Glider Type and Registration (Tail No): BGA No: Discus CS Lak 17 G-IDER (W4) G-CKOI (170) Engine: Year of Manufacture: Time (local) and Date: Location: Type of flight (actual/intended): Type of launch: Persons on Board: Nature of Damage: Injuries: P1’s Qualifications: P2’s Qualifications: Commander’s Age: Commanders’ Flying Experience : Total all types: Total on Type: Last 6 months: Information Source(s): None 1 (turbo) 1992 2006 16:02 hrs on 26 July 2014 Lt. Paxton, Nr. St. Neots, Cambs. Competition task (both gliders) Aerotow Aerotow 11 Glider destroyed Serious Minor Minor Silver C N/A 70 years 3 diamonds N/A 60 years 800 hrs 200 hrs 15 hrs 5000 hrs 1000 hrs 100 hrs BGA Accident Report Forms, Club Investigation, witness statements and follow-up enquiries Synopsis On 26th July 2014, gliders W4 (Discus CS) head. He landed safely in a crop field but had and 170 (Lak 17) were both taking part in a to move away from an approaching combinecompetition organised by The Gliding Centre harvester. He was taken by ambulance to at Husbands Bosworth. At 16:02 hrs, whilst Addenbrooke’s Hospital, Cambridge, and over fields adjacent to the A1 trunk road near given an extensive examination but was found Little Paxton, Cambs, the two gliders collided not to have sustained any serious injuries. at a height of around 4000 ft. The collision Glider 170 was capable of flying after the resulted in the outer portion of the left wing collision. The pilot initially intended to bail becoming detached from W4, which out, but decided to remain with his glider after precipated a structural failure of the same assuring himself as best he could that wing at its attachment at the fuselage. The structural damage was limited to the cockpit pilot was left with no option but to bail out and outer right wing. He landed without and, although the parachute deployed further incident at Bedford (disused) airfield. successfully, the breast strap rose up over his History of the flight Both gliders were flying from the gliding site at Husbands Bosworth were taking part in the HB Challenge Cup (Regional) Competition. The Distance Handicap task set was 178 km with turning points at NPT and OAK. The start line had opened at 15:00 hrs BST, with 170 starting the task at 15:09 hrs, W4 at 15:02 hrs. The following is taken from reports made by each pilot after the accident. Discus CS (W4) The pilot had seen another glider flying in the same area as his on several occasions while on (b) the competition task. He thought he saw a He pulled the parachute ‘rip-cord’ and, as the glider prior to the accident circling in what canopy deployed with a sharp tug, it pulled the seemed to be a poor thermal about half a mile breast strap over his head, photo (c). He was away. He didn’t recollect seeing any more of then surprised that he still held the unattached this glider until immediately before the parachute release handle in his right hand so impact, when it appeared from his left side and dropped it to pull the breast strap back across above, impacting with W4’s raised left wing. his chest. He then took hold of the parachute As it did so, there was a very loud noise and cords and attempted to manoeuvre the the glider went into a tumbling spin, photo (a). parachute, as there were power lines, a river The pilot realised that he had no option but to and trees below him. However, the parachute get out, so operated the normal canopy- didn’t respond and he landed heavily into opening knob and thought that the canopy standing crop in a field that was being flew off1. He then pulled the seat harness harvested. He saw a combine harvester release lever and with no effort he fell from bearing down upon him and so crawled out of the glider into a tumbling free fall, photo (b) the uncut crop into a cut area, pulling the parachute after him. A farm worker came to his aid at that point. (a) (c) The pilot was taken by ambulance to Addenbrooke’s Hospital, Cambridge, for an extensive examination. He was kept there 1 Photo (b) shows that the glider canopy had opened, but that complete transparency can be seen to the left of the glider’s the frame remained attached to the glider. The apparently tail. overnight for observation and discharged the to the right outer leading edge of 170’s wing following morning. He experienced some and the root section of W4’s left tailplane, trauma and was advised he had suffered only probably from impacts with debris from W4’s minor cuts and grazes.2 broken wing. This led to a structural failure of the tailplane but this remained loosely Lak 17 (170) attached until the glider struck the ground. The pilot stated that his recollection of what happened before the collision is unreliable. He recalled being in a thermal and circling to the left for a while, and that there were 2 gliders close by, one approximately 1000ft above him and one 2-300ft below, some 500m to the North-East. His rate of climb was tailing off and he was thinking of leaving or trying to find another core. He did not recall whether or not he left the thermaI, but did recall seeing the other glider only a second or so before the impact as it came out of the sun from above. The pilot pushed the stick fully forward and instinctively ‘ducked’ as part of (d) Failure region of W4’s outer left wing the other glider went close by his head. He initially decided to bail out, released his harness and stood up. However, the glider remained controllable and the broken canopy allowed the pilot to quickly