Don't worry, I didn't crash yet!

[Mobius]

Yikes!  I went flying yesterday, and had a rather unique experience.  I rented a Cessna 172 to take up for a short cross-coutry hop for an hour or so, just to build up some time.  So I went to the airport and got the keys and AD's for the airplane, and did all my preflight checks and everything looked just fine.  The only thing I noticed was the nosewheel  looked like it was extened out too far, like someone was pushing down on the back of the airplane.  But this was a usual occurance when people tie the tail down too tight and the nosewheel doesn't settle back down when you untie it.  So I finished the preflight checks and taxied out and lined up at the end of the runway to take off.  I started my take-off roll, and everything was fine until I hit ~45 kts.  Suddenly the nosewheel started to chatter and shake the entire airplane, so I nudged the yoke back and lifted the nosewheel off the ground, which stopped the chatter, but by then I was at flying speed, so I continued with the take-off, and right when my back wheels left the runway, the airplane yawed to the left like I had jumped on the left rudder pedal.  When this happened, the nose jumped left and I rolled to the left because of the yaw, which was rather frightening 30ft above the runway.  So I jumped on the right rudder pedal to straighten back out and luckily everything went back to normal and I was able to climb out and stay in the pattern to come back and land.  I landed with the nosewheel off the ground for as long as I could keep it there, and luckily it dropped down below the chatter speed, and I went and parked it because I had had enough excitement for one trip.  The mechanics said it was probably the 'nosewheel shimmy damper' that was broken, which would explain all the nosewheel chattering, probably caused by a rough landing in the flight before (I wish those people would have maybe mentioned it or something ).  What I think happened was the nosewheel was off turned to the side when I lifted-off, and that caused the yaw, in addition to a bit of a crosswind.  I know it wasn't just the wind itself (unless it was an especially wicked gust), because I've flown in much worse winds than the wind yesterday.  Looking back I probably should have aborted the landing when the chattering started, hindsight is 20/20, but I'm happy with the way I handled it.  Oh well, it happens, and I'm still here to fly another day.

Edited:  Thanks Doug, I called it a chatter damper and it's a shimmy damper.

[Hagar]

Lucky. Bet you won't be caught out like that again. Sounds like that noseleg is due for an overhaul. These things are so reliable they can get overlooked.

The mechanics said it was probably the 'nosewheel chatter damper' that was broken,

It's called a shimmy damper. Maybe they should fit one of these. http://www.aviationtoday.com/cgi/am/show_mag.cgi?pub=am&mon=0502&file=0502lord.htm

[Mobius]

Lucky. Bet you won't be caught out like that again. Sounds like that noseleg is due for an overhaul. These things are so reliable they can get overlooked.

Is there a way to check something like that without charging down the runway to see if it's broken.  One of the first times I went flying after I got my PPL, the flaps didn't work, so every time since then I've cycled the flaps before flying to check them, but there's no way to check a shimmy damper or something like it, is there?

[Hagar]

[quote]
Is there a way to check something like that without charging down the runway to see if it's broken.

[beefhole]

One of the first times I went flying after I got my PPL, the flaps didn't work, so every time since then I've cycled the flaps before flying to check them

That's not on your preflight checklist? (just wondering)

Well, I suppose it's good to hear you're still with us Mobius  As Doug said, especially in aviation, live and learn.

[Mobius]

I'm wondering if the extended nose strut had something to do with it. Did you notice if it was any different after you landed?

Well, like I said, it's like that probably 50% of the time I go flying becuase when people tie down the tail, the pull the nose up, which extends that strut.  It wasn't much more than an inch or so different than normal.  When I checked it after I landed, it looked normal.  It's still somewhat of a mystery to me.

That's not on your preflight checklist? (just wondering))

It is now. It never was when I was learning and prior to that happening.  We would always check that there weren't any popped fuses, and that the electrical system works, but we never cycled the flaps.  I guess we should've.

