Going Around: Bulgaria Air Charter flight 8115
It was 4am on the 16th of July 2018 when the Bulgaria Air Charter flight crew arrived at the airport, an hour before the scheduled 05:12 flight 8115 from Catania Airport (LICC) in Italy to Tarbes-Lourdes-Pyrénées Airport (LFBT) in France.
The aircraft was a McDonnell Douglas MD-823 registration LZ-LDM. The MD-80 series is a mid-range airliner easily recognisable by its low, arrow-shaped wings, rear-mounted engines and T-shaped tail. It was designed as a second generation DC-9 and in fact the first MD-80 was referred to as the DC-9-80. The MD-80 series was designed with a longer (“stretched”) fuselage, larger wings and more efficient engines: two turbofan engines mounted to the rear fuselage. With a higher maximum take-off weight, longer range and higher fuel capacity, the five-abreast coach seating made it a great choice for frequent, short-haul flights, allowing McDonnell Douglas to compete with the Boeing 737 Classic and the Airbus A320.
The crew that day was standard: captain, first officer and four cabin crew. The flight crew agreed that the first officer would be Pilot Flying and the captain as Pilot Monitoring (shown in the report as “Pilot Not Flying”). As the Pilot Flying, the first officer prepared the cockpit and the Flight Management System while the Captain did the exterior check and monitored the loading of the luggage. The passengers boarded on time.
The weather at Catania airport was poor, with intermittent low clouds, thunderstorms and rain. The METAR (Meteorological Terminal Air Report) for their destination of Tarbes-Lourdes-Pyrénées Airport showed light rain and showers in the area, with low clouds and winds of 15 knots gusting 25; however, the forecast for their arrival in two hours included thunderstorms and rain. They would need to check the weather again as they approached the airfield.
The flight was routine as they departed Catania and climbed to their cruising altitude of FL330 (33,000 feet). As they flew through the Barcelona region, shortly before starting their descent, the flight encountered cumulonimbus activity, dense, towering vertical clouds which mark severe weather, lightning, hail, high winds and turbulent updraughts which can fling an airliner through the air like a lightweight toy. The flight crew deviated around the cloud system as they began their descent.
The weather at Tarbes-Lourdes-Pyrénées Airport was described as “complicated”.
Precipitation is intensifying in the Southern part of the country. There have been reports of thunderstorms in the Tarbes area with peak values at flight level FL350. The wind power at FL50 flight level is heading north at a speed of about 5kts. It should be noted that account is not taken of the possible gusts of wind in the information.
The map showed thunderstorms with maximum values between 35,000 and 40,000 feet, which implies more advanced and more intense storms. The airfield reported unstable winds and heavy rain with a surface wind varying between 100° and 260°. Lightning lit the skies, with three lightning strikes directly over the airfield. The rain was coming down at an average of 60mm an hour, with 78mm/hour for about twenty minutes. For context, “heavy rain” is defined as 4mm/hour with 50mm/hour described as “violent showers”.
The METAR for the airfield was as follows:
METAR LFBT 160700Z 25007KT 220V290 9000 RA VCTS FEW011/// SCT034/// BKN045/// ///CB 17/16 Q1018 TEMPO 28020G40KT 1300 TSRA BKN007 BKN040CB=
Rain and thunderstorms, with layers of broken clouds from 4,500 feet down to 700 feet. The wind was still shown as 20 knots at 280° with gusts up to 40 knots.
The air traffic controller at Toulouse Coordination agreed to assign the aircraft a lower flight level, offering them FL80 to the waypoint TEPTI. As they reached the waypoint, the Tarbes-Lourdes-Pyrénées approach controller asked the flight to descend following the ILS (instrument landing system) for approach procedure Zulu for runway 20.
The captain, in his role as pilot monitoring, asked for “confirmation of the permission” and the latest weather conditions. The approach controller offered the latest information: visibility 5km with rain storms, clouds few at 1,900 feet, scattered at 2,500 feet and overcast at 4,300 feet. The flight crew acknowledged the weather and asked about the latest wind direction, which was reported at 190° at eight knots.
The approach controller asked the flight crew to confirm that the aircraft was deviating to avoid the cumulonimbus activity, which the captain confirmed, saying they would maintain course 290° for another five nautical miles.
The flight experienced moderate turbulence and strong icing conditions as they descended through icing conditions to FL100 (10,000 feet). As the aircraft broke free of the dense clouds, the flight crew began the final preparations and briefings for the landing.
The slats and flaps were extended to 11°. The aircraft maintained FL80 for about 40 seconds and then continued to descend following the ILS approach Zulu.
They were able to see the ground through the scattered clouds and as the first officer turned left to intercept the ILS for runway 20, they had visual contact with the runway which was maintained throughout the approach. As the aircraft descended with a course of 204°, the flight crew reported intercepting the ILS for runway 20. The approach was stabilised as they descended to 500 feet. The first officer, as pilot flying, switched off the autopilot to continue the approach manually. Up until this point, the flight was normal and in full compliance with the airline’s standard operating procedures.
The landing gear, flaps and slats were extended. Approach asked the flight crew to change frequency to Tower.
