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Idiot cat

We have two cats. We got them the same day, but one is about nine months older than the other. The one we got as a very small kitten, Loki, is Xander’s cat. He picked her up upside down, held her in weird positions, and she grew up with my last dog, Ace, a Rottweiler. She thinks she’s a dog. There is a very distinct difference between her tail lashing when she is upset and her tail wagging when she’s happy.

Just think about that for a minute. Have you ever seen a cat wagging its tail?

Loki deals with Nyx pretty well. She messes with her on a regular basis. Loki will lie down on her side on a chair and make mewping noises until Nyx comes over to investigate. Nyx’s head is about the size of the cat. Nyx nudges Loki. Loki smacks Nyx across the face with no claws. Nyx thinks about wandering off, and Loki calls her back. This continues until Nyx nudges a little too hard, at which point jut the tips of Loki’s claws come out and Nyx backs off. Loki is definitely in charge.

Eris is my cat. When we got her she had already been through three homes. One, her original foster home, was a good home. The next place adopted her and decided that she had too much energy for their older cat. I’m not sure what they expected, since they got a kitten, but people are sometimes odd. Instead of taking her back and saying it was not a good match, they gave her a room all to herself. Maybe they thought they were being nice. I don’t know. In any case, shutting a kitten up in a room is a bad idea. She decided to dig out under the door. The floor was carpeted, and she started ripping it up. Unfortunately, the people who had her had sprayed that carpet for ants. Eris got very sick and eventually went back to the first home.

When she was about four months old, she got an infection and the vet had to remove one of her eyes. As you might imagine, this did not endear her to potential adopters.

The third home was not awful, but Eris was still not very good at navigating with only one eye. She fell off of a bookcase and hit a table and the socket bled, so the owners freaked out and sent her, once again, to the foster home.

Xander and I were looking for cats who were at least part Russian Blue. He really likes the breed and I didn’t have much opinion. Eris’ mother was a full Russian Blue, and I asked if we could adopt her, but by the time I came across her she had been adopted. The foster home asked if we might be interested in her daughter and sent pictures. I thought she was beautiful, and we adopted her.

Eris is gorgeous. Sleek, small, and delicate, at least when she’s not being clumsy. She is not, however, the brightest cat I have ever met. She gets stuck in cupboards, hasn’t figured out how to boss the dog around, and, if she’s really irritated, she pees on things. Apparently she doesn’t like papasan chairs. No idea why, but she made that quite clear. Pungently. She also pees on the dog’s bed, given the chance.

Nyx periodically takes cushions off of the couch. We put planks on the cushions if she’s doing it too often, since a while ago she pulled off the cushions and dug a small hole in the inside of the couch. A few days ago she pulled a cushion off just as I was getting ready to leave. I put it back on, put the planks over the cushions, and headed out. A few hours later, Xander mentioned that my cat was an idiot. In the time that it took me to get the cushion and put it back on the couch, my cat dove through the hole and stayed there until Xander sat down. He heard her meowing (we call her the crabby cat because she had some damage to her vocal cords, too, so her voice is scratchy) and, after opening every cupboard in the house (she gets stuck in those pretty often, too), he finally found her under the couch. He had to widen the hole in the couch for her to get out again because she couldn’t figure it out.

The combination of a dog who is still a little bit of a puppy, a cat who is rather short on brains, and another cat who seems to take perverse joy in bothering the other two (about five minutes after Loki met Eris she started jumping her from her blind side), we are never short of entertainment or irritation, depending on our moods that day.

My cat is not very smart, but she is a sweet cat and, despite being terrified of Nyx, she comes and sleeps on my lap. I can live with that.

METARs

KRNO 241155Z 30003KT 10SM SCT200 04/M06 A3012 RMK AO2

Pilots just beginning to learn to fly get to see that for a weather report. I responded with “…what?” and my instructor laughed at me.

This is a METAR, an hourly meteorological observation report. If you aren’t a pilot or don’t want to become one, you will probably never see one of these. If you are a pilot, aspiring or active, these are very important. You should check the METAR before every flight, especially if you live someplace with, shall we say, variable weather.

There are a few tricks. The first is that the first three things on the report are all Ws – Where, When, and Wind.

