Category Archives: Aviation Safety

Any posts about aviation safety.

Herald of Free Enterprise

Ships and Planes and Managers who don’t know!

Have you ever wondered if a pilot in command can learn safety lessons from a ship’s captain? The answer is unreservedly yes because the similarities between the two professions are remarkable. Both are in command. Both are ultimately responsible for the safety of their vessel, their crew, and to their passengers. And strangely enough in many cases they are working for people who are not experts in their profession. One of the requirements of a Safety Management System (SMS) is to define an accountable executive, he who controls the purse strings. How many pilots are working for pilots? For that matter, how many sea captains are working for sea captains? In both cases not many.

The historical lesson we can take from previous accidents in either field, whether in the air or on the sea, cannot be more clearly highlighted than by a study of the Herald of Free Enterprise Disaster. This was a roll-on roll-off ferry that capsized on 6 March 1987 causing the deaths of some 188

persons because it left port with the bow doors open. This was, as are many transportation accidents, a human error accident. The report into this accident (UK Department of Transport MV Herald of Free Enterprise Report of Court No. 8074, MV Herald of Free Enterprise) said, “At first sight the faults which led to this disaster with the aforesaid errors of omission on part of the master, the chief officer, and the assistant boatswain…” (Report paragraph 14.1) As usual, this is not the whole picture. Somewhat controversial for the time, the report’s authors created somewhat of a precedent of adding the cause, “Failure of Management“, to the list of causes. The most damning piece of the report is, “…all concerned in management, from the members of the board of directors down to the junior superintendents, were guilty of fault in that all must be regarded as sharing responsibility for the failure of management. From top to bottom the body corporate was infected with the disease of sloppiness.”


To best illustrate this failure of management the report examined in detail the consideration that had been given, at the request of the sea captains, to fitting an indicator system to show whether the bow doors were open or closed. The captain’s concerns were repeatedly documented and yet rejected for the reasons of costs or even trivial, sarcastic, and frankly incredible statements such as, “do not we pay somebody to close the doors?” Another management failure was the lack of clear orders for the crews and their officers. In short, nobody was actually ordered to close the doors. There was evidence that on many occasions the ships had been overloaded, that they sailed incorrectly ballasted and therefore unstable, and that these shortcomings had been drawn to the attention of management on many occasions by the captains.


So who were these captains working for? The report states, “… those charged with the management of the company’s fleet were not qualified to deal with many nautical matters and were unwilling to listen to their masters, who were well qualified.” Does this sound familiar to many a pilot? How many pilots work for management qualified to deal with aviation matters? Are not many aviation companies run by those with degrees in business, or accountancy, or almost anything except aviation? Surely this must lead to the same frustrations the ferry captains must have felt at the lack of action on serious concerns and other safety issues they had raised with management?


So is there a possible way to solve the issue of specialists working for layman? This whole story of the Herald of Free Enterprise was actually a pivotal point in the history of safety management. The introduction of safety management systems to the transportation industry in particular has many attractive features. Perhaps the most important has already been mentioned; the identification of the accountable executive. This defines, perhaps for the first time, the desk upon which Harry S Truman’s sign, “the Buck Stops Here,” must sit. Part of the measure of a safety culture is the attitudes and commitment of management toward safety; having committed to adopting SMS that attitude is by design subject to change.


So if we are truly to learn from this tragedy management must listen to those who are experts in their appropriate field, react to hazards identified by their experts, and prove that they really are committed to safety by their actions not by their words. Pilots can learn from this too, for they are in the best position to find hazards both in the air and on the ground. They only have themselves to blame if they do not report these hazards.


So has your organization recently adopted SMS? Have you had your Herald of Free Enterprise moment? Have you noticed your management responding more positively to your concerns than before?



Emergency AD: Eurocopter Deutschland GmbH (ECD) Model EC135 P1, EC135 P2, EC135 P2+, EC135 T1, EC135 T2, and EC135 T2+ helicopters

The FAA has issued an emergency Airworthiness Directive (AD) for the EC 135, all variants.

The European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA AD No. 2012-0041-E, dated March 12, 2012 (2012-0041-E), to correct an unsafe condition for the ECD Model EC 135 helicopters. EASA advises that during an inspection of an EC 135 helicopter, a crack was detected on the lower hub- shaft flange of a main rotor hub (MRH) shaft. Since issuing 2012-0041-E, two other lower hub-shaft flange cracks have been reported. ECD is investigating the cause of the cracks and may issue a revised service bulletin with further corrective action. We are issuing this EAD to detect a crack on the hub-shaft flange, which if not corrected could result in failure of the main rotor hub and subsequent loss of control of the helicopter.

