Definitions - LTE
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Definitions - LTE
Is there a big problem with definitions of terms in helicopter pilotage?
There seem to be different phenomena in people's minds which are labelled LTE.
As a result people talk at crossed purposes and the wrong advice is given and efficient solutions are not discussed or missed.
I propose a series of posts labelled:
Definitions - LTE
Definitions - Autoroation (ie. just a state of flight, not EOL and not an emergency and not requiring rapid control changes / entry etc)
Definitions - Vortex Ring State (Fully developed - recoverable? - calm and stable?)
Definitions - Settling with Power (US definition - Vortex Ring but covers insuffiecient power on transition to hover (OGE)?)
Definitions - Translating Tendancy ... etc.
Definitions - Flapping
The aim being to reach coherant industry wide better/common understanding.....
Here's a stab at it:
LTE
Phenomenon 1
Lack of Tailrotor Effectiveness
Classically ment to indicate that the tail rotor provides insufficient thrust to counter the Torque of main rotor drive at Low (Zero) Airspeed (hover) - generally by (inadequate) design. Often found in old fashioned helicopters. This will lead to a rate of yaw which will continue unless the power (M/R torque) is reduced.
Insufficient thrust may arise for a number of reasons:
The tail rotor is feeble in design.
The RPM is too low - Still high torque to M/R but insufficient counter-torque.
High Altitude - ineffective T/R
Excess power applied to M/R - more than permitted.
Dirty T/R - temporary interferance with the efficiency of T/R (ice, dirt, plastic bags etc.)
Phenomenon 2
Loss of Tailrotor Effectiveness
Normally transient;
M/R vortex interferance - generally at low Airspeed (often hover)
T/R vortex ring - with relative airflow opposing T/R outflow. - This can result in massive unpredictable Loss of T/R Thrust - and can be self-perpetuating.
Weather-cocking - T/R insufficiently powerful to overcome Vertical tail surfaces - when flying with Relative Airflow not on the nose - self correcting.
Often because the T/R does not have enought Thrust to maintain yaw at high lateral airspeeds.
Phenomenon 3
Lack of Tailrotor Education.
Frequent amongst inexperienced pilots. (eg R44 ENG in Australia, EC130 in USA, Gazelle in North of England)
Yaw changes (sometimes rapidly) when unexpected - (timid) corrective action fails and control is lost.
Failure often wrongly presumed - so innapropriate pilot response.
Often as a result of not appreciating the Relative Airflow direction (negative airflow - weathercocking).
Often triggered by Phenomenon 2
Either firm response is required to prevent it - or no response would generally be ok since the Helli will align itself with the Relative Airflow if permitted.
Phenomenon 4
Lack of Tail Rotor
Not really part of LTE - but it is ineffective in cases of failure of drive, control mechanism, limitted Pedal travel etc...
Any good? Any use? Helpfull? Wrong? Thoughts?
There seem to be different phenomena in people's minds which are labelled LTE.
As a result people talk at crossed purposes and the wrong advice is given and efficient solutions are not discussed or missed.
I propose a series of posts labelled:
Definitions - LTE
Definitions - Autoroation (ie. just a state of flight, not EOL and not an emergency and not requiring rapid control changes / entry etc)
Definitions - Vortex Ring State (Fully developed - recoverable? - calm and stable?)
Definitions - Settling with Power (US definition - Vortex Ring but covers insuffiecient power on transition to hover (OGE)?)
Definitions - Translating Tendancy ... etc.
Definitions - Flapping
The aim being to reach coherant industry wide better/common understanding.....
Here's a stab at it:
LTE
Phenomenon 1
Lack of Tailrotor Effectiveness
Classically ment to indicate that the tail rotor provides insufficient thrust to counter the Torque of main rotor drive at Low (Zero) Airspeed (hover) - generally by (inadequate) design. Often found in old fashioned helicopters. This will lead to a rate of yaw which will continue unless the power (M/R torque) is reduced.
Insufficient thrust may arise for a number of reasons:
The tail rotor is feeble in design.
The RPM is too low - Still high torque to M/R but insufficient counter-torque.
High Altitude - ineffective T/R
Excess power applied to M/R - more than permitted.
Dirty T/R - temporary interferance with the efficiency of T/R (ice, dirt, plastic bags etc.)
Phenomenon 2
Loss of Tailrotor Effectiveness
Normally transient;
M/R vortex interferance - generally at low Airspeed (often hover)
T/R vortex ring - with relative airflow opposing T/R outflow. - This can result in massive unpredictable Loss of T/R Thrust - and can be self-perpetuating.
Weather-cocking - T/R insufficiently powerful to overcome Vertical tail surfaces - when flying with Relative Airflow not on the nose - self correcting.
Often because the T/R does not have enought Thrust to maintain yaw at high lateral airspeeds.
Phenomenon 3
Lack of Tailrotor Education.
Frequent amongst inexperienced pilots. (eg R44 ENG in Australia, EC130 in USA, Gazelle in North of England)
Yaw changes (sometimes rapidly) when unexpected - (timid) corrective action fails and control is lost.
Failure often wrongly presumed - so innapropriate pilot response.
Often as a result of not appreciating the Relative Airflow direction (negative airflow - weathercocking).
Often triggered by Phenomenon 2
Either firm response is required to prevent it - or no response would generally be ok since the Helli will align itself with the Relative Airflow if permitted.
Phenomenon 4
Lack of Tail Rotor
Not really part of LTE - but it is ineffective in cases of failure of drive, control mechanism, limitted Pedal travel etc...
Any good? Any use? Helpfull? Wrong? Thoughts?
Last edited by AnFI; 3rd March 2011 at 16:21. Reason: change 3 to 4
Joined: Jan 2010
Posts: 4
Likes: 0
From: Los Angeles
Tail Rotor Education
Phenomenon 3 and Phenomenon 3 dont make sense to me
but maybe someone can explain the critical wind azimuth here really good coming from the good old B206 with the older tailrotor design.
I have an idea - but nowhere could i find a clear sense making explanation.
thanks h
but maybe someone can explain the critical wind azimuth here really good coming from the good old B206 with the older tailrotor design.
I have an idea - but nowhere could i find a clear sense making explanation.
thanks h
