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L410, Isle of Man, 2017

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On 23 February 2017, a Czech-operated Let-410 departed from Isle of Man into deteriorating weather conditions and when unable to land at its destination returned and landed with a crosswind component approximately twice the certified limit. The local Regulatory Agency instructed ATC to order the aircraft to immediately stop rather than attempt to taxi and the carrier’s permit to operate between the Isle of Man and the UK was subsequently withdrawn. The Investigation concluded that the context for the event was a long history of inadequate operational safety standards associated with its remote provision of flights for a Ticket Seller.
Event Details
When February 2017
Actual or Potential
Event Type
Human Factors, Loss of Control, Weather
Day/Night Day
Flight Conditions IMC
Flight Details
Aircraft LET L-410/420
Operator Van Air
Type of Flight Public Transport (Passenger)
Origin Isle of Man Airport
Intended Destination Belfast/George Best Belfast City Airport
Actual Destination Isle of Man Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed Yes
Flight Phase Landing
Location - Airport
Airport Isle of Man Airport
Tag(s) Approach not stabilised,
Inadequate Aircraft Operator Procedures,
Ineffective Regulatory Oversight,
Air Turnback,
Approach Unstabilsed at Gate-no GA,
Deficient Crew Knowledge-performance
Tag(s) Inappropriate crew response - skills deficiency,
Ineffective Monitoring,
Plan Continuation Bias,
Procedural non compliance,
Ineffective Monitoring - SIC as PF
Tag(s) Environmental Factors
Tag(s) Significant Crosswind Component
Tag(s) Strong Surface Winds
Damage or injury No
Causal Factor Group(s)
Group(s) Aircraft Operation
Safety Recommendation(s)
Group(s) Aircraft Operation
Investigation Type
Type Independent


On 23 February 2017, a Let 410 (OK-LAZ) being operated by Van Air for an Isle of Man-based Ticket Seller called ‘Citywing’ on a scheduled passenger flight from Isle of Man to Belfast City was unable to land at its destination due to adverse wind and turbulence. It returned to the Isle of Man where, after a day ILS approach completed in VMC, the crew were observed to just manage to retain sufficient control of the aircraft to make a landing in similar extreme wind conditions, in this case with gusts to over 60 knots and with a significant crosswind component. As the aircraft attempted to taxi clear of the runway, ATC ordered the crew to ‘Hold Position’ because of a ‘direction from the Isle of Man CAA’ and the aircraft was stopped into wind. RFFS vehicles which had been on standby for the landing were then positioned around the aircraft to provide some protection from the wind pending tie down and the passengers were taken by bus to the Terminal.

The aircraft tied down just clear of the runway after being required to stop taxiing. [Reproduced from the initial Report]


A Field Investigation was carried out by the UK AAIB on behalf of the Isle of Man Government. Relevant recorded data from both the FDR and 30 minute CVR were downloaded.

It was noted that the 51 year-old Captain, who was a Hungarian national, had 7,800 total flying hours of which 2,200 hours were on type. The First Officer, who was PF for the flight was a Czech national, who was also the Deputy Flight Operations Manager for Van Air, had 1,052 total flying hours of which 509 hours were on type.

What Happened

It was established that the two pilots were based locally and had been rostered to report 30 minutes before the scheduled departure time of an early morning flight to Belfast City after which their next sector was to be a return flight to the Isle of Man with a scheduled time of arrival 1 hour and 35 minutes later. Both had arrived 45 minutes prior to STD and on arrival had been able to download TAFs and METARs for the Isle of Man, Belfast Aldergrove and Dublin, plus METARs only for Belfast City and Londonderry and a TAF only for Blackpool. A warning of north-westerly gales expected to affect the Isle of Man (IOM) from about half an hour after the scheduled return had been issued by the insular Meteorological Office and was also available to the crew at this time. The IOM TAF seen by the crew was the one valid from 0600 -1500 and gave the surface wind as soon veering to 310º and temporarily subsiding to a mean speed of 17 knots before beginning to increase to 33 knots gusting to 46 knots from 45 minutes after the scheduled departure time from IOM. The only wind limit considered by the crew in light of this information was the Van Air OM maximum wind speed of 45 knots from any direction for all ground manoeuvring. Crosswind components for takeoff and landing on the runway in use, runway 26, were not considered. It was noted that, somewhat unusually for most smaller European airports, the crew could, had they wished, discussed the weather outlook with a duty forecaster based at the airport.

