Winter almost upon us. Interesting article and a timely reminder.
When Luck Fails: A Commander Comes To Grief
Feb 26, 2018.
Richard N. Aarons | Business & Commercial Aviation
This article appears in the March 2018 issue of Business & Commercial Aviation with the title - “When Luck Fails.”
Students of air safety investigation know that most accidents and incidents arise from a series ofsmall events that slip unnoticed into the timeline rather than one catastrophic occurrence. Small mechanical stresses grow into large system failures; cockpit workload gradually increases until thecrew falls behind the situation; and, sometimes, luck (good or bad) enters the equation and skews the outcome.
All of these elements seem to have played roles in the loss of a Gulfstream Commander 690C (N840V)
on Feb. 3, 2014, about 1655 CST. The 62-year-old private pilot and three passengers were killed and
the airplane destroyed when it crashed while on approach to the John C. Tune Airport (KJWN) near
Nashville, Tennessee.
Ultimately, the NTSB determined the probable cause of this accident was: “The pilot’s failure to
maintain airspeed with one engine inoperative, which resulted in a loss of control while on approach.
Contributing to the accident were airframe ice accumulation due to conditions conducive to icing and
the loss of engine power on one engine.”
The businessman owner-pilot held ratings for airplane single- and multiengine land, and instrument.
His logbook was not located, but training and medical records indicate he had accumulated over
3,000 hr., including about 1,400 in multiengine airplanes, 450 hr. instrument time and 720 hr. in the
accident airplane. He held a third-class medical and post-mortem toxicological screening showed no
abnormalities. All airplane occupants died of blunt force trauma.
The Flight
On the day of the accident, the pilot flew the airplane from the Clarence E. Page Municipal Airport
(KRCE), Oklahoma City, where it had undergone maintenance including a 150-hr. periodic inspection,
to its home base at Great Bend, Kansas, Municipal Airport (KGBD). His passengers then boarded and
the airplane departed at about 1445 on an IFR flight plan to Nashville. The businessmen had planned
to attend a trade show in the area.
The flight to the Nashville area was uneventful and, as the Commander neared the destination at
1628, the controller cleared the pilot to execute a GPS (RNAV) approach to Runway 2 at KJWN.
Shortly thereafter, the pilot informed the controller that he needed to review the approach procedure
before continuing the approach. The controller acknowledged, and, after the pilot reported that he
was ready to proceed with the approach, the controller again issued clearance for the GPS approach.
Radar data showed that, during the approach, the airplane tracked a course that was offset about a
half mile right of the final approach course until it was about 1 mi. from the runway threshold. The
airplane then turned left toward the threshold and descended to an altitude of about 145 ft. AGL over
the runway threshold before the pilot performed a missed approach. “It is likely,” said the Safety
Board, “that the pilot performed the missed approach because he was unable to align the airplane
with the runway before it crossed the threshold.”
The controller provided radar vectors for the airplane to return to the approach course and cleared
the pilot a third time for the GPS approach to the runway. Radar data showed that the airplane was
established on the final approach course as it passed the initial approach fix; however, before it
reached the final approach fix, its airspeed slowed to about 111 kt., and it began a left turn with a 25-
deg. bank angle. About 18 sec. later, while still in the turn, the airplane slowed to 108 kt. and began
descending rapidly. The airplane’s rate of descent exceeded 10,000 ft. per minute, and it crashed into
trees and then the ground.
The impact created a crater that was 11-ft. long, 11 ft. wide, and 6 ft. deep. Broken tree branches that
contained 45-deg. angled cuts were observed at a height of about 50 ft. Investigators determined the
airplane impacted the ground at an approximate 70-deg. angle, consistent with being in an inverted
position. It was severely fragmented with debris scattered on a course of about 320 deg., for about
450 ft.
A post-crash fire consumed a majority of the airframe. Fragmentation of the wreckage precluded the
ability to confirm control continuity to the respective flight control surfaces. And as a result of impact
damage to the cockpit, Safety Board investigators could not determine the positions of ice protection
system switches at the time of the accident. Portions of the deice boot system were observed on wing
debris and portions of the horizontal stabilizer. The boots were destroyed by impact forces and fire.
