Military helicopter tail rotor failure?

Question

Many thanks to all the responses to my previous posts. I have a followup question or two for engineers or helicopter buffs.
Would a small jet engine, mounted horizontally and suitably armored, in the tail provide enough thrust, be throttleable and be available to power up to full throttle in a matter of seconds to offset LTR. I've seen small jets offered by various companies for models that produce around 100 pounds of thrust and weigh only around 30-35 pounds. You could incorporate existing fuel lines from the main engine to run them and develop a system of control that is either determined by existing pedal inputs or a backup system of hand control or computerized input in conjunction with a gyroscopic mechanism as found on the wheeled single-person transport of the Segway and others. It appears that most LTR situations offer a measure of warning for a pilot to initiate the backup system. All responses welcome and thanks again.

I'm also wondering if a system has been investigated or could be developed using a counter-rotating mass in the tailboom or under the engine to offset the main rotor torque---somewhat akin to a gyroscope. Still working on the physics.

An article on civilian tail rotor failures--
http://the.honoluluadvertiser.com/article/2007/Mar/14/ln/FP703140414.html
Some were simply caused by foreign objects from the cabin getting wrapped up in the rotor.

I'm looking into other systems besides NOTAR. My design theory of a jet propulsion would not add any appreciable weight to the tail...perhaps a hundred pounds and could in fact eliminate the tail rotor if response parameters can be met.

Answer 1

Too heavy, too complex. There are several small helicopters currently being made and tested using NOTAR (no tail rotor) designs. They use some of the exhaust coming off the engine, run it down the boom and out adjustable exhaust vents at the tail. Several designs work and it is only a matter of time before they become wide spread on smaller helos.

Some of the problems of a separate jet engine in the tail, weight, cost, vulnerability of the engine and the fuel supply to even small arms fire. I don't think I would like to have a source of ignition in my tail.

A tail rotor as used in the vast majority of helicopters has one big thing going for it. It works. It is very responsive to pilot input with immediate change of thrust requirements. LTR out of the blue is very rare. In combat aircraft, they have to usually take a real licking before they go out.

Answer 2

Anything is possible but anything you add to a military helicopter adds weight which means decreased performance or less capability; adding weight in the tail means you either change point of balance and handling chracteristics or add weight to the front to maintin point of balance which would further degrade performance or capibility. Actually have been some very safe designs and concepts but they also have to fullfill te mission in the real world, if it can't carry anything or shoot anything is serves no real purpose for the military.

Answer 3

Consider the costs versus the benefits. You're talking about a huge increase in cost and complexity to POSSIBLY mitigate a situation that is exceedingly rare. It just doesn't make sense.