Saturday, September 13, 2008

Clunk, Part I

Despite local doubt in our ability to progress, we taxi out at Oneonta. I get Lite Flyer to make the call, and she says something reasonably similar to "backtracking" before we enter the runway and taxi out. I think she had me do that takeoff but I don't remember. I remember watching the trees pass below as we climbed out over them, with my hand guarding the throttle while I waited for a suitable altitude and position to pull the throttle back to climb power. The motto on the airport sign was City of the Hills but there are still landable fields around, and where there aren't, there are lakes. It's very freeing having any calm water be a suitable landing site!

The airplane has two throttle levers, one for my right hand and on on the other side for Lite Flyer's left hand. That's a kind of odd thing, because you can have your hand over the throttle and someone else can move it. Lite Flyer hasn't scared me yet, though, because she makes very gradual throttle movements. She has to watch out when she is levelling off because this airplane has enough power to go through Vne in level flight at climb power. The manufacturer's checklist has "flaps as required" after takeoff and "flaps up" in the cruise checks. I have been "requiring" them up in the after takeoff checks, as it would be very easy to overspeed them at level-off. While I'm on the topic of cockpit controls, I'll make it clear that the airplane has dual sticks. The shared controls include the brakes and the trim. The brakes are operated with two hand levers that would fall under my left wrist if I had an armrest. There is one brake on each main wheel, with a separate lever for each. I push the levers forward to brake, a little counterintuitve at first, especially as the levers sit right where I might expect throttles to. The trim is a stubby lever right between the brake levers. It's probably my least favourite control, but I talked with the manufacturer and he tried it in a number of places and that seemed to be the best of a bad list for airplanes that required full dual controls. If the airplane was to be fitted with only one set of controls he could put the trim on the side and that worked better. The trim lever is quite stiff while the controls are very light, so I find that in this airplane I more often 'trim and test' and trim again than trim to what I feel right away. That may also be the fault of the fact that a very small travel of the trim lever makes a big difference to the trim.

I'm expecting four to five thousand foot ceilings for the latter half of our flight, but the winds will be so much better at 5500' that I ask Lite Flyer to climb that high. Reaching 4500' I hear a change in the engine sound that I couldn't testify actually occurred, but that I don't like. Maybe it's just the batteries running low in my noise cancelling headset. Or it's all in my head like the "automatic rough running" you get over inhospitable terrain. I look at the gauges. The cylinder head temperature and oil temperature are high, just as one would expect in a steady climb. They are no higher than they have been in other climbs, but something tells me I don't like it. I ask her to level off for a moment, and set cruise power, just to let the engine cool off a little. So sue us if we're at a wrong way altitude.

The engine changes sound as she sets cruise power, of course, and now I can't say if I still hear or if I ever heard anything I didn't like. We continue at that altitude for a while and the engine temperatures come back down exactly as one would expect. The engine does absolutely nothing unexpected. I feel rebellious and exposed at the wrong-way altitude--going northeast we should be at 3500' or 5500', not 4500'--but I don't tell her to climb again. There are a few clouds above us and she is uncomfortable flying when her visibility is not 360 degrees. And for that matter I can already see that the forecast lower ceilings are going to occur. But I don't ask her to descend, because the terrain ahead will be higher and altitude is life insurance. Plus I want that tailwind. I just can't believe that we are this far north and could still run afoul of a tropical storm.

Winds are just about perfect here, giving us groundspeeds over 80 kts. We reach the New York-Vermont border perhaps an hour and a half after takeoff. I muse to Lite Flyer, somewhat puzzled, about the scepticism that we would make it this far. "They have airplanes. Do they only fly around in circles and not know how small the states are here?"

The ski hills start at the Vermont border, but I quickly see that I have nothing to fear terrain wise. The ski resorts are on ridges which themselves are neither very high nor very wide, and the terrain between them is flat and cleared. I didn't even detour from the straight line route through the pass as I had planned. There was an area beyond the ski resorts where the terrain became crinkly for a while, but its saving grace was that it was dotted with lakes. With this airplane, lake equals landing site.

We continue over an area marked on the chart for heavy glider use, but we spot no gliders. Vermont turns into New Hampshire, which looks the same but is flatter and has bigger lakes. I am tempted to go down and do a touch and go on one, just for fun. The wind is still at our backs, the GPS tells us we'll be in Maine within both daylight and fuel range, and all is well. And then there is a loud clunk.