Emergency AD#: 2012-10-51

From Reuters

Limitations and Dangers of the use of the English Language in Aviation Communications

Limitations and Dangers of the use of the English Language in Aviation Communications

AVIA 300 Aviation Safety – Week Seven

John Kirk


This paper is an overview of the limitations and dangers of the use of the English language in aviation communications.  Although the internationally agreed language in the air has been English since 1951, there was little research into the safety implications of this policy. Later, after too many examples of accidents where language difficulties were factors, research took place. The major results of that research are examined. Examples of aircraft accidents where language difficulties were a factor are examined. Some examples of regional dialectic differences are highlighted. Finally conclusions and recommendations are listed.


The KLM/ Pan Am disaster at Tenerife airport (Los Rodeos) on March 27th 1977 was the worst accident in aviation history in terms of loss of life. A major contributory factor was the failure in communication using the English language. The KLM aircraft had taken off without take-off clearance, in the absolute conviction that this clearance had been obtained, which was the result of a misunderstanding between the tower and the KLM aircraft.

This misunderstanding had arisen from the mutual use of usual terminology, which gave rise to misinterpretation. In combination with a number of other coinciding circumstances, the premature take-off of the KLM aircraft resulted in a collision with the Pan Am aircraft, because the latter was still on the runway since it had missed the correct intersection.

International Agreement

One of the outcomes based on this and many other accidents and incidents was the introduction of Language Proficiency Requirements (LPR) by the International Civil Aviation Organization (ICAO) in 2004. ICAO grades English language performance on a scale from 6 (highest) to 1 (lowest):

Level 6:


Level 5:


Level 4:


Level 3:


Level 2:


Level 1:


Formal evaluation of language proficiency was required as of March 2008, but ICAO effectively extended the deadline to 5th March 2011. In the USA the Code of Federal Aviation Title 14 (CFR) Part 61 requires that pilots must be able to read, speak, write and understand the English language. This proficiency is recorded on a pilot’s license. The current FAA standards for English language proficiency are laid out in Advisory Circular AC 60-28, English Language Skill Standards reproduced at Appendix 2.

Testing Standards

Whilst the ICAO recommendations determines the standards to be achieved, there is little information available on the reliability and accuracy of testing methods. A survey of aviation English TESTS Alderson, (2010) states, inter alia, “We conclude that we can have little confidence in the meaningfulness, reliability, and validity of several of the aviation language tests currently available for licensure.” (P. 1) This raises considerable concern, as the lack of creditable standards for testing creates a shortfall in the intention in the ICAO document. See Appendix 1 for the standards to which testing should be directed.

Even native English speaking aviators and air traffic controllers must pass knowledge tests which include standard phraseology which must be included in their initial training. In the USA, check airmen are required to certify English proficiency per the Practical Test Standards (FAA). If there is any doubt, a candidate must be referred to an aviation safety inspector (ASI) at the local FAA Flight Standards District Office. In the United Kingdom, a signatory to the Joint Airworthiness Agreement, a similar requirement has been established with the major difference that there are two levels of testing, formal and informal. English Language Schools accredited to the English Council are nominated for formal examination for levels 5 and below, and UK CAA examiners and some others are accepted for level 6.

Specific Example of Dialectic and Foreign Speaking Difficulties

Mention has already been made of the Tenerif accident as perhaps one of the best examples of a non-native English speaker’s difficulty. The phrase “We are now at takeoff,” is the key to understanding the difficulties. In the pilot’s native Dutch, the present progressive tense of a verb is expressed by the word “at” in English plus the infinitive of the verb, “takeoff.” The obvious interpretations of that phrase are:

  1. “We are holding at the takeoff position,” (which is the meaning the Spanish speaking air traffic controller assumed,)
  2. “We are in the act of taking off,” i.e. actually moving.

It is the second meaning that the Dutch pilot assumed the controller understood. The ICAO recommendations address this specifically where level 4 proficiency assumes, “Basic grammatical structures and sentence patters are used creatively and are usually well controlled. Errors may occur, particularly in unusual or unexpected circumstances, but rarely interfere with meaning.” Clearly, a fuller understanding of English grammar, as opposed to word-for-word translation of another native language, is key to success as in this example.

