Tuesday, November 26, 2013

Stall Recovery Template issued by FAA in June 2012.

Relevant extracts of FAA Advisory Circular 120 - 109 dated 08 Jun 2012, based on the Colgan Air, Air France and other stall related accidents at high and low altitudes.


1. Autopilot and autothrottle………………………………..Disconnect

Rationale: While maintaining the attitude of the airplane, disconnect the autopilot and autothrottle. Ensure the pitch attitude does not increase when disconnecting the autopilot. This may be very important in out-of-trim situations. Manual control is essential to recovery in all situations. Leaving the autopilot or autothrottle connected may result in inadvertent changes or adjustments that may not be easily recognized or appropriate, especially during high workload situations.

2. a) Nose down pitch control…........................................Apply until stall warning is eliminated
 b) Nose down pitch trim…….………………………..….As Needed 

Rationale: a) Reducing the angle of attack is crucial for recovery. This will also address autopilot-induced excessive nose up trim.
b) If the control column does not provide sufficient response, pitch trim may be necessary. However, excessive use of pitch trim may aggravate the condition, or may result in loss of control or high structural loads.

3. Bank…………………………………………………..…….Wings Level 

Rationale: This orients the lift vector for recovery.

4. Thrust …………………………………………….………….As Needed 

Rationale: During a stall recovery, maximum thrust is not always needed. A stall can occur at high thrust or at idle thrust. Therefore, the thrust is to be adjusted accordingly during the recovery. For airplanes with engines installed below the wing, applying maximum thrust may create a strong nose-up pitching moment if airspeed is low. For airplanes with engines mounted above the wings, thrust application creates a helpful pitch-down tendency. For propeller-driven airplanes, thrust application increases the airflow around the wing, assisting in stall recovery.

5. Speed brakes/Spoilers……….…….…………………………..Retract 

Rationale: This will improve lift and stall margin.

6. Return to the desired flightpath.

Rationale: Apply gentle action for recovery to avoid secondary stalls then return to desired flightpath.

Saturday, July 13, 2013


The recent unfortunate accident involving Flight 214, a Boeing-777 aircraft, of Asiana Airlines at San Francisco is a case of a fully serviceable aircraft flying in to the ground in VMC conditions; due to an approach that became increasingly unstabilized with height. Could this accident be averted, had the crew taken a timely decision to go-around? Conditions being VMC, as per the recommendations enumerated below, the approach should have stabilized latest by 500 ft and should have remained so below 500’, to continue with an approach to land. As per reports, the airplane was configured for landing with 30 degrees of flaps and gear down with a target threshold speed of 137 knots. The aircraft descended through an altitude of 1400 ft at 170 kts and slowed down to 149 kts at 1000 feet. The throttles were reportedly at idle and the auto throttle was armed. At 500 feet altitude, 34 seconds prior to impact, the speed dropped to 134 kts, which was just below the target threshold speed. Any speed below the target speed, the approach should have been considered unstabilized, especially below 500 ft in VMC. The situation was allowed to worsen further when the airspeed dropped significantly, reaching 118 knots at 200 feet altitude. Eight seconds prior to impact, the throttles were moved forward. Airspeed reduced further to 112 knots at an altitude of 125 feet. Seven seconds prior to impact, one of the crew members made a call to increase speed. The stick shaker sounded 4 seconds prior to impact. One second later the speed was 103 knots, the lowest recorded by the FDR. One of the crew members made a call for go-around at 1.5 seconds before impact. This was too late to prevent an accident off an approach that was unstabilized. Accidents during the approach and landing (ALA) phase account for a major percentage of all accidents.

Analysis of data collected by a go-around study being conducted by the Flight Safety Foundation’s (FSF) international and European aviation committees has shown that potentially 54 percent of all aircraft accidents in year 2011 could have been prevented by a timely go-around decision by the flight deck crew. Clarifying on the figure of 54%, the FSF director of global programs is quoted to have said that, “this is based on 65 percent of that year’s accidents being in the approach and landing (ALA) phase, and using our analysis that 83 percent of ALAs could be prevented by a go-around decision”. The study has also elaborated that “the majority of accidents over the last 10 years have occurred during the approach, landing and go-around flight phases. The study has also highlighted the fact that the lack of a go-around decision is the leading risk factor in approach and landing accidents and is the primary cause of runway excursions during landing. Yet, less than 5% of unstabilized approaches lead to a go-around.”

