Jet Legend F-18C First Flight Issues  
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Jet Legend F-18C First Flight Issues - 6/20/2007 12:33:15 AM   
F15driver



Posts: 88
Joined: 12/7/2001
From: New Braunfels, TX, USA
Status: offline 		Had my first 2 flights with the F-18 yesterday. Balanced per the CG plans just aft of the front carbon fiber wing rod with only the UAT full and other tanks empty, wheels down. On takeoff the plane leaped off the ground with half flaps after achieving takeoff speed. Controlled with down elevator and all OK until trimming. Airplane exhibited a strong tendency to climb, implying an aft CG. Also it req'd a lot of right aeliron trim which, after the first landing, I trimmed the right horozional stab a little down at the front. The second flight was a little better as far as needing right trim but it still wanted a lot of down trim. I did build this one without wheel doors and there was a lot of drag from the lack of doors. Heres the questions: 1) Has anyone used the CG per the plans sheet and found it correct, and 2) has anyone built this plane without doors and found their absence a major issue as far as trim is concerned? I'm using a TJT turbine rated at about 27 lbs. and I needed all of it to fly this airplane. Haven't weighed it yet but its pretty clear I'm well below 1:1 thrust to weight. All comments appreciated as I would like to improve the handling on the next flights.
Rob

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       Post #: 1

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 2:00:48 AM   
squirt!


 

Posts: 106
Joined: 5/27/2007
From: , SC, USA
Status: offline 		Rob,

I have the SM F-18...think it might be the same plane depending on who you ask...I dont have doors on mine. I think there is some significant drag by doing so. I just cant bring myself to install 9 doors and all the headaches that go with gear doors. I just like the simplicity of no doors. I have a P120 in mine so I think I have even less thrust than you and I'm at full power for most of the flight. I would put something bigger in it, but I just dont think the fuel capacity would support it.

As far as the CG goes...I think on mine I started where SM had the CG and slowly moved it back as it was considerably nose heavy. However, Im sure JL has put out a new set of instructions. The plane looks outstanding in the air...but it is a handful to fly.

Good luck!

(in reply to F15driver)
       Post #: 2

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 4:00:48 AM   
JoelP


 

Posts: 186
Joined: 9/25/2004
From: Santa Clara, TX, USA
Status: offline 		I just finished a Tam's Supa Hornet with the 9 gear doors. I think you'll find that they're time consuming to install but not at all difficult to do. I can't speak about the other F-18's out there, but the doors on this one fit really well and the plumbing was straight forward. I put air to the system the other night and the gear/doors worked perfect...freakin awesome watching those doors close!
I saw the second flight on Rob's F-18 and I think there is a lot of drag with the doors off. I agree that the plane looks good in the air and looks awesome on final when the nose assumes high AOA for landing! Good job on the build Rob and congrats again!!!

(in reply to squirt!)
       Post #: 3

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 3:01:44 PM   
meps


 

Posts: 189
Joined: 5/11/2004
From: durham, NC, USA
Status: offline 		I've always balanced my airplanes in the flight configuration.(wheels up) I think one of the problems you're having is that you balanced yours with the wheels down. After take off, you retracted your gear and some weight was shifted aft as the F-18 mains retract to the rear. I think if you balance your plane with the gear retracted, it will get you closer to the desired flight characteristics you'd like.

(in reply to F15driver)
       Post #: 4

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 5:04:29 PM   
ravill



Posts: 1958
Joined: 1/24/2003
From: Redwood, CA, USA
Status: offline 		Rob,

The F-18c is my favorite airplane and I fly the living crappola outta mine. She is a sweet heart to me. I have flown a total of 3 different F-18c's (2 SM, 1 JL) and I've got another one from xtreme jets on it way. That is how much I love this airplane. She is an honest airplane and the closest scale airplane that flies like a sport plane.

1. I have learned that on Hornets, resist the urge to move the cg back. The leading edge extensions can make for some really bad tendancies on final and on your flare. This is especially true on superhornets. I know this by personal experience. Do a search.

I have the cg right on the front carbon spar, wheels down, fuel in the UAT, and love it.

2. I HATE GEAR DOORS. I use them ONLY if the plane has already got them or the manufacture tells me exactly where to put them.

I've attached vids of the first day of flying the JL F-18C. I cannot speak enough about how much I love this airplane. Oh, and I use tailerons on mine.

http://video.google.com/videoplay?docid=8650789230006470651&hl=en

http://video.google.com/videoplay?docid=2980949992371566069&hl=en

Once you figure out these problems, you're gonna love her, I promise. I'm thinking that your CG is a little aft.

