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Model Forum / Radio Controlled / Helicopters / May 2007Trex 450 Autorotation
Has anyone ever had a successful autorotation with a Trex450 with wooden blades (335mm). I an use to larger 60 size helicopters and have been successful with them (Lot of energy stored in that rotor). I try with the Trex and it just drops like a rock and loosed rotor speed almost immediately. I just power back up at 25 feet and just about miss the ground. I hope I never need to do one in a situation where I can't turn the motor back on. Any advice would be helpful. > Has anyone ever had a successful autorotation with a Trex450 with wooden > blades (335mm). I an use to larger 60 size helicopters and have been [quoted text clipped - 3 lines] > ground. I hope I never need to do one in a situation where I can't turn > the motor back on. Any advice would be helpful. I am not an expert but do you have enough negative pitch?? About 10 Degrees. But before I even get to respond and go to negative pitch the rotor has slowed so much that it becomes impossible to get any cyclic response. Rotor RPM about 2200 before I shut the motor down. >> Has anyone ever had a successful autorotation with a Trex450 with wooden >> blades (335mm). I an use to larger 60 size helicopters and have been [quoted text clipped - 4 lines] >> the motor back on. Any advice would be helpful. > I am not an expert but do you have enough negative pitch?? >Has anyone ever had a successful autorotation with a Trex450 with wooden blades (335mm). I an use to larger 60 size helicopters and have been successful with them (Lot of energy stored in that rotor). I try with the Trex and it just drops like a rock and loosed rotor speed almost immediately. I just power back up at 25 feet and just about miss the ground. I hope I never need to do one in a situation where I can't turn the motor back on. Any advice would be helpful. Forward speed and not too much negative pitch. Too much negative and you're adding drag to the blades. Forward speed will "bank" energy you can use for the flare and setdown. Dropping the nose will kill your RPM. Keep the nose up but not so far as you kill your forward momentum. The harder your flare at the bottom, the more you'll load up the head and generate from "free" RPM. Just don't balloon when you flare.. Pull the nose up to stop the descent and then bleed off speed while paralleling the ground. Once you're almost stopped, level the skids and feed in the collective to cushion the landing. You're going to need to be less than 2' off the ground at the end of the flare or it's gonna drop to the ground. What's your headpseed in a hover? If you're running low-mid 2000s, you're "behind" the curve for autos in a small ship like this. 450s are hard to auto, but if you get the headspeed up near 3000 RPM you've got a bit more energy stored before you enter the auto. I am at 2200 RPM in a hover. That is the recommended max. on the package the blades come in. >>Has anyone ever had a successful autorotation with a Trex450 with wooden >>blades (335mm). I an use to larger 60 size helicopters and have been [quoted text clipped - 22 lines] > are hard to auto, but if you get the headspeed up near 3000 RPM you've > got a bit more energy stored before you enter the auto. >I am at 2200 RPM in a hover. That is the recommended max. on the package the >blades come in. Which blades? The Pro Woodies will tolerate RPMs in the neighborhood of 3000 but I STRONGLY suggest you epoxy the grip reinforcements to the blades and BALANCE them before you spool up. I fly the Pro Woods or Maverik M4s on my 450SE at 3000RPM in a hover. I have yet to shed a blade. That's *MY* experience and I suggest you proceed with caution if you bump the head speed up. The Align CF blades (not the carbon "look" or those awful plastic "carbon" blades will take 3000+ RPM easily. My 450SEV2 runs the Align CF blades at a tick over 3100 RPM in a hover. Zero problems thus far. Yeah, what he said! :-) -10 degrees is WAY too much. -4 to 5 should be a maximum I would think. The little birds simply don't carry the rotor inertia that the bigger ones do so autos will always be problematic on them but they can do it if needed and the pilot keeps his act together. As far as rpms go, don't think that just because you're running 3000 rpm in powered flight, that that's what you're going to get in autorotative flight. Measuring autorotative rpms in something like a T-Rex would be almost impossible. Things just happen too fast. I can tell you that, regardless of how fast you're turning that 30 to 60/90 size bird in powered