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Cornfused about HSN setting - 8/19/2007 1:50:32 AM   
Tbone4life



Posts: 138
Joined: 2/17/2006
From: pearland, TX, USA
Status: offline 		Magnum XLS .15A

The paper work that came with my XLS .15A, says that the engine RPM will increase 10 -30% in the air over that achivable on the ground. this is due to the forward motion of the airplane as well as the aerodynamics of the propeller and the lower levels of fuel in the tank after fly a few minutes. (Basically they say set it rich on the ground).

Since I cant take an rpm reading in flight (due to lack of hobby funds ) has anyone (2Cool) with the electronics in their planes able to read RPM during flight noticed this?

Why does O.S and Satio not mention this in their paperwork?

My XLS .15 with an 8x3 MAS combat prop turns 18,000 RPMs on the ground
18,000 + 10% = 19,800 RPMs
18,000 + 30% = 23,400 RPMs = Ka-Klunk!!!!

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RE: Cornfused about HSN setting - 8/19/2007 5:18:26 AM   
AirScharnell


 

Posts: 29
Joined: 6/8/2004
From: Parker, CO, USA
Status: offline 		SInce you are spinning the MA 8x3, I will guess you are getting ready for SSC combat?
All engines unload in the air. You are not holding it stationary. ANd im sure that after you get some time on that MAGnum your RPM may go higher.

Frank

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RE: Cornfused about HSN setting - 8/19/2007 6:12:21 AM   
OzMo



Posts: 1500
Joined: 9/2/2002
From: OZark, MO, USA
Status: offline 		the wings fell off the plane in your avitar

yep a little rich is standard for all glow engines on planes. happy hunting

< Message edited by OzMo -- 8/19/2007 6:13:51 AM >

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RE: Cornfused about HSN setting - 8/20/2007 1:56:44 AM   
Montague



Posts: 4653
Joined: 4/19/2002
From: Laurel, MD,
Status: offline 		Like the guys said, all engines unload in the air, and will run leaner than they are set on the ground. The other engine instructions DO say to back the engine off of peak RPM on the ground, they just don't explain exactly why.

In general, the amount you need to richen the needle depends on the engine, airplane, and prop, since different combinations will unload differently in the air, which means the amount the mixture will change varies a lot depending on your setup.


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RCCA 560

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RE: Cornfused about HSN setting - 8/20/2007 2:02:21 AM   
Tbone4life



Posts: 138
Joined: 2/17/2006
From: pearland, TX, USA
Status: offline 		I never even thought of this happening to the engine, I've cooked a couple of car and truck engines , but that was due to gettin a little to twist happy with the HSN, when I wanted it to go just a "little" faster.

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RE: Cornfused about HSN setting - 8/20/2007 2:10:28 AM   
Montague



Posts: 4653
Joined: 4/19/2002
From: Laurel, MD,
Status: offline 		Yeah, the mixture can change quite a bit in the air. Also, you'll find that the tank setup is more critical, especially with the smaller engines like the Mag .15XLS. The XLS has a large carb throat, and a large exhaust opening, so it doesn't draw fuel well if you have a bad setup. And it will lean out in a hard turn or sustained climb as well, if you're tank isn't right.


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Kirk Montague Adams
RCCA 560

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RE: Cornfused about HSN setting - 8/20/2007 11:25:00 AM   
j.duncker



Posts: 1228
Joined: 6/22/2004
From: Where I park the RV, AK, USA
Status: offline 		Assuming you are flying something capable of 75 +mph in the air a 3 inch pitch is low. I fly 12th scale combat and use the APC 7x5 on a OS 15 CVA.

On a 750 gr model the vertical is unlimeted and I am one of the faster kids on the block.

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RE: Cornfused about HSN setting - 8/20/2007 2:15:20 PM   
Montague



Posts: 4653
Joined: 4/19/2002
From: Laurel, MD,
Status: offline 		j.duncker,

Since the OP is in Texas and asking about the 8x3, I think it's safe to assume he's flying SSC combat, which, as far as I know, isn't flown over there in the UK. The MAS 8x3 is the manditory prop for SSC, the idea is to keep the speeds down to closer to 55mph, which it does.

Using .15s in a scale combat class is pretty much dead in the USA at this point.


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Kirk Montague Adams
RCCA 560

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RE: Cornfused about HSN setting - 8/20/2007 8:21:24 PM   
j.duncker



Posts: 1228
Joined: 6/22/2004
From: Where I park the RV, AK, USA
Status: offline 		Rats. I am heading to Texas and I like fast.

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