Accident Lockheed L-188AF Electra N5523,

ASN Wikibase Occurrence # 327432

Date:	Wednesday 30 May 1984
Time:	01:44
Type:	Lockheed L-188AF Electra
Owner/operator:	Zantop International Airlines
Registration:	N5523
MSN:	1034
Year of manufacture:	1959
Total airframe hrs:	35668 hours
Cycles:	38353 flights
Engine model:	Allison 501-D13
Fatalities:	Fatalities: 4 / Occupants: 4
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	Chalkhill, PA - United States of America
Phase:	En route
Nature:	Cargo
Departure airport:	Baltimore/Washington International Airport, MD (BWI/KBWI)
Destination airport:	Detroit-Willow Run Airport, MI (YIP/KYIP)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
Zantop ground personnel completed the loading of Flight 931 at 00:40. All cargo was bulk loaded and tied down on the right side of the airplane for the full length of the cargo compartment. Flight 931 departed the gate at Baltimore/Washington International Airport at 01:05 and took off on runway 28 at 01:10. At 01:11:42, Flight 931 contacted Baltimore departure control and was cleared to 13,000 feet. After switching to Washington ARTCC, the flight was cleared further FL220. At 01:32 a no. 2 gyro malfunction made the crew select the no. 1 gyro to drive both approach horizons and the problem appeared resolved. At 01:43:09, Cleveland ARTCC cleared Flight 931 direct to the Dryer VOR. After the turn to the Dryer VOR, the first officers approach horizon may have displayed incorrect pitch and roll information. The flightcrew may have received conflicting pitch and roll information
from the two approach horizons as they attempted to recover from an unusual attitude. The flightcrew overstressed the airplane in an attempt to recover from the unusual attitude as the aircraft spiralled down. The Electra broke up and falling wreckage damaged some houses; however, most of the wreckage fell in uninhabited, wooded areas.

PROBABLE CAUSE: "The aircraft's entry into an unusual attitude and the inability of the flight crew to analyse the flight condition before there was a complete loss of control. Although the precise reason for the loss of control was not identified, an undetermined failure of a component in the No.2 vertical gyro system, perhaps involving the amplifier and associated circuitry, probably contributed to the cause of the accident by incorrectly processing data to the co-pilot's approach horizon. The in-flight structural failure of the aircraft was due to overload."

Accident investigation: