Autopilot - Friend or Foe - By William "BBall" Ball - Page 1 of 2
The headlines told a horrific tale. A very
capable crew, flying a very capable aircraft full of passengers
heading home for the Christmas holidays, somehow veered off
course and struck one of the surrounding mountain peaks. They
were less than fifty miles from the airfield. The result:
of the 164 people onboard, only 4 were left to see that Christmas
of '95; the other 160 perished in a ball of flames and twisted
horror.
What went wrong? Was the aircraft airworthy? Absolutely. The
Boeing 757-251 is one of the most powerful twin-engine transport
category airplanes in the world. It's wing and engine combination
is a thing of beauty; and the auto-flight system is one of
the most sophisticated and safest to be found. Was the crew
competent? The Captain had many hours flying this type of
aircraft on this particular route, and the First Officer had
proven to be proficient in the operation of the big Boeing's
labyrinth of systems and controls. So why did the aircraft
hit the mountain peak? Good question. The obvious answer is
that the crew let the autopilot/flight guidance system lead
them astray; but, as always, there's a bit more to it.
In this article, I'll touch on how, as our combat flight sims
become more and more like the "real deal", we need to obtain
a better understanding of the things that will make our lives
easier in the cockpit, hence safer. My subjects here will
be some navigation and autoflight systems, and how we can
learn to better use them to our advantage.
In January of '97, I received word that my bid to fly the
757 had been approved, and I read the notice with a mix of
anticipation and apprehension. This was to be my first checkout
in a "glass cockpit" (most of the round-dialed analog gauges
are replaced by Cathode Ray Tubes, or CRTs), and I had heard
that since the airplane is rather sophisticated in it's autopilot/flight
guidance systems, the checkout was a real bitch. I was flying
the venerable old 727 at the time, and although it's truly
a wonderful machine, I knew that the most automatic thing
on the entire jet was the mirror light that came on in the
lavatory when you closed the door and locked it. Well, not
exactly, but the autopilot system is very simple when compared
to the "glass cockpit" machines.
I've since found that (like our simulations' flight guidance
systems) the very sophistication of the jet, is what makes
it an easy airplane to take from point A to point B. "No shit,
BBall, doesn't take a rocket scientist to figure that one
out." I guess my point is; don't let the world of the "complex"
overwhelm you when it comes to the systems on these aircraft.
They are there for one huge reason; to make your life better
(i.e., safer). Take the time to learn them, both their strengths
and weaknesses; then spend some time using them. So when the
"do-do hit's the fan", and the world is starting to feel like
you've missed the latest "brain patch", you can work these
systems to let them do the flying, while you do the thinking.
I've picked three very popular flight simulations to use as
examples in this article; two fixed-wing, and one rotary wing.
You've all heard of them, for they read like a who's who in
the world of "hardcore" sims: Microprose's Falcon 4.0, Jane's
F-18, and Razorwork's Commanche vs. Hokum. I picked Falcon
4 for it's TACAN navigation abilities, Jane's F-18 for it's
wonderfully articulate autopilot/flight guidance system, and
Commanche/Hokum just because I love helos and wanted to talk
about their modeling of two autoflight items very dear to
my "rotary heart".
Instead of jumping in with both feet to tackle an autopilot/flight
guidance system, let's start by talking about TACAN. Just
what the heck is it, and what does it do? No, it's not a new
Ricky Martin dance, it's an invention that enables you to
1) figure out just where the hell you are, and 2) provide
a means to navigate to where you are trying to go. Simple
as that….well, almost. In the civilian world we use what's
known as a VORTAC (don't you just love all the alphabet soup
involved with flying?). Which stands for VHF Omnidirectional
Range with TACAN capabilities. What did he say? (Don't worry,
the test that comes at the end of all this is open book, and
WE DO encourage cheating off your neighbor's paper). Basically,
it's a house sized building that has a round top with a funny
"golf tee" looking antennae sticking out of the top. It radiates
signals in a full 360 degree circle around itself. These are
called "radials"; there are 360 of them (obviously, one for
each degree around the circle), and you use these electronic
"beams" to navigate.
In the military world, it was found that use of the civilian
style VOR station wasn't going to cut the mustard. They knew
that they would have very different requirements, and the
use of the "house sized building", wouldn't work. They needed
their equipment to be mobile, and very versatile (i.e., the
in-flight movements of an aircraft, the pitching and rolling
of a naval deck, etc), so they developed TACAN. The technical
aspects of TACAN and VOR equipment are very different (VHF
verses UHF for one thing), but as far as the navigating pilot
is concerned, they operate the same.
So now we know that there are 360 radials "spoking" out from
each TACAN station, right? Let's break it down a bit further
to see what we have in the cockpit to use this wonderful invention
for what it was designed for…navigating. First, there's the
instrument itself. You will almost always find it in the form
of an H S I (horizontal situation indicator…pretty self explanatory,
eh?). Next, we have a window on each H S I that is called
the "to/from" flag. This sounds pretty obvious, and it is…it
tells you that you are either going "to" the station or "away"
from the station. We also have a "course needle" that has
the middle chunk of it movable to show if you are left or
right of course. And finally we have the CRS, or Course Set
knob. This is a small knob on the H S I that allows you turn
and rotate the course line within the instrument itself. You
still with me? Now, let's see how you might use this contraption
to figure out your location.
