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crash - explanation

Old 10-17-2007, 02:22 PM
  #26  
scratchonly
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Default RE: crash - explanation

It is against our natural instincts to push DOWN elevator; We must be mentally prepared to do so when we are in trouble.
Old 10-17-2007, 03:46 PM
  #27  
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Default RE: crash - explanation


ORIGINAL: davideboracay

I used half throttle because this was the first time I flew a 4 stroke and i thought it would have much more power than my previous engine.
Also in reviews it says " it took off in only 50 feet at half throttle".

There is a fair chance that the description you quote isn't all of the story. He could have been advancing the throttle. But wouldn't have to. If you allow any airplane to build speed at any throttle setting, it can and will take off when the airspeed reaches flying speed.

There are lots of possible things that the reviewer meant. And the real kicker........ We have no idea if his takeoff was into a wind of any value. Lot's of things unknown.

What is good about this is that whatever happened, you experienced it and have the experience filed away. You know to do differently for sure. and probably repeat whatever it was that took out the model. Even if none of the explanations seem to fit, you know what not to do again.
Old 10-17-2007, 04:19 PM
  #28  
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Default RE: crash - explanation

bla bla, You speak so authoritatively, you must have some type of credentials to back up your opinions! Please inform us of your experiences in the aviation field?

Or, are you simply waiting under the bridge for Billy Goat Gruff?
Old 10-17-2007, 05:59 PM
  #29  
da Rock
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Default RE: crash - explanation

The really good thing about this thread is that all the input for solutions combines into and excellent recipe for safe take offs:

1. Steady, controlled throttle advance to full throttle.
2. Light movements only for the elevator and aileron.
3. Correct heading with rudder only.
4. Stay on the ground until it's definitely flying.

And that'll avoid any whatever-it-is from happening.
Old 10-18-2007, 09:36 AM
  #30  
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Default RE: crash - explanation


ORIGINAL: Mode One

bla bla, You speak so authoritatively, you must have some type of credentials to back up your opinions! Please inform us of your experiences in the aviation field?

Or, are you simply waiting under the bridge for Billy Goat Gruff?
I've been flying RC planes since the beginning of the 70's so I've had some experience. Even though Im no rocket scientist but that torque roll thing... It just doesn't happen like that man.
Its the action - reaction thing. Sure engine torque is being transmitted to the airframe... the same amount thats being transmitted to the propeller, but the airframe/wing is infinitely bigger than the propeller thus countering the twisting effect. Now if you have a HUGE propeller and a tiny little wing... the planes going to rotate. But that not the way are planes are set up.
Sure we can have far more power... say twice as much as normal so the torque is now, in theory, x2 even then it has no noticable effect. It isn't going to roll your plane on take off.
With the big IMAC/3D planes with 2- 2.5 or even 3 times the power to weight ratio, a vertical torque roll takes time and in many cases, aileron imput to initiate. The plane is flying perfectly straight and level the rest of the time with no need to counter the engine torque.

What is evident with many planes during take off is a distinct swinging to the left during the take off runn and the climb out. Many people believe this is due to torque but it is due to the P (propeller) effect . The spirelling propeller slip stream striking the fin. With some tail draggers, this effect can be almost uncontrollable until the tail comes up, the fin and rudder escaple from the "blind spot" caused by the wing and the rudder now enters the slip stream and is able to counter the swing.
People believe this effect disaperes after take off but in effect it's present constantly through out the flight. Pull up to establish a vertical line and most untrimmed planes will again tend to viere off to the left.
This tendency can be allmost eradicated by adding right thrust and/or using a throttle to rudder mix. Again, this didn't just happen because you pulled to vertical, it's present most of the time. It only tend to become noticable during vertical flight.

Old 10-18-2007, 11:08 AM
  #31  
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Default RE: crash - explanation

Hi!
Have you flown before???
Old 10-18-2007, 11:24 AM
  #32  
davideboracay
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Default RE: crash - explanation

GUESS WHAT! I HAVE FOR 3 YEARS. THIS IS THE FIRST PLANE WITH A 4 STROKE ENGINE I'V TRIED!!!
Old 10-18-2007, 12:10 PM
  #33  
da Rock
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Default RE: crash - explanation

There you have it !!!!!!!

