Date:	Thursday 21 February 2008
Time:	17:05
Type:	ATR 42-300
Owner/operator:	Santa Bárbara Airlines
Registration:	YV1449
MSN:	028
Year of manufacture:	1986
Total airframe hrs:	37138 hours
Engine model:	Pratt & Whitney Canada PW120
Fatalities:	Fatalities: 46 / Occupants: 46
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	ca 10 km NW of Mérida-A Carnevalli Airport (MRD) -   Venezuela
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Mérida-A Carnevalli Airport (MRD/SVMD)
Destination airport:	Caracas-Simón Bolívar International Airport (CCS/SVMI)
Investigating agency:	JIAAC Venezuela
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
An ATR-42-300 operating Santa Bárbara Airlines Flight 518 was destroyed when it impacted the side of a mountain shortly after takeoff from Mérida-A Carnevalli Airport in Venezuela. All 46 on board were killed.
Mérida Airport is located in a mountain valley at an elevation of 5010 feet. Terrain in the valley rises from 1000 to 19.500 feet. Arrivals and departures have to use the Rio Chama corridor to the west of the airport. Runway 07 is used for landings and takeoffs have to be performed in the opposite direction, from runway 25.
Santa Bárbara Airlines however used an unpublished approach and departure procedure which let the aircraft use a valley to the northeast of the airport. This procedure saved about 15 minutes of flying time on the route to Caracas.
After all passengers had boarded for flight 518 to Caracas, it took about 30 minutes for the pilots to arrive at the aircraft. Being late, they immediately started the engines while simultaneously asking for permission to do so.
Because an Avior Airlines flight was approaching the airport, the crew were told to expedite their departure or wait for the arrival of the Avior aircraft. The flight crew decided to go and began taxiing 2 minutes and 40 seconds after startup. Consequently the AHRS (attitude and heading reference) system of the airplane was unusable. The aircraft needed to remain still for 3 minutes after the battery is turned on so that all gyroscopes, accelerometers and magnetometers can be stabilized and synchronized.
The AHRS provides attitude information for aircraft, including roll, pitch and yaw. The captain possibly expected to re-initialize the system while they were at cruising altitude.
After departure from runway 25 the crew planned to use the unpublished procedure. Climbing through clouds a 180-degree turn was initiated. Using the unreliable magnetic compass, the flight made a 270 degree turn, heading towards rising terrain. The captain took over control from the copilot. When visual contact with terrain was regained, the crew noted they were heading for mountains. The captain tried to avoid rising terrain but the aircraft impacted the side of a mountain at 3810 m.

CONCLUSIONS
The attitude and heading reference system (AHRS) as a device was operational, however the initialization of the system was incomplete, so the standard mode was in a fault condition. This failure mode left the RMI or radio magnetic indicators and the autopilot inoperative.
The EGPWS or enhanced ground proximity warning system was inoperative in the "enhanced" functions, since the information is displayed on the EFIS system screens, therefore there was no early warning (Visual) of impact against the mountain range.
The GPS was the only instrument capable of providing heading information to within one degree of accuracy. Because it is located on the co-pilot's lower left panel, the information provided by the co-pilot was basically available for co-pilot observation. In addition, the size of the display is relatively small for the information it shows.
The crew was valid, qualified and certified by the National Institute of Civil Aeronautics (INAC). However, the crew was very unconcerned to learn that they were taking off with the AHRS system inoperative and the weather conditions were instrument or IMC.
The meteorological station in Merida was inoperative.
The control tower did not have an operational communications recording system.
According to the deformation shown on the low pressure compressor wheels, the engines had power at the time of impact.

21:00 UTC / 17:00 local time:
SVMD 212100Z 29008KT 9999 SCT013 BKN100 XX/XX Q1018=

22:00 UTC / 18:00 local time:
SVMD 212200Z 25005KT 9999 BKN013 OVC100 20/12 Q1021=

LAGAD Aviation
NotiSAR
Instituto Nacional de Aeronáutica Civil (INAC)

Other occurrences involving this aircraft

4 April 1993

N422MQ

Simmons Airlines

Chicago, IL

min

photo (c) Google Earth; Mérida-A Carnevalli Airport (MRD/SVMD)

photo (c) Ulrich F. Hoppe; Caracas-Simón Bolívar International Airport (CCS/SVMI); 06 December 2007

Date/time	Contributor	Updates