randy41

My first attempt of a loop ended in a crash.
Back to the repairs. LOL.
It is my first crash but not the last iam sure.LOL

Vortexgen

glad to see you`re not taking it too serious..

QUOTE-It is my first crash but not the last iam sure.LOL -QUOTE

it looks like you didn`t hit nose first (normally a sign of looping too low), what happened???

with a heading hold gyro, it takes practice to get the tail directly behind the heli. i know that if the tail is slightly off, the loop can easily turn into a corkscrew, and loss of orientation can happen if your not ready. did this happen?? just a hint for your next loop...

downtime sux......

randy41

Vortexgen: I think there was several things i did wrong. LOL

1= It was to far away(I didn't want to get hurt).
2 = I had the gv-1 on 1750 rpm.(to fast)
3 = when i started over the top i pulled negative collective
and the helli went into inverted position(Pretty) but
it scared me and i didn't know how to get it uninverted.
4= I tried to loop out of the invert(wrong) I should have
used my aileron not my elevator. She was to close to the
ground at which point i tried to roll out and thats why she hit
on her side(You were right it didn't hit nose in). LOL
I will continue to try. I have enough new parts to build
5 complete hellis and just ordered some back to keep up
the stock. LOL

Could you kinda give me alittle insight on how to do a loop
as far as the stick movements. My trainer will be sick. He is
out of town on vacation for a month(must be nice. lol).
he told me not to try anything fancy(I should have listen.LOL)

Ps: No down time she is already put back together.

RickC2009

My Feedback: (12)

Do you have to have negative pitch to do a loop?
Can a loop be done without it? (-2 to +10)
If so can some one give me the inputs?
Do you go to idle on the top?

thanks
Rickc

Vortexgen

okay guys,
to get you through those first few loops
1. first get comfortable with the heli being at a distance and doing circuits at altitude. Particularly practice diving slightly to gain as much speed as possible as it flies straight. Not necesarily a steep dive, just about 25-35 degrees down so you gain heaps of speed.
2. The lowest part of the dive should still be about 15-20 meters from the ground.
3. do your absolute best to get the tail directly behind the fuselage. (easy with NORM gyro, needs your input with HH Gyros)
4. When comfortable doing these high speed passes then simply pull aft cyclic and hold until the chopper has completely looped then use forward cyclic to continue forward flight.
5. If you do not move the collective from where it was when you entered the loop, usually about 75%, then the heli will still loop without a problem. Simply tighten the loop by pulling more aft cyclic if you start losing altitude too much.
6. This will get your confidence up in the heli being able to loop which will inevitably lead you to the next step..........
REMEMBER - ENTRY SPEED & ALTITUDE!!!!

7. Reducing the pitch while looping should occur so that the transition from positive to negative pitch (o degrees pitch)happens when the heli is vertical, and the most negative you decide to pull should be at the crest. Start with small inputs until you get more comfortable.
8. In an effort to begin inverted straight and level, and extend the inverted section of the loop, make sure you keep the airspeed on and always have a BAIL OUT PLAN- roll,flip, or half loop.
9. Gradually decrease the airspeed to hover inverted, remembering your bail out plan.

More info.
- A half hearted loop is a disaster in waiting - go for it 100% only. Sometimes its best to fly the high speed passes until you feel very comfortable with the speed and then go for the loop on the pass that "just feel right".
- If extending the inverted section to hold altitude or even hover, you will need negative pitch to be setup.
- Semi symmetrical blades need more negative pitch.
- Without a governor, or if the governor is switched by the transmitter stick position, requires another pitch curve which increase the throttle at below 50% stick position. (keeps revs up - not required just for a simple loop though)
- Look at getting a header tank for extended inverted flight.

good luck,
sorry go to go........
-

RickC2009

My Feedback: (12)

vortex
thanks very helpful info!
I have just started doing stall turns and feel very confident with them but I have noticed on the down line when it picks up speed the heli seems to always pitch up!( maybe I am just over correcting but it seems like there is not enough elevator to pull out of the dive and then there is way to much!)
Even more so when I am flying up wind. When I fly level and fast it also seems to do this but only when I pick up alot of speed. Any thoughts on why this is happening?

rickC

randy41

Vortexgen: Thanks very much. As always you are
very helpful and i appreciate it. My helli is doing fine
and back to normal for right now.LOL

Vortexgen

rickc2009,

you are experiencing a very normal condition in helicopters called blade flapback.

I assume you understand the very basics of helicopters, that the spinning blades form a rotory wing (or disc). Any rotating mass has gyroscopic forces, from a spinning top, to a bycicle tyre, to the rotory wing (helicopter).

If you appy a force to a spinning mass (gyro) the reaction occurs at 90 degrees to the applied force.

I'll use pitching up = aft cyclic = aft elevator in the example

Heres what happens -

- We want the helicopter to pitch nose up.
- we apply aft cyclic elevator.
- the servos drive the swashplate and tilt the swashplate aft.
- the blades actually lag the swashplate by 90 degrees because the pitch links are at 90 degrees to the blades.
- the blades subsequently reach the highest amount of pitch 90 behind the swashplates maximum tilt, at the 3 O'clock position (12 oclock is nose/6 oclock is tail)

- at this stage you might want to see this for yourself, by spinning the disc by hand, keep the flybar level, and watch the blade pitch change through one revolution while applying aft cyclic.

-so, as the blades reach maximum pitch at 3 oclock, we are effectively trying to tilt the whole disc to the left side.
- as the disc is a spinning mass, or gyro itself, tilting the disc left results in pitch up changes. (90 degrees from the left tilt=pitch up)

-if you tilt the disc right, the nose pitches down.

Thats all normal aerodynamic physics.

Now the condition we all experience when gaining airspeed and resulting in an automatic pitch up condition is explained as follows.

Lets assume the blades are rotating at 100mph.
When hovering the lift generated by the disc is even at all clock angles.
When moving forward say at 50 mph, there is an advancing blade (on the left side of the caliber) and a retreating blade (on the right side of the caliber)

The advancing blade will be moving through the air at 150 mph.
The retreating blade will be moving through the air at 50 mph.

This of course will cause the advancing (left side of the caliber) blade to generate more lift than the retreating blade. This will try to tilt the disc left, the subsequent reaction is for the nose to pitch up (same as a commanded aft cyclic described above)

Before you ask, helicopters can suffer from whats known as retreating blade stall if they exceed the airspeed limitations. (not normally encountered in RC)

hope this helps, its easy to explain standing besides someone with a model handy - more difficult in writing.