Engine and APU - Water Ingestion Test

The intent of this post is to share ideas for engineers involved in planning and conducting the Water Ingestion test for Turbine Powered Airplanes.

Our involvement with our clients goes from pre-planning to executing and providing a full analysis of the results including lessons learnt and compliance reports if applicable. We help our clients from start to end making sure tests go smooth and are executed on time.

There is a lot that goes into planning for water ingestion test. From finding the right place, to performing a runway survey, to aircraft configuration, instrumentation and of course the water trough construction and removal! However, in this post we focus on the different flight phases during which tests i executed.

For starters, the airplane should be tested under worst case scenario such as maximum allowable weight, most forward C.G and maximum allowable tires service pressure.

Just like in any other testing, water ingestion test should be carried out in a build up approach from low speed to higher speed with an increment of no more than 20 knots until a critical speed is determined. The number of test runs should be sufficient to demonstrate all critical phases of the takeoff, landing and taxi operations.

The critical speed will be determined by the test conductor and the authority witness of the test (if applicable). Generally, critical speed can be determined during the takeoff test cases when engine thrust settings are high. The airplane tires cause bow waves, side spray, and rooster tails which can collect into concentrated water streams that may be ingested by the engine.

 Taxi

Airplane speeds, engine thrust setting and configurations appropriate for normal taxi operation should also be tested. Typically, taxi speeds are 20 and 40 knots. Higher speed will be covered during takeoff test cases.

For airplane with engines mounted on wing, the taxi test cases are more likely affected the APU.

 Simulated Takeoff

Engine thrust setting and configurations should be appropriate for Takeoff.

Airplane speed can be tested from 60kts, 80kts, 100kts and/or up to V1 speed to determine the critical speed. After a number of tests runs at different speeds, it is obvious by post-test inspection of the wetted surface that water ingestion would not occur even at higher speed.

This critical speed can be used for RTO and Landing test cases.

Rejected Take-Off

Using the critical speed found in section 4.3 for this test with engine thrust setting and configuration appropriate for a rejected take-off.

Simulated Landing

Test should be conducted with and without Thrust Reverser deployment using the critical speed found in simulated take-off tests and appropriate configuration for landing.

If you need more info, please reach out to ES3AERO. We have the experience and processes in place to ensure a successful water ingestion testing campaign!