Wingloading and turbulence

[Biggles]

I was under the understanding that the higher the wing loading the less effect of turbulence. Up to a point I observe that when flying but I have noticed that about 15-20mph above cruise speed the turbulence gets worse with the higher airspeed. Has anyone else observed this or could it be a characteristic unique to the wing? Spirit15 wing by the way.

[Tracer]

I have also experienced the ssame thing. When I reach around 15 - 20 mph, above normal cruise, there is a unnerving instability in the wing. I have and Aquilla 2 wing!

[KFA]

Eish. Its just logical that turbulance will be worse at higher aisrpeed. You don't want to bulldoze through the bumps, it's better just to ride the waves or wallow through them. You can easily exceed the max structural capacity (or G loading) of the wing at high speeds in turbulance even more so if the plane is loaded near or at MAUW. Read the owners manual and see where the published Vno or Va of the wing is. You will most likely find that at 20mph ABOVE cruise that you have already exceeded Vno and that Va is at or below cruise speed. In turbulance the plane should be flown at Va(maneuvering speed) There is a very lively and interesting discussion on avcom regarding Vne and so on. See
http://www.avcom.co.za/phpBB3/viewtopic ... 44&start=0
http://www.avcom.co.za/phpBB3/viewtopic.php?f=9&t=63481

[kloot piloot]

15 - 20 mph above cruise in a trike in turbulence is not healthy. In fact it is dumb, yet some instructors tell students to "pull in" when in turbulence. Bullsh@t

Without wanting to start a debate, turbulence is a friend. But you need to understand it. As a hang glider pilot myselve, we LOVE to start flying only when "turbulence" starts.

Rules to fly turbulence:

Make sure you can fly your trike in smooth conditions hands off the control bar
Hands off, your trike wing should (MUST) be trimmed to fly straight
Hands off, your wing should fly at the manufacturers cruise speed (if you fly single)

Try the above and tune your wing on the ground untill you can fly in smooth air with your hands off the bar.

All these flights should be done with your RPM at a steady cruise RPM.

Now advance to a slight turbulence flight and let GO of the control bar ! Keep your hands close to the bar, but do not touch. The balanced wing does everything for you ! It (the wing) WILL fly itself. Make slight corrections, lightly with your finger tips, but allow the bar to move arround on its own. The wing has been designed to fly without imput. Trike wings are awesome !

Now, important, when you get to rough thermal (turbulent) flying, you at least know where the neutral hands off position of the bar is, should be. Pull in slightly (and slightly is the word !!) 5 mph above the neutral cruise and allow the bar to float left and right but keep the pitch in control.

A lot of pilots tend to pull the bar in all the way in turbulence. DON"T !!! You stretch your sail, make the turbulence worse on yourselve, and sell the plane after that flight. Let the plane go up and down, control your speed 5% above neutral and keep the controlbar in control with small fingertip movements.

Although I make it sound easy, there will be times when you got to reign in the horse. A thermal might want to throw your wing 45 degrees bank, pull it back to where you feel safe.

But never, NEVER over-fight a plane in turbulence - it will only fight back twice as hard as you.

And remember, even in turbulence, if you let go of the bar, it WILL go back to neutral (that safe little plce).

Enjoy, and next time when that bliksem throws your wing to the right, bliksem it left and voilla, if you keep it there you will find yourselve in a thermal. Climb and enjoy !

[JCH]

Thanks for the info provided.

I wanted to start a thread on this topic and there it was already with all the questions I had already answeredm
Very conflicting arguments out there when you discuss it with fellow flyers!
Safe flying!

[KFA]

15 - 20 mph above cruise in a trike in turbulence is not healthy. In fact it is dumb, yet some instructors tell students to "pull in" when in turbulence. Bullsh@t

Agree. Those instructors should get a refresher.

Wing loading is defined as the loaded weight of the aircraft divided by the area of the wing. I think the important question to ask is what is the effect of the load factor on the wing at speed. The amount of excess load that can be imposed on the wing depends on how fast the airplane is flying. At slow speeds, the maximum available lifting force of the wing is only slightly greater than the amount necessary to support the weight of the airplane IAW 1G flight. Consequently, the load factor should not become excessive even if the controls are moved abruptly or the airplane encounters severe gusts. The reason for this is that the airplane will stall before the load can become excessive. However, at high speeds, the lifting capacity of the wing is so great that a sudden movement of the bar or a strong gust may increase the load factor beyond the aircraft safe limits. Because of this relationship between speed and safety, certain maximum speeds have been established. Each airplane is restricted in the speed at which it can safely execute maneuvers, withstand abrupt application of the controls, or fly in rough air. This speed is referred to as the design maneuvering speed or Va.

