ASN Aircraft accident Lockheed L-188AF Electra N5523 Chalkhill, PA
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Status:Accident investigation report completed and information captured
Date:Wednesday 30 May 1984
Type:Silhouette image of generic L188 model; specific model in this crash may look slightly different
Lockheed L-188AF Electra
Operator:Zantop International Airlines
Registration: N5523
MSN: 1034
First flight: 1959-02-09 (25 years 4 months)
Total airframe hrs:35668
Engines: 4 Allison 501-D13
Crew:Fatalities: 3 / Occupants: 3
Passengers:Fatalities: 1 / Occupants: 1
Total:Fatalities: 4 / Occupants: 4
Aircraft damage: Destroyed
Aircraft fate: Written off (damaged beyond repair)
Location:Chalkhill, PA (   United States of America)
Phase: En route (ENR)
Departure airport:Baltimore/Washington International Airport, MD (BWI/KBWI), United States of America
Destination airport:Detroit-Willow Run Airport, MI (YIP/KYIP), United States of America
Flightnumber: 931
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 officer’s 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:

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:

Investigating agency: NTSB
Status: Investigation completed
Duration: 293 days (10 months)
Accident number: NTSB/AAR-85-04
Download report: Final report

Fuselage failure
Loss of control

» NTSB-AAR/85-04

Follow-up / safety actions
As a result of this accident, the Safety Board reiterated Safety Recommendation A-80-19 to the Federal Aviation Administration. The FAA this time agreed with the recommendation, but it lasted seven years before the FAA issued a final rule amending 14 CFR 121.305 effective October 15, 1992.

NTSB issued 1 Safety Recommendation

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photo of Lockheed-L-188AF-Electra-N5523
accident date: 30-05-1984
type: Lockheed L-188AF Electra
registration: N5523

This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Baltimore/Washington International Airport, MD to Detroit-Willow Run Airport, MI as the crow flies is 666 km (416 miles).
Accident location: Approximate; accuracy within a few kilometers.

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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