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Report | Nov. 7, 2019

Evaluation of the V‑22 Engine Air Particle Separator (DODIG-2020-006)


Publicly Released: November 12, 2019 


The objective of this evaluation was to determine whether the Naval Air Systems Command V‑22 Joint Program Office developed an Engine Air Particle Separator (EAPS) to adequately protect the V‑22 engine while operating in all desert environments.



 The V‑22 aircraft combines the capabilities of a helicopter and an airplane. V‑22 missions include transport of personnel and cargo, and recovery of personnel. The V‑22 operates from ships and air bases, and performs missions requiring takeoff and landing at unprepared landing zones. One significant mission requirement of the V‑22 is to operate in desert environments. This can result in large amounts of soil on the ground being blown into the air and ingested into the V‑22 engine, which can contribute to premature engine failure. The EAPS’ purpose is to protect the V‑22 engine by removing soil from the air that enters the engine. The V‑22 Joint Program Office, known as the Program Manager, Air 275 (PMA‑275), at Naval Air Station Patuxent River, Maryland, manages the V‑22 program. The PMA‑275 recognized that the EAPS was not removing enough soil from the air entering the engine and initiated two EAPS redesign efforts, in 2010 and 2011. However, the PMA‑275 determined that neither redesign was a viable option. Specifically, the first EAPS redesign had inconsistent test results, and the second EAPS redesign adversely affected the ability of the V‑22 to operate as an airplane.

In 2018, the PMA‑275 initiated a third EAPS redesign effort. The goal of that effort was to increase the ability of the EAPS to separate soil from the air entering the engine by improving the existing EAPS components.



The PMA‑275 did not develop an EAPS that protects the V‑22 engine while operating in all desert environments. Specifically, the PMA‑275 did not include a specification in the original EAPS design that required the EAPS to meet the engine manufacturer’s specification for cleanliness of the air flowing into the engine. Despite two unsuccessful redesign efforts, the PMA‑275’s third EAPS redesign effort will also not meet the engine manufacturer’s specification. The third EAPS redesign is intended to remove more soil from the air flowing into the V‑22 engine than the original EAPS; however, the soil ingested into the engine would be four times greater than the engine manufacturer’s specification allows. While PMA‑275 officials stated that it is not technically feasible to meet the engine manufacturer’s specification for air quality in a desert environment, they could not provide analysis that demonstrated whether this redesign would adequately protect the engine. Additionally, the PMA‑275 intends to test the third EAPS redesign with soil that is not representative of all environments where the V‑22 operates, relying instead on military standard soil compositions and soil concentrations based on testing from a single desert environment. This occurred because the PMA‑275 is not taking advantage of the ability to tailor military standard soil samples. As a result, the V‑22 remains at risk despite more than nine years of EAPS redesign attempts. Additionally, the PMA‑275 cannot be certain that the third EAPS redesign will correct long‑standing problems with the V‑22.



 We recommend that the V‑22 Joint Program Office Commander:

  • Conduct a review of alternatives for the EAPS and V‑22 engine so that the EAPS adequately protects the V‑22 engine in all desert environments.
  • Develop a plan to include a sampling of additional soils, whose compositions and concentrations are representative of those found in actual V‑22 operational environments, in the testing for the EAPS and V‑22 engine.


Management Comments and Our Response

The V‑22 Joint Program Office Deputy Program Manager, responding for the V‑22 Joint Program Office Commander, stated that the PMA‑275 agreed that V‑22 operations in desert environments are a critical capability for the program. However, he disagreed with our focus on only the V‑22 EAPS subsystem, stating evaluating only one V‑22 subsystem and not the overarching program strategy to enable safe operation of the V‑22 during austere operations, does not capture the program’s plan for addressing risk. The Deputy Program Manager described a multi‑layered approach the program office was taking to address safe operation of the V‑22 and stated that extensive research has led the PMA‑275 to conclude that it is not technically possible to develop, integrate, and field an EAPS that is fully capable of protecting the V‑22 engine from all possible soil types and concentrations for unlimited durations. The Deputy Program Manager stated that the PMA‑275 intended to continue its plan to improve the EAPS subsystem as part of a multi‑layered approach to address safe operation of the V‑22, which includes testing that will characterize the performance of the V‑22 engine and EAPS during desert operations.

Although the V‑22 Joint Program Office Deputy Program Manager disagreed with our recommendation to conduct a review of alternatives for the EAPS and V‑22 engine, several components of the multi‑layered approach for improving the overall safety of the V‑22 aircraft directly address concerns discussed in our finding. For example, the PMA‑275 is developing a near real‑time Cockpit Engine Health monitoring system. In addition, the PMA‑275 plans to perform testing to characterize the performance of the V‑22 engine and EAPS in desert environments and use the results of the testing to update the specification for the third EAPS redesign effort. Therefore, the recommendation is resolved but open. We will close this recommendation after we review the results of actions taken by the PMA‑275.

Comments from the Deputy Program Manager did not address the specifics of our recommendation to develop a plan to include a sampling of additional soil compositions and concentrations; therefore, the recommendation is unresolved. However, we revised this recommendation to clarify our intent that the PMA‑275 test soil samples which are representative of actual operational environments for testing of the V‑22 EAPS and engine, instead of soil samples from all desert environments. We request that the V‑22 Joint Program Office Commander provide comments on the revised recommendation no later than December 9, 2019.


This report is the result of Proj. No. D2018-D000PT-0202.000.