GON
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Came across this article and thought to post.
It is common for people to put DEF into the diesel tank in error, often causing serious damage. This is the first time I have read that DEF was introduced into jet fuel, in error. Note this happened 27 months ago (not recent).
The investigation found that the refueler had erroneously deposited diesel exhaust fluid into the FSII tank of his fuel truck, which he subsequently used to refuel 5 airplanes, including the incident airplane.
N135SH GATES LEARJET 35A Page Arizona 23 APR 2023
4 POB - No Injuries
Pilot Flight Time:
PIC - 5606 hours (Total, all aircraft), 3975 hours (Total, this make and model)
Copilot - 1920 hours (Total, all aircraft), 190 hours (Total, this make and model)
On April 23, 2023, about 1729 Pacific daylight time, a Learjet 35A, N135SH, sustained an uncommanded decrease in power on both engines near Page, Arizona. The captain, first officer, and two medical crewmembers were not injured.
According to the captain, the flight was a non-patient MEDEVAC flight destined for Chicago, Illinois. The captain placed a fuel order before the flight with Signature Aviation at Harry Reid International Airport (LAS), Las Vegas, Nevada, that included PRIST, a FSII; he observed the attendant write “T/O +” on the paperwork that pertained to his fuel order. The airplane was subsequently refueled with 674 gallons of JET A fuel.
The airplane departed LAS at 1646 with the first officer flying and the captain monitoring the flight. They climbed to FL350 and accelerated to their cruise speed, which occurred about 19 minutes after takeoff. About 11 minutes later (30 minutes after departure), the captain observed erratic temperature indications between 0° and 750° from the left engine’s ITT gauge. The other engine indications were normal at the time. About 2 minutes later he observed small variations in the left engine’s ITT, followed by noticeable variations in fuel flow, as well as small variations in the right engine’s N1 (fan rotational speed) and N2 (turbine rotational speed). The captain reported that the right-engine variations became significant and resulted in “yaw issues”; according to the first officer, the right engine was “pulsing.”
The flight crew informed ATC that they wanted to return to LAS and the controller gave them instructions to make an immediate left turn. During this time the variations in the right engine’s parameters increased and right-engine power decreased to idle. A review of digital electronic engine control (DEEC) data showed that the right engine reduced to idle power at 1719 and subsequently began to show fluctuations in N1 and N2 without corresponding movement of the power lever beginning at 1720. The right engine returned to idle thrust at 1721 without a consistent movement of the power lever. The captain stated that about this time the right engine’s fuel flow indicator indicated 0 lbs/hr. They declared an emergency and informed ATC they were unable to maintain altitude and would have to descend. The controller gave them an immediate clearance to descend.
The DEEC data for the left engine showed fluctuations in N1 and N2 without a corresponding movement of the power lever beginning at 1717. The flight crew reported that the variations in the left engine’s parameters became more erratic as the airplane passed through FL300 at 1725. The captain observed a slow decay in the left-engine N1 at this time and noted that the engine was unresponsive to thrust lever movements. He also reported that an attempt to restart the right engine was unsuccessful. According to the first officer, the left engine also reduced to idle power at this time. At 1729, as the airplane passed through FL270, he advised the controller that they would make an emergency landing in Page, Arizona.
The captain dumped fuel to reduce the airplane’s landing weight, and the first officer started a circling descent. After they passed below 12,000 ft mean sea level, ATC cleared them for the visual approach to runway 15 at their destination airport. According to the first officer, after the captain secured the fuel jettison valves, the captain took over the flying duties. After the airplane was established on short final the captain lowered the landing gear at 220 KIAS. The captain noted that he was intentionally high and fast at this point, in order to perform a dead stick landing. At 1744, they touched down successfully at a slightly higher than normal speed and slightly long. The airplane came to rest about 650 ft from the runway end. The first officer noted that the left engine was still at idle and the right engine was off.
DEEC data showed the left-engine N2 between 50% and 60% for about 4 minutes, 23 seconds; about half of this time was before landing and the other half was after landing. In addition, after landing the ITT value dropped after the engine was shut down, when all the engine parameters decreased. According to the data, after the reduction in thrust to the right engine at 1719 until the end of the flight, the engine remained at an idle, sub-idle or non-operational condition and did not respond to pilot commands.
The investigation found that the refueler had erroneously deposited diesel exhaust fluid into the FSII tank of his fuel truck, which he subsequently used to refuel 5 airplanes, including the incident airplane. Crystalline deposits were discovered in the fuel tank.
Postaccident examination of the airframe and engines did not reveal contamination of the airframe filter elements; however, crystalline deposits began to appear on the elements about 5 months later. The reason for the latency was not determined. The rest of the fuel systems exhibited various quantities of crystalline deposits, with extensive formation at the fuel nozzles of both engines. The contamination at the nozzles would have interfered with the spray pattern of the affected nozzles, inhibiting their ability to atomize the fuel and resulting in the loss of power to both engines.
Probable Cause and Findings:
The fueler’s inadvertent addition of diesel exhaust fluid (DEF) to the FSII reservoir on the fuel truck, and its subsequent mixture with the JET A that was used to fuel the airplane, resulting in a total loss of power to the right engine and a partial loss of power to the left engine.
