Typhoon Operations - Human Factor Considerations


Typhoons provide us with the opportunity to compare how different performers attempt to balance customer service requirements against safety considerations unique to the airline industry. In everyday operations airlines, airports and air traffic services strive to provide as an efficient service as possible to the travelling public whilst ensuring their safety. In order to ensure this safety many different safety nets are put in place. This includes the management of fatigue levels, aircraft operating procedures, airspace corridors, maximum weather limits, planning minima and so forth.

Whilst these are in place continuously an event such as a Typhoon allows the opportunity to see how realistic, practical and flexible these safety measures are. Furthermore it allows us to see how far certain performers are willing to push other performers to exceed their own set limitations.

We will now consider the issues for 4 prominent performers affected during operations at Hong Kong International Airport: Airline Management; Flight Crew; ATC and Hong Kong International Airport staff.

Actual Impact Study - Typhoon Vicente

Typhoon Vicente struck Hong Kong on July 23, 2012. It grew from a Category 1 typhoon to Category 4 in under six hours with sustained wind speeds of over 140 km/hr. The Hong Kong observatory raised the number 10 signal, its highest warning and the first one since Typhoon York in 1999, in the early hours of Tuesday morning. The results for airline operations were significant. The figures from Cathay Pacific alone show the level of disruption - Monday saw 23 flights cancelled. Tuesday 31 flights cancelled and overall 22 diversions for inbound aircraft (5 to Bangkok, 2 to Manilla, 4 to Kaohsiung, 2 to Inchon, 1 to Haneda, 1 to Kansai and 1 to Xiaman). Wednesday saw the cancellation of another 27 sectors. At one point, Cathay Pacific had nearly 7,000 passengers stranded airside at the airport (CX News, 2012)

Airline Management Considerations

One of the over-riding considerations for Airline Management is the balance between Productivity and Safety. The approach of a Typhoon carries with it potential disruption to flights and loss of productivity. The overall aim of management is therefor to limit flight disruptions and minimise the economic costs. These economic costs can include:

  • Increased fuel costs - as flights manoeuvre around weather, divert, carry more diversion fuel etc
  • Increased staff costs - flight crew may go into overtime with diversions, staff called off reserve etc
  • Accommodation - cancelled or delayed passengers may have to go to hotels at the airlines expense
  • Loss of goodwill - passengers who feel badly treated may switch to other airlines. Flight Delays and cancellations need effective communication to passengers to reduce confusion and stress.
  • Increased airfield penalties - flights delayed into or out of certain airports charge penalties if flights do not utilise thier gate or 'slot' times.

When carefully managed with pre-planned strategies these costs can be limited to a degree. For example if a Typhoon is approaching, crew and staff can be placed at en-route airfields to take over from inbound crew. In the case of Hong Kong, with flights arriving from all points of the compass, flights can be diverted to airfields according to their inbound tracks. Manilla, Bangkok and Taipei are all utilised.

The issue of economic loss vs potential safety issues arises when the plan is not actioned. i.e the storm changes track unexpectedly or intensifies rapidly. In this case the management of aircraft and crew switches from proactive to reactive.

Crew Management

The primary vehicle for controlling daily operations is a central control operations room (crew control). It is important to note that their primary focus is maximising the productivity of crew within the legal bounds of the negotiated roster agreements. Doganis (2006) reminds us that within its own operational and institutional constraints, Management is under constant pressure to increase productivity of its employees. This depends largely upon the negotiated work practices or rostering agreements in place defining such things as maximum flight duty, length of rest periods, reserve callout procedures and so forth.

Importantly many of the negotiated rostering practices will be derived from legislation or regulations issued by the governing aviation authority. The independence the national aviation body and a reasonable unionisation of the workforce are critical in balancing the productivity drive of management.

The second important facet is that it is unlikely that corporate safety will be represented by any individual in crew control. So long as crew control operate within the letter of the law the sole responsibility for ensuring fitness to fly (including fatigue, mental stress etc) and the legality of the duty, rests with the licence holders- the crew.

As an example of what is legal but also highly tiring take the following roster for an Austrlaian based crew member (Australian time in Brackets)
Day 1 : Sign-on Melbourne at 0640 arrive Hong Kong at 1515 (1715).
Day 2 and 3 : Sign-on Hong Kong 1905 (2105) arrive Delhi at 2335 (0435). Arrive at Hotel approx. (0635).
Day 4 : Sign-on Delhi 0135 (0605) arrive Bangkok 0805 (1105) then depart Bangkok 0920 (1220) arrive Hong Kong 1315 (1515)

It is also worth noting that although the departure time from Delhi was at 0605 Australian time the actual wake-up call in the hotel for the crew was around 3 in the morning. So having lost 2 nights sleep in a row, then having flown 2 sectors from Delhi what condition are the crew in to deal with the severe weather of a Typhoon? If one was forecast should they consider staying in Bangkok even though they are well within the controlling legal limits to attempt an approach?

