Modern jetliners start the descent from cruising altitude i.e. 30,000 to 35,000 feet i.e. 9.1 to 10.6 kilometers (kms) and slow down from its cruising speed of around 400 to 500 knots i.e. 740 to 925 kms per hour true airspeed when it is around 160 kms from the airport. The gradual reduction in speed and altitude enables the aircraft to arrive at the runway at a safe speed of around 135 knots i.e. 251 kms per hour to execute a safe touchdown. Air traffic control directs the aircraft towards the airport through a series of instructions to change heading (direction of flight), height and speed until the aircraft can begin its approach to the runway. The instrument landing system (ILS) is critical in carrying out a safe landing. While providing both lateral positions relative to the runway as well as its position with respect to the ideal glide slope i.e. the angle at which the plane descends, the ILS executes a typical approach following a three-degree glide slope. The descend on the glide slope, steady deceleration to arrive at the target approach speed depending on the aircraft type and configuration, is the traditional process followed.
The ideal approach is directed towards becoming stabilized i.e. identifying and precisely following the ideal glide slope with controlled speed and correctly configured aircraft. at any point of time during this course of approach or landing, if the pilots consider it unsafe to continue due to poor positioning, an occupied runway or unstable approach, they opt for a go-around. This is followed by a climb away from the airport on a prescribed path on full power to set up another approach or divert to another airport.
Engaging some of the internal components are conventional ways of slowing down an aircraft after touchdown. These are the following:
- Applying brakes in landing gear wheels can produce enough friction to bring the aircraft to a standstill, but a high amount of heat produced can melt the tires
- Spoilers (rectangular plates layered and aligned with the wing surface) can be deployed to increase the wind drag. The spoilers deflect up against wind flowing around the wings restricting the lift component of an aerofoil, adding drag
- Thrust reversers are applied by reversing the direction of exhaust stream of the jet engine and use the power of the engine to decelerate.
However, deceleration may still be troublesome with standardized techniques in place and these slips may lead to catastrophes resulting in loss of life and property. The unfortunate incident of the crash landing of Flight AI 1344 from Dubai to Kozikhode, India on 7 August 2020 can be cited as an example.
Hypothetical explanation of the recent AI 1344 crash
The fateful Boeing 737-800 touched down at 315 kms per hour or 170 nautical miles per hour, overshot the runway and broke into three parts leading to the death of 19 persons on board, including the two pilots.
The pilot may have wanted to land from the eastern side which was not possible due to hostile weather. As a result, he switched sides, took a teardrop turn and attempted to land from the opposite direction anticipating opposing wind. However, in reality, the aircraft was subjected to wind acting from the back and increasing its speed. Furthermore, in hilly terrain near the sea, the wind pattern is unpredictable which rises upwards from low level to high level sometimes. Consistently, the sudden upthrust raised the level of aircraft during final moments of touch down. Additionally, touching the designated area of the runway with the elevated speed was difficult. The higher speed could not be reduced within the available time. Also, deposits of rubber from tires of aircraft which is sedimented during landing are required to be scrapped and cleaned at regular intervals to have effective braking system functioning which was not done recently at Kozikhode airport, making slowdown even more difficult for the pilot.
In both cases, an emergency ramp could have stopped the aircraft without damage to the chassis and similar other undershoot, overrun, or excursion from the runway incidents.
The Evolving R&D Ecosystem
Several innovations have been directed to addressing challenges associated with airliners overshooting the runway space. The initiatives toward improvements to be adopted in Runway Safety Areas (RSA) is not new. Around 5 years back, the FAA undertook several research works and recommended a wide spectrum of structural modifications such as an extension of 1000 feet long and 500 feet wide stretch at both ends of runway to provide to safeguard against probable aircraft overrun, undershoots or veering off the side of runway incidents. These modifications, however, are often impractical for several brownfield airports built a few decades back. There is often a dearth of land, adjoined populated areas, waterbody, highways, rail tracks or drop-offs in terrain coming in its alignment.