It was also noted that a replacement IOM TAF had been issued at 0800 for the remainder of the period to 1500 that gave the surface wind for the two hour period which included the time at which the returning aircraft landed back at the Isle of Man as from 310° with a mean speed 36 knots, gusts to 55 knots and the likelihood of moderate rain showers, but this was not seen by the crew and the aircraft left the stand on its delayed departure soon afterwards.

In respect of a pre-flight assessment of the destination weather where runways 04 and 22 were available, the METAR seen by the crew during their pre-flight preparations gave the surface wind as from 230º at 9 knots. As no TAF was reported to have been available for Belfast City (BHD), the crew stated that they had selected Belfast Aldergrove (BFS) and IOM as their alternates airports noting that at the former, the wind was forecast to be from 340º with a probability that it would temporarily increase to a mean speed of 33 knots but that runway 35 was available there. However, although the crew stated “they considered BFS to be their first alternate” they had “created their Operational Flight Plan (OFP) to show IOM as the only alternate”. The Ticket-Selling company for the flight, Citywing, “stated afterwards that BFS was its preferred commercial alternate, followed by IOM and then Dublin”. It was found that although the first TAF of the day for BHD had not been issued until after the time of scheduled departure from IOM, it did not appear, despite the almost one hour departure delay, to have been seen by the crew. It did indicate that the crosswind component for either direction of the only available runway would be close to 35 knots at times - in contrast to the BHD METAR seen earlier by the crew which had given the surface wind speed as of almost no operational consequence. It was noted that Glasgow Prestwick, where a runway direction close to the forecast wind direction and with much lighter forecast windspeeds than IOM, was not considered as a potential alternate.

The departure to BHD was delayed for just over an hour because the forecast decline in the strong westerly surface wind speed did not occur as soon as had been expected and had been gusting up to 10 knots above the 45 knot ground manoeuvring speed limit. At the time of the eventual takeoff, the wind was broadcast by ATC as being from 290º at 21 knots gusting to 41 knots and the takeoff was uneventful.

En route, the crew copied the BHD ATIS which stated that Runway 22 was in use with the latest surface wind as 320º at 25 knots gusting to 40 knots and the lowest cloud at 900 feet aal. When subsequently contacting BHD ATC, radar vectoring for an ILS approach to runway 04 was offered with the wind direction unchanged but the speed slightly increased. ATC were informed that one approach would be made but a go around would follow “if the approach was not stable”. The crew stated that they had experienced continuous moderate turbulence during the latter part of this approach but had “judged that the aircraft operator’s stable approach criteria were met until the aircraft passed over the runway threshold, when turbulence de-stabilised the aircraft and they initiated a go-around. ATC confirmed that the aircraft had gone around from approximately 20 feet above the runway and were subsequently advised that a second approach would not be made and that the aircraft would return to IOM. No mention was found from the CVR data of any discussion of a possible diversion to BFS where the available runway 35 would have offered more favourable relative surface wind conditions. The Captain stated subsequently that following the go-around, he had not asked ATC about the latest conditions at BFS, or whether other aircraft were landing there because he judged “the same sort of wind was prevailing at both BFS and IOM”.

After levelling at FL070, the IOM ATIS was copied. This gave runway 26 in use, that it was wet and gave a surface wind as from 290º at 28 knots. The First Officer, remaining as PF, briefed for a flap 18º approach, a target Vref of 105 knots and noted “a slightly right crosswind” and was subsequently recorded as remarking that the wind would be “not so challenging” as it had been at BHD. However, soon after this ATC advised that the surface wind was now from 310º at a mean speed of 41 knots and ranging between 22 knots and 53 knots and asked if they wished to make an approach to which the Captain replied “of course”. The CVR data showed that “there was no discussion between the pilots regarding the change to the wind before the aircraft began descent in preparation for its approach at IOM” and without any further discussion, radar vectoring for an ILS approach to runway 26 was accepted with the First Officer continuing as PF.

Shortly before vectoring the aircraft onto the ILS, ATC advised that the surface wind was from 310º with a mean speed of 43 knots and ranging from 23 knots and 63 knots. Once the aircraft was established on the runway 26 ILS, a landing clearance was given with wind advised as from 300º with the mean speed 41 knots and varying between 31 knots and 63 knots. Whilst this message was being received, the first of three EGPWS Mode 5 ‘Glideslope’ cautions was annunciated to which the PF immediately declared “1,000 feet stabilised”. The Captain stated that the runway had been in sight at 600 feet and approximately 35 seconds before the aircraft touched down ATC provided a final wind check of 300º at 48 knots varying between 32 knots and 63 knots.

As ATC were “concerned for the safety of the aircraft and its occupants when it landed”, two RFFS vehicles were deployed facing towards the runway, approximately 200 metres from the Touchdown Zone (TDZ). As the aircraft made its approach, ATC, aware of the Van Air maximum ground operation limit and of a previous weather-related Serious Incident when another Van Air Let 410 had been blown onto its wingtip while taxiing in surface winds exceeding that limit, “discussed the situation with the Isle of Man Civil Aviation Administration” (CAA).

The Investigation found four RFFS and two ATC witnesses who concurred that “as the aircraft crossed the threshold it seemed unstable and it rolled considerably, causing the tip of the left wing (the downwind wing) to tilt down until it seemed in close proximity to the runway, before the wheels made first contact (and that) the aircraft then bounced and rolled left again before touching down for a second time, on all three wheels”. These witnesses also stated that “after travelling along the runway for approximately 20 metres, the right main wheel was seen to lift off the ground and nearby RFFS witnesses estimated the left wingtip rolled to within one metre of the runway surface”. Concurrent CVR data indicated that the crew had been aware of this roll because, approximately nine seconds after touchdown, the PF was recorded as saying “ailerons… good… too much roll” although the Captain stated that he had thought that all the wheels remained on the ground and that the aircraft had responded to appropriate aileron control and that “he had no concern that the wingtip or the propeller might have been close to the ground”.

After landing the commander took control and the First Officer said “taxi carefully with the wind” and ATC then gave the surface wind as from 300º at 47 knots and varying between 32 knots and 63 knots and asked if they wished to taxi or to hold on the runway. The crew responded with “we will try and taxi and if we can make it we will vacate, otherwise we need to leave the aircraft here” and accepted taxi instructions to the terminal but 45 seconds later, as the aircraft was leaving the runway, ATC transmitted “direction from Isle of Man CAA, hold position” and the crew complied.

FDR data was found to show that the aircraft had passed 1,000 feet agl on the IOM approach stable at approximately 120 KIAS and descending steadily at around 1000 fpm. However, over a period of about 40 seconds beginning whilst the aircraft was still in IMC at approximately 850 feet agl, this descent had reversed into a climb which reached 950 feet agl before descent was re-established. During this excursion, airspeed was recorded as fluctuating between 113 KIAS and 146 KIAS. Then, passing 500 ft agl, the aircraft rate of descent had reduced to approximately 440 fpm and the airspeed had dropped to 107 KIAS before the aircraft had levelled at 390 feet agl. Thereafter, a generally increasing trend in airspeed was recorded as descent towards the runway was re-established. FDR data showed that airspeed during this final descent towards the runway had fluctuated between 125 KIAS and 148 KIAS.

It was noted that when asked if he had considered taking over as PF for the approach to IOM after the wind speed had increased significantly, the Captain had stated that there would have been no advantage to him doing so despite his greater general and type flying experience, because “as PM he had oversight of what was taking place”.

The prevailing weather situation

It was noted that on the morning concerned, “a deep low pressure system […] was centred in the vicinity of Northern Ireland and the Isle of Man”. The forecast chart aviation-relevant weather below 10,000 feet (see below) showed “a cold front approaching the Isle of Man and a slow moving trough following behind (with) the centre of the low pressure system expected to track across Northern Ireland, the Irish Sea and Northern England” during the forecast period. This chart “indicates that widespread moderate turbulence and occasional severe turbulence was forecast to the south of the warm front and therefore in the vicinity of the Isle of Man”.

The Aviation low level Area Forecast Chart valid when investigated flight occurred. [Reproduced from the Official Report

An aftercast from the Met Office stated that SIGMETs warning of severe low level turbulence had been issued for the area in which the aircraft was flown and it was “evident that the crew did not see these SIGMETs or the F215 chart, or other synoptic charts”. The Investigation found that due to the extreme surface winds, no other flights had attempted to land at either BHD or IOM during an extended period around the respective approaches made by OK-LAZ.

