«SERIOUS INCIDENT Aircraft Type and Registration: Boeing 737-300, VP-CKY No & Type of Engines: 2 CFM56-3B2 turbofan engines Year of Manufacture: 1992 ...»
AAIB Bulletin: 10/2014 VP-CKY EW/C2014/01/01
Aircraft Type and Registration: Boeing 737-300, VP-CKY
No & Type of Engines: 2 CFM56-3B2 turbofan engines
Year of Manufacture: 1992 (Serial no: 26282)
Date & Time (UTC): 15 January 2014 at 2249 hrs (local Grand
Location: Owen Roberts International Airport, Grand Cayman Type of Flight: Commercial Air Transport (Passenger) Persons on Board: Crew - 2 Passengers - 64 Injuries: Crew - None Passengers - None Nature of Damage: None Commander’s Licence: Airline Transport Pilot’s Licence Commander’s Age: 52 years Commander’s Flying Experience: 18,450 hours (of which 13,800 were on type) Last 90 days - 65 hours Last 28 days - 42 hours Information Source: AAIB Field Investigation Synopsis Following an unstable approach to a wet runway, the aircraft was flared for landing but floated along the runway. The commander extended the speed brakes to cause the aircraft to touch down and applied maximum reverse thrust and braking. Reverse thrust was cancelled at a groundspeed of 22 kt with 139 m of runway remaining.
One Safety Recommendation is made relating to the reporting of serious incidents and one relating to the reporting of surface winds at Owen Roberts International Airport.
History of the flight VP-CKY was operating a scheduled passenger flight between Miami, Florida and Grand Cayman, Cayman Islands, with six crew and 64 passengers on board. The commander was the pilot flying (PF) and the co-pilot was the pilot monitoring (PM). The crew recorded the ATIS (valued at 2200 hrs local time)1 for Owen Roberts International Airport at Grand Cayman, which reported a calm surface wind, a visibility of 10 km, few clouds at 1,800 ft and broken cloud at 3,500 ft above the airfield. The temperature was 24°C and the sea level pressure was 1011 hPa. The crew planned to make a visual approach to Runway 08 Footnote Local time in the Cayman Islands is UTC - 5 hours and local time is used throughout this report. The event took place on 15 January 2014 at 2249 hrs local time (16 January 2014 at 0349 UTC).
© Crown copyright 2014 AAIB Bulletin: 10/2014 VP-CKY EW/C2014/01/01 at the airport by routing from the north west of the island towards the Final Approach Fix (FAF) before turning onto the final approach. The approach was to be made using Flap 40 with a VREF of 133 kt and an Autobrake setting of 32. Figure 1 shows the actual track flown by the aircraft.
When the crew of VP-CKY first contacted Cayman Approach control, the Air Traffic Control Officer (ATCO) reported that there were light to moderate rain showers at the airport with a visibility of 2 nm. He also reported that there were rain showers approaching the airport from the east-southeast, moving north-northwest. VP-CKY was cleared to route via ATUVI3 to the FAF and to descend to 1,500 ft amsl. At 2238 hrs, when the crew reported their position at ATUVI descending through Flight Level (FL) 130, the ATCO (who was in the visual control room in the ATC tower at the airport) reported that the visibility on final approach was now less than 0.5 nm. The commander reported to ATC that he could see on the aircraft’s weather radar a “wall of build-up” running “all the way over grand cayman and over the vor”.
The Cayman Islands National Weather Service later provided an image, timed at 2230 hrs, which shows the band of showers to which the commander referred. The colours yellow, amber and red in Figure 2 indicate increasingly heavy precipitation.
Footnote Available Autobrake settings are off, 1, 2, 3 and max.
The commander transmitted that he intended to route to the right (west) of a line towards the VOR and position on base leg for the runway. As a backup plan, the commander said that he would pass over the VOR and position to the east of the airport where the weather looked better on the aircraft’s weather radar.
At approximately 2248 hrs, the crew reported that the aircraft was at an altitude of 1,500 ft and on a 5.5 nm base leg for Runway 08. The ATCO cleared the crew for a visual approach and to report when on final approach. Approximately 30 seconds later, the crew reported that the field was in sight and the controller cleared them to land, adding that the surface wind was from 350° at less than 5 kt. The aircraft touched down at 2249:25 hrs.