Both propellers remained attached to their respective gearboxes, which had separated from their
respective engines. All three left propeller blades separated from the hub. Two right propeller blades
remained attached to the hub, and one blade had separated. Both propeller assemblies were severely
damaged and displayed evidence of rotational scoring; however, the right propeller blades displayed
a significantly greater degree of rotational scoring, tears and missing blade tips than the left blades.
Both engines had been damaged by impact and fire. Their respective fuel pumps and fuel control
units were separated. A subsequent teardown examination of the engines revealed no pre-impact
conditions that would have prevented normal operation. However, type and degree of damage to the
left engine was indicative of an engine that was not operating, with rotation consistent with a
windmilling propeller at the time of impact. Static impact marks were observed on the first and
second stage centrifugal compressor shrouds and no evidence of rotational scoring was noted on the
turbine section.
The type and degree of damage to the right engine was indicative of an engine that was operating
under power at the time of impact. Rotational scoring was observed on the first and second stage
centrifugal compressor shrouds and the first-, second- and third-stage turbine shroud. Almost all of
the vanes on the first-stage centrifugal compressor impellers were deformed and or separated. In
addition, the forward curvic coupling of the second-stage centrifugal compressor impeller was
heavily smeared.
The left engine fuel control unit was extensively damaged and could not be functionally tested.
Disassembly revealed no evidence of pre-impact malfunctions.
CAT scans of the left- and right-engine fuel shutoff valves revealed that they were both in the closed
position; however, their respective pre-impact position could not be confirmed. Teardown of the
valves revealed no evidence of any pre-impact failures. The left-engine fuel shutoff valve solenoids
could be opened and closed by applying electrical power directly to the solenoids. The right-engine
fuel shutoff valve solenoids did not function when electrical power was applied.
Examination of a vertical and directional gyro recovered from the wreckage was performed by the
NTSB Materials Laboratory. Despite impact and fire damage, tests revealed that VG and DG internal
damage was consistent with rotation at the time of the accident.
Ice
Safety Board specialists determined weather conditions present at the location and time of the
accident were conducive to supercooled liquid water droplets, and the airplane likely encountered
moderate or greater icing conditions. Several pilot reports (PIREPs) for moderate, light, trace and
negative icing were reported to ATC but were not distributed publicly into the National Airspace
System, and there was no Airmen’s Meteorological Information (AIRMET) issued for icing.
The type and degree of damage to the left engine was indicative of an engine that was not
operating, with rotation consistent with a windmilling propeller at the time of impact.
Investigators said the pilot had received standard and abbreviated weather briefings for the flight,
and his most recent weather briefing included three PIREPs for icing conditions in the area of the
accident site.
“Given the weather information provided,” said the Safety Board, “the pilot should have known icing
conditions were possible. Even so, the public distribution of additional PIREPs would have likely
increased the weather situational awareness by the pilot, weather forecasters and air traffic
controllers.”
The airplane’s deicing and anti-icing systems included wing and empennage deice boots and engine
inlet heaters. As noted, the position of the switches for the ice protection systems at the time of the
accident could not be determined.
In an analysis of the accident, investigators commented, “Although the airplane’s airspeed of 108 kt.
when the steep descent began was above its published stall speed of 77 kt., both bank angle and ice
accretion would have increased the stall speed. In addition, the published minimum control airspeed
was 93 kt. It is likely that, after the airplane passed the initial approach fix, the left engine lost power,
the airplane’s airspeed began to decay, and the asymmetric thrust resulted in a left turn. As the
airspeed continued to decay, it decreased below either stall speed or minimum control airspeed, and
the airplane entered an uncontrolled descent.”
Safety Board investigators examined both the maintenance history and ice-certification history of the
airplane. The high-wing, twin executive turboprop was manufactured in 1982. It was powered by
two Executive Wings Inc. STC-modified Garrett TPE331-5-511K 715-hp engines, equipped with
Hartzell three-blade constant-speed propeller assemblies.
According to maintenance records, the airplane’s most recent inspection was a 150-hr. periodic
inspection, which was performed on Feb. 1 — two days before the accident. At the time of the crash,
the airframe and both engines had been operated for about 4,460 total hours since new. The airplane
had been operated for about 70 hr. during the 13 months that preceded the accident.