The flight crew reported full interception of the ILS. The Tower controller asked them to confirm reading four nautical miles from the runway and gave the latest runway information: wind at 200°/10 knots, runway wet.
The aircraft was fully configured for landing in a stabilised approach at 2,200 feet above mean sea level with a calibrated airspeed of 140 knots. The airfield elevation is 1,259 feet above sea level. The autopilot was on and the auto-throttle was engaged in SPEED mode.
The auto-throttle allows the Pilot Flying to control the power generated by the engines by specifying the effect that they want, rather than a specific level of thrust. In THRUST mode, for example during take-off, the auto-throttle maintains a high power setting to allow for the aircraft to climb while increasing speed. If the auto-throttle is in THRUST mode, the aircraft speed is controlled by pitch.
In SPEED mode, a target speed is set and the auto-throttle maintains the power needed to achieve and maintain that speed. If the aircraft configuration changes, the auto throttle will automatically adjust the power in order to maintain the speed selected.
At this point, the aircraft was perfectly positioned for its landing on runway 20.
The first officer, as Pilot Flying, disengaged the autopilot with the auto-throttle in SPEED mode set for 140 knots. As he began manually flying the aircraft, the flight encountered strong gusting winds and heavy rain and the flight was blown off course. The first officer struggled to main control but the aircraft lost height as it deviated to the left.
The captain immediately took control of the aircraft and attempted to correct their course by banking to the right. At 250 feet above the ground, the aircraft began to sink below the glideslope. The Captain, having taken over as Pilot Flying, raised the nose to correct the loss of height but the auto-thrust, still in SPEED mode, struggled to maintain 140 knots after the pitch had increased. The aircraft continued to gently sink under the glideslope.
The aircraft continued to lose height. At 80 feet above the ground, the Captain pitched up aggressively as he shut down the autothrottle. He managed to halt the MD-80’s descent at 46 feet above the ground, still 460 meters from the runway threshold but now the aircraft was starting to drift to the right.
It continued level for about ten seconds as the speed dropped from 136 to 128 knots. The aircraft crossed the threshold of runway 20 at 37 feet over the ground with a heading of 196° and a calibrated airspeed of 129 knots, positioned just to the right of the centre-line. The captain attempted to bank left to line up with the runway; however at no point had he actually increased the engine power.
The first officer, described by the report as “extremely concerned”, shouted out to go around. About five seconds later, having travelled a further 350 metres (1,150 feet) along the runway, the captain called out GO AROUND and began to pitch up. He pressed the TO/GA (Take-Off/Go-Around) button, which helps to quickly configure the aircraft for climbing away from t he runway and started to follow the flight director arrows for the go-around.
However, he had forgotten or somehow not noticed that the auto-throttle was off. He did not make any power adjustments as he began to climb away.
By now, the MD-80 had travelled 830 metres (2,700 feet) from the moment when the captain disconnected the auto-throttle (at 40 feet above terrain and 480 metres before the threshold) to the point where he called for a go-around. Throughout this, the aircraft was close to the critical level of attack with the engines set just above idle.
I’ve been focused on the captain but the first officer, having taken the role of Pilot Monitoring, also did not ever check the position of the throttle controls or notice the deteriorating speed. Even after the captain called for a go-around, the first officer didn’t check or better yet, adjust the engine throttles for go-around power.
The MD-80 series aircraft has slightly different aerodynamic characteristics as a result of the engines at the back and the T-shaped tail. The engines set on the rear meant that the air flow would tear off later than in an aircraft with engines installed under the wing, as a result of the cleaner surface. In this situation, with critical angles of attack at low power, the aerodynamics of the aircraft is a key reason why they managed to stay in the air.
However, the T-shaped tail means that the tail panels can be affected by wake from the wing at high angles of attack, which quickly leads to a deep stall. The report recreated the situation:
The deep stall is characterized by two consecutive, energetic pitch-ups – two energetic pitches that ultimately lead to uncontrollable aircraft in the second pitch-up. At both the pitch-ups, the aerodynamic focus of the airplane moves and the airplane decreased, partially recovered for a short time, and then decreased again and completely lost its longitudinal stability.
Basically, when the aircraft first pitches up with a pitch angle of about 20°, the flow wake is spread across the wing and the aircraft can still be controlled. With “extreme and vigorous rudder commands”, the aircraft can continue to fly horizontally for a short time without sinking. Then a second pitch-up occurs as the horizontal stabiliser, which is already in a highly disturbed flow, stops having any effect and the aircraft goes into a deep stall which would not be recoverable from at low height.
At sixty-six feet above the ground, the captain called out for flaps. The first officer retracted the flaps from 40° to 11° in a single motion, followed by retracting the landing gear, setting the go-around altitude and selecting a target speed of 180 knots.
Although he had not increased the engine power, the aircraft’s height above the ground increased from 33 feet to 107 feet. The first officer reported “positive rate” (of climb).
