Aircraft Wing Compartment Liner Concept to Reduce
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Aircraft Wing Compartment Liner Concept to Reduce obert F. Salmon November 1992 OT/FAA/CT-TN 92/34 ile at the Technical Center U.S. Deporthnf of Transportam FedcrcllAVhtiOn AdministmnMl Technical Center Atlantic City International Airpon. N.J. 08405 NOTICE This document is disseminated under the sponsorship of the U.S. Department of Transportarion in the inreresr of information exchange. The United States Government assumes no liability for the contents or use thereof. The United States Government does not: endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the objective of this report. frehnicol Rqort Documentation Pogc 1. Report No. 2. Government Accession No. 3. Rmcipiont'r Catalog No. DOTIFAAICT-TN92I34 4. Title and Subtitlo 5. R.port 0.10 AIRCRAFT WING COMPARTMENT LINER CONCEPT TO liEDUCE FUEL SPILLAGE 8. Pmrfotminp Organization Report NO. 7. Author's) Robert F. Salmon DOTIFAAICT-TN92I34 9. Pmrforming Orgaization Nome md Address 10. Work Unit No. ITRAIS) Federal Aviation Adminisrration Technical Cencer 11. Controct or Grant No. Atlantic City Internarional Airport, NJ 08405 13. TYPOof Rmport ond Pariod Coverod 12. Sponaoring Agorrsy Norno and Addross U.S. Department of Transportation Technical Note Federal Aviation Administration Technical Center 14. Sponroring Apency Cod. Atlantic City International Airport, NJ 08405 ACD-2 10 16. Abstroct This report describes a new concept in aircraft fuel tank design. The concept has the potential for reducing the spillage from an aircraft fuel tank which has been ruptured during what could be considered a survivable crash. The time element is very critical for survival after a crash. By reducing the .amount of fuel spilled during the first minute after the aircraft comes to rest, the probability of passenger survival can be greatly enhanced. The penalties in weight and reduction in fuel capacity resulting from installing the new containment system appear to be minor. The reduction in fuel capacity in a 707 type aircraft, for instance, would be approximately 44 gallons or 0.32 percent of total fuel capacity. 17. Kmy Words . I 18. Distribution Stotmmmt Fuel Containment Document is on file ar the Technical Fuel Spillage Center Library, Atlantic City Reticulated Foam International Airport, New Jersey 08405 Fuel Bladders 19. Seturity Clossif. (of thia report) a0. Security Closiil. (ot'thir pagd 21. No. of Popes 22. Price Unclassified Unclassified 29 TABLE OF CONTENTS Page EXECUTIVE SUMMARY v INTRODUCTION 1 Purp0s e 1 Background 1 DISCUSSION 1 DESCRIPTION OF A FUEL CONTAINMENT SYSTEM 3 PROTOTYPE FUEL CONTAINMENT SYSTEM 6 Compartment Liner Concept Applied to Oucboard Wing Tank 7 Compartment Liner Concept Applied to Inboard Wing Tanks 16 CONTAINMENT SYSTEM WEIGHT AND VOLUME COMPARISONS FOR BLADDERS, 20 FOAM, AND NEW CONCEPT Bladders 20 Foam 20 New Concept 20 SIGNIFICANT FEATURES OF THE CONTAINMENT SYSTEM 22 Compatibility With Existing Fuel System 22 Actuation of the System 22 Check-Out of the System 23 Operational Procedure 23 REFERENCES 23 APPENDICES -A -- Excerpt from Reference 1, Crash Resistant Fuel Cell Installation Weights B -- Specifications of Scott Foam Division’s Reticulated Foam Products iii LIST OF ILLUSTRATIONS Figure Page 1 Outboard Wing Tank 3 2 Z Ribs 4 3 Anti-Slosh Bulkhead 5 4 Tapered Section of "2" Rib 6 5 Compartment Frame Assembly 7 6 Open Top Compartment Liner 8 7 Valve in Compartment Liner 9 8 "Z" Rib Tapered Section 10 9 Modification to "2" Rib 10 10 Exploded View of Containment Design 11 11 Cross-Section of Compartment With Fuel 13 12 Outboard Wing Tank Spillage Versus Time 15 13 Schematic of Wing and Fuel Tanks 16 14 Inboard Wing Tank Liner Schematic 17 15 Inboard Wing Tank Spillage Versus Time 18 16 Inboard Wing Tank Liner Installation 19 iV .. __ . EXECUTIVE SUMMARY This report describes an innovative concept for containing fuel in the fuel tanks of aircraft involved in survivable crashes. The concept involves the use of rapid response hydraulic/air actuated closures to seal liners in Lank Compartments of a fuel cank. With the closures in operation, any fuel spillage can only come from the ruptured compartment or compartments, nor from the entire tank. However, in contrast to bladder spsrems which introduce great complexity to the fuel system, this concept is a passive system which can be installed in a commercial transport aircraft without major modification to the existing fuel system. The weight penalty and reduction in fuel capacity resulting from the installation of such a system appear to be minimal. A prototype system was built at the Federal Aviation Administration (FAA) Technical Center. Compared to alternare containment systems (i.e., fuel bladders or reticulated foam), this concept incurs lower weight and volume penalties. Installarion costs for retrofitting existing aircraft are expected to be significantly less than those incurred when using either