[Biggles]

My cruise speed is 50mph, wing specification states a cruise range of 50-70mph with VNE at 90mph. So I am still well within the advertised cruise range for the wing and no where near the VNE. I take it Va will be stated cruise range.

I think that a sweeping Bullsh$t with regards pulling the wing in in turbulence is wrong.

Turbulence is not only thermal. You get Orographic that can have a wing shear component as well as sink. In this case some excess airspeed might be handy. Flying with wing at near neutral in these conditions could see you coming a cropper. Maneuvering close to VNE in turbulence may cause damage.

When low level it is also handy having some extra airspeed.

So when flying at a higher speed why would the wing feel more susceptible to turbulence.

[kloot piloot]

Biggles, I did not say pulling in in turbulence is wrong, read on what I said. You have to pull in. But what I explained, and what Kitplanes also explained in detail, is how to determine how much to pull in.

It is not just a "pull in untill you are happy" answer. It is more scientific. It has to do with trimspeeds, Va, manufacturer specs etc.

Speeds in turbelence are safely determined to try and keep you away from the extremes, namely stall or Vne.

[AndyG]

Guys read the thread on VNE on Avcom and see the dangers of flying outside the parameters.

[Big-D]

Agree with Kloot Pilot 100% - I used to hate turbs and pulled bar in without even realising once things got bumpy

Dieselfan flew backseat with me once and pointed out ot me that I was pulling once things get turbulent - I did not even realise that I did this, I relaxed on the bar and noticed right away that the ruff stuff felt better.

Per Wikepedia - Wing loading is the loaded weight of the aircraft divided by the area of the wing. Wing loading also affects gust response, the degree to which the aircraft is affected by turbulence and variations in air density. A small wing has less area on which a gust can act, both of which serve to smooth the ride.

So smaller wing should be more stable - Or is it? My Blade wing is rather big at 15.6sq meter yet I find it smoother in turbs than the other trikes I have owned

So is a smaller wing easier in turbs? I dunno - Thoughts?

D

[KFA]

The big thing here is that your wing loading doesn't increase with speed . You still have x amount of kg force per sq cm(Your total weight). You are still flying 1g flight, only faster. The disadvantage now is that when you hit terbulance, there is a positive change in flight direction. This force acting on the wing is magnified by the factor of speed (i.a.w g loading) and then the loading increases or decreases ( + or - g's) which in most instances is bad for you airfarme.

So the simple answer is still the same, if you fly faster you will be effected more by the terbulant air, making the ride bumpy.

[Biggles]

So increased airspeed does not increase wing loading?

[KFA]

Read this
http://www.mountainflying.com/Pages/mou ... rb_va.html

[kloot piloot]

Excellent article Kitplanes !

So increased airspeed does not increase wing loading?

Hate to answer you like this Biggles, but : Yes and No

Example 1: You fly straight and level (at 1 G-force) at cruise speed. Your all up weight is 140 kg and the wing surface is 14 m2. Therefore 10kg spread over each 1 m2 of the wing = 10kg/m2.

Example 2: As above, still at cruise speed, but now you hit an upwards "bump" enough to make the plane pull 2 G's momentarily. All up weight therefor went up from 140kg to 280 kg, albeit momentarily. The wing loading shot up from 10kg/m2 to 20kg/m2.

Example 3: If you were flying 25% faster than in example 2, the temporary G force would probably also be 25% more and the load on the wing would have increased to 25kg/m2.

Therefor: Increased airspeed does not increase wing loading (in smooth air). Increased airspeed will however result in increased wing loading in turbulence.

Big D: Small wing with high wing loading = good penetration into head winds, improved roll and pitch control BUT increased stall speed. Yet again not that simplistic. A huge wing with good billow shift will handle better than a small tight sail, but will suffer in a headwind.

Confusing? Then enters aspect ratio, nose angle and anhedral and dihedral, all of which aims at addressing the above issues again.

So the bottom line is; There is a lot more hi-tech in our little pizza wings than meets the eye !

[KFA]

Thanks for the answer kloot, excactly what I meant. My English is crap so I keep to short posts. So to determine Va you multiply the stall speed with the square root of the design load factor(normally 3,8g's). Eg stall = 28mph then the sum will look like this
Va=28 X 1.949
Va=54,5mph
Hope it helps