Jet engines are tested at several points in their life cycle, including prototyping and development; after the installation of the engine in the aircraft; and after repairs, rebuilds, or inspections. During the design and development phase, the manufacturer will perform an exhaustive list of tests at both indoor and outdoor test facilities.
Among other factors, the results of this testing must prove that the engine can function in the face of environmental hazards such as snow, ice, hail, water/rain, sand, debris, and dust, and still meet all of its required safety and operational standards. Engines must also pass significant standardized testing for stress tolerances, endurance, and efficiency. This testing is quite expensive and accounts for a sizeable portion of most design and development budgets. In addition, thorough full-sized jet engine testing often takes years to complete when performed on new designs and jet engine models.
Subscale Jet Engine Testing
Running full-sized jet engines through a complete gamut of testing is often cost-prohibitive during the development phase. Using subscale jet engines makes engine testing much more affordable so that designers and engineers can analyze multiple factors, including high cycle fatigue (HCF) on blades, coating durability, oxidation and corrosion limits and susceptibility, creep and fatigue, volcanic ash and CMAS testing, and fuel burn studies.
Jet engines must be able to consistently perform well in extreme environments for long periods of time. Reliable functionality is central to a jet engine’s operation. Subjecting a jet engine’s parts to combustible gas products and high temperatures helps designers and engineers understand how to refine and strengthen their work.
To execute that level of testing on a full-scale jet engine is costly, time-consuming, and often nearly impossible, especially when the engine in the early stages of development. Using more realistic conditions for testing, designers and engineers employ subscale jet engines to gather feedback so that they can identify and eliminate any costly risks before constructing full-scale engines.
Additional Jet Engine Testing Methods
There is a wide range of jet engine tests that test used across the industry to ensure the safety and functionality of equipment. These tests include, but are not limited to:
Spin Tests
Jet engines must undergo spin testing to ensure they can tolerate extreme stress caused by centrifugal force. Testing rotors for centrifugal strength is a must for any manufacturer of high-speed machinery, since improper rotating components can fail when exposed to volatile force, causing equipment failures, damage, or worse. Typically performed in a vacuum, spin tests remove the high air friction losses that make it challenging to propel most rotors at higher speeds. In addition, the vacuum diminishes the chance of an explosion during a rotor failure.
On-Wing Engine Testing
Following the replacement or inspection of an engine, on-wing tests must be performed. On-wing tests are also often performed periodically after engines have been in frequent operation, such as with an airline or during military service. On-wing engine tests perform a thorough analysis to ensure that the engine produces the necessary thrust, that the engine rotors are balanced, and that there are no leakages.
Off-Wing Engine Testing
After an engine is removed for maintenance or a rebuild, off-wing tests must be performed before the engine is installed on the wing. To certify that an engine is ready for reinstallation, an exhaustive list of tests must be conducted These tests ensure that the engine complies with all technical standards and is safe to operate. An off-wing engine test is also required every five years after the engine achieves its maximum flying hours and is removed for refurbishment.
Testing jet engines at every stage not only ensures the safety of its operation but allows designers and engineers to improve their work by incorporating analysis and feedback. Submitting the engine and its hardware to formidable environmental conditions and extreme stress testing helps to safeguard manufacturers and consumers alike.
Resources:
- The Testing Capabilities of Subscale Jet Engine Rigs – Part 1
- The Testing Capabilities of Subscale Jet Engine Rigs – Part 2
- How Do We Test Jet Engines?
- Watch Ge Test Its Jet Engines
- How is a Jet Engine Tested?
Image Credit: Steve Mann/Shutterstock.com