Unstabilized approaches have been attributed to various factors, which include company policies, human factors, weather, crew resource management, ATC and automation. The Asiana case can also be attributed to a number of these factors. The crew felt that the auto throttle should have maintained the speed at 137 kts; the PF and PM were not effectively flying and monitoring the flight path and parameters, which permitted the IAS to drop well below the target speed, and the throttles to remain at idle; company culture may have also come into play in this scenario; fatigue after a long flight due to improper work load assignment – there were four pilots on this flight; three of them in the cockpit during the approach. All of these factors that led to the unstabilized approach would have been taken care of, if the crew had made the decision to go around in time. When things are not as planned in aviation, it is always better to have height and speed in hand. In this particular case there were many issues that pointed towards an unstabilized approach. To understand this it is best to study the elements that constitute a stabilized approach.

Stabilized Approach

Stabilized approach concept is all about maintaining a stable speed, descent rate, and vertical/ lateral flight path in the landing configuration. It is felt that a stabilized approach would generally lead to a safe landing, as the crew’s awareness of the horizontal/ vertical flight path; the IAS and the energy-condition of the aircraft would lead to improved overall situational awareness during the approach. Also, flying a stabilized approach permits the crew to devote adequate time and limited human ‘attention resources’ to flying, monitoring, communications, weather conditions, systems check, and most importantly to decision making. As has been brought out earlier, 95% of unstabilized approaches do not lead to a go-around, and this has contributed to 54% of the total accidents in 2011, and the lack of go-around decision is a major risk factor in ALA. It is now an accepted fact that the decision to execute a go-around is no indication of poor performance.

Recommended Elements of a Stabilized Approach

The following recommendations are developed by the Flight Safety Foundation. All approaches should be stabilized by 1,000 feet above airfield elevation (AFE) in instrument meteorological conditions (IMC) and by 500 feet AFE in visual meteorological conditions (VMC). An approach is considered stabilized when all of the following criteria are met:

·                     The airplane is on the correct flight path
·                      Only small changes in heading and pitch are required to maintain the correct flight path
·                     The airplane speed is not more than VREF + 20 knots indicated airspeed and not less than Vref
·                     The airplane is in the correct landing configuration
·                     Sink rate is no greater than 1,000 fpm; if an approach requires a sink rate greater than 1,000 fpm, a special briefing should be conducted
·                     Thrust setting is appropriate for the airplane configuration, and not below the minimum power on approach as defined by the aircraft operating manual.
·                     All briefings and checklists have been conducted.
·                     Specific types of approaches are stabilized if they also fulfill the following:

    • ILS approaches should be flown within one dot of the glide slope and localizer
    • During a circling approach, wings should be level on finals when the airplane reaches 300 feet AFE.
    • Unique approach procedures or abnormal conditions requiring a deviation from the above elements of a stabilized approach require a special briefing.

For safety reasons, an approach that becomes un-stabilized below 1,000 feet AFE in IMC, or below 500 feet AFE in VMC should be discontinued and a go-around executedAlso, stabilized conditions should be maintained throughout the rest of the approach for it to be considered a stabilized approach. If the above criteria cannot be established and maintained at and below 500 feet AFE, initiate a go-around.


Considering the statistics and the facts enumerated above, it is felt that all efforts should be made to fly stabilized approaches, and if due to some reason an approach becomes unstabilized then the decision to go-around should be taken well in time. A well considered, and executed, go-around will go a long way in ensuring safe operations, and enhance safety in aviation.

Monday, July 8, 2013


A Boeing 777-200 of Asiana Airlines with 307 people on board crashes while landing on runway 28L at San Francisco, killing 2 people and injuring 180. The accident took place at about 11:28 am local time on 06 Jul 2013. As per initial reports coming through, the ILS Glide slope for the runway was non-operational for runway 28L at SFO. It appears that the aircraft came in low. Watching the debris trail on the runway, it appears that some portion of the aircraft touched well short of the beginning of the runway, let alone the threshold. Why? 

The aircraft has called finals at 7 miles and every thing appears normal. Has any failure taken place after that; the aircraft has encountered wind shear; or is it just a case of an undershooting approach with the tail portion of the aircraft hitting the snow wall - a vertical wall at the edge of the land/ water junction.

Awaiting further news on the cause of the accident - prima facie appears to be human error, with the aircraft making an undershooting approach in the absence of ILS glide slope information. No news about VASI or other visual approach aids. Weather at the time was VFR.

Wednesday, June 26, 2013


Introduction      What are Standard Operating Procedures (SOPs)? A letter by the US Federal Aviation Administration (FAA) aptly answered this question where in it was stated that, “SOPs are written, tested procedures that are applied uniformly and consistently within an organization and involve all aspects of flight, both normal and non-normal”. It further stated that “SOPs are widely recognized as a basic element of safe aviation operations”. Safety is one of the pre-requisites for mission accomplishment in aviation, and thus the importance of SOPs can never be under estimated.

