Security issues with utilizing increased descent path at airports

Is flying to Imphal airport Manipur state of India dangerous? The reply isn’t any. Nevertheless, there are threats to flight operations that are peculiar to this airport different comparable airports. Imphal has instrument strategy procedures for each ends of the runway, nonetheless one finish has an instrument touchdown system put in, which permits the plane to land below decrease prevailing visibility as in comparison with the opposite finish.

A steeper than regular glide path of three.5 levels
Tail winds on strategy
Propensity of some airline/crew to hold out decrease flap landings

The USA Federal Aviation authority security group has issued a bulletin which educates the pilots on the dangers related to a steeper than regular glide path. A 3.5 deg glide path at 1000’ above the start of the runway shall be 2 occasions extra prone to grow to be unstable(dangerous) between 1000’-500’. (FAASafety,AFS-850 20-04)

Operators ought to assist not conducting tailwind approaches on Steep Approaches, or GP larger than 3.0 levels.(IFALPA place paper on tail wind)

That is with nil wind and most flap setting. With tailwinds and a decreased flap setting, the danger will enhance even additional.

Tailwind-related overrun accident knowledge reveals that in 70% of the instances, the runway was moist or contaminated. Clearly, the mixture of tailwind and a slippery runway is hazardous and must be averted. (Karwal,2001)

The instrument touchdown system

A business jet plane flies an strategy for a runway utilizing the instrument touchdown system which is a precision strategy. This permits the plane to align with the runway centerline and in addition offers indicators for steerage within the vertical path. This vertical path is named the glide path and is often mounted at a 3 diploma angle emanating from near the runway landing level.

The three deg glide path ensures a managed descent at a vertical velocity which varies proportionally with the bottom velocity of the plane. The bottom velocity is the velocity of the plane with the impact of wind both pushing from behind(tail wind) or from entrance (head wind). With growing tail wind, the speed of descent needs to be elevated for the mounted glide path angle since it’s pushing the plane in the direction of the runway at a sooner price. Subsequently to unfastened the surplus top, the speed of descent needs to be elevated.

Stabilised strategy

Security specialists have coined the time period & stabilized strategy’ which is the standards that an arriving plane should meet at a 1000’ if flying with the help of devices. The important thing flight parameters being airspeed and price of descent moreover others. The speed of descent at or beneath 1000’ above aerodrome stage should not exceed 1000feet per minute or else it’s thought of unstabalised and unsafe. The strategy should be discontinued to mitigate the danger of an plane accident sue to runway overrun(tour).

The statistical abstract of business jet airplane accidents all over the world, between 1959-2016 (Boeing, 2017), reveals that 48% of deadly accidents and onboard fatalities by the part of flight happen in the course of the remaining strategy and touchdown. As per worldwide air transport affiliation (IATA) publication on unstable approaches (Unstable approaches 2 nd version, 2016), knowledge from 2011-2015 reveals that roughly 65% of all recorded accidents occurred in strategy and touchdown part of the flight, and Unstabilised approaches have been recognized as a consider 14% of those strategy and touchdown accident. Additional, 31% of runway/taxiway tour was a results of unstabilised strategy.

Steep descent ratio

Whereas the regulator mandates that the airways monitor 100% of flights for unstabilised strategy, the crew are the primary line of protection. The crew plans the plane descent and chooses the runway which permits them to fly the strategy safely. Nevertheless at occasions their superior abilities and choice making capabilities are required when the winds aren’t favorable and/or the glide path is steeper than regular. Lets study the instrument strategy at Imphal in Manipur state of India.

Imphal airport is surrounded by hills and is seated in a bowl. The hills represent as obstacles. It is a risk to security and procedures are drawn which make sure that the plane flies at heights which preserve them safely above all obstacles. In an effort to preserve away from obstacles, the instrument touchdown system is put in with a steeper than regular glide path of three.5deg as in opposition to the traditional 3deg.

