ElpinDAB
Topic Author
Posts: 442
Joined: Sun Apr 17, 2005 7:00 am

Starting A Multi Engine Seaplane

Fri Nov 17, 2006 8:17 am

Hey

I remember back when I got my seaplane rating, one of the most interesting things is that the second the engine turns over after you start it, you are moving along the water, even at idle power. Because of that, I've always wondered what the procedure is to start a multi engine seaplane. Does it have to be done on land, or can it be accomplished in the water also without undesirable results? (I guess I can't really think of any multi engine seaplanes that aren't amphibs...)

thanks.
 
WrenchBender
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Joined: Wed Feb 04, 2004 5:59 am

RE: Starting A Multi Engine Seaplane

Fri Nov 17, 2006 8:56 am

The Twotter with the 12000 series floats is not an amphib, but part of the conversion was rigging the props with 'zero thrust latches' and setting up the throttles for that setting.
Therefore when you start, the props do not generate any thrust. The downside is they take forever to coast down on shutdown.

Notice that the props are at a 'flat setting'.

WrenchBender
Silly Pilot, Tricks are for kids.......
 
SlamClick
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RE: Starting A Multi Engine Seaplane

Fri Nov 17, 2006 9:08 am

I've pondered the same problem with a helicopter on floats.

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The old problem of Newton's 3rd law and the tail rotor not yet developing enough thrust to counteract the torque on the main rotor as it winds up or down.
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113312
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RE: Starting A Multi Engine Seaplane

Fri Nov 17, 2006 5:35 pm

I remember spending hours watching Grumman Gooses operating from a floating dock at Catalina Island during the 1960's. Since the boarding door was on the left side, they started the right engine first and allowed the plane to move forward until it was clear of the dock and personnel. Then they started the left engine.
 
BAE146QT
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RE: Starting A Multi Engine Seaplane

Fri Nov 17, 2006 6:20 pm

Quoting 113313:
Since the boarding door was on the left side, they started the right engine first and allowed the plane to move forward until it was clear of the dock and personnel.

I'm trying to picture this. The asymmetric thrust from the right motor would tend to push it into the dock, I should think.

A quick peek at some pics seems to show that the Goose does not have little water rudders, (a-la the Cessna amphibious Caravan), and I can't imagine that the control surfaces have any sort of authority at low speed, any more than they would on any other aircraft.

Or did the floating dock come from *behind* the aircraft and stop at the door, IYSWIM? Bogus ASCII graphic below;


[] + <- Airplane here, facing up the page.
[]
[]
[]

This would mean it could move left as much as it wanted, I guess.
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DC8FriendShip
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Joined: Fri Apr 29, 2005 7:35 pm

RE: Starting A Multi Engine Seaplane

Sun Nov 19, 2006 5:54 am

The other method is you could start the engines with props in feather ala PT-6's and move the props out of feather when it's time to move the plane.
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Fly2HMO
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Joined: Sat Jan 24, 2004 12:14 pm

RE: Starting A Multi Engine Seaplane

Wed Nov 22, 2006 11:46 am

Quoting WrenchBender (Reply 1):
'zero thrust latches'

Would that be the same as discing?
 
WrenchBender
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Joined: Wed Feb 04, 2004 5:59 am

RE: Starting A Multi Engine Seaplane

Thu Nov 23, 2006 8:42 am

Quoting FLY2HMO (Reply 6):
Would that be the same as discing?

Yes, they are just a physical lock at the discing pitch setting. Spring loaded in, centrifigal force out.

WrenchBender
Silly Pilot, Tricks are for kids.......

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