- Date
- April 5, 1991, 14:51 local (19:51 UTC)
- Place
- Brunswick, GA
- Injuries
- 23 fatal
- Damage
- Destroyed
- Phase of flight
- Approach
- Aircraft
- N270ASEmbraer EMB-120RT
- Weather
- Visual (VMC) · Day
- Status
- Completed · report August 5, 1993
- Report
- Board-adopted at Board Meeting
- Investigation class
- Class 1
- NTSB office
- Major Investigations Division
- Safety recommendations
- Yes
- FAA report
- 19910405009019A
- Case key
- 15951
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 loss of control in flight as a result of a malfunction of the left engine propeller control unit which allowed the propeller blade angles to go below the flight idle position. Contributing to the accident was the deficient design of the propeller control unit by hamilton standard and the approval of the design by the federal aviation administration. The design did not correctly evaluate the failure mode that occurred during this flight, which resulted in an uncommanded and uncorrectable movement of the blades of the airplane's left propeller below the flight idle position. (NTSB report AAR-92/03)
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
Witnesses reported that the airplane suddenly turned or rolled left until the wings were perpendicular to the ground. The airplane then fell in a nose-down attitude. Exam of the left prop components indicated a blade angle of about 3 deg, while the left prop control unit (pcu) ballscrew position was consistent with a commanded blade angle of 79.2 deg. Extreme wear on the pcu quill spline teeth, which normally engaged the titanium-nitrided splines of the prop transfer tube, was found. The titanium-nitrided surface was much harder and rougher than the nitrided surface of the quill. Therefore, the transfer tube splines acted like a file and caused abnormal wear of the gear teeth on the quill. Wear of the quill was not considered during the certification of the propeller system.
Aircraft
- Registration
- N270AS
- Reported as
- Embraer EMB-120RT
- Category
- Airplane
- Serial number
- 120-218
- Airframe hours
- 816
- Engine
- P&W PW-118, 1,800 horsepower, turbo prop
- Damage
- Destroyed
- Fire
- On-Ground
- Flight
- Part 135
- Operator
- Atlantic Southeast Airlines
- Airworthiness certificate
- Standard, Transport
- Last inspection
- Continuous airworthiness · April 1, 1991 · 26 hours before
- Departed
- ATL · Atlanta, GA
- Flight plan
- IFR
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.
Flight crew
As NTSB recorded them. NTSB leaves out names.
- Role
- Pilot
- Age
- 34
- Certificates
- Airline transport, Commercial
- Airplane ratings
- Multi-engine land, Single-engine land
- Instrument ratings
- Airplane
- Medical
- Class 1, Valid Medical--no waivers/lim.
- Seat
- Left
- Toxicology
- Performed
- Flight hours
- 11,724 total · 5,720 in this make and model
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 160° at 10 knots
- Visibility
- 7 statute miles
- Lowest ceiling
- 10,000 ft broken
- Temperature
- 79 °F, dew point 70 °F
- Altimeter
- 30.00 inHg
- Observed at
- BQK, 2 nm away
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.