Final Report Issued on 2008 B737 Bird Strike Accident in Rome
Final Report Issued on 2008 B737 Bird Strike Accident in Rome On 10 November 2008 Ryanair Boeing 737-8AS EI-DYG collided with a dense flock of starlings (typical mass 40-1o0 g) on short finals at Rome Ciampino. The Italian safety investigation agency, the ANSV, discuss this accident in a final report issued 20 December 2018. The crew spotted the birds and being aware of the relatively short 2207m runway, initiated a go-around around 100m from the threshold at approximately the same time as impacts occurred. The crew said these sounded like hailstone impacts. However, both engines were unable to deliver sufficient thrust, with N1 (fan speeds) dropping from 62% to 41%. The aircraft, with 172 persons on board, rapidly lost speed and height. The aircraft hit the ground about halfway down the runway, nose high in a near stall condition, on the main landing gear and the lower part of the rear fuselage. The left main landing gear collapsed and the left engine nacelle came into contact with the runway. There were 8 injuries, all minor. Investigators identified 86 bird impacts (on the radome, forward fuselage, wing leading edges, flaps undersides, engine nacelles and landing gear). While this damage would not have affected control of the aircraft, there was extensive bird debris on the stator and rotor blades of the CFM56-7B26/3 engines. Investigators identified 55 impact points on the number 1 engine fan and 30 on the number 2 engine fan. The fan blades themselves showed little damage. The investigators identified that both engines had repeatedly surged after the impacts, which they believed to have considerably exceeded those required for certification. ANSV Conclusions on Cause The accident has been caused by an unexpected loss of both engines thrust as a consequence of a massive bird strike, during the go-around manoeuvre. The loss of thrust has prevented the aircrew from performing a successful go around and has led the aircraft to an unstabilized runway contact. Contributory factors were: The inadequate effectiveness of bird control and dispersal measures put in place by the airport operator at the time of the accident; The captain decision to perform a go around, when the aircraft was at approximately 7 seconds from touchdown. This decision was significantly influenced by: The lack of instructions to flight crew concerning the most suitable procedures to adopt in the case of single or multiple bird strikes in the landing phase; The absence of specific training in the management, by the flight crew, of the “surprise” and “startle” effects in critical phases of the flight. They also explain that the elongated completion of the report was due to retirements and staff shortages. ANSV Safety Recommendations ANSV-12/1525-08/1/A/8 Addressees: EASA and FAA ANSV recommends to provide flight crews with guidelines and/or operational and training procedures, based on a careful assessment of the risks associated with the conduct of the aircraft in approach in case of birds encounter or single/multiple bird strikes. These guidelines should include the following topics: to discuss bird strike risks during take-off and approach briefings when operating at airports with known or expected bird activity; in case of single/multiple bird strikes in the final approach phase, if landing is assured, it is preferable to land maintaining the lowest engine power setting possible rather than carrying out a go-around procedure (in case of birds ingestion, especially a massive one, the engines damages can be greater at...
