I am a maintenace engineer on a type course for the Dash 8 100/200/300, with the associated Pratt engines (PW 120/121/120a ect) My background is CRJ's so I dont have a lot of experiance with the propeller systems. Anyway why when you start up do you put the propeller into full feather? This dosn't make any sense to me. It would make more sense to start the prop in disc mode, thus you don't load up the hubs, the gear box and other associated mechanisims. You also dont have to change the pitch while you are doing our runs, if your in full feather to change the pitch you have to go through the range of prop angle that produces thrust and gives you a potential break away situation. Anyone know why?
2007-03-14 06:43:31 · 5 answers · asked by Anonymous in Cars & Transportation ➔ Aircraft
Dude....thats a way to complicated question, you are way better off googling whatever company it is that makes whatever it is you are talking about and call a number on their website.
2007-03-14 07:34:02 · answer #1 · answered by thereha 3 · 0⤊ 4⤋
Most P & W engines are free shaft turbines. The starter does not have to turn the props when starting and the prop unfeathers and begins to turn as the engine spools up. Every turbo prop engine you see that goes to full feather when stopped is a free shaft turbine. If you grab the prop and turn it by hand, only the prop and shaft turn. When you see one that goes flat when off, it is not a free shaft turbine and the starter must turn the prop when starting. If you turn the prop by hand all rotatables in the engine turn with it. A good example of this is the Garrett (some other company makes them now) found on Merlins and Twin Commanders.
2007-03-14 20:22:47 · answer #2 · answered by eferrell01 7 · 1⤊ 0⤋
Eferrel is exactly right. There is no strain on the starter from the gearbox or propeller on a free shaft turbine. The blades feather when there is no oil pressure as a safety point.
2007-03-15 08:56:41 · answer #3 · answered by txpilot 3 · 0⤊ 0⤋
To shut the engine down you select full feather so that the blades will come to a stop quickly. To come out of full feather requires hydraulic pressure, (unless you have de-feathering pumps installed) You don't have hydraulic pressure until the engine starts...
2007-03-14 16:25:16 · answer #4 · answered by Gordon B 4 · 1⤊ 1⤋
very low thrust in feather
lower np/nh in feather
some unfeather in GI in icy conditions, but that can cause its own issues
2014-09-23 17:04:33 · answer #5 · answered by Mr 1 · 1⤊ 0⤋