Tabletop Airports, Rough Weather, Runway Excursions — Expert Pilot On Nitty-Gritty Of Flight Safety
Swarajya speaks to an ace pilot to ascertain what can be done to up aviation security, in the aftermath of the recent Kozhikode air crash.
The crash last week of the Air India Express flight at the Kozhikode Calicut International Airport has sparked conversations around aviation safety.
Comparisons with the 2010 Air India Express crash at Mangaluru, Karnataka, have led to apprehensions over “tabletop runways” — those that sit on elevated terrain and taper off on the sides.
The crash has now forced a change — wide-body aircraft have been prohibited from operating in the monsoon at Kozhikode; however, the Boeing 737 flight that overshot the runway and went down into the gorge was a narrow-body aircraft.
Globally, runway excursions are on the rise and have become a top aviation safety concern.
Even in India, the 2019 monsoon season offered up several instances of planes overshooting the runway.
The most recent, notable Indian case before the Kozhikode incident was of a FedEx plane overshooting the runway at Mumbai airport during cyclone Nisarga in June this year.
Clearly, aviation safety requires a closer look.
For insights, this writer reached out to an experienced airline pilot who goes by the name of “Mentour Pilot” online.
Mentour Pilot is a captain and ace flight instructor who has clocked over 10,000 hours on the Boeing 737.
On the condition that he wouldn’t speculate on the Kozhikode air crash — he wisely advised everyone to wait till the findings of the investigation team emerged — and would, instead, speak more generally, he answered some of the pertinent questions that have come up this past week.
Here’s the exchange with Mentour Pilot:
1) Most of the talk in the aftermath of the crash has been around tabletop runways and the challenges they pose for pilots. Could you give us your perspective on this — both in ordinary circumstances and in times of heavy rain and tailwind?
Personally, I have no problems with “tabletop” runways. To a certain extent, they can cause turbulence at a low-level due to the winds blowing over the topography, but the fact that the runway is on a hill should not cause a problem.
Professional pilots are required to calculate their landing distance very carefully before landing on any runway.
We never look at the area after the runway ends because we should never end up there. In this case, there is also a 150-metre RESA (Runway End Safety Area), which is created to enable the aircraft to stop on in case the runway wasn’t enough; that area should also never be touched, but it is there as a last safety buffer in case something goes wrong.
The key here is proper landing distance calculations before the landing and careful execution of the landing itself.
If the aircraft is not able to land within the landing zone (the marked area on the runway), an immediate go-around must be executed (Provided the reversers haven’t been selected. Once the reversers are out, the pilots are committed to the landing and no go-around is possible any more.)
Any landing outside this touchdown zone will render the landing calculations useless as the pilots would not be able to assess how much runway they have left to decelerate on.
It is also critically important that the state of the runway is accurately assessed and passed on to the pilots. There is a huge difference between a dry and a wet runway in terms of friction and it's an even bigger difference between a wet and a flooded runway.
In case a runway is flooded (more than 3 mm of standing water), there is a risk of aquaplaning, which will make the braking effectiveness close to nil. If that is the case, and the pilots are made aware of it, they would not land on that runway, unless it is extremely long and the landing calculations support it.
Connected with the braking assessment is the amount of rubber deposits that is present on the runway.
Rubber deposits can become very slippery when wet, but they are rarely a big problem since they tend to be present only in the respective touchdown zone to a large extent.
Use of all the aircraft deceleration aids is also hugely important, like its spoilers, brakes, and reversers. In case of landing on a slippery runway, they all need to be activated as soon as possible after landing and used until a safe landing is assured.
2) You have pointed out that despite the advancements in aviation safety, runway excursions have been rising over the years. From your experience, what factors may be contributing to this increased risk?
It is very hard to pinpoint the exact reason for the increase in runway excursions. If we knew this, we would immediately start to deal with that reason.
Factors we have seen in previous excursions have included unstabilised approaches, landing too far down the runway without executing go-arounds, late application of reversers on slippery runways, and the acceptance of high tailwinds on wet runways without proper landing calculations.
These are all human factor reasons and could possibly be attributed to perceived time pressure (get-there-itis) or a lax attitude towards established safety rules like stabilised approaches and landing distance calculations.
These are all general reasons for runway excursions; we will not know what has happened in this particular case (Kozhikode air crash) until the accident investigation team has done its job.
3) Besides the challenge of landing on a tabletop runway, the Air India Express that crash-landed in Calicut had to contend with heavy rain. Reports say the plane skidded off the runway. Could this have been a case of aquaplaning? And what options does a pilot have if he or she thinks the runway is flooded?
A pilot can always decide not to land if the weather or conditions dictate that as being the safest option.
This is, however, dependent on accurate assessments of weather and runway conditions from the airport. If not happy, go around and divert to the alternative.
4) Unlike the 2010 crash in Mangaluru, India, with which this crash is being compared, this aircraft is said to have not caught fire after crashing and breaking in two, resulting in significantly fewer casualties. The speculation is that the pilots turned off the engine. Is this plausible? What other ways can pilots prevent the plane from catching fire?
No, this is highly unlikely. A pilot would never turn off a working engine inflight since that severely limits their options. Pilots work on a set of very determined procedures.
In case of a runway excursion or landing gear failure, we would first focus on stopping the aircraft, then assess the situation and evacuate if necessary.
There are no procedures that instruct us to shut down engines prior to or during a landing attempt.
After the aircraft has come to a stop, we have a checklist that instructs us to, among other things, shut down the engines to facilitate an evacuation. It is very possible that, if one of the pilots was still conscious, he could have executed parts of that checklist after the aircraft had stopped.
When it comes to shutting down the engines, as seen from the pictures, it would make very little difference since it seems the engines had separated from the wings.
Luck is the only thing that stops a fire from breaking out in an accident as severe as this one, where you have the aircraft breaking apart.
5) Do you think technology such as EMAS is going from optional to necessary with the increase in runway excursions? What other improvements can be made, either in piloting or technology, to make aviation safer over this decade?
Since most runway excursions are caused by the human factor, this type of accidents can mainly be avoided through training and emphasis on proper approach and landing techniques and the enforcement of a no-blame policy for go-arounds.
Proper assessment of runway conditions during heavy rain should also be implemented and clearly communicated to the flight crew so that they can accurately predict aircraft deceleration after landing.
EMAS can be a good thing on runways where an excursion could lead to an increased risk to the aircraft as compared to other runways.
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