It has been established that such patterns as described above lead to a cumulative deterioration in behavioural alertness and cognitive functions. Also that the impairments caused by a lack of sleep or circadian mis-alignment are further compounded in a heavy workload environment (Mallis et al, 2010). The potential for mistakes in a crew operating in Typhoon conditions, particularly in the critical approach and landing phase of flight needs to be carefully considered before the crew depart.

We can therefor add one more factor crew must consider before either signing on before a flight and airborne inbound to an airport under typhoon conditions.


There are many aspects of modern airline operations that make aircrew vulnerable to safety issues. Crew operate in a shift environment and may invlove working through the night followed by day flights. Often the rest periods prescribed are during daylight hours when actual rest is problematic. Coupled with this, in the case of Cathay Pacific, crew are based all over the world such that at any given time in Hong Kong you can have crew on Australian, New Zealand, North American or European time zones.

A crew inbound to an airfield under Typhoon conditions may have just flown 13 hours across the Pacific or 2 hours from the local region. For the crew leaving from the USA into Hong Kong they are already at maximum fuel loadings just to reach Hong Kong so the ability to load more fuel for lengthy holding may not be feasible. Similarly the maximum duty (for example 18 hrs) means that if they divert to another airfield they will be out of duty hours and be forced to ground the passengers until the crew has rested or another crew can be arranged.

It is highly likely that these crews will face a potent combination of safety issues. High fatigue, low fuel, bad weather and the latent stress of the high possibility of a divert. The defence against this is careful briefing and planning as early as possible, however, as we know Typhoons can intensify and change direction such that crews find themselves facing conditions they neither expected or planned for.

Similarly crews departing from the airfield may find that they sign on to duty but then face delays of many hours before actually boarding the aircraft, due to the delay of inbound aircraft, and many more hours before actual departure. Once on-board they may find passengers that have been waiting for lengthy periods and aircraft not yet serviced. For a day time flight this is just a long day but for a crew signing-on at midnight they may not actually get airborne until 5am. They have faced a night of work before they even start the process of actual aviation. At what point should the crew advise they are unfit to continue? Consider the subtle pressure of having 200 passengers who have been stranded at the airport for 24 hours already. How would they react to the crew walking off the aircraft because the delays have caused fatigue or compromised crew duty?

Co-operation Considerations

Not to be overlooked is the current state of relations between management and crew. If the relationships between management and crew is positive then the crew are more likely to assist the airline by extending into discretionary duty times and coming in to work on Rostered days off to mitigate crew shortages. Conversely if relations are strained or union action is taking place, many of the problems faced by crew control will be exasperated by requiring more crew to cover those not extending whilst being unable to contact off-duty crews. The more aircraft that are unable to get airborne or return to home port, the escalation of costs involved.

If co-operation levels are high then staff will be more pro-active in assisting and may feel proud to have done 'their bit'. Given that in many cases passengers will be looking for information and assistance from front-line staff the difference between pro-active, helpful and positive interactions versus surly and uncaring will have significant ramifications.

It raises the issue of whether high levels of co-operation are beneficial to safety in a Typhoon situation. If relations are poor-average then staff may feel more secure or justified in turning down a potentially compromising duty. By not extending into discretion, by walking off the aircraft despite the anger of passengers they may in fact be taking the safer course. However, staff who feel a high sense of dedication to the airline may be more inclined to push on to the very limits of legality. Whilst this may feel like the 'right thing to do' and is technically legal, it may be setting them up for a poor operational performance.

Air Traffic Control

Hong Kong Airspace is very limited and Hong Kong ATC suffer from a lack of co-ordination with its many neighbours, the Phillipines, Taipei, Sanya, Zhuhai,Shenzhen and Guangzhou. It is important to realise that although 5 of the centres all belong to the PRC, China still operates in zones who consider themselves independent. Unlike Europe where direct routing is available from the Baltic to the UK, in China you are unlikely to get any direct routing and if you do it will only be to the boundary of the next control zone.

Also flights to/from Taipei are restricted to a very narrow corridor as flights cannot deviate to the west due to Chinese airspace.

The following are all threats to efficiency and safety on a daily basis within the Pearl River Delta

  • heavy congestion
  • a lack of corridors for manoeuvre
  • lack of ATC experience in the region
  • differences in operations and procedures (SOP's) in ATC units
  • heavy military dominance limits available airspace
  • close proximity of 5 airports ( Macao, Shenzhen and Zhuhai are within 60km of Hong Kong, Guangzhou about 140km)
  • conflicting runway orientations
  • lack of ATC co-ordination and direct communication

It was estimated that the extra fuel costs due to congestion and inefficiencies in and out of Hong Kong in 2006 was HK$600 million annually. Also that the number of delayed flights was over 3000 and 7 out of every 10 Dragonair flights to China were delayed (Cheung et al).