read moreInadequate Maintenance at a USAF Depot Featured in Fatal USMC KC-130T Accident
Inadequate Propeller Maintenance at a USAF Depot Featured in Fatal USMC KC-130T Yanky 72 Accident Maintenance issues at a US Air Force (USAF) depot featured in the loss of US Marine Corps (USMC) Reserve Lockheed KC-130T Hercules 165000 (callsign Yanky 72) and 16 lives when a propeller blade failed in flight over Itta Bena, Mississippi on 10 July 2017. The USMC Command Investigation determined that the accident was due to: …an inflight departure of the number four blade from the number two propeller. This propeller blade (P2B4) liberated while the aircraft was flying at a cruise altitude of 20,000 feet. This liberation of P2B4 is the first known occurrence of a circumferential fatigue crack initiating from a radial crack which had not grown to pass fully through to the outer diameter blade shank wall of a propeller produced by UTC Aerospace Systems (UTAS). [The liberated blade] sliced through the left (port) side of the fuselage, and impacted the interior of the right (starboard) side… This impact caused the skin of the aircraft to separate along the starboard side. The energy transferred from P2B4’s impact through the structure of the airframe also caused an overload condition of propeller three’s drive shaft. This resulted in its associated reduction gearbox assembly (RGA) failing and the separation of propeller three from the aircraft. Propeller three then momentarily embedded into the upper right section of the fuselage. After which, it continued over the aft starboard section of the fuselage and impacted the starboard horizontal stabilizer separating a significant portion of the stabilizer from the aircraft. As a result, the fuselage “explosively disintegrated into multiple pieces” says the investigation. Post-mishap analysis of P2B4 revealed that a circumferential fatigue crack in the blade caused the fracture and liberation. This fatigue crack propagated from a radial crack which originated from intergranular cracking (IGC) and corrosion pitting. This intergranular radial crack in P2B4 had grown to a total of 2.7 inches in length along the interior taper bore of the blade, extending 1.25 inches beyond the bushing. The radial crack had grown outward through 64 percent of the shank wall section until it was 0.45 inches from the outer diameter at the time P2B4 liberated on 10 July 2017. When the circumferential fatigue crack reached critical length the remainder of the blade shank structure failed in overload… The analysis also revealed the presence of anodize coating within the band of corrosion pitting and intergranular cracking on the blade near the origin of the crack. This finding proves that the band of corrosion pitting and intergranular cracking was present and not removed during the last overhaul of P2B4 at Warner Robins Air Logistics Complex (WR-ALC) in the fall of 2011. The investigation concluded that the failure to remediate the corrosion pitting and intergranular cracking was due to deficiencies in the propeller blade overhaul process at WR-ALC which existed in 2011 and continued up until the shutdown of the WR-ALC propeller blade overhaul process in the fall of 2017. In fact 12 of the 16 propeller blades on the accident aircraft “were determined to have: corrosion that existed at the time of their last overhaul at WR-ALC”. A US Navy (USN) engineering team conducted a ‘process audit’ of the WR-ALC propeller blade repair facility in August 2017. Their report concluded the US Navy requirements for propeller overhaul are different from the USAF requirements. The team...
read moreB777 in Autoland Mode Left Runway When Another Aircraft Interfered With the Localiser Signal
B777 in Autoland Mode Left Runway When Another Aircraft Interfered With the Localiser Signal (9V-SWQ, SIA) Boeing 777-312ER 9V-SWQ of Singapore Airlines was flying from Manchester to Munich on 3 November 2011. Shortly after touch-down in Munich the aircraft veered to the left and went off the runway, before veering right and coming to a stop on the grass to the other side next to the runway. In their safety investigation report, published 85 months after the occurrence, German safety investigation body, the BFU, explain that: …the co-pilot was initially Pilot Flying (PF) during the flight Manchester – Munich. Based on the latest weather information at Munich, visibility 2,000 m, cloud base 300 ft, the Pilot in Command (PIC) decided to assume the role of PF, as the SOPs (FCOM/NORMAL PROCEDURES/OPERATION) of the operator required, and the co-pilot became Pilot Monitoring (PM). The PIC decided to conduct an automatic approach and autoland. A BAE 146-RJ85 taxied along taxiway B4 to runway 08R as the B 777 was about 2.9 NM ahead of the runway threshold 08R and 3.4 NM behind the BAE 146-RJ85 when it received take-off clearance. As the B 777 was about 50 ft above the runway in the flare phase the airplane began to slowly bank left up to 3.5°. As the B 777 flew above the runway threshold 08R, the BAE 146-RJ85 was in front of the localizer antenna and interfered with the localizer signal. The PIC called out: “Okay, flaps twenty.” At approximately 420 m beyond the runway threshold the airplane touched down with the left main landing gear and 132 kt (KIAS). At that time the Auto Flight System (AFS) switched to rollout mode. The autopilot was still engaged as the airplane moved toward the left runway edge and veered off the runway with a speed of 123 kt (KIAS) about 944 m beyond the threshold in the area of taxiway B4. For about 400 m the airplane rolled through the grass north of runway 08R in a slightly curved right hand turn. The largest lateral deviation from the runway was reached at about 1,242 m beyond the threshold; speed was 109 kt KIAS. Because of the system design the autopilot disengaged due to crew inputs via the rudder pedals. The airplane turned right by about 40°, re-entered the runway close to the intersection with taxiway B6, about 1,566 m beyond the threshold. The aircraft crossed the runway with a heading of about 120°. Speed was still 71 kt KIAS. The airplane veered off the runway again, turned left by about 40°, and came to a stop in the grass south of and parallel to runway 08R. There were no injuries or apparent aircraft damage. The crew stated that during the approach and the landing there were no indications as to malfunctions or system failures. The PIC stated he had tried to initiate a goaround procedure by pushing the TO/GA buttons on the thrust levers and thereby triggering the go-around mode once it had been noticed that the airplane banked to the left. But the airplane did not respond. At the same time he retracted the ground spoilers manually which had automatically been deployed at the time of the touchdown. The BFU say: The crew did not inform the approach controller of their intention to conduct an automatic...