inspect the glider’s tail, which appeared to be undamaged, so he made the decision to strap himself back in. He flew the glider 10-15km from the point of impact to Bedford disused airfield and landed without further incident. Neither pilot recollected seeing the other glider until a second or two before the collision. Meterological conditions At the time of the accident the wind was quoted at 5-10 kt/340 deg, visibility 30 km, and 3/8 cloud with a base of 5,500 ft. Wreckage assessment A hard impact had occurred between W4’s left outer wing (d) and 170’s cockpit (e). This removed the outermost part of the wing, and (e) Damage to 170’s right cockpit edge precipitated a structural failure at its inboard and instrument binnacle end, and forced the instrument binnacle downwards causing structural damage to the The relative attitudes of the gliders at the time cockpit section. Secondary damage resulted support the statement by the pilot of 170 that 2 The following day the same hospital contacted him to but that this did not require treatment, only a check again at advise him that he had a stable fracture of his L1 vertebrae, the hospital in several weeks time. his glider had been put into a steep dive, in his attempt to avoid the collision. All damage seen was judged as a result of the collision and, in W4’s case, impact with the ground. Neither pilot reported any problems with their flying controls prior to the collision, and this is supported by examination of the wreckages by various parties during recovery/repair. Both gliders possessed an EASA Certificate of Airworthiness and had current (h) Airworthiness Review Certificates, and both pilots were flying within their glider’s weight and balance limits. The collision Each glider was equipped with a data logger, which provided good evidence of their flights. Figures (g) and (h) show screen shots from SeeYou of the flight paths of the gliders (W4 red, 170 blue) shortly before the collision, and figure (i) a plan view of their estimated relative positions for the 12 seconds before the (i) collision. As may be seen, the gliders were circling in the same direction (to the right) but initially not about the same vertical axis. As glider 170 approached the same level as W4, it moved closer to W4’s orbit. At 6 seconds before the collision, the gliders were about Based upon the above, an assessment of the relative visibility of each glider from the opposite cockpit available to the pilots, and their estimate distance apart, is shown in the following table: 480ft apart. Glider 170 was moving from right to left in the field of view of W4 so that at 4 seconds it was 20° to the left and at 2 seconds 50° left. At 2 seconds the gliders were approximately 250ft apart. The position of W4 relative to 170 hardly changed between 12 seconds and 6 seconds. At 4 seconds W4 would have been just behind the right wing tip of 170. At 2 seconds W4 was 70° R viewed from the cockpit of 170. At 4 seconds from impact both pilots may have tightened their turns slightly (i), possibly in response to the same surge of lift. (g) (i) naturally makes a series of jumps, or saccades, Lookout issues with intervening rests. The scene is only The prime means of avoiding mid-air interrogated by the brain during the rest collisions in open airspace in VMC is lookout, periods. A very small object may therefore be ie, the see-and-be-seen method, but this ‘jumped over’ or fall on an area away from the cannot be considered a perfect method. When fovea – in either case it will not be detected. thermalling, situational awareness in addition Each saccade-rest cycle takes a finite time and to a good lookout is vital and, if sight is lost of a full scan of an area of sky will take several a glider in close proximity, then serious seconds. An object missed early in the scan consideration should be given to leaving the may approach hazardously close or even thermal in an appropriate manner. (See the collide before that area is scanned again by the Soaring Protocol below.) pilot. The effectiveness of visual air-to-air There are limitations in the human visual acquisition also depends on the contrast of an system that serve to make collision avoidance aircraft with its background. Increased difficult by visual means alone. The capacity contrast improves visual acquisition but of the human eye to resolve detail is not contrast degrades exponentially with visual distributed evenly across the retina. The most range. If contrast reduces to approximately central part of the retina is termed the fovea, 5% the target disappears. and is composed only of cones - the light Another of the characteristics of the human sensitive cells used for day vision. Cones eye is potentially more relevant here. The provide high visual acuity, colour vision and human visual system is particularly attuned to contrast discrimination. Although there is detecting movement, this being accomplished good resolving power at the fovea, this ability largely using peripheral vision, but is less drops rapidly outside the fovea. Normal visual effective at detecting objects that appear reflexes adjust the direction of gaze to ensure stationary. The outer boundaries of peripheral that the image of an observed object falls on vision correspond to the boundaries of the the fovea for optimum resolution. Such vision, visual field as a whole. For a single eye, the sometimes termed ‘focal’ vision, requires a extent of the visual field can be defined in stable image