TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: Joint Strike Fighter

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop a method to measure control surface buffet loads on in-service fleet aircraft to be used in individual aircraft structural life tracking.

DESCRIPTION: An aircraft's usage within its operational envelope contains repeated loads due to maneuvers, ground events, and dynamic events such as buffet. Buffet loading is due to the dynamic response of the tail and control surfaces. Aircraft are instrumented and the flight loads are recorded in flight to obtain a load history for individual fleet aircraft. This data is downloaded and used in structural fatigue life tracking methods to quantify structural life used by the aircraft. Currently fielded sensors either inadequately capture buffet loading or do not measure at the correct sampling rate to capture buffet. Inadequate or missing buffet loads can lead to cracks that occur earlier than predicted by analysis and fatigue life tracking. Because buffet impacts are typically not fully known during design, the fatigue life of aircraft structure is significantly affected by operational usage which contains buffet flight maneuvers. The very transient nature of these maneuvers makes the dynamic response of the tail and control surfaces difficult to capture with currently fielded sensors. Structural lives of wings and control surfaces have been limited due to the affects of buffet loading. Buffet on control surfaces is measured as a function of angle of attack and dynamic pressure, but is also influenced by other factors. Premature cracks combined with time-consuming in-service crack inspection techniques demand accurate in-service control surface buffet load measurements which will lead to more accurate fatigue-life predictions. Innovative methods are sought to measure control surface buffet loads on in-service fleet aircraft to be used in individual aircraft structural life tracking.

PHASE I: Develop and determine technical feasibility of an innovative method that can be used to measure control surface buffet loads on in-service fleet aircraft.

PHASE II: Develop, verify and demonstrate the method developed in phase I through coupon, component and possibly full scale test applications.

PHASE III: Mature the process so that it can be used by any data recording unit in the fleet to capture control surface buffet loads. This would include developing and maturing any equipment or models necessary to a fleet readiness state.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Civil aircraft are heading toward structural life tracking where control surface buffet and gust load measuring will be needed. Civil aviation, commercial airlines as well as private, could benefit.

REFERENCES:
1. Bisplinghoff, R. L., Ashley H., and Halfman, R. L. "Aeroelasticity." Dover, (1996).

2. Grover, Horace J. "Fatigue of Aircraft Structures." Batelle Memorial Institute, 1966 (NAVAIR 01-1A-13).

3. Molent, L. "A Review of a Strain and Flight Parameter Data Based Aircraft Fatigue Usage Monitoring System." Proceedings of the USAF Aircraft Structural Integrity Conference (Dec 3-5, 1996).

4. Hill, B., Levinski, O., and Watmuff, J. "Experimental Investigation of Generic Buffet Configuration." 24th Applied Aerodynamics Conference. 5-8 June 2006, San Francisco, CA. (AIAA 2006-3485)

5. Levinski, O. "Vertical Tail Dynamic Response in Vortex Breakdown Flow." DSTO. June 2003. (DSTO-RR-0256)

KEYWORDS: aircraft; buffet; load; measurement; sensor; control surface

** TOPIC AUTHOR (TPOC) **

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