The USA Federal Aviation authority security group has issued a bulletin which educates the pilots on the dangers related to a steeper than regular glide path. A 3.5 deg glide path at 1000’ above the start of the runway shall be 2 occasions extra prone to grow to be unstable between 1000’-500’. That is with nil wind and most flap setting.

Decrease flap settings are utilized by airways and its crew as a measure of gasoline financial savings since they generate decrease drag or resistance to the airflow. The flip facet being that the strategy velocity is elevated which might lead to a barely increased price of descent and an extended touchdown roll.

If we introduce tail winds and a decrease flap, the probability of an unstable strategy shall be a lot increased because of the elevated price of descent. Imphal airport has an instrument touchdown system at one finish of runway 04 solely. The strategy winds are normally tail winds and as a result of its geographical location it rains usually and the runway is moist. A moist runway makes it tougher for the plane to cease there by requiring an extended touchdown roll. A decreased flap setting additionally will increase the touchdown roll because of the decreased drag and better strategy velocity.

Worldwide Federation of Air Line Pilots Associations place on tail winds

Worldwide Federation of Air Line Pilots & Associations place on tail winds

Wind measurement of tailwindICAO Annex 3 offers wind measurement and reporting suggestions. Wind measurement and its presentation to the pilot inherently create inaccuracies and uncertainties. Wind measurement is neither accomplished on the proper place (the landing zone, remaining strategy path), nor on the proper time (time lag).

Wind knowledge are filtered, and the excessive frequency content material of the wind disturbances just isn’t represented. Not all wind modifications in route or velocity are measured and communicated as reporting thresholds are in place.Correct and dependable (tail)wind info must be measured and reported to the cockpit, based mostly on anemometers for every runway.Wind info shouldn’t solely embody the landing zone but additionally be consultant for the ultimate strategy.Particularly, variations in wind route can quickly enhance the utmost tailwind part. These variations must be intently monitored.

ICAO Annex 3 states that wind should be measured and will not be mathematically derived or augmented, al-though this might produce extra correct and constant wind knowledge for the strategy path and landing zone.IFALPA helps the analysis and growth of a mathematically-derived wind worth to include the strategy path and increase touchdown zone winds and to enhance the anemometer siting. If derived and precise wind values can be found in future, utilization must be assessed.


Method procedures must be designed in a manner that enables pilots to execute protected flights in response to stabilized strategy standards. A secure strategy reduces the probability of a protracted flare, a protracted touchdown and runway excursions, particularly throughout tailwind situations and in opposed climate and runway situations.

The landing aiming level must be outlined as goal.

Pilots must be skilled in following a constant go/no-go decision-making course of based mostly on clear operational standards for tailwind and lengthy landings, probably assisted by technological aids. Operators must be inspired to refuse land and maintain brief operations (LAHSO) with tailwinds.

Operators ought to assist not conducting tailwind approaches on Steep Approaches, or GP larger than 3.0 levels.

The information is indicative of a variance in using flap setting used for touchdown at Imphal Airport. Airline B has constantly decrease vertical velocity recorded between 800-500’ AAL. Airline A makes use of A321 plane along with A320. Airline C has most variety of vertical velocity tour past 1000’/min indicating using a decrease flap setting. The winds on strategy are tail winds. The exceedance is at about 28%, the speed is way increased than what the regulator targets as acceptable within the state security plan.


Danger can’t be eradicated from aviation however may be managed. There are a selection of ways in which this may be achieved.

The wind and runway situation knowledge accessible to the crew should be as correct as doable.
Crew should elect to make use of probably the most favorable runway for strategy and touchdown.
Crew coaching should concentrate on the position of pilot monitoring and normal name outs.
Resolution making course of should be enhanced to mitigate the danger of unstable approaches and the insurance policies should be worded in consonance.
Compounding elements of upper glide path angle, tailwinds and decrease flap settings should be thought of as lively danger and a possible for an accident.



Views expressed above are the writer’s personal.


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