It is common for people to put DEF into the diesel tank in error, often causing serious damage. This is the first time I have read that DEF was introduced into jet fuel, in error. Note this happened 27 months ago (not recent).
The investigation found that the refueler had erroneously deposited diesel exhaust fluid into the FSII tank of his fuel truck, which he subsequently used to refuel 5 airplanes, including the incident airplane.
N135SH GATES LEARJET 35A Page Arizona 23 APR 2023
4 POB - No Injuries
Pilot Flight Time:
PIC - 5606 hours (Total, all aircraft), 3975 hours (Total, this make and model)
Copilot - 1920 hours (Total, all aircraft), 190 hours (Total, this make and model)
On April 23, 2023, about 1729 Pacific daylight time, a Learjet 35A, N135SH, sustained an uncommanded decrease in power on both engines near Page, Arizona. The captain, first officer, and two medical crewmembers were not injured.
According to the captain, the flight was a non-patient MEDEVAC flight destined for Chicago, Illinois. The captain placed a fuel order before the flight with Signature Aviation at Harry Reid International Airport (LAS), Las Vegas, Nevada, that included PRIST, a FSII; he observed the attendant write “T/O +” on the paperwork that pertained to his fuel order. The airplane was subsequently refueled with 674 gallons of JET A fuel.
The airplane departed LAS at 1646 with the first officer flying and the captain monitoring the flight. They climbed to FL350 and accelerated to their cruise speed, which occurred about 19 minutes after takeoff. About 11 minutes later (30 minutes after departure), the captain observed erratic temperature indications between 0° and 750° from the left engine’s ITT gauge. The other engine indications were normal at the time. About 2 minutes later he observed small variations in the left engine’s ITT, followed by noticeable variations in fuel flow, as well as small variations in the right engine’s N1 (fan rotational speed) and N2 (turbine rotational speed). The captain reported that the right-engine variations became significant and resulted in “yaw issues”; according to the first officer, the right engine was “pulsing.”
The flight crew informed ATC that they wanted to return to LAS and the controller gave them instructions to make an immediate left turn. During this time the variations in the right engine’s parameters increased and right-engine power decreased to idle. A review of digital electronic engine control (DEEC) data showed that the right engine reduced to idle power at 1719 and subsequently began to show fluctuations in N1 and N2 without corresponding movement of the power lever beginning at 1720. The right engine returned to idle thrust at 1721 without a consistent movement of the power lever. The captain stated that about this time the right engine’s fuel flow indicator indicated 0 lbs/hr. They declared an emergency and informed ATC they were unable to maintain altitude and would have to descend. The controller gave them an immediate clearance to descend.
The DEEC data for the left engine showed fluctuations in N1 and N2 without a corresponding movement of the power lever beginning at 1717. The flight crew reported that the variations in the left engine’s parameters became more erratic as the airplane passed through FL300 at 1725. The captain observed a slow decay in the left-engine N1 at this time and noted that the engine was unresponsive to thrust lever movements. He also reported that an attempt to restart the right engine was unsuccessful. According to the first officer, the left engine also reduced to idle power at this time. At 1729, as the airplane passed through FL270, he advised the controller that they would make an emergency landing in Page, Arizona.
The captain dumped fuel to reduce the airplane’s landing weight, and the first officer started a circling descent. After they passed below 12,000 ft mean sea level, ATC cleared them for the visual approach to runway 15 at their destination airport. According to the first officer, after the captain secured the fuel jettison valves, the captain took over the flying duties. After the airplane was established on short final the captain lowered the landing gear at 220 KIAS. The captain noted that he was intentionally high and fast at this point, in order to perform a dead stick landing. At 1744, they touched down successfully at a slightly higher than normal speed and slightly long. The airplane came to rest about 650 ft from the runway end. The first officer noted that the left engine was still at idle and the right engine was off.
DEEC data showed the left-engine N2 between 50% and 60% for about 4 minutes, 23 seconds; about half of this time was before landing and the other half was after landing. In addition, after landing the ITT value dropped after the engine was shut down, when all the engine parameters decreased. According to the data, after the reduction in thrust to the right engine at 1719 until the end of the flight, the engine remained at an idle, sub-idle or non-operational condition and did not respond to pilot commands.
The investigation found that the refueler had erroneously deposited diesel exhaust fluid into the FSII tank of his fuel truck, which he subsequently used to refuel 5 airplanes, including the incident airplane. Crystalline deposits were discovered in the fuel tank.
Postaccident examination of the airframe and engines did not reveal contamination of the airframe filter elements; however, crystalline deposits began to appear on the elements about 5 months later. The reason for the latency was not determined. The rest of the fuel systems exhibited various quantities of crystalline deposits, with extensive formation at the fuel nozzles of both engines. The contamination at the nozzles would have interfered with the spray pattern of the affected nozzles, inhibiting their ability to atomize the fuel and resulting in the loss of power to both engines.
Probable Cause and Findings:
The fueler’s inadvertent addition of diesel exhaust fluid (DEF) to the FSII reservoir on the fuel truck, and its subsequent mixture with the JET A that was used to fuel the airplane, resulting in a total loss of power to the right engine and a partial loss of power to the left engine.