Design of SOPs

The aircraft manufacturer provides the initial SOPs for the aircraft based on lessons learned from previous operating experience; analyses performed during design; experience gained during development and certification flight testing; and also experience from the route-proving program. These manufacturer-provided SOPs are adopted without change by an aviation organisation, or these are used as the basis for the development of customized SOPs that promote standardisation across the different aircraft fleets in service at the organisation. Company SOPs so developed reflect the organisation’s operating and training philosophies. Thus, SOPs represent the collective wisdom of the aviation community on how operations could be conducted safely.

To ensure safety, training and operations need to be consistent, implying that training and operations should both be conducted as per the SOPs. This can only happen if everyone in the organisation is convinced of the need to follow SOPs. Bringing about this awareness places a great responsibility on the flying supervisory staff.  Instructors and check airman of the operator are required to ensure that crews are made aware of the reasons for SOPs; are trained as per the SOPs, and are also required to enforce the same during routine line operations.

SOPs published by the operator normally include expected procedures that would be utilised during the flight profiles that are used by the operator, including pre & post flight procedures. SOPs lay down the most effective and efficient procedure to execute any task safely. New procedures need to be added to the SOPs, and redundant ones modified/ deleted based on requirements, and also based on experiences gained by the aviation community. To undertake this task, review of SOPs should be an ongoing task, ideally accomplished with suitable feedback from the end user, the flight crew.

All of this is done with an aim of ensuring safe aviation operations. It is now abundantly clear that safety is not dependant only on the training of the crew, but also on good crew coordination as well as optimum crew performance (or good CRM). This can best be ensured if the crew has a shared mental model of each task that is being undertaken. SOPs provide that vital link that can effectively ensure this shared mental model between crew members, with the least communications, because when every crew member is following SOPs, he/ she is aware of what needs to be done; when it needs to be done; and by whom.

To ensure that every crew member follows the SOPs, these procedures should be clear, comprehensive, and readily available to the flight crew members. In addition the crew members should be aware and convinced of the need to follow the SOPs. All this sounds logical but a study of aircraft incidents and accidents indicates that some of these have been caused due to the crew not following the SOPs.

Operational and Human Factors Involved in Deviations from SOPs

To ensure effective compliance with SOPs, it is important to understand why pilots intentionally or inadvertently deviate from the SOPs. In most cases of deviation from SOPs, the procedure that was followed in place of the published procedure seemed appropriate to the crew, for the prevailing situation, considering the information available in the cockpit at the time. However, it was later found that it was either inappropriate, or at best suboptimal. Experts cite the following factors and conditions as making it more likely that a deviation from SOPs will occur. Awareness of these factors can influence adherence to SOPs and may also be useful in developing corresponding prevention strategies.

  • ·         Corporate culture (e.g., the absence of company management’s clear commitment to SOPs and standardization; double standard practices)
  • ·         Ineffective or unclear company policies (e.g., regarding schedules, costs, go around, diversion, crew duty time, etc.)
  • ·         Inadequate awareness/ knowledge of, or failure to understand the procedure, or action (e.g., quality of wording or phrasing; procedure or action being perceived as inappropriate)
  • ·         Insufficient emphasis on strict adherence to SOPs during routine training and checks.
  • ·         Insufficient vigilance (e.g., due to fatigue)
  • ·       Distractions (e.g., due to cockpit activity)
  • ·         Interruptions (e.g., due to ATC communication)
  • ·         Task saturation resulting in fixation/ degraded multi-tasking ability or task overload leading to reduced attention.
  • ·         Incorrect management of priorities (e.g., lack of or incorrect decision-making model for time-critical situations)
  • ·         Incorrect CRM techniques, especially the absence of cross-checking, crew coordination or effective backup
  • ·         Personal desires or constraints (e.g., personal schedule, press-on-itis)
  • ·         Complacency or Over confidence

An Effective SOP

An effective SOP would need the active collaboration of all stake holders, at the formulation as well as the implementation stages. The following factors should thus be considered for creating effective SOPs: -

  •  All crew members should be aware of the reasons for the procedure, and should also be convinced of the need to follow the same. It is a known fact that when flight crew members are so convinced, then they are more likely to follow the procedure, and also offer valuable feedback to improve upon an existing procedure, or  introduce a new relevant procedure.
  •   All crew members should hold the belief that the procedure is appropriate to the stated flight situation, and would cover all the likely eventualities. This should be reinforced during effective training sessions conducted by the operator’s flight instructors/ check pilots.
  •  The procedure should clearly lay down what needs to be done, by whom (PF/ PM), and when it is to be done. Each crew’s responsibilities would thus be clearly delineated.
  •  The senior supervisors should set an example through word, and more importantly through their deeds that SOPs are to be followed. Any shortcomings/ misgivings about the procedure that are pointed out by the line crew should be discussed and remedial action initiated, if considered appropriate; otherwise the crew member should be provided feedback of the reason why the suggestion is not considered worthy of implementation.

