How aircraft fly, how to fly one
Dispel those pre-conceived notions
Dispel those pre-conceived notions
We all grow up with an inbuilt set of notions about how things work. Some we absorb from films or TV series, some from real life experience. So we know that if we push something off the edge of a cliff it will go out a bit but mainly downwards. And we think, from watching aircraft either live or on TV, that we know how they fly. For most people that's OK because they don't actually need to know.
But we're pilots so we need to know.
First of all, an aircraft will only fly because it's going along. Helicopters are different, and we'll come to that. So that thing with the twisty blades at the front pushes air backwards, literally screwing its way through the air (it’s sometimes called an airscrew) and pushing the air backwards.
Air always seems such a gentle thing: we push through it as we walk, it's hard to reconcile that with something that keeps a 747 in the air, but if concentrated it can be very powerful.
So your aircraft is going along. Now this has to be against the wind, so an aircraft going along the runway at 30mph with a wind from behind going at 30mph is, according to the wind, not moving. Turn the aircraft round in to the wind, however and suddenly it's doing 60mph against the wind. This relative motion we can do things with.
The stubby things on the side are simply bits of metal, they're nothing clever. Your hand will do as a "wing", so ride in a car (passenger is best, being a driver you generally need to concentrate a bit, although many of the drivers I see clearly aren't doing that), open the window, put your elbow on the door and point your hand forward outside. Now raise your wrist a little. Your hand is pushed upwards. That’s lift. Hand horizontal: no lift. Hand angled upwards a bit: lift. The higher the angle the more lift, but you feel more airflow so more drag, to a point at which suddenly the lift stops and your wrist dives down. So increasing the angle of your wrist against the wind generates more and more lift right up to the point your hand "stalls".
Wings are just big hands being pushed along by the airscrews (or the big "jet" engines which, for the purpose of this thought experiment) are just big airscrews with cowlings round them.
That’s how wings make lift. You do NOT get sucked up in to the sky by Bernoullis effect or by high pressure, low pressure, whatever your flight instructor might tell you but by the prop pulling you along against the air and the wings being slightly tilted up. Everything else is mumbo jumbo.
Helicopters: the airscrew is at the top pointing upwards and pushing the air down. Simple.
We use the little wings at the back we know as the elevators to angle the big wings up a little or a lot and that's how we control how much lift we can demand (more makes us go up, less makes us go down). The point here is that unlike the toy aircraft we use to amuse our children, we don't actually put the nose down to go down. Counter-intuitively putting the nose down actually makes the aircraft go faster and so the wings generate more lift, so we go up!
A "stall" is when you get the angle of the wing too high against the airflow by demanding too much lift. Popular fiction would have you believe you are stationary, but you're not, neither are you about to plummet (aircraft don't generally plummet). You just need to reduce the amount of lift demanded, so push hard, wait half a second then move the yoke back to where it was before to carry on what you were doing before, just don’t pull back quite as much. Unless you are very close to the ground stalls are not dangerous, merely inconvenient. The issue is that your natural reaction is "ground coming up, pull back!" and it's hard to overcome, which is why we have flying schools. My Instructor once said he didn't teach me to fly, he just stopped me from killing myself wile I learned.
The reason we have flaps at the back of the wings is they modify the wing shape to temporarily lower the stall speed so we don't take 2 miles to land, but at the expense of higher drag. In an airliner you often hear the pilots throttle up the engines after they’ve lowered the flaps, this is exactly why.
Let us also remove the preconceived notion that you fly an aircraft like a car, with two hands on the yoke. It is much easier to learn to fly with just the left hand on the yoke, with the elbow resting on either a handy support on the left wall, or on your knee. This leaves the other hand free to manipulate all the other stuff (radios, altimeters, fuel pumps, writing down clearances etc etc) and is also more relaxing.
It's also time to dispel the myth that you have to keep controlling the aircraft. The aircraft is best left alone and occasionally pointed in a slightly different direction. Less is more.
"It’s Pull back to go up, push forward to go down, yes?"
No. It’s a tad more complex than that. Pushing and pulling sets your speed, no more. Engine power (more for up, less for down) controls height. I know, it doesn’t sound right...
More engine power means more energy which you can choose to use by gaining height or speed.
Less engine power means less energy which you can choose to use by relinquishing height or speed.
Pushing and pulling is tiring and it’s very hard to maintain exactly the same amount of push or pull for more than a minute or so, and we get distracted so we have a trim wheel which, using springs, allows you to set a given amount of push or pull, at which point the aircraft will quite happily fly hands off. Pilots are taught the rule “Power, Attitude, Trim" (unless it's at the top of climb when it's "Attitude, power, trim”).