According to the pilot operating handbook, the Commander 690C’s anti-icing system included heated
stall warning, rudder horn anti-ice, rudder tab anti-ice, generator inlet anti-ice, electrically heated
windshield and pitot-static heaters. The systems were designed to prevent ice accumulation and
were to be placed in operation prior to entering flight conditions conducive to ice formation. Engine
inlet heaters utilized hot engine compressor bleed air to prevent icing. The ice protection systems
were controlled by switches in the “ICE PROTECTION” group of the cockpit overhead switch panel.
The following warning, said the NTSB, was included under the Engine Inlet Anti-Ice Systems:
“Warning: When icing conditions may be encountered, do not delay operation of the engine inlet heat
systems. Turn the systems on before any ice accumulates. Engine inlet heat must be on if icing
conditions exist or are anticipated.”
The airplane was also equipped with a Negative Torque Sensing (NTS) system that was designed to
reduce drag caused by a windmilling propeller in the event of a loss of engine power by moving the
blades toward the feathered position to reduce drag and yaw.
Honeywell Operating Information Letter OI331-11R11, issued Sept. 16, 2013, emphasized proper use
of engine inlet anti-ice and provided additional information on the use of engine ignition in icing
conditions. The operating letter stated in part that engine inlet anti-ice should be used during all
flight in potential icing conditions and icing conditions should be considered to exist when flying in
precipitation or visible moisture (including clouds or fog) with an outside air temperature 10C or
50F, or colder. In addition, it stated, “If the use of anti-ice is inadvertently delayed after encountering
icing conditioning, ice may accumulate on engine and airframe inlet surfaces. In such instances,
subsequent application of engine inlet anti-ice can cause ice shedding and ingestion, which may
cause flameout. . . .”
So, in this case, it would seem that all the tolerances lined up unidirectionally. An airplane just out of
maintenance, only flown occasionally, susceptible to icing challenges, operating into an unfamiliar
destination in the face of what might be considered under reported mixed icing conditions came to
grief.
Those circumstances are worth thinking about.
When Luck Fails: A Commander Comes To Grief
Feb 26, 2018.
Richard N. Aarons | Business & Commercial Aviation
This article appears in the March 2018 issue of Business & Commercial Aviation with the title - “When Luck Fails.”
Students of air safety investigation know that most accidents and incidents arise from a series ofsmall events that slip unnoticed into the timeline rather than one catastrophic occurrence. Small mechanical stresses grow into large system failures; cockpit workload gradually increases until thecrew falls behind the situation; and, sometimes, luck (good or bad) enters the equation and skews the outcome.
All of these elements seem to have played roles in the loss of a Gulfstream Commander 690C (N840V)
on Feb. 3, 2014, about 1655 CST. The 62-year-old private pilot and three passengers were killed and
the airplane destroyed when it crashed while on approach to the John C. Tune Airport (KJWN) near
Nashville, Tennessee.
Ultimately, the NTSB determined the probable cause of this accident was: “The pilot’s failure to
maintain airspeed with one engine inoperative, which resulted in a loss of control while on approach.
Contributing to the accident were airframe ice accumulation due to conditions conducive to icing and
the loss of engine power on one engine.”
The businessman owner-pilot held ratings for airplane single- and multiengine land, and instrument.
His logbook was not located, but training and medical records indicate he had accumulated over
3,000 hr., including about 1,400 in multiengine airplanes, 450 hr. instrument time and 720 hr. in the
accident airplane. He held a third-class medical and post-mortem toxicological screening showed no
abnormalities. All airplane occupants died of blunt force trauma.
The Flight
On the day of the accident, the pilot flew the airplane from the Clarence E. Page Municipal Airport
(KRCE), Oklahoma City, where it had undergone maintenance including a 150-hr. periodic inspection,
to its home base at Great Bend, Kansas, Municipal Airport (KGBD). His passengers then boarded and
the airplane departed at about 1445 on an IFR flight plan to Nashville. The businessmen had planned
to attend a trade show in the area.