At 2250 hrs, the ATCO transmitted “107 tower” and, after the commander replied “go ahead”, he said “just making sure you’re still on [the runway]; backtrack vacate charlie”. The commander asked for the current wind velocity and was told that the anemometer was indicating calm wind while the digital system was indicating wind from 260° at 5 kt gusting to 15 kt4.
Footnote See the section, Information from the Air Traffic Control Officer, for an explanation of the two systems.
Recorded data Flight data recorded on the aircraft’s Quick Access Recorder (QAR) was available from the flight and salient parameters relating to the approach and landing are shown in Figures 3 and 4.
The approach Figure 3 starts with the aircraft at 1,300 ft amsl on the approach to Runway 08. At 1,000 ft amsl (992 ft aal), the landing gear was down, the flap was passing the Flap 15 position in transit to a final flap setting of Flap 30, and the calibrated airspeed (CAS5) was 188 kt. The engines were set at idle thrust during the descent from 1,100 ft to 550 ft amsl, during which the average rate of descent was 1,200 ft/min.
As the aircraft descended through 1,000 ft amsl, the aircraft was in a left turn to intercept the runway centreline, which it briefly flew through at 800 ft amsl. The aircraft was established on the final approach track at approximately 400 ft amsl.
The landing Figure 4 starts with the aircraft at 60 ft agl, a little under 12 seconds before touchdown. At 50 ft agl, the aircraft was flying at 160 kt CAS but had a groundspeed of 175 kt. At about 3 ft agl, approximately six seconds after the thrust levers were set to the idle position, the speed brakes were deployed and the aircraft touched down approximately one second later at 157 kt CAS (166 kt groundspeed). Maximum braking was then applied, followed four seconds later by the selection of reverse thrust, both of which were maintained until the aircraft slowed to approximately 22 kt groundspeed, by which time the aircraft was being positioned to the left side of the runway. The distance from touchdown to the point that reverse thrust was cancelled was 1,027 m (derived from recorded groundspeed).
Figure 5 shows information on the landing derived from recorded flight data and depicted on a plan of the airport (all distances are approximate). The aircraft touched down 634 m beyond the touchdown zone markers. When reverse thrust was cancelled at 22 kt, there was 139 m remaining of the landing distance available (LDA). The aircraft began to turn around when the groundspeed was 6 kt, 95 m from the end of the LDA.
Calculation of ground stopping distance
The recorded flight data was used to calculate a ground distance from touchdown to the point on the runway where the aircraft was at 22 kt, the groundspeed at which the maximum braking action ceased. This gave a distance of 1,027 metres. This was compared with calculations based on the tabulated information in the Boeing 737-300 Quick Reference
Handbook (QRH) for two cases:
1) a ‘Dry’ runway
2) a ‘Wet’ runway with ‘good’ braking action.
The conditions used in each case were a landing weight of 113,300 lb, an airspeed of VREF+25 kt, a tailwind of 10 kt and maximum manual braking. Allowing an ‘air distance’ of 305 metres in each case, the calculated ground distances (to a standstill) were 785 metres for the Dry runway, 1,205 metres for the Wet runway.
Engineering action Following evaluation of the recorded data from the incident, and the identification of a significant peak value (2.249g) of vertical acceleration at touchdown, a Hard Landing inspection was ordered on VP-CKY. This inspection was in accordance with the aircraft manufacturer’s Aircraft Maintenance Manual (AMM), which details two Phases. The Phase 1 inspection, conducted on 5 February 2014, did not show any damage so, in accordance with the AMM, the further Phase 2 inspection was not performed.
Information from the commander
The commander reported that, as the aircraft passed the north-western tip of the island, he could see the whole of the west coast of the island, including the airport and runway, beneath the cloud. The cloud had a “flat ceiling” at what he estimated to be 1,200 ft to 1,400 ft amsl.