Another casualty to the dreaded 4strokes. Minnesnowta needs to add this characteristic to his 2C/4C comparison chart.

It just doesn't happen like that man.
Its the action - reaction thing. Sure engine torque is being transmitted to the airframe... the same amount thats being transmitted to the propeller, but the airframe/wing is infinitely bigger than the propeller thus countering the twisting effect. Now if you have a HUGE propeller and a tiny little wing... the planes going to rotate. But that not the way are planes are set up.
Actually it does. Remember the function rpm's play in the engine power equations? A tiny piston that weighs almost nothing can't create enough force in one stroke to do much to a big old airplane. But add a lot of strokes per minute and........... And same thing with a tiny prop being able to torque roll a big old wing. Especially when it takes almost no force to move that big old wing when it's just hanging there doing nothing much. Try this....... hold your airplane up by the prop. Push on one wingtip and see how much effort it takes to move it. How fast does it roll when you got that 3D sucker torque rolling? RPMs is the answer. Lots from the prop, only a few from the wing.
Old 10-18-2007, 12:17 PM
  #34  
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Default RE: crash - explanation

I gave slow progressive throttle to half and didn't touch the controls after that.
Didn't touch any of the controls? "Bing!" We have an answer. Not holding down elevator to be able to steer? Not holding right rudder to prevent prop torque from drifting it left? Not ready to counteract rudder vs. tailwheel steering imbalance when the tailwheel looses steering authority and release right rudder stick immediately to prevent a . . . snap?

Next time be on the controls and control the airplane.

Roll the airplane on a smooth flat surface with the rudder centered. If it veers to either side adjust the tailwheel. If the rolling motion is direction is different from the flight direction it will always veer when lifting off. Tail draggers take a little finesse for a slow takeoff. Getting into the bad habit of turning the engine on full and yanking the stick will bite you eventually.
Old 10-18-2007, 07:29 PM
  #35  
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Default RE: crash - explanation

Bla Bla, We have similar R/C experience. However, I did take a hiatus for 10 years. I've been building and flying model airplanes since the early 1960s. I did have my pilots license for a few years until I started thinking about all the R/C stuff I could have bought for the cost of aircraft rental. However, going after your private pilots license was an education on aviation that most R/Cers just don't get.

I am skeptical of your explaination on P-factor. Spiraling wind around the fuse hitting the fin and rudder and pushing them to the right, seems unlikely. My understanding of P-Factor for take off roll is because the airplane sits nose high at this time, the downward swinging prop blade is at a higher angle of attack creating more thrust, then the upward swinging blade. Certainly other factors are involved and it is likely complicated by these other factors! I certainly don't have all the answers or knowledge on these topics and don't claim to be an expert. I do however know enough about all this to know there are few clear cut, hard & fast rules and if you claim your absolutly certain about something in aerodynamics, ten other people will be absolutly certain you are wrong!
Old 10-18-2007, 07:41 PM
  #36  
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Default RE: crash - explanation

Sounds like most crashes. You ran out of airspeed, altitude, and ideas at the same time.

Bill, AMA 4720
Old 10-19-2007, 05:04 AM
  #37  
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Default RE: crash - explanation

ORIGINAL: Mode One

if you claim your absolutly certain about something in aerodynamics, ten other people will be absolutly certain you are wrong!

Absolutely... look at this thread!

But I'll still stand here today, naked [X(] to the world and state that unless you are flying some type of experimental airframe... you're not going to suffer from a torque roll on takeoff unless you plan it!
Whats happening is the P effect. Spirelling air hitting the fin and yawing the airframe to the left. And it will continue to do so throughout the flight at varying degrees associated with the throttle use. Fly at full throttle: much effect, medium throttle: some effect and at low throttle: no, or because you're trimmed it out, very possibly the opposite will happen and you'll now start drifting to the right!

