Originally Posted by
MistWolf
PISTONS
A piston does not have to move to be a piston. It can be stationary in relationship to the machinery it's attached to. Some aircraft use hydraulics where it's the cylinder portion that moves causing the control surface, landing gear, doors etc. to move, while the piston part is affixed to the airframe or accessory
I don't post this to explain things to you, Hans as you've proven you will continue to interpret the facts as you will and will continue to argue against what knowledgeable, trained and experienced people have to say. I post this for others who slog their way through this post.
SEMANTICS
Technicians know it's not semantics, it's proper nomenclature to correctly identify the problem so job can get done properly and safely. It's not semantics when 400 lives are riding through a cold, harsh environment at 30,000 feet traveling at 600 knots. It's not semantics when a fighter is popping chaff and flare as it dives it's way to deliver ordinance on an enemy position that has our troops pinned down and cutting them to pieces. It's not sementics when the FAA is combing through the maintenance books and looking at your practices when a pilot balls up an aircraft you just worked on, out in some remote location.
Let's bring it home- Warfighter brings in AR and says "It's double feeding." Armorer hands Warfighter a new mag. "This'll fix it." Warfighter goes out and gets in a fight and the same malfunction occurs. Warfighter clears malfunction while under fire, cursing the armorer the whole time.
When the Warfighter gets back, he tears into the Armorer. "You said a new mag would fix the double feed problem!" Armorer says "It does. Were two live rounds in the chamber?"
"No! It was a double feed! An empty and a live round were jammed in there, just like all the other times."
"Ah," says the Armorer. "That's not a double feed. That's something different."
"Semantics! Two rounds were stuck in there!"
Well, guess what? In this case, "semantics" almost got your ass shot off. Dismissing the proper use of words as "semantics" muddies communications. If we're lucky, it merely wastes time and money. If we're not, it can lead to fines and imprisonment and loss of life and expensive equipment
DEFINING DIRECT IMPINGEMENT
I have not found enough information to use to clearly define "Direct Impingment", so I have not attempted to do so. I have not yet had the time to study the DI system to attempt to define it on my own, as I have with the AR system. So I will leave you with this-
The DI System is like pornography. I cannot clearly define it, but I know it when I see it
Basically, all DI system have a cup or pin that is external to the carrier that the gas tube directs gas pressure to in order to activate the carrier with a push. If the cup/pin is considered the piston and the gas tube the cylinder, a feature common to all DI systems is that when the carrier begins movement, the piston separates from the cylinder.
In the AR, the gas tube is not a cylinder and the piston is internal meaning it remains with the cylinder and the piston & cylinder. The gas tube is actually a capillary tube that controls flow from a high pressure vessel to a low pressure vessel. That means the gas flowing from the gas tube drops in pressure as it enters the expansion chamber