Second Example, voice warning systems

On November 13, 1993, a McDonnell Douglas MD-82 jet crashed in Urumqi, China, while it was approaching to land, killing 12 and injuring 24. Heard on the Cockpit Voice Recorder (CVR) was the last words of the native Chinese speaking pilot who said, “What does ‘Pull-up, pull-up” mean?” It is almost impossible to believe that there should be such lack of knowledge of audio warnings, especially to anyone outside of aviation.

Sources of Errors

The sources of communication error:

  1. Phonology – language sound patterns, prosody, e.g. speech rate, stress, intonation, pauses.
  2. Syntax – language word patterns, sentence structure.
  3. Semantics – language ‘meaning patterns’.
  4. Pragmatics – language in context, situational influences on meaning.

Considering numbers in voice communication conventional wisdom would say that as the digits are particularly standardized there should be little difficulty with regional language barriers. However, that assumption proves to be incorrect. Dr. Bürki-Cohen (Bürki-Cohen, 1995) researched the particulars of how complexity affects pilot recall. ATC normally are required to state digits individually, such as an altitude of 17,000 has to be stated as “one seven thousand.” ATC regulations allow controllers to add grouped digits after the individual digits were stated, i.e. “one seven thousand, seventeen thousand.” It was believed that this would aid retention and accuracy. However the research showed there was little difference with or without grouped digits added. Indeed, analysis showed an advantage of the restated format over the grouped format at higher complexity levels. It is axiomatic that increasingly complex verbal instructions carry a commensurate increase in the risk of misunderstanding.


If it is hoped to reduce the human factors accident rate more attention needs to be paid to language. The higher standard to which the international aviation community should aspire must constantly strive to ensure that the recommendations of ICAO in the area of English Language Proficiency should be achieved.


The following recommendations are suggested:

  1. Establish accredited schools for teaching English to all in aviation,
  2. Set clearer standards for testing and awarding all levels of proficiency,
  3. Research current “standard” phraseology, particularly differences between native English speaking nations, to harmonize those standards, reduce or eliminate ambiguity – particularly where cultural influences effect the use of language,
  4. Study pronunciation, and publish standard pronunciation for those words which exist in standard phraseology.


AC 60-28 CHG 1 Appendix 1


The following English language proficiency standards* must be met by the applicant and evaluated by the designated examiner or aviation safety inspector (ASI) when determining if the applicant meets the English language eligibility requirements of 14 CFR parts 61 and 63:

1.            PRONUNCIATION. Assumes that English is not the applicant’s first language and that the applicant has a dialect or accent that is intelligible to the aeronautical community. Pronunciation, stress, rhythm, and intonation are influenced by the applicant’s first language, but only sometimes interfere with ease of understanding.

2.            STRUCTURE. Relevant grammatical structures and sentence patterns are determined by language functions appropriate to the task. Basic grammatical structures and sentence patterns are used creatively and are usually well controlled by the applicant. Errors may occur, particularly in unusual or unexpected circumstances, but rarely interfere with meaning.

3.            VOCABULARY. The applicant’s vocabulary range and accuracy are usually sufficient to communicate effectively on common, concrete, and work-related topics. The applicant can often paraphrase successfully when lacking vocabulary in unusual or unexpected circumstances.

4.            FLUENCY. The applicant produces stretches of language at an appropriate tempo. There may be occasional loss of fluency on transition from rehearsed or formulaic speech to spontaneous interaction, but this does not prevent effective communication. The applicant can make limited use of discourse markers or connectors. Fillers are not distracting.

5.            COMPREHENSION. Comprehension by the applicant is mostly accurate on common, concrete, and work-related topics when the dialect, accent, or variety used is sufficiently intelligible. When the applicant is confronted with a linguistic or situational complication or an unexpected turn of events, comprehension may be slower or require clarification strategies.

6.            INTERACTIONS. Responses by the applicant are usually immediate, appropriate, and informative. The applicant initiates and maintains exchanges even when dealing with an unexpected turn of events. The applicant deals adequately with apparent misunderstandings by checking, confirming, or clarifying.

* Level 4 Rating Scale adopted from the ICAO Language Proficiency Rating Scale found in ICAO Document 9835 and the attachment in ICAO Annex 1.


