RESA
Re your question “If, … you arrived at visual to threshold and your TCH was going to be ~ 150' instead of the published 58', and given the conditions . . . what is the prudent course of action?”
The ‘stock’ safety answer is – go around. However, I suspect that there may be a few doubters and many more “what if’ers”. If so, these views could represent some of the human factors issues that relate to the circumstances, situation awareness, decision making, and importantly the risk assessment of options for action – land or go around.
In this instance I would argue that good background knowledge of the certification rules (and assumptions) would improve the choice of action.
First,
continuing to land will involve risk; the key judgment is how much. The certification margins for landing distance contain a small allowance for error; or in UK CAA English “variation in the values of various parameters from those assumed at certification”. Good guidance on these matters is in
AIC 11(P164)/98 ‘Landing performance of large transport aeroplanes’ (free download, but registration and cookies enabled required, then go to Publications, UKAIC , Pink safety related). Also see AIC 61(P195)/99 ‘Risks and factors associated with operations on runways affected by snow, slush or water’ Note the statement ‘For JAR-OPS performance purposes, runways reported as WATER PATCHES (25% cover) or FLOODED should be considered as CONTAMINATED’.
Thus with ‘all other things being equal’, a landing from a gross error of 100 ft high (150 ft @ threshold) the landing distance could be extended by 2000 ft (AIC11/98). Probably at most airports with long runways this increase would be accommodated and the crew would write-off their error against ‘normal exercising of judgement’ (shrug of shoulder) with increased braking / full reverse. However, if any other physical condition that affects a landing is ‘at variance with the assumptions’ then there could be no margin for any operating error or misjudgement. It is often the case that the misjudgement of the less obvious variables cause the greatest problems (different wind speed / direction from that used in the planned performance, runway surface (baseline mu), runway condition / depth of water). Then there is human skill; in the limiting conditions in the above scenario a landing would require a firm touchdown, prompt selection of spoilers / reverse, and use of MAX brake – at least until assured of stopping (another judgment).
The alternative option of
executing a go around at any time during the approach or even from the point of touchdown should involve far less risk.
This might be refuted by some Canadian operators due to the advice given in the poorly worded AC 0141 (13 May 1998), which implies that aircraft ‘may not be able to’ (my words) conduct the manoeuvre from a ‘low energy state’; whereas a better explanation might have been to add ‘without increased risk’ (which can be combated by appropriate crew skills). However the AC does correctly conclude “ … operators should review their operations to ensure that pilots and training personnel are adequately aware of the hazards inherent in and procedures for dealing with low-energy operations”, i.e. late go-arounds.
The fundamental basis of aviation is that all aircraft are safe to operate within the constraints of the flight manual and when flown as per the manufacturer’s operating instructions. Flying a go-around is safe; we must put aside any concerns of conducting an infrequently practiced maneuver, unfounded fears of lack of control, or inadequate performance, the next failure, etc; the flight deck is not the place for these negative personal attitudes that can bias situation awareness, judgment, and decision making.
From the environmental aspect, a go-around into a Cb is not a good option, but if essential, it is still safe; the aircraft will not breakup or be thrown into the ground by a downburst, provided the appropriate action is taken. Normally a Cb hazard is identified and avoided well before starting the approach this requires crews to consider the threat for the approach and landing, and the go–around route.
I would argue that the above supports the ‘stock’ safety answer – go around, it is the lower risk option. To reinforce this we must bias our judgment towards a go around (go around minded) on every approach. Our mind set should consider the definition of a ‘landing’ as “an approach without a go around”.
We have to dispel the subconscious pressures that come from of the routine objective of always landing, the background commercial pressures, peer pressure (fellow pilot or ATC) - ‘the stigma’ of a go around, and the natural human desire to help others – land on time, don’t divert, don’t foul up the traffic pattern, give the pax a smooth ride. We have to focus on the safety aspects of the flying task.
A decision to transition to a landing in marginal conditions constrains the aircraft to a short narrow strip of land without any flexibility in altitude, heading, distance or time; whereas a go-around leaves open reasonable options of heading, altitude, speed, and within fuel constraints distance, time and location, – many more options than for landing. The action or consideration of a go-around may involve more workload or personal delay and disruption, but that’s what we are paid for – too ensure the safe conclusion to the flight.
In reality, if you have decided to start an approach and there is someone ahead, the airfield is ‘open’ and you are visual with both the runway and the weather, and you have done something similar several times before, then it takes very strong willpower to overcome the human fallibility for error … ‘Press-on-itis’. For the aircraft to end up high at the threshold implies that something preceded it, a tailwind shift or gust that is not noticed. The PF may see this as a flight error that s/he attempts to correct, the crew are now suckered in and with the additional attention on the flying task, all of the good thoughts and safety considerations that where planned beforehand are put in the background and the crew continues the landing, after that it’s history.
I suggest that personal flight safety based around good technical knowledge is one way of combating the subconscious biases; there are many others, but if, ‘on that day at that time’ all the weaknesses in the defences come into line then not even the luck that we all use on a daily basis will save us.
Good planning, go-around mindedness, early decisions, zero tolerance to violation of SOPs (stabilised approach limits), and resisting peer pressure will help. But ‘on that day at that time’ it is only you against the aircraft and the elements.
I suspect that the investigation into the accident in Toronto will find that some of the above issues are contributory to the cause, if so I hope that they will be discussed and solutions considered rather than leave them, as many reports do, as just human factors / human error.
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