The Aircraft and its operation

Based on the Let 410 AFM, the Van Air OM Part ‘B’ (aircraft type specific) was found to state that the maximum demonstrated crosswind component was “20 knots at 90° to the direction of takeoff” and noted that the demonstrations on which this figure was reached “were made with both engines operating and lateral controllability on the ground was close to being limiting”.

The OM did not include any other relevant crosswind limit or guidance and there was no evidence that Van Air crews were trained to handle the aircraft in crosswinds of more than 19.4 knots. The only other wind speed limitation in the OM was for ground operations, which assigned a 45 knot wind speed limit to Captains with more than 300 hours type experience and a 40 knot limit for Captains with less than 300 hours such experience. The actual prevailing wind for the purposes of these limits was to be calculated by “adding half of the gust factor to the stated steady wind speed”.

The OM was found to briefly mention the concept of CRM but made no mention of various components of it “such as the evaluation and management of threats, problem solving and decision making.

It was noted that an approach could be flown with flaps set to 18º as occurred and that according to the AFM, the Vref was always 89 KIAS regardless of aircraft weight and that the maximum approach speed was 135 KIAS, which was the limiting speed with the landing gear selected down or with flaps set to 18º. The OM advised that the Vref should be “increased by not more than 15 knots by adding a value equal to half the headwind component in excess of 10 knots plus the full gust value, to give an ‘adjusted Vref’". The Van Air SOP required approaches to be stabilised by 1,000 feet aal in IMC and by 500 feet aal in VMC. The term “stabilised” was defined as “on the desired flight path in landing configuration with only small changes in heading and pitch required to maintain that path, a maximum sink rate of 1,000 fpm and with airspeed between Vref and Vref + 20KIAS (using the adjusted Vref where applicable)". It was also stated that passing 1,000 feet aal in IMC or 500 feet aal in VMC, the PM should annunciate this and also state ‘not stabilised’ if the stabilised approach criteria are not met at that point, “in which case the PF is to initiate a go-around”. It was additionally stated that “for the aircraft to be considered stabilised when crossing the runway threshold the maximum speed should be the adjusted Vref + 10 knots".

The subject of crosswind limits for takeoff and landing was highly relevant to the circumstances being investigated. It was found that “in the view of the aircraft operator, there was no specific crosswind limit the crew needed to consider when deciding whether to operate”. However, it was noted that the OM Part A referred to a crosswind limit when it stated that “for planning purposes an aerodrome shall be considered below minimum if the steady crosswind exceeds the prescribed limitations” and considered that “other evidence from the AFM and the OM indicates that the maximum demonstrated crosswind component of 19.4 knots was limiting”.

Safety Regulation of a remote non-EU based operation

Whilst Van Air operated under a Czech AOC and the Czech CAA was therefore responsible for oversight of the Operator in accordance with EASA regulations, EU Regulations also require that Member States “cooperate with respect to the safety of operations in the territory of a National Aviation Authority (NAA) which is not the certifying authority”. However, since the Isle of Man is not in the EU, the ruling regulatory requirements are Foreign Carrier Permits (FCPs) for the operation of commercial flights to or from the Island. The UK has to provide a permit for commercial flights between the UK and any non-EU territory and the Isle of Man CAA separately requires such permits if foreign-registered aircraft are used to operate such flights. Both these requirements are “delivered by the UK CAA in co-ordination with the Isle of Man CAA” and VAN Air had been issued with an FCP “for its operation between the Isle of Man and the UK on behalf of the ticket-selling company” (Citywing).

The UK CAA informed the Investigation that “following a number of operational incidents”, the Czech and UK CAAs had been co-operating to oversee this aircraft operator’s remote operations “in a trial sponsored by the EASA” to explore how ‘cooperative oversight’ might work and develop best practices for NAAs involved in the “oversight of organisations / persons certified by another Member State”. This trial was reported to have “identified shortcomings in management structure, operational procedures and in the way the operator’s crew were trained, particularly in threat and error management principles and “although the oversight trial was completed once a programme to address these deficiencies had been agreed, the two NAAs continued to work together to secure further safety and compliance improvements by the operator”. To retain its FCP, Van Air had been required to submit monthly updates and through this process, the UK CAA had concluded that the Company’s newly-appointed Flight Operations Manager lacked the “experience, knowledge and authority” required for the post and noted that his deputy (the First Officer who had acted as PF on the investigated flight) “also had very little operational experience”.

