How to make your turbine handle grass fields
 

Hey guys lm looking for tips to help those who want to fly turbines off grassfields


I know it helps when your landing gear have the ability to pivot back to help from ripping out the retracts out the wings

I just flew my old CAI Razor today with an a 18 pound AMT turbine. Even with the 20% takeoff flaps it took almost the whole runway to get off the ground.

I will ill admit when full of fuel it seems hard to push by hand. But on the stand all the wheels seems to spin very freely

any other pointers?

One of my boys falcon has bearings on his wheels on his falcon 120 and it takes off 1/4 runway

thanks

Position the jet at the very end of the runway. Brakes on, full elevator, full throttle for a few seconds until it feels like it's gonna drag the jet, release brakes, hold elevator full up until nose starts to lift, relax elevator slightly for take off and then pull up again. The key is getting the weight off the nose. You might also try not fueling up 100% to lighten the load and flying for a little less time.

Thanks I was not pulling up until 1/2 runway

Actually done more damage to my plane off tarmac but if you have Jet1As on the mains that helps reduce the loads.

Trailing link main gear is a must IMO.. Andy's short field takeoff technique is another good bit of info to go by. It helps reduce the roll out a good bit. Also make sure your brakes are fully releasing with them aired up. I know my eurosport brakes would stick if i didn't clean some of the crud out of them every few weeks. I also found a sticky brake valve to that would let about cause the brakes to drag a bit

The razor has small wheels for grass and does not come off overly quick even on pavement. I think my old razor probably took about 500' on pavement to rotate. I doubt you could put trailing links in a razor, the gear is very short, I doubt I could put them in my Raptor which is bigger than my razor was. I had a pst1300 in mine too putting out 28lbs of thrust. The biggest issue with the raptor and razor for takeoff is the forward fuel tank is really forward and quite large so the jet is very nose heavy on takeoff.

I joke with my buddies that our short grass strip is like operating from an aircraft carrier. Things that helped my jets take off are Power - as much as you can fit in there. Trailing link oleos, make sure your wheels spin as freely as a skateboard wheel. Also I run full flap on takeoff, see if you can extend your nosewheel so the bird has a slight nose up attitude on takeoff. Having a rear biased CG point helps as does extra travel on your elevator just for takeoff, you can change out the rates then when you are in the air for smoother flying.

This helps more than you would think. If you have the clearance, shim the gear 1/8 to 1/4 inch to make the nose taller

Agreed. If you can install a bigger tire, it will help. I built a little T-45, that originally was a 90mm EDF. SO... the stock tires were tiny. (1.75") But, knowing I was flying it off the grass... I installed 3" mains, and 2.5" on the nose. It looks a little goofy, but it works.


And finally.... more thrust is always nice. (lol) Is this the ECU I turned up to 152K for you?


****EDIT****

One thing to remember... on the AMT's, they calibrate on every start up. SO... you need to hold the throttle to full, for at least 6 seconds, before your flight, for the ECU to give you full power. If you are just taxi'ng out, and hitting the throttle... you may only be at 90% power.

Doing a simple run-up may get you out of the grass faster with that engine.


(Do you have a manual? I can post one if you need it)

Thanks guys. I think I'll try killing 2 birds with one stone. I have seen were a few guys add a 12oz fuel tank under the canopy. This will put a little weight behind the CG and add an extra 45sec on the clock

I flew it with the stock 142.7 rpms. I just replaced the controller with the one you helped me out with so to get the 152k I'm sure that will help.

I tried pushing the jet by hand and was very surprised how much effort it takes on the grass

if the extra thrust and fuel don't help then replacing the wheels with the kind with wheel bearings will be next.

I just oust need to make all the gear doors now. I can't believe how great this bird flys!

i got a boy who is thinking of giving me a sweet deal on a used JetCat 80 Maybee that's what this jet needs vs the AMT

This also will help greatly :phttp://www.rcuniverse.com/forum/atta...mentid=1932227

OK... well, then don't fool yourself. At 142K RPM... the AT-180 is only a 15 Lb thrust engine. Pushing it up to 152k makes it a 17.5~18 # engine. With the updated burner, and compressor... it's 19.5 #'s.

FYI: DO NOT hold the throttle wide open for a long time. The old engine will get hot at that RPM. But honestly... unless you are a total speed junky, it's not an issue.

I bet putting in the 152k ECU will make a HUGE difference.


I like the AMT engines... but the JetCat 80 will scrap over a pound of weight, and give you added thrust.

