Sunday, September 14, 2008

Clunk, Part II

For best results, read Clunk, Part I first.

There continue to be no control difficulties, engine changes, or airframe flutter and I decide against an immediate precautionary landing. Or maybe I just haven't decided to make one yet. Absence of a decision is a decision, after all. There are as many good sites to land ahead as there are in the immediate vicinity, and the larger airport at our intended destination is in a larger town, with more resources, if we need anything. I'm trying to think of the most dire thing that this could be. Parts falling off are going to make a distant and inaudible thud or splash, not a clunk. And the moving parts on this bird are mostly fabric. They simply aren't heavy enough to clunk.

I know that there are some springs securing the rear of the exhaust system to the front of the exhaust system, and that they are a bit of a weak point. While Lite Flyer was up on her test flight at the manufacturer's I had a look at their demo plane, and noticed that it had a one-piece exhaust system. "There are no springs on this one," I said to the wiring expert who was with me.

"Yeah, springs break and go through propellers," he said. "This is the new improved kind."

The springs on this one are all safety wired and have that orange gunk on them that you use to tell if a nut is starting to back off a bolt. They were all intact and wired down before this flight. But maybe under the right conditions a spring can make a heavy clunk. Aviatrix, who knows perfectly well that springs go sproing tries to rationalize. If something had hit the delicate little composite propeller I'd expect an engine vibration. If I really thought it was a spring, I'd be landing already, because if one goes, then there's more strain on the others.

While I'm thinking, I reach in the side pocket by my seat for my water bottle. I heard once that even two per cent dehydration has a measurable effect on cognitive ability. But damn: my water bottle is not there. Did I leave it in the FBO when I refilled it? No I didn't. I reach down behind my seat, down in front of the fuel tank. I find my water bottle. You might recall from an earlier posting that I eschew plastic water bottles and have invested in metal ones. The kind that go clunk when you drop them against a fibreglass-kevlar hull. "Listen to this," I say to Lite Flyer, and I drop the water bottle again.


Mystery solved. In the best possible way. My mouth went dry because while I can reach my hand back there and grab the water bottle, the space my hand goes through isn't big enough to pull the water bottle out through. It's like trying to get a pop out of an old fashioned ice-chest style pop machine where you have to pull it along to the right spot after you put the coins in.

I could tell you about the rest of that flight, but it would be an anti-climax, wouldn't it. And you've probably stopped reading already to berate me for stringing you along. So I'll wrap it up quickly. New Hampshire became Maine under our wings, and other than finally descending to a right-way altitude of 3500', we stayed high because there are a large number of very tall towers in that part of Maine. We tuned up the ASOS for KLEW and it favoured a landing on the small cross runway, but there was a lot of traffic on a crossing runway, which curiously is zero four. I say curiously, because this is still the United States and these are American accents in US-registered airplanes, but they are saying "zero four" not just four. Everyone is doing it. Must be the Canadian influence. I don't believe the US has decided to conform to ICAO runway numbering overnight.

I hear student pilot radio voices and instructor radio voices. Three airplanes are doing continuous circuits and other traffic is departing and arriving, probably from the local practice area. While I could arrange our approach to go under the downwind, it could be tricky to coordinate crossing an active runway with different speed traffic. With it being busy and having students around i want to do the most expected thing. I direct Lite Flyer to fly towards a point that will allow us to join "downwind on the forty-five," the most common US pattern entry. I think she is confused why I am sending her the wrong way, but I don't spend the words explaining, because I am listening to overly verbose student pilot radio calls, and looking out for traffic, trying to make sure I don't cut anyone off. We join, fly a close-in circuit and I take control to sideslip us in and clear the runway. There are a lot of GA aircraft here and I park in an unoccupied space and then go back to the flying school to confirm we're okay there overnight.

We take on the usual division of labour, with me securing and inspecting the airplane while Lite Flyer goes to convince strangers to help her get mogas. She's good at that.


Anonymous said...

"my mouth went dry"

...very clever ;)

I must say, I feel lucky that I read the first post, refreshed and low and behold, you had posted the second part of the story.

What would I do without good old Aviatrix to add some suspense and adventure to my office life?

dpierce said...

ooh, that was evil. More!

Anonymous said...

Phew! If every in-flight "noise" turned out to be so benign.

Great story telling. Thanks

Unknown said...

PHEW ! The sheer relief and the euphoria that follows the gnawing anxiety, the doubt,the worry.

Yes, you had me thinking of some "non-vital" chunk of hardware departing in the slipstream, via the prop.

In my youth I watched the glass depart the handle-bar-end mirror and glide down astern to shatter on "landing" !...good thing the road ahead was clear!

Another inspiring account of your aviation adventures. Thanks .

Anonymous said...

"The baggage is secure, has not shifted, and is composed of small cloth knapsacks, anyway. There's nothing to go clunk." Cleverly misleading, thank you. In retrospect, I see you were still talking about baggage when you said "nothing", and water bottles don't count as baggage. Got it. :)

Anonymous said...

A clunk does have the capacity to be something sinister and it's good that you found out what it was quickly enough.

I had, on a training flight, a somewhat similar problem. There I was, doing tight turns or somesuch, when suddenly there was a very loud BANGBANGBANG reverberating around the cabin of the Cessna 152 I was flying. A (long) list of things that could have broken off and making that sound ran through my mind; a lot of the items on the list were quite critical for flight..

Luckily, before declaring an emergency and attempting landing on a suitable field, I felt a small tugging motion on my hips, coinciding with the rhythm of the banging. A short investigation later, I found out that the loose end of my safety belt was wedged between the door and the doorframe, with the end banging against the fuselage in the slipstream. A slowdown, a gentle opening of the door, a tug on the belt to get it back inside and pulling the door closed ended the noise. I didn't feel quite relaxed until I was safely back on the ground again, though..

Anonymous said...

I'm assuming that the spring-secured exhaust you're talking about is a Rotax 912. Speaking from experience, when one of those springs break, there's a noticeable change in the engine sound, even with the safety-wire backup holding it (mostly) on. Well, it's noticeable by a bystander on the ground during taxi; I assume at 75% power it'd be noticeable from the cockpit, even in a pusher configuration.

Anonymous said...

Lame. Trust broken... :)

Aviatrix said...

Lame. Trust broken.
I didn't lie to you. Would you rather I make up a story with a more exciting ending? Skip that event all together? Or tell it in a way that didn't allow you to share my apprehension?

I think more readers share dpierce's take on the story, and I'm happy with how I told it.

Samwise: The seatbelt-in-door emergency is a venerable one, to while many pilots have fallen prey. I worked with someone who declared an emergency for it. It does make a hell of a noise.

Interesting to see all the comments on these last two. Thank you for your insights, everyone.