3tracks wrote:MTV
How can you tell which Mag. the impulse coupler is tied to?
Does the timing need to be retarded or advanced?
Tks. John

Generally (actually, almost without exception) the left magneto has the impulse coupling. The alternative is that some (not many) engines have impulse couplings on both mags. I've never run into an engine with an impulse on the right mag only.

The impulse coupling itself changes the mag timing effectively, so the "standard" timing of the mags should be the same. The only time the timing is changed is during the start.

Aircraft with key starters that have a R/L/Both/Start position have a shunt built into the ignition lock such that the right mag is turned off when the key is rotated to the start position. Thus, this feature is essentially transparent in those systems.

But if you have separate starter and magneto controls, ALWAYS start on left magneto only, especially with the new lightweight starters, which are much less tolerant of kickbacks.

MTV

MTV is spot on.
I would like to expand on the footing. He talks about footing and snow. I would like to suggest footing as one of the FIRST thing you evaluate-anywhere:
New leather soled dress shoes on smooth ramp....
Oil on ramp with dust covering....
With the younger generation I might add 'shoe laces tied'.....
Concrete ramp with uneven joints...
Gopher mound or hole in the backcountry...
Vines or long grass that can trip....
The list is as long as unique circumstances.
Footing is paramount on engines of ALL sizes, and determines whether it CAN be done, or what needs to be done to make 'safe' footing.

I also believe that the size of the engine and the height of the engine make a big difference on which technique is best (F or R) and how that technique is modified for the situation/airplane.
Big engines low (tricycle) are the most dangerous to hand prop. IMHO
Just because you can prop a 65 hp engine with ease doesn't make you an expert at them ALL.
Some big engine planes should only be propped in a 'no other choice' circumstance, and then only by someone with real world experience.

I am not claiming to be an expert at anything but my Cub. I have propped enough other airplanes with large motors that the hair on my neck starts to stand up just thinking about it.....
Think about the whole process if you are doing an unusual airplane to you. Evaluate. Consider. Walk through the process a couple of times without throwing the prop. Think about your body's center of gravity when and after the 'toss'. CONSIDER OTHER OPTIONS-like a jump start or calling someone with more experience (That-not an easy thing to do for us pilots).

Have someone cool and collected and smart-hopefully a PILOT-in the cockpit.

lc

Maybe I am doing things 'Backwards', but I have watched the video now....
My comment on the video is at the start he seems pretty casual about moving the propeller.
If I am going to move a propeller I want the carb 'dry' and the mags off. Not just off, but I want to have checked very recently that the mag switch/switches kill the engine. There is one little wire to each mag called the p-lead that grounds the mag to prevent a spark in the cylinder. If that wire vibrates off its post on the mag switch you have a hot mag ALL the time. If you always shut down with the mixture by cutting off fuel to stop the engine, you can go for a long time and not know you are carrying a 'loaded gun'!

I'll repeat.
DRY carb AND mags (for sure) OFF before you move the prop at all.

lc

I am assuming that the mixture is off and the gas is "run out" (burned) and the 'off' is competent for a 'DRY carb'.

Afterthought: The 'joy' of older/worn equipment is you learn some of these things 'firsthand'......
Moving the prop and having it fire unexpectedly will really STARTLE the crap out of you. What saved me was I ALWAYS treat the prop as 'hot' by staying out of the propeller arc.

Related:
http://www.sbw.org/pleads/


lc

Great thread! I was taught on a J-3 (front and back) and later when needed have propped our 172s and 182s. I'll echo all the good advice above. Footing is key and I'm glad that "palming" the prop blade was mentioned as opposed to gripping it. I think this is a very good skill to have, but it does demand the ultimate respect and is not to be taken lightly. Learn the procedure from someone experienced and then follow it verbatim...and make sure that the person on the brakes (if you have one) is fully briefed on what is going to happen and what you are expecting from them.

I've handpropped a 206 a lot, and that required propping from the front. Can be really exciting when alone in the middle of nowhere. With the 180 and 185, escpecially if on 29" BW's, propping from the front is a bit of a reach, and I'm 6'3". I flew a Champ and J-5 alot without an electrical system, both had lousy doors for hopping in in a hurry. I prefer propping from behind in every plane except the 206.

