Special Condition UK.SC.C.0001 Installation of Conformal Rear Centre Tank - Crashworthiness Conditions

For comments on the proposal that the CAA introduces a special condition to be used for the crashworthiness conditions of a conformal rear centre fuel tank installation on a large transport aeroplane.

The UK CAA is consulting on a Special Condition that is applicable to CS-25 Large Aeroplanes.

This Special Condition is to address the design change that introduces a conformal fuselage structural fuel tank to the aeroplane, also called rear centre tank (RCT), and the unusual design of the RCT should prevent fuel spillage in sufficient quantities to start a serious fire in an otherwise survivable crash event.

The Consultation Paper Special Condition UK.SC.C.0001 Issue 1 provides the full detail of the identified issue, and the associated Special Condition.

We received 1 response.
The response agrees that additional guidance for fuel tank crashworthiness is appropriate and recognised that the proposed special condition is substantively similar to the European Union Aviation Safety Agency (EASA) special condition SC-E25.963-01; however, the responder did not consider that special conditions were necessary to address this novel design feature and that establishing acceptable means of compliance with the introductory requirement stated in 14 CFR 25.963(d), and ensuring the applicant makes every practicable consideration to ensure protection of fuel tanks in more severe crash conditions that exceed, or are not captured by, the conditions specified in 14 CFR 25.963(d)(1) through (d)(5), especially tanks located in the fuselage below the main cabin floor, is an acceptable approach to this novel design feature.

We acknowledge the response and thank the responder for their suggestion. The CAA believes that creating the Special Condition rather than a Means of Compliance provides a stronger, clearer criteria that the aircraft must achieve for this unusual configuration and the specific crashworthiness case, and that aligning with the Certificating Authority’s approach, given the common requirements set on this project, is more appropriate in this case.