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Author Topic: What can be done?  (Read 1083 times)

Bruce Byerly

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Re: What can be done?
« Reply #15 on: September 05, 2019, 01:18:51 pm »
Glenn

I have available 2 720’s, the props, and probably most of the parts to convert a 680FL(p) to 720 power. STC’s get rid of the 3000 psi hydraulic system and it’s supercharger too.

If you want to do it, it’s probably doable with enough time and money!


AC680fan

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Re: What can be done?
« Reply #16 on: September 05, 2019, 07:30:02 pm »
Glenn,

Don’t know what you’re willing to try, but there’s also at least 1 680 fp in Germany with fresh <100 hr engines. 67’ model used in aerial survey, that apparently they can no longer certify due to EASA regulations. One add stated for export or part out. No price was given. The add was on “aircraft24.com”. Hope this was useful.

https://www.aircraft24.com/multiprop/commander/680fl--xi130880.htm
« Last Edit: September 05, 2019, 07:37:20 pm by AC680fan »

ghancock

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Re: What can be done?
« Reply #17 on: September 06, 2019, 08:50:10 am »
Thanks for all the info.  And I'm weighing all my options at the moment.  Things will start to move as soon as this hanger is finished so I can get her back inside to start work.  Having the Beech 18 does give me more time to do things as I won't be in a rush to get her flying immediately.  The 720's project does sound interesting but need to get all the parts and processes lined up ahead of time to make sure I don't work myself into a hole.

As for the gearbox on this particular engine, the engine turns at 3400rpm on takeoff and 47" of manifold.  The prop is only turning around 60% of that on this engine.  It makes for an exciting takeoff roll and makes it even more interesting that it will push well over 46" so you have to watch what you're doing on each takeoff.

I've been talking to Bill Leff about it and he's telling me to just let her drink the gas and the engines will last.  He said the reason people have so much trouble with them is trying to lean them out too much and that most people throughout the years have always tried to do that.  But there are others that just keep them fed and they last like a normal engine.

I may give that a shot too but still trying to decide.  We'd be talking about 60gph for an airplane that barely flies 200knots.   Not sure if I'd be able to do that for long. :-)

Glenn
--glenn
You can't win an argument with an ignorant person,  they'll just drag you down to their level and beat you with experience.

Roy

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Re: What can be done?
« Reply #18 on: September 06, 2019, 10:40:59 am »

@ Steve, thanks, I showed my ignorance in public on how the gear boxes work. Thought it was the other way around.

Roy


WilsonRiggan

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Re: What can be done?
« Reply #19 on: September 07, 2019, 03:07:51 pm »
Hi, Glenn, et. al.

My 685 is very similar, with the GTSIO-520K's.  3400RPM, 44.5 inches MP at takeoff to generate 435hp.  Thankfully, I have not had as much difficulty with cylinders.  I think it's because of my constant monitoring of CHT's via my EDM-800's.  At any reasonable kind of altitude (thinner air, less effective at cooling), I cannot run with the cowl flaps anywhere near full closed and still keep the CHT's under 435 (I like to leave a margin for error below the 460 max) with a properly-leaned mixture.  That generates about a 5kt airspeed loss due to the drag, but I'll take it vs. cooking the cylinders.

By the way... I rely heavily on the engine analyzers to show me the individual CHT's.  The OEM gauge shows just one cylinder... and it's not the hottest one.  I likely would have cooked off several cylinders by now without even knowing why.

Wilson

ghancock

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Re: What can be done?
« Reply #20 on: September 30, 2019, 10:13:51 am »
Thanks,

Yeah, I use my monitors as well and I generally kept my CHT's below 400.  I ran LOP though with generally 390 F temps.  The problem though is when running LOP your EGT's are generally higher and I am burning Exhaust valves.  So I'm thinking of switching back to ROP.  However, we're talking 38gph at LOP and 60GPH ROP.  When flying ROP I can barely lean the mixtures at all before the CHT's go through the roof.

Are you running ROP or LOP?

Glenn
--glenn
You can't win an argument with an ignorant person,  they'll just drag you down to their level and beat you with experience.

WilsonRiggan

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Re: What can be done?
« Reply #21 on: October 17, 2019, 11:23:57 pm »
Hi, Glenn.

I run ROP.

Badger

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Re: What can be done?
« Reply #22 on: October 18, 2019, 02:27:09 pm »
Glenn,

I run LOP.

ed
Ed

donv

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Re: What can be done?
« Reply #23 on: October 20, 2019, 06:14:06 am »
But the 500 really isn't a fair comparison to the big geared engines on the 680/685, is it?

Glenn,

I run LOP.

ed

Badger

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Re: What can be done?
« Reply #24 on: October 21, 2019, 10:12:09 am »
I am sure you are right.  I just jumped in there, not thinking about that ...  ;-)

Ed
Ed

ghancock

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Re: What can be done?
« Reply #25 on: November 04, 2019, 01:00:32 pm »
Yeah, the issue is not the CHT as I keep all mine below 390F.  The issue is with EGT's when LOP as they do run higher and 100% of my cylinder problems have been with burnt exhaust valves.  I may just try running ROP once I get her in annual again and see how that goes.  Problem is we're talking 38GPH LOP and 60GPH ROP.

Glenn
--glenn
You can't win an argument with an ignorant person,  they'll just drag you down to their level and beat you with experience.

Popeye

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Re: What can be done?
« Reply #26 on: December 26, 2019, 10:49:08 pm »
Heyy Glen...how about some allisons??  Perhaps talk to lycoming for a recommended engine and do an STC?? I am on the same boat, but I do run ROP instead of LOP. They go for about 800 hrs.