Safety of flight

Larger and more complex aircraft usually use hydraulics for most mechanical systems, including flight controls, landing gear, brakes and others. Many of these systems are critical to the safety of flight and the quality of the hydraulic fluid is vital. 

A sector is a portion of the air space controlled hy an air traffic controller. The main ohjective of the air traffic controller is to warrant the safety of flight while the aircraft are inside his sector (Air Safety Group 2003). 

Chapter 6 of the CAIB report, titled Decision Making at NASA, focuses on the decisions that led to the STS-107 accident. Section 6.1 reveals that the shedding of foam from the external tank - the physical cause of the Columbia accident - had a long history. It illustrates how foam debris losses that violated design requirements came to be defined by NASA management as an acceptable aspect of shuttle missions - a maintenance turnaround problem rather than a safety of flight concern. Table Al, adapted from figure 6.1-7 of the CAIB report, provides the histoiy of foam debris losses up to the Columbia disaster. 

STS-35 December 2, 1990 First time NASA calls foam debris a safety of flight issue, and a re-use or turnaround issue. ... 

The analysis is, and will remain, preliminaiy. A more systematic analysis of the vocabulaiy would require a more comprehensive examination of a more complete corpus of written documents, memos, and emails. One of the difficulties of a retrospective analysis is that of sampling on the dependent variable. Using internet search engines, I searched for documents containing key terms in NASA s vocabulaiy, including safety of flight and acceptable risks, i also searched for documents on foam debris, tiles, and reinforced carbon carbon (RCC), paying particular attention to documents produced prior to the Columbia disaster. 

Finding 5. Post-Challenger, the term safety of flight became an institutionalized expression within NASA s organizational culture, but this expression was subject... 

Finding 8. NASA s focus on safety of flight criteria in its vocabulary allowed NASA s managers and engineers to perceive the post-Challenger culture as a safety culture, despite the inherent risks in the space shuttle technology. 

In developing their interpretation of the Columbia accident and its root causes, the CAIB board members singled out the expression not a safety of flight issue, and how it affected key decisions made by the shuttle program ... 

Finding 9. Based on a combination of flight experience and engineering analysis, NASA s space shuttle program learned that foam debris was an "acceptable risk, a turnaround or maintenance issue, and not a safety of flight issue. 

Finding 12. The bipod foam loss during STS-112 yielded limited damage to the solid rocket boosters, and even if designated as an in-flight anomaly, would have been unlikely to be considered a safety of flight issue. ... 

While risk was an explicit, albeit ambiguous, part of the vocabulary of safety within NASA s space shuttle program, the Mission Management Team, concerned with guaranteeing safety of the shuttle vehicle and crew, did not explicitly consider risk or uncertainty. In particular, an examination of the written transcripts of the STS-107 MMT meetings reveals that, while safety of flight was considered a critical issue for its consideration, no direct acknowledgments of risks and uncertainties were contemplated. 

The CAIB does define the phrase No Safety of Flight Issue, as we wUl discuss further below. It does not define, however, the terms safety or safety culture, as used by the CAIB itself, but unphcitiy treats them as objective and unproblematic. 

DAT briefs Mission Evaluation Room manager Don McCormack that while many uncertainties remain, their analysis confirms this is not a safety of flight issue. An hour later McCormack relays this message to the Mission Management Team. 

On Wednesday, January 29, William Ready, associate Administrator for space flight, actually declares that NASA would accept a DOD offer of imagery, but since there is no safety of flight issue, such imagery should only be done on a low-priority not-to-interfere basis. Ultimately, no imagery was taken (CAIB, 2003 166). [missed opportunity 8]... 

Based on this logic, it s possible that shuttle management s pessimistic perceptions about both DOD s imagery capabilities and their own in-flight repair capacity may have unconsciously influenced their interpretation of the foam strike as a turnaround maintenance issue and not a safety of flight concern, thus helping to explain their... 

After a series of interactions between the different parts of NASA s distributed knowledge system, what began as an out-of-family event was eventually categorized as an accepted risk and no longer a safety of flight issue. As the shuttle re-entered the Earth s atmosphere on February 1, hot plasma breached the RCC tiles and the shuttle disintegrated. The CAIB report said ... 

---