 It has been seen that many a times SOPs are not consistently implemented, in that double standards are practiced by the crew and these are also condoned by the instructors/ check pilots/ managers. Flight crews follow the SOPs during training and check rides, but do it their own way during routine line operations. When this kind of a situation exists, it is an indication that the SOP is either not practical or effective for some reason. The reason for the deviation should thus be investigated and remedial action initiated.


Safety in aviation continues to depend on good crew performance. Good crew performance, in turn, is founded on standard operating procedures that are clear, comprehensive, and readily available to the flight crew. Development of SOPs is most effective when done by collaboration, using the best resources available including the end-users themselves, the flight crew. Once developed, effective SOPs should be consistently enforced during training as well as during line operations and ineffective SOPs should be continually reviewed and renewed. Double standards should not be permitted.

Thursday, May 30, 2013


Aircraft Operations and Communications

An aircraft comes in to regular flight operations only once it has been accorded regulatory approval, the whole purpose of which is aimed at providing an error free product. However, latent errors can still be present. The recent Boeing 787 battery snafu that led to the world wide fleet being grounded is a case in point. Even when the approval process ensures an error free aircraft, there are still chances of errors creeping in during regular flight operations because each individual aircraft is tended to by a large number of diverse groups. These errors can be prevented and safety & efficiency can be ensured only if all these diverse groups work as a team, which can only happen when there is adequate co-ordination between, and within, the various groups, viz. the flight crew, cabin crew, dispatch, Air Traffic Control, maintenance personnel, and others directly or indirectly connected with the safe operation of the flight. Communications is that vital link that helps in ensuring good co-ordination between all of these different agencies. Thus understanding communications is important for anyone connected with aviation, and more importantly for the flight deck crew, they being aviation’s last line of defence to prevent any mishap from happening.

Communication is a two way process, in which a message is sent out from the sender to the receiver; the receiver gives feedback; and this process continues in a loop until the same meaning is shared between the sender and the receiver. The message can be sent either verbally in the form of oral or written communications or through non verbal means like body language, gestures, postures, face & eye expressions, touch, etc. Communication is a concept that has been variously defined in text books. These definitions essentially characterise communications in terms of two basic issues, which are: -  

·         First, communication entails the transfer of information (facts, opinions, ideas, feelings, instructions, commands, etc.)  from the sender to the receiver
·         And second, communication entails the transfer of meaning from the sender to the receiver

Effective Communications

Communications are useful only when they are effective, in that the transfer of information from the sender to the receiver should lead to the same meaning being shared by each of them, at the completion of the transaction(s). This can only happen when the sender and receiver are both active participants in the process and thus entails a responsibility not only on the sender to obtain or elicit feedback in order to determine whether or not the communication was effective but also on the receiver, who is responsible to provide honest feedback. Or in other words, effective communication is a two way process, and is only effective when the desired understanding or action takes place. In the fatal Air India Express accident at Mangalore, the First Officer had thrice communicated to the Commander to go around, but no go around action was initiated by the Commander during the approach and touchdown phase. Would this communication be considered effective? In this paper we would only focus on effective communication between the flight deck crew.

Communications and Crew Resource Management

Effective communication between flight deck crew members is an essential tool for achieving technical, procedural, and also crew resource management objectives. The communication process amongst the flight deck crew fulfils many important functions. Research shows that these functions include:

·         The most obvious being the transfer of information in the form of checklists, logs, R/T, etc.
·         Interpersonal/ team relationships that are crucial in any highly effective team, primarily because humans are emotional, in addition to being rational beings
·         Working towards shaping predictable behaviour and expectations from the other crew members, through the medium of briefings and critiques
·         It helps the crew to develop a shared mental model about the location, spatial orientation, environment, aircraft systems, time and fuel; thereby enhancing situational awareness
·         It allows individual crew members to become aware of problems and to contribute effectively to the problem solving and decision-making process on the flight deck
·         It helps the efficient and effective management of the flight with optimum use of available resources, including the crew, through planning, implementing/ revising & monitoring the tasks; the environment; and the crew.

These functions are all crucial for safe and efficient flight operations and underpin the important role of communications on the flight deck. Research has shown that each message can have different content, depending on the circumstances. These circumstances could be whether we communicate face to face, or under high workload conditions, or on R/T, or through written messages or through gestures.

Face to Face Communications

In this kind of a situation, the message content is dependent just 7% on the spoken words. The major part of the message content is conveyed by the tone employed while speaking (38%); and on the non verbal aspects of communications (55%) like body language, eye & facial expressions, postures etc. The flight deck crew would encounter this situation when they come face to face on arrival at the dispatch and also during low workload periods, as in a long cruise on autopilot. It is important to remember that in such a situation, words of the sender convey very little meaning to the receiver, if they are not backed by the right tone and the non verbal cues. The message communicated during this interaction would be stored and all future interactions on the flight deck would take place keeping the sense of the stored communications in mind.

