Hello. I am an engineer with General Electric Power Systems. I work with Aero and Aero Derivative power plants every day (except most weekends). I konw a thing or two about this stuff, so I hope I can help.
First, you are absolutly right, kind of. When the pilot pulls back the throttle to decellerate from, say 400 kts to 250 in order to initiate a decent, you, the passenger, will notice a "breaking" feeling. What is happening are two things. First, the thrust from the engines go away. Second, drag takes over and pulls the jet slower. This is a simplistic explanation, but it will work.
Those big engines are very good at producing drag. Very good. Basically it's like holding a large billboard out in the airstream. The fan is driven by a free turbine, that is, a turbine that is not physically connected to the gas generator, or jet engine. The jet engine is inside the whole assembly. It's real purpose is to generate large amounts of gas to drive the multiple turbines that turn the fan. When you stop producing gas to turn the big fan, the fan will no longer produce thrust and instead generate tremendous drag. While it is true that the gas generator portion of the engine has various bleeds that will keep everything a-okay inside the GG
, the air coming in will push hard against the blades of the fan and go through it and exit out the rear. Because the GG
is still producing thrust, and the rotating mass of the LPT and fan are dripping with momentum, these effects are limited by the throttle setting. There is not "anti-torque", just loads of drag. Kind of...
Okay, that explanation wasn't very good.
As far as your turboprop deal, this is only true if the pilot sets a flat blade pitch on the propeller. If you feather the prop, it will produce very little drag. The pitch of a prop has the sole purpose of dictating what speed a particular aircraft will travel at a certain throttle setting. When you have the prop set for high cruise and suddenly flatten it out, the prop is suddently in a configuration of a slower speed, and will try very hard to bring the PT
's RPMs up to match the airpseed. The resultant is drag, drag, drag, and drag. Maybe a grenaded PT
Hope that helps. Probably not...