The flight to the Nashville area was uneventful and, as the Commander neared the destination at
1628, the controller cleared the pilot to execute a GPS (RNAV) approach to Runway 2 at KJWN.
Shortly thereafter, the pilot informed the controller that he needed to review the approach procedure
before continuing the approach. The controller acknowledged, and, after the pilot reported that he
was ready to proceed with the approach, the controller again issued clearance for the GPS approach.
Radar data showed that, during the approach, the airplane tracked a course that was offset about a
half mile right of the final approach course until it was about 1 mi. from the runway threshold. The
airplane then turned left toward the threshold and descended to an altitude of about 145 ft. AGL over
the runway threshold before the pilot performed a missed approach. “It is likely,” said the Safety
Board, “that the pilot performed the missed approach because he was unable to align the airplane
with the runway before it crossed the threshold.”
The controller provided radar vectors for the airplane to return to the approach course and cleared
the pilot a third time for the GPS approach to the runway. Radar data showed that the airplane was
established on the final approach course as it passed the initial approach fix; however, before it
reached the final approach fix, its airspeed slowed to about 111 kt., and it began a left turn with a 25-
deg. bank angle. About 18 sec. later, while still in the turn, the airplane slowed to 108 kt. and began
descending rapidly. The airplane’s rate of descent exceeded 10,000 ft. per minute, and it crashed into
trees and then the ground.
The impact created a crater that was 11-ft. long, 11 ft. wide, and 6 ft. deep. Broken tree branches that
contained 45-deg. angled cuts were observed at a height of about 50 ft. Investigators determined the
airplane impacted the ground at an approximate 70-deg. angle, consistent with being in an inverted
position. It was severely fragmented with debris scattered on a course of about 320 deg., for about
450 ft.
A post-crash fire consumed a majority of the airframe. Fragmentation of the wreckage precluded the
ability to confirm control continuity to the respective flight control surfaces. And as a result of impact
damage to the cockpit, Safety Board investigators could not determine the positions of ice protection
system switches at the time of the accident. Portions of the deice boot system were observed on wing
debris and portions of the horizontal stabilizer. The boots were destroyed by impact forces and fire.
Both propellers remained attached to their respective gearboxes, which had separated from their
respective engines. All three left propeller blades separated from the hub. Two right propeller blades
remained attached to the hub, and one blade had separated. Both propeller assemblies were severely
damaged and displayed evidence of rotational scoring; however, the right propeller blades displayed
a significantly greater degree of rotational scoring, tears and missing blade tips than the left blades.
Both engines had been damaged by impact and fire. Their respective fuel pumps and fuel control
units were separated. A subsequent teardown examination of the engines revealed no pre-impact
conditions that would have prevented normal operation. However, type and degree of damage to the
left engine was indicative of an engine that was not operating, with rotation consistent with a
windmilling propeller at the time of impact. Static impact marks were observed on the first and
second stage centrifugal compressor shrouds and no evidence of rotational scoring was noted on the
turbine section.
The type and degree of damage to the right engine was indicative of an engine that was operating
under power at the time of impact. Rotational scoring was observed on the first and second stage
centrifugal compressor shrouds and the first-, second- and third-stage turbine shroud. Almost all of
the vanes on the first-stage centrifugal compressor impellers were deformed and or separated. In
addition, the forward curvic coupling of the second-stage centrifugal compressor impeller was
heavily smeared.
The left engine fuel control unit was extensively damaged and could not be functionally tested.
Disassembly revealed no evidence of pre-impact malfunctions.
CAT scans of the left- and right-engine fuel shutoff valves revealed that they were both in the closed
position; however, their respective pre-impact position could not be confirmed. Teardown of the
valves revealed no evidence of any pre-impact failures. The left-engine fuel shutoff valve solenoids
could be opened and closed by applying electrical power directly to the solenoids. The right-engine
fuel shutoff valve solenoids did not function when electrical power was applied.
Examination of a vertical and directional gyro recovered from the wreckage was performed by the
NTSB Materials Laboratory. Despite impact and fire damage, tests revealed that VG and DG internal
damage was consistent with rotation at the time of the accident.