[beefhole]

It is now. It never was when I was learning and prior to that happening.  We would always check that there weren't any popped fuses, and that the electrical system works, but we never cycled the flaps.  I guess we should've.

Interesting.  On our checklists its flip on the master, check the gauges, test the annunciator panel and put down the flaps.  Well, now you know

[Brett_Henderson]

When I first stick my head into a C172, it's .. " Battery on, beacon on, flaps down".. Then check the fuel gauges for "any" indication (to be later verified with a stick) check the beacon (our tower yells at you if you have a prop spinning and no beacon flashing). It IS on the the "Initial" checklist (flaps extended)...

Anyway.. unless your one guess is right (gust of wind).. I'd suspect that the nose-wheel and rudder weren't agreeing with each other and you had more rudder than you thought during the take-off roll. You'll get that, to a certain extent, when the rubber linkage (that keeps you from snapping the nose-gear when it touches down with loads of rudder in, during a crosswind landing) is worn.. Or.. when one too many students think you need to move the rudder, full deflection each way, while at the tail during walk-around

[Mobius]

Yep, with our checklists, the only thing you do before preflight is flip the battery side of the master to check the fuel level the guages read so you can double check the if the fuel level guage reading and actual levels in the tank are the same.  Right after start-up though we check that the alternator is good, that all the guages are set and checked for correctness, and all the radios, nav. equipment, and transponder are set correctly and tested, and that's pretty much it.  Just curious, when do you guys test the flaps?  I always do it right after checking that the instruments are set, and right before the run-up, but it sounds like you guys are doing it before starting the engine.

And yeah, with that gust of wind, HERE is the weather history from yesterday, and right after I went flying is when the only gust of wind was recorded in that history.  The only other time I've had a gust that would even be close to that one would be when the new airport was being built a couple of years ago and we had to use the taxiway as the active, and one day there was a steady direct crosswind out of the south (runway is 28 ) and because the taxiway is so close to the FBO building, which is about 100 feet south of the taxiway, the wind was blocked right until the point where you were supposed to touch-down, so everyone would come in with x-wind correction, until the last minute when the wind was blocked, and to stay on the 30 ft wide runway, you had to straighten back out, then be ready to put that correction back in to touchdown.  On that day, I landed right before the building stopped, so right after touchdown that gust hit me and weather-vaned me into the wind, and I was about 3 feet from going off the left side of the runway, but I kept it on, and watched as the three people landing right behind me did the exact same thing.  The guy landing right behind me even asked me how my landing went (jokingly) so right after he landed and did the exact same thing, I had to return the favor.

[Brett_Henderson]

I don't get to use my scanner much (oh boy !)..

Here's a portion of the checklist we keep in the C172s..




The last time a gust got me good enough scare me.. was at 5Y1 (Cedarville/Hessel, Michigan). It's a small strip carved into the trees in Michigan's western, upper peninsula. That day was so gusty and variable, we had to fly the pattern to get a look at the windsock and a feel for the wind, before landing... (took a photo.. you'll find a cropped version of this photo on 5Y1's page at www.airnav.com) )



The gust turned out to be a quartering tailwind  :o  and put me on the ground, wing high, nose-wheel first. Got it down, stable and centered after a good "bounce".. If I had it to do over.. I woulda gone around.. One of those poor decisions you get to talk about    ... and learn from  

[beaky]

Been there (nosewheel shimmy and uncommanded yaw); done that; got the soiled underwear,

The shimmy damper is basically a wee shock absorber, mounted usually on the right side of the gear leg, angled more or less horizontally so that it absorbs some of the energy produced by the nosewheel fork flexing or just shimmying for whatever reason.
Sounds like yours was stuck in the extended position (which would tend to force the nosewheel- and the rudder, because they're linked- to the left.
I was thinking at first that the over-extended strut was the culprit, but the damper is mounted on the upper part of that unit, so I'm not sure what happened to your damper, except that she's-a-no-good.

The usual left-turning tendency of a Cessna at high power but low airspeed just made it worse.