Lite Flyer had the controls, but we both heard the clunk. "What was that?" she asks me.

No bullshit from me. "I don't know. Was there any feeling from the controls when it happened?"

Nothing. She heard the sound, but the airplane didn't jerk. The engine gauges haven't budged, and the engine is running smoothly. I take control and gently test the control authority about each axis. There is no binding, no difference from before. I direct Lite Flyer to look out her side as I look out mine, for anything flapping, damaged, bent, odd in any way. Neither of us can see anything. All the flying wires we can see are intact. The wheels are still visible outside the windows. There are no feathers or blood on the visible airframe. The baggage is secure, has not shifted, and is composed of small cloth knapsacks, anyway. There's nothing to go clunk.

And it was definitely a clunk, not a snap, not a whump. I'll leave you in suspense for a while to wonder, as we did what that clunk was. I did find out. And let me tell you, my mouth went dry.

14 comments:

Steve at the Pub said...

Now you've got us on the edge of our seats.

All we know about the "clunk" is:
You are here telling us about it.

dpierce said...

You added the label "smashing" ... that has to be a clue. I just got done listening to a story about a tailwheel falling off, but that would be too coincidental. I'm wondering if the phantom changes in engine noise was a clue? I'll guess something fell off the engine and hit the vertical stab.

zeeflyer said...

I once heard a change in my engine noise, diverted back to the airport and found my short stubb of exhaust pipe had fallen off. But it didn't 'clunk' ... and fell into an unpopulated, wooded area, thankfully.

Apparently you survived whatever clunk was ... but did you end up ditching in one of those lakes...?

zb said...

I guess there are some clues in the introducing paragraphs of this post, but which are the hints and contributing factors?

Water as a landing site? Flaps? Something with the dual controls? Brake? Trim? Mid-air with an aluminum beer can dropped by a glider pilot?

Can't wait for part 2.
No! Sleep! Till! Part 2!

Anonymous said...

The whole trip, not just "Clunk," has made for a great story. Can't wait to read the rest. Guess you're OK since you're typing and all :) (pretty smart, eh?) The suspense is killing me though.

zb said...

I'm hitting Ctrl-R to reload the site every thirty seconds or something.

Anonymous said...

The adventure continues... with a cliff-hanger ending to tantalize the readers. Well done.

And only fair, as you point out you were also in suspense and wondering what would happen next with rather more on the line.

I imagine there was lots of time to think about what it could be. Wing pins/braces/control surfaces.. things you can't see, like the tail feathers.. I'm glad there's a part II.

Chris Prosser said...

Hmmm. Here's my WAG. Engine mount?

Anoynmous said...

Something breaking off would be a "snap". Something hitting the aircraft would be a "whump". A "clunk" gives me the impression of something coming unfastened and running into something else without actually coming totally apart.

The thing I can think of which would be able to do that without being visually obvious or affecting the controls would be a part of the engine that doesn't produce power. Perhaps something in the exhaust plumbing.

Soaring Student said...

Thermal expansion/contraction of something plastic, like the fuselage? Something that bowed in/out?

The last of the pop rivets gave out, and the splash guard swung around and went thump against the fuselage?

One if the wheels fell from the retracted position to deployed? But you visually checked that....

Whatever it is, it isn't structural (those go bang, fallowed by a falling sensation), it isn't the engine, and it isn't the control surfaces. Which relegates it to a worrisome problem, rather than a immediate problem.

After eliminating the most critical of what it could be, I'd bet the most worrisome thing about the clunk is that you don't know what it is. In any case, unless you've developed the body parts to fly on your own, my bias would be that a precautionary landing would be encouraged.

Anonymous said...

To my mind "clunk" normally implies something slow movement in something large and mechanical, which really means control linkage, undercarriage or engine mountings...I'm guessing that as you didn't get any sensation through the controls, and your sense of something barely noticeable with the engine during the climb that it's related to the engine installation, possibly a failed engine mount?

Anonymous said...

AWW Come on!! You can't leave us hanging like that. I was thinking a motor mount as well.

majroj said...

Drymouth (xerostomia)....a secret bottle of celebratory champagne blew in the luggage?

Small arms fire from the Jersey Pine Barrens? (Used to devil the dirigibles and blimps thereabouts).

majroj said...

Seriously though...takeoff, climb, level, clunk. Engine mt, pontoon mt..?