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ltaylor02(at)Chartermi.ne Guest
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Posted: Tue May 10, 2011 2:33 am Post subject: MODEL IV-1200 PERFORMANCE |
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I have a Model IV-1200 with 21 hrs TT; eng/airframe with a 68" GSC GA wood prop. I'm not seeing the performance from the 618 that I expected. I been all over the pitch and static RPM relationship in an attempt to find best climb/speed. Presently, I'm pitched at 14 degrees using the GSC tool provided; showing 6400 RPM static; full throttle flight RPM of 6800 at 82 MPH; at 6000 RPM (cruise), I'm showing 74 MPH; full power climb of 600 ftmin. The plane is OEM except for grove gear with an empty weight of 623lbs. The plane responds very well without any glaring drag issues. EGT's 1120; plugs look great; jetting per the manual. I'm the builder. Any feedback would be much appreciated. Perhaps it is what it is, but I expected more speed and better climb.
Lane
N356RL
KOSC
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Tom Jones
Joined: 12 Mar 2006 Posts: 752 Location: Ellensburg, WA
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Posted: Tue May 10, 2011 5:48 am Post subject: Re: MODEL IV-1200 PERFORMANCE |
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Lane, there have been a couple times over the years I can remember a performance issue like you are having. The problem was that the tachometer was faulty. have you checked the RPM with an optical tach? Another way to cross check is to install a Tiny Tach. http://www.buycheapr.com/us/result.jsp?ga=us12&q=tiny+tachometer
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_________________ Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA |
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Guy Buchanan
Joined: 16 Jul 2006 Posts: 1204 Location: Ramona, CA
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Posted: Tue May 10, 2011 7:02 am Post subject: MODEL IV-1200 PERFORMANCE |
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On 5/10/2011 3:31 AM, lane taylor wrote: Quote: | The plane responds very well without any glaring drag issues. EGT's 1120; plugs look great; jetting per the manual. I'm the builder. Any feedback would be much appreciated. Perhaps it is what it is, but I expected more speed and better climb. |
Lane,
The key here is that the plane "responds well". Sounds like it's working better than your measurements would indicate. So, as Tom already said, the first things to check are your measurements:
- Tach with an model airplane optical tach.
- ASI with a set of accurate, no wing, GPS runs.
- Measure OAT while making the ASI runs to make sure your density altitude is reasonable.
- Make time to climb measurements to verify the VSI. One trick I learned while doing this was to get the aircraft in a stable climb, take a picture of the panel with the GPS showing time, then wait a while and take another picture. Get back to base and use the pictures to figure out the rate of climb based on the change in time on the GPS and the change in altitude.
Next I have some questions:
- What's your gearbox ratio?
- How many blades on the prop?
- Are the EGT's full throttle?
- Is this a single plug head?
- Is this a round cowl?
- What has been faired? Possible options include:
- Wing struts
- Jury struts
- Radiator
- Horizontal stab struts
- Vertical / horizontal junction
- Gaps on vertical and horizontal
- What kind of wing tips are you running? (A picture might answer a lot of these.)
- What's your radiator installation look like?
Your speeds are low, as my 582 powered IV will top out at 110 mph at 6800 rpm. However I've been told my 582 is "fast" for what it's worth. It has everything faired but the radiator. I understand that "dirty" IV's are much slower. (I've heard 15%, or 15mph for the wing struts alone.) Enough for now.
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. and grounded
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_________________ Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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ltaylor02(at)Chartermi.ne Guest
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Posted: Tue May 10, 2011 8:27 am Post subject: MODEL IV-1200 PERFORMANCE |
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ltaylor02(at)Chartermi.ne Guest
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Posted: Tue May 10, 2011 8:27 am Post subject: MODEL IV-1200 PERFORMANCE |
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Miss fire. I'll check out the tach. Deke's been suggesting the same...
Thanks Tom
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ltaylor02(at)Chartermi.ne Guest
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Posted: Tue May 10, 2011 1:30 pm Post subject: MODEL IV-1200 PERFORMANCE |
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Apparently my earlier email had too many pictures so here's round two....
C box 3:1
Three bladed wood GSC presently set at 14 degrees
Cruise and full throttle EGTs remain between 1100 - 1200 F
Duel plugs per head
Round cowl
The only fairing is on the wing struts. I don't have gap seals or any other drag reducing strategies or devices. I've double checked my wing dihedral which is set at 2 degrees per side. All my measurements are within 1 or 2 mm of the manual's recommendation. She flies great--just at a slower than anticipated rate of speed and climb. I'll try your suggestions...
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dave
Joined: 22 Sep 2006 Posts: 1382
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Posted: Tue May 10, 2011 2:34 pm Post subject: MODEL IV-1200 PERFORMANCE |
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What are you using for Airspeed ?
ASI or GPS?
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Guy Buchanan
Joined: 16 Jul 2006 Posts: 1204 Location: Ramona, CA
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Posted: Tue May 10, 2011 3:22 pm Post subject: MODEL IV-1200 PERFORMANCE |
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On 5/10/2011 2:26 PM, lane taylor wrote: Quote: | The only fairing is on the wing struts. I don't have gap seals or any other drag reducing strategies or devices. I've double checked my wing dihedral which is set at 2 degrees per side. All my measurements are within 1 or 2 mm of the manual's recommendation. She flies great--just at a slower than anticipated rate of speed and climb. I'll try your suggestions... |
Yep. Clean enough, and very attractive. You should be going at least my speeds. I'd hope for an ASI or tach error.
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. and grounded
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_________________ Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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ltaylor02(at)Chartermi.ne Guest
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Posted: Wed May 11, 2011 3:43 am Post subject: MODEL IV-1200 PERFORMANCE |
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Hi Dave, I have both and on calm days the ASI and GPS are very close as are the VSI and GPS.
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