read moreSeason’s Greetings from Aerossurance
Aerossurance sends its Season’s Greetings to all its customers, partners, suppliers, colleagues and friends. We also wish you all a safe and prosperous 2019! For aviation advice you can trust, contact Aerossurance at: enquiries@aerossurance.com Follow us on LinkedIn and on Twitter @Aerossurance for our latest...
read moreUSAF Engine Shop in “Disarray” with a “Method of the Madness”: F-16CM Engine Fire
USAF Engine Shop in “Disarray” with a “Method of the Madness”: F-16CM Engine Fire USAF Lockheed Martin F-16CM 92-3883 suffered a General Electric F110-129 engine fire on departure from Misawa Air Base, Japan on 20 February 2018. The resulting USAF Accident Investigation Board (AIB) investigation report describes organisational weaknesses in a USAF engine maintenance facility and the latent defect of an obsolete part incorrectly fitted 6 years earlier. History of the Flight The AIB explain that: The mishap flight (MF) consisted of two F-16CM aircraft. The mishap pilot (MP) departed runway (RWY) 28, fifteen seconds after the mishap lead pilot (MLP). Shortly after the afterburner takeoff, Misawa air traffic controllers informed the MP and the mishap lead pilot (MLP) that the MP had a large flame coming from the aft section of the MP’s aircraft. The MLP also contacted the MP regarding the fire. During the MP’s ascent, he noticed an unexpected decay in his airspeed and climb rate. The MP took a right turn back towards RWY 28, and when unable to maintain airspeed or altitude, the MP jettisoned his stores (external fuel tanks) in accordance with F-16CM critical actions procedures. The two jettisoned fuel tanks landed off-base in Lake Ogawara… The tanks contained approximately 300 gallons each at the time they were jettisoned. The Crash Survivable Flight Data Recorder (CSFDR) indicated the total weight of two tanks with JP-8 was 896 pounds. Following the jettison, the MA regained some airspeed and achieved a better climb rate to get into a position to land. The MP landed on RWY 28, and accomplished the emergency engine shutdown and emergency ground egress critical action procedures. There were no injuries resulting from the mishap. The engine damage and loss of external fuel tanks resulted in a loss (calculated with absurd precision) of $987,545.57. The Investigation The investigation concluded that the cause of the accident was an obsolete turbine frame forward fairing that fractured, causing the engine to ‘overheat’, and resulting in significant damage to parts of the engine. This fairing is made up of three titanium segments that line the forward outer section of the turbine frame. In 2007 an order had been issued that “dictated replacement across the fleet by August 2010 of this susceptible fairing, along with its attaching hardware” after operators “began experiencing excessive wear, cracking and, in a few cases, failure of the turbine frame forward fairing”. This engine had been fitted with the later standard in 2010, however during a subsequent engine shop visit in 2012: …maintenance personnel ordered and installed an obsolete part, a turbine frame forward fairing, years after it was replaced by a forward fairing made of stronger material and design. The logistics system then delivered the obsolete forward fairing. Maintenance personnel installed the obsolete forward fairing on the mishap engine (ME) using the updated version of the bracket hardware. The obsolete forward fairing’s weaker material, along with wear from the mismatched [bracket] hardware, ultimately caused the forward fairing to fracture during takeoff. Once fractured, a piece of the forward fairing lifted and blocked the cooling flow of air around the engine, causing the area near the blockage to overheat and catch fire. Since the obsolete titanium fairings were new at the time of installation, they would have accumulated 760 flying hours on the day of the mishap. The AIB President further found by a preponderance of the evidence that maintenance...
