Modern piston twins do not have unfeathering pumps, I believe they have accumulators which use stored air / oil pressure to drive the prop to fine pitch for airstarting. While this action was ongoing, you could see the blades twist from the cockpit. When it reached minimum low pitch, spring-loaded locks snapped out and held the blades there against the push of the feathering spring, after the pump stopped. The electric unfeathering pump moved oil into the prop dome and forced the piston forward (same way the governor does it) to drive the props out of feather into fine pitch. Old piston radial-engine multiengine aircraft, such as (e.g.) the Beech 18 and the DC-3 had unfeathering pumps to make it possible to unfeather for an airstart, or to restart the engine on the ground without the inconvenience of having a mechanic come out and use a big wooden paddle with a prop-fitting cuff on the end to apply the forces necessary to rotate the props out of feather and into the fine-pitch locks against the force of the feathering springs. An exception would be the case of unfeathering. When the engine's not running, no oil pressure - no movement. The cockpit prop control only moves a "speeder spring" on the prop governor. In my own operation, I always cut the engine first, then feathered, to minimize the noise and vibration which otherwise occurs, especially with a tailwind.I believe that some very old (20s-30s) birds with wooden blades and metal hubs (and possibly some ultralights) have direct-adjustable blades that you could see this action in response to cockpit control movement, but constant-speed props since the 1930s have had a governor that uses oil pressure to move the blades towards fine pitch - a feathering spring and airload provides the force that moves the blades towards coarse pitch and feather. Now I have seen, in the case of a PT6 with very slow self-feathering action (weak springs), where you could see the blades moving toward feather after the prop had stopped, but this is unusual - mostly because, by the checklist, the pilot will feather his engine before moving the condition lever to cutoff. The PT6 under discussion in this thread will (slowly) feather it's prop after engine shutdown (though pilots feather the engine during or before shutdown to prevent gearbox motion without lubrication), but it will be feathered before rotation stops, and it cannot be moved from the cockpit when stopped. This happens in FS where developers have made the effort, but does not reflect RW (real world) propellor action. It seems to me that all turbo engines should model this, right?Sorry, Don, but no. >when the engine was not running I could see the prop blades rotate when I moved the lever. But the whole idea of pushback for GA aircraft in the real world is pretty outr
At least, that's the way the Cajuns were doing it at Southern Seaplanes, 'bout 20 years ago!It's not in the backwoods that you need a tug (hopefully!), it's at the home base where the ground crew are dealing with many of these a day. Get the carts wheels jacked down, then dolly the whole shebang wherever it needed to go. The non-amphibs, I recall them scooting themselves out of the canal and up the railroad-tie ramp, where a little wheeled cart with hydraulic jacks could be run between the floats. DC-3s, for example, are too heavy to push! And the Beaver is no lightweight, either.Those twin bars are probably the solution for towing amphib floatplanes, too. I remember the Beech bars going back to 1968, and I'm sure there were similar solutions long before that. You either have two special-made bars going from the tug to each of the mains (Beech 18), which you tug from the front, or a special bar with adaptors for each of the several designs of tailwheels, and you tug from the back. >Pushback cart that would be able to pushback a Beaver (Float or fixed wheel) has yet to be invented :-) (tip: how would it be coupled to the "nose gear" ?As to specifically for the Beaver, I can't say, but generally speaking, taildragger airplanes are not a problem for a properly equipped tug to manage.
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