LTE & Crosswind Component Calculator
Compute the crosswind component and Loss of Tail Rotor Effectiveness (LTE) risk for a helicopter operation. The calculator decomposes the wind into headwind/tailwind and crosswind components and classifies the relative wind angle against the FAA AC 90-95B LTE risk zones. Helicopter-specific - fixed-wing crosswind calculators do not model LTE.
Calculator inputs and results
Wind
Helicopter state
Source: FAA AC 90-95B "Unanticipated Right Yaw in Helicopters". Risk zones apply to single-main-rotor helicopters with counter-clockwise rotor (US convention). For European (clockwise) rotors the zones mirror to the left. LTE risk is highest at low airspeed (below ETL ~16-24 KIAS), low altitude, and high power settings. Standard crosswind formulas: headwind = wind × cos(relative angle), crosswind = wind × sin(relative angle).
How this calculator works
Relative wind angle = (wind direction - helicopter heading + 360) mod 360. Wind direction follows aviation convention: the direction the wind blows FROM. Relative angle is measured clockwise from the helicopter nose.
Crosswind component = wind speed × sin(relative angle). Headwind/tailwind = wind speed × cos(relative angle). Standard FAA AC 00-2A formulas, identical to fixed-wing usage.
LTE risk zones per FAA AC 90-95B (counter-clockwise rotor, US convention): 285°-315° = main rotor disc vortex interference; 120°-330° = tail rotor vortex ring state / reduced effectiveness; 210°-330° = weathervaning yaw tendency. Risk is amplified at airspeeds below ETL (effective translational lift, ~16-24 KIAS) and at low altitude.
Recovery per AC 90-95B: lower the collective to reduce torque demand and rotor blade loading; apply forward cyclic to gain airspeed and translational lift; full opposite pedal as needed. Do not pull collective - that increases torque demand into a tail rotor that is already saturated.
Default assumptions & sources
Every default value the calculator starts with, the realistic range you'd see in the field, and the source we used to set it.
| Input | Default | Typical range | Source |
|---|---|---|---|
| Wind direction format | FROM (meteorological) | 0-359° | FAA Aeronautical Information Manual (AIM) / AC 00-45 |
| Effective Translational Lift | ~16-24 KIAS | Varies by type | FAA-H-8083-21B Ch 5 + AC 90-95B |
| Rotor direction | Counter-clockwise (US) | US OEMs | AC 90-95B applies as published; European clockwise rotors mirror the risk zones to the left |
What's not modeled
The calculator covers the major cost and time line items. These additional factors apply in some cases but aren't included in the estimate:
- Mountain wave, rotor wash, and turbulent boundary layer effects near terrain
- Tail rotor authority degradation at high density altitude
- Aircraft-specific tail rotor design (open vs ducted vs fenestron) - fenestrons (AS350/H125, EC135) are generally less susceptible to classic LTE
- Pedal authority remaining as a function of gross weight and power demand
- Specific aircraft cyclic and pedal authority limits at low airspeed
Frequently asked questions
What is LTE (Loss of Tail Rotor Effectiveness)?
LTE is an uncommanded right yaw (in counter-clockwise US-rotor helicopters) that occurs when the tail rotor cannot produce enough thrust to counter main rotor torque. It is not a tail rotor failure - the tail rotor is still working, but its effectiveness is reduced by aerodynamic conditions including specific relative wind angles, low airspeed, high power demand, and high density altitude. Source: FAA AC 90-95B.
#What are the LTE risk wind angles per AC 90-95B?
Three overlapping zones for counter-clockwise rotor helicopters: 285°-315° relative (main rotor disc vortex interference into the tail rotor), 120°-330° relative (tail rotor vortex ring state), and 210°-330° relative (weathervaning yaw tendency). The 210°-330° zone is the broadest and most commonly cited in accident reports.
#How do I recover from LTE?
Per AC 90-95B: (1) Lower the collective to reduce torque demand on the tail rotor. (2) Apply forward cyclic to gain airspeed and re-establish translational lift. (3) Apply full opposite pedal (left pedal in US-convention rotors) as needed. Do NOT pull the collective - additional power demand worsens tail rotor saturation. Recovery requires altitude and airspeed margin.
#Why is LTE worse at low airspeed?
Below effective translational lift (~16-24 KIAS), the tail rotor operates in disturbed air from the main rotor and may not produce its full design thrust. Above ETL, the tail rotor encounters cleaner air and produces nominal thrust. This is why LTE accidents typically occur during hover, takeoff, low-speed maneuvering, or terminal approach.
#Do European helicopters (clockwise rotors) have the same risk zones?
The physics is the same but the risk zones mirror. For clockwise main rotors (most European OEMs including AgustaWestland/Leonardo), the equivalent LTE risk zones are on the LEFT side of the helicopter (mirror of 120°-330° becomes 30°-240°). Uncommanded yaw direction is also reversed. This calculator displays US-convention angles; verify against your aircraft's published procedures.
#Related guides & tools
This calculator provides estimates only. Actual aircraft performance and regulatory compliance vary by specific aircraft serial number, density altitude, gross weight, equipment installations, and operator's FAA-approved General Operations Manual / OpSpec. Always verify with primary sources: the FAA (faa.gov), 14 CFR (eCFR at ecfr.gov), your aircraft Rotorcraft Flight Manual (RFM) or Pilot Operating Handbook (POH), the relevant FAA Advisory Circular, and NTSB safety studies for the operational profile.