The aircraft joined the base leg approximately 5 nm west of the runway at 1,500 ft amsl and 220 kt. The commander reported that it was raining at the FAF (Figure 1) and so he turned left, inside the FAF, to avoid the weather and intercept the final approach at approximately 4 nm.
He also briefed the co-pilot that the landing would be made using Flap 30 instead of Flap 40.
As the aircraft flew along the final approach path, the crew could see the runway through light rain. However, the commander reported that, just after the aircraft descended through 50 ft radio altitude and he began to flare, “a wall of heavy rain hit the windscreen”. He considered that the situation was “too critical to go around”, so he maintained runway alignment using the runway edge lights as his reference and deployed the speed brakes at what he estimated to be 6 ft radio altitude. After touchdown, the commander selected maximum reverse thrust and maximum manual braking and brought the aircraft to a halt just before the turnaround bay at the end of the runway. He commented that he had difficulty selecting reverse thrust, such that it seemed to take longer than normal to engage, and that the brakes felt ineffective.
The commander stated that, although he had been aware that the aircraft was faster than normal on the approach, the speed had been fluctuating in the gusty conditions and he had expected it to decrease when the aircraft was below 200 ft aal.
Information from the Air Traffic Control Officer The ATCO was in the visual control room in the ATC tower and he based his report of visibility upon knowledge of the distance from the tower of lights in the local area.
The ATCO saw the lights of the aircraft while it was on base leg and commented that it appeared closer than would normally be expected. During the landing, he noticed that the aircraft floated before touching down just before Taxiway C. He had expected the aircraft to go around, basing his judgment on the distance it floated along the runway and the fact that the runway was wet. He lost sight of the aircraft after it touched down because of the intensity of the rain and the spray from the thrust reversers. He could see the red centreline lights at the end of the runway6 and he saw them disappear as they were occluded by the passing aircraft. This prompted him to ask the commander whether the aircraft was still on the runway.
Footnote The runway centreline lights are red along the final 300 m of runway.
The ATCO explained that the primary system for reporting wind velocity is the digital Automated Weather Observing System (AWOS) which uses equipment located on the south side of the airfield. However, during inclement weather, there is doubt about the accuracy of the information this equipment provides because the wind can be disrupted by local obstacles. An alternative display of wind velocity is available in the ATC tower which takes its information from an anemometer on the north side of the airfield. During inclement weather, the controller considered this equipment to be more accurate.
Reporting of the event
The commander considered that the event did not lead to an accident or an incident that would be classified as reportable. Nevertheless, after discussion with managers at the airline, he submitted an Air Hazard Report Form as part of the operator’s Safety Management System (SMS). Approximately two weeks later, the operator instigated an investigation after receiving further information about the event. Subsequently, the Civil Aviation Authority of the Cayman Islands (CAACI) asked the operator to produce a report on the event which the operator submitted through the CAACI’s Mandatory Occurrence Reporting (MOR) scheme.
The ATCO did not feel that guidance on reporting within the Manual of Air Traffic Services (MATS) was clear in respect of this type of incident. He did not consider the incident to be reportable because the aircraft had remained on the runway.
Stabilised approach criteria The landing mass recorded on the landing data card was 113,300 lb, at which mass VREF would have been 133 kt for a Flap 40 landing and 136 kt using Flap 30.
At the time of the event, the operator required all approaches to be stabilised by 1,000 ft aal.
The operator’s stabilised approach criteria included:
1. Aircraft on the correct flight path.
2. Speed not more than VREF + 20 kt and not less than VREF with a thrust setting appropriate for the airplane configuration (‘engines spooled to the required engine thrust setting for the approach’).
3. Aircraft in the correct landing configuration (‘gear down and landing flaps’).
4. Sink rate no more than 1,000 ft/min.
5. All briefings and checklists completed.
Boeing 737 Flight Crew Training Manual (FCTM) The Boeing 737 FCTM states that, if a go-around is initiated before touchdown but touchdown occurs, the crew can continue with the go-around. A go-around can be initiated after touchdown until the point at which reverse thrust is selected.
The FCTM states that, after touchdown and with the thrust levers at idle, the reverse thrust levers should be raised rapidly aft to the interlock position and then to the reverse idle detent.