On the approach to land, where speed is critical, it’s best to set the trim for a given speed and fly hands off (not really, but not pushing or pulling, just turning the aircraft to line up with the runway and compensating for any wind gusts) down to the flare, using the throttle to adjust your position within the approach cone (see below).
The approach cone: imagine a huge ice cream cone, one of those nice brown ones with the pointy end resting on the runway just past those white numbers. The bottom of the wide round end is held 400ft or so above the ground and reaches about a mile away from the pointy end.
You fly in to the cone from the big end, aiming for a line that follows the middle of the cone down to the runway. If you’re flying within that cone you can land, if not then go round. There is no shame in a missed approach. Everyone misses them, from the lowliest student to the most hardened senior Boeing captain. We call it the “can I get it in from here?” cone.
When you start to fly approaches your cone will be very narrow indeed both horizontally and vertically. But as you grow in experience the cone gets wider and wider until eventually you learn enough tricks with flaps and sideslipping to be able to get it in from virtually anywhere vaguely within sight of the runway.
There is a smaller cone within it called the “Passenger” cone where you fly more conservatively so as not to scare the passengers.
Once you’re over the end of the runway past the pointy end of the giant ice cream cone at what could be described as single-decker bus height make sure you are looking at the end of the runway. Your gaze must not, under any circumstances leave the end of the runway. Pull the power off and every time the end of the runway looks a bit higher, pull the yoke back a bit more. Don’t panic about the stall Warner screaming at you, they’re all set miles too early. Runway end up, pull back. If the runway end goes down, freeze but don't push forwards. Once it starts going up again, pull back a bit more. A rumble from below will announce your failure to prevent the aircraft from landing correctly….
Take off is easy: set take off flap, push the throttle all the way in to the dashboard and hold it there. Push some right rudder to compensate for the engine power and slipstream, wait until the aircraft reaches your designated Rotate speed and pull back to get the aircraft free of the ground and all that grass drag.
But the trees at the end are looming. Must…pull…back…to…gain…height....
No.
Instead push like you're aiming for those trees.
You’ll gain speed, the wings will gain lift and force you bodily upwards so those tree trunks will slide down your cockpit view. You’re climbing. It takes a bit of courage and experience to know that is the solution but it does work.
Control laws: if you want a given movement apply the necessary deflection then immediately remove half of it.
Ooh, strong wind warnings… I can’t fly today.
Yes you can, if it’s straight down the runway and or within crosswind limits. It’ll just be bumpy. Wind is only an issue when it interacts with the ground either on or close to the runway. We’ve taken off and landed in 36G44Kts straight down tghe runway and it was just bumpy with short landing and take off rolls.
The scariest weather I’ve ever encountered was rotor off trees at the take off end of runway 24 at Kingsmuir requiring repeated stop to stop aileron deflection and a big push to keep the speed up because aileron authority is hugely dependant on speed, but once above the trees it was only a bit bumpy.
Let's remove the notion that flying is dangerous. Flying is no more dangerous than driving, but is less forgiving of mistakes. The general idea is to make the really bad mistakes early while you've got an instructor with you, and always to debrief after the flight either with someone or with yourself. Be brutally honest with yourself, and slowly the mistakes will lessen in importance. Try not to to make the same mistake twice!
A good example of this is mixing the Carb heat lever with the mixture lever. They both pull out, and when stressed it's easy to select the wrong one. I did it once on the downwind leg and nearly caused an inadvertent forced landing but I had an instructor with me and we both agreed that I would never, ever, do that again. So now, whenever I reach for the Carb Heat I hold the control and pause for a second, thinking back to that moment: double-checking it's not the Mixture control, before pulling it.
Another example is that I fly two different aircraft, one with toe brakes, the other with a hand brake. I once found myself rolling down the runway pushing the non-existent toe brakes like crazy as the aircraft failed to decelerate, so I now brief on every approach "hand brake today" or "foot brake today" and visualise my action.
After you've got your licence and you start going out on your own or with passengers you do need to make the mental transition firmly to Command. You are now "P1": you are legally responsible for the aircraft and all in it. Your weather decisions are now yours and yours alone, whether you comply with ATC's demands is also down to you. If you feel their demands are putting you in danger you have every right to question or refuse, don't be intimidated just because they are Bordeaux Tower or Miami Control and they are vectoring Airbuses and Boeings around. It is said that whenever there is an accident the Safety Board's findings are always "Pilot Error", which is a bit rude but reflects the fact that the pilot is where the buck stops.
And finally the saying "There are Old pilots, and there are Bold pilots, but no Old, Bold pilots" is true, to an extent, but you should temper that statement with the fact that if you never experiment you will never grow. Cautious experimentation is the name of the game here.