SAFE WINGS. This issue THE GO AROUND DECISION ILLUSIONS THAT CAUSE ACCIDENTS AND INCIDENTS AT NIGHT. * For Internal Circulation Only

Transcription

1 * For Internal Circulation Only SAFE WINGS Flight Safety Magazine of Air India, Air India Express and Alliance Air Issue 66, November 2017 This issue THE GO AROUND DECISION ILLUSIONS THAT CAUSE ACCIDENTS AND INCIDENTS AT NIGHT

2 SAFE WINGS November Edition 66 EDITORIAL Failure to go-around and continuing with a landing inspite of deteriorating weather or unstable approach is the main cause of approach and landing accidents. Collisions and incidents caused due to optical illusions are many fold greater at night. In this issue we have covered these two topics. ACKNOWLEDGEMENTS The posting of stories, reports and documents in this magazine does not in any way, imply or necessarily express or suggest that all the information is correct. It is based on details gathered from various sources and is for information purpose only. The Flight Safety Department is making this material available in its efforts to advance the understanding of safety. It is in no way responsible for any errors, omissions or deletions in the reports. 1 P a g e

3 November Edition 66 SAFE WINGS THE GO AROUND DECISION In spite of SOPs making it mandatory to Go-Around in instances of unstabilised approach, it is estimated that worldwide about 95 % of unstabilised approaches continue to a landing. The causes could be: i. Accident/ Serious incidents rates are very low at almost 1 in a million un-stabilised approaches. Pilots due to their own, experience feel confident that they can land from an unstabilized approach without incident. ii. During simulator trainings and checks, pilots often conduct approach during non-normal situations where they are under pressure to land due to a fire, etc. Due to a hurried approach, marginal weather situations induced in the Simulator session, the Approach becomes unstabilised and the pilots continue and manage to land. The simulator instructor, due to time constraints of having to complete the requisite exercises in the limited time available, at times, permits the crew to continue a somewhat unstabilized approach and land. Every such successful landing whether in simulator or actual flight increases the confidence of the crew and would tempt that crew to attempt landing off an unstabilised approach or land in poor/marginal weather conditions confident that since they have done it so many times they could do it again. It may be that only one approach in a million unstabilised approaches results in an accident. But that one in a million could be the one you are flying. You just cannot afford to be that one out of a million. 2 P a g e

4 SAFE WINGS November Edition 66 Statistics show that over 95 % of all unstabilised approaches continue to a landing. In spite of each individual airline as well as the industry documenting that pilots should not continue an unstabilised approach, yet why is it that repeatedly pilots routinely ignore this SOP. Every time a pilot continues and recovers from what is defined as an unstabilised approach, where a normal landing was made, it would probably reinforce the view that stabilized approach procedures are too restricted and could be bent somewhat and that these procedures should be more flexible. This attitude will then permeate to other portions of the SOP and then the whole purpose of having an SOP gets diluted. SOPs are made after thorough research and after experienced Training Captains and Management Pilots have studied, discussed and come to the conclusion that certain procedures, restrictions and a disciplined method of operations is necessary for that airline. Whilst making SOPs consideration is given to the crew experience level, cultural back ground, geographical location, weather conditions and even airports where the airline operates. These SOPs then need to be sacrosanct and meticulously followed. Stabilised approach criteria have been standardized, developed and adopted worldwide. What is mentioned in the SOPs are a gold standard. If it is required to deviate from this a special briefing is required stating why. For e.g. If the aircraft has to land with reduced flap setting ( e.g. Flap 15) at high landing weight the approach speed would be high and consequently the ROD on finals would be high too. For a 3 glide slope with an approach speed of 175 kts the ROD itself will be 950 ft/min and momentarily could exceed the stabilized approach definition of 1000 ft/min. At runways with a glide slope angle of 3.2 the ROD in this case would be slightly above 1000 ft/min. Therefore this would require the PF to cover this in the approach briefing so that both pilots are aware of it. In such a case a ROD of 1050 FPM would not be considered unstabilised. An unstabilised approach is an obvious deviation from the expected approach criteria. Such an approach must require a Go-Around each and every time. This can only happen if Simulator Instructors and Training Captains adopt a Zero tolerance policy for continuing with unstabilised Approach, no matter what the situation is. 3 P a g e