Ice
Safety Board specialists determined weather conditions present at the location and time of the
accident were conducive to supercooled liquid water droplets, and the airplane likely encountered
moderate or greater icing conditions. Several pilot reports (PIREPs) for moderate, light, trace and
negative icing were reported to ATC but were not distributed publicly into the National Airspace
System, and there was no Airmen’s Meteorological Information (AIRMET) issued for icing.
The type and degree of damage to the left engine was indicative of an engine that was not
operating, with rotation consistent with a windmilling propeller at the time of impact.
Investigators said the pilot had received standard and abbreviated weather briefings for the flight,
and his most recent weather briefing included three PIREPs for icing conditions in the area of the
accident site.
“Given the weather information provided,” said the Safety Board, “the pilot should have known icing
conditions were possible. Even so, the public distribution of additional PIREPs would have likely
increased the weather situational awareness by the pilot, weather forecasters and air traffic
controllers.”
The airplane’s deicing and anti-icing systems included wing and empennage deice boots and engine
inlet heaters. As noted, the position of the switches for the ice protection systems at the time of the
accident could not be determined.
In an analysis of the accident, investigators commented, “Although the airplane’s airspeed of 108 kt.
when the steep descent began was above its published stall speed of 77 kt., both bank angle and ice
accretion would have increased the stall speed. In addition, the published minimum control airspeed
was 93 kt. It is likely that, after the airplane passed the initial approach fix, the left engine lost power,
the airplane’s airspeed began to decay, and the asymmetric thrust resulted in a left turn. As the
airspeed continued to decay, it decreased below either stall speed or minimum control airspeed, and
the airplane entered an uncontrolled descent.”
Safety Board investigators examined both the maintenance history and ice-certification history of the
airplane. The high-wing, twin executive turboprop was manufactured in 1982. It was powered by
two Executive Wings Inc. STC-modified Garrett TPE331-5-511K 715-hp engines, equipped with
Hartzell three-blade constant-speed propeller assemblies.
According to maintenance records, the airplane’s most recent inspection was a 150-hr. periodic
inspection, which was performed on Feb. 1 — two days before the accident. At the time of the crash,
the airframe and both engines had been operated for about 4,460 total hours since new. The airplane
had been operated for about 70 hr. during the 13 months that preceded the accident.
According to the pilot operating handbook, the Commander 690C’s anti-icing system included heated
stall warning, rudder horn anti-ice, rudder tab anti-ice, generator inlet anti-ice, electrically heated
windshield and pitot-static heaters. The systems were designed to prevent ice accumulation and
were to be placed in operation prior to entering flight conditions conducive to ice formation. Engine
inlet heaters utilized hot engine compressor bleed air to prevent icing. The ice protection systems
were controlled by switches in the “ICE PROTECTION” group of the cockpit overhead switch panel.
The following warning, said the NTSB, was included under the Engine Inlet Anti-Ice Systems:
“Warning: When icing conditions may be encountered, do not delay operation of the engine inlet heat
systems. Turn the systems on before any ice accumulates. Engine inlet heat must be on if icing
conditions exist or are anticipated.”
The airplane was also equipped with a Negative Torque Sensing (NTS) system that was designed to
reduce drag caused by a windmilling propeller in the event of a loss of engine power by moving the
blades toward the feathered position to reduce drag and yaw.
Honeywell Operating Information Letter OI331-11R11, issued Sept. 16, 2013, emphasized proper use
of engine inlet anti-ice and provided additional information on the use of engine ignition in icing
conditions. The operating letter stated in part that engine inlet anti-ice should be used during all
flight in potential icing conditions and icing conditions should be considered to exist when flying in
precipitation or visible moisture (including clouds or fog) with an outside air temperature 10C or
50F, or colder. In addition, it stated, “If the use of anti-ice is inadvertently delayed after encountering
icing conditioning, ice may accumulate on engine and airframe inlet surfaces. In such instances,
subsequent application of engine inlet anti-ice can cause ice shedding and ingestion, which may
cause flameout. . . .”
So, in this case, it would seem that all the tolerances lined up unidirectionally. An airplane just out of
maintenance, only flown occasionally, susceptible to icing challenges, operating into an unfamiliar
destination in the face of what might be considered under reported mixed icing conditions came to
grief.
Those circumstances are worth thinking about.