read moreBFU Investigate S-76B Descending to 20ft at 40 kts En Route in Poor Visibility
BFU Investigate S-76B D-HHNH Descending to 20ft at 40 kts En Route in Poor Visibility The German safety investigation body, the BFU, is investigating a serious incident that occurred to Sikorsky S-76B D-HHNH of Heli Service International on 23 October 2017. UPDATED 22 November 2019 after issue of the final report. History of the Flight In an interim report they describe that the flight was on a return to Emden from the DolWin Alpha High Voltade Direct Current (HVDC) platform in the North Sea, which helps transit power from offshore wind farms ashore. At 0842 hrs the helicopter took off now with four persons on board [2 crew. 2 passengers] for the return flight…[and]…climbed to 2,000 ft AMSL which remained the same up until right abeam of Borkum Island. At 0854 hrs the flight crew established radio contact with the Flugleiter at [the uncontrolled] Emden Airfield and requested information regarding the prevailing weather conditions. They were told: “Right now it is raining, cloud base few one thousand, overcast thousand five hundred and wind south-west 10 to 15 gusts 20 kt, QNH 1,010 and visibility here visual reference point 2.5 to 3 km.” At 0857 hrs the crew informed Bremen Radar of passing way-point JUIST. However: Before reaching way-point JUIST the helicopter began to descend. The descent ended in low altitude with reduced speed near the coast line. Then the helicopter climbed again to about 500 ft AMSL and continued the flight to Emden. At 0901 hrs the crew again requested information regarding the prevailing weather at Emden Airfield. They were told: “Right now it has decreased a little bit few seven hundred, broken one thousand, overcast one thousand eight hundred, the rain is gradually slowing down”. The aircraft landed safely at 0911 hrs. The Aircraft Commander (PIC) had a total flying experience of 11,461 hours, of which 3,025 hours were on type. The First Officer (co-pilot) had 910 hours flying experience, of which 359 hours were on type. Investigation (Interim Report) The BFU examined the events leading to the period between 0957 and 0901 when the aircraft lost speed and altitude over the Wadden Sea, the tidal mud flats between the outer island and the mainland. …during the two legs (outbound and return) the co-pilot in the left-hand seat acted as Pilot Flying (PF) and the Pilot in Command (PIC) in the right-hand seat as Pilot Non Flying (PNF). After take-off from the converter station DOLWIN ALPHA the helicopter had been operated using the Flight Director (FD) coupled in the Upper Modes ALT and NAV. Between the way-points UTIRA and HW751 the FD had decoupled without reason. The two autopilots had changed from Attitude Retention (ATT) Mode to Stability Augmentation System (SAS) Mode. This resulted in the PF having to actively control the helicopter manually. Subsequently, the PNF tried to find and eliminate the cause for the FD failure. Both in vain. After they had enquired about the prevailing weather conditions at Emden Airfield they decided to reduce the flight altitude before reaching the coast line. During descent the helicopter had suddenly encountered heavy rain and significantly reduced visibility. At about 500 ft AMSL the co-pilot had handed over controls to the PIC. Notably: He had instructed the co-pilot to extend the landing gear because he wanted to be prepared for a possible off-field landing due to the unexpected bad weather. According to the Cockpit Voice...
