the Trimmings Pt.2
Or - Why I still don't like flying with Dave.
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
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,
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
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%
cut out ... stable idle at 65%. Same again for the right engine. Flight
full & free movement. Brakes almost non-existent. (Make a note of
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",
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.
lifts the nosewheel, and after another couple of knots the plane eases
into its natural environment for the first time in months. End of the
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
back to normal as if nothing had happened. Dave and I looked at each
and had a quick silent discussion - "Tower, we'd like to return for a
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
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
the big props to slow a little, then threw the door open and raced down
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
yourself, and if there was an engineer in the pilots seat next to Dave,
would've been little chance that the reversed trim could have been
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
high G turns, etc. That was a hell of a flight in itself, but it
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 ...
from the NZ Flanker sim group
Page & contents where
applicable © Bill Sherwood