29 Mar 2024, 09:41 [ UTC - 5; DST ]
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Post subject: C421 converted to single PT6 Posted: Yesterday, 11:42 |
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Joined: 03/07/18 Posts: 75 Post Likes: +38 Location: Woburn, MA
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Saw this as I was looking at LinkedIn earlier from a flight test facility in Canada. I'm in a mixed bag of "well that's cool" and "but why?" but wanted to share in case someone had more insight into the project. A quick read through some comments and it looks like this has been an ongoing project for somebody over the past several years. If I understand this correctly, they've converted a 421 airframe into a SETP. https://www.linkedin.com/posts/lgraviat ... 48576-ciVGhttps://www.linkedin.com/posts/lgraviat ... 71488-tcAX
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 13:04 |
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Joined: 01/10/17 Posts: 1662 Post Likes: +1127 Company: Skyhaven Airport Inc
Aircraft: various mid century
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Tricky parts is the turbine is not supposed to switch fuel tanks. When O&N converted a couple 340s to twin Allison turbines they modified the aux tanks to continually refill the tips (mains) or the tips drain into the aux always I forget which it was. Then if you have locker tanks you can refill the tips but not feed directly from them like normal. The tricky part is tip tank Cessnas usually feed directly from the mains or aux tanks when selected.
Then there is the left right tank issue for a single turbine. Maybe header tank in the nose supplying the engine?
I wonder if the engine beam torque on the wing structure was figured into twisting moment during a High positive G event. Without the engines twisting the wing leading edge down is the spar strong enough?
Makes me wonder about the prop blade pulse frequency on the horizontal tail and the Conquest having dihedral horizontal tail vs the 421 does not. 441 having debonding issues of the tail also.
There are a lot of things to consider beyond bolting it on.
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 13:09 |
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Joined: 11/03/08 Posts: 14529 Post Likes: +22860 Location: Peachtree City GA / Stoke-On-Trent UK
Aircraft: A33
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there has also been a 340 converted to SETP. In fact, I have a notion (maybe misplaced) that a member here owns it, or owned it
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 13:21 |
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Joined: 01/19/16 Posts: 3278 Post Likes: +5509 Location: 13FA Earle Airpark FL/0A7 Hville NC
Aircraft: E33/152A
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Username Protected wrote: Tricky parts is the turbine is not supposed to switch fuel tanks. When O&N converted a couple 340s to twin Allison turbines they modified the aux tanks to continually refill the tips (mains) or the tips drain into the aux always I forget which it was. Then if you have locker tanks you can refill the tips but not feed directly from them like normal. The tricky part is tip tank Cessnas usually feed directly from the mains or aux tanks when selected.
Then there is the left right tank issue for a single turbine. Maybe header tank in the nose supplying the engine?
I wonder if the engine beam torque on the wing structure was figured into twisting moment during a High positive G event. Without the engines twisting the wing leading edge down is the spar strong enough?
Makes me wonder about the prop blade pulse frequency on the horizontal tail and the Conquest having dihedral horizontal tail vs the 421 does not. 441 having debonding issues of the tail also.
There are a lot of things to consider beyond bolting it on. I solved the fuel selection issue on my single turbine (converted 58TC Baron) by utilizing the in tank submerged pumps. Take off-both on (with inline check valves) after climb then turn one off. When wing gets heavy select to transfer (reconfigured factory valve to utilize crossfeed port and line to transfer to other side). When pressure switch triggers annunciator light (no flow) then turn that pump off. This way all of the remaining useable fuel is in one tank. Worked perfectly and never had to worry about unporting fuel. Entire fuel system is under positive pressure so no chance of drawing in air. https://motoplaneparts.com/czechmate/I utilized that configuration on this aircraft too. https://www.facebook.com/beechcraftheri ... 155373026/
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 15:20 |
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Joined: 08/24/13 Posts: 8409 Post Likes: +3662 Company: Aviation Tools / CCX Location: KSMQ New Jersey
Aircraft: TBM700C2
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Username Protected wrote: Tricky parts is the turbine is not supposed to switch fuel tanks. TBMs do it
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 17:26 |
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Joined: 01/10/17 Posts: 1662 Post Likes: +1127 Company: Skyhaven Airport Inc
Aircraft: various mid century
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Username Protected wrote: Tricky parts is the turbine is not supposed to switch fuel tanks. TBMs do it
Manually or automatic system?
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 17:36 |
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Joined: 01/10/17 Posts: 1662 Post Likes: +1127 Company: Skyhaven Airport Inc
Aircraft: various mid century
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I solved the fuel selection issue on my single turbine (converted 58TC Baron) by utilizing the in tank submerged pumps. Take off-both on (with inline check valves) after climb then turn one off. When wing gets heavy select to transfer (reconfigured factory valve to utilize crossfeed port and line to transfer to other side). When pressure switch triggers annunciator light (no flow) then turn that pump off. This way all of the remaining useable fuel is in one tank. Worked perfectly and never had to worry about unporting fuel. Entire fuel system is under positive pressure so no chance of drawing in air. https://motoplaneparts.com/czechmate/I utilized that configuration on this aircraft too. https://www.facebook.com/beechcraftheri ... 155373026/[/quote] 58TC airframe makes a lot more sense than the converted A36 turbines. For a Cessna wing Would that configuration work out with getting fuel from the aux tanks into the tips and then the tips supplying the selectors to then feed the engine. I think it would take another set of pumps to keep pushing fuel into the tips to refill as the mains? I guess it would be setup as the existing clicker pumps in the tip tanks always on. Aux tank pumps refilling the mains (tips) and boost pumps in the tips(mains) feed supplying the engine? Guess they made it work out somehow.
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 18:01 |
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Joined: 11/03/08 Posts: 14529 Post Likes: +22860 Location: Peachtree City GA / Stoke-On-Trent UK
Aircraft: A33
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Username Protected wrote: I always wondered why someone used the 340 instead of the 421 from the beginning. It seems like a no-brainer to have the larger cabin. My only suggestion would have been to use a 421C and eliminate the tip tanks for a more modern looking airplane... the best reason I can think, is that the 340 is about the biggest airplane you can fit into a common T hanger. However, I’m not sure that is still true after you put the long turbine snout on it.
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 18:13 |
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Joined: 04/06/11 Posts: 7895 Post Likes: +3908
Aircraft: Warbirds
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Username Protected wrote: TBMs do it Manually or automatic system? Auto on the 850
_________________ Be careful what you ask for, your mechanic wants to sleep at night.
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Post subject: Re: C421 converted to single PT6 Posted: Yesterday, 18:23 |
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Joined: 11/18/16 Posts: 82 Post Likes: +72
Aircraft: King Air C90
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Username Protected wrote: I don't know, it seems like they could make it longer Ha! Comment of the day.
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