and the viewer’s attention. Away terms of four angles, each measured from the from the fovea, the density of cones reduces, fixation point, i.e., the point at which one's and the density of rod cells increases. Rods are gaze is directed. These angles, representing more sensitive to light than cones, and are four cardinal directions, are around 60° used for day, night and low intensity vision. superior (up), 60° nasal (towards the nose), Rod vision is monochromatic and of low 70-75° inferior (down), and 100-110° acuity, giving only outlines or shapes. It is, temporal (away from the nose and towards the however, responsive to movement. It does not temple), ie, 130/135° in the vertical sense, and require the same degree of attention as focal 160/170° in the lateral sense. vision, and is important for spatial orientation However, this field of vision begins to and ‘flow vision’, which gives a sense of contract after about the age of 35 years. In speed. Rod vision is sometimes referred to as males, this reduction accelerates markedly ‘peripheral’ vision. A distant aircraft will be after 55 years of age and for males aged 70 perceptible to a pilot if it is acquired at or near years is likely to be less than 130° for a single the fovea, a near one by peripheral vision, eye in the lateral sense. especially if there is good relative motion. As When flying, the eyes and head are very rarely an area of sky is scanned by the pilot, the eye still for very long except, critically perhaps, when looking at the instrument panel. that none of the pilots were incapacitated or Although head/eye movement will killed in the collision itself. The pilot of 170 compensate to an extent, in a given situation a was, literally, within inches of being hit in the reduction in the time for an older pilot to chest/head by W4’s wing. become aware of the presence of another On 14 May, one of these collisions occurred aircraft using peripheral vision will be between an Arcus and a Discus B close to the present, particularly so if there is little or no gliding site at Gransden Lodge airfield. Both apparent relative motion. gliders had launched from this site with the An additional factor which could influence the intention of carrying out recreational flights in time taken to recognise a collision threat is the the local area. The report relating to this time taken for the eye to ‘accommodate’. accident identified the following: Accommodation is the process of focussing on an object. Whereas a camera is focussed The gliders sharing the thermal were clearly by moving the lens, the eye is brought into operating in accordance with published focus by muscle movements which change the guidelines in that they maintained safe shape of the lens. A young person will relatively static positions relative to each (typically) require about one second to other. The Flarm units on both aircraft gave accommodate to a stimulus, however, the frequent audio warnings throughout the 5 speed and degree of accommodation minutes before impact. However, during the decreases with age. The average pilot final minute before impact, the warnings probably takes several seconds to ceased (for unknown reasons) and this may accommodate to a distant object. Shifting the have led to an assumption that one of the focus of the eyes, like all muscular processes, gliders had departed the thermal. is also affected by fatigue. Obscuration of the Flarm signal by the airframe did not appear to be a factor but Flarm could not be totally discounted. Flarm is a useful aid to lookout, when used appropriately, and one of its features is to alert This report made the following Safety the pilot to potential collisions, but only if Recommendation both gliders in a potential conflict situation are equipped with serviceable systems. Glider 170 was so equipped, W4 was not. Therefore, there was no possibility of either pilot SAFETY RECOMMENDATION BGA 2014/XX detecting the close proximity of the other glider by electronic means. This raises the possibility that where only a proportion of gliders in relative close proximity are equipped, the attention of the pilot of a Flarm That the BGA examine a mechanism for a check of understanding of soaring procedures during biannual pilot competency checks. equipped glider may be divided between Discussion observing the Flarm output following an audio Effective lookout and awareness of any other warning and subsequently searching for the glider(s) in close proximity is paramount. identified target, and general visual lookout. Although this may be supported by the Therefore it is particularly important when in appropriate use of electronic means, such as proximity to other gliders that the best possible lookout is maintained, with ‘head down’ time reduced to an absolute minimum. Flarm, their non-universal use (and possibly their reliability) means that it is unwise to use them as a prime means of collision avoidance Previous mid-air collision over good visual lookout. However, in the In 2014, four glider-on-glider mid-air collision scenario between 170/W4, had both collisions occurred. All the pilots involved gliders had Flarm installed, then an survived by either parachuting or landing the appropriate warning could have alerted the damaged gliders. However, there was a high pilots to each other’s close proximity, degree of luck associated in these events in possibly in time to avoid the collision. lift. After a fatal mid-air collision in the early It is generally