A possible solution would be placing a bed of engineered materials, termed Engineered Materials Arresting System (EMAS), at the end of the runway. The adequate choice for this, as specified in the FAA Advisory Circular No. 150/5220-22B, should be “high energy absorbing materials of selected strength, which will reliably and predictably crush under the weight of aircraft”. The tires of the aircraft sink into the lightweight, crushable material and the aircraft decelerated by the grinding as it rolls through the mass. The EMAS solution is capable of stopping an aircraft speeding at up to 130 kms per hour, from overrunning the runway with less than 600 feet of RSA length.
Complex Maintenance can discourage airport authorities to install EMAS Bed
The current EMAS structure consists of multiple concrete blocks sealed in between by sealants. Considering its usage, the materials used for sealing joints should be capable of withstanding expansion/ contraction due to temperature changes as well as jet blasts. Furthermore, moisture creeping in into the EMAS structure, as well as hardening of sealant can cause faster degradation of the sealing tape. Also, instances of efflorescence between blocks can result in leaching out of the vent holes. Last but not least, hostile climatic conditions can aggravate the EMAS condition due to pealing of coat, necessitating re-painting of the EMAS surface and re-caulking of joints.
The cost of any aircraft overrun can have segmented into the following components (considering a sample of 100 runways across multiple airfields):
- Aircraft repair cost: Repair cost which can be minor (15%), moderate (50%) and major (80%) of market value
- The Substitution/Lease cost: This ranges from 1.6 to 3.75% of the market value per month. For a 5-year-old aircraft considering 63% market value and 2% monthly lease price
For a new Airbus A320 costing $100 million: Considering 63% as present value after 5 years, 2% per month = $1.25 million per month
For a new Boeing 777 costing $305 million: Considering 63% as present value after 5 years, 2% per month = $3.8 million per month
- Closure of runways resulting in delays and diversions:FAA estimates this as $24 for ground delays and $36 for delays in air. With 40 departures per hour ground delay costs around $53,000 per hour.
As per IATA, diversion cost for narrow-body and wide-body jets are approximately $15,000 and $100,000 resulting in moderate size and major hub airports to spend $600,000 and $20 million respectively.
4.Repair of runways for aircraft excursion: This includes removal of debris, wreckage, re-construction of the strip, EMAS, RSA, lights, instruments etc.
- Loss of Revenue:Runway usage i.e. landing fees passenger fees and taxes are estimated as $5000 per aircraft. Closing a runway, thus, would cost $4 million (50 movements/hour/runway) per day of 16 hours for a major hub airport. This would be $200,000 for regional airports ($1000 per movement for 200 movements per day) for a regional airport.
6.Financial Compensation for flight delays: Depending on type and flight, the compensation can range between 250 to 600 euros i.e. $295 to $708 per passenger. It may be assumed that a regional flight carries about 100 passengers on an average and 6 stretches while international flight carries 300 passengers for 2 stretches. Considering above, the total estimated costs without EMAS are thus, over $1747 million, whilst the estimated accident costs are $283 million; denoting a saving of $1464 million. Standard EMAS is estimated at $5 to 7 million, totalling the worldwide EMAS installations costs at $700 million for 100 runways, resulting in $764 million of net savings.
A quick calculation based on an actual runway overrun
A 6-years-old Airbus A340-313E Air France flight 358 from CDG Paris overran runway 24L at Toronto Pearson with a speed of 86 knots, destroying the aircraft in a ditch/ravine. Toronto Pearson had no standard RSA, nor an EMAS bed. In case of presence of a standard EMAS bed, most of the destructive kinetic energy would have been neutralized causing only minor damage to the aircraft.
The runway excursion costs for this accident has been calculated as a total of $468.96 million. Had there been EMAS bed installed, the severity would have been a mere (hypothetical) $67.21 million. This is with an assumption that the airport would have invested $10 million for an EMAS bed on runway 24L, indicating net savings of $468.96 – (67.21+10) = $391.75 million.
Trends: Market consolidation monopolizing the technology landscape
The global technology landscape represents a couple of prominent and effectual innovations, represented as follows:
- Swedish-based Runway Safe developed its proprietary EMAS technology, the greenEMAS, featuring foam glass or recycled glass as the main arresting component. Foam glass, with its characteristic closed cell microstructure, makes the overall mass lightweight, chemical and water-resistant, as well as fireproof. A geotextile is placed over the foam glass, which is covered with a sheet of a material containing cement. Once the sheet is sealed, the surface is coated with an acrylic-based paint.