read moreCRJ900 Skids Sideways Down Finnish Runway
CRJ900 Skids Sideways Down Finnish Runway On 25 October 2017, Bombardier CRJ900 EI-FPD of Cityjet was operating as Scandinavian Airlines (SAS) flight SK4236 from Stockholm, Sweden, to Turku, Finland, where it landed at 2024 local time. The Landing of Cityjet Bombardier CRJ900 EI-FPD at Turku After touchdown the aircraft did not decelerate as anticipated and entered a skid, drifting towards the right hand edge of the runway but with the nose pointing to the left of track. In their safety investigation report the Finnish Safety Investigation Authority (SIAF or Onnettomuustutkintakeskus) describe how: Approximately 1,200 m from touchdown, the skidding airplane began to veer to the right towards the edge of the paved area. It impacted and broke five runway edge lights. The minimum distance between the right mainwheel tires and the unpaved area was less than 0.5 m. The airplane then started to rotate to the left. When it was at right angles to the runway heading it was moving at 42 kt (78 km/h) groundspeed. It came to a halt next to the runway centerline 2,050 m from the initial touchdown point, having rotated 196° counter-clockwise from the initial direction of travel. The distance from the final position to the runway end was approximately 160 m. Analysis SIAF developed an AcciMap that summarises their analysis: SIAF Conclusions SIAF present 11 conclusions, each paired first with an observation: 1. Aerodrome maintenance decided to clear the runway after an arriving flight had landed and a departing flight had taken off. The decision was not reviewed even though weather was changing rapidly and continuous snowfall increased the thickness of the slush layer on the runway. Conclusion: Long-term runway maintenance planning is not possible under rapidly changing weather conditions. 2. The flight crew did not question the weather and runway condition data on which they based their decisions. The flight crew monitored wind data closely. Conclusion: Some time had passed from the preparation of the previous SNOWTAM. Personnel at the aerodrome knew that snowfall was intensifying. SNOWTAM reliability degrades fast under rapidly changing weather conditions. 3. The airplane was above the maximum performance limited landing weight on landing. Conclusion: The multi-step procedure required to determine the permitted landing weight using the tables provided for the purpose contributed to an error in weight calculations. 4. At Turku, only runway 26 is ILS-equipped. Conclusion: The flight crew elected to conduct a tailwind landing on runway 26 because they considered a runway 08 approach impossible due to the lack of ILS. Finland’s airports, with the exception of Helsinki-Vantaa, have ILS at one end of the runway only. 5. Landing was firm; therefore, weight on the right main landing gear lightened as the oleo leg extended after touchdown, the extension reaching a point where the airplane systems sensed an airborne condition. The thrust reverser system, although armed, was unavailable after touchdown. Conclusion: The flight crew was not familiar with reselecting the thrust reverser system in case of it being inhibited. 6. The airplane entered a hydroplaning condition at the moment of touchdown due to the high groundspeed and a slush deposit on the runway. Conclusion: Anticipating the possibility of hydroplaning enhances situational awareness and prepares for a necessary action if the airplane enters a hydroplaning condition. 7. Hydroplaning prevented the wheels from spinning up to a required speed and therefore the anti-skid system did not activate. The captain’s brake application, which was later augmented by simultaneous brake application by the first officer, resulted in the wheels remaining locked until the airplane came to a halt. Conclusion: The...
read moreHelicopter Tail Rotor Strike from Firefighting Bucket
Helicopter Tail Rotor Strike from Firefighting Bucket On 2 May 2017 Bell 206B3 N911GE, operated by the Marion County Sheriff’s Office as a public-use aircraft, sustained substantial damage during firefighting operations near Orange Springs, Florida. The pilot was seriously injured. The pilot was using an under slung Bambi Bucket and had completed between 25 and 30 drops on the fire. According to the US National Transportation Safety Board (NTSB) safety investigation report: After refueling, he completed three or four additional drops and then filled and pulled the bucket from the water and immediately felt “a severely out of CG [center of gravity] condition to the right.” He assumed that the bucket cables were entangled in the right landing skid, so he released the water from the bucket. The condition persisted, so he rocked the helicopter to attempt to free the cable without success. He then released the cable with the cargo release button and heard the “clunk” sound typically heard when the bucket was released, but then he heard another “clunk.” The helicopter then began to spin violently and after 4-6 rotations crashed into the water. After the aircraft submerged, rolled right and came to rest the pilot “egressed through the left cockpit door and swam to the surface”. On reaching the surface he inflated his life jacket, swam to the water’s edge and used his personal mobile phone to call for help. The NTSB investigation revealed: …6-inch long cable marks on the right rear landing skid tube and a torsional fracture of the tail rotor short shaft. Based on the pilot’s statement, the cable marks likely occurred initially when a cable became