I wanted to try and summarize these weird ideas on loss of T/R I've posted, and relate them to what I think is the current state of dealing with the loss of T/R in the helo industry. My opinion is that dealing with the loss of T/R thrust is not nearly as well developed as it can be, and this poses some safety problems.
In the Penny Farthing helo configuration, we all know that the loss of T/R thrust is a significant failure that no pilot wants to face, but all pilots should be prepared for. For this discussion I'll focus mainly on total loss of T/R thrust and exclude jammed pedals, stuck cables, etc, and those failures with CG changes.
There are 3 basic methods of responding to this failure, which deals with the loss of the anti-torque required for directional control of a Penny Farthing helo.
Method 1 Reduce the Main Rotor torque to zero. This is the "reduce the collective, chop the throttle and autorotate to a landing" method. It is the method of choice for failure in the hover, and for inexperienced pilots. This is taught by all flight instructors to new pilots, and all new pilots learn autorotative techniques in training.
Pros: Stops the airframe from experiencing severe yawing. Relies on the autorotative ablility of the airframe for a "safe" landing. All pilots have a degree of training in autorotation. Most simple recovery technique.
Cons:Technique varies by airframe type. Not all airframes are created equal in autorotative landing ability. The choice of landing area is severely restricted.
Method 2 Low to mid range Main Rotor torque method. This is the run-on landing method where forward flight with a controlled descent rate at sufficient airspeed provides enough anti-torque for directional control, to allow a run-on landing in either grass or on concrete.
There seems to be a lot a gray area in this method. Not all airframes are well suited to this method. Not all pilots are trained in this method. This method also generally requires a lot of skill from the pilot (Nick Lappos spoke eloquently on this in his earlier post). This method is generally not well developed (with certain exceptions), in either airframe capability or in pilot training.
Pros: The pilot has much greater choice of landing areas. The airframe usually suffers far less damage upon landing.
Cons: Requires a lot of pilot skill to accomplish. Can only be used when some altitude is present at failure. Not all helos are well suited to this method. Not all pilots are capable of this method. Maintaining altitude (or a slight climb) may only be possible with significant forward airspeed, and only in certain airframes.
Method 3 High Main Rotor torque method. This is the climb out from either low speed or a hover method. This method is used to climb out of a bad landing area at low altitude, so a transition to method 2 can be made. This is the method GulfPLt used in the event of his earlier post.
This method is not well understood at all, and presents considerable dangers. Anecdotal evidence suggests that this method does work at times, but accident investigations show that it often does not work.
There is usually not enough alternative anti-torque available with this method to prevent spinning of the airframe, as spinning of the airframe is considered quite dangerous in a helo.
Pros: Can prevent a forced landing in an inhospitable area during a low altitude failure.
Cons: Requires great skill from the pilot. Requires an airframe, avionics, engines, fuel system, etc, that can tolerate a high torque induced flat spin. Persons can be thrown out of the airframe while spinning if not belted in. (Added in edit) A pilot can become disoriented in a spin. Structural failure of the airframe could occur in a spin. Collision with an obstacle might occur in the spin.
Conclusion
I guess my final conclusion is that not enough has been done to help helo pilots deal with the issue of loss of T/R. Most new or low time pilots are at a loss as to what do if a loss of T/R event occures except to use Method 1 discribed above, and the results of this method are not always satisfactory. Method 2 is highly useful in certain circumstances, but many pilots are not trained for it, and some airframes are not built to use this method without making great demands on the skills of the pilots.
Method 3 does have some merits in my opinion, but the demands on both pilot and airframe are even greater than in method 2. When I posted some of the ideas previously, it was an attempt to think of ways to better improve the ability of all pilots (through airframe improvements) to perfrom a satisfactory recovery from a loss of T/R event. I also don't understand several things related to method 3. Why does a spinning airframe HAVE to be dangerous (apart from not being belted in, and poor directional control near obstacles). FW pilots practice spin recovery all the time. But as GulfPLt pointed out in his post, he had no training in how to recover a helo from a spin. Why are pilots not trained for this? Are there methods to prevent (or at least limit) the pilot disorientation of a spin? Is there any aero-medical research on this?
Reading the other thread referred to by "The Nr Fairy" demonstrates just how daunting this event is to nearly all helo pilots, and it's my opinion that more can done to improve both helo airframes and a pilot's training to help a pilot get through a loss of T/R event safely.
To vfrpilotpb, I took the word "some" out of the text, as you are correct.
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Safe flying to you...
[This message has been edited by Flight Safety (edited 02 July 2001).]