Manual on the Implementation of the ICAO Language Proficiency Requirements – Doc 9835-AN/453

World Englishes, Vol. 23, No. 3, pp. 451–470, 2004. 0883–2919 Fatal miscommunication: English in aviation safety ATSUSHI TAJIMA

The challenge of regional accents for aviation English language proficiency standards: A study of difficulties in understanding in air traffic control–pilot communications. T. Tiewtrakul and S.R. Fletcher Ergonomics Vol. 53, No. 2, February 2010, 229–239

A survey of aviation English tests J. Charles Alderson, Language Testing 27(1) 51–72 2010 DOI: 10.1177/0265532209347196

An Analysis of Tower (Ground) Controller-Pilot Voice Communications. Final Report No. DOT-VNTSC-FAA-95-41

Bürki-Cohen, J. (1995). Say Again? How Complexity and Format of Air Traffic Control Instructions Affect Pilot Recall. In 40th Annual Air Traffic Control Association Proceedings, September 1995, 225-229.

Bürki-Cohen, J. (2003). Evidence for the Need of Realistic Radio Communications for Airline Pilot Simulator Training and Evaluation. In Proceedings of the International Conference Simulation of the Environment, Royal Aeronautical Society, 5-6 November, London, UK.

AC 60-28, English Language Skill Standards

Crew Resource Management            Date: 1/22/04            AC No: 120-51E TRAINING$FILE/AC120-51e.pdf



Do Pilots join associations? HAI, NEMSPA, AOPA


Here’s a question for all pilots, do you join associations, societies, or any aviation communities? A gut feeling tells me the answer is no! We live and work in a tiny little office, otherwise called a cockpit, for good reasons. There’s many a pilot who has said, either out loud or to himself, “I’m glad to get airborne to get away from the BS on the ground!”

“So what?”, I hear you cry. Well, there are some advantages to joining those organizations who represent us. Three in particular spring to mind, in no particular order:

Helicopter Association International

The first meeting of the founding members of this group took place on December 13th 1948. Yes, younger readers, there were helicopters way back then. Going through several name changes, the mission of the HAI has remained largely the same over more than 60 years. Their mission statement; “To provide its members with services that directly benefit their operations, and to advance the international helicopter community by providing programs that enhance safety, encourage professionalism and economic viability while promoting the unique contributions vertical flight offers society.”

You may join the HAI by clicking here.

National EMS Pilots Association

Whilst HAI serves the entire helicopter community world-wide, NEMSAP represents the EMS pilot in the USA. Much more specific and focused on issues that effect the American EMS pilot’s life. From personal experience, I know that NEMSPA has been very influential with those people who regulate us! It is clear that their efforts have prevented overbearing regulation, have created an influential voice for us all at Washington, DC, and are actively pursuing leading-edge research into issues that effect us all. Their mission statement; “We, the National EMS Pilots Association, will strive to help the Air Medical industry prosper safely and enhance the delivery of pre-hospital health care. We will provide the leadership necessary to establish standards of operational safety and a forum for the dissemination of knowledge. This organization will continue to be a major advocate for positive change for our industry.”

You may join by clicking here.

Aircraft Owners and Pilots Association

Incorporated on May 15th 1939, AOPA represents over 400,000 members. Their advocacy and campaigning efforts with the nation’s lawmakers and regulators have helped to prevent aviation hostile political people from closing us down, closing our airports, and from unfairly taxing us out of existence. The contribute greatly to aviation safety through their Air Safety Foundation, and rely on general aviation’s support through their Foundation.

AOPA’s mission statement; “We preserve the freedom to fly by…

advocating on behalf of our members,
educating pilots, nonpilots, and policy makers alike,
supporting activities that ensure the long-term health of General Aviation,
fighting to keep General Aviation accessible to all, and
securing sufficient resources to ensure our success.”

AOPA’s vision statement; “AOPA is the beacon for those who cherish the freedom to fly. It demonstrates what is possible when a determined organization listens to its members, collaborates with its colleagues, finds solutions with its partners in government, and focuses its resources—all to secure the future of General Aviation. AOPA’s success is proof that the public good can be served while individual freedoms are preserved.”

You may join by clicking here.

NEMSPA Pilots Survey of America’s Heliports

NEMSPA Pilots Survey of America’s Heliports
Now Available for Review and Download

NEMSPA has completed the intiial analysis of the data gathered from a survey of helicopter pilots nationwide. The survey garnered over 1300 responses from helicopter pilots with opinions and suggestions regarding the design and the safety of the heliport facilities that they typically use in their daily flying duties. The detailed results of the survey can be accessed by Clicking Here

Helicopter makes emergency landing in Palo Alto – AP State Wire News – The Sacramento Bee

If ever you’ve been involved in an emergency, be aware that within minutes you can expect a large number of reports. Check out this Google Search for the 40 news stories about this Robinson R22 forced landing.

Helicopter makes emergency landing in Palo Alto – AP State Wire News – The Sacramento Bee.


