Bob Cotsford Posted August 9, 2018 Share Posted August 9, 2018 Possibly blown wing effect comes into it but I think the propwash over the tail surfaces has more bearing on how a landing turns out. One of the issues I've encountered in converting from glow to electric on 40-120 size models is the dramatic loss of thrust you get on low throttle with electric compared to glow which has resulted in me making some pretty heavy landings due to lack of elevator sensitivity at the flair combined with a sudden loss of airspeed. I could cope with this on a glow deadstick where I know I need extra airspeed, but I'm still recalibrating my mind to the poor low end throttle response on electric. I need to follow Jon's lead and add some throttle curves! Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted August 9, 2018 Share Posted August 9, 2018 'Why do some models have a wide flight envelope and others don't?' Design:- wing loading, aerofoil used, available engine power, high lift devices fitted, configuration, aspect ratio, intended purpose, to name only a few. Edited By Piers Bowlan on 09/08/2018 14:04:58 Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted August 9, 2018 Share Posted August 9, 2018 TWS, I was not implying you or anyone else had missed the point, just a different view. Is it the model or the thumbs/fingers on the sticks? I am by no way one of them, but there are pilots out there that pull off outstanding landing on a consistent basis seemingly with anything they fly Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 9, 2018 Share Posted August 9, 2018 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted August 9, 2018 Share Posted August 9, 2018 Posted by Bob Cotsford on 09/08/2018 13:57:22: Possibly blown wing effect comes into it but I think the propwash over the tail surfaces has more bearing on how a landing turns out. One of the issues I've encountered in converting from glow to electric on 40-120 size models is the dramatic loss of thrust you get on low throttle with electric compared to glow which has resulted in me making some pretty heavy landings due to lack of elevator sensitivity at the flair combined with a sudden loss of airspeed. I could cope with this on a glow deadstick where I know I need extra airspeed, but I'm still recalibrating my mind to the poor low end throttle response on electric. I need to follow Jon's lead and add some throttle curves! Having been caught out with this one Bob, as I have the privilege to test fly and trim most models at my patch, I soon realised that though I/C are usually set with a healthy 2000rpm idle at throttle stick fully down Their electric counterpart is at zero thrust, at full stick down I have adapted to this by leaving some stick on as I make an electric arrival Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 9, 2018 Share Posted August 9, 2018 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Geoff S Posted August 9, 2018 Share Posted August 9, 2018 I must be very insensitive because I've never noticed a problem with electric power. My conversions usually have a prop at least as big as the specified glow engine. My Moth has a 13x6.5 prop which is a lot bigger than on the 40 size glow the model was designed for. Moreover I know that when I open the throttle after the 'cut' part of the approach to lose height, which could be 10 or 15 seconds, it will respond perfectly. If you want to keep the prop turning more than the normal windmilling then there's no reason why you shouldn't leave the throttle open a touch. Geoff Quote Link to comment Share on other sites More sharing options...
Nigel R Posted August 9, 2018 Share Posted August 9, 2018 Good thread gents. For me I find the easiest landings come with a steep approach and enough control to change that angle a bit and get a decent flair, the two big factors for me come down to drag and loading, which sort of goes... Low drag, low loading = power off to try and get the glide as steep as possible, flair with a tickle of throttle, the easiest to land I think Lots of drag and low loading = power on (probably to make headway against wind) and flown down at whatever angle is needed, the flair will be cake with a tiny bit of a blast from the throttle. Foam 3d models, a lightly loaded bipe, a lightly built STOL type, etc. My depron 3d model glides at about 45 degrees because of the drag and cannot flair without power as it simply stops and stalls (although, so light it bounces) I have to physically "fly it at the ground" in any kind of wind. Lots of drag and high loading = power on, no question at all, and still coming down quite steep, with a blast of throttle to get the flair right. Warbird types with good flaps, heavy bipes, that kind of thing, easy enough with practice but not for learners as it can go pear shaped quite easy with the loading being high. My small Bi Fly is like this. Probably a lot like BEB's Kyosho Pitts. Low drag, high loading = crikey. Coincidentally to this thread I just spent the last session doing nothing but shooting touch and goes with my electric trainer which is low(ish) drag (only the U/C really sticking out) and low loading, its a piece of cake to land, and a circuit + touch and go can all be done in the confines of the field (60m square?); it can just about be held at a high AoA balanced on the throttle and elevator (almost like a 3d model in a harrier) - it is one of the easiest models I have ever had to pull off a good landing. OTOH I have retired (for now) my heavy (well, not especially heavy by old style glow model standards), slick 2 stroke glow aerobat, until I can fit flaps, as our field is too simply small for its glide path (unless I am on right down at near stall speed and then I have no directional control options). Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted August 9, 2018 Share Posted August 9, 2018 Posted by Peter Miller on 09/08/2018 11:44:37: There was a similar event over thye Atlantic when an airliner coming across from North America glided for hundreds of miles to land on one of the islands in the Atlantic. I watced the program may years ago but cannot remember the details. I know the problem was caused by thye confusion between pound, and gallons. I must see if I can google that one Air Transat Flight 236 think, landed on the Azores. Quote Link to comment Share on other sites More sharing options...
J D 8 Posted August 9, 2018 Share Posted August 9, 2018 In the early day's of flight with the Royal Flying Corps cut and glide was the accepted landing method due mainly to the possible unreliable pickup of the rotary engines. Any pilot seen motoring in [ rumbling in it was then called ] would have to stand a round of drinks at the mess that night. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted August 9, 2018 Share Posted August 9, 2018 I think the only way of controlling the engines was by cutting the magneto. The carburretors were very crude and didn't incorporate a throttle. The aircraft were also prone to nosing over. Flying was a dangerous business in those days. Geoff Quote Link to comment Share on other sites More sharing options...
J D 8 Posted August 9, 2018 Share Posted August 9, 2018 And painful to,that darn engine blip button could deliver the pilot some nasty electric shocks! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 10, 2018 Share Posted August 10, 2018 Posted by Geoff Sleath on 09/08/2018 15:22:11: I must be very insensitive because I've never noticed a problem with electric power. My conversions usually have a prop at least as big as the specified glow engine. My Moth has a 13x6.5 prop which is a lot bigger than on the 40 size glow the model was designed for. Moreover I know that when I open the throttle after the 'cut' part of the approach to lose height, which could be 10 or 15 seconds, it will respond perfectly. If you want to keep the prop turning more than the normal windmilling then there's no reason why you shouldn't leave the throttle open a touch. Geoff More than no reason why you shouldn't leave the throttle open a touch - more a case of why don't we set a "flight idle" on our electric models? I hate to see electric models (especially scale ones) taxi out, stop their props while completing the turn into wind and restart after a second or two for the take off run. Maybe a bit "anal" but I always make the effort to keep the prop turning and some of the comments in this thread are prompting me to doing a little programming along these lines (although in general, my scalish models tend to be IC powered). It will be interesting to see if there is a noticeable difference in fine control of the flare... Quote Link to comment Share on other sites More sharing options...
Chris Jones 7 Posted August 10, 2018 Share Posted August 10, 2018 Posted by Martin Harris on 10/08/2018 00:20:08: More than no reason why you shouldn't leave the throttle open a touch - more a case of why don't we set a "flight idle" on our electric models? I hate to see electric models (especially scale ones) taxi out, stop their props while completing the turn into wind and restart after a second or two for the take off run. Maybe a bit "anal" but I always make the effort to keep the prop turning and some of the comments in this thread are prompting me to doing a little programming along these lines (although in general, my scalish models tend to be IC powered). It will be interesting to see if there is a noticeable difference in fine control of the flare... Interesting - I’ve always set up my electric models so the prop is always spinning at zero throttle and requires the arming switch to be flicked to stop it. I do this even on belly landers simply flicking the switch at 1ft above landing. I seem to remember reading somewhere that a spinning propexhibits a greater braking effect that a stopped prop? Which may be why I fly with power on when landing on most models? Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted August 10, 2018 Author Share Posted August 10, 2018 Intriguing point, Chris. I seem to recall that about spinning props, too, but I didn't see any explanation. I think it might be the ability to spin (i.e. windmilling - the prop itself is not braked) that gives a braking effect. This is logical, because the prop is taking energy from the air to produce the rotation. I can't see a simple explanation as to why using motor power to provide a spinning prop should have any additional braking effect over windmilling. Presumably, the braking effect is zero when the propeller speed is exactly matched to the forward motion of the air. Looks like the scientific answer is: it depends... Edited By The Wright Stuff on 10/08/2018 09:07:20 Quote Link to comment Share on other sites More sharing options...
Chris Jones 7 Posted August 10, 2018 Share Posted August 10, 2018 Haha! So still nothing’s clear other than an aeroplane looks bloody silly coming in to land without its prop spinning! I also figure that on an ic model if the props not spinning it’s clear there’s a problem and people may allow more airspace for you (yes I know deadstick should be called). Keeping the prop spinning makes it clear the engine/ motor is running and all is, relatively, well. Beingbas most people at my club fly ic I figure I’ll make my electric models look as much like expected as possible. But This is a bit off the original topic. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted August 10, 2018 Share Posted August 10, 2018 Posted by Martin Harris on 10/08/2018 00:20:08: More than no reason why you shouldn't leave the throttle open a touch - more a case of why don't we set a "flight idle" on our electric models? I hate to see electric models (especially scale ones) taxi out, stop their props while completing the turn into wind and restart after a second or two for the take off run. Maybe a bit "anal" but I always make the effort to keep the prop turning and some of the comments in this thread are prompting me to doing a little programming along these lines (although in general, my scalish models tend to be IC powered). It will be interesting to see if there is a noticeable difference in fine control of the flare... That thought had occured to me too Martin, particularly for some larger foamies which seem to stop dead in the air on closing the throttle. In the past I've set an 'idle up' on one or IC two models where they showed a tendency to go deadstick after particular manouveres. Time to try it on a leccy. And yes, it does look odd when a scale model taxis out then the prop stops prior to taking off! Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted August 10, 2018 Author Share Posted August 10, 2018 Posted by Bob Cotsford on 10/08/2018 11:56:22: And yes, it does look odd when a scale model taxis out then the prop stops prior to taking off! Not as odd as when the prop stops on an I.C. scale model, and then a 36 foot giant lumbers over to take it back to the pits... Quote Link to comment Share on other sites More sharing options...
eflightray Posted August 10, 2018 Share Posted August 10, 2018 What's the usual question from a non-modeler watching you fly ? "Does it crash if the engine stops ?" It's mostly about wing loading, and where in the sky the engine quits. An up wind pass and a cut, really makes you think. Turn ?, or just keep straight and hope. That's why I love electric, my 'engines' have inflight electric 'starters', (most of the time). Lightweight always has benefits. Ray. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 12, 2018 Share Posted August 12, 2018 Posted by eflightray on 10/08/2018 14:53:20: What's the usual question from a non-modeler watching you fly ? "Does it crash if the engine stops ?" Seems an unlikely question from a non modeller. Have you been prompting them? My experience in something like order of popularity: Howmuchizzit? How fast does it fly? How far away can you control it? How high can it go? Did you build it yourself? How often do they crash? (also the most common question from passengers/first time pupils in full sized gliders - my answer was "usually just the once!" ...and while on the subject, "will it crash if the wind stops?" was a close second. How can you bring yourself to fly something that takes so long to build? But I can honestly say I don't recall any visitor even considering an engine failure... Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted August 13, 2018 Share Posted August 13, 2018 I was slope soaring a simple 2 ch flying wing (Zagi) from the South Downs a few years ago. A woman came up to me and said that she had been watching my plane fly and said 'It is so quiet, where is the engine?' I said it doesn't have an engine, it is a glider. 'But', she said, 'you have a controller, how does it fly?' I said that it is just soaring in the rising air that is blowing up the slope. The 'controller' is just so that I can steer the model around the sky. It will continue to fly for as long as the wind blows (almost). She looked at me totally non-plussed with a look of bewilderment and scepticism. In her eyes I was clearly lying, as what I was doing was impossible; magic was at play! Edited By Piers Bowlan on 13/08/2018 09:32:19 Quote Link to comment Share on other sites More sharing options...
Geoff S Posted August 13, 2018 Share Posted August 13, 2018 I had a similar conversation when I was sailing my 1 metre yacht on my own. The woman couldn't understand how it could sail in any direction but dead down wind (I didn't attempt to explain how it got back up wind!). She did agree, however, that it looked beautiful so she was forgiven Geoff Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 13, 2018 Share Posted August 13, 2018 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
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