Good infos, increase size of wheels, reduced weight if possible are all going to help... More thrust also help for not just faster acceleration but to overcome wheel friction however it produce minor counter rotation or nose down effect during takeoff. Moving CG slightly backward and increase flaps can also help. Rough runway and grass is stressful to landing gear also exposure to FOD, so the goal is to reduce takeoff and landing speed. I have also issue on grass runway when height and dirt are not favorable. Also when there's no wind or at 90 deg crosswind expect a longer and faster takeoff and landing.

Here's why I want to shorten my takeoff and minimize exposure of runway debris.
http://www.youtube.com/watch?v=KdtmvjNj2tg

Like the clip. Really shows the landing gear working

Dont use full flaps. Flaps only produce lift at up to 20 %. Flaps were and are intended to induce drag to slow the plane down.
Thats the only thing they do.
absolutely no extra lift at full flap.

holding up elevator increases drag, full flaps increase drag, the thrust tube is restrictive at the back get a larger diameter tube, I would drop in a jets Munt VT80 and raise the front nose gear.

I agree a Merlin vt 80 on that airframe would be great, amts are great but very heavy a p80 will shed some weight but not a ton it's still a big engine..the latest generation 80 and 100n turbines on that airplane would be the ticket...not to mention much less thirsty than an old p80 or mercury. The AMT is not the most efficient engine, and remember the only way to get more power is more fuel keep that in mind on an airplane that doesn't carry very much of it..I don't remember how much my razor carried but I believe it was only 70 some odd ounces.
As mentioned earlier though unless your a total speed demon most of your flying will be around half throttle on that slick airframe...have fun with it, it's a good one.

Since you have brass bushing in your wheels, its possible that the wheels are twisting sideways when rolling on the grass. With the plane inverted on the bench, apply force to the wheels from the front. If the wheels are twisting.. loosen your struts and turn till the wheels are straight and then tighten. I had this problem with my Prolinks that ARE trailing links. The bushings started to give and when taxing they acted like the brakes where on. It took a lot more effort to get in the air.

Holding full up elevator + 20 deg flaps when taking off from grass/soft field is standard procedure on all full scale aircraft with tricycle landing gear. It reduces the load on the nose gear & also reduces the take off roll.

http://www.youtube.com/watch?v=YG7JdTP7XRg the CAI raptor handles grass great, as well as the Razor. With the razor, i would say the grass should not be tall as the wheels are somewhat smaller. . it DOES NOT need trailing link struts, and takes off of grass with no problems, and they land even better. If set up correctly, it will trail straight just fine on TO roll. Use no more than 25deg down flap on take off. more than that acts more as a speed brake. On take off, hold brakes, power up to full and as it starts pushing through the brakes let go and hold just slight up elevator. The plane will get on step on its own and let it do so for around 50 feet before pulling more elevator to climb. This video is how it look on board from under the fuse.

the Razor has very similar flight properties. The most important thing to get right on the Razor is the CG. If its too nose heavy, it will have a hard time breaking ground. At least this was my experience with the plane. Fun flying aircraft :)


~V~

I thought 40 degrees was recommended take off flap for razor? Without the certain amount of flap, it won't get off the ground.

Trailing links will hurt you on takeoff performance as they flex they move aft and will put more weight on the nosewheel. Nosewheel springs compressing also hurts you by putting the plane in a negative angle of attack that requires the elevator to produce more downforce to overcome= more speed required = more distance required. Proper design is the first thing-but that is mostly out of the modelers control- get the mains as close to the cg as possible so that the load on the nosewheel is small and you can get the nose up to rotate sooner. in the end good setup with wheels pointing straight and running as big of wheels as possible will help the most.

holding full elevator on take off is a recipe for a nasty surprise snap. Lifting off too soon is a major cause of crashes, I would not touch the elevator until you are at speed. A better idea is to ensure your cg is more neutral on take off, many jets have fuel forward of the cg making it way nose heavy to start with. Not good on grass. Set it up so the cg starts more where it should be if you can add tanks behind the cg and a smaller tank in front.

I mainly fly from grass. Full brake to get full power. Half flaps. A positive AOA can help but beware can cause bouncing on landing if field is bumpy.
Trailing links help a lot but bigger tires do too. Wider tires are best as well. Thin ones dig in more.

A falcon 120 has a very light wing loading. Its not a jet in the sense your Razor is. It cant be compared any more than my wifes slow stick can.

Another option is too only carry enough fuel for a 3 min flight. Should shed a pound that way.

That's the exact opposite of what I have found. Have you tried taking off on full flap vs half flap?

Same as what essyou said. Pulling it off the deck too early and snapping is much worse than a long take off run. I've seen some nice models lost that way.