accepted that however good a 1990s all of the interested parties governing pilot’s lookout may be, with or without the gliding in the United Kingdom met to support of electronic means, it cannot be formulate a protocol for safe flying in considered to be 100% effective in removing thermals to improve understanding and the risk of a mid-air collision. Limitations of minimise risk in this facet of the sport. This the human visual system and when looking Soaring Protocol (below) generated by the towards the sun are two of various factors meeting has survived un-amended since its which can degrade optimal lookout. inception: The wearing by of parachutes by glider pilots BGA THERMAL SOARING PROTOCOL is an acknowledgement of these factors and Joining a thermal that a risk of collision exists, particularly  Gliders established in a thermal have when thermal soaring, and they are worn largely to mitigate this risk. As demonstrated by this and other recent mid-air collisions, their successful deployment has saved several lives in 2014 alone. Being aware of how to best exit a damaged glider before such an event, and regular servicing of parachutes, must be considered prudent. right of way  All pilots shall circle in the same direction as any gliders already  If there are gliders thermalling in opposite directions, the joining glider shall turn in the same direction as the nearest glider (least vertical separation) Following a collision where the glider  The entry to the turn should be apparently remains controllable, a difficult planned so as to keep continual visual decision has to be made by the pilot of whether to remain or to leave the glider, assuming the collision occurs at a height to give sufficient time to bale out and for the parachute to deploy. Remaining with an apparently controllable, but damaged, glider brings its own risks, as it is almost impossible to fully assess its airworthiness following a contact with all other aircraft at or near the planned entry height  The entry should be flown at a tangent to the circle so that no aircraft already turning will be required to manoeuvre in order to avoid the joining aircraft serious collision, even if a handling check is Sharing a thermal carried out. At least one previous collision  Pilots should adhere to the principle resulted in a fatality where the pilot elected to land the glider, but where structural integrity was lost at a height too low to use the of see and be seen  When at a similar level, never turn parachute. A damaged glider structure may inside, point at, or ahead of another deteriorate before landing under normal aircraft unless you intend to overtake aerodynamic loading from, for example, and can guarantee safe separation gusts/turbulence, use of the flight controls,  Leave the thermal if, in your deployment of flaps, landing gear and judgement, you cannot guarantee airbrakes. adequate separation  Look out for other aircraft joining or BGA advice on thermalling converging in height Uniquely in aviation, glider pilots fly in close Leaving a thermal proximity to other gliders without the benefit of a pre-flight briefing. The nature of the sport dictates that gliders congregate in areas of rising air enabling them to climb and then use the height gained to proceed to other areas of  Look outside the turn and behind before straightening  Do not manoeuvre sharply unless clear of all other aircraft A poster (j) reflecting this was developed and In consideration of the Safety issued some years ago to clubs, but like most Recommendation made in the report on the ‘safety’ related material, maintenance of its Gransden collision on 14 May 2014, and the effectiveness requires that such material is fact that the BGA is currently reviewing the ‘refreshed’ on a regular basis. content and presentation of the Thermal Soaring Protocol, no further recommendations are made here concerning the protocol. In consideration of the initial difficulty that the pilot of W4 had with his parachute, the following Safety Recommendation is made to the BGA: Safety Recommendation 2015-xx It is recommended that the BGA should remind all glider pilots of the high importance of properly adjusting their parachute harness to ensure as far a possible that it will deploy correctly and avoid the possibility of the breast strap ‘riding up’ upon deployment. Conclusion The collision occurred close to the village of Little Paxton, near St Neots, Cambs, at around Safety Action The following text is a recently agreed statement by the BGA Executive Committee on the use of traffic and collision warning systems a height of 4000 ft. Only one of the two gliders was equipped with Flarm so collision avoidance relied upon good visual lookout and situational awareness. However, neither of the pilots involved saw the other glider in sufficient time to avoid the The BGA encourages the widespread use of collision. traffic and collision-warning systems in gliders and tugs. FLARM is an increasingly popular system. Pilots should make their own decision on equipage based on compatibility with other systems and as to whether such a system is appropriate for their particular operation. Pilots are reminded that whilst electronic collision warning equipment can enhance pilots' awareness by providing most useful warnings, such equipment cannot and must not replace a good systematic visual lookout scan, and that it is necessary to avoid any in- cockpit equipment from distracting from the visual lookout scan.