United Airlines Suffers from ED (Error Dysfunction)

We have previously discussed a long running series of around 40 events when Fan Cowl Doors (FCD) were lost from Airbus A320 series aircraft, including:

In each case the cowls had inadvertently been left unlatched and this had not been subsequently detected before flight.

Damage to Tigerair Airbus A320-200 9V-TRH (Credit: TSIB)

Damage to Tigerair Airbus A320-200 9V-TRH (Credit: TSIB)

Airbus introduced a modification that would prevent the cowls being opened without inserting a mechanical ‘key’ attached to a long red streamer, that would normally be stowed on the flight deck and that could only be removed when the cowls were fully locked.

But remarkably a US airline fought the proposed Airworthiness Directive (AD).

United Airlines Responses to FAA NPRM

The airline responded as follows for the FAA Notice of Proposed Rulemaking (NPRM) to adopt the exiting EASA AD (AD 2016-0053 on IAE V2500 powered A320s had been issued in March 2016 and was followed by AD 2016-0257 on CFMI CFM56 powered A320s):

United Airlines (UAL) stated that it strongly disagrees with making the new latch keys installation mandatory. UAL stated that each one of the fan cowl door losses during takeoff can be attributed solely to human error.

The implication is that no design improvement is needed after 40 occurrences.

UAL explained that the mechanics are not correctly latching the fan cowl after maintenance and the flight crews are not checking that the latches are secured before departure.

A320 Fan Cowl Doors (Credit: via ANSV)

A320 Fan Cowl Doors (Credit: via ANSV)

This is undoubtedly true, but in a surprisingly they go on to say:

…instead of mandating the modification, UAL stated that more emphasis should be placed on addressing the root cause—not the design, but human error.

James Reason, Professor Emeritus, University of Manchester wrote in his classic 1997 classic Managing the Risks of Organizational Accidents that among some of the problems with error management are:

  • Focusing on the active failures (of people) not the latent conditions
  • Not being informed by current human factors thinking regarding error and accident causation

Human error is not itself a cause, but merely the start of a human factors investigation, as explained by Sidney Dekker in The Field Guide to Understanding Human Error – A Review (discussed in this book review The Field Guide to Understanding Human Error to the RAeS).

United are disappointingly focusing on what Reason called ‘the human condition’ and hoping to change it, something he argued was futile, but that “we can change the conditions under which people work“.

Perhaps United have never heard of the Murphy’s Law from the 1940s either.

United went on to complain that:

…adding another loose piece of equipment to be maintained and stored on the airplane would lead to operational complications.

That is true but in the scheme of operation of a modern airliner it is neither a disproportionate or novel complication.  According to the FAA:

UAL also noted that additional time would be added to accomplishing routine tasks after incorporation of the modification.

UAL contended that additional time would be required to access the cockpit, retrieve the key, and open the fan cowls, which would expose personnel and the airplane to further damage or harm.

They don’t specify what further damage / harm this could involve as non of these tasks are again unique.  More telling:

Mandating the modification, UAL argued, would impose an unnecessary financial and maintenance burden on operators that have proactively implemented alternate procedures.

The alternative being an independent inspection, which of course involves additional maintenance personnel, a cost and complexity that they don’t feel worthy of mentioning.

Its not clear what risk assessment was conducted under United’s Part 5 SMS or what human factors assessment methodology was used as no such assessment was submitted to the FAA, nor was any other data driven substantiation for their claims, according to the FAA.

FAA Conclusions

From these statements, we infer that UAL was requesting that we withdraw the NPRM.  We do not agree with UAL’s request.

EASA, as the State of Design Authority for Airbus products, has determined an unsafe condition exists after conducting a risk analysis taking into consideration the in-service events in the worldwide fleet. We agree with EASA’s decision to mitigate the risk by mandating a new design that makes it apparent to the flight crew on a pre-flight walk-around that an FCD is not latched.

Regarding the concern about operational complications, we have determined that the safety benefits of the new design outweigh any potential complications.

We reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously and minor editorial changes.

We have determined that these changes:
- Are consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and
- Do not add any additional burden upon the public than was already proposed in the NPRM.

Our Observations

The value of human centred design (HCD) is preventing the ability to release an aircraft in an undesired or unsafe condition.  As we have commented previously:

…controls that are entirely training and procedural will one day fail and the most effective way to control a hazard that can be triggered by a human error is to eliminate the potential for error whenever possible.  This may be using mistake-proofing features which the Japanese call ‘poke’-yoke’ (like the new key), or by changing how a task is accomplished…

A poorly argued, data free response that only focuses on the negatives of a mitigation to a frequently repeating event (especially when the negatives are relatively small negatives), that fails to consider contemporary thinking on human factors does not reflect well on an organisation’s approach to safety, and smacks of complacency.

See also:


Aerossurance will be presenting at EASA‘s 11th Rotorcraft Symposium on Cologne on 5 December 2017 on human centred design (HCD) for rotorcraft.  This presentation will be live streamed.

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Aerossurance has extensive air safety, operations, airworthiness, human factors, aviation regulation and safety analysis experience.  For practical aviation advice you can trust, contact us at: enquiries@aerossurance.com