RafAvia SF34 at Savonlinna on Jan 7th 2019, runway excursion on landing
Last Update: December 10, 2019 / 22:01:29 GMT/Zulu time
Incident Facts
Date of incident
Jan 7, 2019
Classification
Incident
Cause
Runway excursion
Airline
RafAvia
Departure
Riga, Latvia
Destination
Savonlinna, Finland
Aircraft Registration
YL-RAF
Aircraft Type
SAAB 340
ICAO Type Designator
SF34
Airport
Savonlinna Airport, Savonlinna
Airport ICAO Code
EFSA
The aircraft was about to perform scheduled flights out of Savonlinna for Flexflight. The morning flights of Flexflight had to be cancelled as result.
Finland's Onnettomuustutkintakeskus (Accident Investigation Board AIBF) dispatched an investigation team of 5 investigators on site.
Finavia, the airport operator, reported the runway had been cleared on a width of 37 meters, the runway surface was covered with dry snow of 8mm/0.3 inches, the braking action was measured to be beter than medium. Snow banks at the edges of the runway rose to about 40cm (15.7 inches).
On Jan 8th 2019 Finland's Onnettomuustutkintakeskus reported the weather conditions were not exceptionally bad, the runway condition was sufficient for landing. Based on the ground tracks the aircraft touched down to the left of the runway center line and drifted off the runway coming to a stop about 20 meters to the left of the runway edge. There were no injuries, the aircraft sustained damage to both propellers, landing lights and tyres. The onsite work has been completed.
On Dec 10th 2019 Finland's Onnettomuustutkintakeskus (AIBF) released their final report concluding the probable causes of the accident were:
- The operating licences and air operator licences issued by the EU Member States’ aviation authorities do not guarantee constant and uniform safety levels among air carriers.
Conclusion: In addition to operating licences and air operator licences, competitive tendering for air services requires other practices to verify the safety of airlines.
- While the EU’s regulations have aimed at ensuring the most open participation in tendering, they may result in overlooking the safety of aviation as one criterion in tendering.
Conclusion: The interpretation of regulations should not result in a situation where qualitative criteria in competitive bidding are discarded because of tendering rules, the risk of challenging a decision or the desire for an uncomplicated process.
- The purchaser organising the public tender for air services will not necessarily impose any safety-associated criteria because of being cautious about breaking EU competition rules and the court processes launched by losing bidders. Often the price and on-time performance are the tender criteria.
Conclusion: Tenders for air services may not necessarily assess the operators’ safety records at all. Present air service competition rules do not encourage operators to invest in safety.
- Purchasers of air services do not have suitable and straightforward indicators to assess air carrier safety. Clients and purchasers may also include those that are not deeply familiar with the aviation branch.
Conclusion: It is difficult for purchasers to reliably compare the safety of air carriers.
- The airline had not completely complied with its own safety management system. Oversight authorities do not always detect the difference between the safety management that operators promise to follow and their real-world practices.
Conclusion: Authority oversight does not always extend to the implementation of operators’ safety management systems or to actual practices.
- At no time did the flight crew consider aborting the landing.
Conclusion: A go-around is always the safe option if the preconditions for landing are not met or if a safe landing cannot be achieved.
- The airline’s operational manuals (OM-A and OM-B) were inconsistent concerning maximum crosswind components. The instructions were difficult to follow in practice.
Conclusions: Manuals must be consistent in all respects and user-friendly during the different stages of the flight.
- Regardless of the alert to the Emergency Response Centre, no information about the airliner accident was relayed to the region’s divisional officer on duty because, owing to the situation assessment, there was no need to deploy rescue service units.
Conclusion: The region’s divisional officer on duty responsible for rescue operations must be sufficiently informed of an accident occurring in the region, even if the situation did not require deploying rescue service units. The situation may change from the onset, requiring the commencement of rescue actions.
- The Cockpit Voice Recorder had not recorded anything from the flight in question, and the earlier recordings that were retrieved from its memory were of extremely poor quality. The recording quality of the FDR, when compared to modern recorders, was poor. The magnetic tape of the FDR was worn, which caused defects in the recording.
Conclusion: The purpose of flight recorders is to make it easier to investigate accidents and incidents so as to improve safety. Aircraft should carry recorders that meet modern-day recording capacity and reliability requirements.
The AIBF described the sequence of events:
The runway maintenance vehicles exited the runway at 05:34 and the runway friction measuring vehicle entered the runway. The friction measuring device displayed the average friction for the different sections3 of the runway: A:0.29 B:0.22 and C:0.23, in which A corresponds to “medium to poor” and B and C to “poor” estimated runway friction.4 The driver reported the results to the AFIS officer at 05:42. According to the inspection, the cleared width of the runway was 37 metres, the estimated runway friction for each third of the runway was poor5, and there was a 4 mm layer of dry snow covering the entire cleared area. The critical snowbanks were 40 cm high and were four metres inside of the runway edge lights. Friction was also poor on the taxiway and the apron. The AFIS officer reported the runway conditions to the pilots of the positioning flight.
