Monday, June 16, 2008

We Control the Horizontal

I'm advised that I'll be doing my much delayed pilot proficiency check this week. That means that if I get the job I'll have two career-critical flight tests right after one another. Lovely. This one can serve as the warm up.

Fortunately regulations require me to have training, not just go straight to a test, even though this is the airplane I normally fly. Well it isn't exactly. I'll be doing the test in an unfamiliar airplane, not even owned by my company, because the company airplanes are busy working and company hasn't been able to schedule them home in in a way that works out. This particular airplane is a different version of the airplane I normally fly for work. I'm not worried about that, because I've flown all the versions of this model and am familiar with the way they vary. I think the examiner will probably cut me some slack if I rattle off the numbers for the more familiar plane. The pilot who flies this airplane every day gives me a sheaf of paper to photocopy, not only the numbers for the airplane itself, but a bunch of helpful notes left over from his own training.

The test will include my ability to use the autopilot, yet this autopilot is not the same as the one I use at work. There is no standard interface for autopilots, and the complement of things they can do isn't a given, either, so you really have to learn how to use one, not just figure it out as you go along. Before the first day of my PPC training I took the autopilot manual home with me, to get acquainted. Curiously, the autopilot has the same name as the company I just interviewed with. I won't try to interpret that as an omen; I'll just leave it as a hint for those in the know. I pretty much gave it away already anyway.

I started out trying to blog about the Bilby autopilot but I figured I'd better explain a little about autopilots in general first, and well my explanations are a bit like my movie synopses. So here's the first part.

In order to tell an autopilot which direction to fly, you have a heading bug a little pointer that sits on the rim of the heading indicator and which can be positioned, with a knob or by keypad inputs. It shows the heading you are asking the airplane to fly. Many non-autopilot-equipped airplanes have heading bugs too. They are useful to remind the pilot where she is supposed to be going, or to help her crab to hold a radial in wind. This autopilot has one, and it is controlled with a knob on the right side of the horizontal situation indicator. There is another knob on the left side, the OBS, which is used to select the radial of a VOR, or the localizer track to the runway. Airplanes are not standardized on which is on the left and which on the right, so a pilot should look at the symbols before twisting one of the knobs. The OBS has an arrow and the heading selector has a pentagon, the same shape as the heading bug. The heading bug can be different colours, too, and you might be surprised how distracting this can be. This one is orange, a pretty standard colour, but I've had them yellow and green for sure, and possibly other colours too.

If the autopilot is on, working, and the heading mode is engaged, and you turn the heading bug to a heading more than a few degrees away from the current one, the airplane will roll into a standard rate (3 degrees per second) turn. and roll out on the selected heading. If you turn it to a heading very close to the current one, it will still roll, but but at a shallower bank angle. You have to be careful if you want a turn of close to or more than 180 degrees to move the heading bug part way and then wait until the airplane has turned far enough that it won't try to take a shortcut and turn in the opposite direction.

I mentioned the heading mode. You put the autopilot in a particular mode or combination of modes to tell it what you want it to be doing. For this particular autopilot to engage heading mode from not having the autopilot active at all, I would push the command wheel steering button (on the yoke) to reset the flight director, then press the HDG button, then move another switch forward to engage the autopilot. The HDG light on the dashboard panel should now be illuminated, and the airplane should continue to follow the heading bug when I turn it.

It's usually pretty good at that, holding the heading to within a few degrees and correcting promptly when turbulence causes a deviation. In this particular aircraft the alignment of the autopilot to the bug is a little bit off, so I have to align the left edge of the bug, not the centre part, with the intended heading. I get used to that soon enough. That alone is a pretty convenient feature. It allows a pilot to look up things in a manual, read a chart, eat lunch, retrieve dropped items all with hands off the yoke. You still have to keep a lookout, but it's a big help. It's also very useful at night or in IMC if you get momentarily disoriented, you can have the airplane fly for a few minutes while you scan the instruments and reassert in your brain which way is up.

4 comments:

Sarah said...

SO.... Would Bilby going to make you sit sideways at first? I suspect you've enough time that is unlikely, but I'm wondering what that would be like. I think I'd hate it, unless clearly time limited. And yes, you gave too many clues. Even I got it.

majroj said...

What, fly SIDE-SADDLE?....
Sorry couldn't resist, no more than I can resist relating the image I got of the Acme AutoPilot, as endorsed by Wile E. Coyote; you input 180deg, and it pulls an Immelman.

Aviatrix said...

Essyay on the idewaysay, and majroj I have a story about such a manoever coming up for you.

Anonymous said...

I just hope it's not KFC. Working for the Colonel is not as good as it seems from the outside.