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carmoda

Flying over water - Twin/Single Distance

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Hi,

 

another noob question. I am aware that twin engines are 'generally' considered safer for flying over water. Is there a rule of thumb for how far hours/klm?

 

 

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Many twins WILL fly on one engine, so if you fly one of those you have engine out redundancy . but then YOU are on one engine and sometimes THAT engine will be stressed so more likely to fail if you want to take the analysis that far. On a single, obviously you can just glide till can't glide any further if an engine fails. This will be around 11x your altitude on average plus/ minus wind component so height (altitude) is an advantage if you are trying to range to land forms. A safe landing may not be assured on some rocky outcrop.These considerations apply and there is no simple rule of thumb for the comparo that I've ever heard of. Twin Jets now go everywhere where they used to have 3 or 4 engines. Jet engine reliability is probably 100 times better than pistons and the second engine will run reliably at high power as long as temps are within the range. and you have fuel. Nev

 

 

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facthunter/Nev, great information to work with. cheers. I would be looking at modern twins that can hold altitude and remain stable on one engine. although there are so many points going against them. higher acquisition, operating costs, unsuitability for inexperienced pilots, much higher insurance premiums, unsuitability for unimproved airstrips - all make them less appealing than a good single.

 

 

  • Agree 1

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Turbo prop single seems to be the answer to that sector of the market.. Twins kill a lot of pilots who don't fly a lot. Not cheap though. as they are generally pressurized if they are economic. Nev

 

 

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Civil Aviation Regulation 258 is the underlying rule. Basically you must be within gliding distance at all times unless you can comply with various other regulations. One of which is CAO20.11 which deals with emergency equipment requirements.

 

Keep in mind that “Land” is referring to a suitable landing area. You can’t use a rock for,action off the coast as “Land”.

 

 

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On a basic twin piston, say six seat, you must look also at PNR (specifically over water) - ( point of no return} and look at fuel available in case of engine failure at that point, as you usually will have descend if flying high, and have the good engine at near 100%. Speed drops and one of your legs will get very tired holding in a lot of rudder in.

 

 

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A twin should have rudder trim if it's worthy of the name. As you slow up your rudder is less effective at high power and at VMC(a) and below you won't have enough rudder at full power to stop it turning towards the dead engine. IF that happens lower the nose and reduce power on the good engine to avoid loss of control and get above VMC(a) and stay there till the landing flare unless you are very high and will definitely not need much power. to get in at any stage of the approach.. Nev

 

 

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A twin should have rudder trim if it's worthy of the name. As you slow up your rudder is less effective at high power and at VMC(a) and below you won't have enough rudder at full power to stop it turning towards the dead engine. IF that happens lower the nose and reduce power on the good engine to avoid loss of control and get above VMC(a) and stay there till the landing flare unless you are very high and will definitely not need much power. to get in at any stage of the approach.. Nev

Really Nev. Did not know that!

 

 

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Pretty big load at times. The planes must be designed to not require more than 200 LBS of foot pressure... You can't hold that for long so you trim out most or all of the pressure. If you change the power it alters each time as it does with speed change. You may choose to not fully trim with these small. alterations. and just apply rudder pressure...You usually centre it when on late final so it doesn't wreck your landing when you close the throttle on the good engine. There's a dial and pointer to show how much trim is on.. You get to use a very active rudder when flying assy. Nev

 

 

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