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N50PL accident description

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Tail numberN50PL
Accident dateDecember 12, 1999
Aircraft typeIsrael Aircraft Industries 1124A
LocationGouldsboro, PA
Additional details: None

NTSB description

HISTORY OF FLIGHT

On December 12, 1999, about 1635 eastern standard time, an Israel Aircraft Industries (IAI) 1124A, N50PL, was destroyed after impacting terrain near Gouldsboro, Pennsylvania. The two certificated airline transport pilots and a passenger were fatally injured. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the personal flight conducted under 14 Code of Federal Regulations (CFR) Part 91.

The flight departed from the Boeing Field/King County International Airport (BFI), Seattle, Washington, and proceeded eastbound, destined for the Teterboro Airport (TEB), Teterboro, New Jersey. After a 5-hour flight, the airplane began its descent to TEB. Air traffic control (ATC) instructed the flight crew to cross the Wilkes-Barre (LVZ) VOR at 18,000 feet, which the flight crew acknowledged. The flight was then instructed to cross the MUGZY intersection at 6,000 feet. The flight crew acknowledged the clearance, and no further transmissions were received from the airplane.

Several witnesses stated that they observed the airplane before its impact. One witness, who was riding in the front passenger seat of her car heading southeast on Interstate 380 in Pennsylvania, stated that she saw an airplane in a near vertical climb level off, then begin a pattern of "twists, swoops, and turns." The witness also observed a fairly dark smoke trail but stated that it was "not a thick trail of smoke." Several other people in the same car thought that the airplane was performing acrobatic maneuvers. The witness added that the airplane's movements became more erratic as it made more "flips and turns" and that it went straight down "nose first, no spinning, twisting, or corkscrewing."

Another witness, who was standing in his yard at a mobile home complex, observed an airplane flying close to the treetops. The witness stated that he heard the sound of the engines being "fired up" and that the airplane went into a vertical climb. He added that the airplane completed one spiral, then "the nose came down" into the ground.

A third witness, who was also traveling southeast on Interstate 380, stated that she observed the airplane "dipping" toward the highway. She stated that it then ascended steeply, completed several spins, and made a final descent. The witness added that, at the time, she thought it was a model airplane performing acrobatic maneuvers.

A fourth witness, who was getting out of his car at a nearby rifle range, stated that the airplane came at him from the trees. He added that it then went straight up into the air, and "nose dived" to the ground. He then heard an explosion about 10 seconds later, and observed smoke rising from the trees.

A fifth witness, who was sitting on his porch, stated that he observed an airplane and heard a "pop" noise, like the engine had quit. According to the witness, the airplane then flew "tipsy" like it was in turbulence and then the engine sounded like it had started up again. The witness added that as the airplane passed low overhead, it sounded like something out of "Top Gun." He further added that the airplane was intact and that the engines were red. The witness stated that there was no fire or smoke emanating from the airplane prior to impact.

The airplane struck treetops and impacted the ground in a wooded area, which surrounded a mobile home complex.

The accident occurred during the hours of daylight approximately 42 degrees, 28 minutes north latitude, and 76 degrees, 8 minutes west longitude.

FLIGHT CREW INFORMATION

Captain

The captain held an airline transport pilot certificate with a rating for airplane multi-engine land and commercial privileges for airplane single-engine land and sea. In addition, the captain was type rated in the Gulfstream G-1159, Israel Aircraft Industries IAI-Jet, and Lear Jet. The captain also held a flight instructor certificate for airplane single land.

The captain reported 9,700 hours of total flight experience on his last application for a medical certificate. The captain's pilot logbook was not recovered.

According to company records, the captain last attended recurrent training in the IAI-1124, on February 15, 1999.

The captain's most recent Federal Aviation Administration (FAA) first class medical certificate was issued on February 1, 1999.

First Officer

The first officer held an airline transport pilot certificate with a rating for airplane multi-engine land and commercial privileges for airplane single-engine land and sea. In addition, the first officer was type rated in the Israel Aircraft Industries IAI-Jet. He also held a flight instructor certificate for airplane single and multi-engine land.

According to the first officer's most recent pilot logbook entries, he recorded 4,413 hours of total flight experience.

According to company records, the first officer last attended recurrent training in the IAI-1124, on January 5, 1999.

The first officer's most recent FAA first class medical certificate was issued on January 29, 1999.

AIRCRAFT INFORMATION

Examination of the airplane maintenance records revealed that on February 20, 1998, the airplane's horizontal jackscrew actuator was overhauled and returned to service by Lucas Aerospace Power Equipment Corporation, Aurora, Ohio. The actuator was then installed in the airplane on February 26, 1998, and an entry was made in the airplane flight log describing the installation. The airplane flight log entry did not mention, however, that the installation of the new actuator would have terminated the repetitive inspections required by Airworthiness Directive (AD) 98-20-35, Amendment 39-10802.