Raf

< Message edited by ravill -- 6/20/2007 5:48:30 PM >

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(in reply to meps)
       Post #: 5

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 5:14:25 PM   
mach1-RCU



Posts: 371
Joined: 12/6/2001
From: Huntsville, AL, USA
Status: offline 		Raf,

What size engine(s) are you using in your F18's.

(in reply to ravill)
       Post #: 6

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 5:49:27 PM   
ravill



Posts: 1958
Joined: 1/24/2003
From: Redwood, CA, USA
Status: offline 		I flew two with p-120's and my JL has a Titan. They fly fine with 120's and have great vert with titans!

Raf

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RE: Jet Legend F-18C First Flight Issues - 6/20/2007 6:02:17 PM   
F15driver



Posts: 88
Joined: 12/7/2001
From: New Braunfels, TX, USA
Status: offline 		Raf,
Ditto the above question re engine size. It seems you have gobs of vertical. How did you immobilize the ailerons as you're using tailerons? I'm going to use the earlier suggestion of balancing with wheels up and see if it moves the CG to the front carbon fiber wing rod.
Thanks all for suggestions.
Rob

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Don''t look back, they may be gaining on you!

(in reply to mach1-RCU)
       Post #: 8

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 6:11:39 PM   
ravill



Posts: 1958
Joined: 1/24/2003
From: Redwood, CA, USA
Status: offline 		I didn't immobalize the ailerons! I use tailerons and ailerons.

After many flights I have seen that the best, scale, take offs, for me, are achieved as follows.

Full throttle roll out and with some ground speed just start to pull on the elevator until the nose just rotates and keep the elevator at a postion that keeps the nose at the angle that I want. And I am using full flaps (~35 degrees).

I found that this works better than holding full elevator for the lift off.

Like I said, moving the CG back will make the plane roll a little better, fly inverted a little better, but can turn the airplane into a bear to land! I moved the Cg back from the former to the carbon spar (1cm or so) and that is all I am willing to go, esp after my lessons with my superhornet.

Raf

< Message edited by ravill -- 6/20/2007 7:40:54 PM >

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       Post #: 9

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 6:15:01 PM   
ravill



Posts: 1958
Joined: 1/24/2003
From: Redwood, CA, USA
Status: offline 		Oh and don't be scared to deploy the airbrake to land. That lets you carry a little more power to the runway.

I deadsticked my JL f-18c at BTW a few weeks ago (stripped engine mount causing the engine too move and pinch the fuel line ) and was surprised at how much it glid! I wouldn't suggest that you try that, however.

Raf

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RAVjets Demo team. All We Do Is Fly.

(in reply to ravill)
       Post #: 10

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 6:52:32 PM   
erbroens



Posts: 1948
Joined: 11/20/2003
From: Curitiba, Parana, BRAZIL
Status: offline 		Ditto on Raf´s comments on the takeoff technique. The F-18 rotation is super smooth if done this way.



Enrique



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E pluribus unum

(in reply to ravill)
       Post #: 11

RE: Jet Legend F-18C First Flight Issues - 6/20/2007 11:06:12 PM   
JohnMac



Posts: 746
Joined: 10/13/2002
From: Leeds, UNITED KINGDOM
Status: online 		Hi Ravill,
So whats the story with the Superhornet? I have a SM version half built and I have heard that they are more tricky to land than the C version. Is that so?
Regards,

John

(in reply to ravill)
       Post #: 12

RE: Jet Legend F-18C First Flight Issues - 6/21/2007 2:33:48 AM   
NUNU


 

Posts: 114
Joined: 8/4/2006
From: NORTH MIAMI, FL, USA
Status: offline 		hell no....the super is designed ...if you believe in scale...to fly better than the C don't get mad at me people ask the manufactuer...anyway on the super use the flaps and it wont be a problem...and yeah cg at 125mm ffrom leading edge......the super was and is my first jet.

(in reply to JohnMac)
       Post #: 13

RE: Jet Legend F-18C First Flight Issues - 6/21/2007 7:07:54 AM   
F15driver



Posts: 88
Joined: 12/7/2001
From: New Braunfels, TX, USA
Status: offline 		Raf,
Tell me more about coupling the horizontal stab to the aileron. I understand thats how the full-size F-18 is configured.
How did you couple the two and approximately how much throw did you employ on each at full deflection? It makes sense to do this but, as you know, no instruction comes with the kit as far as throw amounts are concerned.
I moved the CG to almost right onto the wing carbon fiber rod. This took an addt'l 3 oz. of lead, making 9 oz. in total with both batteries in the nose.
Will take you up on your suggestion of using the airbrake after I uncouple it from the brakes.
Thanks again your suggestions.
Rob

_____________________________

Don''t look back, they may be gaining on you!

(in reply to ravill)
       Post #: 14

RE: Jet Legend F-18C First Flight Issues - 6/21/2007 5:00:03 PM