Monday, August 21, 2006

Part 4 of 4. Scroll down to read these in order so they make sense. This is not a feel-good story.

So what the hell happened? Why did VLH stop making engine sounds and then disappear behind the trees in a 60 degree banked turn?

The day after the crash when we were picking up the pieces of the airplane, Doug and I looked in the cockpit and there it was, staring us right in the face.

In the Cessna 185, the fuel selector is on the cabin floor, right between the 2 front seats. It's set up like a clock dial, with a single little lever. If you move the lever to the 9 o'clock position then it will feed from the LEFT tank. If you move it to the 12 o'clock position, then it will feed from BOTH tanks, and if you move it to the 3 o'clock position, it will feed the engine from the RIGHT tank.

Now here's the critical thing: This fuel selector is very similar to other Cessna fuel selectors. For example, in the Cessna 172, it's exactly the same thing, except that you can also slide the lever to the 6 o'clock position which is the fuel cutoff position - no fuel at all will be fed to the engine from either tank. In the 185, however, there is a piece of plastic that prevents the lever from moving south of the 9 o'clock or the 3 o'clock position, so you should only be able to select the left, right or both tanks for fuel.

In this particular 185, that was not the case. The plane had been rolled up into a ball a few years before, and while rebuilding it, the mechanics had used a fuel selector that had the fuel cutoff feature if you placed the needle at the 6 o'clock position. The piece of plastic that is supposed to prevent the fuel selector switch from being moved to the 6 o'clock OFF position was still there, but the mechanic had noticed that if you pull the lever straight up off the selector, you could wiggle it above the plastic piece and still pull it to the 6 o'clock OFF position. Again, none of this was mentioned in any airplane manual for VLH, and the mechanic later said he was the only person who knew about it.

He was also the mechanic who had done the last inspection on VLH, just before it took off on the final flight. He had been working on the fuel system and had moved the selector lever to the 6 o'clock OFF position to cut off fuel to the engine while he did some work on it. After the inspection was done, he had forgotten to move the fuel selector lever to the LEFT, BOTH, or RIGHT position, and it remained in the OFF position.

Unfortunately, even in the OFF position, there are a couple of gallons still in the fuel line between the fuel cutoff valve and the actual engine. In a Cessna 185, a couple of gallons is enough to do an engine run-up, taxi, take off, and get around 300 feet in the air before the gas runs out.

Because of the position of the selector switch between the two front seats on the floor, it's somewhat difficult to lean over and visually confirm the position. What we think happened is that when the checklist called for identifying the fuel tank selector switch position, Daryl put his hand between the seats and manually felt the lever. It was pointing to 6 o'clock OFF, but if he didn't know it could even point in that direction, he might have assumed it was pointing to the 12 o'clock BOTH position because the lever was in a vertical position, it was just pointing 180 degrees from where he expected it to be pointing.

In any event, he took off with the fuel selector in the OFF position. He got 300' in the air, and the engine stopped dead. This is a hard part to figure out, 'cause one of the basic things they teach in flight school is that if you engine quits and you are low to the ground, say below 500', you NEVER try to make a 180 degree turn, you land straight ahead. Daryl went for the turn. Why?

Now it's also important to know that the direction Daryl took off in was facing the rapids of Stony Rapids. We think that he saw the white water in front of him after the engine failed, and tried to make a 180 degree turn back to the safe part of the river, which would have saved the plane from flipping over in the rapids. At 300' up, he wasn't nearly high enough to accomplish that, and he hit the shoreline in the turn.

To summarize:

1. A Modification to airplane fuel system without anyone but the mechanic knowing
2. The fuel selector was left in the OFF position after inspection
3. Daryl failed to physically check position of the fuel selector, or misread it
4. There was enough fuel in gascolator line to get airborne to 300'
5. Daryl attempted to make a 180 degree turn at low altitude

So it took 5 distinct actions to cause this accident, maybe more. I have listened to many Transport Canada presentations on safety, and they all hammer home one basic thing: An accident is the result of many links in the accident chain, it's never just one thing. And this was a classic case of exactly that. If any of the following links had been broken, he would have survived the accident. If Daryl had taken off in the other direction, his taxi would have been shorter and he would have been higher up when the engine quit - or if his runup had taken longer, maybe the engine would have quit before the takeoff run. So many variables had to come together for this to happen, but eventually they did. Daryl was a great guy and he deserved better. He did make a couple of mistakes on that flight, and unfortunately he paid a really high price, as did his family and fiance. I think about him often and wonder where he'd be if the accident on August 7th hadn't occured.

How many times have you left a switch in the wrong position, like landing lights or maybe had the left mag on instead of both of them? have you ever nearly forgotten your landing gear or flaps or left the battery switch on after a flight? Stuff like that happens all the time, but the consequences are usually slight. I have had my share of missed items, but I have been really lucky in that none of them have resulted in an incident or accident.

Be careful. And be lucky.

7 comments:

Anonymous said...

A lot of links in the chain there. So sad that it cost a life. It's probably easiest to blame the mechanic because he's the one that's still around but as you point out, in the end, there were a lot of links. There are reasons that some things like the fuel selector are on the checklist more than one time but it's too easy to check it with just your hand... especially in a cessna with this configuration. I know I've done it exactly this way thousands of times. Runup, pre-takeoff, cruise, descent, pre-manuaver... thousands of times. I've reached down and touched that fuel selector to make sure that it's in the vertical position and never once considered that it might just be in the 180 degree off position. I mean, why would it be? The thing doesn't turn that way... usually. Thanks for sharing.

Jason said...

I wonder if this is one of the reasons that the fuel cutoff in new 172s is a separate red pullrod.

Taking the Off position for the Both position seems like an easy mistake to make with the old style.

Thanks for sharing that story - I imagine it was hard to write up.

Aviatrix said...

You can bet it is, Jason.

I almost conducted a take-off once in an old C172 with the fuel selector in the off position. I was checking out a pilot to fly and he had turned the stubby end of the selector to the 12 o' clock "both" position for the runup. The engine quit at the hold short line.

I hope my bag of experience fills up before my bag of luck runs out.

Dave Starr said...

Just wanted you to know how much I appreciated this series. It couldn't have been easy ... possibly a good thing for you to get it all out on "paper" for once.

I have to say I guessed the fuel selector back at your very description of the crash ... not because I'm smart, but because I'm old ... sadly similar sad stories were common when I was a boy ...back when we were barely getting rid of the third wing for two ;-).

There may be a reason still for a fuel cutoff position ... but there is no excuse whatever for the number of designs that allow such a mistake to be made so easily ... it's "biplane" thinking on the part of engineers who never touched a biplane... if Cessna finally made the change to something sensible as Jason mentioned, great ... it's only 40 years and who knows how many pilots too late in coming.

Anonymous said...

It's interesting to see the focus of the story after 9 years. The funeral/family/fiancee fade away in favour of the wisdom of safety issues which may well save lives.
It's a compelling read. And a beautiful balance between rational/analytical thinking and deep sadness. KM

The Big Pilot said...

I can't imagine how hard this was for you to write up.

My old flight instuctor was an ex-Air Force guy and once had an incident in a 172 similar to Aviatrix. He was adamant in his check list that the fuel selector be visually verified and added it, visual verification, to his checklist for the old 172s. If you didn't visually check it, you got a slap in the head.

I hope by putting this on paper you got a sense of closure. Thanks for sharing. Hopefully, other pilots and students will read this and learn.

Anonymous said...

A great post Sully. Thanks for sharing this with us. I have unfortunately had the misfortune of losing 4 friends in this business. It's never easy. And always leaves you wondering with an endless list of "what if's".