Fw-189 Prop Spinner Question

Matt308 · Mar 18, 2013

What purpose does the finned prop spinner in this picture serve?

tyrodtom · Mar 18, 2013

That windmills in the wind a provides power for the varible pitch propeller, instead of using electricity or hydraulics.

Matt308 · Mar 18, 2013

Interesting! Thanks. I never noticed it before. Must not be on all variants. Off I go to dig around. :thumbup:

nuuumannn · Mar 18, 2013

Yep, the Fw 189's props were Argus built, as was its engines. The same was fitted to the Siebel Si 204. The Argus props were controllable pitch, but not constant speed, meaning the pilot controlled the pitch change, or it was done by aerodynamic forces and not a C/S governor.

What follows is purely guesswork, since I've never seen the mechanism of one of these, but I'm assuming the turning vanes would mechanically counter-balance aerodynamic loading on the prop blades. When you increase the power levers, the forces want to decrease blade angle, but the turning vanes would counter this to enable the blade angle to increase or not change, depending on the setting the pilot selects. The vanes would act in the opposite as when the power is brought back, the decrease in rpm wants to increase the angle, but the rotating vanes would counter it. I think this is right; other controllable pitch props work in a similar way using counter-weights to counteract aerodynamic loading.

tyrodtom · Mar 18, 2013

I just noticed the radar antenna on that Fw189, what was it used against ? Night Witches ?

nuuumannn · Mar 18, 2013

Yep, night fighter variants were used by 1/NJG 100 - the Eisenbahn Nachtjagd for defending railways lines against Russian Polikarpov U-2s. Note also the schragemusik gun installation. That aircraft hasn't been run in awhile or those guys wouldn't be holding the exhaust like that...

bobbysocks · Mar 19, 2013

only a 2 blade prop??

Snautzer01 · Mar 27, 2013

tyrodtom said:
That windmills in the wind a provides power for the varible pitch propeller, instead of using electricity or hydraulics.

no not quite. Argus works with hydraulics. A flywheel driven by the engine influence oil pressure in the control box. Pressure moves a rod which mechanicly governs the prop.

Snautzer01 · Mar 27, 2013

nuuumannn said:
What follows is purely guesswork, since I've never seen the mechanism of one of these,

Adjusting the propeller wing is done by measuring the difference in speed of nabe and the ribspinner. The ribspinner goes opposite the nabe because of obliqueness of the spinner ribs

Snautzer01 · Mar 27, 2013

bobbysocks said:
only a 2 blade prop??

yes. it was desigded for two bladed prop.

stona · Mar 27, 2013

nuuumannn said:
Yep, night fighter variants were used by 1/NJG 100 - the Eisenbahn Nachtjagd for defending railways lines against Russian Polikarpov U-2s. Note also the schragemusik gun installation. That aircraft hasn't been run in awhile or those guys wouldn't be holding the exhaust like that...

Exactly so. The antenna is for a FuG212C-1 radar. The "schrage musik" installation is probably a single MG 151/20. The aircraft is a modified A-1 and these aircraft were designated "Behelfsnachtjager" or auxiliary night fighters.
They were not capable of catching,let alone shooting down,bombers in the west. They could manage a little over 200mph before the addition of the radar antenna,fine for reconnaissance but not for an interceptor!

I think the original posted image may be colourised as I first saw a black and white version of it many,many years ago.

Cheers

Steve

Matt308 · Mar 27, 2013

Great information guys. Thanks.

nuuumannn · Mar 27, 2013

Great info Snautzer and great to see the illustration.

A flywheel driven by the engine influence oil pressure in the control box. Pressure moves a rod which mechanicly governs the prop.

So, looking at the drawing, the actuation of the variable pitch is done electrically by the switch at right, which sends a signal to the (governor boost?) oil pump and a solenoid switch attached to the governor (the big box below the prop) or it could be a complete PCU (Prop Control Unit) with governor attached (that's the governor with the wee arms attached at the centre of the box - the fly wheel) - the actuators above it in the drawing could be power levers - just guessing.

Engine oil from the governor at boost (governor boost pump?) pressure acts via a distributor valve against the mechanism in the hub, which mechanically decreases the blade angle when the pilot increases the power levers. The spinner at front counter balances aerodynamic forces against the blades (as I guessed in my earlier post) in the same vein as counter weights, which assists in actuating them. Decreased oil pressure via the governor and aerodynamic forces via that spinner actuate the prop in the opposite direction when the power levers are pulled back. The illustration is a little too small and my German isn't that hot, but that, I think is the gist of it.