I know I posted before... but one last element to bring up. The advice to not let the joints of the fingers overlap the edge of the prop. Try as I might, all the years I hand propped the little Continentals, I could not do it without at least the first joint bending at the edge of the prop. Maybe it is just my hands. Others might be able to do it with flat palms and no risk during a kick back. Just did NOT work for me.

Littlecub wrote:If I am going to move a propeller I want the carb 'dry' and the mags off. Not just off, but I want to have checked very recently that the mag switch/switches kill the engine. There is one little wire to each mag called the p-lead that grounds the mag to prevent a spark in the cylinder. If that wire vibrates off its post on the mag switch you have a hot mag ALL the time. If you always shut down with the mixture by cutting off fuel to stop the engine, you can go for a long time and not know you are carrying a 'loaded gun'!.

A good solution to this conundrum is to ALWAYS switch the mag switch momentarily to the OFF position prior to shutdown, and see if the engine actually starts to die. If so, switch it back on quickly (this is just a momentary thing) and shut down with mixture.

Or, install an electronic tachometer, which tells you there's a hot mag.

MTV

MTV.... here is the problem. When you switch the mags back on.... and the engine goes BANG, all the aviators in the whole area go under the nearest table or truck. Then you can't find anyone to guard the controls while you hand prop the bastard !!!

I could not do it without at least the first joint bending at the edge of the prop. Maybe it is just my hands.

You and a whole lot of others.....
I think that is "ideal", but I think the point is to NOT wrap your fingers all the way around the edge tight to the backside. Just catching under the edge of the callous pad on that 'first pad' that is beyond/above the back edge of the prop is pretty standard. Minimal 'wrap' to get the job done, I would think.
With little engines, they are more forgiving with 'kick back'. Been there, felt that. On big engines (I have been told) "only wrap the ends of the fingers you can spare".....
That is one of the problems with 'low' engines. You either have to use more wrap or move your body too close to the propeller arc.

lc

You have probably figured out by now I highly 'respect' any/all propellers whether moving or not. (Chicken, big chicken)

This is an interesting thread. I am almost mirroring Grasstrippilots post. I have used both methods on Champs, Only from behind on J3's and float planes. The rest I have propped from the front but never propped anything over 180 hp.I've been around a float Beaver and even had some dual but it never occured to me that the compression was such that you could prop it.
What about gear drive Franklins and Rotax. The 100ULS must be impossible.
Chance

But how should you comb your hair first?

I have replied to this thread twice now and have hit the wrong button and deleted the damn thing so third time's a charm right?

Master Gump has the right of it, and now so have lot's of the others who have written in, I don't have much to add now except for some personal thoughts.

One thing I have not seen mentioned that is a real potential problem is that with any tail dragger that sits high on the mains, such as big tires or big gear will have the prop sitting at a "canted" angle to the ground, as in it will not be perpendicular to the ground.

If the plane has a high power engine or is hard to pull through so that it must be done from the front This means that when the prop tip passes the bottom of the swing it is a whole lot closer to your sweet flesh than it is at the top of the arc. My biggest fear on my plane is that a foot will slip or my knee will flex thus putting me in the food processor.

My engine has no impulse couplers and the timing is set at 25* BTDC so if you are going to hand prop this thing you want to damn well give it a REAL good pull. I like to get good, clear footing, prop indexed to a comfortable spot, then lift my left foot sort of like a baseball pitcher and when I come down hard I step back well clear. I don't do this if I have any other choice.

If you want to have fun sometime try a hand propping a champ in the winter, then add in a carb fire so that the only way to save the plane is to keep propping so it sucks the fire up into the engine. Now keep this up as hard as you can for say ten minutes till it fires and runs.. A great cardio workout.

What HAIR?

mtv wrote:A good solution to this conundrum is to ALWAYS switch the mag switch momentarily to the OFF position prior to shutdown, and see if the engine actually starts to die. If so, switch it back on quickly (this is just a momentary thing) and shut down with mixture.

Or, install an electronic tachometer, which tells you there's a hot mag.

