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Tow bar and prop pulling for RV-6?

Hey all-

I?m new to GA stuff. I have 7k hrs of USAF/Airline jet time, but only about 100 hrs in the world of bug smashers. Bought our first airplane a few months ago, and I?ve been pulling it out of the hangar by the prop. Recently learned this might be a bad idea, even if I pull near the hub. My plane has a Hartzell blended airfoil CS prop.

So:

1) Am I potentially damaging my plane by pulling it this way? It?s a real PITA to get it moving with the tow bar, especially pushing at the tailwheel. Seems like a lot of stress to put on that axle/bolt. But my guess is that this was considered in the design, and I?m being lazy not using a tow bar.

2) The tow bar I have is kinda crappy. If I need to use the tow bar and avoid pulling on the prop, what?s the best tow bar to buy? I need something that?ll fit in the cargo area.

Thanks. I know this is total noob stuff. But, well, that?s what I am.

Keith
RV-6 N91CN
KLHM, CA
 
The prop pulls the plane a whole lot harder than you ever could. Many people warn against it, but I am of the opinion that they either don't know what they are talking about, or think that by warning they will prevent you from doing it the wrong way. I do not see how even pressure on both sides of the prop, applied right outboard of the spinner, could possible hurt anything.
 
You will need the tow-bar to PUSH the plane

Prop, near the hub, is fine for pulling, or the tow-bar -- but a tow-bar is necessary to control the "push back" ---- I use the Bogey RV bar, from ACS -- holds tight.

Ron

[Note: A Google search for "Bogey RV bar" returns a null reply. Try Googling "BOGERT BOGI-BAR" and you'll have several to choose from. It appears the Model 4-RV from the ACS chart specifies the model to fit the RV-6.]
 
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I pull my RV-6 by the prop frequently. I don't think damaging the airplane is a concern as long as you're pulling near the prop hub.

On the other hand, I'm very careful not to rotate the prop while I'm pulling on it. Occasionally, engines with hot ignition systems (broken p-lead, switch left on, whatever) will start with little provocation. I don't want to provide that provocation.

Here's a video showing an engine starting when it wasn't expected:

https://www.youtube.com/watch?v=Ypb6fEgLNpY
 
Not touching a stopped prop is good practise in general, just because there's always a chance you forgot the mags and happen to move it and it happens to be in just the right spot to kick over. At least, that's what I was taught from a very young age growing up at airports... Don't touch the spinning cutty thing at the front.

That said, the prop is designed to pull the entire plane, even through gyroscopic aerobatic manoeuvers, and to slow the plane, during descents. You aren't going to hurt it by pulling on it at the base of the blade near the spinner, even pulling one-handed on one side while you steer the nosewheel with the other. Get in the habit of checking your switches before moving it, and the prop will be just fine.

And on "tow" bars: Don't think of them as TOW bars, think of them as STEERING bars. As anyone who has had one fail will tell you, the damage it'll cause to your wheelpant isn't worth it. Just use it to steer the nosewheel, and provide momentum by pulling/pushing on the prop. There are very well designed steering bars that will very securely lock onto your wheel, and once in place are unlikely to come free even if used for towing. People will swear that it will "never happen." But the one time you don't quite get it in place (and don't realize it), you'll find yourself flying home 5 kts slower without your wheelpant.
 
Keith, I see you are local to the Sacramento area. I have the Cessna towbar that Carl linked. I bought a longer bolt and made some spacers so the towbar has more to grab onto. I'm at Rio Vista Airport (O88) during most workdays, roughly 10-3, at the Team Light Aviation hangar. Stop by and I'll give you some spacers. You'll need to order a longer bolt, I don't recall the length offhand but that just takes a moment to figure out.
 
Lots of different posts regarding you not hurting a prop by pulling on it at the root of the blade, with a lot of good theories on why it is not bad (prop already pulls airplane through the air, etc.).

When an engine is running at normal cruise power the centripetal loads induced on the prop hub and the root end of the blade are huge and likely counter a lot of the pull load induced by thrust.

Hartzell specifically states in their owners manuals to never pull on the prop blades.
Is that because they are being conservative because they can't assure people will always pull directly beside the spinner? I don't know.

Since I don't know, I acquiesce because they know a whole lot more about propellers than I ever will, so I try and always use a tow bar and encourage all of our pilots to do the same.
 
If you have ever taken a Hartzel prop apart you will know why pulling on the blade (even right at the hub) is a bad idea. There are very large ball bearings which allow the blades to change pitch. With engine operation the blades sling outboard and evenly load all the bearings. When you grab a blade and pull or push, you have a very good chance that you are applying all of the push/pull force, multiplied by fantastic leverage directly on a single ball. This ball will of course have minimal contact with the race, and consequently can brinell the race. Short answer, the engine needs to be running for the blades to take the "pull" force.

And yes, I used to "carefully" pull airplanes around by the hub.

Not anymore
 
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Welcome!

Hi Keith,
I looked back through your posts and it appears you didn't get the VAF Welcome! Usually a guy named Mike from Nevada gives it to ya, but I didn't see a post from him, so here goes:

Keith, welcome aboard the good ship VAF!

