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Loss of Tail Rotor Effectiveness [LTE]
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What is LTE?
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LTE is an uncommanded, rapid yaw towards the advancing blade which does not subside of its own accord. It can result in the loss of the aircraft if left unchecked.
- Which helicopters are susceptible to LTE?
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All helicopters with a single main rotor and tail rotor are susceptible to LTE. Those helicopters equipped with a Fenestron are affected by a similar phenomenon traditionally known as 'Fenestron Stall'. The Bell Jetranger is statistically the most likely to encounter LTE and it is this type which caused the FAA to look more closely at the problem back in the 1980s.
- Is LTE caused by a mechanical defect?
- No. LTE is caused by an aerodynamic interaction between the main rotor and tail rotor. Some helicopter types (Jetranger) are more likely to encounter LTE due to the insufficient thrust produced by having a tail rotor which meets certification standards, but which is not always able to produce the thrust demanded by the pilot.
 An R44 suffers LTE over the sea.
Incident Report |
 Camera ship suffers LTE. |
 Skycrane seems to encounter LTE. |
 Rotor & Wing article on LTE
A short article on LTE from Rotor & Wing Feb 2007.
|  IAA OAM on LTE
IAA Operations advisory Memorandum on LTE and the need to publicise its existence
|  NTSB Letter to the FAA re: LTE
A letter from the NTSB to the FAA asking them to provide more information about LTE.
|  Article on LTE from Vertical Magazine
An article from Vertical Magazine about LTE.
|  Unanticipated Right Yaw at low speeds
Filght Safety Foundation Article on LTE from the late 1980s. Also included is a short article on a maintenance error which caused the loss of a Whirlwind.
|  Flight Safety Foundation LTE Article
Flight Safety Foundation document which looks at an LTE accident in detail.
|  FAA Advisory Circular on LTE
The FAAs original document with description of and advice on LTE.
Mornington Sanford Aviation have the same article in a more readable format here.
|  Eurocopter Service Letter 1673-67-04
Eurocopter Service Letter describing LTE in clockwise rotating main rotor helicopters.
|  Eurocopter Service Letter 1692-67-04
Eurocopter Service Letter describing LTE in anti-clockwise rotating main rotor helicopters.
|  CAA FODCOM on LTE 01/2004
The CAAs official line on the history, avoidance and recovery actions upon encountering Loss of Tail Rotor Effectiveness. Now incorporated into CAP 768, kept here for reference only.
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| Registration | Type | Date | Fatal |
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| B2 | 21 May 2009 | |
| LTE during training, instructor intervened late, aircraft rolled over. |
| R44 | 21 Jul 2008 | |
| Aircraft ended up with a downwind component OGE and probably encountered LTE. Overpitched and lost control. |
| B206 | 30 Apr 2007 | |
| Rotors struck ground after helicopter was caught by gust of wind while carrying out a spot turn. Substantial damage. 2 POB - 1 minor injury. AAIB AARF investigation. |
| R44 | 08 May 2005 | |
| Aircraft entered uncontrollable right yaw, struck ground and came to rest on its side. Substantial damage. No injuries to 3 POB. AAIB AARF investigation. |
| B206 | 05 Apr 2004 | |
| Aircraft entered right yaw and spiralled down to heavy ground impact. Substantial damage. 3 POB, 1 serious and 2 minor injuries. Investigation by Irish AAIU. |
| B206 | 30 May 2003 | |
| Aircraft began to yaw right and rotate before striking ground at low speed and rolling onto side. Aircraft destroyed. Minor injuries to 3 POB. AAIB Field investigation. |
| Gazelle | 14 Jul 2002 | |
| Loss of control on take-off. Main rotor struck ground. Aircraft destroyed. No injury to 4 POB. AAIB AARF investigation. |
| Gazelle | 03 Sep 2001 | |
| Aircraft entered uncontrollable turn and crashed. Substantial damage. No injury to 1 POB. AAIB AARF investigation. |
| AS341 | 28 Jul 1997 | |
| A/c began to rotate after lift off & tail struck hangar door. A fire ensued & a/c was destroyed. 2 POB seriously injured. |
| AS341 | 05 Jul 1997 | |
| Heavy landing, airframe distorted. No injury to 4 POB. |
| 10 |
| 0 |
A Graph of These Accidents By Model+/-
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AS341 |
2
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0
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B2 |
1
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0
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B206 |
3
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0
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Gazelle |
2
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0
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R44 |
2
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0
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