Fuel Tank Safety

BACKGROUND

This subject was an aspect of the Jet A/Jet B fuel controversy referred to in the History Section of this website since one of the accidents mentioned involved a fuel tank explosion while the passengers were evacuating from the almost undamaged aircraft. Subsequently one of the Group's priorities became passenger survival aspects of low speed accidents, particularly those with a ground fire, whatever the fuel.

This concern was given added impetus in 1985, following the fatal B737 ground fire accident at Manchester Airport. As a result of this accident the CAA sponsored a programme of research into various aspects of emergency evacuation. This work was carried out by Cranfield University under the leadership of Professor Helen Muir. One of the recommendations from the research was that minimum passageway widths through cabin bulkheads should not be less than 30 inches. Accordingly, in 1989 the CAA submitted to the JAA a Notice of Proposed Amendment to JAR 25 which, if accepted, would raise the minimum permitted passageway width from 20 to 30 inches. The Group strongly supported this proposal and is dismayed that 23 years after the Manchester accident the proposal has not been agreed by EASA, following its consultation process using NPA-2008-18.

It has now to be recognised that the ASG's, perhaps somewhat idealistic stance on the Bulkhead issue, is unlikely to prevail, as the move towards harmonisation within the EU, and with the FAA, has become unstoppable. The formation of EASA is described elsewhere in this website. It had been hoped that this new Agency would have been able to agree and progress proposed safety measures more swiftly than has been the case with the JAA. However in October 2008 EASA stated that it proposed to make no change to the 20 inch minimum gap.

The ASG's position on this matter is as follows:

In addition to the bulkhead issue highlighted by the Cranfield research into the Manchester accident referred to above, three specific design weaknesses were identified in relation to typical Type III exits in use at that time:

  1. Delays in opening these 'self-help' exits, often 15-30 seconds, due to the passengers being untrained, not having read the instructions and the relatively complicated two-step opening process.
  2. The exit hatch not being thrown out onto the wing, as intended, but placed on a seat (usually subsequently ending up on the floor) or placed on the floor, thus causing a major obstruction delaying evacuation.
  3. The tendency in a life threatening situation (competitive behaviour) for these exits to block when two people try to exit at the same time, or with a single obese passenger. This can prevent further evacuation for long periods (and necessitated abandoning such evacuation tests when this happened at Cranfield). The intention at that time was to replace these exits on new aircraft types by larger exits (Type II hatches or Type 1 doors).

The Boeing 'Automatic Opening Exit' (AOE) provides part of the solution, where a single movement of a lever results in the hatch, now hinged at the top, to open upwards by spring action such that there is no obstruction. This addresses and removes the first two weaknesses, but the 'blocking' - the most serious - remains. The AOE is a valuable palliative but only applies to later Boeing 737s and does not address the main problem.

The Air Safety Group is concerned that there is now no plan to address this problem any more and we agree with the International Airline Passenger Association that this is unacceptable. It is inappropriate to allow such exits to continue to be used to meet the evacuation requirements on new types of large airliners. The most fundamental flaw in Type III exits (blocking) remains and the Regulatory Authorities and industry have allowed this to slip out of the proposed work programme. This major potential hazard to evacuating aircraft, that became evident and posed such a problem in 1985, remains and is still in need of rectification.

As mentioned, other major cabin safety issues of concern relate to the air quality within the cabin and the potential for overloading of the overhead bins by excessive cabin baggage. Both issues are being actively progressed by members of the Air Safety Group with letters now having been sent to EASA and the aircraft manufacturers.