Helicopter pilot misjudged altitude: report

Helicopter pilot misjudged altitude: report.

Southwest Airlines Flight 1248 landing accident

Liberty U – AVIA 305 Week 6 Essay

Southwest Airlines Flight 1248 landing accident (NTSB/AAB-06/03).


This essay will examine landing accident to Southwest Airlines Flight 1248 at Chicago O’Hare airport on December 8th 2005. A search of the NTSB accident/incident database reveals ten runway overrun accidents or incidents since 1982. The NTSB accident report highlights major systemic failures, which will be highlighted below.

Determination of Cause

The National Transportation Safety Board determined that the probable cause of this accident was the pilots’ failure to use available reverse thrust in a timely manner to safely slow or stop the airplane after landing, which resulted in a runway overrun. This failure occurred because the pilots’ first experience and lack of familiarity with the airplane’s autobrake system distracted them from thrust reverser usage during the challenging landing.

Contributory Causal Factors

The factors that contributed to the accident or contributed to the severity of the accident are:

  1. Failure to provide its pilots with clear and consistent guidance and training regarding company policies and procedures related to arrival landing distance calculations;
  2. Programming and design of an on board performance computer, which did not present inherent assumptions in the program critical to pilot decision-making;
  3. Plan to implement new autobrake procedures without a familiarization period;
  4. Failure to include a margin of safety in the arrival assessment to account for operational uncertainties;
  5. Pilots’ failure to divert to another airport given reports that included poor braking action and a tailwind component greater than 5 knots;
  6. Contributing to the severity of the accident was the absence of an engineering materials arresting system, which was needed because of the limited runway safety area beyond the departure end of runway 31C.

Pre-landing planning

Under regulation in force at the time of the accident, air carriers were required to provide landing performance calculations prior to departure to ensure adequate landing distance considering aircraft weight, forecast weather and runway conditions, and the expected fuel burn en route. Less than half of the airlines required an arrival landing distance assessment using current data. However, Southwest required their pilots to perform an arrival assessment. The pilots carried out such an assessment using an onboard personal computer with data and algorithms provided by a third party vendor.

However, critical assumptions, specifically the tailwind component of 8 knots, was not used by the computer, inserting the 5 knot tailwind limit imposed in the Flight Operations Manual (FOM). In addition the FOM required pilots to use the worse of mixed runway conditions, as in this case… fair/poor.

Taking all the above critical data into account the pilots were required to divert to an alternate and failed to do so. It must be noted that five similar airliners, some Southwest Airlines operated, had landed safely prior to the accident aircraft.

Conduct of the landing.

Neither pilot had used autobrake, although they had completed ground training. They discussed the autobrake during the approach briefing phase of flight, and clearly were aware of its use. However, after a seemingly normal if fast approach due to the 8-knot tailwind, and after a firm touchdown, the flying pilot failed to engage reverse thrust being concerned with the performance of the brakes. He elected to use manual braking and applied full brake pressure. It was some 15 seconds after touchdown that the monitoring pilot noticed the lack of reverse thrust, and he removed the captain’s hand from the engine levers and selected full reverse thrust. Both full reverse thrust and full wheel braking were applied from then on.

Using all available data, and analyzing the flight data recorder, manufacturer’s landing data, and the reported runway conditions worst case of poor, it is true that a safe landing could have been performed.


This was an avoidable accident.

Poor regulation, poor operational procedures, poor training, inadequate computer display of critical information, confusion amongst pilots as to the significance of landing performance calculations, ignorance of published company procedures, and introduction of autobrake without familiarization all contributed to this accident. Had any one of those factors been correct at the time of this accident, it is entirely possible that one of the links in the chain of events could bave been broken, thus preventing such a tragedy.


NTSB Animation Runway Overrun of Southwest Airlines Flight 1248 at Chicago Midway

Accident Involving Air Tahoma, Inc., Flight 185 N586P August 13, 2004 (Not helicopter, but safety relevant)

Accident Involving Air Tahoma, Inc., Flight 185 N586P August 13, 2004

John Kirk

Liberty University

This paper will examine the accident involving Air Tahoma Flight 185 at Covington, Kentucky. The area of examination will discuss the human factors involved in the pilot’s actions, the maintenance actions, the airliner’s training, and the design flaws highlighted in this accident. As with any aviation accident, there is a chain of events which led to the occurrence; each link in the chain will be highlighted.

Breaking the sequence down into constituent parts allows an understanding of all the factors involved. The paper will go beyond the simple statement of causes as determined by the National Transportation Safety Board (NTSB) and will cover topics of accident prevention that apply to the entire safety culture.