Now,this effect on the fin is having a similar effect as rudder input and inturn will effect your plane differently depending on the aircraft design.
Unless you are flying a well trimmed and neutral F3A or competitive aerobatic design where rudder input only creates a flat yaw, this is going to cause the plane to yaw... and roll!
And because this effect is very evident during take off, It's this fin/rudder induced slow roll/bank thats people can sometimes believe is due to torque.
Whats important to remember this happens quite slowly and is, under normal circumstances,always corrected by the pilot. What happens sometimes during take off is a SNAP due to too much elevator and low speed. Because this happens fast and because the plane is in a stalled condition, no corrections are going to be effective anyway... bang you hit the ground and stand there in stock asking "what the F' happened?" Desparate for answers, people will cling to anything that sounds resonable. And excludes pilot error! That's where the... ohh a torque roll... how unlucky you are nonesense comes from.

Solution is simple... learn to trim out your plane properly. And the best way to learn this is get yourself involved with competive aerobatics.
Even at a beginners sports level, you'll learn an enourmous amount, the benefits of which will make your general sports or scale planes fly so much better and the practice will only increase your own flying skills.
I'll put my clothes on again now.
Old 10-19-2007, 06:54 AM
  #38  
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Default RE: crash - explanation


ORIGINAL: Mode One

bla bla, You speak so authoritatively, you must have some type of credentials to back up your opinions! Please inform us of your experiences in the aviation field?

Or, are you simply waiting under the bridge for Billy Goat Gruff?
Well since somebody mentioned my name guess I'll put my .02 cents in.
My vote goes to.... Forgot to hook up ailerons.
Old 10-19-2007, 07:26 AM
  #39  
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Default RE: crash - explanation


ORIGINAL: BillyGoat


ORIGINAL: Mode One

bla bla, You speak so authoritatively, you must have some type of credentials to back up your opinions! Please inform us of your experiences in the aviation field?

Or, are you simply waiting under the bridge for Billy Goat Gruff?
Well since somebody mentioned my name guess I'll put my .02 cents in.
My vote goes to.... Forgot to hook up ailerons.
Hey i've done that.
And taken off the them conected the wrong way.
And landed it!
Not a mark on the plane.
My underpants were a different story.
Old 10-19-2007, 07:51 AM
  #40  
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Default RE: crash - explanation

Took off once with the rudder trim slider all the way to the left. (It was in the winter and I was using a plastic baggie slipped over the transmitter to keep the wet falling snow off). "Where the heck is that crosswind coming from?!?!" Got airborn, realized the problem and made the second mistake of trying to tug the cover for slack so I could reach the trim slider. Managed to squeeze my left thumb off the aileron stick with the cover while pulling back with my left hand to reach the trim with my left thumb. By then the model was a smoking hole in the mud.

Moral: a take off that starts bad should be aborted. It will only get worse. And don't use a baggie as a transmitter cover. ;-)

God Bless the man who invented digital trims.
Old 10-19-2007, 09:37 AM
  #41  
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Default RE: crash - explanation

Hi!
Agree with Bla bal...I have never in my 32 years R/C flying seen any airplane torque roll at take of ...but seen many newcomers snap roll their airplanes.
Old 10-19-2007, 04:47 PM
  #42  
da Rock
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Default RE: crash - explanation

So, if any of you beginners learn one thing from this thread, it's that on takeoffs, pushing the throttle too fast and pulling the elevator too much will result in........ a crash.

Why? It could be a number of things, and the jury's out on which one of the many.
Old 10-19-2007, 08:27 PM
  #43  
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Default RE: crash - explanation

Agreed.
But it aint goin' to be da torque roll!
Old 10-19-2007, 09:00 PM
  #44  
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Default RE: crash - explanation

Would you just give it a break already.....what does it really matter......Unless one of you is an Aviation Engineer I am tired of your so called "opinions". Call it what you like but the fact is the plane was going too slow to fly and the pilot didn't compensate.
Old 10-19-2007, 09:03 PM
  #45  
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Default RE: crash - explanation

I`ll second that.
Old 10-20-2007, 07:44 AM
  #46  
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Default RE: crash - explanation

I guess we're starting to make people mad at us for finding this superfluous disagreement interesting. Per Waross and Insanemoondoggie we must stop now.
Old 10-20-2007, 08:12 AM
  #47  
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Default RE: crash - explanation

oops [sm=spinnyeyes.gif]

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