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HomeAircraftHelicopterThunder TigerOther › Preparing for Death Spiral
02-07-2006 08:28 PM  12 years agoPost 1
Rafael23cc

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Junction City, KS

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A couple of weekends ago I was preparing for a death spiral by just rolling the heli on it's side and letting it fall for 100 or so feet. (it goes by pretty quick) Well the first few went ok with a roll left to a knife edge and roll right to right-side-up hovering.

The problem was the following weekend when I went to try it again, the heli did a half pirouette and ended up nose in while falling. I recognized the attitude and recovered with no problem. Tried it again and the same thing happened, roll left, the tail swings down and around until it is falling on its right side. Recovered again but by now i had to practice some other maneuvers to calm myself.

The only difference that I noted was probably temperature and wind. The first weekend, the temp was in the mid 50s and light wind. the second weekend the temp was in the low 50s / high 40s with about 10mph wind.

I was doing a search here and found the possible solution, that is to roll right to initiate the fall. That way the tail rotor does not have to keep up with the fall.

What do you guys think?

My set-up is:
R50, Hyper, Hitec 945MG on collective and Cyclic JR 500T and Hitec 6965 on tail. Maverics 80mm tail blades.

I will try rollling right when the weather gets nice again, but in the meantime, I'll appreciate your opinions.

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-07-2006 10:45 PM  12 years agoPost 2
TTRappy50Uk

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North Yorks (UK)

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I have just started to do death spirals for real i can do them on the sim with my eyes shut - i have done about 8 now and i roll right - as soon as knife edge push the nose around do a full turn and stick in 90 deg of rudder and fly out inverted towards myself, never tried to roll left though maybe its as you say and the tail rotors and affecting things??

www.hambleton-helis.co.uk

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02-07-2006 10:59 PM  12 years agoPost 3
Rafael23cc

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Junction City, KS

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I read on the 3D forum of another guy with similar symptoms but on a Scaedu. I'm not familiar with that heli so I decided to post this on the Raptor Forum.

My guess is that the tail rotor cannot keep up with the falling speed, but it threw me off when it rotated _against_ the fall going tail first for a while and ending up falling on its ride side nose in. (I started the fall tail in). I would have expected for the tail to rotate _with_ the fall and the heli would just fall nose in towards the ground, and an elevator bail-out to be performed to prevent a meeting with terra firma.

I need to upgrade my computer so I can run the simulator. I wish I kept my Army laptop!

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-07-2006 11:03 PM  12 years agoPost 4
TAZZY

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Westfield,MA

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i always roll to the left for death spirals and have never had a problem, i run a 401 with 9254 on tail. maybe your gain is too low.

GDay

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02-07-2006 11:20 PM  12 years agoPost 5
Tday

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Needham, MA

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I hate to say this, but this all sounds a little wacky. A heading hold gyro does exactly that unless you put in rudder or full tail pitch can't hold the tail or there's too little gain. Left/right---it doesn't make any sense for that to be a consideration. Absent something else, the tail will be held steady by the gyro. And if your fall is overwhelming the tail's ability to hold, then I can't imagine how it would rotate into the fall. I'd look to your inputs first on this one.

Tom

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02-08-2006 12:03 AM  12 years agoPost 6
Ruff

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Queen Creek, AZ

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You aren't using the stock solid tailfin are you? That will cause issues.

Ruff

http://srcha.com

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02-08-2006 12:43 AM  12 years agoPost 7
Tom DeWinter

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Quad Cities, IL

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Are you running a governor? The knife edge fall requires neutral collective. If you are running the inverted bell throttle curve you may not have enough power to sustain the main & tail rotor speed. But, I wouldn't think it would be a problem in the beginning of the fall and before adding elevator.

Tom

Quad Cities RC Whirlybirds -- FunFly July 12 & 13, 2008 Davenport IA
Plan Now to Attend!!!

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02-08-2006 03:47 PM  12 years agoPost 8
Rafael23cc

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Junction City, KS

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TAZZY:

It is possible, I did not go thru the process of fine-tuning the gyro gain. You know increasing the gain until the tail wags and then backing down until it stops...


Tday:

And that is the exact reason I'm asking the question here. The day that I attempted the maneuver, there was only one peron at the field and he is a plank pilot, no clue about helicopters. I'll try to explain the maneuver to one of the plank flying guys at my club and have him look at my hands while I preform the maneuver to see what I do during the maneuver.


Ruff:

NO, I have the carbon Skeleton fin. But if I had a solid fin, the tail would not rotate _into_ the fall but feather away from the fall and point the nose of the heli down...

Tom DeWinter:

No, i'm not running a governor, all the specs of my heli are on the top of the thread, nothing fancy. All of this happens as I'm practicing the entry and recovery of the maneuver. I have not attempted any elevator input yet. I do have cyclic and tail to throttle mixing for that reason, when I'm at 0 pitch and input cyclic or tail commands.

Thanks for your comments, keep them coming if you have more ideas. I'll try some of them this weekend if the weather cooperates.

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-08-2006 07:48 PM  12 years agoPost 9
robhurlin

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Pretoria, South Africa

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I would tend to go with the gyro system comments above. I am also concerned with the hitec 6965 servo on tail rotor. It is reasonably fast but not in the league of dedicated tail rotor servos. Try the JR 8700G servo which is recommended for the 500T.