Pre-Flight Brief:  Face to face communications normally include a pre flight brief. A good pre-flight brief is very important because it effectively touches nearly every function of communications that are enumerated above. Open questions, like ‘how is this weather likely to impact our flight? Why do you think so?’ by the Commander can draw in the other crew members into giving valuable inputs that should be incorporated in the plan, if feasible. This gives the crew a sense of ownership and would also send a very positive message, which would lead to a very effective team that is motivated to optimum individual, as well as team performance. The Commander has a major role to play in setting the tone, but the crew members also need to live up to the transactional analysis dictum of ‘I am OK, you are OK’. This can only happen if the crew members believe/ are made to believe that they have an important role to play in the safe and efficient conduct of the flight. This can happen if all crew members are encouraged to participate in the communication process, and more importantly are listened to, and treated like trained professionals having a vital role to play during the flight. Operating from the adult ego state would be desirable but depending on the experience of the crew it may need to switch between the adult and the nurturing parent/ natural child ego states too, at times. Crossed and other damaging ego states should be avoided under all circumstances.

High workload situations

The contents of the message change completely in a high work load situation, like during a take-off, landing or during non normal situations. Here words convey 55% of the meaning; the tone of the words spoken another 38%, and body language just the balance 7%. This tells us that it is most important to use standard phraseology with the correct intonation and sense of urgency during these situations. Standard phraseology has the advantage of brevity with accuracy, as both the sender and receiver are on the same page instantly. This however, does not rule out the need to give feedback, read back and hear back, as appropriate. High workload situations are most prone to the use of leading questions, wherein the need for quick answers overrides all else, but these are also the situations when these are most dangerous. Leading questions under such situations are thus best avoided. The analysis of a number of aircraft accidents indicate an increasing number of leading questions leading up to the accident. Leading questions generally are an indicator of a loss of situational awareness. 

Communications on R/T, Intercom or Telephone

In such a situation the content of the message is conveyed 55% through the spoken words and the balance 45% through the intonation, speed and clarity of the spoken words. Standard phraseology is vital in this situation along with feedback, read back and hear back. In case of any disruptions in any of the messages, it is important to retransmit/ seek a clarification instead of assuming, as was the case in the tragic Tenerife accident. Choice of words in verbal communications has significant safety implications. In order to minimise potential ambiguities and other variances in aviation, there are certain standard rules regarding which words, phrases or other elements need to be used for communicating. As an example, ICAO phraseology requires that the word ‘departure’ is used instead of ‘take-off’ in all cases, except for the actual take-off itself. It also requires all clearances, heading, altitudes, runways etc. to be read-back by the crew, as also hear back by the ATC. This was introduced to enhance safety following many cases where messages were misinterpreted/ read back incorrectly.

Written communications

90% of the meaning is conveyed through words or symbols in written communications, with only the balance 10% through the tone of the message. This implies that the choice and use of words and symbols are critical in written communications, like in SOPs, checklists, let down charts, etc. This is even more so in the modern day cockpits with EFIS; the choice of symbols, colours, updating of the databases, etc. become even more critical as there is no dynamic feedback available in the cockpit that can prevent misconceptions/ misrepresentations from leading to an untoward incident. Updation date of the database should be checked before every flight by the crew to ensure that the database is current. The initiator of the written communications should be able to unambiguously create the message in such a way that clearly conveys the intended meaning. It is the responsibility of the crew also to clarify every written communication and get it rectified in case the words and symbols, etc. are perceived differently from what they are intended to convey. Latent errors in written communications are possible and should be eliminated for safe operations.


This form of communication is routinely used in aviation while marshalling an aircraft, and demands that each signal should convey a common understanding to the sender as well as the receiver. Since aviation is an international profession, all the hand signals have been standardised and should be used to prevent chances of misunderstanding. Non standard signals should be avoided.

Accent free English Language for Communications

As discussed above, words are important in almost all forms of communications barring gestures, but even more so on R/T, intercom or telephone and also during high workload situations. The message conveyed is affected by the language employed, the individual accents, pronunciation, vocabulary and grammatical styles. Investigations in to a number of accidents brought home the requirement for a common language for the flight crew in which they should be reasonably proficient to ensure effective communications. ICAO thus recommended through SARPs that language testing should be undertaken to ensure proficiency.  Indian DGCA has implemented this recommendation vide a CAR in Section 7 titled, “English for Aviation Language - Training, Assessment, Test and Certification”.   This CAR lays down the six skill areas in which the crew need to be proficient, and tested. These areas include pronunciation, structure, vocabulary, fluency, comprehension and interactions. Six levels of competency have been identified, and crew have to attain a minimum of Level 4 to operate. The aim of this requirement is to make communications possible, and effective. Crew would still come across individual variations, and should be sensitive to this fact and thus ensure that these variations do not hinder effective communications.