MTV

Now, I've been told NOT to switch the mags back on again as it might cause a cylinder to misfire and damage the engine. Perhaps this is erroneous info. I will sometime switch the mags to off if I know I'll be starting it again soon or right away. I don't leave a loaded prop unattended.

GroundLooper wrote:

mtv wrote:A good solution to this conundrum is to ALWAYS switch the mag switch momentarily to the OFF position prior to shutdown, and see if the engine actually starts to die. If so, switch it back on quickly (this is just a momentary thing) and shut down with mixture.

Or, install an electronic tachometer, which tells you there's a hot mag.

MTV

Now, I've been told NOT to switch the mags back on again as it might cause a cylinder to misfire and damage the engine. Perhaps this is erroneous info. I will sometime switch the mags to off if I know I'll be starting it again soon or right away. I don't leave a loaded prop unattended.

If you accidentally switch the mag off when doing a mag check, don't switch it back, or it will likely back fire and could cause damage.

Doing it at idle is a completely different situation.

GroundLooper wrote:

mtv wrote:A good solution to this conundrum is to ALWAYS switch the mag switch momentarily to the OFF position prior to shutdown, and see if the engine actually starts to die. If so, switch it back on quickly (this is just a momentary thing) and shut down with mixture.

Or, install an electronic tachometer, which tells you there's a hot mag.

MTV

Now, I've been told NOT to switch the mags back on again as it might cause a cylinder to misfire and damage the engine. Perhaps this is erroneous info. I will sometime switch the mags to off if I know I'll be starting it again soon or right away. I don't leave a loaded prop unattended.

Yes, this is erroneous information. And, for Flightlogic, if you can't QUICKLY switch the mag switch OFF, then right back to both.....you probably shouldn't be operating complex machinery....

I'm not talking about almost allowing the engine to die here.....the point is, QUICKLY, MOMENTARILY switch the ignition off, then back on. If you hear NO difference in the engine, you've got a hot mag.

Sorry, but this is pretty basic stuff, folks.

MTV

My Stinson sits on 31 inch Ak Bush wheels. I am 5ft 10 in. with some good compression on the 165 hp. Franklin.
It has to be hand propped from the front with both hands. I flew out in to the back country of Alaska . The battery I had at the time would not hold a charge so I had to hand prop the plane. It can be intimidating looking up at the prop. I turn off the mags , pull mixture all the way out , turn off the starter then rotate the prop a few times before I even attempt to hand prop it. This lets me pump fuel in to the cylinders . I always check for my self and never rely on some one in the plane no matter who it is. Its my ass out in front of that prop. A lot of good info on this trend.
Safety first.

You can tell which mag has the impulse coupling because it sits further aft than the one without...about 3/4". The inpulse coupling looks like a 3/4"disc between the mag and the engine. If both mags are the same distance aft, you probably have two impulse couplings which you should be able to see as these 3/4" discs.

This is a virtual magneto assembly doohickey...click on each of the components then click on the install button...it really helps to understand these things:
http://www.undaerospace.com/cbt_files/virtualengine/Magneto/Virtual%20Engine.swf

Start with the components, then click on the component button and go to operation.

MTV is spot on. Footing is very important. Also, people have a tendency to do the "Great Waldo Pepper" leg kick which can actually pitch you forward toward the propeller especially on a small nosewheel airplane.

On the S-2 and the PBY it was normal to ground each mag individually and then use the center gang bar for both mags at the same time to make sure you don't have a hot mag. For me this carried over to all recip airplanes that I have flown. The procedure for the Kinner I have now is to shut the engine down with the mags not the mixture. I still check mag grounding when I start my taxi even knowing I am going to shut the engine off with the mags when I am done flying. To me this is even more important when the airplane is hand started every time.
I was propping an antique with a Le Blond with no impluse coupling or spark advance. The owner said it was usually hard to start and he was right. I cranked and cranked with not even a sign of life. Being a five cylinder the prop usually stopped at about the seven o'clock position. I told him to leave it hot and just pulling it through the bottom cylinder to re-position the prop it lit off. I have always treated a prop like it's hot and this was a classic example of why. I just stepped back with no problem.


I do have to agree with the comment regarding the video. The gentleman did seem very nonchalant around the propeller.

Again, front or back, both methods are safe when taught correctly.