Beware of Surprise engine start
 

How can this happen, you ask. Well, I don't really understand it myself, but I know it can happen. Sunday, after one flight on a new plane, I refueled her and was getting ready to take her up again. It had been about twenty minutes since landing.

I placed the igniter on the glow plug, took hold of my electric starter with my right hand, then reached to the front of the fus to hold the plane with my left hand. The motor started by itself, BEFORE I touched the starter to the spinner. It caught my thumb and cut me pretty bad. Fortunately, our club's president and most experienced pilot had the transmitter and shut it down, since it did not shut down by itself. This was NOT a compression spin on the prop, but an actual start of the motor.

This has happened once before, on another plane, but did not cause bodily damage. I guess there was enough fuel or fuel vapor in the carb, plus heat remaining in the motor, that the igniter was all that was needed to start it. The cut took 11 stitches, and ran the full length of my thumb, and OMG how that first shot into the cut hurt.

So, guys, take some advice....even when the motor is not running, reach AROUND the prop diameter to the fus when you start the plane. Or have someone else behind the motor hold the fus while you start the motor. This is supposed to be a fun sport, and being safe will keep it that way. WATCH THAT PROP ALL THE TIME!!

RE: Beware of Surprise engine start
 

I've had a particular engine start when the glow plug was applied. I now hold the prop firmly when I put the glowplug on. Maybe not the smartest thing to do, but better than being surprised.

RE: Beware of Surprise engine start
 

Yep...ALWAYS assume a glow engine can start....


I have seen someone just gently playing with a prop on an engine (just flipping it back and forth) WITHOUT A GLOW DRIVER on the engine....
and it popped.....

ALWAYS assume a glow engine can start

RE: Beware of Surprise engine start
 

Add to that - always expect an electronic ignitioned gasser to start when you flip on the ignition switch. The electronic module will send a spark signal every time you turn it on. The planets could be aligned and the piston positioned just right for it to come to life by just switching on the ignition battery.

Be careful ... always.

Bedford

RE: Beware of Surprise engine start
 

I usually hold the prop securely with my left hand as I connect the glow starter. I have
not had this happen to me, but I have heard of it happening.

FBD.

RE: Beware of Surprise engine start
 

I’ve see that happen one time in fifty-five years of flying.

RE: Beware of Surprise engine start
 

I saw a motor start with out the igniter attached. He spun it to prime the motor and it fired.

RE: Beware of Surprise engine start
 

Full scale aircraft have been known to start when a strong breeze push's the piston off of top dead center.

RE: Beware of Surprise engine start
 

Thats enough for me to be careful... I like my fingers

RE: Beware of Surprise engine start
 

It did happen to me. Was flipping the prop back and forth showing someone how to back flip start a os91fs.
It did not start but made 1 pop. Could it have started? I dunno. I just told the guy SEE os91's just want to run!!
Im allot more careful about just flipping props now though!
Pat

RE: Beware of Surprise engine start
 

I had an engine pop and catch my knuckles...without any glow battery attached [X(] The catalyitic (sp?) reaction of the alcohol with the Platnum element of the glow plug I'm guessing?

Whenever I attach the glow plug battery I make sure the piston is at BDC or at least not closing/ trapping any vapors in the cylinder...along with keeping the hands well away from the prop.

My guess Capt. is that the piston was part way up (or down) in the cylinder, and just the right mixture of fuel/air was trapped in there and it ignited when you attached the plug battery.

RE: Beware of Surprise engine start
 

I hang my planes nose down on the wall.I try to keep
the port open to vent off the vapor. Once I reached from
my chair and turned the prop on a MVVS diesel and it
started. It had been hanging there for at least a month.
Wasn't hurt but it did my laundry no good.
Ralph

RE: Beware of Surprise engine start
 

....oh boy....:eek:

....when a pilot shuts off the engine in a full scale piston aircraft he does so by leaning out
the engine until it dies. Once this is accomplished there is no fuel left in the cylinders
or the intake manifolds. After the pilot stops the engine, he shuts off both magnetos. Full
scale engines have dual magnetos for redundancy (safety).

There is no way....not even in a hurricane, the wind can turn an engine over....through compression
and start it....even if the engines was primed for a restart, and the magneto switch was turned on....

...you're dreaming, or making up story's. :eek:

FBD.

RE: Beware of Surprise engine start
 

Proptop....You've made an interesting point here, although I'm not sure I understand all of what you're saying. This could change my start up procedure.

I don't know what you mean by "piston is at BDC" (Before Dead Center?). Are you referring to the point when there is loose play in the propeller, as apposed to when it's tight (during the compression stroke)?
Please explain further.

If your saying that the engine won't self start if the propeller is "loose", but it could if it's in the middle of the compression stroke, "tight", then the ignitor shouldn't be attached unless the propeller is "loose". THEN attach the ignitor, take hold of the plane, and turn the propeller to the beginning of the compression stroke with the end of the starter, and hit the starter button to spin the prop and start the motor. The free hand could be used to hold the loose propeller as an additional precaution, as suggested by a couple of respondents here.

