Problem stated in slot #105:
"... I don't really undertand why some of these overrun accidents keep happening...."
Excerpts from
“Pressing the Approach”
A NASA study of 19 recent accidents yields a new perspective on pilot error.
By Benjamin A. Bermin and R. Key Dismukes,
Aviation Safety World December 2006 | Flight Safety Foundation
Pressing the Approach 6 pages. [PDF 297K]
_Aviation Safety World_, December 2006, pgs 28-33
Some interesting concepts here, subtly
implicated in “unstable” approaches, eg:
-- Plan Continuation Bias,
-- late cognitive demands may overwhelm the human’s capabilities, and then inhibit his decision for go-around;
-- mixed messages from the airline (merely suggesting guidelines rather than imposing standards).
The cognitive-limitations described in this FSF paper (from Bermin and Dismukes) suggest the earliest activation of Honeywell’s hosted
RAAS [Rwy Awareness Advisory System] and
SAM [Stabilized Approach Monitor].
[A special thanks to FSF’s K. Ehrlich, Production Coordinator, Flight Safety Foundation, for her sending the un-locked pdf file. That protection-free file made these excerpts easily available for you to read below.]
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“...
two of the most common themes in the 19 accidents studied: *** plan continuation bias — a deep-rooted tendency of individuals to continue their original plan of action even when changing circumstances require a new plan — and
*** snowballing workload — workload that builds on itself and increases at an accelerating rate....
“...
the problems encountered by the crews seem to have centered on these two themes....
“Too often, pressing an approach ... is attributed to complacency or an intentional deviation from standards .... To understand why experienced pilots sometimes continue ill-advised approaches, we must examine the insidious nature of plan continuation bias. Plan continuation bias appears to underlie what pilots call “press-on-itis,” which a Flight Safety Foundation task force found to be involved in 42 percent of accidents and incidents they reviewed.Similarly, this bias was apparent in at least nine of the 19 accidents in our study. Our analysis suggests that this bias results from the interaction of three major components: -- social/organizational influences,
-- the inherent characteristics and limitations of human cognition, and
-- incomplete or ambiguous information....
“...
Our study suggests that ... -- when standard operating procedures are phrased not as requirements ... that may appear to tacitly approve of bending the rules,
-- pilots may ... place too much importance on schedule and cost when making safety/ schedule/ cost tradeoffs.
“Also, pilots may not fully understand ... that the cognitive demands ... from an unstabilized approach severely impair their ability to assess ... the approach ...”
“...
Although plan continuation bias is powerful, it can be countered once acknowledged. One countermeasure is to analyze situations more explicitly than is common among crews. This would include explicitly stating the nature of the threat, the observable indications of the threat and the initial plan for dealing with the threat. Crews then should explicitly ask, “What if our assumptions are wrong? How will we know? Will we know in time?” These questions are the basis for forming realistic backup plans and implementing them in time, but they must be asked before snowballing workload limits the pilots’ ability to think ahead.
“ Airlines should periodically review normal and non-normal procedures and checklists for design features that invite errors....
“... Operators should carefully examine whether they are unintentionally giving pilots mixed messages about competing goals such as stabilized approaches versus on-time performance and fuel costs. For example, if a company is serious about compliance with stabilized approach criteria, it should publish, train and check those criteria as hard-and-fast rules rather than as guidelines....”
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