flight, once you enter the autorotation, you're going to be down around 1450 within the first 3 to 5 seconds. We've tached about a dozen different models and this worked out to be the case no matter what. We had a 60 size bird spinning between 1950 and 2000 rpm, flipped throttle hold and they hadn't dropped 10% of their altitude and the rotor stabilized at 1450, give or take a little depending on where the pilot was holding the collective. I can't imagine that the micros are doing much better. JMO! :-) Fly Safe, Steve R. >>Has anyone ever had a successful autorotation with a Trex450 with wooden >>blades (335mm). I an use to larger 60 size helicopters and have been [quoted text clipped - 22 lines] > are hard to auto, but if you get the headspeed up near 3000 RPM you've > got a bit more energy stored before you enter the auto. >Yeah, what he said! :-) > [quoted text clipped - 17 lines] > >JMO! :-) Now that's interesting. I think I might check that out myself when I fly Saturday. I'd be surprised if the smaller ships didn't turn a bit faster in an auto... >>Yeah, what he said! :-) >> [quoted text clipped - 26 lines] > fly Saturday. I'd be surprised if the smaller ships didn't turn a bit > faster in an auto... After re-reading my statement and then your response, I'd like to clarify that I don't think the micro is getting down to 1450. What I wrote "could" be interpreted that way and it's not what I meant. I'll I was trying to say is that I'm not sure that the micro will maintain that 3000 rpm, powered rotor speed in a stable autorotative state. I could certainly be wrong about that but as explained above, my experience with the larger birds would imply that it probably won't. Kevin, if you tach a 30 or larger model in powered flight and then in an autorotation, I'd be very interested in what your results are. I'm sure a lot of that depends on the pilots techniques. My friend and I love doing auto's. We both tend to play the collective a bit on the descent. We don't bottom out the collective and let it drop like a rock and we don't try to float them too much either. If you and whoever winds up helping you in this does things differently, you'll certainly get different results. If you manage to get a solid reading on a T-Rex in a stable autorotative state, I'd "really" like to see what numbers you come up with. You'll have to start high as those little suckers drop like a rock when you cut power! :-) Fly Safe, Steve R. You are not kidding when you say those little suckers drop like a rock ! >>>Yeah, what he said! :-) >>> [quoted text clipped - 55 lines] > Fly Safe, > Steve R. I had 335mm blades 100 feet altitude 15 MPH head wind 35 MPH forward speed 5 Deg. negative pitch and this thing was 4 feet from the ground and falling like a rock with no inertia left in the rotor. Powered back up just in time. It fell in less then 2 sec. I have come to the conclusion it is impossible to auto a Trex 450. I have a Blade CP Pro and can just about stop the rotor with no throttle in normal mode and this think just floats around. The Trex 450 is a brick. > You are not kidding when you say those little suckers drop like a rock ! > [quoted text clipped - 58 lines] >> Fly Safe, >> Steve R. >I had 335mm blades 100 feet altitude 15 MPH head wind 35 MPH forward speed 5 >Deg. negative pitch and this thing was 4 feet from the ground and falling [quoted text clipped - 3 lines] >with no throttle in normal mode and this think just floats around. The Trex >450 is a brick. I saw several folks auto their 450s successfully this past weekend at a local fun fly. I'd almost be willing to bet -5 degrees is too much to keep driving the rotor blades or you let the nose drop - or a combination of both.. >>I had 335mm blades 100 feet altitude 15 MPH head wind 35 MPH forward speed >>5 [quoted text clipped - 12 lines] > to keep driving the rotor blades or you let the nose drop - or a > combination of both.. Letting the nose drop is a definite no-no. You do that and you'll loose the airflow that's supposed to keep the rotor turning. The rotor will then slow down "RIGHT NOW!!!" and you'll have "NO" chance of recovering without the reapplication of power. The model has to be kept level at the very least, slightly nose high would be better. Enter the auto from moderate forward flight (that's as it appears to travel over the ground) with a "healthy" head wind. Lower the collective with power still applied and "then" flip into throttle hold. Also make absolutely sure that the collective curves and the cyclic trims are matched between throttle hold and whatever flight mode you typically enter autorotations from. That will insure that the model doesn't do anything unexpected when you change flight modes. Whether or not -5 is too much negative pitch, I'm not sure, but I tend to agree that it certainly could be. I don't think I'd go any lower than that on an initial setup. FWIW! ;-) Fly Safe, Steve R. PS: Kevin, have any look taching that little sucker yet? :-D >PS: Kevin, have any look taching that little sucker yet? :-D I've been trying, but each time I hold the viewport on the tach up to my eye, I lose control of the helicopter. :) >After re-reading my statement and then your response, I'd like to clarify >that I don't think the micro is getting down to 1450. What I wrote "could" [quoted text clipped - 3 lines] >about that but as explained above, my experience with the larger birds would >imply that it probably won't. Oh, I'd be willing to bet large sums of money that 3000 RPM headspeed won't remain in an auto. My point was that high speed would give you a little more "breathing room" to get established in the auto before RPM decayed to the point where the heli is no longer generating any lift. Running 2200 RPM might give you (and I'm just tossing out number here) 2 seconds to stabiize the auto where that extra 800 RPM at entry might give you 3 seconds. >Kevin, if you tach a 30 or larger model in powered flight and then in an >autorotation, I'd be very interested in what your results are. I'm sure a [quoted text clipped - 3 lines] >float them too much either. If you and whoever winds up helping you in this >does things differently, you'll certainly get different results. Well, I can tell you my Trex600 in an out of ground effect hover tachs out right about 1900RPM on those crappy Align 4400 batteries. I haven't checked it with the new Flightpower EVO25s I just got, but will try to do so this weekend. My buddy's 600 on 8S and a Neu motor tachs out at 2200 RPM in an OGE hover. My 450SE is somewhere around 2900 RPM (tached by my 10 year old so results are subjective at best. heheh) and my SEV2 is around 3100 RPM. The SE has the 430L motor and 15C Thunderpower batteries and the V2 has the new 430XL motor and Align's 22C packs. Same pinion, throttle and pitch curves on both. >If you manage to get a solid reading on a T-Rex in a stable autorotative >state, I'd "really" like to see what numbers you come up with. You'll have >to start high as those little suckers drop like a rock when you cut power! >:-) I'll try and get some results this weekend. I'm going to a funfly Saturday but not sure if I'm going to bring any helis or not. Those things make me nervous about keeping an eye on my gear.. Sunday is Mother's Day and I'm not sure I can get away to burn off a few packs or if I can find someone to tach the heli for me. To be honest, I'm not sure I want to try an auto with the 450s. heheh I have a Kalt Gas Baron Alpha, Weedwacker Engine and 10 oz. of lead in the ends of the rotor blades. I had this Heli since the late 80,s never crashed. I can put this baby in a 10 foot hover cut the engine to idle and auto it straight down nice and slow. It takes about 40 sec. for the rotor to stop when on the ground and you go to idle. Into a head wind you can actually turn and fly around in an autorotation. So when I go to my Trex 450 I an coming to the conclusion that it is impossible to auto this heli. >>>Yeah, what he said! :-) >>> [quoted text clipped - 55 lines] > Fly Safe, > Steve R. >I have a Kalt Gas Baron Alpha, Weedwacker Engine and 10 oz. of lead in the >ends of the rotor blades. I had this Heli since the late 80,s never [quoted text clipped - 3 lines] >actually turn and fly around in an autorotation. So when I go to my Trex >450 I an coming to the conclusion that it is impossible to auto this heli. Yup! Large helicopter + heavy rotor blades = long hang times at the bottom of an autorotation. Great fun! :-) The T-Rex (and similar) models aren't impossible to auto. I've seen too many folks do it. However, you simply "do not" have the rotor inertia to cushion the landing much and you have to take that into account. A "healthy" wind to auto into is also a very good thing. I'd never deliberately attempt an auto on a calm day with one of these birds. I've only tried one autorotation with my HDX450. Everything happened "very" quickly but for the most part, the approach was good. I even got a nice spool up on the flare but I didn't get it level enough for the touchdown and was rewarded with a healthy boom strike for my trouble. I haven't tried another one yet but probably will eventually. FWIW! :-) Fly Safe, Steve R. |
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