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  #21  
Old 06-06-2011, 11:16 PM
ArlingtonRV ArlingtonRV is offline
 
Join Date: Feb 2005
Location: Marysville, WA
Posts: 378
Default Climb Suggestion

Quote:
Originally Posted by JohnF View Post
Take off climb at 68-mph WOT showed 5,040 rpm (climb rate 650 fpm +)
John,

I'm not trying to pick nits, but you might want to review Rotax SL 912-016 page 4 section 3.1.2 step 2. They recommend, among other things, that to help prevent preignition/detonation to not climb with WOT at less than 5200 RPM.

After reading that Service Letter I do what I need to clear the ground and once all obstacles are cleared I climb at just above 5200, which tends to give me about 82 knots and 800 - 1000 FPM (solo).
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Arlington, WA
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  #22  
Old 06-07-2011, 07:04 AM
JohnF JohnF is offline
 
Join Date: Jan 2005
Posts: 458
Default Climb and Hub setting

No, Steve, that 68mph at 5,050 is not the max available or full effort. It is a data point to determine hub adjustment recommended by Roger Lee of the Tucson Rotax Service Center....different rates of climb will produce different rpm max figures. They recommend testing performance by setting the rate of climb at 68mph and then insure that you have at least 5,000 rpm. Other than that there is no significance to that rpm figure. The second check data point they recommend is WOT in level cruise at what ever altitude you usually fly to insure that you can get 5500.
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  #23  
Old 06-07-2011, 10:12 AM
MartySantic's Avatar
MartySantic MartySantic is offline
 
Join Date: Apr 2008
Location: Davenport, IA
Posts: 1,369
Default

Quote:
Originally Posted by ArlingtonRV View Post
John,

I'm not trying to pick nits, but you might want to review Rotax SL 912-016 page 4 section 3.1.2 step 2. They recommend, among other things, that to help prevent preignition/detonation to not climb with WOT at less than 5200 RPM.

After reading that Service Letter I do what I need to clear the ground and once all obstacles are cleared I climb at just above 5200, which tends to give me about 82 knots and 800 - 1000 FPM (solo).
John,

If you set the blade pitch to get the 5200+ rpm at 75 knots (Vy), on take-off, you will easily hit 5800 rpm at WOT in level flight. The recommendation is not practical. A setting that gives you 5050-5100 rpm seems more practical.
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  #24  
Old 06-07-2011, 11:00 AM
JohnF JohnF is offline
 
Join Date: Jan 2005
Posts: 458
Default Prop Setting

I agree ... prop may be overpitched..based on this and other comments. I will increace the pitch in 1/10-degree increments and see what happens. Will post results when something is worthwhile.
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  #25  
Old 06-08-2011, 08:08 PM
Peterk Peterk is offline
 
Join Date: Mar 2008
Location: Texas
Posts: 1,375
Default Dynamic Balance

I mentioned on here before what a believer I was in the Dynamic Balance System that Walt performed on my RV12. So after the SB...my hub had to be replaced with a new, old revised hub....things didn't seem quite the same. Sure enough, took it back to see Walt today and it was off almost as much as it was originally. Apparently just shaving those two hub sides was enough to throw it off. We had to start over...and now all is wonderful again.
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  #26  
Old 06-09-2011, 06:16 AM
BigJohn BigJohn is offline
 
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,470
Default

Quote:
Originally Posted by Peterk View Post
I mentioned on here before what a believer I was in the Dynamic Balance System that Walt performed on my RV12. So after the SB...my hub had to be replaced with a new, old revised hub....things didn't seem quite the same. Sure enough, took it back to see Walt today and it was off almost as much as it was originally. Apparently just shaving those two hub sides was enough to throw it off. We had to start over...and now all is wonderful again.
Peter,

I found it quite amazing how sensitive the balance is to very slight changes in weight. A few grams one place or another can make a BIG difference. Sure is nice enjoying that famous Rotax smoothness!

John
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RV-12 N37JP 120176 Flying since 2012.
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  #27  
Old 06-09-2011, 07:21 AM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 4,374
Default

Quote:
Originally Posted by Peterk View Post
I mentioned on here before what a believer I was in the Dynamic Balance System that Walt performed on my RV12. So after the SB...my hub had to be replaced with a new, old revised hub....things didn't seem quite the same. Sure enough, took it back to see Walt today and it was off almost as much as it was originally. Apparently just shaving those two hub sides was enough to throw it off. We had to start over...and now all is wonderful again.
I first checked Pete's RV12 with the weights installed from the previous balance and found it over the limit at approx 0.260 IPS. We removed the previous weights and started over, results below. Went from 0.460 to 0.039 IPS (the red circle in the polar plot represents the upper limit of 0.2 IPS).

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  #28  
Old 06-09-2011, 12:24 PM
Peterk Peterk is offline
 
Join Date: Mar 2008
Location: Texas
Posts: 1,375
Default John

amazing how sensitive the balance is to very slight changes in weight

Yeah John, you're so right. I think Walt has about 40 different thickness' of washers that he can use!

Pete
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  #29  
Old 06-14-2011, 11:27 AM
dick seiders dick seiders is offline
 
Join Date: Jan 2006
Posts: 875
Default

Took the 12 up for another test flight this morning. I made no changes since last flight a week ago except to top off the tank with 11 gal of fresh fuel. The temp was 32C. The density alt was 2600'. Winds 5kts from 030 on runway 10. Static run up was 4950, but held that only for a few sec. and fell to 4920 where it held steady. WOT on t.o. and rpm at 5050 at angle producing 70 kts By the time I was at 400' alt the rpms had dropped to 4900. I lowered the nose to get rpms to 5000. Climbed to 2200 msl and leveled off for about 15 sec which produced only a continued 5000. I turned onto left crosswind since I decided to stay in pattern given what was happening. I pulled throttle to 4500 then went to wot and max rpm in level flight was 5300. I again pulled throttle back to 4900, got a burble which dropped rpm to 4700. I went back to 5000 with more throttle and then adjusted speed dropping to 3750 rpm which I maintained until turning final, and then adjusted to 2200 rpm for landing. No further events. I again checked my prop blades with my Warp Protractor (I know, I know, and I am building a Tony T. style digital setup).The blades were w/i .3 degrees. I am thinking now that the prop hub, adjusting, blade match, etc. hasn't anything to do with what's going on. Clearly it must be a fuel or ignition issue. I pulled the top cowl and inspected everything and found nothing obvious. No time to pull bottom today and check plugs, but will do tomorrow. Ok, please tell me what all y'all think is going on possibly. Thanks.
Dick Seiders
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  #30  
Old 06-14-2011, 12:20 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,534
Default Vapor Lock?

Dick,
The problem is likely one of three causes:
1. Vapor Lock
2. Bad engine driven fuel pump
3. Heavy carburetor float
See the threads below and pick one to post in:
Joe Gores
http://www.vansairforce.com/communit...ad.php?t=72330
http://www.vansairforce.com/communit...ad.php?t=72604
http://www.vansairforce.com/communit...ad.php?t=66775
http://www.vansairforce.com/communit...ad.php?t=70434
http://www.vansairforce.com/communit...ad.php?t=69242
http://www.vansairforce.com/communit...ad.php?t=57774
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