On October 9, 1998, an "A" check was accomplished in accordance with the IAI inspection guide. The entries made in the airplane flight log did not mention compliance with AD 98-20-35 Amendment 39-10802, nor was it required.

The airplane maintenance records also revealed that on December 10, 1999, an "A" check was accomplished in accordance with the IAI inspection guide. Among the activities completed during the inspection, the left-hand elevator was removed from the airplane, painted, balanced per the maintenance manual, and reinstalled.

Examination of the airplane's flight log revealed stickers that were added to two pages of the log. The stickers were dated December 10, 1999, and described work that was accomplished during the "A" check. One of the stickers stated, "Complied with an "A" check in accordance with I.A.I. inspection guide. Complied with A.D. 98-20-35 Amendment 39-10802 on inspection of trim actuator. Actuator was replaced 3/98. This terminates the repetitive inspections I.A.W. Para. (2) (a) of this AD."

Review of the airplane's flight log revealed that the airplane had accumulated about 170 hours of total flight time in the previous year. The airplane's last flight prior to maintenance was on December 1, 1999. The airplane accumulated 3.6 hours of flight time and 3 cycles that day.

According to line service personnel at BFI, the airplane was last fueled on December 11, 1999, with about 958 gallons of Jet A fuel. A fuel additive was mixed with the fuel, as requested by the pilot.

METEOROLOGICAL INFORMATION

The weather reported at 1645, by the Wilkes-Barre Wyoming Valley Airport, Avoca, Pennsylvania, was calm winds, 10 statute miles of visibility, and clear skies.

FLIGHT RECORDERS

Cockpit Voice Recorder

The airplane was equipped with a B&D cockpit voice recorder (CVR). The CVR was transported to the Safety Board on December 13, 1999. The CVR group convened on December 20, 1999. A transcript was prepared for the entire 32 minute 50 second recording.

The following are excerpts of the CVR transcript:

1621:16, the first officer stated, "elevator up... my light just flashed on."

1621:22, the captain stated, "oh, your trim did?"

1621:22, the first officer stated, "yeah... there it goes again."

1621:25, the cockpit area microphone (CAM) recorded [sound of beep]

1621:48, the CAM recorded [six beeps similar to altitude alert signal]

1622:21, the captain stated, "your trim didn't work in the up position either, did it?"

1623:00, the captain stated, "let me know if you see that light again."

1623:03, the first officer stated, "I will, I will."

1623:20, the first officer stated, "where's it gonna go?"

1624:07, the captain stated, "they probably won't be able to do anything about the mic thing."

1627:12, the captain stated, "** box grounds in turbulence." [* denotes unintelligible word(s)]

1628:34, the first officer stated, "afraid to touch anything in here."

1629:25, the captain stated, "we got a problem here **** schedule anyway."

1630:04, the CAM recorded [six beeps similar to altitude alert signal]

1635:01, the first officer stated, "oooh, lights. oohoo."

1635:04, the captain stated, "amazing."

1635:07, the first officer stated, "what is *?"

1635:09, the first officer stated, "a series of lines with contacts with for these lights through there."

1635:13, the captain stated, "yeah."

1635:14, the first officer stated, "one of these lights, all the contacts around it were broken off. so they had to put a new one on there and weld them all together... complete the circuit."

1637:45, the first officer stated, "it's trimmin'."

1637:47, the captain stated, "yeah I left the autopilot on intentionally."

1638:05, the captain stated, "yeah, I think this autopilot bus looks * mine."

1638:55, the CAM recorded [sound of three beeps]

1638:56, the first officer stated, "elevator out of trim."

1638:57, the captain stated, "which way?"

1638:58, the CAM recorded, "up."

1639:00, the CAM recorded [increase in general cockpit noise similar to aircraft increasing in speed]

1639:23, the captain stated, "keep pushin'."

No further conversations or noises were recorded on the CVR.

Sound Spectrum Study

A sound spectrum study was performed to analyze a sound that was heard in the last 27 seconds of the accident recording. According to the Safety Board specialist's report, the CVR recording consisted of four channels of fair quality audio information. All four channels were examined for the noise in question. The noise was not contained on any of the three channels designated for the captain, first officer and CAM. The noise appeared to be contained on the fourth channel only. The fourth channel did not contain any vocal or acoustic audio information.