Communications, Workload and Situational Awareness

It is a known fact that human cognitive resources are limited and are shared between current reasoning processes and actions. Communications also consume mental resources. This fact needs to be clearly understood and internalised to ensure that one is sensitive to the workload on the flight deck before initiating/ responding to communications or before interrupting communications already underway, for some other task. We have all experienced situations wherein an increased workload tended to shorten our sentences, as also reduce their numbers, thus increasing the chances of communication errors. The most relevant example is the execution of the ‘Before take-off checklist’. Invariably this gets interrupted by the ATC that is ready to give out the departure clearance. It is best to ask the ATC to standby and complete the checklist before taking down the clearance or take down the clearance and then re-initiate the checklist from the beginning to ensure that both of these crucial tasks are not interrupted, thus making them prone to errors.

Similarly, a person absorbed in a difficult or unfamiliar task like in an emergency situation is less likely to understand what someone is saying to them. It is always best to wait until the task is completed, or stabilised before interrupting them. It is difficult to continue with a demanding task while at the same time communicating effectively. Leading questions at such times can be disastrous, as the person may respond verbally without paying attention, due to lack of mental resources available at his/ her disposal. Please be aware that under conditions of excessive workload, one of the first signs of degraded situational awareness is a loss of the ability to listen in. Since communications consume limited mental resources, to conserve on these, communications should be restricted to task oriented only during the critical phases of flight when sterile cockpit is called for. This ensures that communications are not distracting the crew during periods of anticipated high workload and helps the crew maintain situational awareness.

Thursday, May 23, 2013



The PIC is responsible to ensure that none of the limitations laid down for an aircraft are ever exceeded during any stage of the flight - starting from ramp weight up unti landing weight. There are a large number of people doing the loading; preparing the load and trim sheet; and thus assisting the PIC with this job, but the final responsibility of ensuring that the aircraft is correctly loaded rests with the PIC. The PIC is given a load and trim sheet in which all details are mentioned. He must check that all loading is within the limitations for the operations that he is signing up to undertake, and are as per his/ her latest calculations. These limitations could be related to strength, performance or cg position. In this chapter we would only focus on the how to calculate the amount of payload that can be carried on a particular flight. To get a basic understanding, it is important to read through the following: -

  • Strength limits are easy to understand and are given out in the Certificate of airworthiness/ Flight manual as Max. Ramp Weight, Max Take off Weight, Max Landing Weight and Max Zero Fuel Weight.
  • Performance limitations are based on the environmental conditions in which the aircraft operates and changes at different places and also at the same place at different times of the day and seasons depending on changes in ambient temperature, pressure, runway, winds, precipitation, etc. These could be Climb Limited Weight (CLW), Obstruction Limited Weight (OLW) or Runway Length Limited Weight (RLLW) limitations.
  • CG limits are decided by the manufacturer and are given out in the Certificate of airworthiness/ Flight manual. These should be respected in terms of forward limit and aft limit of CG, during the entire flight spectrum. CG going out of these limits could lead to stability and control problems for the aircraft. An out of limit aft CG can lead to stability problems and an out of limit forward CG to controllability problems. CG changes during the flight due to consumption of fuel, movement of passengers, extension of services, etc. At no stage should the CG be allowed to go outside the stated limits.
Relevant Weights (or Masses)

Basic Empty Weight: The measured or computed weight of an aircraft excluding the weight of all removable equipment and other items of disposable load but including engine coolant, fixed ballast and unusable & trapped fuel and oil. All aircraft weighing more than 2000 kgs are weighed at the time of issue of certificate or airworthiness and thereafter every 5 years as per the regulations (CAR Section 2 - Airworthiness
Series 'X' Part- II dated 14th May, 1993). In addition, if there has been any significant change in empty weight due to repair/ alterations, the aircraft is required to weighed.

Operational Empty Weight: BEW + Cabin Equipment + Crew & their baggage + Potable water and lavatory chemicals.

Dry Operating Weight: OEW + Catering; Newspapers, etc. The load and trim sheet, and thus the Captain starts working from this figure onwards. The rest of the information is to understand the process.

Zero Fuel Weight: DOW + Payload

Landing Weight: ZFW + Fuel Reserves (Alternate, holding and contingency fuel)

Take Off Weight: LW + Trip fuel

Ramp Weight: TOW + Taxy fuel

The table below gives the various figures in tabulated form and the weights are to be added from the bottom row upwards, flowing outwards from the middle column.

Traffic Load: Total mass of passengers, baggage and freight, also called as Payload, as revenue is generated from this load only in commercial aviation.

