Date:	Tuesday 6 February 1996
Time:	23:47
Type:	Boeing 757-225
Owner/operator:	Alas Nacionales
Registration:	TC-GEN
MSN:	22206/31
Year of manufacture:	1984
Total airframe hrs:	29269 hours
Cycles:	13499 flights
Engine model:	Rolls-Royce RB211-535E4
Fatalities:	Fatalities: 189 / Occupants: 189
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	26 km NE off Puerto Plata, Dominican Republic -   Atlantic Ocean
Phase:	En route
Nature:	Passenger - Non-Scheduled/charter/Air Taxi
Departure airport:	Puerto Plata-La Union International Airport (POP/MDPP)
Destination airport:	Gander Airport, NL (YQX/CYQX)
Investigating agency:	DGAC Dom. Rep.
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
Alas Nacionales flight 301 departed Puerto Plata for a charter flight to Frankfurt via Gander and Berlin at 23:42 LT. At 80 knots on takeoff the captain found out that his air speed indicator (ASI) wasn't working properly. The co-pilot's indicator seemed to work fine. While climbing through 4700 feet the captain's ASI read 350 knots (real speed was about 220 kts); this resulted in an autopilot/autothrottle reaction to increase the pitch-up attitude and a power reduction in order to lower the airspeed. At that time the crew got 'Rudder ratio' and 'Mach airspeed' advisory warnings. Both pilots got confused when the co-pilot stated that his ASI read 200 knots decreasing while getting an excessive speed-warning, followed by a stick shaker warning. This led the pilots to believe that both ASIs were unreliable.
Finally realizing that they were losing speed and altitude they disconnected the autopilot. The autopilot, fed by the captain's faulty ASI, had reduced the speed close to the stall speed. Full thrust was then applied. At 23:47:17 an aural GPWS warning sounded. Eight seconds later the aircraft struck the ocean.
The incorrect ASI readings were probably caused by the obstruction of the pitot system by mud and/or debris from a small insect that was introduced in the pitot tube during the time the aircraft was on the ground. The aircraft was not flown for 20 days before the crash and was returned for service without a verification of the pitot-static system as recommended by Boeing.

PROBABLE CAUSE: "The crew's failure to recognize the activation of the stick shaker as a warning of imminent entrance to the stall, and the failure of the crew to execute the procedures for recovery from the onset of loss of control."

Air Safety Week 12 February 1996 (p. 1)
Aviation Week & Space Technology 12.02.96(33,34)
Flight International 14-21 February 1996 (4)
NTSB Safety Recommendations A-96-15 through -20
Erroneous Airspeed Indications Cited in Boeing 757 Control Loss (Flight Safety Foundation - Accident Prevention October 1999)

photo (c) Werner Fischdick; Düsseldorf Airport (DUS); 05 June 1994

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