Zenith Aircraft Builders and Flyers
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Broke My Bungee!
I broke my nose gear bungee the other day and it caused me a few anxious moments in flight. I have read about others having their bungee break during landing or taxi. The description is that the nose drops a bit and the steering gets heavy, but here is adequate prop clearance to the ground. No worries, right?? Mine broke on takeoff from a grass strip that was a bit rough. The takeoff had quite a bit more nose gear bounces than normal before I had enough air over the elevator to hold the nose off. There was a fair crosswind so after lift-off I applied rudder to center the ball and the pedal went straight to the firewall without hardly any resistance. All us nose dragger Zenith guys like to complain about the rudder pedal force required to overcome the V-notch nylon block in the steering mechanism. I'm telling you, when that resistance is gone, you really know it!!!
I thought maybe something had seriously broke in the nose gear. In the 20 minute flight back to my home field, I convinced myself it had to be just a bungee break. Just for the heck of it, I did a low pass in from of the line guy at the airport and he reported nothing visually wrong from his viewpoint. As added precaution, I cut the mags over the numbers to have a stopped prop on landing and rolled off to the taxiway for a look-over. It was pretty obvious that I had a slight nose-down attitude, but there was still plenty of clearance from the prop to the ground.
I just replaced this bungee 1.5 years ago after getting 5+ years out of my original one with no problems. A new 1080HD bungee is on the way from ZAC. Should take less than 2 hours to replace assuming everything else is in OK shape. It's oil change time anyway so there's another reason to take the cowling off.
Here is the offending bungee at first look into the cowling:
Dave Gallagher
Replies to This Discussion
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Permalink Reply by Walt Snyder on
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Thanks, Dave, for posting this, should calm the jitters of those wondering what happens if that breaks. Can you see any reason for the break, i.e. wear, oil, heat, etc? It's interesting the original bungee lasted 5 years, do you have an opinion on why the new one lasted 1.5 years vs 5 years? Do you know where the break was, and if that area was subject to anything out of the norm that may have caused it?
Thanks again for posting this and detailing what to expect in handling, etc if it does fail.
Walt Snyder
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Permalink Reply by Mark Maltais on
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Looks like it snapped at the joint? Yours is a lot cleaner looking than mine... obviously oil wasn't a factor in this snap like mine... heat maybe?
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Permalink Reply by David Gallagher on
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I will try to do a post-mortem on the old bungee. Unfortunately I will not be getting to it for a week or so due to other comittments. Heat and oil should have not played a part. I will look for any unusual wear or signs of infant mortality. I don't want this to put a bad light on grass strip for me. I like to fly to as many as I can.
I wonder if any rough strip 701/750 guys go through bungees? Who knows, maybe lower speeds and bigger tires are actually easier on bungees.
Dave
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Permalink Reply by Wayne Tyson on
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In the photo, it looks like there's another spot where the wrappings were worn through . . . or are my eyes and inexperience fooling me?
Some Cajun is likely to come up with a new song, something like "I got a busted bungee; I can't go see my gal . . . " to the tune of https://www.youtube.com/watch?v=5aOPreYjMks
WT
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Permalink Reply by Paul Hajdu on
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Did you see any rubbing on the landing gear between the bungee pin and landing gear tube?
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Guys,
I have an update on my broken bungee. Work and personal schedules kept me from completing the replacement and test flight until just a few days ago. I used the ratchet wrench method of pulling the bungee over the gear leg pin instead of the ratchet strap method and it also worked well. Both methods are perfectly fine in my book.
Short story in my limited post-mortem on the broken bungee is I personally feel the bungee suffered from a quality issue. I found some rubber bands that were brittle. Fortunately I still had the original 2006 bungee I replaced back in 2014 to compare with. The broken 2014 bungee probably saw less than 100 landings while the original 2006 bungee saw close to 700 by the time I decided to replace it due to age concerns. Both bungees saw the same undercowl conditions and landing techniques. I am quite easy on my nose gear on landing (the light Jabiru engine helps) and I am the only pilot so I know that abuse was not the issue.
I will try to keep a closer eye on the new bungee I just installed. Problem is, you can only see if when the upper cowl is off. I am going to incorporate a push-down on the prop during pre-flight to see if I can spot an impending failure.
I have attached to this post a file with pictures comparing the 2006 and 2014 bungees.
Dave Gallagher
- Attachments:
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Bungee Break.pdf, 403 KB
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Permalink Reply by Ken Ryan on
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Excellent report. It appears the bungees are significantly different designs. I wonder if they are manufactured by the same company?
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Permalink Reply by Orville Neisingh on
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I just purchased a 701 and am replacing all of the rubber including the bungee. Can anyone tell me the best method for replacing the bungee as I have no instructions and do not want to try to reinvent the wheel, so-to-speak. Thanks for any help from this newbe.
Orv Neisingh N701WB
West Plains, MO
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Permalink Reply by david shrader on
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Great thorough write up thankyou.
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Permalink Reply by John Austin on
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FWIW: I had a bungee break just after landing, but it was a non-event with plenty of prop clearance.
From what I've heard - the bungees usually have a long life on the Jab's - the engine is light and that means the engine mount holds the engine even farther away from the firewall than heavier engines, so the bungee is not subject to much direct radiant heat or oil (although my engine doesn't leak, anyway!). I ordered my replacement from Spruce since they claim they sell "fresh" ones - indeed, according to the date code, my replacement was manufactured in the quarter just previous to my order.
My first bungee was probably 5 years old (came with the kit) - 3+ years in service and 280+ hrs when it broke. I'm still on the second at about 15 months and 80+ hrs - I'll certainly report if a premature failure occurs!
I notice that Spruce has a lighter-weight version of the same-size bungee available ("1080/750 lb test" vs "1080 HD/900 lb test"). I've always wondered if one had a bungee with a little less resistance combined with an engine on the lighter end of the spectrum (Jab 3300's are about 180 lbs with all the accessories, exhaust, etc. installed) if the reduced landing shock from not having to overcome so much resistance might actually lead to better service life? - Just thinking out loud here! ;>)
John
N750A
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I'm still getting some rattling in the nose gear assembly. I keep checking it out, but everything seems normal. Since I have the plane up for sale, I'd like to silence it. Were I the buyer, I would be unimpressed, to put it mildly.
Any ideas? The bungee is quite new.
WT
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