USA Jet Airlines DC91 at Saltillo on Jul 6th 2008, crashed aside of the runway
Last Update: September 26, 2018 / 14:43:43 GMT/Zulu time
The continuation of an unstable final approach without having the runway in sight and consequent loss of control at low altitude before imminent impact.
Contributing factors were:
- weather conditions at the airport
- unstabilized approach
- lack of experience by first officer
- standard operating procedures not being followed by crew
- lack of operating procedures
- standard operating procedures not being followed by Saltillo Tower
- lack of supervision by authorities
- the coincidence of factors each of which alone would not represent a substantial increase in the risk of operation added: night flight at dawn, little experience by the first officer, omission of briefing by the captain, only one Jeppeson plate for two pilots, DME#2 inoperative, flight director bars inoperative at the captain's side, DME arc standard arrival approach procedure, lack of reports of fog banks and finally saturation of frequency in communication with the center of Monterrey.
The Mexican Transport Ministry (SCT) reported the prevailing weather conditions at the time of the accident at Saltillo Airport were: winds calm, visibility 2 miles limited by haze, broken cloud at 1000 feet, cloudy at 12,000 feet.
The crew had already operated two sectors the same day prior to the accident flight: Detroit Willow,MI (USA), departure about 18:00L (22:00Z) Jul 5th 2008 to Hamilton,ON (Canada) to Shreveport, LA (USA). The crew added 20,000 lbs of fuel in Shreveport and departed Shreveport at 00:48L (04:48Z) with an estimated time of arrival in Saltillo at 01:25L (06:25Z).
The captain (ATPL, 7,146 hours total, 2,587 hours on type) was pilot flying, the first officer (CPL, 6,842 hours total, 88 hours on type) pilot monitoring for the accident sector. The crew contacted Monterrey Center at 00:52L, the next 7 minutes there was total silence in the cockpit. The captain made a brief explanation of plans indicating once they got there, they would fly a heading of 240 for 45 seconds, then turn back and intercept the localizer. The first officer immediately queried whether they would perform a straight in approach, the captain did not respond, a clearance by ATC to descend to FL200 interrupted and the captain did not return to the subject. The aircraft subsequently cleared to 12,000 feet Altimeter 30.06, while descending through 19500 feet both pilots adjusted their altimeters at once, the altimeters were crosschecked at 18700 feet. ATC cleared the flight for the ILS DME 2 approach to runway 17. The first officer requested the current weather, approach reported the weather to the crew as stated above, the crew took note to the clouds however did not mention the visibility.
Descending through 8300 feet the captain advised they were crossing radial 002 of the VOR Saltillo and asked the first officer for the DME, the first officer's DME showed 12nm (the captain did not have a working DME), the captain requested the frequency of the ILS, first officer reported the frequency and inbound radial (172), the captain asked for the minimum safe altitude until 10nm out, the first officer reported 6800 feet. The landing gear was lowered and the flaps extended to 30 degrees (jumping the intermediate setting of 20 degrees). The landing checklist was read. While working the landing checklist the minimum setting was checked, the captain responded 4646 feet which is the elevation of the runway touchdown zone. The flaps were further extended to 40 degrees and the landing checklist was completed 50 seconds prior to the aircraft descending through 1000 feet above the aerodrome.
Descending through about 6000 feet the captain queried whether the first officer's glide slope indications were erroneous, too, the first officer advised the indications appeared erroneous too, they were high. The EGPWS sounded "Sinkrate!", the first officer also called the high sink rate, the captain indicated he was correcting. According to the FDR they were descending at 3000 fpm through 1000 feet AGL, the captain gradually reduced the sink rate to 500 fpm briefly, then the sinkrate increased again and reached 1300 fpm at 400 feet AGL.
Descending through 500 feet AGL the first officer called out the height and simultaneously Monterrey handed them off to Saltillo Tower. The captain queried whether they had been cleared to land, the first officer replied they had not yet been cleared to land. The sinkrate increased to 1400 fpm at 300 feet AGL, the captain commented he couldn't see the field, and the sounds of the engines changed indicating the engines were accelerating. Both engines had slowed down during the approach and were now spooling up to 2.1 EPR about 9 seconds prior to impact. The right hand engine suffered four compressor stalls after exceeding EPR 2.0. Until then the wings were level, but now with each compressor stall the bank angle increased, after the first stall visible on the airport surveillance camera the bank angle was 15 degrees to the right, following the second compressor stall the bank angle was 55 degrees to the left, following the third compressor stall the aircraft rolled abruptely to 85 degrees bank angle to the right just before impact. The right hand wing tip contacted an embankment 480 meters to the east of the runway 17 center line. The aircraft subsequently smashed two medium voltage power lines and impacted the road where it came to rest.
