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  1. #61
    Join Date
    Dec 2004
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    4,262

    Default Re: Four motors, two props

    The Trollfjord sounds quite amazing! Thank you for posting this report about her engines. I have just googled her, but they only seem to have the basic info of interest to the average cruise passenger at http://www.cruisenorway.com/trollfjord.html

    And here is a bit more info about her at http://www.deltamarin.com/references...ry-trollfjord/

    While this link to info from her Classification Society give a wee bit more info about her propulsion systems :
    https://exchange.dnv.com/exchange/ma...vesselid=22927
    Here is a useful guide to Barbados - http://doyleguides.com/barbados.html

  2. #62
    john_morris_uk is online now Registered User
    Location : Home near Exeter, work in Hampshire, boat in Plymouth
    Join Date
    Jul 2002
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    11,506

    Default Re: Four motors, two props

    The latest RN Hydrographic ships have 'Azipods' for propulsion. Diesel generators provide electric for the electric motors in two pods which can rotate 360 degrees. Couple this with a bow thruster and a fancy computer and a joystick and you can walk the ship in any direction - or hold it stationary for bottom sampling etc.

    For close quarters work you can either set them both ahead and use them like a conventional twin drives in f'wd and astern, or set one fore and aft and the other athwartships and with the bowthruster put the ship anywhere at any angle by hand.
    [B][I]Wishing things away is not effective.[/I][/B]

  3. #63
    Join Date
    Aug 2006
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    5,986

    Default Re: Look at this fantastic piece of engineering and enjoy...

    Indeed. I am the survivor of an engine failure in a single-engined aircraft. It raised the pulse rate somewhat, but didn't hurt!


    But, to take this thread back off topic.....I believe that loss of a single engine - even in a 4 engine aircraft - can be very serious at a critical period. I remember talking to a 747 pilot some years ago, and was surprised to hear that loss of 1 engine at just the wrong moment on take-off was distinctly life threatening. Is this still the case with newer more powerful engines ? What happens on the newest big jets if they loose 1 of the 2 just as the wheels lift ?
    Usisafirie nyota ya mwenzio

  4. #64
    Join Date
    Mar 2006
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    179

    Default Re: Look at this fantastic piece of engineering and enjoy...

    Ah. Now I can speak with a bit of authority.
    All transport category aircraft can manage very well following the failure of a single engine, even elderly 747s. May be an increase in crew workload, but manageable.

    This means that a twin carries arround twice as much power as it really needs, and four engines has a third extra. Hence you can have some sporty takeoffs in twins.

    We had the family round yesterday, so I was unable to join in the spectacular thread drift, but here are a few notes.

    Aviaition people are quite open about safety statistics, so if you visit the AAIB and CAA sites you will see that many engine failures in light aircraft result in fatality (especially rotorcraft). But light aircraft are really analagous to sportsboats, not freighters or tankers

    I was interested to see that the large ship mentioned earlier is in effect multi engined, but I'm not sure whether all such vessels have this capability.

    Oh, and the thing that worries us most of all is common cause failures across all engines such as water/dirt in fuel, rain / hail ingestion , icing (did that get the Airspeed?)bird flock ingestion and the most common of all, pilot difficulties (as I get older I find it increasingly difficult to use the word error)

  5. #65
    Join Date
    Aug 2006
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    5,986

    Default Re: Look at this fantastic piece of engineering and enjoy...

    Thanks for that, i can relax more on take-off! Thinking more about the conversation I had, it might have been 15 years ago and we were talking about very high, very hot airports - eg Nairobi and Addis Ababa.

    Although, I wonder why Kenya Airways lost a brand new 737 on take off ? Bad fuel at Douala? I fly with them a lot and it makes one think!
    Usisafirie nyota ya mwenzio

  6. #66
    Anonymous Guest

    Default Re: Look at this fantastic piece of engineering and enjoy...

    [ QUOTE ]
    icing (did that get the Airspeed?)

    [/ QUOTE ]

    I was very young at the time but did discuss it with my father twenty years after the event. The AAIB did not conclude icing and I don't know what they did report. "Pilot error" was the usual in those days even if the wings had fallen off [img]/forums/images/graemlins/wink.gif[/img]

    I think that the Cheetah Xs (like many engines of that era) had comparatively cool carb heat which could push the carb right into the icing region and then was not hot enough to melt any ice - and as the exhaust manifold cools, all hope is lost. This is all well-known today but wasn't as well-understood back in those days.

    On finals into the field he had had the gear down then realised that the field was ploughed further down and had to pump the gear up manually at a few hundred feet. Must have been exciting!

  7. #67
    Join Date
    Mar 2005
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    684

    Default Re: Look at this fantastic piece of engineering and enjoy...

    Sorry if my "input" is a bit tardy, I've spent my weekend with a sanding block and a epoxy spreader.
    Actually with an engine like this you have multiple redundancy:

    I sailed on a ten-cylinder 900mm and a six-cylinder 900mm bore sulzer-engined ships.
    If you have a problem with a cylinder, it can be disconnected at the crosshead and the ship can continue until either a port is reached or, if possible, the problem solved.
    I saw this done once as a apprentice.

    Mike
    Missed my opinion? - No problem! - Someone elses will be along in a few minutes.

  8. #68
    gandy's Avatar
    gandy is offline Registered User
    Location : Aberdeenshire (quite far from the Solent)
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    Aug 2004
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    3,191

    Default Re: They don\'t all crash

    There was a 767 (I think) in Canada that did a glide from around 40,000' followed by a dead-stick landing on a disused airfield. They ran out of fuel following an imperial/metric screw up following a prior failure of some automatic fuel management systems.
    Tony S

  9. #69
    Join Date
    Mar 2005
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    684

    Default Re: Look at this fantastic piece of engineering and enjoy...

    The cams referred to are on the fuel pumps, they are timed to inject at the correct point on the cycle.

    Mike
    Missed my opinion? - No problem! - Someone elses will be along in a few minutes.

  10. #70
    Porthandbuoy's Avatar
    Porthandbuoy is offline Registered User
    Location : Firth of Clyde or Queensland.
    Join Date
    Apr 2003
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    2,675

    Default Re: Look at this fantastic piece of engineering and enjoy...

    And a 2-stroke, just like my Stuart Turner!
    www.backbearing.com. Astronavigation resources.

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