Keywords: aircraft, accident, fuel system mismanagement, design flaw, Convair 580

 Accident Involving Air Tahoma, Inc., Flight 185 N586P August 13, 2004


Every aircraft accident is characterized by a chain of events, breaking any one of the links in the chain the accident would have been prevented. Reviewing the NTSB aircraft accident report (AAR 0603 – hereinafter referred to as “the Report”) shows that this accident matched the above generalization. In reviewing such accidents going beyond the simple statement of “pilot error”, the obvious question is why did the pilot do what he did. This is the essence of human factors theory and practice.

This accident was not the first fuel starvation forced landing accident. On 30 December 1964 a Convair 340, operated by United airlines, registration N73102, landed wheels up after the flameout of both engines. It has proved impossible to acquire the accident report from archives this old. It is disappointing that the lessons learned from this previous accident were not applied thereby preventing the subsequent accident near Cincinnati.

It will be useful to define what is meant by fuel cross feed and what is meant by the fuel transfer. Fuel cross feed is only intended to correct an imbalance between two tanks or two groups of tanks. In many installations this is achieved simply by opening a cross feed valve and switching off the fuel boost pump in the tank with the higher fuel contents. The remaining fuel boost pump feeds both engines and the pilot is required to observe the fuel quantity restoring normal operation when the fuel is balanced. Fuel transfer, on the other hand, is often achieved by a failsafe-protected system whereby a separate transfer pump allows fuel to be pumped from one tank to another. Because fuel transfer would be possible, in theory, to completely empty a tank there are limit switches that prevent over fueling of one group of tanks. Fuel transfer systems are rarely fitted to normal passenger or freight aircraft, and are usually only found on larger more complex aircraft such as military fuel tankers, or fitted to aircraft, such as the Concorde, which require center of gravity fuel transfer for supersonic flight.

On August 13, 2004, about 0049 Eastern daylight time, Tahoma, Inc., Flight 185, a Convair 580, N586P, crashed about 1 mile south of Cincinnati Northern Kentucky International airport (CVG), Covington, Kentucky, while on approach to runway 36R. The first officer was killed, and the captain received minor injuries. The airplane was destroyed by impact forces. The flight was operating under the provisions of 14 Code Of Federal Regulations part 121 as a cargo flight for DHL Express from Memphis International airport, Memphis, Tennessee, to CVG. The National Transportation Safety Board (NTSB) determined that the probable cause of this accident was fuel starvation resulting from the captain’s decision not to follow approved fuel cross-feed procedures.

Contributing to the accident where the captains inadequate pre-flight planning, his subsequent distraction during the flight, and his late initiation of the In-range checklist. Further contributing to the accident was the flight crew’s failure to monitor the fuel gauges and to recognize that the airplane’s changing handling characteristics were caused by a fuel imbalance.


This paper will be divided into the following sections:

  1. Bad Design
  2. Bad Certification
  3. Bad Modification
  4. Bad Maintenance
  5. Bad Regulation
  6. Bad CRM

Bad Design

To an outside observer the design of a fuel system that is capable of causing structural damage or of venting half the contents of the of the fuel system overboard cannot be safe. In addition, what is often referred to as tribal knowledge seems to have taken part in this accident.

The aircraft manufacturers approved flight manual says:

  1. “place boost pump switch for tank being used to the on the position and place the cross feed switch to the on position,
  2. place the boost pump switch for the tank not being used to the off position, and
  3. place the fuel shutoff valve switch for the tank not to being used to the closed position.”

Air Tahoma fuel cross feed procedures states:

To cross freed from either tank to opposite engine;

  1. both fuel boost pumps ON,
  2. both aircraft fuel boost pressure lights OFF,
  3. cross feed valve OPEN,
  4. fuel boost pump for tank not to be used OFF.
  5. Tank shutoff valve for tank not used OFF

Evidence was presented that pilots in general do not trust a fuel shutoff valve quoting valve failure as a reason for not using it. How this myth became so prevalent is perhaps based on the fact that the fuel shutoff valve and the fuel cross feed valve are both motor operated valves, which remain in their last position if power is lost. (Figure 1.) Therefore closing the fuel shutoff valve before an unexpected electrical power failure will mean the loss of half of the aircraft available fuel. Little wonder that pilots did not trust the fuel shutoff valve, and that one operator, the pilot’s previous employer, even stated in their checklist, “fuel shutoff valve close at pilots discretion.” Many fuel systems do not have a shut-off valve such as in this installation. A lack of a failsafe fuel valve must be considered a design flaw.