The captain received fatal injuries, the first officer survived with serious injuries.
The left hand engine was installed on the airframe on May 31st 2006 and had accumulated 46,445 flight hours in 51,071 flight cycles until then. The right hand engine was installed on the aircraft on Jun 3rd 2008 and had accumulated 54,633 flight hours in 45,842 flight cycles. The left engine had operated 1,972 hours in 1372 flight cycles since installation on the airframe, the right hand engine 102 hours in 78 flight cycles.
The aircraft had been dispatched with DME#2 inoperative, the captain's flight director bars inoperative as well as the left hand engine's fire loop A malfunctioning according to minimum equipment list requirements. The loading was within limits, the CG was within the permitted envelope. The aircraft was estimated to land about 10 tons under maximum landing weight.
The SCT analysed that the first officer had begun his training on the DC-9 in early April 2008 and completed his simulator training by end of April. Most of the hours logged on the DC-9 were simulator training, only 7.2 hours were on an actual aircraft before departure for the accident flight. This also makes clear that the necessary continuity of training was not followed necessary for qualification as type rated pilot.
The SCT further analysed that the airline had the habit of not using the radio altimeters for any kind of approach. This remove an additional layer of defense easily available. In addition the airline has the habit of adjusting the minimum altitude bug to the touchdown zone altitude.
The airline had provided two sets of flight charts for US domestic operation, however, only provided on set of flight charts for Mexico.
At the time of the accident the captain had been up for 20 hours and 13 minutes after his last rest due to being on stand by and being called in for the rotation. His actual duty time at the time of impact was 8 hours 13 minutes of which he had flown 5.4 hours.
The first officer had flown a sector on Jul 5th arriving in Concord at 01:07L, then went onto a flight to Michigan as passenger. There he was assigned the rotation that ended in Saltillo. No records were available to identify when the first officer arrived in Michigan and how he spent the time until departure, however, this time was less than 13 hours and insufficient for rest.
When the crew requested the current weather for Saltillo, Monterrey Center phoned Saltillo tower for the weather and received the weather information, however, tower did not mention the various fog banks around although the information was available. The crew thus never learned that there was a fog bank in their final approach course.
It is probable that the captain recognized early into the approach that they were too high for the approach, for example the rapid flaps change from 10 to 30 degrees suggests the captain was trying to lose height. The aircraft was twice as high as needed for a 3 degrees glide path. At 2.2nm before the runway threshold the aircraft was still at 6260 feet MSL or 1620 feet AGL. This corresponds to a false glideslope beam at 6 degrees.
Neither pilot became visual with the runway, it was the first officer who called out the runway was not in sight at 300 feet AGL.
The captain made a turn onto a heading of 160 degrees magnetic at about 1.3nm before the threshold which caused the aircraft to cross the localizer and impact ground 480 meters to the east of the runway center line.
Due to the issue with the DME the crew did not follow the DME arc procedure to intercept the ILS but followed a heading of 245 degrees. This resulted in the aircraft becoming too high on final approach.
Due to the captain's flight director bars being inoperative the workload of the captain increased while flying "raw data" due to increased monitoring of instruments necessary.
The SCT continued analysis that the fog bank in the final approach path was an important factor in the captain losing situational awareness.
The first officer's inexperience combined with the captain's considerable seniority may have created a situation called gradient of authority causing the first officer to self restrain on confronting the captain or simply prioritize tasks, for example trying to receive a landing clearance for a runway that was not in sight instead of attractign the captain's attention to the fact the runway was not in sight.
In addition that the loudspeakers in the cockpit were all open at considerable volume and the frequency was busy created a chaotic environment on the flight deck.
The entire final approach had been performed with the engines at idle thrust, then the acceleration of the engines was so abrupt that the right hand engine suffered compressor stalls causing surprise to the captain in addition to the flash emitted by the stalling engine illuminating the buildings and obstacles ahead of the aircraft.
The captain was not wearing his shoulder harness and died. The first officer was wearing his shoulder harness which saved his life.
This article is published under license from Avherald.com. © of text by Avherald.com.
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