As I walked toward a four-seat propeller plane with the metal nozzle of a fuel hose in my hands, Mark Goodwin told me what scratching an airplane is considered in his business.

''A mortal sin,'' said Goodwin, general manager of Northeast Air, a family-owned aircraft service and maintenance business located at the Portland International Jetport. ''When you do damage to an airplane, it can get very, very expensive. It's not like you bring it to the body shop. We can't afford mistakes out here.''

With that caution in mind, I listened to general aviation manager John Savage explain to me what I needed to do to fuel the plane.

First, we needed to ground the fuel truck and the plane to prevent static electricity. So we took a cord from the truck and clamped it near the wheel of the plane. We also made sure both the plane and the fuel truck were ''chocked,'' meaning they had heavy blocks placed behind their wheels to prevent them from moving.

''A big gust of wind could move the plane,'' Savage said. ''Or something could fail on the truck.''

He then showed me where the emergency fuel shut-off control was on the truck, near the front. Just in case.

I climbed a stepladder to reach the plane's filler pipe on top of the wing. Savage told me to lay a big plastic mat with a hole in the middle around the filler pipe opening. That way I wouldn't scratch the top of the wing with the heavy nozzle.

After unscrewing the gas cap, Savage told me to stick the nozzle in only 2 or 3 inches to avoid damaging the inside of the tank. And he told me to watch the fuel and stop pumping when it was an inch or so from the top.

He also told me the fuel was filtered three times before it goes into a plane. And that Northeast Air has to keep a sample of every shipment of fuel they get, in case there is a problem with a plane later. Northeast Air also does work for the airlines at the airport - refueling and repairs - but doing a refueling for airlines requires more special training and certification, and was not something I could take part in.

To fuel the private planes parked at Northeast Air, Savage and his co-workers in the general aviation division of the company move planes around quite a bit. They move them in and out of the hangars to different parts of the ''ramp,'' or what I would call the parking lot.

To move the planes - mostly small prop planes and medium-size jets - the Northeast Air crews use what they call a ''tug.'' It's a vehicle the size of a golf cart with a heavy-duty motor.

As we were preparing to hook a Hawker 700 jet up to the tug, Savage showed me the different tow attachments hanging on the wall, each labeled for the kind of plane with which it is compatible. We found the one for the Hawker, and I brought it over to the plane.

Savage had me fit the piece over the tow bar, a long iron cylinder on wheels that attaches to the tug on one end and the plane on the other.

''Be careful of your hands. Don't get them caught in there,'' Savage said, as I attempted to slide the tow bar and tow attachment into place. I did this while on my knees under the plane.

I had to take two pins out of their respective slots near the wheel and use them to lock the tow attachment into place. Savage told me it was important to put the pins back into the wheel base once we were done.

''If those pins aren't in place, the wheel won't turn and the pilots can't steer,'' said Savage.

That's one important pin, I thought.

After we hooked up the tow bar and tug, I sat in the tug's passenger's seat as Adam Miller, another general aviation worker, drove. He backed out of the hangar, pulling the plane. He was watching the two ''wing walkers'' - the men who were slowly walking along the wings of the plane to make sure there was no danger of contact with walls, equipment or other planes.

The wing walkers had whistles, which they are supposed to blow if they want Miller to stop. Because of all the noise from plane engines around us, it would be almost impossible for Miller to clearly hear someone yell ''stop'' or ''more to the left.'' Thus, the whistles.

Once Miller had pulled the plane out, Savage demonstrated some of the hand signals all the workers must know in order to guide pilots as they taxi out to the runway or come off the runway and park.

If you want the pilot to put his brakes on, clench your fists. If you want the pilot to turn his brakes off, open your fists. At least, I think that's what they said. And don't ask me which arm to wave for a right turn, because I'm pretty sure it's not the right arm. But I'm not 100 percent sure it's the left, either.

My point is this - there's a lot to learn when you're dealing with airplane safety. Workers have a lot of training and a lot of certification, and the company has to carry $25 million worth of liability insurance, Goodwin said.

But Savage told me it's a fun job, too. He likes meeting people who fly into Maine on private jets. On the first weekend that Maine's summer camps are open, families from all over the world fly in. Northeast Air's facility may see 300 to 400 private planes in one weekend.

''I like talking to people,'' said Savage, standing near the fuel truck. ''Sometimes a (pilot) just came in, with white knuckles, and I know to take it easy. Another guy might come in all smiles, and I can joke around. Everyone is different.''

Staff Writer Ray Routhier can be contacted at 791-6454 or at:

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