At 05:43 the captain of the positioning flight reported being established on the ILS localiser. The AFIS officer said that wind was 220 degrees at five knots and that runway 12 was free. The pilots used 20 degrees flap during the approach. According to the flight data recorder the approach was stable until the threshold. During the final approach the pilots saw the approach and runway lights well. Owing to the icing conditions they intended to use an airspeed which was 10 knots higher than the Aircraft Operations Manual’s prescribed minimum approach speed. At the threshold their speed was 126 knots, while the approach’s target speed was 120 knots.
However, the airspeed at the touchdown zone markings was 123 knots. Contrasting from normal, the aircraft floated close to the surface for 6–7 seconds before touching down. The flight crew did not consider aborting the landing, i.e. going around. Following the level flight the captain steered the aircraft toward the ground at a fairly high vertical speed. A person working at the airport saw that the aircraft was still airborne when passing taxiway A and that it very rapidly lost altitude after it. The aircraft touched down at 05:50, approximately 307 metres after the optimal touchdown point, on the left side of the runway. At touchdown the airspeed was 109 knots, which corresponds to the 110 knot target speed.
Judging by the marks on the snow the left main landing gear hit the left snowbank on the uncleared area. The nose gear touched the runway, following which the left main gear became airborne for a moment and the right main gear touched the ground. The left main gear touched down again. After having travelled approximately 100 metres from the first touchdown point the aircraft’s nose gear and the right main landing gear moved outside the cleared runway area.
The aircraft was tracking towards the left, away from the direction of the runway. The pilots tried to turn the aircraft back towards the runway centreline. According to the markings the aircraft began to turn and started to skid sideways outside the cleared area of the runway.
When the left main gear hit a high snowbank outside the runway, the aircraft began to turn more sharply to the left. The left engine stalled when snow entered its air intake. The pilots did not deploy reverse thrust. The right main gear knocked one runway edge light over. The aircraft stopped in half-metre deep snow outside the runway, at a 110 degree angle in relation to runway 12.
The aircraft received substantial damage.
The AIBF added background information:
Runway friction was measured again at 07:52, after the occurrence. This was done in accordance with instructions without any additional runway maintenance action. At the time of the occurrence, and following it, it had been snowing. At the time of measuring the snow layer on the runway was estimated to be 8 mm. This is why the estimated runway friction had probably degraded from the time when the aircraft landed. The measured friction data averaged at A:0.31 B:0.31 ja C:0.30. The estimated runway friction was medium to poor for each third of the runway.
The minimum required cleared width of the runway for a Saab 340 aircraft is 30 m15. While poor estimated runway friction is permitted, the commander of the aircraft must ensure that wind conditions make it possible to carry out a safe landing.
Possible sensory illusions during the approach and landing
Sideways blowing snow may cause sensory illusions for pilots. This has been addressed in many books16 on aviation physiology, and aircraft manufacturers’ manuals also warn of the phenomenon. When snow is blowing sideways, a pilot may see an illusion when approaching the runway where the aircraft’s track is deviating from the intended track or the runway bearing. The illusion is stronger at nighttime when the aircraft’s landing lights are on.
For example, if the pilot makes a control input that causes the aircraft to level out over the runway at a more gradual approach slope, touchdown occurs farther down the runway. If there are no runway centreline lights the pilot may get a sensory illusion of sideways motion. Dimming the runway edge lights only further intensifies the phenomenon.
When the illusion occurs the pilot, in sideways blowing snow, experiences a sideways motion of the aircraft which, in reality, is not happening. The snowflakes illuminated by the landing lights take the pilot’s attention away from the runway edge lights. In such a case there is the danger of the pilot compensating for the illusion by making an unnecessary corrective control input. The control input may result in touching down at the side of the runway.
The Aircraft Operations Manual17 states that there are no absolute rules for controlling the situation. The manual recommends that pilots recognise the situations in which sideways blowing snow or rain may generate sensory illusions. Pilots are also recommended to avoid using taxiing lights and, when possible, to also turn off the landing lights. Eyes must look straight ahead during touchdown and the landing roll. The aircraft is kept in the correct position with the help of the runway lights.
According to the captain, the landing and taxiing lights were on during the final approach and landing. He felt that the aircraft’s landing lights are too dim.
The AIBF analysed:
During the positioning flight to Savonlinna on 7 January 2019 the weather conditions were normal for wintertime. The runway had been cleared of snow but the clearance had to be repeated to achieve better runway friction. The aircraft had to wait for the landing in the holding pattern, and the landing was delayed. At the time of the landing it was dark, a crosswind was blowing, it was snowing and the runway was slippery. The landing conditions were communicated to the flight crew clearly.
The landing conditions met the OM-B’s requirements. Correspondingly, the air carrier’s OM-A says that if the reported runway friction is poor, crosswind landings are prohibited. The preconditions of crosswind landings are defined in several different manuals which the pilots must follow.
