Rotor flap on rough fields

Build a Light weight Helicopter! Take off and land it pretty well where you want, No bumpy ride.

Coming from someone who has both a Mosquito and a GyroBee, you might want to consider flattening out the bumps before going the heli route.
 
From my past experience. If you try to take off on a rough field. Your rotor blades will loose lift with every bounce. Make sure you have plenty of rotor RPM to ensure you do not get any flap. It will take twice the distance to takeoff because of bounce.
 
Do most people use a rotor rpm guage? I'm sure if its ready to fly it will fly. I'm guessing rotor rpm is sorta like airspeed in a fixed wing?
 
Have had the good fortune to be learning on a Bensen with 22' RotorHawkes and no prerotator.

I have learned now to be able to little excursions in order to keep the blades up to speed while waiting for take off behind others.

These little bursts of accelerating ground run do serve to keep the rotor from getting too low in RRPM.

I do not have a rotor RPM guage and though it took time have begun to recognize by sight when the rotors are getting a bit slow. When they do it is pointless to try to go as they will flap, and RotorHawkes are mild mannered blades.

This has all been a good build up to the 23' DW's we are going to put on the Hornet. I will have not one but two rotor tachs, and two engine RPM guages. This is simply because I bought a dual instrument on the forum which is proving a bit hard to read in sunlight, and the Tiny Tach and Schwinn are so cheap that as back-ups they were hard to pass up.

With those weighing ounces and self powered even an ultralight need not go without them.
 
I fly a gyrobee hybrid (no pre-rotator) out of a rough grass field quite a lot. As mentioned, the real key is keeping your rotor speed up. Once I hit about 120 RRPM, even a bumpy ride seems to have no more tendency to cause flap. Less than that and you are taking a chance on a flap. High-speed flaps are bad. Get your rotor speed up before you get serious about a take-off.

It doesn't hurt to get really good at short-field technique. Get your gear off the ground early (behind the power curve...oh no!) and then put the nose down a foot or so off the ground to get your speed up before climbing out. You won't get much (any) help from ground effect on grass.

I don't use a RRPM gauge on the little gyro, but it is nice to have, especially when getting used to the machine. It is a good double-check on grass to know when you are in the safe zone or when you need to work on getting a bit more RRPM. Look at the threads about using a bicycle speedometer (about a $10.00 investment) for RRPM.

*JC*
 
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I have a starbeegyro. The small oe wheels and std shocks are great on pavement but did not work for me on grass. I have changed over to Dominator type Wheel Barrow Wheels, 14" dia, and run them at 16psi. This combination has done wonders for my grass takeoffs. To shorten the takeoffs further, I now begin by roll with my electric pre rotor on and only turn off the assist when the blades accelerate above the max 150rpm pre rotor speed. Operation of the throttle and pre rotator toggle switch, with one hand, took a bit of practice!
 
David Bliss said:
I have changed over to Dominator type Wheel Barrow Wheels

Yes, I also have wheel barrow wheels running at low pressure on the GyRonimo (bee-like gyro). It has no pre-rotator, so I have to taxi carefully on a fairly smooth-ish part of the grass field until I get the rotors really going before I attempt to transition any rough ground. I have seen another gyro flap Dragon Wings after a pre-rotate to 100 RRPM on the bumpy part of the runway. The pilot was initally shocked that it could happen, but took the appropriate steps before anything got out of hand.

*JC*
 
Rotor rpm gauge? I find it more useful to look at the blades instead of a little box with numbers on it. The blades tell me more.

I think David has hit it on the head. The standard StarBee wheels and suspension is designed for smooth surfaces, for rough surfaces you need bigger wheels and suspension with good damping.

With the standard suspension it's a very unpleasant experience hitting bumps when the rotors are already generating lift but not enough to stay off the ground. That's the point where things can go wrong very quickly, and because the rotors are already close to flying speed they have the potential of really ruining your day.
 
Heres a view of the north and south sides of the field I fly from. My plane rides real smooth on the north end but theres a few shallow dips on the south side. Do you think a gyro could fly outta here? :confused:
 

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Oskar I'm not gonna use starbee suspension, gunna use the stock bungee cord suspension in ralphs plans! I dunno how it will work but you can adjust the suspension with differnt bungee cords.
 
Rotor rpm gauge? I find it more useful to look at the blades instead of a little box with numbers on it. The blades tell me more.

Hmm guess you have to have the experience of knowing what thos blades are saying. If one is a newbie then being able to look at the blades then see what that picture is in terms of numbers is going to build that knowledge base more accurately and quicker.Then do away with the tach and just watch the blades and know exactly what they are saying.