The day before the flight under investigation had occurred, representatives of the UK CAA had met Czech CAA representatives and “requested that inspectors from the two NAAs perform a cooperative audit of the operator at IOM to confirm that safe operations could be guaranteed by the new management structure”. Following the investigated flight, the FCP was suspended and the Operator was directed to suspend UK Commercial Air Transport operations indefinitely. Both NAAs “agreed that a crosswind limit of 19.4 knots should have been applied for takeoff and landing” and the Czech CAA also confirmed that the ground operation limit (which had been introduced by the Operator after a previously investigated Serious Incident at the Isle of Man) was related to aircraft taxiing and was not a takeoff and landing limit. IOM operations by Van Air ceased and were not subsequently resumed.

The Investigation concluded that the Primary Causal Factor was “the decision to land with a maximum crosswind component of 40 knots, which is approximately twice the maximum demonstrated (and limiting) certification value of 19.4 knots”.

Nine Contributory Factors were also identified as follows:

  1. By only studying weather reports for six airfields and without referring to any meteorology charts, the crew had insufficient information to assess the prevailing weather conditions en route and the storm’s path.
  2. The aircraft operator believed that a valid TAF could be disregarded upon the subsequent issue of a METAR that included a TREND forecast.
  3. The aircraft operator did not provide adequate oversight to a flight in airspace affected by this storm. The aircraft commander did not refer to the available weather forecast charts and neither the Operator’s Operations Control Centre (OCC) nor the Flight Operations Manager (FOM) reviewed the situation with him, or suggested he seek guidance from the duty forecaster.
  4. The fuel figures presented on the Operational Flight Plan (OFP) did not account for the correct level of contingency fuel and did not allow for a realistic alternate routing. The aircraft had sufficient fuel for the sector, but the crew did not have as much extra fuel on-board as they believed they had, and the OM offered little guidance on the carriage of extra fuel when there was a possibility of widespread, adverse weather conditions.
  5. The OFP only showed navigational and fuel information for the second of two selected alternates. However, the two Belfast airports are in close proximity so the lack of navigational information for the routing to the first alternate may not have been problematic in this instance.
  6. The CVR evidence, that evolving threats did not precipitate verbal discussion between the pilots, indicates they had not been effectively trained in respect to CRM, and to threat management in particular. The OM appeared to lack guidance concerning the evaluation and management of threats, problem solving and decision making.
  7. The approach became unstable before visual flight conditions were achieved, but the crew did not discuss this, and the required SOPs were not followed.
  8. The limiting airspeed for flight with gear down and for flight with flaps extended was exceeded but no corrective action was taken.
  9. The crew began taxiing the aircraft in a wind which was stronger than the wind which blew (one of the Operator’s other Let 410s) onto its wingtip at IOM in 2007 and which exceeded the ground operation limit introduced after the 2007 accident.

Safety Action advised by the Czech Republic CAA as having been completed was noted as follows:

  1. The aircraft operator has increased the time allocated between crew report and the scheduled departure time to 60 minutes and incorporated this in OM Part A.
  2. The aircraft operator has updated the crosswind limits in OM Part B. No details of the changes have been provided except a statement that the OM now offers guidance for taking off and landing in a crosswind, and that the EASA SIB 2014-20 has been taken into account.
  3. The CAA of the Czech Republic has also stated that recent audits of the aircraft operator have focussed on hazard identification and safety risk management, with particular focus on operations in hazardous weather conditions.

It was considered by the Investigation that although these safety actions addressed “some of the factors identified in this report”, there appeared to be '“a number of issues concerning operational control and supervision which still require attention”. It was noted that whilst the Investigation had “highlighted certain of the operator’s policies and procedures which did not comply with regulatory requirements (it was) possible that there are areas outside the scope of this Investigation that may also require review”.

One Safety Recommendation was therefore made:

  • that the Civil Aviation Authority of the Czech Republic review Van Air’s operational processes, training and operator’s guidance to ensure that they are effectively compliant with the applicable regulations for commercial air transport operations.

The Final Report of the Investigation was published on 8 March 2018.

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