DCA12CA042

NTSB accident investigation · Embraer EMB120 · Iliamna, AK · February 16, 2012

Accident · No injuriesData collectionFinal report
Date
February 16, 2012, 13:08 local (17:08 UTC)
Place
Iliamna, AK
Injuries
2 uninjured
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N1110JEmbraer EMB120
Defining event
Enroute-descent: Flight control sys malf/fail
Weather
Visual (VMC) · Day
Status
Completed · report March 30, 2020
Report
Approved by Office Director
NTSB office
Major Investigations Division
FAA report
20120216002539A
Case key
82916

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

the maintenance personnel's failure to install the cotter pins that secured castellated nuts on the left elevator vertical hinge bolts, which resulted in the left elevator partially detaching in flight. Contributing to the accident was the failure of maintenance personnel to document the non-routine maintenance procedure that was used to remove and reinstall the elevator during maintenance.

Findings · 3

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Action: incorrect action performancePersonnel issues › Action/decision · Maintenance personnelEmbraer EMB-120FC: 1 caseAll aircraft: 1,386 casesProbable cause
Record-keeping: aircraft/maintenance logsPersonnel issues › Task performance · Maintenance personnelEmbraer EMB-120FC: 1 caseAll aircraft: 21 casesProbable cause
Maintenance: repairPersonnel issues › Task performance · Maintenance personnelEmbraer EMB-120FC: 1 caseAll aircraft: 99 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

On February 16, 2012, at about 1308 local time, Everts Air Cargo flight 1291, an Embraer EMB-120, N1110J, experienced an uncommanded pitch down while descending into Iliamna Airport (KILI), Iliamna, Alaska. There were no injuries to the 2 crewmembers onboard but the airplane sustained substantial damage. The flight was operating under 14 CFR Part 121 Supplemental as a cargo only flight from Anchorage, Alaska (KANC) to KILI. The Captain reported that the flight from KANC had been uneventful. The Captain reported that during the descent, while at about 250 knots airspeed with his hands on the controls and the autopilot engaged, the airplane pitched to about 20 degrees nose down. The captain reported he then disconnected the autopilot and adjusted the pitch trim while pulling back on the column to recover from the pitch excursion. The flight crew declared an emergency and slowed the airplane to about 200 knots. Approximately 5-10 miles from the airport, while in a slow left turn at 3000 feet msl altitude, the airplane pitched down a second time while the captain was hand flying. As he recovered from the pitch down, he was lined up for a 5 mile final approach for runway 35. The captain elected to make a high speed, flaps up landing and landed uneventfully on runway 35. Post-flight inspection revealed that the left elevator was bent at the mid span trim tab, had partially detached from the aircraft, and was missing two attachment bolts. A review of the airplane maintenance history showed that while in "A" check maintenance, a dent was noted in the left elevator and the elevator was removed. The maintenance team did not follow the EMB 120 maintenance manual procedure for removal of the left elevator. During the non-routine maintenance procedures used by the maintenance team, cotter pin safeties that were removed from castellated nuts on the 2 outboard vertical hinge bolts on the left elevator were not reinstalled. The removal of these two bolts is not part of the EMB 120 maintenance manual procedure for removal of the left elevator. The maintenance team did not document the non-routine procedure they used to remove and reinstall the left elevator. The Require Inspection Items (RII) inspector had inspected the elevator installation for the procedures in the manual and was not aware of the undocumented non-routine maintenance procedures used, and hence did not examine the nuts that did not have the required cotter pins, which were not to be removed as part of the approved procedure. The FAA found that the maintenance teams that removed and reinstalled the elevator were inexperienced in EMB 120 elevator removal and reinstallation procedures.

Factual narrative

On February 16, 2012, at about 1308 local time, Everts Air Cargo flight 1291, an Embraer EMB-120, N1110J, experienced an uncommanded pitch down while descending into Iliamna Airport (KILI), Iliamna, Alaska. There were no injuries to the 2 crewmembers onboard but the airplane sustained substantial damage. The flight was operating under 14 CFR Part 121 Supplemental as a cargo only flight from Anchorage, Alaska (KANC) to KILI. The Captain reported that the flight from KANC had been uneventful. The Captain reported that during the descent, while at about 250 knots airspeed with his hands on the controls and the autopilot engaged, the airplane pitched to about 20 degrees nose down. The captain reported he then disconnected the autopilot and adjusted the pitch trim while pulling back on the column to recover from the pitch excursion. The flight crew declared an emergency and slowed the airplane to about 200 knots. Approximately 5-10 miles from the airport, while in a slow left turn at 3000 feet msl altitude, the airplane pitched down a second time while the captain was hand flying. As he recovered from the pitch down, he was lined up for a 5 mile final approach for runway 35. The captain elected to make a high speed, flaps up landing and landed uneventfully on runway 35. Post-flight inspection revealed that the left elevator was bent at the mid span trim tab, had partially detached from the aircraft, and was missing two attachment bolts. A review of the airplane maintenance history showed that while in "A" check maintenance, a dent was noted in the left elevator and the elevator was removed. The maintenance team did not follow the EMB 120 maintenance manual procedure for removal of the left elevator. During the non-routine maintenance procedures used by the maintenance team, cotter pin safeties that were removed from castellated nuts on the 2 outboard vertical hinge bolts on the left elevator were not reinstalled. The removal of these two bolts is not part of the EMB 120 maintenance manual procedure for removal of the left elevator. The maintenance team did not document the non-routine procedure they used to remove and reinstall the left elevator. The Require Inspection Items (RII) inspector had inspected the elevator installation for the procedures in the manual and was not aware of the undocumented non-routine maintenance procedures used, and hence did not examine the nuts that did not have the required cotter pins, which were not to be removed as part of the approved procedure. The FAA found that the maintenance teams that removed and reinstalled the elevator were inexperienced in EMB 120 elevator removal and reinstallation procedures.

Aircraft

Registration
N1110J
Reported as
Embraer EMB120 (FC)
Category
Airplane
Serial number
120.110
Built
1988
Engines
Pratt & Whitney Canada PW118, turbo propPratt & Whitney Canada PW118, turbo prop
Damage
Substantial damage
Flight
Part 121
Operator
Arctic One Llc
Registered owner
Arctic One Llc
Airworthiness certificate
Standard, Transport
Departed
ANC · Anchorage, AK
Destination
ILI · Iliamna, AK
Flight plan
IFR
Airport
ILI · Iliamna, runway 36, 4,800 × 100 ft, asphalt

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Weather

Conditions
Visual (VMC) · Day
Observed at
PAIL, 1 nm away

Docket · 1

The files NTSB released with the investigation on July 21, 2021, on NTSB’s docket system: statements, records, photos and specialists’ reports. 60 KB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.