Vision: A Resource f

 Lazette Gifford
Publisher & Editor
zette@cableone.net

 

The Write Stuff:

Aviation for authors

By Robert Billing
2005,
Robert Billing

 

The dragon was coming in for a second run, claws extended, eighteen feet of silver-scaled leathery wings held in a rigid curve. Nicholas Verrin calculated frantically in his mind; seven, perhaps eight seconds until it would be in flaming range. But it was already in an unclean configuration, sideslipping with its tail hard over, pushing the edge of the envelope to lose height faster.

Nicholas turned to face the monster, watched its huge, dark eyes follow him, saw instant death flickering blue in its nostrils and ran, diagonally, towards the descending nemesis.

It kicked hard, tail flicking over, trying to reverse and steepen the sideslip, tendons standing out like wires in its wings. For a moment it was in trouble, aerodynamic forces tearing at its slab-like muscles.

A moment was all Nicholas needed. He pulled the wand from inside his robes and thumbed the safety. With a faint ping and a flash of blue-green fire it came alive in his hand.

Nicholas projected a simple, unfocussed spell that splashed red-gold against the dragon's hide.

It lost control, tumbling out of the sky in a rattling, clanging confusion, finally slamming into the granite setts of the roadway with a sickening thud.

 

Dragons and spaceships, talking eagles and vintage warbirds --  things that fly are are a staple of fiction that deals with action and adventure. If, as a writer, you can get the main characters off the ground, you have at once a planeload of problems and opportunities to weave into your stories. Your heroes can escape from the villains by air, or chase them in midair. They can get hopelessly lost in minutes, or search for the missing member of the party. You can even take the old standbys -- the crash, the mechanical fault that's going to bring the hardware down at the crucial moment, and the character who can't fly but suddenly has to take over the controls -- dust them off, repaint them in fresh colours and use them again.

Brian Lecomber, himself a display pilot before he took to writing, produced three excellent novels containing flying: Talk Down, Turn Killer and Dead Weight. These use many stock situations but combine them with complex characters and first-class narrative. Of the three, Talk Down is the most interesting to writers because, as well as telling a gripping edge-of-the-seat story, Lecomber teaches the reader to fly. There are several documented cases of people who have read the book suddenly finding themselves having to take over the controls of an aeroplane and pulling off remarkably successful landings.

Writing convincing flying scenes doesn't demand that level of piloting skill. A little experience -- just once having held the controls and made the machine turn, climb and descend -- makes a huge difference. Really high quality flight simulation -- the sort of thing that involves a mocked up flight deck on big hydraulic jacks -- is almost as good, but costs almost as much as flying a real light aircraft. Flight simulation software on home computers is almost useless for gaining experience; it can present you with the right images and sounds, but it simply doesn't feel like a real aeroplane.

Consider having one flying lesson if you can possibly afford it. Most flight schools will offer a "trial lesson" package which will give you an introduction to the hardware and about 30 minutes in the air.

To help you with your research I've put the technical terms that are worth looking up in italics like this.

Flying things stay up for one of two reasons. Either they are lighter than air -- balloons and airships for example -- or they have wings which move through the air. The rotor blades on helicopters are really wings -- technically a helicopter is a rotating wing aircraft.

Most of the flying things in fiction, from sparrows to space shuttles, can be thought of as fixed wing aircraft -- even if they flap. Understanding how a fixed wing aircraft works, and what the controls do, will let you write almost any sort of flying sequence.

Have a look at a fairly simple aeroplane, for example a single-engined Cessna. The wings, seen end on, aren't simple flat sheets, but an elongated teardrop shape, with the rounded end at the front or leading edge and the narrow, angular part at the back, known as the trailing edge. This shape, known as an aerofoil, has a slight bulge upwards, making the top of the wing slightly convex and the bottom sightly concave.

