loss of fuel on dive= dead stick  
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All Forums >> RC Airplanes >> Questions and Answers >> loss of fuel on dive= dead stick
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loss of fuel on dive= dead stick - 7/8/2008 9:17:49 PM   
Big-Mo


 

Posts: 32
Joined: 11/11/2007
From: Richmond, MO, USA
Status: offline 		OK I have NEVER had this happen in 13 years of flying,

got the laser200 all ready to rock on and when i go into a dive it runs out of fuel got it down and checked everything out and it is actually running out of fuel due to the clunk coming out of the fuel and sucking air. i have several air planes of same style sport flying and none of them run out of fuel , any suggestions? i hate dead sticking a flying model instead of a gliding model !


HELP!!!!!!!!!!!!!!!!
lol

Big-Mo
       Post #: 1

RE: loss of fuel on dive= dead stick - 7/8/2008 9:26:36 PM   
Big-Mo


 

Posts: 32
Joined: 11/11/2007
From: Richmond, MO, USA
Status: offline 		i checked my other setups 3 of them doen the exact way and they have no problems/

Im stumped

(in reply to Big-Mo)
       Post #: 2

RE: loss of fuel on dive= dead stick - 7/9/2008 8:27:54 AM   
alan0899


 

Posts: 2023
Joined: 4/17/2006
From: Cundletown, NSW, AUSTRALIA
Status: offline 		G'day Mate,
The fuel cannot run to the front of the tank in a dive, it is imposible, for that to happen, the fuel must accelerate faster than the plane, & that can't happen unless the plane stops in mid air then the fuel can fall forward. Also the clunk can't fall to the front of the tank in a dive, for the same reason.
That is why it doesn't happen in any of your other planes, so you must have a hole in your fuel line, in the tank, or the clunk is getting stuck at the back of the tank, then as the nose drops, the clunk could come out of the fuel, because it is no longer level, & then it could suck air.
Hold the plane nose straight up, & give it a shake, you should be able to hear the clunk swinging side to side, & top to bottom, if you can't then there is your problem.

_____________________________

Good Flyin Mate. Keep Thyne Airspeed up, lest the ground arise & smite thee, Allan.

(in reply to Big-Mo)
       Post #: 3

RE: loss of fuel on dive= dead stick - 7/9/2008 12:35:29 PM   
BillyGoat


 

Posts: 476
Joined: 5/19/2004
From: -, MT, USA
Status: offline 		From personal experience, my guess is your pick up line in the tank is just a tiny bit too long.

Even if you can hear the clunk moving around, try shortening the line about 1/8 of an inch.

< Message edited by BillyGoat -- 7/9/2008 12:39:05 PM >

(in reply to alan0899)
       Post #: 4

RE: loss of fuel on dive= dead stick - 7/9/2008 4:02:29 PM   
Jburry



Posts: 560
Joined: 7/12/2006
From: Cape Spencer, NB, CANADA
Status: offline 		Fuel does run to the front of the tank in a dive. A plane does accelerate in a dive, but only to a point. It must accelerate at more than 1g continuously for the fuel to stay in the back of the tank. This will not happen. The airframe is slowed by drag. The fuel is not. It falls to the front of the tank. This is high school physics.

There was a video making the rounds about this a year or so ago. Showed this very clearly.

In a downline, the engine runs ONLY on the fuel already in the line. If the downline lasts much longer than the fuel in the line, flameout. Very few downlines last this long. At 60mph, you're doing about 100 feet per second. The fuel in the line will last most engines several seconds. How many hundreds of feet are you diving from? Larger engines can thus benefit from having larger and longer lines. Reducing throttle setting during the dive will also extend the available dive time.

J

_____________________________

Revver Bro. #220

(in reply to alan0899)
       Post #: 5

RE: loss of fuel on dive= dead stick - 7/9/2008 10:01:56 PM   
scratchonly


 

Posts: 946
Joined: 6/3/2006
From: winnipeg, MB, CANADA
Status: offline 		I have seen the video jberry refers to; it was made in germany with the plane mounted camera focused on an external fuel tank; a flying buddy disputed this saying he often flys 10 second downlines, we timed his long down lines, they lasted 2-3 seconds! Fuel behaved as jberry states.

< Message edited by scratchonly -- 7/9/2008 10:03:11 PM >

_____________________________

Real planes have two wings and round engines

(in reply to Jburry)
       Post #: 6

RE: loss of fuel on dive= dead stick - 7/9/2008 10:33:51 PM   
Big-Mo


 

Posts: 32
Joined: 11/11/2007
From: Richmond, MO, USA
Status: offline 		OK so everyones right how do I stop this , as i flew it today and it is almost immediately flamed out ,,, fuel line is only 5 inch long , do I wrap fuel line around the plane to get it to run longer? I'm stumped on this one , I have 3 other planes setup the exact same way and none of them do this, one with a ys 91AC in a super sportster, a super hots with a super tigre 61 in it, and a acromaster with a eyna 120 in it i have none of these problems...