Given that the system is already strained in airspace and aircraft movements there is little flexibility to handle the extra complexities of severe weather effecting the airspace. With the volume of traffic inbound to Hong Kong (the worlds busiest cargo gateway and one of the top 10 busiest airports in the world) it does not take long for holding patterns to become full.

Little room for Manoeuvre

Apart from a lack of airspace in which to accommodate deviating aircraft and controlling one of the busiest airports in the world, the number of controllers available has caused concern. On Sept 18, 2011 bad weather saw aircraft in long holding patterns and starting to complain of fuel minimums. It was a sunday so extra staff could not be called in and supervisors were involved in actively manning screens instead of providing a managing function. The strain on the approach staff ultimately led to two near misses requiring aircraft to actively follow the TCAS collision avoidance system. One controller and then a supervisor were relieved due to the stress of the incident (Siu, 2011).

From a human factors view point the extra stress placed on controllers from Typhoon conditions could easily lead to critical mistakes in directing aircraft. At a time of high workload oversight management is crucial. It is needed to manage fatigue/ stress levels that may well increase to dangerous levels faster than standard work and rest periods were designed for. It is also needed to check potential mistakes caused by a more dynamic environment i.e multiple aircraft requests, diverts and delays. If productivity has been placed at a much higher premium than safety through minimum staff and inadequate resources, then weather phenomena such as Typhoons will pose a much more deadly threat.

Airport Operations

Although it may not seem like it, one of the most restrictive areas is operations on the airfield. When the No.8 signal is hoisted in Hong Kong all public transport ceases and everyone is released from work to go home. That means many airport workers do not come in for work or are unable to do so. Without refuellers, caterers, mechanics, check-in staff and security personnel the airport ceases to support flight operations.

Of primary concern is the safety of those working on the ramps. Already a highly dangerous area due to vehicles, aircraft, noise and machinery the effect of high winds and heavy rain make the working environment critically so. The lightning warning system also mandates that all ramp functions cease in a red warning further delaying aircraft getting onto and off gates.

Catering trucks are especially susceptable to high winds given the height they extend up to get to aircraft doors.

Here we see the effect of the reliance of one set of performers on another. Without catering and cleaning aircraft cannot depart on time. However the safety limits of the ground personnel, or their equipment may be less then those of the aircraft they service.


For example an aircraft may be able to take-off in 50kts of wind but the catering truck needed to get the aircraft ready for that take-off may have an operating limit of 30kts.
As aircraft are delayed leaving their parking bays, incoming aircraft have no where to park and turnaround for the next flight and so the effects flow through.

Feedback will now play a critical role in managing the situation. Airport managers, airline managers and ATC are dependent upon timely information regarding aircraft states. Only when the limiting factors are discerned are managers able to solve the problems associated with Typhoon conditions. For example if Airline Operations are aware that it is only catering stopping a flight departing they can decide if it can leave without it. Is catering neccessary on a 2 hour flight to Shanghai compared with a long haul to Europe where it becomes very much a safety issue for the crew.

Conversley if operations on the ramp are halted by Lightening warnings the airline managers have no leeway to influence aircraft servicing. It is now dependent on the its communication and co-operation feedback loops from other agencies to let them know when aircraft will be ready to move again.


The above areas demonstrate some of the issues surrounding operations in Typhoon conditions. By no means exhaustive they demonstrate some areas that need to be considered more carefully. The principle performers and organisations each have different challenges but are also dependent on one another to collectively manage the situation. Feedback loops and communication channels are vital to ensure problems are recognised and understood. Finally, as each has their own safety regulations in place it is important that these are robust enough to withstand the challenges Typhoon conditions produce and the pressures other organisations may apply to achieve their own goals.

As a final example of the dangers of Typhoons, attached is the video of China Airlines Flight 642 attempting to land during a Typhoon in Hong Kong on Aug 22, 1999. China Airlines also lost a 747 during a severs storm in Hong Kong in 1993 (Flight 605)

China Airlines Crashes in a Typhoon

Doganis, R.(2006). The Airline Business (2nd ed.) Routledge. Oxon : UK. Mallis, M., Banks, S.,Dinges, D.Aircrew Fatigue, Sleep Need and Circadian Rythmicity. In Human Factors in Aviation (pp.401-429) 2nd Ed Salas, E. & Maurino D (2010). Elsevier : London. Siu, P. (2011)Wing and a PrayerThe Standard Friday October 14, 2011. Cheung K, Japhet S, Dicky Siu Man Tse (2008)An Investigation of Airspace Congestion & Possible Air Traffic Management Integration in the Pearl River Delta Region of Southern ChinaAviation Policy and Research Center, The Chinese University of Hong Kong, Shatin, New Territories. CXWorld. Magazine for Staff and Friends of Cathay Pacific Airways. August 2012 Issue 197 Traffic Movement figures HKIA HKIA Information
1. full reference in the following format AUTHOR (date work). Title. Reference location, date publication.
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