reticulated foam or fuel bladders. This savings would result from the fact that no functional changes to the fuel system are required when this system is added to the aircraft. If the concept was incorporated in the original design of a new aircraft, the costs could be significanrly lower. V INTRODUCTION PURPOSE. The purpose of this report is to describe an innovative concept in aircrafc fuel tank design which will reduce the spillage from an aircraft: fuel tank which has been ruptured during what could be considered a survivable crash. The time element is very critical for survival after a crash. By reducing the amount of fuel spilled during the first minute after the aircraft comes to rest, the probability of passenger survival is greatly enhanced. The report is divided into four sections: . Description of a full-scale fuel tank section which was modified to incorporat:e the components of t:he new concept. Brief discussion of the potential for incorporating the concept into present day commercial carriers. Comparison of the new concept's performance penalties relative to the penalties incurred when using either reticulated foam or bladder tanks in aircraft. Discussion of the technical viabil.ity of the concept. BACKGROUND. Fuel fires are the major cause of faralities in impact-survivable aircraft accidents. Fuel flowing from ruptured fuel tanks while the aircraft is still moving can form fine, readily ignitable mists. The remaining fuel, which spills from the tank after the plane comes to a stop, also constitutes a major potential fire hazard. Dealing with the spilled fuel is the subject of this effort . The Federal Aviation Adminisrration (FAA) and other government agencies have conducted a significant amount of work on developing methods of containing fuel during accidents. Most of this past work, however, is not applicable to modern, commercial transports owing to excessive weight, cost, or range/capacitp penalties. DISCUSSION A report (reference 1) was published in 1987 which summarized the various concepts that have been considered for reducing the severity of postcrash fires. The title of the report is "Fuel Containment Concepts - Transport Category Airplanes." After analyzing the various concepts presented, a new concept was developed which appears to minimize the penalties of weight and aircraft performance and yet offers considerable promise in reducing the size of postcrash fires. The essence of the new concept is to apply the principles employed aboard a ship when the integrity of the ship's hull is threatened. Aboard a Naval ship, when an accident occurs or enemy action causes damage, the various compartments of the ship are sealed off to isolate the damage. Thus, the idea is to keep the sea out of the compartments which are still intact and minimize and isolate the impact of the damage. The same concepr. can be applied to an aircraft's fuel tanks. 1 Fire is rhe major contributor to fatalities when an otherwise survivable aircraft crash occurs. There are two major facrors in this type of situation which are the prime causes of the fatalities. One is the development of a fuel mist which occurs while the aircraft is still moving and fuel is released from a rupture in the fuel cank. The second factor is the fuel spilled from the rupzured fuel tank which results in a sizable pool of fuel on the grourid under the aircraft when it comes to rest. This pool, if exposed to an ignition source can develop into a very Large fire encompassing the aircraft. Thus, there are two problems TO be solved: one, reduce or eliminate the fuel mist fireball; and two, minimize rhe size of the fuel spill and the porential fire size. Antimisting fuel (reference 2) can address the misting and fireball problem. The fuel spillage problem is the subject discussed in this report. Over the years, a great deal of work has been done on methods (reference 1) to contain the fuel in a crash. Most of this work dealt with structural design of the wing and fuel tanks, frangible fittings for the fuel system, installation of bladders in the tanks to improve the containmenr. of the fuel, and use of reticulated foam to impede the spill rate of the fuel. Some of the modifications have been implemented in specialized aircraft. For instance, helicopters have been using bladders and frangible fittings for about 15 years and have found that they perform quite well. However, most of the containment proposals over the years are not readily adaptable to typical commercial transport aircraft. The modifications required would be prohibitive in weight, cost, or reduction in fuel capacity, thus reducing the maximum range of the aircraft. This report describes a containment concept which would not penalize the aircraft performance to any significant extent and would not compromise existing fuel systems. 2 DESCRIPTION OF A FUEL CONTAINMENT SYSTEM Many studles over the years have defined the causative factors which influence the potential for fatalities in aircraft accidents.