flying3

All the Trimmings Pt.2

Or - Why I still don't like flying with Dave.

by

Bill "Wingnut" Sherwood

Dave called me on the phone one Sunday morning, to ask if I could sit in on a test flight of a Metro that had just finished being rebuilt after a ground accident. I had nothing better to do, so I agreed to meet him just before lunch at the hanger.

The plane looked fine when I saw it for the first time since it'd been repaired - A few months before it was taxying along very early one morning on a 'bank run' with about twenty other planes, and due to a bizarre set of circumstances it had run into a Mitsubishi MU-2 and had about six feet of it's left wing tip cut completely off. A wing off another Metro had been found and the tip off that one grafted on, making it whole again. Of course, we, as the pilots, were a tad nervous about flying a plane that had a rather large chunk of wing grafted with a bunch of rivets & straps, so we gave it a thorough inspection before the test flight. Nothing significant could be found, and so after the engineers had finished the final touches, Dave & I and two of the engineers that had worked on the plane got in to see how it flew. (Pilots alway like to take the engineers along that do the work to the planes, as it's a sort of 'confidence' test!)

When doing the check in the cockpit, I thought that there was something wrong that I couldn't quite place ... But everything seemed to work ok so I just focused on backing up Dave as needed.

The first engine spools up nicely, with the ground cart to help the batteries; 11% RPM light off ... 28% boost the fuel to accelerate the start ... run the EGT up to ~1,000°C, short of the maximum 1149°C limit ... 50% starter cut out ... stable idle at 65%. Same again for the right engine. Flight controls full & free movement. Brakes almost non-existent. (Make a note of that for the engineers) Annunciator panel checked & clear. And so on ...

Dave ran out of things to check, and I couldn't think of anything else to add, so I called the Tower that we were ready. "Clear for take off", and we knew that they would be keeping a special eye on us because of the nature of the flight so if any fluids or smoke were to come out that we couldn't see they would tell us immediately.

Props to high RPM, EGT decreasing to normal, temps and pressures green and normal. Power lever coming up, and the torques & EGT's rising to match. No significant torque swing, plane tracking straight. 95kts comes up and we're committed to takeoff - The runway isn't long enough to stop now. 110kts, Dave lifts the nosewheel, and after another couple of knots the plane eases itself into its natural environment for the first time in months. End of the runway goes under the nose, so gear up.

And then it happened.

Dave started to command a nose up trim, which is normal for a Metro just after takeoff, maybe at 50' to 100'. Just above the tree line, in any case. He started to trim, and didn't stop, which was odd, I thought. I looked over and saw that he had a wild look on his face, and was straining hard on the controls. The plane was also starting to head back down to the ground, only a few 10's of feet below us ...

For some reason I looked down at the elevator trim position indicator gauge. Normally, the needle would be about halfway up the gauge and slowly climbing as Dave commanded 'nose up trim', but the needle was buried way *down* into the full nose DOWN position and getting further by the second. I knew immediately what the problem was, and so put both my hands around the back of the control column, locked my fingers together, and pulled ......

Whilst shouting to Dave, "The trim's back to front - Trim nose DOWN! " He did so and the heavy load started to ease. We were up above the tree line in seconds after that, and heading uphill. Whew! The Tower shouted over the radio, "Confirm ops normal???"

"Get back to you in a second," was all I had time for. The load was nearly gone, after ten seconds or so and I asked Dave if I could let go now. He agreed, so I slowly eased off the back pressure. Another few seconds later all was back to normal as if nothing had happened. Dave and I looked at each other and had a quick silent discussion - "Tower, we'd like to return for a landing right now thanks."

"Roger, make left circuit and confirm ops normal?"

"Ahhhh ... yeah, it is now."

In the 100 odd seconds it took to do the rest of the circuit, I tried my trim to see it if was afflicted with dyslexia as well, and it was. There's an emergency elevator trim on the Metro, but that seemed to work just fine. When we were heading downwind one of the engineers came up the front and asked us what had just happened.

Both of us replied, "Elevator trim's back to front!"

"F%&", he replied, and went back to strap in extra tight for the landing.

Now that we had some warning of what was happening, the actual approach and landing was totally uneventful, so we taxied back to the hanger somewhat relieved. The same engineer came up the front again to ask us the same question again, to which we replied more eloquently, "The f*&%$#g elevator trim works back to front!"

"F#%*&g George did that - I'll have words with him when I get out!"

He was pissed off, no doubt. Dave and I weren't exactly happy either, but the anger was to come later after the adrenalin had worn off.

Well, the George in question was waiting there for us as we pulled up and waited for the engines to cool before shutdown. The agro engineer waited for the big props to slow a little, then threw the door open and raced down the steps, grabbed the dumbfounded George by the collar and dragged him behind the hanger for a few minutes ... Not quite sure what happened, but I can guess it wasn't pleasant!

After confirmation by the engineers that the trim was working back to front, they quickly figured out was what wrong - The actual trim switches were installed (By George!) upside down, hence when you commanded a nose-up trim, it actually trimmed nose down. That was what was bugging me, but I couldn't put my finger on it! This is sort of like swapping the accelerator and brake pedals over in a car; If you wanted to stop, you would actually be making the car go faster, so you push the 'brake' harder, making things worse. Very hard to pick by yourself, and if there was an engineer in the pilots seat next to Dave, there would've been little chance that the reversed trim could have been picked up in time.

Oh, yeah, an hour or so later we did go up and do a full flight test on the plane, you know, stalls, Vmca (min airspeed with one engine operating) high G turns, etc. That was a hell of a flight in itself, but it doesn't seem so important now.

Just one of those day where Fate gets your attention, just to give you a peek of what's on the other side ...