(in reply to scratchonly)
       Post #: 7

RE: loss of fuel on dive= dead stick - 7/10/2008 12:44:15 AM   
gjesion


 

Posts: 54
Joined: 6/11/2007
From: Woodhaven, MI, USA
Status: offline 		I don't have a solution to your problem, but i do have a question relating to it. If the pickup is out of the fuel during the down line and sucking air, why doesn't the engine burp when the air in the line gets to the carb? Or am I missing something?

Regards,
Jerry

< Message edited by gjesion -- 7/10/2008 12:49:52 AM >

(in reply to Big-Mo)
       Post #: 8

RE: loss of fuel on dive= dead stick - 7/10/2008 1:35:36 AM   
Villa



Posts: 875
Joined: 8/12/2003
From: Wilson, NC,
Status: offline 		The fuel line in the fuel tank must be flexible enough to allow the clunk to move to the front of tank a little when the front of the tank is pointing down. Many fuel lines are too stiff. It seems to me that if the engine is running on the fuel in the line while in a dive, then the line is filling with air. When the plane levels off, the engine will see a 'chunk" of air in the fuel line and may stop running.

(in reply to gjesion)
       Post #: 9

RE: loss of fuel on dive= dead stick - 7/10/2008 2:03:59 AM   
Big-Mo


 

Posts: 32
Joined: 11/11/2007
From: Richmond, MO, USA
Status: offline 		Your Absolutely Correct Villa thats exactly what its doing.

Jerry you are also right it is burping to the point of killing the engine,

What fuel line should i use for the tank klunk? I'm using GP 3/32 line, to big? to stiff?


maybe were getting closer.

I hope

(in reply to Villa)
       Post #: 10

RE: loss of fuel on dive= dead stick - 7/10/2008 2:17:35 AM   
PilotFighter



Posts: 2019
Joined: 10/9/2002
From: Houston, TX, USA
Status: offline 		I had this happen on a Cap232. Open the tank and shorten the pick-up. Fixed mine.

_____________________________

turn left, your other left

(in reply to Big-Mo)
       Post #: 11

RE: loss of fuel on dive= dead stick - 7/10/2008 5:03:15 AM   
Charlie P.



Posts: 2281
Joined: 2/25/2003
From: High Above Upstate, NY, USA
Status: offline 		These kind of problems are fun when you're looking back on them . . . but a real pain when they are in process. My thought would also be to shorten the inside line to the klunk. I have also had some real puzzlers from tiny holes in the fuel lines both inside and outside the tank. One of the worst was a split fuel line inside the tank at the stopper tube that had me ready to scream. That was a twisted wire (Sullivan style) that had sliced through the silicone line. The line would suck air when I went vertical and I thought the klunk must have slipped forward. I had the tank out of the model several times before I decided to replace all the fuel lines and found that.

When something like this happens now I start with all fresh fuel lines and THEN worry about the next steps.

_____________________________

Charlie P.
"Gravity is weak but it is persistant" AMA 747089/IMAA 30723

Oh Lord, your earth is so hard and my planes are so frail.

(in reply to PilotFighter)
       Post #: 12

RE: loss of fuel on dive= dead stick - 7/19/2008 8:11:29 PM   
pt19 flyer



Posts: 333
Joined: 11/9/2002
From: Roanoke, VA, USA
Status: offline 		hi

one solution to this which has worked in the past is to loop the fuel line to the carb around the fron of the engine. this gives a little reserve to the engine if fuel in the tank is low enough to let the clunk out of the fuel briefly in a dive

good luck and happy flying

pt19 flyer

(in reply to Big-Mo)
       Post #: 13

RE: loss of fuel on dive= dead stick - 7/19/2008 8:42:35 PM   
dbacque


 

Posts: 385
Joined: 6/3/2005
From: Houston, TX, USA
Status: offline 		I had a very draggy quarter scale bipe that had this problem. I tried everything including pumps and it still died in dives. Finally I put a 1 oz. header tank in front of the main tank. The vent on the main tank is still connected to the muffler, the fuel line from the main tank goes to the vent line on the header tank and the fuel line from the header tank goes to the carb.

When you fill from the carb line the fuel fills the header tank then overflows into the main tank. Now when you run (in level flight) the header tank will stay full until the main tank is empty, then the header tank will empty. When you dive, any bubbles picked up in the main tank will go to the header tank but the bubble stays in the header tank and the engine still has a steady supply of fuel. Make the klunk line short in the header tank, to about the center of the tank. You'll never pass another bubble to the engine.

It fixed my problem.

Dave

< Message edited by dbacque -- 7/19/2008 10:03:29 PM >

(in reply to pt19 flyer)
       Post #: 14

RE: loss of fuel on dive= dead stick - 7/19/2008 9:12:17 PM