When anything at all seems amiss with the nosegear, it's best to not even taxi until someone looks at it, and if the maintenance guy shrugs, try a high-speed taxi test before commiting to takeoff.
And yes, don't tie the plane down in such a way that the strut is extended. That's not good for it.

I could be wrong about all this in your case, but I had a similar experience due to what I described above.


Here's an interesting article about the newfangled Lord dampers, which use neither gas nor fluid to do their thing; pretty cool idea!!

http://www.designnews.com/article/CA152921.html

[Mobius]

When anything at all seems amiss with the nosegear, it's best to not even taxi until someone looks at it, and if the maintenance guy shrugs, try a high-speed taxi test before commiting to takeoff.

I couldn't agree more.  If anything seems amiss, go ask someone about it, and if no-one is around, go flying another day, it's just not worth it.  The only problem in this case was I didn't know there was a problem until I was at flying speed, and I had to choice to fly and airplane I was relatively confident would fly, or try to touch back down with nosegear that was potentially cocked to one side.  Funny thing is, after I had landed and gone to tell someone about the airplane, they asked me if I was done flying for the night. Um, yes.

And yes, don't tie the plane down in such a way that the strut is extended. That's not good for it.

You're preaching to the choir here, I couldn't agree with you more.  I usually just leave a bit of slack in the tail tie-down, not enought to let the airplane swing and break the knot, but enough that it's not pulling the back off.  The problem is the airplanes I fly are the main ones used for training, so people who don't know any better crank down on the tail tie-down.  It's funny too (well not really ) but the eye-bolt used to tie the tail down has almost the entire bottom worn and ground off from people scraping the tail either on take-off or landing.

[Chris_F]

[quote]
I couldn't agree more.

[Mobius]

One of the most important things you can do is go talk to your mechanic if something doesn't seem right, it could save your life, and getting off the ground two minutes ealier isn't worth not asking.

As for the take-off, I was past the half-way point with a strong gusting cross-wind, so if I had tried to set it down with the nosewheel cocked, I could have shot right off the side or the end of the runway.  At the point I was at, I was going to have to set the nose gear back down at some point or another, so why not go flying and try to fix the problem, you only need the gear when you're on the ground, not while you're flying.  Luckily the problem sorted itself out with application of right rudder, and I was more ready on final and touchdown for whatever might have happened than I would have been at the instant I had lifted off.  Also, if you time your touchdown right and keep the nose up, you can stay off the nose gear for quite a while after touchdown, which is exactly what I did, so I was below the speed where the chatter occured, and didn't have as much of a problem when I was landing.  Overall, I know I could have done some things better, but I am happy with how it worked out.

[beaky]

We live and learn... and if we remember what we've learned, we live longer.

I've had some astonishing surprises while preflighting airplanes... the shimmy-damper thing is hard to detect sometimes; I found out about that the same way Mobius did.
There's nothing wrong with asking for advice- hell, if a wiser head thinks the plane's not fit to fly, why chance it? Which is more important: fly today, no matter what happens, or try to ensure that the next flight is trouble-free?

A good example: I have always been thorough with my preflight, but two critical things stick out in my memory...
first was the time my instructor decided to do his own inspection after I did, and discovered an aileron balance weight was missing. Might not have done any harm, but if it did...! Man, that would suck! Flutter; jamming. anyone? No? Me neither! I canceled my flight.
The other thing was when I was about to start up for a solo flight, and one of the CFIs ran out onto the ramp and told me to kill it. "did they fix that tube?" he asked... I didn't know what the hell he was talking about. turns out the brake fluid tube on one side had been badly crimped from hard landings (the main gear fairing was pressing down on it). I thought it looked OK, but he said "put your hand under there and feel it". I did, and my blood ran cold. It wasn't split yet, but it was close. Too close for my liking, as well as his. Another cancellation.

Now you can always pick me out on the ramp because I'm the guy who's fingering every nook and cranny of the plane...