Twin or Single

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carmoda

Twin or Single

Postby carmoda » Fri Aug 31, 2018 10:25 am

Hi,

IS there a rule of thumb for choosing a twin over a single for water crossings? I plan to fly over 200klm (144mi) stretch of sea roughly 6-12 times a year. I am considering a DA40NG over a DA42-V1.
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Re: Twin or Single

Postby jb642DA » Fri Aug 31, 2018 1:21 pm

This is an interesting topic. I'm not aware of a "rule of thumb", but there are many personal "opinions".......

Mine is - I'd rather get to "dry land" and LAND versus put down in water.

What "kind" of water are you talking about? By the distance you mentioned, I'm guessing "BIG" water.
If you have to land in water due to an engine failure, think about "sea state" and water temperature.
Here's some info on:
"Sea State" - https://www.skybrary.aero/index.php/Sea_State
"Ditching" - https://www.skybrary.aero/index.php/Dit ... g_Aircraft
"Evacuation on water" - https://www.skybrary.aero/index.php/Eme ... n_on_Water

Once during my flying career, I spent 2 1/2 hours over the North Atlantic, with one engine inop (high pressure oil return line broke) in a twin engine plane. Sea state was 20-30 foot waves and water temp 34 deg F ("nasty" sea state day,my non-technical term!).

I was very glad I had a "spare" engine that day! Even though I had an "exposure suit" on and raft with me, surviving 1 hour in that sea state would be very questionable, to say the least!
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Re: Twin or Single

Postby TimS » Fri Aug 31, 2018 1:25 pm

Ferry pilots on really long over water flights prefer single engine, because most twins when you lose an engine lose range.
Since they often need ferry tanks, losing an engine in a twin often means you are not making land.
So you need more info, besides the 144 mile water crossing.

Tim
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Re: Twin or Single

Postby jb642DA » Fri Aug 31, 2018 1:28 pm

TimS wrote:Ferry pilots on really long over water flights prefer single engine, because most twins when you lose an engine lose range.
Since they often need ferry tanks, losing an engine in a twin often means you are not making land.
So you need more info, besides the 144 mile water crossing.

Tim


"prefer single engine" - that's interesting!! What kind of planes do these "ferry pilots" you mention usually fly?

(carmoda - I told you this will be an interesting topic!)
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Re: Twin or Single

Postby TimS » Fri Aug 31, 2018 2:39 pm

Any piston plane being moved overseas. Such as Barons and Bonanza going to Australia, sometimes south America...
I want to one day fly around the world, so I started reading blogs and discussions by ferry pilots for a few years.
I have come to the conclusion: I need burn Jet-A, and I will take my time and do it over a year or two and see the world.

Tim
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Re: Twin or Single

Postby Rich » Fri Aug 31, 2018 2:43 pm

Most singles also kind of lose range when the engine fails :scratch:

There's a difference between losing an engine in a twin over the middle of the Atlantic Ocean and merely 100 NM from shore.

From what sketchy evidence I can find, of all Diamond variants, the NG would seem to be the leader in power failures.
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Re: Twin or Single

Postby TimS » Fri Aug 31, 2018 3:02 pm

Rich wrote:Most singles also kind of lose range when the engine fails :scratch:

There's a difference between losing an engine in a twin over the middle of the Atlantic Ocean and merely 100 NM from shore.

From what sketchy evidence I can find, of all Diamond variants, the NG would seem to be the leader in power failures.


If you fly the northern route across the Atlantic; there are many sections where you are 750 miles between stops, but only over the ocean for a hundred or so. There is effectively no place to land in between. Many twins lose range when you lose an engine. I recall one guy who said the Baron loses so much range when you lose an engine, that along the northern route to Europe, you only get the benefit of the second engine for the first 25% of many legs (headwinds when you turn back give you a big hit on range) and the last hundred miles assuming no alternate. Therefore, the vast majority of the trip, the Baron doubles the chance of engine failure, but does not help you get to a safe landing location, and you also crash with more energy.

Part of the reason I like the DA-42 with extended range tanks, like the Aerostar I had before. They have the range, so there never is a single engine operation point on crossing the Atlantic or even the Pacific (if you go the really, really long way around) where one engine will not get you back to an airport.

Tim
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Re: Twin or Single

Postby YCCA » Fri Aug 31, 2018 5:25 pm

Is there really a debate as to what is a better option, single or twin, over open water? Like I always say, you can’t get a group of pilots to agree on what color the sky is!
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Re: Twin or Single

Postby YCCA » Fri Aug 31, 2018 5:40 pm

TimS wrote:
Rich wrote:Most singles also kind of lose range when the engine fails :scratch:

There's a difference between losing an engine in a twin over the middle of the Atlantic Ocean and merely 100 NM from shore.

From what sketchy evidence I can find, of all Diamond variants, the NG would seem to be the leader in power failures.


If you fly the northern route across the Atlantic; there are many sections where you are 750 miles between stops, but only over the ocean for a hundred or so. There is effectively no place to land in between. Many twins lose range when you lose an engine. I recall one guy who said the Baron loses so much range when you lose an engine, that along the northern route to Europe, you only get the benefit of the second engine for the first 25% of many legs (headwinds when you turn back give you a big hit on range) and the last hundred miles assuming no alternate. Therefore, the vast majority of the trip, the Baron doubles the chance of engine failure, but does not help you get to a safe landing location, and you also crash with more energy.

Part of the reason I like the DA-42 with extended range tanks, like the Aerostar I had before. They have the range, so there never is a single engine operation point on crossing the Atlantic or even the Pacific (if you go the really, really long way around) where one engine will not get you back to an airport.

Tim


Whatever range you lose is still going to get you closer to land, or a boat, or some sort of rescue, then becoming an instant glider pilot. And ditching with power on is a far preferred method then power off.. you can arrest your descent rate or climb and try to get better positioning with respect to the swells.. Not so much in a single engine
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Re: Twin or Single

Postby jb642DA » Fri Aug 31, 2018 9:06 pm

YCCA wrote:Is there really a debate as to what is a better option, single or twin, over open water? Like I always say, you can’t get a group of pilots to agree on what color the sky is!


If the question was "yes" or "no", you'd still get 4 or more "opinions"!

I'll take 2 (or more?) engines over "water" any day!
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