As for the field, it looks OK, but what gyro? What performance will it have? What is the temperature when you are taking off what is the altitude?
 
Saw an experienced gyro pilot try taking off on a bumpy sod field once, had his blades up past flap speed with a good pre-rotor, after about 400 feet was unable to get lift because apparently every time the blades "flexed", (not flapped), lift was momentarily broken and had to be re-established and this was so frequent that it just continuosly eat up runway. Although the blades were above flap speed, additional blade speed could not be obtained due to the repeated "lift disruption". This was at Oshkosh some years ago in the ultralight area on the old crappy rough sod field.

Tony
 
Saw an experienced gyro pilot try taking off on a bumpy sod field once, had his blades up past flap speed with a good pre-rotor, after about 400 feet was unable to get lift because apparently every time the blades "flexed", (not flapped), lift was momentarily broken and had to be re-established and this was so frequent that it just continuosly eat up runway. Although the blades were above flap speed, additional blade speed could not be obtained due to the repeated "lift disruption". This was at Oshkosh some years ago in the ultralight area on the old crappy rough sod field.

Tony
Well that's good to learn. Thanks I didn't know that could happen too!
 
Those photos might be deceptive, but that looks like a very smooth runway on the one side and not bad on the other. You'll easily be able to spin up the blades going one way and then turn around quickly for the takeoff, I cannot see a problem taking off there.

I've had similar experiences to the pilot at Oshkosh, once the gyro starts bouncing it struggles to get off the ground. It really is a very unpleasant experience.

Regarding the suspension there are normally 2 main parts, the first is the spring component and the second is the damping component. The spring component will always be there, it's the bungy in the original gyrobee suspension. The damper is the thing that dissipates energy when the suspension moves. It needs to be some form of a friction device in the suspension system, and without it you end up with a bouncing aircraft. If there are plates in the gyrobee suspension that rub against each other as the suspension moves it would count as a form of crude damper. Shock absorbers usually use oil which gets squeezed through small holes.

With no prerotator a rotor rpm gauge really just gets in the way. There are lots of things happening while spinning up the rotors, if you start concentrating on a little box with numbers things are bound to go pear shaped. It's much more useful to concentrate on airspeed by feeling the airflow (the airspeed indicator is useless at these speeds as well) and watching the blades to see if they are accelerating or not. Handstarting using instruments just don't work.
 
Energy is required to change the plane of rotation of the rotor disc. The source of that energy when hitting a bump that changes the rotor plane is the energy stored as kinetic energy; rotor RPM.

With every bump, some of the rotor’s stored energy is sucked out, slowing it down.

Loosen your grip on the stick and allow the rotor to float a bit instead of keeping it tightly coupled to the airframe.
 
Energy is required to change the plane of rotation of the rotor disc. The source of that energy when hitting a bump that changes the rotor plane is the energy stored as kinetic energy; rotor RPM.

With every bump, some of the rotor’s stored energy is sucked out, slowing it down.

Loosen your grip on the stick and allow the rotor to float a bit instead of keeping it tightly coupled to the airframe.
That's what I wanted to know too, Thank you Chuck!
 
I was flying my KB-2 off a grass strip all the time. At first I tried balancing on the mains like normal but found that hard to do as I bumped along. I then starting using the rough/soft field take off all the time. I prerotated to 200 RRPM's then held the cyclic full back as I started my takeoff roll. The front wheel would come off the ground very quickly but I kept the cyclic back. It didn't take long for the rotors to pick up enough speed to drag me into the air. At this point I was not a full flying speed yet so I would level off and pick up speed before I started my climb out. Using this method I could get off the ground and off the bumps very quickly.
 
Thank you Tim, that is very similar to flying a FW!
 
Tim and others. Isnt this a standard take off? I take off this way all the time. But I pose a theoretical question I have thought about a lot. If getting the rotors up to flying speed as quickly as possible is the goal.... isnt it better to make that initial roll out with the disk as flat and as efficient as possible, then briskly pull the stick back just enough to pop the gyro into the air, then immediately lower the nose and stay off the deck while gaining additional AS? I had occasion to try this only once in a very critical situation (my best friend had just crashed his Quicksilver on a beach and after landing to check on him I had to now get out of there)... and it worked very well. How would this not be a "better" way?

I also like the idea of holding the stick a tad looser to allow less absorption of the lift energy. I have noticed that it make a big difference in how much I might have to fight with the stick if my blades are still turning and I am rolling over rough ground. I will now incorporate this into any grass take offs.
 
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