RE: Beware of Surprise engine start
 

I can guess the next post "My airplane jumps out of the car and starts itself and shoots touch-n-goes until I get my transmitter out to the pilot station" :)--I have a MVVS gasser with electronic ignition that will pop-I have found over the years that if I handle my engines/props along the same idea as a weapon that your risk of harm is greatly reduced. (i.e. reaching over the rotating prop to adjust the carb or disconnect the glow stick, standing in the front or side of engine when engine is being ran(always behind for me), We have all seen the guy that is going to help you start your plane and he holds the transmitter and stands straddling the fuse with his heels against the leading edge of the tail and you assume the position kneeling in front of the model with your starter, as soon as the engine fires he firewalls the engine and holds the plane with his heels while you are inches from a prop that is comparable to a table saw. I had to have my left index finger reattached by a hand surgeon and have limited use of the finger due to my negligence of not following a couple of simple rules-do not let it happen to you.

RE: Beware of Surprise engine start
 

I have a super tiger 2000 in a yellow Cap 10 B that did it twice
with throttle wide opên to prime and glow driver off
it started at full song. was sure glad to have aircraft restrained. could have been real bad
I do not flip a prop without the aircraft beeing held or secure. a KB 40 pilon racer engine once while flipping to prime
can be very scary
have been playing with glow engines since early 50`s

RE: Beware of Surprise engine start
 

BDC = Bottom Dead Center.

Assuming the engine is two-stroke, the only way this can happen is if the engine is left with the piston somewhere in the upper range of its stroke, closing off the exhaust port, capturing ignitable mixture in the cylinder. Whenever you shut down a two-stroke engine, make sure the crank is in that "loose," or "free," area of rotation at the bottom of the piston stroke, and not in the the compression area, and this will not happen. Of course, use care when turning a hot engine, too, or it might bite you then. I usually give the prop a whack when my engine stops, just to make sure it's in that non-compression part of its cycle.

Similar thing with four strokes, but harder to tell where in the stroke the engine is left, and more likely to have the SUS occur. (SUS = Sudden Unintended Starting)!

Phil

RE: Beware of Surprise engine start
 

Had this unexpected start couple weeks ago with an OS 61, No glow liter attached. Just reached over and flipped the prop and the dang thing came to life. Glad there were several guys standing around watching cause I didn't even believe it and I was the closest one to it. Be Carefull because if IT CAN IT WILL!!!!!!!!:eek:

RE: Beware of Surprise engine start
 

Jeesh, my engines are reluctant to start when primed, glow plug powered, and using an electric starter. [:o]

RE: Beware of Surprise engine start
 

Have had it happen several times to me, on several Fox 35's no less including once without the igniter. If a Fox 35 can do it, the rest of you is in dangerous position.

RE: Beware of Surprise engine start
 

Flyboy Dave you stated that "....when a pilot shuts off the engine in a full scale piston aircraft he does so by leaning out
the engine until it dies. Once this is accomplished there is no fuel left in the cylinders
or the intake manifolds. After the pilot stops the engine, he shuts off both magnetos. Full
scale engines have dual magnetos for redundancy (safety). "



Yes, the engine is leaned out and the mags turned to off. However, after working at a local airport throughout college, I developed a healthy respect for 100% scale engines. A piston engine can start with the mags "off". If a magneto has an internal short, the impulse coupler can produce a current to the spark plugs. The reason for two mags is to produce redundancy for the spark plugs. If one is not working, the other is there to pick up the load. It is not for safety on the ground. I have personally seen a plane start when someone leaned a little too hard on a prop. The stars where aligned, gravity was in place, and everything was perfect. Luckly for that person, they got out of the prop arc before they got hurt. The can happen especially on older engines that have lower compression in the cylinders. A good pilot or lineboy "proping" a plane is already ready for it to start no matter how long it has sat on the ground. After propping planes hundreds of times, my insurance policy was someone was always in the seat with the brakes applied. "Brakes On, Mags cold" was always the way to do it, but even with "cold" mags, I've had planes start on me as I pulled the prop through to prime the engine. If you ever have the notion to pull a prop through on a full size, always do it backwards so the impuse coupler will not engage. It's best not to even touch the prop on a full size unless you know what you are doing.

RE: Beware of Surprise engine start
 

....that story, my friend is an "Old Mechanics Tale" designed to keep people from leaning
against airplanes....especially against the props. The explanation sounds good too, unless
a person (like myself) knows mechanical things about aircraft engines. That scenerio never
happened, and cannot happen. :eek:

But, thank you for sharing the "story" with us. ;)

FBD. :D

RE: Beware of Surprise engine start
 

I`ve seen a full scale prop strike . Big or small , respect anythng that rotates . Be safe !

RE: Beware of Surprise engine start
 

Well, IIRC the mags are grounded when switched off. So theoretically, if something happened to the ground, the mag would go live. But most likely, there would only be sparks becuase as Dave said the mixture is pulled to shut down the engine.

RE: Beware of Surprise engine start
 

I had somthing like this happen yesterday. I had been out in the yard tuning an engine and when I was done I carried the plane back into the garage put it upside down in my field box..

I started working with somthing on the table next to the plane... and dropped the screwdriver which fell on the prop.. The engine goes POP (with my leg VERY close to the prop).. and I nearly wet my pants.