- Author
-
Picard, B.
|
Hartsig, D.
- Title
- F/A-18 Engine Bay Fire Reduction. Final Report. March 31-June 23, 1992.
- Coporate
- Naval Air Warfare Center Aircraft Division, Patuxent River, MD
- Sponsor
- Naval Air Systems Command, Arlington, VA
- Report
-
NAWCADPAX-TM-92-172-SA,
July 22, 1993,
172 p.
- Distribution
- Available from National Technical Information Service Distribution authorized to U.S. Government agencies and their contractors
- Keywords
-
aircraft engines
|
ventilation
|
temperature
|
supersonic aircraft
- Identifiers
- engine bay; VEN boots
- Abstract
- The F/A-18's high engine bay fire incident rate has been attributed primarily to hardware failures which result in fuel/oil leaks and ignite inside the engine bay. Tests conducted at NAVAIRTESTCEN in 1989 identified flow reversal from Variable Exhaust Nozzle (VEN) cavity through the actuator holes as the source of the high temperatures. The objective of this program was to evaluate three engine and airframe modifications designed to cool down the engine bay and/or reduce the potential for fire spreading to the other bay. Modifications were evaluated independently and together, consisting of VEN boots designed to isolate the VEN cavity, modified bay air inlet scoops for more flow, and finally, keel close-out hardware designed to prevent the potential for fire migration to the other bay. Tests documented flow entering the engine bay through the aft keel openings where flow was thought originally to discharge. The potential exists for an engine bay fire to generate sufficient internal pressure to reverse the keel flow in one bay while the other continues to induct air, hot gases or flames, offering a possible explanation for development of a dual engine bay fire. Supersonic baseline tests documented engine b-sump vent induces ejector flow which helps cool the engine bay and should be retained. High temperatures at/around the forward engine mounts can degrade adjacent engine components, creates an ignition hazard and can impact airframe structural life. During subsonic flight, the VEN cavity interior surface temperature and the anti-ice duct represent the only potential ignition threats. During supersonic flight, the aft bay, forward bay, and VEN cavity are potential free air ignition regions, and the VEN actuators, flamesensor, A/B case, anti-ice duct and VEN cavity are potential ignition surfaces. With the exception of the anti-ice duct, VEN boots eliminate the ignition potential of all known surfaces and components. VEN boots will reduce the potential for engine bay fires and is an enhancing characteristic which should be incorporated in future designs. VEN boots should be incorporated on all F/A-18 F404-GE-400 engines. The contractor should modify the mid-frame and b-sump vent interface to prevent engine bay backwash while maintaining ejector flow. VEN boots is the single most effective engine bay modification. Of all combinations tested, VEN boots + modified inlet scoops + keel close-out provides the best overall performance on bay cooling, flow distribution, and safety.