Hoping you enjoy the voyage! :D

Don
 
If you have ever taken a Hartzel prop apart you will know why pulling on the blade (even right at the hub) is a bad idea. There are very large ball bearings which allow the blades to change pitch. With engine operation the blades sling outboard and evenly load all the bearings. When you grab a blade and pull or push, you have a very good chance that you are applying all of the push/pull force, multiplied by fantastic leverage directly on a single ball. This ball will of course have minimal contact with the race, and consequently can brinell the race. Short answer, the engine needs to be running for the blades to take the "pull" force.

And yes, I used to "carefully" pull airplanes around by the hub.

Not anymore

I don't believe this. The torsional, centrifugal, and traction forces (forward bending moment) are so much greater than a push pull. No way. Show me some numbers. Races and balls are 52100 steel heat treated to Rc 62+

Now to the OP, I push pull, but I'm not tall or heavy so it is not much force. Getting the little wheel in the back to behave when pushing has become an acquired skill. I push, then align the little wheel with a couple of pounds on a wing leading edge as needed to effect a straight entry into the hangar.

On ice, a completely different story.
 
Who needs a tow bar....

I don?t have pictures handy, but to prevent having to keep a tow bar in the plane or push/pull on the prop I installed ?pull handles? they work great! A bonus is that I don?t put any undue stress on either the vertical or horizontal stabilizers by pushing on them.

I got them from BAS inc. they specialize in Cessna mods here is a link to their website. They no longer list the one for RV?s but suspect they could still make you a set.

http://basinc-aeromod.com/tail_pull_handles.php

I have No affiliation with this company, I?m just a happy customer.
 
1. Take one apart and report back.

And/or

2. I don't care... as long as you don't touch my prop.

I wouldn't, and have learned each person treats their plane differently and respect them all. I just can not see the brinelling theory as plausible, maybe some other issue, but not that.

I'm not taking a position in this debate. Here is a little more info from Les Doud of Hartzell props to help others form their own opinion:

http://www.vansairforce.com/community/showpost.php?p=835667&postcount=23

Les is the guy I would consider an expert, he's a great guy! He does note not to take 2 X 4's and twist the prop like some recommend. My composite is pretty thin and I only handle it by the root. This is only for the RV, too and is not unlimited.

Moderation and care is the key to longevity of many things.
 
Great information, guys. And thanks for the welcome!

Lars, I PMed you. I appreciate the offer.

I should have known opinions would span the spectrum on pulling by the prop. Can?t say I have terribly strong feelings about it, but there?s enough evidence for me to at least want a better tow bar. The pull handles are an interesting idea too, but I?ll need to read more about them.

In short, I plan to reduce my prop pulling as much as I can, and I hope I haven?t done any damage so far. I?d say it?s maybe been pulled 20 times by now. Any advice on what to look for in terms of potential damage? I know it?s not terribly likely, but, well...one engine...

Not saying I don?t buy the argument that the prop can handle it either. It?s a pretty light plane, and I?m not exactly the Incredible Hulk. But when I pull it out of the hangar, I need to make a 90 degree turn, which I?ve been doing by the prop. I?ve tried to be smooth and hold near the spinner, but there?s still been asymmetric force as part of the deal.

To provide a little more background, I started thinking about this a couple days ago after noticing a sort of wobble around the 900-1000RPM area during initial taxi out. It wasn?t terrible, and I was taxiing behind another plane at the time, so it could have been an airflow thing with his propwash. It also didn?t happen the rest of the day. But lying in bed later that night, I couldn?t help but wonder if I oughtn?t look into it further. Paranoia? Maybe. Regardless, I plan to go taxi around a bit when I get home this week and see if I can replicate it. I?m hoping I can?t!

Thanks for weighing in and helping a new guy. As an aside, this thread compelled me to end my lurking days and donate.

Keith
 
...To provide a little more background, I started thinking about this a couple days ago after noticing a sort of wobble around the 900-1000RPM area during initial taxi out...

My Hiperbipe had a pronounced "wobble" (spinner relative to cowl) at certain RPM and ground speeds. I attributed it to a resonance between the spring gear and the durometer of the mount isolators (mine were pretty soft). No such behavior in flight nor when stationary on the ground. Something to consider.
 
My Hiperbipe had a pronounced "wobble" (spinner relative to cowl) at certain RPM and ground speeds. I attributed it to a resonance between the spring gear and the durometer of the mount isolators (mine were pretty soft). No such behavior in flight nor when stationary on the ground. Something to consider.

Consider it considered! Did you do anything about it? Seems like as long as it can be pinpointed to a certain RPM range and reasonably attributed to something non-threatening, it?s NBD.
 
Consider it considered! Did you do anything about it? Seems like as long as it can be pinpointed to a certain RPM range and reasonably attributed to something non-threatening, it?s NBD.

I lived with it for a long time as it wasn't hurting anything. When the spinner started to dig into the cowl during hard acro however, I knew replacement isolators were needed. That fixed all the wobble.
 
The prop pulls the plane a whole lot harder than you ever could. Many people warn against it, but I am of the opinion that they either don't know what they are talking about, or think that by warning they will prevent you from doing it the wrong way. I do not see how even pressure on both sides of the prop, applied right outboard of the spinner, could possible hurt anything.

+1 here as well, but I have a fixed pitch prop. The root of the blades are very beefy and this is where I pull/push.
 
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