5 November Edition 66 SAFE WINGS Other threats to continuing an Approach which would otherwise require a Go-Around are:- 1. I will decide later: hoping you will be able to stabilise later. Leaving it for later may cause a fixation till it is too late. 2. I am visual and can see the runway: Being visual is a strong motivator to continue an unstabilised approach. More unstabilised approaches and ALAs happen during VMC than in IMC. 3. Get Home Itis:- It is our job to get the passengers to their destination. If I divert I will upset them, and also my duty time may exceed and cause further delay, 4. Lack of preparation:- rushed approach without sufficient briefing. 5. Late runway change or approach change requiring FMC reprogramming 6. Changing wind conditions 7. Inadequate traffic spacing by ATC 8. Fatigue 9. Commercial or personal pressure (stress) Suggestions: 1. First officers must be encouraged by the Airline and empowered to call for a Go-Around any time when stabilized criteria are not met or if weather conditions preclude a safe landing even if the PIC appears very confident 2. It shall be mandatory for the PF to Go-around if the PM/PNF calls Go Around and if s/he does not carry out an immediate Go around the PM/PNF/ first Officer must take over controls and Go Around. This must be reiterated in every Simulator training and check. Most simulator go-arounds are done at heavy weight and one engine inoperative. Go-around must be practiced in all situations including with all engines operating and lower aircraft weights as that is a more realistic situation. By Capt Vivek Kulkarni Air India Express 4 P a g e

6 SAFE WINGS November Edition 66 ILLUSIONS THAT CAUSE ACCIDENTS AND INCIDENTS AT NIGHT. :-By Capt Vivek Kulkarni The number of landing accidents and ground incidents/accidents at night are nearly 3 times of those that occur during the day. Visual perception is considerably lowered during night and a brief description of the eye and some common illusions which cause accidents are given below. The Eye Vision is primarily the result of light striking a photosensitive layer, called the retina, at the back of the eye. The retina is composed of light-sensitive OPTICAL ILLUSION cones and rods. The cones in the eye best perceive an image when the light is bright, while the rods work best in low light. Cones are concentrated around the center of the retina. Cones allow colour perception by sensing red, blue, and green light. The best vision in daylight is obtained by looking directly at the object. This focuses the image on the fovea which is directly behind the pupil, where the cones are concentrated, and details are seen clearly. The cones, however, do not function well in darkness, which explains why colour is not seen as vividly at night as it is during the day. Rods are receptors for dim light and are concentrated outside the fovea area. The number of rods increases as the distance from the central area increases. Rods sense images only in black and white. Because the rods are not located directly behind the pupil, they are responsible for most peripheral vision. Images that move are perceived more easily by the rod areas than by the cones in the fovea. In low light, the cones lose much of their function, while rods 5 P a g e

7 November Edition 66 SAFE WINGS become more receptive. The ability to see an object directly in front of you is reduced, and much depth perception is lost, as well as judgment of size. Due to the concentration of cones in the center, there is a night blind-spot at the center of vision. How well a person sees at night is determined by the rods in the eyes, as well as the amount of light allowed into the eyes. The wider the pupil is open at night, the better night vision becomes. Vitamin deficiencies and other factors, such as smoking, alcohol, and certain drugs can greatly decrease night vision. Night Illusions. Blue Light Phenomena: At night, blue wavelengths of light prevail in the visible portion of the spectrum. Even pilots with perfect vision find that image sharpness decreases as pupil diameter increases. For individuals with mild refractive errors, these factors combine to make vision unacceptably blurred especially if they are not wearing their prescribed corrective glasses. The blue light phenomena can become even more accentuated when there are a number of closely spaced parallel taxiways exiting from a long parallel taxiway perpendicular to these, where the area between 6 P a g e