Rob.

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02-08-2006 07:50 PM  12 years agoPost 10
TAZZY

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Westfield,MA

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i'm king at death spiraling, i get it up sooo high you can barely see it, and i can easily get 20 rotations out of the free fall. it's alot of fun, you can really get the crowd going with that one, especially if you exit it from 5 eet off the ground (i'm working on that one)

GDay

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02-08-2006 10:24 PM  12 years agoPost 11
Rafael23cc

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Junction City, KS

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robhurlin:

Please tell me why should I run a $120 servo when I found these Hitecs for less than $75 Specs are below.

HITEC HS-6965 0.10 sec 92 oz/in
JR NES-8700G 0.09 sec 49 oz/in

That is a difference of _ONLY_ 0.01 seconds, and I have almost twice the torque.

Yes, the guy at Horizon Hobby also recommended that I run an 8700 when I went from my 30 size and 810G to my R50 and R70. He said that the 810G did not have enough torque to properly control the bigger tail in the R50 and R70. I understand, but it is a $120 servo!!!

So asked myself why spend $120, when I can get almost the same thing for about $70.

I'll try re-setting the gyro, and try again.

TAZZY:

Let me work on the maneuver first and then we can talk about bailout at 5ft. That is nuts!

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-09-2006 03:16 AM  12 years agoPost 12
inkspot1967

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Cranston Ri

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i'll tell why you should use the $120 servo....in one word....

framerate....

the $120 servo has a higher framrate which makes the servo way better...it has a quicker responce time ,torque isn't a big factor there ...speed and no latency is the biggest factor to consider on a tail ...thats why your having your tail blowout on you

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02-09-2006 04:04 AM  12 years agoPost 13
Rogue123

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Phoenix AZ

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I use the 9254 for the tail. Im running the 500t without any probs also I have 92mm on the tail. I roll to the right then push and roll out left. using the TjP with a head speed of 1930~1950.

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02-09-2006 06:41 AM  12 years agoPost 14
robhurlin

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Pretoria, South Africa

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Rafael, inkspot put it very well. It's all about frame rate, ie the rate at which the gyro updates and the rate at which the servo receives the updates. Thats why the manufacturer generally specifies a gyro and servo as a matching pair. The frame rate is about double as far as I know on Futaba gyros. The 9254 has a speed of 0.06s, much better than the JR. I have a JR 9XII and 3810 and stick with JR whenever possible. When it comes to gyros I find the 401/9254 gives the best value for money in terms of performance. I was disappointed with my old JR 550T so I changed to Futaba.

I suggest you beg, borrow or steal an 8700G or 9254 and try it. If it works then invest with confidence. There are times in heli flying when an extra $50 is an investment in preventing frustration, hassles and time wasted. The gyro servo is one of those critical items! Painful but true.

Rob.

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02-09-2006 07:10 AM  12 years agoPost 15
Rogue123

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Phoenix AZ

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robhurlin said it best, welcome to the world of this HOBBY.

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02-09-2006 06:03 PM  12 years agoPost 16
Rafael23cc

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Junction City, KS

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Ok, Ok, I'll try the following:

1. Rolling to the right instead of the left to start the fall.
2. Increading the gyro gain to the limit (and roll to the left then )
3. I'll beg, borrow and steal for when is time to upgrade I can upgrade to a 8700 on the tail, until then it has to wait. I was hoping for upgrades with more bling than a servo, but that will have to do....

Weather seems crappy for this weekend, so the maneuver may have to wait for another week.

Thanks for all your opinions and suggestions.

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-09-2006 07:13 PM  12 years agoPost 17
kaptkaos

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Miami FL

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Are you absolutely positive that your at close to 0 pitch and not bleeding into the cyclic or tail axis? Its easy to do when you are nervous...ask me how I know!

In this hobby, you cant cut corners on servos, you get what you pay for. I notice the difference immediately when flying other peoples helis. Use Futaba all around, 9252, and 9254 on tail.....

Also, get a governor, you will never go back, trust me.....

If you give a Chimp a gun, and the Chimp shoots, DONT BLAME THE CHIMP!!!!

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02-09-2006 11:13 PM  12 years agoPost 18
Rafael23cc

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Junction City, KS

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oh, yes I forgot that i had one more thing to try:

4. Have somebody looking at my hands when I try the maneuver the next time.

Thanks for reminding me kaptkaos...

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-27-2006 08:25 PM  12 years agoPost 19
Rafael23cc

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Junction City, KS

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Ok I had one more attempt at this, but the weather was borderline on crappy, so I could only put a few flights and only a couple of attempts at this maneuver.


On both attempts I rolled right, then let it fall for a while before attempting to recover. This time, on both occasions the tail swung with the fall making the nose point down.

I did not have the chance to try any of your suggestions, but I will try again next weekend.

Thanks to all.

Rafael

Keep your feet on the ground, but your eyes on the sky.
Team Heliproz.com

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02-27-2006 09:01 PM  12 years agoPost 20
TAZZY

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Westfield,MA

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what kind of tail blades are you running?
if they are the stock plastic ones, that could be your problem. you need carbons.

GDay

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