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  #1  
Old 04-22-2018, 09:12 AM
MountainU2 MountainU2 is offline
 
Join Date: Aug 2017
Location: Roseville, CA
Posts: 16
Default Tow bar and prop pulling for RV-6?

Hey all-

Iím 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 Iíve 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? Itís 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 Iím 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, whatís the best tow bar to buy? I need something thatíll fit in the cargo area.

Thanks. I know this is total noob stuff. But, well, thatís what I am.

Keith
RV-6 N91CN
KLHM, CA
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  #2  
Old 04-22-2018, 10:59 AM
pa38112 pa38112 is offline
 
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Location: Clarksboro, NJ
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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.
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  #3  
Old 04-22-2018, 11:47 AM
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RONSIM RONSIM is offline
 
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Location: Largo, FL
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Default 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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Last edited by rv7boy : 04-23-2018 at 12:26 PM. Reason: Added note to clarify which "Bogi-Bar."
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  #4  
Old 04-22-2018, 12:17 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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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
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  #5  
Old 04-22-2018, 04:36 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by MountainU2 View Post

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.

Keith
RV-6 N91CN
KLHM, CA
I use the Deluxe Cessna tow bar for my RV-8s. Works well and is collapsable. You may have to adjust the tailwheel bolt length and squeeze the cotter pin for a good fit.

http://www.aircraftspruce.com/catalo...xe_towbars.php

I don't pull/push by the prop unless I have to, or push the airplane using the HStab either. If I do, it's very near the root of each.
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  #6  
Old 04-23-2018, 07:58 AM
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Snowflake Snowflake is offline
 
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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.
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  #7  
Old 04-23-2018, 09:07 AM
Lars Lars is offline
 
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Location: Davis, CA
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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.
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  #8  
Old 04-23-2018, 09:14 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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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.
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  #9  
Old 04-23-2018, 10:35 AM
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Toobuilder Toobuilder is offline
 
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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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Last edited by Toobuilder : 04-23-2018 at 10:39 AM.
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  #10  
Old 04-23-2018, 12:14 PM
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rv7boy rv7boy is offline
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Default 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!

Don
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