The report states that a one-way check valve was not fitted into this fuel system. “One-way check valves are not typically installed on airplanes, and the accident airplane did not have one installed. According to a Kelowna Flightcraft representative, one Convair 580 operator modified its fleet of about 30 Convair 580 airplanes in the 1960s under an engineering order by installing a one-way check valve, which prevented fuel from flowing back into the fuel tanks when the fuel tank shutoff valve was left open. However, the representative stated that this operator was no longer in business and that its airplanes had represented a small percentage of the entire Convair 580 fleet.”

It is clear that at least one operator considered this design flaw merited the fitting of a one-way check valve to prevent inadvertent transfer of fuel. In addition they retro-fitted warning lights to show the status of the cross feed valves and the shut off valves.

The position of the fuel gauges is also an example of bad design, bad ergonomics. With a seat in the aft position, often where non-flying pilots sit, meant that it was not easy at all for the captain to view the fuel gauges. (Figure 3.)

Bad Certification

The design flaw and lack of failsafe having been certified by the FAA must, by definition, be a failure in that certification process. To simply accept an aircraft as airworthy by accepting procedures to cope with a non-safe installation is simply not good enough. Had the certification personnel checked with global regulatory bodies, they would have found widespread requirements to fit one way check valves to fuel systems.

Bad Modification

PJCB 10-21, “Aircraft Fuel Boost Pump Output Pressure Limit-Reduce,” which was published in October 1969, provided details on an optional procedure that allowed Convair 580 operators to reduce the typical fuel boost pump output pressure setting of 21 psi to 15 psi to “improve the service life of the aircraft fuel boost pump.”  This cost saving measure has now been shown to have introduced an unintended consequence, that differential fuel boost pump output pressure settings would guarantee that fuel would transfer from one tank to the other should the cross feed valves be left open. The service bulletin contained a recommendation that aircraft should preferably be operated with identical boost pump pressure; there was no requirement for this to be done.

Another incident of inadvertent fuel transfer had occurred to this operator on September 21, 2004. No evidence was given as to what modification state the incident aircraft had, other than  post-incident bench testing showing a differential pressure of 15 and 21 psi between the two pumps.

Bad Maintenance

Air Tahoma maintenance personnel reported that they were not aware of the service bulletin to lower the fuel boost pump output pressure setting to 15 PSI. In June 2004, maintenance and replaced the left fuel boost pump on the excellent airplane with a pump that have them output pressure setting of 21 PSI. However, they did not replace the right fuel boost pump and did not measure or alter the output pressure setting. As a result, they were unaware that it was operating the airplane with left and right differential fuel boost pump output pressure settings.

Maintenance procedures did not include a reference to the service bulletin, and only required setting of the fuel boost pump pressure to 21 PSI, as opposed to the lower service bulletin setting of 15 PSI.

Only 4 months before the accident, there had been the in-flight fuel imbalance incident to Nolinor Aviation. Maintenance personnel had changed a pump inadvertently introducing differential fuel pressure and had left the cross feed valve open. Other than switch position there is no cockpit indication that a cross feed valve is open.

The NTSB recommendations included the requirement for operators to set the left and right fuel boost pump pressure to the same setting. This recommendation clearly addressed the issues of poor maintenance.

Bad Regulation

It is the duty of the regulatory body, the Federal Aviation Administration (FAA) to regulate and thereby ensure safety of flight. In particular, Principle Operations Inspectors are required carry out specific functions including approval or acceptance of a certificate holder’s operating procedures. Experience has shown that there is a lack of standardization across an otherwise well motivated and experienced pool of such inspectors. Company checklists which include the words “at the captain’s discretion” having been approved or accepted by one inspector caused this particular pilot to ignore a critical step on his checklist. Whilst these approvals are well intended, the unintended consequences in this example show that improvements to the methods and procedures used by the FAA require critical examination.

In addition, the FAA is required to certify airmen. That is to say conduct check rides issuing qualifications for types or ratings. In the report evidence was given that this pilot had reduced training, presumably due to his previous qualification on type, and a check airman signed this pilot’s type qualification for his new employer. The check airman is either employed by or appointed by the FAA, therefore responsibility must be partly apportioned to poor regulation.