8 SAFE WINGS November Edition 66 two parallel taxiway exits could also appear as a taxiway. To cope up with the increase in air traffic, the airport authorities have increased the size of aprons and the number of taxiways to facilitate flow of aircraft. Therefore hazards such as closely spaced taxiways are increasing at all airports where chances of error is omnipresent.. Certain large cash rich airports such as Dubai have mitigated these hazards partially by installing taxiway centerline lights and progressive taxi lights. Yet new hazards are frequently appearing even at such cash rich airports, due to the increase in construction activity. Dark Focus: Another factor to consider is dark focus. When light levels decrease, the focusing mechanism of the eye may move toward a resting position and make the eye more myopic. Practicing good light discipline is very important and helps pilots to retain their night adaptation. Keeping the cockpit lighting on dim allows the pilot to better identify outside details. Hence it is a good practice to turn off the dome lights and dim the cockpit lights before top of descent as it takes the eyes about 15 mins for complete dark adaptation. Black-Hole Approach: Another Illusion which occurs at night is the Black Hole Approach. In the absence of lighted terrain between the aircraft and runway, pilots attempt to maintain a constant visual angle between the runway threshold and runway end lights (or the ground lights beyond). Contrary to what you might think, a constant visual angle does not equal a constant approach angle. In fact, a constant approach angle results in an ever-increasing visual angle as one gets closer to the runway. Upslope runways intensify this illusion, Even when the Precision Approach Path Indicator (PAPI) lights indicates a too low approach, the dark night combined with an upslope runway creates a strong height illusion for the pilots. Approaches to Calicut and Mangalore are typical examples of Black-hole approaches. 7 P a g e

9 November Edition 66 SAFE WINGS Night Flying Hazards And Mitigation Measures: 1. Avoiding Taxi Incursion and Collision at Night: Because the quantity and quality of outside visual references is greatly reduced, a pilot tends to focus on a single point, making him or her less aware of the other traffic around. Therefore pilots should make a special effort to devote enough time to scan for traffic. Effective scanning is accomplished with a series of short, regularly spaced eye movements. If the pilot detects a dimly lit object in a certain direction, the pilot should not look directly at the object, but scan the area adjacent to it, called off-center viewing. This will decrease the chances of fixating on a particular set of lights and allow focusing more on the objects (e.g. aircraft, ground lights, markings, etc.) 2. Avoiding Visual Illusions on Approach: (a) When flying an Instrument approach (ILS or Non-ILS), even in good visibility, avoid transitioning to the visual segment before the DH/MDA. Pilots have often mistaken other lights such as a brightly lit road or fence, a parallel runway or taxiway for the landing runway. (b) Even after transitioning to the visual segment, continue monitoring and tracking the localiser and glide slope and scan the air-speed, rate of descent and thrust. (c) If localiser and or glide slope is not available, continue tracking the LNAV and VNAV path even after transiting to the visual segment along with raw data glide path monitoring ie 300 feet per NMi from touchdown. This distance can be programmed on the fix page. Remember the VOR/DME is usually not co-located with the touchdown point and VORs are progressively being removed ( eg Dubai and Sharjah). VOR approaches are being replaced by straight in RNAV approaches which are safer and similar to ILS approaches but with higher minima. (d) Do not get fixated with visual cues but continue scanning in and out throughout the approach. An up-slope in the runway or a hump on the runway ( eg. r/w 10 at Calicut) should not then cause an illusion. 8 P a g e

10 We give utmost importance to your valuable comments and feedback. Please do mail us at or PROMISING A SAFER SKY, AIR INDIA, AIR INDIA EXPRESS & ALLIANCE AIR Editorial: Capt V Kulkarni, Bhavish B S Designed by Bhavish BS