View Full Version : turbulence - what turbulence?

6th January 2011, 21:42
Is there a flaw in this logic:
My Blade had a wing area of 15.6 sq m, and with just me in and a bit of fuel weighed 254 kg (582 engine). This gives a load per sq m of 16.3
The Dragonfly with just me and full fuel and some bits and pieces will weigh 203kg (OK Paul I'll find a way of kicking out 3kg). and it will be using a 12.8 sqm wing - hence wing loading 15.9
ie not much difference between the two .... so I should find it just about the same to fly the Dragonfly in turbulence as I did the Blade ? (perhaps it might even be easier as the Dragonfly will be hitting the turbulence at 38mph whereas the Blade was hitting it at 62mph)

.... and a connected question ... what about ground handling? perhaps this is where absolute mass is more important, and the more weight you have in the trike the better as it's less likely to tip (ie the Blade would be better). On the other hand is the controllability directly related just to the wing area -so the smaller Combat wing will be easier to manhandle on the ground than the much bigger and heavier Blade wing?


7th January 2011, 09:00
In the air, span counts as well as wing loading. Try working out the span loading of the two and compare.

On the ground height of wing and height of CofG counts as well as area and (again) span.

Laurie (2)

7th January 2011, 13:06
Yes I agree with evrything you say Paul .... but Peterlee airfield has a habit of turning very turbulent while you are away from the field. If the wind strengthens to even 15mph out of the south west, it boils across the village and makes landing an adventure. I got quite used to it in the Blade and after some horrendous chucking about at 100 ft or 50 ft it would usually smooth out in the bottom 20ft. If the Dragonfly is only as bad as the Blade in these circumstances I will be happy enough.

With regard to the span - I think it's possibly 1.5metres less, so on 10.6m That means the Blade has a loading perm of span of 24 and the Dragonfly has 22.5 - Again this looks similar enough. By the way don't forget I'm am comparing the Blade lightly loaded (just me) with the Dragonfly at full load. For ground handling - I did think that the hangpoint of the Dragonfly was perhaps a couple of feet higher than it needed to be, but I guess that's dicated by where they have to put the base bar of the wing. The trike is very low and since I perosnally will be a large part of the weight of the machine, it's possile that the CofG of the dragonfly is actually lower than the Blade. I suspect that the wheelbase (track) is also very important for ground handling, and in this respect the Blade probably scores. Just as an aside on ground handling by the way, my instructors taught me to hold the into-wind wingtip down near the ground. I later discovered that providing you concentrated hard it was much better to do the ground handling with the wings absolutely level. It will be interesting to see if this technique transfers across to the Combat wing with its upstanding winglets.

Paul Dewhurst
7th January 2011, 22:40
Not sure I agree that span loading is a good indicator of handling. It is a good indicator of glide and climb performance though. Handling is a complex balance of stability, ease of control, control effort, power etc.

Comparing blade with dragonfly is really apples and oranges, and a totally different experience - that Paul explains well. That tricky crosswind might be tough in blade and too much in a dragonfly - but dragonfly will land into wind maybe somewhere on the airfield that the blade couldn't. Dragonfly will require more care on the ground especially when you are not in it.. Be careful wheeling it around and tie it down well!

I think that the dragonfly excels in sheer joy of flight ( we can't believe the response to the motprfloating video!) and that local bumble suddenly has extra dimensions, and a longer trip, more satisfaction. And satisfaction too compared to a 582 blade in that one hours worth of fuel = 4 now! And as for permit and mod fees, organising inspectors and check pilots.......

Only piss off is forgetting to lower the undercarriage for landing - doesn't do much damage, but if your mates are looking.. !


8th January 2011, 17:08
Yes - don't get me wrong guys. I'm not buying the Dragonfly for touring round western Scotland - well I might be but if I do I'd be more likely to take it in the car up to Oban. There's some nice open country and small ridges within 10 miles of our airfield - good area for playing around after work in the summer. But slightly further away are the Cleveland Hills and the Pennines - probably 30-45 miles. Now there is no way I'm going to de-rig the aircraft take it by car and re-rig it at Carlton bank (say), so I have to plan to do some slogging away at as fast as the Dragonfly feels comfortable, in order to get to some of these playgrounds. If it turns crap while I'm away I can land on the emergency runway or even the taxiway at Peterlee, so I'd already worked out that crosswinds are not such a problem as might have been the case with a heavier trike.
Regarding tying it down - Has anyone got any experience of the aircamp stuff - they had a stand at the Flying show? I know it's expensive but it's extremely light and compact. http://www.air-camp.biz/rootsystem1.html

8th January 2011, 17:33
Paul said "only poss off is forgetting to lower the undercarriage for landing - doesn't do much damage, but if your mates are looking.. !"
Now you've got the electric retracts, I would have thought it would be reasonably easy to design a little circuit with a proximity sensor that flashed a big red light if it detected anything at less than say 30ft below the trike, and the undercarriage switch was in the 'up' position. Any electronics wizards on here ?

Mike Cowlishaw
8th January 2011, 18:20
Exactly which 'proximity sensor' did you have in mind?

8th January 2011, 18:27
dunno mike - must be summat out there. The motion detectors on my 4.99 outdoor lights seem to pick things up at the right sort of range, maybe one of them would do.

Mike Cowlishaw
8th January 2011, 18:36
Those motion sensors pick up moving warm bodies; not quite how I'd describe the average runway at this time of year :-).

However, the laser distance measurer in your local toolshop might do the trick. Maybe worth pointing one down on your next landing and seeing if it reports plausible height?


8th January 2011, 19:05
ah - right. I could take the dog dangling on a very long lead, then as it approached the bottom of the aircraft the body heat detector might pick it up. Wow lasers sound good - I guess they don't output a specific signal at a certain range though?

Mike Cowlishaw
9th January 2011, 05:47
Probably not (signal at a range) ... but I haven't checked. The ones in airliners call out the height as the 'plane gets near the ground. That bit's relatively easy. I'm curious as to whether the devices would work moving fast across grass/tarmac.


Kevin Armstrong
16th January 2011, 05:27
We use Leica Distos, they will give out a continuous reading, but a bit expensive to cannibalise! Won't an old camera Auto-focus do?

Alternative is a height warning off the altimeter, dunno how you do that.

Or a barometric switch; they use these in diesel vehicles to pressure-compensate the engine fuel supply, Google 'Barometric Switch' for suppliers, but you'd need to zero it for changes in ambient baro pressure every time you departed.

Maybe trail an old hang-glider batten off the keel with a micro-switch to trigger the extend at the root, but would it extend quickly enough? :confused:

Maybe you should abandon the idea of flying if you're that absent minded Mike, and flog it off cheap to me...