The FAA defines Crew Resource Management (CRM) as, “The effective use of all resources to include human and other aviation system resources”. The history of accident prevention includes a time when training was primarily limited to the skills of flying and the technical knowledge in aircraft systems that were required to operate an aircraft. Realization that human factors were the main cause of accidents led to the development of CRM over several decades. This was because research looked beyond “what the pilot did” to understand “why the pilot did it”. (Salas p. 565)

This accident is typical and includes many of the elements that CRM attempts to address. The “insidious enemies” of erroneous “facts”, incorrect assumptions, miscommunications, misunderstandings and the individually generated disconnect between “situational awareness” and “truth” all play a part here. (Salas p.564) Examining each of these elements in relation to the accident will, no doubt, give a clue as to the real causes.

Erroneous Facts

The pilot believed that the fuel shut off valve was unreliable. It has already been speculated that this may have been simply because the valve was not fail-safe. It is also speculated that as a fraternity, the pilot population would in general be uncomfortable shutting off fuel supplies on an aircraft in flight. Whilst understandable it is, on the face of a lack of evidence of fuel shut off valve failures, one of those erroneous facts that pervades aviation. Any number of commonly held beliefs based on no real scientific evidence has led to many an error. Perhaps aircraft designers need to consider these “urban myths” when designing aircraft systems.

Incorrect Assumptions

The pilot assumed that opening the cross feed valve and doing nothing else would have no consequence. As any pilot about a cross feed system and they would probably agree with this assumption. If both fuel pumps are running it is assumed that opening the cross feed valve will have no effect. Having no indication of fuel supply pressure downstream of the fuel pumps other than a pressure switch set to operate at a pressure determined by either the high or low setting, neither this pilot nor any pilot on this type of aircraft would have any reason not to make this assumption. It is clear that the setting of differential pressures on the two pumps made this assumption wrong.

In addition, there was evidence that the pilot believed there was a one way check valve in the system preventing the undesirable fuel transfer. One operator had fitted these check valves. Other aircraft have them as standard equipment. Therefore through incomplete or inadequate training on the systems this pilot was led to failure through his hazy notion that transfer was not possible, despite the warnings in the flight manual and on the placard in the aircraft.


This pilot was distracted throughout the flight. His concerns with an error on his weight and balance calculations led him to forgetting that he had started a fuel balance procedure. On six occasions the first officer complained about the handling of the aircraft. Post accident actions included the reminder that under the principles of CRM a crew member has a duty to be more assertive in expressing concerns. To be fair to the captain, the first officer’s words were ambiguous at best if not misleading at worst. The only reply from the captain was to have the controls checked on landing. There were clues which are obvious in hindsight given by the first officer, but not expressed in a way that would have reminded the captain of what was likely to be the cause of the control difficulties.

Disconnect between Situational Awareness and Reality

Given the erroneous facts above and the resultant incorrect assumptions it is clear that the captain was not aware of the realities of the situation. It is true that once a person has formulated a certain way of thinking about a problem, it appears difficult to get out of that way of thinking and try a different interpretation of the data. (Green P.61) This “confirmation bias” was clear in this instance. For all the reasons above the pilot could not make a new determination of the cause of the control difficulties reported by the first officer.

The biggest single failure on the part of this captain was not to have been more pro-active in responding to his first officer’s concerns. He did not, for example, ask any questions to clarify the information, nor did he take control of the aircraft to see for himself. This has to be the most surprising aspect of this accident. Given the timing of events, it is uncertain whether he would have concluded correctly that he had a fuel imbalance, but he should have done more to identify the problem.


This was a preventable accident. There are CRM lessons for all operators here, not only for pilots, but for maintenance, management, regulation and supervision. To misquote an old adage, “To err is human, to make the same mistake twice is unforgivable, to make the same mistake three times is unbelieveable”.

Air Safety Net Convair 580 hull write off database. Retrieved 29 February, 2012 from: http://av.

Convair 580 Aircraft Data Retrieved 29 February, 2012 from:

Green R.G, Muir H., James M., Gradwell, D., Green R.L, Human Factors for Pilots (2nd ed.) (1996) Aldershot: Avebury Aviation

NTSB Aircraft Accident Report NTSB/AAR-06/03  PB2006-910403 Notation 7778 Retrieved  29 February, 2012, from:

NTSB Brief Incident Report, CONVAIR CV-340, registration: N73102 Retrieved 29 February, 2012 from:

Salas E., Maurino D., Curtis M., Human Factors in Aviation (2nd ed.) (2010) Burlington: Elsevier

Seamster T. L., Boehm-Davis D. A., Holt R. W., Schultz K. Developing Advanced Crew Resource Management (ACRM) Training: A Training Manual 1998 Federal Aviation Administration Retrieved 29 February, 2012, from: