JSF-TC

My Feedback: (2)

I've just tried the 1st flight of my AD small Rafale with an OS91/Ramtec fan/ JMP System II pipe/ BVM Remote Needle Valve combination.

Unfortunately after a very long take off run (150yds+ on a paved runway) it just got into the air but on the wrong side of the drag curve, and mushed along for a few seconds with the gear up at about 10 feet before I cut the power as it slowly sank into the grass at long range. Minor damage to one main gear door and air ram and a cracked bulkhead which should be easily repaied.

Ran the engine again afterwards and found that with the BVM remote arm approx 3/4 turn open as recommended, I could fully close the main needle valve and still have the engine running rich. Full lean on the remote needle servo did produce an increase in revs but still with a lot of smoke. I can't get the motor to run over lean, even with the needle fully in. Any suggestions??

I've got my 2 saddle tanks plumbed in series with the Ramtec pitot pressure, and I notice that when I fill the tanks I seem to pressurize the tanks which takes a few seconds to dissipate and if I'm not careful dump fuel into the fan unit throught the pressure line. Both tanks feed normally on their own. I can run the engine down and drain both tanks with virtually no trapped fuel left but I don't know if there is a fuel restiction holding back the engine. I don't think I can shorten the fuel lines much more. Should I go back to parallel tanks??

Any other thoughts of how to increase thrust significantly to produce a more successful second flight attempt??

Thanks

Paul

I will master this DF thing - Just so I can fly Jet A-1

Jackjet

My Feedback: (1)

Jsftc,
please make sure there is absoulutely NO dirt inside the remote needle valve and or carb-and it doesnt take much to cause this kind of engine problem.I have run tanks in series and parallel and having a tight leak-proof "fod" free tank and carb. is very important.There MAY be some dirt in there-check it out........


Jackjet

Kevin Greene

My Feedback: (85)

How large are your fuel lines? I always used the large silicone tubing to plumb my jets. Try going to a parallel set-up just to see what happens. Also, put a small header tank in that thing!!! It will not only help to smooth out the fuel supply during aerobatics but will give you better needle valve control too. I used a 2 ounce header tank on all of my DF models. Sometimes too much pressure from the pitot coupled with fuel tanks that are above the carb centerline will cause what you described. Again, a header tank can also alleviate the above mentioned fuel supply problems by helping to regulate the fuel flow. If you do go to the parallel set-up be sure to make all of your fuel lines equal. Let us know what you find.

Kevin

Richard Buescher

Make sure that the mixture control valve closes all the way. If you can blow through it with it "Closed", you have a problem. It should be able to block all fuel flow if you wanted it to. I have ordered 3 of them earlier this summer. I have now used all three. They all would not go lean enough. I ended up having to tighten the jam nut more and screw the needle in with a plyers. This may not be the correct way but after a few times in and out the threads opened up and they became easier to use. My guess is they had a bad run of these. Mabey a worn out tap or something. I have had more of these that did not have the problem.


Funny story:
I actually used one of these on my school weight lifting project. We finished the plane the night before the qualification day. So at 1:00 A.M. we ran the o.s. .61 outside our motel room. Need less to say the police came before our 2 oz tank was gone! It would not lean out. So frantically I called John Redman's house at 2:00 A.M. Ofcourse I had another mixture control in the morning and we fixed the problem mixture control!
Thanks John if your out there!
Dustin