This bulge is what makes the aeroplane fly. As the machine moves forward through the air the shape of the wing deflects air downwards. Imagine standing on a skateboard with someone squirting a fire hose at you. Your body would deflect the water back towards the hose but at the same time you'd be pushed backwards. In the same way deflecting air downwards produces an upward force on the wing. This is called lift and is the reason aircraft stay up.

The lift has to be enough to carry the weight of the machine, pilot, passengers, cargo, and first-class drinks trolley.

Friction between air and the aircraft creates a force that tries to hold the machine back. This called drag. Aircraft designers keep this to a minimum by smoothing the shape of the machine into a series of graceful curves.

The last major force is thrust, which comes from propellers, jet engines, rockets or whatever it is that dragons use.

When an aircraft is flying straight and level at a constant speed the four forces balance: lift cancels weight and thrust cancels drag exactly.

Just flying straight and level isn't that interesting. You want to be able to go somewhere, and that means being able to steer and make the aircraft continue more or less in the direction you chose.

Have a look at an aeroplane and a bird. They both have tails which make them stable. The aeroplane's vertical fin and the horizontal tailplane both contribute to the weathercock effect that makes them able to fly steadily in a straight line.

To make an aeroplane climb you need to make the nose point higher. This increases the angle of attack of the wings and generates more lift, and up you go. However, it increases the drag at the same time and the machine gets slower. To keep climbing you need more thrust -- you open the throttles, or if you are a bird you flap like mad. This makes sense in another way; you have to work harder to climb a hill than to walk on the level.

To descend you do the opposite -- reduce power and point the nose downwards.

You control the aeroplane in the up and down direction by pushing or pulling the joystick or control column. This is connected, in a simple aeroplane to movable control surfaces on the tail called elevators. Pull back on the stick and the elevator folds upwards, the air flowing over it pushing the tail down and the nose up. This movement is called a pitch change.

If you let go of the controls now the nose will fall, the aeroplane will speed up, the nose will rise slightly, and the whole thing will go through a few oscillations before settling back into straight and level flight. To keep a climb or descent going there is a tiny control surface, worked by a hand wheel, called a trim tab, at the back of one elevator. This can be used to hold the elevators up or down for long climbs and descents.

Turning is a little more complicated. To make an aeroplane turn right you first make it bank to the right, left wing up, right wing down. Moving the joystick, or turning the control wheel or yoke to the right, moves little surfaces called ailerons, which are near the ends of the wings. In this case the left-hand one goes down, the right-hand one moves up, and between them they roll the machine to the right.

Once you have rolled to the right the lift from the wings isn't pulling straight up, it's pulling a bit to the right as well. The aeroplane will now start moving to the right. At the same time you push gently with your right foot on the right pedal; this moves the rudder and causes the machine to change the way it's pointing -- it begins to yaw to the right. If you get these movements exactly synchronised you can balance the angle of bank and the centrifugal force in the turn in such a way that the passengers' drinks stay right way up. There is an instrument called a turn co-ordinator (which is a fancy name for a ball in a glass U-tube) to help you do this. If the ball isn't in the middle you simply press harder on the pedal that it indicates.

When turning, you are using some of the lift to pull the machine around the corner. As always this increases drag, so you need more thrust. The steeper the turn, the more thrust you need, and the more centrifugal force you generate. This is the infamous gee-force that squeezes fighter pilots into their seats. Because you need to pull back hard on the controls to keep a high-rate turn going, this is sometimes known as pulling gee. A curious side effect of this is that it robs your eyes and brain of blood, which has all slid down into the lower parts of your body. This causes a blackout -- you can still feel the controls but your vision collapses down to a small grey patch and finally vanishes altogether. A small further increase in gee can be dangerous but, when younger, I pulled enough gee to black out several times in one flight, practising high-rate turns on a C150 Aerobat, and came away with nothing worse than a headache.

