Crash Campbell

Hi,

I'm posting this in the beginner's forum as most visit here from time to time, but it applies to us all.

Long storey short. I passed an elderly beginner (in his eighties) on to the most experienced instructor in our club as whilst I had assited him to learn to fly an Easy Glider, micro cub and a slow stick, (all without ailerons), I was unable to stop him "over controlling" his first aileron model, an electric foam piper cub, about a 40 size machine.

The instructor was adjusting the rates with the assistance of our clubs radio guru as the transmitter is a Hobby King brand with "Chinglish" instructions so those of us used to JR, HiTec, Futuba et al have a real learning curve to negotiate. The model was inverted on a work bench at the field with the battery cover removed but the battery was still connected to allow the throws to be measured. Unfortunately the throttle was inadvertently reversed. The motor went to full revs dragged itself off the bench and into radio gurus thumb splitting it end on, from tip to cuticle right through the nail and the bone. The injury required micro surgery to repair and will see the injured party unable to fly for some time.

The message is alway ensure that models are restrained when working on them and that electric motors can start unexpectedly and require particular care. Ok this may be overkill for ducted fans.

I hope "newbies" and "old hands" can exercise true genius and learn from this mistake. Sorry I borrowed this partial quote from someones signature line.

Cheers,

Colin

CGRetired

My Feedback: (1)

This wasn't checked before the plane was worked on? You mean to say that the instructor had the power applied without noticing that the throttle was at full position rather than idle?

Sounds like a slight lapse of good judgement to me.

I've done something similar, but my throttle position was at normal idle, not full open. When I went to full open to "arm" the ESC, it was actually already armed. So, when I went from full open to idle, the motor rotated and, before I could react, it sliced my index finger to the point where I needed 5 stiches. Not near as bad as what happened in your situation, but somewhat different in terms of what caused the problem.

What I've suggested in the past was that motor checks be done with the prop removed. It won't hurt electric motors to do so. And, if that HAD been done, it would have been obvious that the throttle setting on the transmitter were not set right.

CGr.

carrellh

One of the first guys to bring electric models to our field gave this advice. While many glow engines will stop if the prop strikes something solid, the electric motor tries to keep turning until the power is removed.

CGRetired

My Feedback: (1)

You are right. And the reason for that is the nature of electric motors vs glow fuel or gasoline powered engines. With glow, you need the compression stroke to continue operating. Stop that.. even with a finger, and the engine will stop. With electric, however, the motor is propelled by magnetic force, which does not stop as long as there is current flowing through the motor windings. So, they just keep turning. My right index finger has three scars. One on either side of the one with stitches showing that the prop hit my finger three times as it was rotating.

The problem is, many, if not most, beginners don't realize how potentially dangerous electric motors can be when there is a prop attached to the shaft. Glow or gas can be dangerous, however, usually, you have to start them up first. With electric, well, a mistake, such as the original poster.. and me for that matter, made, can be inadvertent, and costly.

CGr.

MetallicaJunkie

thats scarry....something similar happened to me minus the cuts. i always verify throttle with prop off

Campy

My Feedback: (1)

A couple of things about this:

1. ALWAYS remove the prop when doing ANY type of adjustments on an electric, especially if you need to have the battery connected to do the adjustments. The little bit of extra time it takes to R&R the prop is worth it since it may very well prevent an injury.

2. Everyone missed this part of the original statement:


Just my two cents worth.

ChuckW

This is a very good poitn to bring up. A lot of people think that electric is less dangerous than glow or gasoline power but it is actually just as dangerous or even more so in some cases. A lot of us get complacent and overlook basic safety stuff such as restraining the airplane or removing the prop. Everyone needs a reminder liek this from time to time.

CGRetired

My Feedback: (1)

Campy:

From my first reply:

Although I didn't make it clear, I was indicating checking the throttle before turning the thing on.

CGr

Crash Campbell

Hi CGR,

The model had just been flown. The system was live with the throttle at zero. When trying to reduce the aileron throw on the low rates switch the throttle was inadvertently reversed via the TX, so no throttle now became WFO and the injury occured. I'm sure that had the radio been one he was familiar with the injury would not have occured as he wouldn't have selected the wrong channel.

Restraints or remove the prop as suggested seem to be the safest way to go when working on electric models. The only "good" thing was the motor didn't keep turning as having done the damage it appears to have lost a phase and only vibrates without turning.

Cheers,

Colin

jetmech05

there are those of us that have been biten....those of you that will be biten...if you stay in the hobby long enough....PLEASE, PLEASE PROVE ME WRONG.

blueapplepaste

My Feedback: (5)

If I'm working on any of my electrics, I will unhook one of the wires between the ESC and motor - just too easy to accidentally bump the throttle and really hurt yourself or something worst. Just a good habit to get into IMO.

AltaTed

I developed and manufactured electric motors for over 40 years. Something most don't know or think about is the types of motors we use in electric powered planes. They are constant torque devices capable of putting out maximum torque even below 1 RPM. Thats opposite the power curve of an internal combustion engine where they must be running at full speed to produce torques the electric motors put out at any speed. The slicing power at any speed is awsome so beware and be sure you observe safety proceedures as provided before in this discussion. They are silent and may not even be noticed they are on, ready to run and it's instant power....


.

acdii

One thing I learned with the heli's is to use the throttle kill switch when making any adjustments, so that if i bump the throttle the motor wont engage. I think this can also be used on the plane setting, at least on the DX6i, my mSR is setup under plane, and it works.  (i'm also training myself to use that instead of just chopping power when the heli is about to hit something, if I chop throttle on a CP, it will go down, hard.)

TruBlu02

This is what has always made me nervous about electric planes. They have instant power with no warning. I never mess with my electric planes with the props on. The APC E-props are razor sharp (learned that the hard way) so they go back in the prop drawer when the e models need some work.

scooterinvegas

My Feedback: (1)

Something like that happened to me. I was setting up a new Extra. Had the plane done and ready to go. I powered it up to check the controls and noticed that I didn't have any throttle. I moved the throttle up half way, nothing. Moved it all the way up and heard the tones of motor arming!! Not expecting that, I quickly chopped the throttle. I didn't know the throttle was reversed. When I chopped the throttle, the plane took off out the door of my garage! Damn! Hit a trash can, but no damage done. I felt stupid.