Points all well taken Forestoke but the problem with all these things is when attempted to be used in the training evironment and particularly when being used by someone attempting to bypass the need altogether for training then they indeed are a crutch and even worse a severe liability.

The real danger is the implication that they make teaching oneself to fly easier which is quite the opposite. Every single one of them require extensive setup and fine tuning of the various gains which means more than just a few flights with even competant pilots forced to deal with a poor flying airplane. Now do you think this loner somewhere depending on this crutch is ever going to get this thing fine tuned before taking off by himself to teach himself, very unlikely and it is only going to hasten the demise of the airplane with the self teaching individual totally befuddled.

I think you will find in the cases where a competant instructor who attempts to use the devices soon realizes that the wasted time in finetuning of the devices to make them usable just never happens and they only serve as hindrance even in the dual instruction situation. They will increase the learning curve in every type of learning environment increasing the total time spent before any student reachs any given level of competant skills. In short they are a liability in the learning environment.

John