraft substantially damaged
- Investigation
- NTSB CEN20LA159
The pilot accepted vectors toward Rockwall. Then the power appeared to stabilize. That changed the decision: instead of continuing to the diversion airport, the pilot asked to return toward DFW.
Moments later the power deteriorated again. The pilot requested the diversion airport once more. ATC identified another airport about three miles away.
The problem was now no longer a temporary power fluctuation. The aircraft had to reach a runway while its engine condition remained uncertain.
The Maintenance Record Explained the Intermittent Behavior
Maintenance had been performed on the airplane the same day to address difficulty moving the Power Control Lever into reverse. Mechanics found severe binding in the beta control cable and cleaned, reinstalled and rigged the cable.
The postaccident examination found the beta control cable mis-rigged and the propeller blades in the feathered position. The beta valve plunger was extended beyond the expected position, consistent with a condition that could interrupt oil flow to the constant-speed unit.
That evidence changed the character of the event. The aircraft had not suffered an unexplained engine failure. The engine-power loss was associated with the propeller-control system.
The 360-Degree Turn Consumed the Remaining Margin
The pilot was already close to the diversion airport. But the aircraft was too high to immediately establish the desired left-base profile, so the pilot planned a 360-degree turn to lose altitude.
During that turn the engine lost all power. The runway that had been three miles away was no longer reachable.
This is the key decision-making point. A maneuver that would normally be harmless during a stable approach becomes hazardous when the aircraft's propulsion is intermittent. The safest plan has to account for the possibility that the power will disappear again before the maneuver is complete.
What the Records Show
the reconstruction source identifies the probable cause as loss of engine power due to a mis-rigged beta control cable, resulting in loss of thrust in flight.
The NTSB investigation record is CEN20LA159.
Why This Incident Matters
Intermittent failures are particularly dangerous because they invite the pilot to believe the emergency has ended. When the engine recovers, returning to the original plan can feel reasonable.
But the first power loss is already evidence that the system is not trustworthy. The PC-12 accident shows the importance of treating intermittent thrust as a continuing emergency until the aircraft is safely on the ground.
The maintenance history also demonstrates why work on flight-critical control systems requires verification beyond the initial rigging check.
Evidence and Findings
The cockpit sequence explains the operational problem. The pilot initially believed the engine power loss was stabilizing and requested to return toward DFW. That decision was reversed when the power deteriorated again. The aircraft then diverted toward Mesquite.
At roughly 4,500 feet, the pilot planned a 360-degree turn to lose altitude. During the outbound portion of that turn, total power was lost. The aircraft could not reach the runway and struck a field short of the airport.
The accident therefore illustrates why intermittent engine problems deserve the same seriousness as total failures. The temporary return of power did not mean the aircraft was healthy. The maintenance evidence shows that the underlying control problem remained.
What Could Have Broken the Chain
The first barrier was the maintenance inspection. Severe binding had been found in the beta control cable before departure, yet the aircraft returned to service. A later verification of the complete control path might have exposed the mis-rigging before flight.
The second barrier was the first engine-power loss. Once power appeared to recover, the pilot chose to return toward DFW. A more conservative response would have been to continue toward the diversion airport while the aircraft's performance remained uncertain.
The final barrier was the 360-degree altitude-loss turn. Because the aircraft was close to the airport, reducing altitude through a long maneuver assumed that engine thrust would remain available. The subsequent total power loss removed that assumption.
Each point illustrates the same principle: a temporary recovery does not restore the safety margin that existed before the first failure.
The Final Safety Margin
The aircraft's proximity to Mesquite also illustrates the danger of using altitude as a substitute for reachability. Being high enough to see the airport does not mean every maneuver required to descend toward it is safe. A forced landing plan should preserve the shortest practical path to the runway when propulsion is uncertain.
- Intermittent power loss should be treated as a continuing emergency.
- A temporary recovery does not prove that the failure has been resolved.
- Avoid altitude-loss maneuvers that assume continued engine performance during an unstable power emergency.
- Maintenance on propeller-control systems must be verified carefully.
- A nearby runway is only useful if the aircraft can still reach it after the next failure.