The noise on the fourth channel consisted of signals that decreased and increased in frequency until the end of the recording. Specifically, two signals appeared to increase in frequency at about the 27-second mark, and one signal of about 750 Hz at 20 seconds decreased to about 300 Hz at the end of the recording. The sound spectrum also revealed a decreasing frequency signal at about 24 seconds emerging from the background noise that decreased in frequency from approximately 7,500 Hz to 3,000 Hz when the recording ended. The last 10 seconds of the recording contained the sound of an electrical buzz, which decreased in frequency until the end of the recording. Notably, a 60-Hz signal and corresponding harmonics were present in the spectrum, that was not attributed to the CVR or the aircraft because the signal continued through the end of the recording. Although the exact cause for the electrical noise was not ascertained, it did not appear to be the result of a malfunction or anomaly of the CVR. Moreover, the noise was generated by the aircraft but was not acoustically recorded through the microphone. It was determined to most likely be a by-product of the electrical system that had been introduced into the fourth channel wiring and recorded by the CVR.

Flight Data Recorder

There was no flight data recorder installed in the airplane, nor was it required.

WRECKAGE INFORMATION

The airplane wreckage was examined at the accident site on December 13, 1999. Inspection of surrounding trees, the impact crater, and wreckage revealed that the airplane struck the ground about 80-degrees nose-down, wings level, with the nose of the airplane facing about 235 degrees. Debris from the wreckage was scattered from the main impact crater outward, about 337 feet, in a 180-degree arc about the centerline of the airplane.

All of the airplane's major components and flight control surfaces were located at the accident site; however, the cabin and fuselage were fragmented into numerous pieces by the impact.

Both wings were separated from their respective wing-to-fuselage attach fittings and remained at the impact crater. Both the left and right flaps were damaged; however, they remained partially connected at their wing flap track assemblies and were found in the full-retracted position. Sections of the outboard wings were located with the ailerons attached. Portions of the left and right wings and fuel tip tanks were located near the impact crater.

The vertical stabilizer was found about 200 degrees and 57 feet forward of the impact crater. The rudder was about 250 degrees and 91 feet forward of the impact crater.

The engines and sections of the aft portion of the airplane were located about 5 feet forward of the main impact crater. The horizontal stabilizer trim actuator was attached to its support structure on the aft main fuselage. The actuator was missing one of its electric motors, and did not have a dust shield surrounding the jackscrew torque tubes. Closer examination of the actuator revealed that the jackscrews inside the torque tubes were sheared. Attached to the horizontal stabilizer front spar attach point were two rod ends. Attached to one of the rod ends was an adapter with a tie rod installed through it. The other adapter remained attached to the tie rod. Examination of the rod end adapters did not reveal any jackscrews threaded into them, and the threads were clean and displayed no visible damage. When the aft portions of the airplane were removed from the crater, the horizontal stabilizer trim actuator dust shield and separated pieces of jackscrews were found underneath. The top of the dust shield was crushed. Holes, which were machined at the top of the dust shield to accept a tie rod, did not display any visible damage and the tie rod was not installed. The separated pieces of the jackscrews, which were found inside the dust shield, contained two different thread types. A fine thread was at the machined end, and a coarser thread was at the fractured end. The finer thread section of the jackscrews also had machined holes through them to accept a tie rod. The holes and threads were not damaged and the tie rod was not installed. One of the electric motors for the horizontal stabilizer trim actuator was also located inside the crater.

The rudder and elevator control stops were examined and revealed normal wear.

Continuity of the engine and flight control surfaces could not be determined due to impact damage.

Both main landing gear assemblies were found inside the impact crater. The nose gear was found about 152 feet forward of the impact crater. The main and nose gear actuators were not found during the on-scene examination.

Pieces of circuit breaker panels from the cockpit area were located in numerous areas of the accident site. When the panels were examined, no visual signs of arcing or soot were observed.

MEDICAL AND PATHOLOGICAL INFORMATION

Neither an autopsy nor toxicological testing was performed on the two pilots.

TEST AND RESEARCH

Engine Teardown

The airplane's engines were examined at the Honeywell Aerospace Investigation Laboratory, Phoenix, Arizona, on February 16, 17, and 18, 2000, under the supervision of an FAA inspector. The examinations revealed that the engines sustained impact and fire damage. Both engines exhibited indications of rotation at impact. No pre-impact conditions were found that would have interfered with normal operation of either engine.

Airplane Pitch Control

The airplane's pitch was controlled by two methods, the horizontal stabilizer and two elevators. The horizontal stabilizer had a NACA 64.A010 airfoil and was swept back at an angle

(c) 2009-2011 Lee C. Baker. For informational purposes only.