When the aeroplane slows down you can get more lift by pointing the nose higher. This increases the angle of attack, so that the airflow meets the wing at a steeper angle. This process can't go on forever -- you can't point straight up and stop. There comes a point when the airflow stops following the curve of the wing and breaks away in randomly churning confusion. This is called a stall, and when it happens the wings suddenly stop generating lift, drag increases sharply, and the nose drops.

The stall is more startling than dangerous. The recovery action is simple -- just push the stick forward and drop the nose even further to reduce the angle of attack and gain speed. An aeroplane will normally snap out of a stall in seconds and with a drop of a few hundred feet.

More interesting is the spin. If an aeroplane is turning when it stalls, the slower wing, on the inside of the turn, can stall first. The machine then yaws rapidly towards the stalled wing, with the result that the other wing never stalls. What happens now is called autorotation. The aeroplane flies almost straight down at very low speed, turning at the same time.

The spin is less disturbing than it sounds. It is a very slow flight phenomenon, and doesn't involve high levels of gee. The recovery action is simple -- stick in the middle, full opposite rudder, push forwards until the spin breaks and the aeroplane comes out into a dive.

A good flight instructor will put the machine into a spin and give the student time to read all the instruments, learning how to recognise the situation from the panel, before recovering.

The opposite of a co-ordinated turn is a sideslip. Applying aileron and rudder in opposite directions makes the machine crab along sideways. This is a very inefficient form of flight, and as such it's a good way of losing height quickly. It also puts a heavy load on the airframe, the rigid parts of the aircraft, and if taken to extremes can make bits fall off.

When designing an aeroplane the engineers have to compromise between making it fly efficiently at high speed -- which needs a flat wing -- and slowing it down enough to land -- which needs a wing with more of a curve. To get around this they fit flaps -- hinged sections at the back of the wings -- that can be lowered to "curve" the wings, giving them more lift at low speed.

Instead of a speedometer an aeroplane is fitted with an airspeed indicator or ASI, a meter which is operated by the pressure of air entering a little tube called a pitot head that points forwards. Because the ASI is operated by air pressure, its readings are affected by anything that makes the air thicker or thinner. Imagine two aeroplanes flying at the same speed, one almost on the ground and the other at high altitude. The ASI in the second one will be showing a lower reading because the higher you go the lower the pressure and density of the air. The altimeter makes use of this -- it's really just a pressure gauge marked in units of height.

Pilots find the way the ASI works very useful. If the aeroplane does something at a particular airspeed, it will do the same thing at the same reading on the dial almost regardless of the conditions. So if you make an approach at 65 knots indicated airspeed to a runway just above sea level, then on the next day approach an airfield on top of a mountain at 65 knots, the aeroplane will behave in the same way both times. Of course, when you land on the mountain you will really be travelling a lot faster and need more runway length to stop.

The ASI dial has several coloured markings to show the limits of safe speed. The green area is the normal operating range. Above it is the yellow section. The aeroplane will fly quite safely in this region, but suddenly banging a control into the stops can cause damage. The amount of control movement you can safely use diminishes with increasing speed, until you reach Vne, marked with a little red line on the ASI. The "ne" stands for "Never Exceed"; going faster than this puts excessive stresses on the machine and can cause failures, such as the wings coming off.

If you haven't got an ASI -- you are riding a dragon or the pitot head has been shot off by the enemy -- you can still see the attitude the machine is in from how far the nose is pointing up or down. You can also feel the airspeed through the controls. The faster you are going the more strongly the airflow presses on the aircraft and the more resistance you feel when you try to move the controls. Big airliners, which have power-assisted controls, often have artificial feel -- mechanisms that feed information back to the pilot by resisting movements of the controls.

Now you have mastered the basics let's try a circuit in an aeroplane: take off, once round the airfield, and land again.