entangled on the skid tube… After releasing the bucket the tail rotor shaft fractured when the cable or bucket contacted the tail rotor. Safety Resources Just today, 1 December 2018, a firefighting Kamov Ka-32T crashed in Korea with the loss of one life while uplifting water, though as seen in the library footage below, that was likely by a suction system. Other Ka-32s do use an under-slung bucket: A Flight Safety Foundation (FSF) report ‘External Loads, Powerplant Problems And Obstacles Challenge Pilots During Aerial Fire Fighting Operations’ reviewed US accident reports from 1974 to 1998. UPDATE 28 January 2019: The Bureau d’Enquêtes et d’Analyses (BEA) are investigating an accident in Reunion on 24 January where a Airbus Helicopters AS350B3e/H125 F-OFML appears to have suffered a tail rotor strike on its own under slung firefighting bucket. Also see our articles: Wayward Window: Fatal Loss of a Fire-Fighting Helicopter in NZ Firefighting Helicopter Wire Strike Keep Your Eyes on the Hook! Underslung External Load Safety EC120 Underslung Load Accident 26 September 2013 – Report Unexpected Load: AS350B3 USL / External Cargo Accident in Norway Unexpected Load: B407 USL / External Cargo Accident in PNG Load Lost Due to Misrigged Under Slung Load Control Cable Fatal Wire Strike on Take Off from Communications Site UPDATE 21 October 2018: Fallacy of ‘Training Out’ Error: Japanese AS332L1 Dropped Load UPDATE 20 December 2019: Helicopter External Sling Load Operation Occurrences in New Zealand UPDATE 30 May 2020: Fatal Wisonsin Wire Strike When Robinson R44 Repositions to Refuel UPDATE 28 June 2020: Maintenance Issues in Fire-Fighting S-61A Accident UPDATE 27 December 2020: Fire-Fighting AS350 Hydraulics Accident: Dormant Miswiring UPDATE 9 January 2021: Korean Kamov Ka-32T Fire-Fighting Water Impact and Underwater Egress Fatal Accident UPDATE 21 May 2021: Firefighting AW139 Loss of Control and Tree Impact UPDATE 16 October 2021: South Korean Fire-Fighting Helicopter Tail Rotor...
read moreIced C208 Loses Airspeed During Circling Approach and Strikes Ground
Iced C208 Loses Airspeed During Circling Approach and Strikes Ground On the morning of 30 December 2014, Cessna 208B Grand Caravan N950FE, operated by Baron Aviation Services for Federal Express (FedEx), impacted the ground short of the Roswell International Air Center Airport, New Mexico. Instrument meteorological conditions (IMC) prevailed at the time of the accident and an instrument flight rules (IFR) flight plan had been filed for a Part 135 scheduled cargo flight from Lubbock, Texas. Baron Aviation Services, of Vichy, Missouri, was founded in 1973 and has been a FedEx feeder carrier since 1975. This was originally with DC-3s. The company has grown to a current C208 fleet size of 34 aircraft. N950FE is owned by FedEx. History of the Flight According to the US National Transportation Safety Board (NTSB) safety investigation report (released 3 years and 10 months after the accident in November 2018): The pilot reported that he encountered inflight icing and solid IMC conditions for most of the flight and due to airplane performance was unable to climb above 8,500 feet mean sea level. In the post-accident interview, the pilot thought the altitude limitation was due to ice forming on the unprotected portions of the wings. During the approach the pilot received vectors and altitude changes by the controller; the controller issued a clearance to 4,900 feet; the pilot acknowledged and stated that he didn’t have much elevator control and thought that his controls were “almost frozen”. In the post-accident interview the pilot added that he controlled his descent by adjusting power. He added that based on losing altitude, by using flaps during a climb, he elected not to use flaps on the approach; stating he never went below 100 knots on the approach. About three miles from the runway the controller cleared the pilot down to 4,580 ft, and the pilot acknowledged the transmission. Two miles from the runway the controller reported he was “on course”, and 4,280 ft was the recommended altitude. The pilot was unable to identify the runway until too late for a normal descent to land. Rather than perform the missed approach procedures, he elected to turn left, for a circling [no flpap] approach to runway 35. During the maneuver, an intermittent stall warning horn was heard in the background of radio communications between the controller and the pilot, indicating that the airplane was below the manufacturer’s recommended approach speed. The pilot stated that he “never went below 100 knots” during the approach. On the second landing attempt, before crossing the runway threshold, the airplane suddenly experienced an un-commanded roll to the left and the left wing and left aileron impacted terrain. The pilot was uninjured and the aircraft received substantial to the left wing. Frost and ice was evident on the aircraft. NTSB Analysis …the manufacturer’s minimum recommended no-flaps airspeed in icing conditions is 120 knots. Additionally, the manufacturer recommended using 10° of flap extension for landing when airframe ice was suspected. It is likely that, during the approach for landing, the pilot did not compensate for the airframe icing by increasing the approach airspeed as recommended. The accident is consistent with the pilot not maintaining adequate airspeed during a circling approach to the runway, and the uncommanded roll is consistent with an aerodynamic stall. The situation was likely exacerbated by the presence of ice on the wings and control...
