23 May 2007

Shake, Rattle, and Roll

To continually improve my landing technique, which the Good Pilot Handbook says is one of the more important skills to know, I was practicing some touch-and-gos the other day at Erie Municipal (EIK) which has a pretty short runway of 4700 ft.

No offense intended, but the concrete runway there is not in the greatest shape, having some shallow wear-ruts and expansion joints which can make landings and takeoffs, well, interesting at times. As a bone-fide pilot myself (and speaking only for myself) I can say with good authority that pilots like interesting. Keeps ya on yer toes, if ya know what I mean.

Anyways, did three really good soft-field landings, where you keep the nose wheel off the ground until it just eases down from lack of airspeed to keep it up. I applied full power to take off after the last one, and as the plane accelerated it began to vibrate, getting more and more intense until I was convinced I had somehow gotten a flat tire.

Hmmm . . . interesting. Do I take a chance that there really is a flat and take off knowing my subsequent landing would be . . . um . . . troublesome (at best)? Or do I abort and check things out?

Accelerating through 45, 50 knots, vibration intense and still increasing.

Decision time.

Actually - no decision, really. (I know, I know - anticlimactic)

If there's one thing that's been fully ingrained in me by flight training and my instructor, it is the sense that safety is the most important skill a pilot can ever master, and I chose to exercise that skill right then and there. Because as I've mentioned before, gravity is always turned on and landing with possibly just two out of three fully-inflated tires would not be pretty. Probably mess up my day.

I pulled the throttle to idle, aborted the takeoff and as I taxied over to the ramp, realized that the vibration had stopped. Shut 'er down, got out, and my eagle-eye noticed no flat tires or any other obvious vibration-inducer. Such as a missing nose wheel or a broken gear strut. Even the shimmy-dampener on the nose wheel looked OK to me. Course I'm not an A&P mechanic but usually I can tell if something's broken or not . . .

Called over to McAir (my flight club/school) and spoke with our chief flight instructor. We decided to call the mechanic for a look-see, meanwhile he'd drive over from Jeffco, er, Metro Airport and we'd fly the plane back together, assuming nothing prevented it.

The mechanic on-site at Erie was an amiable sort as he hopped out of the golf cart he used to get from the hangar to where I was on the ramp. He examined the plane just as I had, but probably his trained eye knew more of what exactly to look for.

He found - nothing.

But he did explain that when landing or taking off on a less-than-perfect runway, airplanes can encounter a groove or rut and if you do it just right, you can set up a harmonic vibration (AKA mechanical resonance) in the wheel/airframe system.

He also mentioned that the Cessna Skyhawk 172 (which is what I fly at the moment) is particularly known for this fun feature.

And that it feels just like a flat tire. Huh. Interesting. Allrighty then.

Our CFI Justin arrived and sheepishly I related what the mechanic had said, feeling a little like the boy who cried wolf. "You definitely did the right thing" he said, reinforcing the safety mantra. He did offer that if that happens again, to add some back pressure (on the control wheel) to lift the nosewheel and see if that eliminates the vibration. But still better safe than sorry and no reason at all to feel embarrassed.

So then we took off without incident - no vibration, nothing - and landed back at our home base.

Still being a relatively new pilot with about 90 hours of total flight time, I am keenly aware of the important roles that safety and decision-making play in having a good outcome to a flight. As my time and experience build, I intend to keep those factors topmost in my mind.

One of the more sobering aviation 'zines I read is Aviation Safety. It contains incident and accident reports and it's incredible (to me) the way in which some pilots - even high-time pilots - make, shall we say, ill-advised decisions. Many of which stem from one of the factors that pilots are trained against - the "it-can't-happen-to-me" attitude.

Not that I will never make a bad decision but my goal (as is, I'm sure, the goal of most if not all pilots) is to minimize them and trust that my skill and experience don't get in the way of clear thinking.

And so far I have not made any bad decisions. Knock on wood. Forgot to untie the tail once, but that's another story . . .

Til next time . . .


Heather said...

I know you did the right thing- and I think people do get compliant not just with flying, but with other situations where we do it so often, we think it-won’t-happen-to-me.

A few years ago, two friends of mine, who were also former co-workers died (along with 2 others), when the plane they were flying in, to Las Vegas, crashed into the mountains in Utah. They were flying with a pretty inexperienced pilot, who ignored suggestions on her flight plan, and later the investigation found the crash was due to pilot error. It sounds like you can never be too careful, if something seems “off.”

Glad nothing was wrong with the tire, and you were able to continue on your flight. :-)

deb said...


I can't believe you are flying!!!! You sure have guts....glad to hear you are keeping your head straight...missed you at Phil's graduation