What is loss of tail rotor effectiveness (LTE)?

Loss of tail rotor effectiveness, commonly referred to as LTE, is when the ability to provide anti-torque thrust from the tail rotor is ineffective or highly unreliable.

Notwithstanding mechanical problems, there are several wind conditions that impact the tail rotor’s ability to provide anti-torque thrust: main rotor disc interference, tail rotor vortex ring state, and weathercock stability.  Main rotor disc interference may occur when there is a wind between 285-310-degrees.  From this angle, the main rotor vortices can be blown into the tail rotor, making the tail rotor operate in turbulent air.  A tail rotor ring state may occur when the wind is from 210-330 degree as there is the potential for the wind to blow tail rotor’s vortices into the tail rotor and the tail rotor can end up in a vortex ring state.  When the wind is from 120-240 degrees, the helicopter will want to weather vane into the wind, making it operate in extremely turbulent air.

Diagram showing wind conditions leading to loss of tail rotor effectiveness or LTEWhen there is pilot discretion to approach a landing site with left or a right cross wind, a right crosswind minimizes the likelihood of LTE.  Often, a pilot has the discretion on the approach to a landing site, so the wind should be considered, particularly on final where tail rotor use increases.

Reference(s):

FAA-H-8083-21A – Helicopter Flying Handbook pg. 11-17
Principles of Helicopter Flight, 2nd Edition, pg. 69

Other Helicopter Flight Conditions

Tagged under:

Leave a Reply

Your email address will not be published.