Start on the runway, pointing into the wind so that it will help us get to flying speed. Open the throttle all the way and glance at the gauges to make sure the engines are working properly. We're starting to roll now, steering with the rudder pedals which are connected to the nosewheel. The speed is building up; the ASI is beginning to read. Have another quick look at the gauges. The ASI is reading higher and the aeroplane is feeling lighter, coming alive in your hands. Glance at the ASI; almost flying speed. She's thinking about going, she wants to go, so rotate, come gently back on the stick and we're off the ground.

Settle her in the climb, 500 feet per minute will do, and make a gentle climbing turn to your left onto the crosswind leg. Level off at 1000 feet, throttle back to cruise and turn left again onto the downwind leg. See the runway, over there? Fly parallel with it and run through the downwind checklist. Everything is looking good, so turn left again onto the base leg, throttle right back and descend. We're going to need flaps, so move the switch down one, two clicks and adjust the trim. Six hundred feet; turn left into final approach and line up with the runway. We're down to approach speed now and the controls feel soggy in your hands. Trim again, get her right and she'll fly the approach hands-off. Runway is coming up to meet us, so ever-so-gently come back on the stick to slow the descent. Close the throttle, finally. The main wheels kiss the concrete with a quiet thump and rattle, the airspeed unwinds, the nosewheel makes contact and we're down.

Like to try another one?

That's what flying is like on a nice clear day with the wind straight down the runway. In real life you will meet up with howling crosswinds, bird strikes, and weather so thick you can't see anything. Instrument flying, substituting the dials on the blind flying panel for being able to see where you are going, is a huge subject and beyond the scope of this article.

Now that you can fly the next step is to go somewhere, and that means navigation. It's perfectly possible to find your way around by following line features such as rivers, roads and railways. Lakes, woods and towns are clearly visible from the air and make good landmarks. The shape of a town or lake can easily be matched to its shape on a map; the easiest way is to count the things that go in and out: a river running north-south, two roads to the west and one to the east, for example.

Eyeball navigation can be helped along by instruments. A magnetic compass and an accurate watch are enough for most purposes. Correct the indicated airspeed for altitude and the effect of the wind, do a little bit of simple geometry, and you can find your way by dead reckoning. Your accuracy will improve with experience. There are several white horses cut into chalk hillsides in the west of England, and I used to practise by spending an afternoon finding all of them.

There's nothing like navigation to teach you about self-deception. It's very easy to see a ground feature and convince yourself it's the one you want to see, then do the same with the next until you are so hopelessly off-course that something horrible happens, such as suddenly realising that you have infringed the controlled airspace at somewhere like Heathrow, or that you are crossing the target area of a military firing range and a Harrier with a live weapon load is closing on you. Both of these have happened to me, though mercifully neither ended in tragedy.

It's up to you, the writer, to decide how you will use flight in your stories. Be prepared to do a lot of research. Read, search the web, network with people who fly. You can get a lot of background from the novels of writers who are themselves involved in or knowledgeable about flying, such as Brian Lecomber, Nevil Shute, Len Deighton, and David Beaty.

Try to find new twists on the stock situations, or concoct new ones. Think of new things that could cause in-flight emergencies.

It's important to try to master the language of aviation. Flyers are naturally calm, unflappable people who think things through quickly before acting, and this is reflected in the way they talk. The correct phrase is not "Everything's jammed solid!" but "I have a control restriction"; not "I'm going to crash!" but "Difficulty maintaining altitude." Don't shout, "It's coming to bits!" when a quiet "partial engine failure" conveys your meaning. And finally, should your characters find themselves hopelessly outnumbered in a dogfight, the appropriate term is not "There's hundreds of the beggars after me!" but "I'm in a target-rich environment."

 

Some useful websites:

Cessna single-engined aircraft (I learned to fly on these):
http://se.cessna.com/

The Nevil Shute Norway Foundation:
http://www.nevilshute.org/

An interview with Brian Lecomber:
http://genres.ukauthors.com/modules.php?name=News&file=article&sid=134

British Civil Aviation Authority:
http://www.caa.co.uk/

US Federal Aviation Administration:
http://www.faa.gov/