read moreAAIB Highlight Electronic Conspicuity and the Limitations of See and Avoid after Mid Air Collision
AAIB Highlight Electronic Conspicuity and the Limitations of See and Avoid after MAC (Cessna 152 G-WACG and Guimbal Cabri G2 G-JAMM) Cessna 152, G-WACG and Guimbal Cabri G2 helicopter G-JAMM collided in mid-air when both were engaged on training flights near Waddesdon, Buckinghamshire on 17 November 2017. History of the Flight The UK Air Accidents Investigation Branch (AAIB) safety investigation report explains that both aircraft were operating under Visual Flight Rules (VFR) in uncontrolled Class G airspace and neither aircraft was receiving an ATC service. The AAIB comment that: Both aircraft were based at Wycombe Air Park/Booker(WAP). WAP is a busy general aviation airfield with fixed wing, rotary and gliding activity. The weather conditions were clear with good visibility. [However], the opportunity for the occupants of either aircraft to see the other was limited because, although they were in proximity for some time, they were both following a similar track and were not in each other’s field of view. At 1159:10 hrs, G-WACG, with a higher groundspeed, was approximately 0.5 nm behind G-JAMM and 1,950 ft above. A minute later, G-WACG was 750 ft above and approximately 1,000 ft behind. The vertical and horizontal separation progressively reduced to the point of the collision. The damage sustained by G-WACG indicated that the initial contact with G-JAMM was between the right wing of the aircraft and the main rotor blades of the helicopter. The collision occurred in an area called the Brize Norton-Heathrow-Luton Gap, that the Future Airspace Strategy VFR Implementation Group (FASVIG), now Airspace4All, described as an: Intensive private and commercial licence training area for Oxford, Wycombe, White Waltham and other airfields/airstrips in the area, plus helicopter training from RAF Benson.’ Conspicuity and Look-Out Radar data indicated that, when G-WACG was 1,950 ft above G-JAMM, it was only 0.5 nm behind it. A simple assessment indicates that, if G-WACG was straight and level with zero pitch angle at 2,000 ft above G-JAMM, it would have to have been at least 1.9 nm behind for the pilot to have had any opportunity of detecting a possible conflict without additional manoeuvring. In the absence of a turn, the pilot would need to have pitched the aircraft at least 24° nose-down to have had any chance of observing the helicopter. The situation, whereby additional manoeuvring would have been required by G-WACG to bring the helicopter into view, would have persisted up to the point of collision. The cockpit field of view from the Guimbal Cabri G2 is predominantly forwards and sideways. Rearward visibility is severely restricted by the engine and transmission, making rearward searching for an overtaking aircraft impractical. G-JAMM was painted predominantly metallic red with the upper section and tail painted white. The main rotor blades were light grey with yellow tips. The AAIB note that: The European Aviation Safety Agency (EASA) Part-FCL – Subpart C provides a syllabus of flight instruction for a Private Pilot’s Licence (PPL) and includes the note: ‘Each of the exercises involves the need for the applicant to be aware of the needs of good airmanship and look-out, which should be emphasised at all times.’ Specific details concerning the use and interpretation of the syllabus is the responsibility of the National Licensing Authority, in the UK this is the Civil Aviation Authority (CAA). CAA Safety Sense Leaflet 13, ‘Collision Avoidance’ provides comprehensive guidance on the importance of lookout for pilots operating under Visual Flight Rules (VFR)....
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