Useful Load: The total of traffic load and useable fuel.

Max Allowable TOW or Regulated TOW: The MTOW of an aircraft is fixed based on the structural strength. This is fixed by the regulator and does not vary with operating conditions. However, the aircraft cannot always take off at this maximum weight due to performance limitations. Consider the same aircraft operating from different pressure altitudes, say from Delhi and from Leh, or operating from Delhi in summers at 40°C or in winter at 10°C. This is why we have something known as RTOW, that varies with temperature, flap setting, altitude, length of runway and other environmental factors. To ensure that none of the limitations of the aircraft are ever exceeded during flight, it is important to ensure that the take off is always regulated by selecting the lowest of the following weights: -

  • MZFW + Take-off fuel (Trip fuel + Reserves)
  • TOW; Lesser of the Performance limited TOW or Structural MTOW.
  • LW + Trip Fuel; Lesser of the Structural MLW or Performance limited LW.

Steps to find Payload

  • Find the three figures for TOW based on MZFW, TOW, and LW, as given above
  • Take the least of the three as the RTOW for that flight.
  • Subtract the DOW from this to get the Useful Load.
  • Subtract the Fuel Carried from this to get Payload.

Wednesday, May 22, 2013


The dragonfly is the aerial stunt of the insect world. Dragonflies were amongst the first insects to fly, about 300 Ma ago. 290 Ma ago, the dragonflies had a wingspan of 68 cm (2.3 ft). They can fly fast, up to 60 km (37 mi) per hour, which is an amazing feat for an insect, but also slowly, backwards (the hummingbirds are the only other species that can do this) and forwards; they can even copulate in the air while hovering, like the kestrels do. Their wings have a rhythm of 20-30 beats per second. 

A new study published in the Journal of the Royal Society Interface has revealed the secret of the stunts of the  dragonflies: it's all in their ability to move their four wings independently. Most insects use their wings like a single pair. In beetles and bugs, the anterior wings, resembling a crust, are called elytra and they do not beat the air, being just used for protection. Mosquitoes and flies have just one pair of wings (not two), the second having been turned into two organs that detect altitude and 
acceleration, allowing the insect to adapt permanently to the parameters of the flight. Others insects, like butterflies and bees, synchronize the motion of their wings, while special hooks anchor the anterior and posterior wings on one side. 

Dragonflies and damselflies are different: their specific musculature allows them to move each of their four wings independently. Computer modeling has revealed that this type of flapping decreases the amount of generated lift. To verify these computer models, James Usherwood, a biologist at the Royal Veterinary College in London, and Fritz-Olaf Lehmann, a biologist at the University of Ulm in Germany, developed a robot mimicking a dragonfly. 

The robot was soaked in mineral oil containing air bubbles, which permitted to monitor the movement of the liquid around the moving wings. Sensors placed at the base of the robot's wings registered lift and drag forces, and the gathered data allowed to determine the aerodynamic efficiency of the robot.

The robot revealed that flapping four wings actually generated more lift for the same amount of spent energy compared to only two wings. The hind wings, flapping just 25% of a wing beat ahead of the front wings, could catch the rush of air generated by the front wings and generate lift with 22% less energy than in the case of a two-winged system. 

Synchronized flapping too was beneficial: in this case, the robot dragonfly was able to lift off and accelerate better than when using just two wings or four out-of-sync wings. "Engineers may be able to apply these findings to building the next generation of flapping micro air vehicles," said Lehmann.

"Scientists need to validate the findings in living insects. The main difficulty facing the designers of micro air vehicles is that battery life limits how long the devices stay aloft, so any tips or tricks which enhance aerodynamic efficiency will be warmly welcomed," Richard Bomphrey, a biologist at the University of Oxford in the U.K., told ScienceNow.

Monday, May 20, 2013


Brief Details of the Accident

Flight TS 236 took off from Toronto at 0:52 UTC on Friday August 24, 2001 bound for Lisbon. There were 293 passengers and thirteen crew members on board. The aircraft was an Airbus A 330 registered as C-GITS that was manufactured in March 1999, configured with 362 seats and placed in service by Air Transat in April 1999. Leaving the gate in Toronto, the aircraft had 46.9 tonnes of fuel on board, 4.5 tonnes more than required by regulations.

