enginehistory.org

[jjuutinen]

In the latest Reno article Graham White writes how the HamStan prop goes to low pitch position in case on oil pressure failure while Aeroproducts prop doesn´t. Interestingly, both German major designs, Junkers VS and VDM, have "pitch locks", i.e. if the connection between the engine and prop is lost, they remain at the last selected pitch. Note that the VS design is hydraulic, but very different from HamStan. It has a gear type hydraulic motor inside the hub which powers worm gears that rotate the blades.

[jschauer]

Just a note about the Ham Std. props, the later versions that were self contained, they also had a pitch-lock system. We had them on the C-130s and the KC-97s. With the pitch lock system, if there was any oil (hydraulic fluid) pressure available it would tend to increase the pitch before locking up again. One of the emergency procedures was to intermittantly hit the feather button to try and force the higher feathering oil pressure into the prop dome to increase the pitch, lowering the rpm. That procedure was used only if you needed that engine's power. I had an overspeed to 106% one time on a C-130, boy did that make a weird noise in the cockpit! All the little access panels started to vibrate and hum, it got your attention real quick. We were able to feather it OK. Funny thing about shutting engines down, in my 13 years of flying C-130s, I had to shut down an engine about 10 times, eight were due to propeller problems.

[jschauer]

One more thing about the Ham. Std. self contained props, All the engine shutdowns I did were due to the valve body failing, i.e. pump failure, internal leaks, external leaks, etc. The propeller itself never failed.

[jrussell]

I have access to a VDM propellor / hub assy off a Me-109 G-10, and was amazed to find out that I could rotate the pitch change pinion gear very easily with my fingers. To rotate those large blades so easily was astonishing. Does a Curtiss Electric prop change pitch with so little friction? How about a Ham Standard?
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It runs best just before it blows!

[jschauer]

Not with a Ham. Std.

[jjuutinen]

Schauer, did you refer to Hamilton Super Hydromatic?

[jschauer]

I don't know what a Ham. Super Hydromatic is. I'm somewhat familiar with the Ham. Std. that were/are installed on KC-97s and C-130s if that's what a Super Hydromatic is. Those are the self-contained props that have the valve body, pumps, hydraulic fluid resevoir, governor, all in a housing that slides over the prop shaft before installing the prop next. It is operated with MIL-O-5606 hydraulic fluid instead of engine oil. You could reservice the resevoir on the 97 in flight with engine oil in an emergency. We used a prop paddle that you would slip over the end of the blades to twist the blades when assembling them before putting on the dome assemblely, it was about three feet long for leverage. Once the dome was installed you could not twist the blades.

[jjuutinen]

I believe thje Super Hydromatic was being offered at the end of the war, but apparently it did not gain acceptance. One book on the Kaiser Fleetwings carreir attack aircraft mentions some critique on the SupHyd.