For instance, let's say you were wondering were you were in
relation to the KIMPO TACAN. You would dial in the frequency
(in this case 106 X), rotate the CRS knob on the HSI until
the "left/right" needle centers, make sure you have a "from"
indication on the "to/from" flag, and whatever the "course
selector window" says when the needle centers….that's what
radial you're on at that moment (regardless of your heading,
don't let that throw you). If it says 180, you are south of
the station, if it says 270, you're west, 040 would be northeast
and so on…. plus TACAN has the ability to display Range information
(in the civilian world, we call it DME, or distance measuring
equipment). So you turn the CRS knob until the needle centers
with a "from" flag, read the course and MI (miles) window
and, viola…"I'm on the 210 degree radial (southwest of the
station) at 105 DME". Once I was lost, but now I'm found.
If you're trying to fly TO a particular station, there's a bit more to it…but not much (a really cool thing about military TACANs is they can put one damn near anywhere, a tanker, a carrier, a liquor store). Simply dial in the freq., rotate the CRS knob until the "left/right" needle centers with a "to" flag, see what the course window says, TURN TO THAT APPROXIMATE HEADING, and fly inbound to the station noting your Range info. Do note if the "left/right" needle begins to drift one way or the other, signaling you that you're drifting off course; you may want to adjust your heading a bit for the wind. If the needle starts to move to the right, it means you are drifting left of course and must correct your heading to the right. In the sims we fly, you won't find 100kt winds like we do at altitude in the 757, but do keep an eye on the needle. It's called tracking a radial, and if I can do it, you can do it.
Now let's dissect the procedure to do this in Falcon 4. I HIGHLY recommend that if you don't completely understand every switch you are moving (and why), or you're like me and fly several simulations regularly, that you make a "checklist" if you will, outlining the steps….note; on the 747, just to balance fuel from the almost dozen fuel tanks, we used a checklist….not that it's all that complicated, but it just makes sense to do it by the book. I use a small 5 X 7 inch binder with note cards inside…works great.
O.K, we crossed the FLOT, hosed the DPRK big-time, but they caught us with a "magic bullet", and we've taken damage. No HUD, no MFDs…..crap, how are we gonna find our way to our emergency alternate of Mandumi? (Let's also assume that AWACS info is not available…hehe) First we start by ENGAGING THE AUTOPILOT (if available). There is an age-old axiom in aviation; Aviate, Navigate, Communicate. Don't let the aircraft become a "lawn dart" while you're heads down in the cockpit fiddling with the knobs and switches (a bit of what happened to the airliner in the first paragraph, but more on that later). Autopilot not available? Well then, you're going to have to know what your doing, why you're doing it, and do it pretty quickly between glances down and back outside the cockpit (couple that with flight control problems, and you've got yourself a tiger by the tail).
Here's where that checklist may keep dirt off the nose for you.
1) CNI switch on AUX COMM panel to ""BACKUP". This now changes your source of navigation data from what would have been preplanned info in the UFC (Up Front Control) panel, to the TACAN channel you will now manually set.
2) TACAN function switch to "TR". This sets the TACAN to receive a signal from a ground-based transmitter. Set to "AA-TR" to receive signals from an airborne transmitter (i.e., tanker).
3) Band switch to X (in this sim, X is almost always used for ground based equipment, Y for airborne).
4) TACAN channel selector to 73 X (Mandumi's TACAN frequency).
5) Instrument Mode Selector (left of the H S I), to "TCN". (NAV or NAV/ILS uses steerpoint, markpoint, datalink or ILS info).
6) Now we follow what we've learned from above. Rotate the CRS knob on the H S I until the "left/right" needle centers with a "to" arrow in the "to/from" indicator, fly that approximate heading, and adjust for any wind that may cause you to be drifting off course….noting that if you're doing it correctly, the MI indications should be getting smaller.
Unfortunately in Falcon 4.0, the autopilot will not track to the TACAN for us. Of course, in the real world it would either be able to do that or allow us to steer it via a "heading select" function. Having never flown a Viper, I'm going to go out on a limb here and say that the flight guidance system in this sim, is no where as complicated as the real deal (at least I hope so, or we've paid a lot of cash for something with a REALLY basic autopilot). We basically get one of three choices for autoflight, and we decide this in the Setup GUI. You decide whether to have your basic "Three Axis" autopilot that will just fly you straight and level when engaged, or "Steerpoint" that will take you to the current steerpoint, or "Combat" where it will do the whole enchilada (including fight) for you. Not totally realistic, but it gets the job done I guess.
With that said, in part two we'll talk about an autoflight system that really rocks (other than the one in the 757). I've been impressed by many things in Jane's' latest (and/or last) flight sim by the name of F-18, and the autopilot system is just one of them. This baby can do a ton of things for you, up to and including getting your tail back on board the ship. If one could couple this with an autothrottle system, you'd have yourself some real life "pilot heaven".