At 05:36 UTC, the pilots received a warning of fuel imbalance. Not knowing at this point that they had a fuel leak, they followed a standard procedure to remedy the imbalance by transferring fuel from the port to the near-empty starboard tank.
At 05:16 UTC, a cockpit warning system chimed and warned of low oil temperature and high oil pressure on engine no. 2. There is no obvious connection between an oil temperature or pressure problem and a fuel leak. Consequently Captain Piché and co-pilot DeJager suspected these were false warnings and shared their observations with their maintenance control centre, who advised them to monitor the situation.
Unknown to the pilots, the aircraft had developed a fuel leak in a fuel line to its starboard engine. The fuel transfer caused fuel from the operational side of the aircraft to be wasted through the leak in the engine on the other side. The leak, which averaged at 1 gallon per second, caused a higher than normal fuel flow through the fuel-oil heat exchanger (FOHE). The FOHE is designed to transfer heat from engine oil to fuel for both cooling and efficiency purposes. The increased fuel flow caused both the drop in oil temperature, as well as the rise in oil pressure that the pilots had observed earlier.

At 05:45 UTC, the pilots decided to divert to Lajes air base in the Azores. The crew were still unsure if they really had a fuel leak or not. They declared a fuel emergency with Santa Maria Oceanic air traffic control three minutes later.
At 06:13 UTC, while still 135 miles (217 km) from Lajes, engine no. 2 on the right wing flamed out because of fuel starvation. Captain Piché ordered full thrust from the remaining operational engine, and the plane descended to 33,000 feet (10,000 m), unable to stay at its 39,000 feet (12,000 m) cruising altitude with only one engine operating. Ten minutes later, the crew sent a Mayday to Santa Maria Oceanic air traffic control.
Thirteen minutes later, engine no. 1 also flamed out at while the aircraft was still approximately 65 nautical miles (120 km) from Lajes Air Base. Without engine power, the aircraft not only lost all thrust, but also its primary source of electrical power. The emergency Ram Air Turbine was deployed automatically to provide essential power for critical sensors and instruments to fly the aircraft. However the aircraft lost its main hydraulic power which operates the flaps, brakes, and spoilers.
Military air traffic controllers who were tracking the aircraft on their radar system guided the aircraft to the airport. While Piché flew the plane, DeJager monitored its descent rate – around 2000 feet (600 metres) per minute – and calculated that the plane had about 15 to 20 minutes left before they had to ditch the plane in the water. The crew sighted the air base a few minutes later. Piché had to execute a series of 360 degree turns to lose speed and altitude. Although they successfully lined up with Runway 33, they faced a new danger. The plane was on a final descent, going faster than optimal. Although they had unlocked the slats and deployed the landing gear, the airspeed was still too high. Additionally, the aircraft would be unable to use its thrust reversers to slow the plane during the landing.
At 06:45 UTC, the plane touched down hard 1,030 feet (310 m) down Runway 33 at a speed of approximately 200 knots (370 km/h), instead of the 170 knots (310 km/h) recommended for an unpowered landing. The aircraft bounced back into the air, but touched down again 2,800 feet (850 m) from the approach end of the runway and came to a stop 7,600 feet (2,300 m) from the approach end of the 10,000 feet (3,000 m) runway. With the operation of the emergency brakes, eight tires burst. Fourteen passengers and two crew members suffered minor injuries during the evacuation of the aircraft. Two passengers suffered serious but not life-threatening injuries.
The favourable outcome was partly attributable to the flight being rerouted at the last minute via a more southerly route across the Atlantic than initially planned, which brought the aircraft within range of the Azores.


The Portuguese GPIAA investigated the incident along with Canadian and French authorities.
The investigation revealed that the cause of the incident was a fuel leak in the number two engine, caused by an incorrect part installed in the hydraulic system by Air Transat maintenance staff. Air Transat maintenance staff had replaced the engine as part of routine maintenance, using a spare engine, lent by Rolls-Royce, from an older model. This engine did not include a hydraulic pump. Despite the lead mechanic's concerns, Air Transat ordered the use of a part from a similar engine, an adaptation that did not maintain adequate clearance between the hydraulic lines and the fuel line. This lack of clearance — on the order of millimeters from the intended part — allowed vibration in the hydraulic lines to degrade the fuel line and cause the leak. Air Transat accepted responsibility for the incident.
Although pilot error was listed as one of the lead causes for the incident, it was the skill of the pilots, and of the military Air Traffic Controller in service at the time, 1st Sgt. José Ramos, that allowed the flight to land without fuel, causing only minor injuries to the passengers and minor damage to the airplane, which is still in service. The pilots returned to a heroes' welcome from the Quebec press.
The incident also led to the issue of Airworthiness instructions to all operators of certain types of the Airbus aircraft that stressed that crews should check that any fuel imbalance is not caused by a fuel leak before opening the cross-feed valve. The French Airworthiness Directive (AD) required all airlines operating these Airbus models to make revisions to the Flight Manual before any further flights were allowed. The FAA gave a 15-day grace period before enforcing the AD. Airbus also modified its computer systems; the on-board computer now checks all fuel levels against the flight plan. It now gives a clear warning if more fuel is being lost than the engines can consume. Rolls Royce also issued a bulletin advising of the incompatibility of the affected engine parts.