Overview of Vehicle Integrated Propulsion Research (VIPR) Testing
Authors: Hunter Gary W. , Lekki J. D. , Simon D. L. 
Published: February 2020

Maintaining safe operation of an aircraft is a major emphasis of the NASA Aviation Safety Program [1]. An Integrated Vehicle Health Management (IVHM) system aims to maintain vehicle health through detection, diagnostics, state awareness, prognostics, and lastly, mitigation of detrimental situations for each of the vehicle subsystems and throughout the vehicle as a whole [2]. Major subsystems associated with a vehicle wide IVHM system are the airframe, avionics, and propulsion systems. Each subsystem has its own challenges associated with development of IVHM technologies.

One particular challenging subsystem for vehicle health management is related to Propulsion Health Management (PHM). The engine is a complex system with a range of operating components whose failure can affect passenger safety. Reliable operation of these engines is critical for aircraft safety. The harsh environment conditions within an engine often present significant challenges for the integration and application of health management systems. In parallel, diagnostic systems often have to perform evaluations with limited sensor information, while evaluating a complex system whose components include gas path, turbomachinery, hydraulics, and other components.

Demonstration of Propulsion Health Management technologies is critical for their commercial acceptance. A major aspect of ongoing NASA Propulsion Health Management work is demonstration of these maturing technologies on an operational engine in series of tests called Vehicle Integrated Propulsion Research, or VIPR. This paper gives a brief overview of the VIPR series of tests, the technologies involved in this testing, and how this approach is being used to advance the commercialization and acceptance of these technologies.

VIPR is a means to test and evaluate emerging health management technologies on a commercial engine, incorporating new sensors directly on the engine, providing seeded fault scenarios, and evaluating advances in engine diagnostics. This step is critical in order for IVHM technologies to mature from lab work and simulation demonstrations needed for industry acceptance. This work is in partnership with the Air Force, which has provided access to two F117 high bypass turbofan engines and time on operational planes for the ground-based, on-board engine tests. In these tests, the research engines are instrumented to achieve NASA and partner goals and mounted on a C-17 aircraft, though it is important to note that the planes are grounded and do not take flight.

A series of tests are planned with overall Vehicle Systems Safety Technologies (VSST) project objectives of testing health management sensors, sensor systems and algorithms on a high bypass turbofan engine under the following conditions: (1) Normal engine operations; (2) Seeded mechanical faults; (3) Seeded gas path faults; and (4) Accelerated engine life degradation through volcanic ash ingestion testing.

The first VIPR test took place in December 2011 at NASA Dryden Flight Center/Edwards Air Force Base as an on-wing ground test on a heavily instrumented high bypass turbofan engine. This test featured:

1. Emission Sensor System: Investigation of the ability of of an array of chemical sensors to detect a simulated oil leak and measure changes in sensor response with changing engine conditions.

2. Self Diagnostic Accelerometer feasibility test: Demonstrate operability of self-diagnostic accelerometer in aircraft engine environment

3. Validate Gas Path Diagnostics: Test analytical model predictions of engine parameters in the presence of bleed valve faults (failed, full open; schedule bias)

An unique feature of this VIPR series is an upcoming test, which includes the planned ingestion of volcanic ash into an engine on-board an aircraft. The primary objectives of this work are to determine the effect on the engine of several hours of exposure to low to moderate ash concentrations and to evaluate the capability of engine health management technologies for detecting these effects. Numerous observations and measurements of the engine’s performance and degradation will be made during the course of the experiment. While not intended to be sufficient for rigorous certification of engine performance when ash is ingested, the experiment should provide useful information to aircraft manufacturers, airline operators, and military and civil regulators in their efforts to evaluate the range of risks that ash hazards pose to aviation.

A research team of U.S. Government agencies and engine manufacturers are involved in this VIPR testing. This government and industry partnership is not only crucial in enabling the tests, but is also a method by which various organizations can be involved in the demonstration and maturation of technologies, facilitating potential future acceptance. A conclusion of this paper is that partnerships between developers and users of new technologies are crucial towards enabling technology commercialization and acceptance. Not only does this type of work allow the ability to mature and evaluate the technologies in environments reflective of potential application, interaction with potential technology users can provide feedback on pathways towards technology improvements and possible implementation.

References

[1] Gary W. Hunter, Richard W. Ross, David E. Berger, John D. Lekki, Robert W. Mah, Daniel F. Perey, Stefan R. Schuet, Donald L. Simon, and Stephen W. Smith. "A Concept of Operations for an Integrated Vehicle Health Assurance System," NASA Technical Memorandum 2013-217825 (2013).

[2] Gary W. Hunter, John D. Lekki, Donald L Simon. “Development and Testing of Propulsion Health Management,” Proceedings of the Workshop on Integrated Vehicle Health Management and Aviation Safety; Bangalore, India; January 2012. http://ntrs.nasa.gov/search.jsp?R=20120002753