- US-based Zodiac Aerospace, now a part of French-based Safran, has been one of the pioneers of EMAS developments. Its innovative EMASMAX represented as a bed of cellular cement blocks enclosed in a cover is one of the most globally adopted passive solution. The bed is placed at the end of a runway, which reliably and predictably crushes under the weight of an aircraft, delivering consistent deceleration.
However, we can expect the market moving towards consolidation. The decent deal between Runway Safe Group and Engineered Arresting Systems Corporation (ESCO, a Safran Group subsidiary), around the acquisition of the ESCO EMAS (Engineered Material Arresting Systems) business further solidifies this claim. The combined entity, with extensive presence across the US and Europe, would create a global market leader with a robust and customizable product portfolio.
The road ahead is not free of speedbumps. Several airports are equipped with RSAs as specified in the ICAO guidelines and several airport authorities tend to question the practicality of the EMAS when standard RSA length has been maintained. Undertaking EMAS implementation projects in a brownfield setup would come with an entourage of roadblocks such as achieving cost competitiveness and addressing demographic shortcomings
While the EMAS sub-segment of the aviation vertical stages a rectitude of criticality with respect to safety, it also highlights white spaces which promise potential opportunities to stakeholders. Construction and engineering infrastructure companies with experience in airfield construction and materials science wherewithal can opt for the runway refurbishment projects. With a limited number of technologies in the market, engineering contractors can easily get their engineers trained and certified.
The aviation vertical has been experiencing tectonic shifts in the technology paradigm for a while now and the airport infrastructure segment is no exception. The world has witnessed several devastating crashes due to the overrun of commercial aircraft and accordingly, the adoption of EMAS is expected to metastasize. With an exponential rise in greenfield aerodrome constructions and widespread adoption of aerotropolis concepts, global aviation regulatory boards such as FAA are setting stringent safety measures as guidelines for the present, which are expected to be hardwired into the policies, close-fisted airport authorities would relinquish and adhere to this trend willy-nilly. The engineering contractors should buckle up to tap this growing market and upskill their workforce in material science clout to gain the first-mover advantage.
Disclaimer: The views expressed in the article belong solely to the authors, and not necessarily to the authors’ employer, organization, committee or any other group (including Industrial India magazine management) or individual.
Subrata Basu is a Vice President with a European EPC major and comes with over 40 years of experience in engineering consulting and execution. He has commissioned several high valued projects for both public and private sector clients in the oil & gas, power and steel industries.
Avimanyu Basu is a senior analyst with 10 years of experience in market research and consulting. He has executed several strategy consulting assignments for both public and private sector clients in APAC, Middle East and Europe in verticals like aerospace and defence, automotive and energy. Presently, most of his engagements revolve around outsourced engineering services.
1 knot = 1.85 kms per hour
1 euro = US $1.18
- The Hindu: Kozhikode plane crash, Pilots gave Calicut ATC no hint of danger, published 10 Aug 2020, accessed 17 Aug 2020, accessible at here
- Engineered Arresting Systems Corporation, published May 2011, accessed 17 Aug 2020, accessible at here
- SHS: A sure path into the future, published Dec 2018, accessed 17 Aug 2020, accessible at here
- My News Desk: Creating a market leader in runway safety, published 2 Mar 2020, accessed 17 Aug 2020, accessible at here
- Safe Runway GMBH: Estimated Cost-Benefit Analysis of runway severity reduction based on Actual EMAS Arrestments, by J.N.M van Eekeren, accessed 22 Aug 2020, accessible at here
- Popular Mechanics: The Runway Tech That Stops Runaway Planes, by Amy Nordrum, published 25 July 2014, accessed 28 Aug 2020, accessible at here
- AIN Online: Key West Runway Overruns Prove Value of Emas, by Curt Epstein, published 1 June 2012, accessed 28 Aug 2020, accessible at here