Landing
The landing proceeded normally until the aircraft passed the threshold. After that, the flight attitude became unstable. At the final phase of the landing the aircraft floated close to the surface for 6–7 seconds before touchdown, following which the touchdown point moved farther down the runway than normally. Extra airspeed after the threshold partly contributed to this. The captain did not notice that the aircraft began to veer off the runway centreline. He steered the aircraft toward the ground at a fairly high vertical speed. At that time the aircraft was already over the snowbank at the edge of the cleared area of the runway. Despite the pilot’s corrective control actions the aircraft completely veered off the runway into the snowbank. At no time did the pilots consider aborting the approach or landing, i.e. going around. The length of the runway was not a limiting factor for the landing.
No single factor explains the failed landing. It is known that the following factors, combined, stressed the flight crew’s performance in this situation: the crew’s shift had already begun during the night, and, at the time of the landing, it was dark and a crosswind was blowing, and snow was drifting in the wind. Furthermore, there was only a little time before the next scheduled take-off and the passengers were already waiting. The airline manuals’ instructions for the preconditions of landing differed from those of the aircraft manufacturer’s manual.
Hence, they were difficult to follow operationally. On the other hand, most of the aforementioned factors are part and parcel of normal wintertime operations. It is also known that working at night especially stresses older employees. The captain of the accident flight was 61 years old. Flying low and level over the runway may have made it more difficult to precisely determine the position of the aircraft.
The lack of the cockpit voice recording significantly hampered the investigation of the sequence of events, especially, regarding multi-crew cooperation. The recorder had been replaced with a new type but the recording system operated poorly. The recordings from previous flights were of extremely poor quality and contained noise. The functioning of the recorder had probably not been checked before take-off, and it recorded nothing from the flight. Checking the functioning of the recorder is one of the pre-flight checks.
The flight data recorder (FDR) worked properly during the flight, but its tape was worn which caused defects in the recording. The FDR model was over 30 years old and its sample rate and recording capacity is more limited compared to modern recorders. However, the recording provided a sufficiently accurate picture of the sequence of events for the investigation. Using obsolete technology or worn, or non-functioning, recorders makes it more difficult to ascertain the course of events and, on the other hand, may disguise essential factors for the improvement of safety.
The airline had already experienced incidents in the past. According to the Latvian CAA there had been shortcomings in the company’s flight safety. The air carrier had not appropriately reported all incidents. The company’s action had not completely complied with its own safety management system.
Oversight authorities do not always detect the difference between the safety management that operators promise to follow and their real-world practices. The authorities’ safety audits focus on safety management system documents; the assessment of actual operations has been transferred to companies’ self-monitoring. This being the case, maintaining and improving the operator’s flight safety is largely left to its own interests.
Related NOTAMs:
SWEF0001 EFSA 01070552
(SNOWTAM 0001
A)EFSA
B)01070552 C)12 E)37 F)4/4/4 G)8/8/8 H)2/2/2
J)40/4LR
T)RWY 12 CONTAMINATION 100 PER CENT
OPR SIGNIFICANT CONT F)4 G)8 H)2/2/2
TWY A F)4 H)1
ALL APN F)48 H)1)
B0059/19 NOTAMN
Q) EFIN/QMRLC/IV/NBO/A /000/999/6157N02857E005
A) EFSA B) 1901070400 C) 1901071200 EST
E) RWY12/30 CLSD
B0068/19 NOTAMR B0059/19
Q) EFIN/QMRLC/IV/NBO/A /000/999/6157N02857E005
A) EFSA B) 1901071135 C) 1901071700 EST
E) RWY12/30 CLSD
Metars:
EFSA 070520Z AUTO 23006KT 180V270 9999 -SN OVC005 M01/M02 Q1009=
EFSA 070450Z AUTO 23005KT 180V270 4300 -SN OVC006 M01/M02 Q1010=
EFSA 070350Z 22005KT 170V260 2500 SN BKN005 OVC015 M02/M02 Q1010=
EFSA 070320Z 21004KT 180V260 3000 -SN BKN006 OVC017 M02/M02 Q1011=
EFSA 070250Z AUTO 22004KT 160V300 3400 -SN OVC006 M02/M03 Q1011=
EFSA 070220Z AUTO 22004KT 140V280 1700 -SN BR OVC004 M02/M03 Q1012=
EFSA 070150Z AUTO 22006KT 170V280 4200 OVC004 M02/M03 Q1012=
EFSA 070120Z AUTO 21005KT 170V280 6000 OVC004 M02/M03 Q1012=
EFSA 070050Z AUTO 20005KT 140V250 4900 BR OVC003 M03/M03 Q1013=
EFSA 070020Z AUTO 21005KT 150V260 4800 BR OVC004 M03/M03 Q1013=
Incident Facts
Date of incident
Jan 7, 2019
Classification
Incident
Cause
Runway excursion
Airline
RafAvia
Departure
Riga, Latvia
Destination
Savonlinna, Finland
Aircraft Registration
YL-RAF
Aircraft Type
SAAB 340
ICAO Type Designator
SF34
Airport
Savonlinna Airport, Savonlinna
Airport ICAO Code
EFSA
This article is published under license from Avherald.com. © of text by Avherald.com.
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