Aviation Recommendations - 2006

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Reassessment of Responses to Aviation Safety Recommendation A06-10

Existing Production Aircraft

Background

On 30 May 2000, the pilot of a Cessna 177B Cardinal was attempting to take off from a grass airstrip at Calling Lake, Alberta. The aircraft struck trees during the initial climb, struck the ground, and burst into flame. The two occupants were exposed to smoke and flame for some time. One occupant was fatally injured due to the effects of fire, and one sustained serious burns.

The accident investigation identified fuel system crashworthiness as a small-aircraft safety deficiency. In light of that finding, the Transportation Safety Board of Canada (TSB) identified a need to examine the extent to which fuel system crashworthiness and other safety deficiencies contribute to the risks associated with post-impact fire (PIF) in otherwise survivable accidents, and to consider the risk control options available to mitigate those risks.

According to TSB data from 1976 to 2002, PIF occurs in approximately 4 per cent of accidents involving small aircraft; however, these accidents account for approximately 22 per cent of the fatalities and 11 per cent of the serious injuries caused by all accidents. Overall, 6.2 per cent of fatal injuries and 3.8 per cent of serious injuries that resulted from small-aircraft PIF accidents were related to fire. Because small aircraft have a higher accident rate with a correspondingly greater number of PIF accidents, more defences are required to mitigate the risk of PIF. Considering these factors, the Board identified the need to conduct a Safety Issues Investigation.

The Board concluded its investigation and released report SII A05-01 on 29 August 2006.

Board Recommendation A06-10 (29 August 2006)

There are a large number of small aircraft already in service and the defences against PIF in impact-survivable accidents involving these aircraft are and will remain inadequate unless countermeasures are introduced to reduce the risk. The most effective ways to prevent PIF in accidents involving existing small aircraft are to eliminate potential ignition sources, such as hot items, high-temperature electrical arcing and friction sparking, and prevent fuel spillage by preserving fuel system integrity in survivable crash conditions. Technology that is known to reduce the incidence of PIF by preventing ignition and containing fuel in crash conditions may be selectively retrofitted to existing small aircraft, including helicopters certified before 1994. Therefore, the Board recommended that:

To reduce the number of post-impact fires in impact-survivable accidents involving existing production aircraft weighing less than 5700 kg, Transport Canada, the Federal Aviation Administration, and other foreign regulators conduct risk assessments to determine the feasibility of retrofitting aircraft with the following:

• selected technology to eliminate hot items as a potential ignition source;
• technology designed to inert the battery and electrical systems at impact to eliminate high-temperature electrical arcing as a potential ignition source;
• protective or sacrificial insulating materials in locations that are vulnerable to friction heating and sparking during accidents to eliminate friction sparking as a potential ignition source; and
• selected fuel system crashworthiness components that retain fuel.

A06-10

Transport Canada's Responses to A06-10 (20 November 2006 and 29 January 2007)

Transport Canada's (TC) response dated 20 November 2006 states that it is not aware of any aviation industry initiatives to retrofit production aircraft in the manner suggested in Recommendation A06-10. Furthermore, it states that, until such technology is available, viable and required, it cannot conduct a risk assessment or mandate a retrofit to production aircraft. It concludes by stating that a study would be required to clearly identify the benefit of such an undertaking. The final paragraph of the response states that the Department is not in a position to commit the necessary resources at this time.

In its second response dated 29 January 2007, TC states that it would be inappropriate for TC to mandate changes to current production aircraft as suggested in Recommendation A06-10. TC indicates that it will review design proposals from industry in light of TSB's recommendations to assure that such modifications meet the highest standards possible.

Board Assessment of the Responses to A06-10 (12 September 2007)

TC's initial response dated 20 November 2006 states that it cannot conduct a risk assessment to determine the feasibility of retrofitting aircraft, as suggested in Recommendation A06-10, because a study must first be undertaken to establish that pertinent technologies are available, viable and required. No action plan to conduct such a study is provided in TC's response.

TC's follow-up response dated 29 January 2007 states that mandating changes to current production aircraft as suggested in Recommendation A06-10 would be inappropriate. This statement is incongruous as Recommendation A06-10 makes no mention of mandating changes but rather suggests that risk assessments be conducted. In lieu of any TC initiative to conduct risk assessments, TC would react to technology proposals from industry to ensure that such modifications meet the highest standards.

Because TC's responses contain no action or proposed action that will reduce or eliminate the risks associated with this deficiency, TC's overall response to Recommendation A06-10 is assessed as Unsatisfactory.

Next TSB Action (12 September 2007)

The Board will monitor subsequent responses from TC and the other addressees of Recommendation A06-10 to determine to what extent, if any, those responses will have a positive effect in mitigating the validated risks established in the preamble to the recommendation, both in the short and the long term.

Transport Canada Response to A06-10 (15 February 2010)

TC's response indicates that it supports the TSB objective of reducing fatalities and serious injuries due to post-impact fires in general aviation aircraft however; implementation of these recommendations would require an immense resource effort. The response further states that other safety initiatives have a higher priority.

Board Assessment of the Response to A06-10 (28 July 2010)

TC's latest response makes no effort to explain its conclusions that an immense resource effort would be required to execute the objectives of Recommendation A06-10 and that such resources would detract from other safety initiatives.

Meanwhile the post-impact fire experience remains high. Preliminary research reveals that since 01 January 2005 the Board has recorded 99 occurrences that involve a post-impact fire phase/event combination. The majority of these occurrences involved aircraft weighing less than 5700 kg. A word string search of the NTSB database for the same timeframe turned up records of over 300 general aviation accidents where post-impact fire is referenced.

Again TC has failed to address the risks associated with the deficiency identified in Recommendation A06-10 it would appear that TC has in fact declared that it plans no further action.

Because TC's responses contain no action or proposed action that will reduce or eliminate the risks associated with this deficiency, the overall response to Recommendation A06-10 is assessed as Unsatisfactory.

Next TSB Action (28 July 2010)

The Board has determined that as the residual risk associated with the deficiency identified in Recommendation A06-10 is substantial and since no further action is planned by TC continued reassessments will not likely yield further results.