His rapid retraction of the flaps had reduced the drag. The slats were partially retracted at the same time, which increased the angle of attack and allowed the aircraft to continue forward in horizontal flight. This caused the drag to increase again. There was not enough thrust to compensate and the MD-80 reached the critical angle of attack, with the wake almost all over the wing, although it did not exceed it, as shown by the aircraft rising (I hesitate to use the word “climbing”) to 107 feet.
The landing gear took about six seconds to retract, by which time the aircraft was travelling 116 knots and was pitched nose-up to 15°.
As the aircraft sank to 50 feet above the ground, the first officer disarmed the spoilers and suddenly noticed that the throttles were not in the correct position for a go-around. He asked the captain if he had put the engines into TO/GA mode. The captain told him to push the throttle forward — this was clearly not a good time for discussion. The first officer aggressively pushed the throttle controls forward to the maximum position.
By now, the pitch had reached 19.8° with an angle of attack was 38.6° and their speed had dropped to 116 knots at 49 feet above the ground. The aircraft had travelled another 850 metres along the runway, meaning that it had travelled a total of 1,680 metres (5,500 feet) at a critical angle of attack.
The full length of the runway was 2,993 metres (9,821 feet).
The parameters of both engines quickly reached maximum values. The captain quickly intervened and corrected the engine power to the TO/GA setting.
Once they’d achieved 342 feet above the ground at an airspeed of 141 knots, he reduced the engine throttles to normal climb and banked left for a course of 080°. The final stage of flaps was retracted, the auto-throttle was engaged and the auto-pilot turned on. The flight crew performed a holding pattern and agreed to divert to their alternate airport. The flight landed at Toulouse and then returned to Tarbes-Lourdes-Pyrénées Airport a few hours later, once the weather had cleared.
The captain did not consider it necessary to report the incident to his management. However, the controllers on duty absolutely did consider it necessary to escalate the issue, reporting that those on shift were “terrified” by the approach and had been expecting the plane to crash at any moment. The dispatcher filed a written report which described the incident in detail.
One A/C MD82 of a Bulgarian company was performing an ILS approach for RW 20 around 09:30 AM, local time. The weather was stormy, very rainy, but the wind was weak. Given the meteorological conditions, we expected the plane, we expected to see it coming out of the cloud layer, and finally, we saw its lights being too low and too far. Thus, the plane would land at about 500 m before the threshold of the runway and to the extreme left of the runway (probably wind shear). The plane tried to return to the RWY axis, and its wings were low, over the threshold of the Runway, it retracted the landing gear to make a Go-Around.
Then the plane quickly came with a high pitch in [an] attempt to climb, but the speed was low. The aircraft flew over the entire runway with abnormal high pitch, with a tail at 20 m from the ground, unable to climb and even lost some altitude. Total horror, we almost saw the plane collapsing at the end of the runway, with the same configuration as Airbus in Hamsheim. Then, at the end of the runway, and with this high pitch, it managed slowly to climb, flew very close to a hill, turned left, and was radar vectored to head North again. The plane then went to Toulouse, where it landed and in a few hours returned to us again.
The local Flight Safety Unit immediately prepared an official report for the French aviation investigation bureau, the Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation Civile (BEA). The BEA classified the case as a serious incident and passed it to the Bulgarian Aircraft Accident Investigation Unit (AAIU).
The cockpit voice recorder had been overwritten as the flight crew had not made any report and had not removed it. However, the aircraft’s digital flight data recorder confirmed the sequence of events as described by the controllers.
The report concludes with a probable cause of “pilot mistakes”.
On the grounds of the analysis made the Commission points out that the serious accident is the result of the following cause:
Pilots mistakes in crew coordination and in-flight technology in bad weather conditions during the landing approach and the go-around procedures at the Tarbes-Lourdes-Pyrénées Airport, France.
Taking into account the causes of the serious incident and the deficiencies found in the investigation, the Commission recommends that the following measures should be taken to ensure the flight safety:
* BG.SIA-2018/08/01. AO “Bulgarian Air Charter” must organize and carry out additional theoretical CRM training course, and the A/C crewmembers, who have caused the serious incident, must undergo a flight simulator check.
* BG.SIA-2018/08/02. During the next flight simulator training session, all MD-82 pilots of AO “Bulgarian Air Charter” to include an exercise with similar conditions for flight performance as in the case of the serious incident.
You can read the full report on the AAIB site.
This incident was also covered by AVHerald and I was deeply amused by this comment by “The Wrench”:
I’m just surprised the report doesn’t say anything about the hand of god reaching down from the clouds to hold the little airplane airborne until the mortals within got their s**t together.
Well, it was Lourdes, after all.
I would have liked to have seen more about the Cockpit Resource Management but I suppose without the CVR, it is hard to do a real analysis of the crew actions and interactions. The investigators also clearly struggled when writing a section about the decisions which saved the incident from becoming a fatal accident. The crew were flying thirty-three feet above the ground, travelling 116 knots with a pitch of 20° and no power, hoping to go around. It’s hard to work out how, having ended up in this position, one could highlight how their final choices may have increased the chances of survival.
The controllers were right to be horrified and that captain may not have had an ounce of CRM but he kept that MD-80 flying along the entire length of the runway. If I’m honest, that must have been one hell of a slow and low flight to watch.