Where, in this case, is KRNO. That’s the RNO airport, or Reno, in the United States (thus the K at the beginning, which signals the US – each country has its own indicator).

When always has the date first (just the day, though, not the month or year, as the assumption seems to be that you ought to know at least that part of the date) and then the time, hours and minutes, in Zulu, which is aviation and military for Greenwich Mean Time. It’s good to know where you are in relationship to Zulu time so you can tell how recently the METAR report was recorded. You should also be careful, as the relationship with Zulu time changes with Daylight Saving Time. For Pacific Time, Pacific Standard Time is Zulu -8 and Pacific Daylight Time is Zulu -7.

Wind has a few things you might see. In this report, it is 30003KT. The first three numbers, 300 in this case, are the direction of the wind. This could be VRB, which stands for variable, if the wind direction is not consistent. 03KT means the wind is at 3 knots, which is not very much wind. You may also see something like this: 36007G15KT, which would be wind coming from 360 degrees (straight north, for those of you who don’t know the compass headings by heart), with the wind speed at 7 knots gusting (that’s the G) to 15 knots. If the winds are above 6 knots and it’s a day with interesting winds, you might see this: 16018KT 140V250, which indicates that the winds are from 160 degrees at 18 knots, but the direction is actually variable between 140 degrees and 250 degrees. For this to show up, the wind has to have a difference of more than 60 degrees in the variation.

10SM means the visibility is ten statute miles. This is generally the highest number you will see. It can go down to 1/4 of a mile visibility.

SCT200 means there are scattered clouds at 20,000 feet. Always add two zeros to get the altitude of the clouds.

04/M06 is the temperature and dewpoint. The dewpoint is the temperature to which the air must be cooled for condensation to form. These temperatures are in Celsius, and the M means minus.

A3012 means the altimeter shows 30.12 inches of mercury for the pressure.

RMK AO2 means that this is the beginning of the remarks section and that the station is automated and has a precipitation sensor. If it’s AO1, it does not have a precipitation sensor.

Now for the fun part. What if something more dramatic is going on? Here are some of the pieces you may see:

Clouds:
Couds are measured in eighths of the sky, or octas.
SKC Sky Clear
FEW 1-2 octas
SCT 3-4 octas
BKN 5-7 octas
OVC 8 octas – this is short for overcast.

means light.
There is no notation for moderate.
+ means heavy.
C is in the vicinity.

Here are some descriptions:
MI Shallow
PR Partial
BC Patches
DR Low Drifting
BL Blowing
SH Shower(s)
TS Thunderstorm
FZ Freezing

Precipitation is listed like this:
DZ Drizzle
RA Rain
SN Snow
SG Snow Grains
IC Ice Crystals
PL Ice Pellets
GR Hail
GS Small Hail and/or Snow Pellets
UP Unknown Precipitation (I always wondered what could be falling out of the sky to get this notation!)

If the air is not clear, you may see these:
BR Mist
FG Fog
FU Smoke
VA Volcanic Ash
DU Widespread Dust
SA Sand
HZ Haze
PY Spray

This is where it gets fun (or I go find a closet to hide in, which works, too):
PO Well-Developed Dust/Sand Whirls
SQ Squalls
FC Funnel Cloud Tornado Waterspout
SS Sandstorm

If you see any of the last four, I sincerely hope you decide not to fly.

I’m a VFR pilot. I don’t fly in clouds or nasty weather, which is just fine with me. I may eventually get my IFR (instrument) rating, but that will mostly be because I like learning new things, not because I like storms.

Now you have some idea how to read a basic aviation weather report, and I’ve remembered a few things I had forgotten. I think that’s positive all around. At some point I’ll get into SIGMETs and AIRMETs, but that’s a post for another day.

Four forces and control surfaces

There are four forces that act on an airplane in flight: life, thrust, drag, and weight/gravity.

I’ve gone over lift, so today I’ll run through the other three and then talk about control surfaces.

Drag is what slows the airplane down. Drag is caused by the airframe hitting the air (wind resistance), by cooling ducts, by things sticking out from the airframe (antennas, for instance), and drag that’s caused by lift (when you are flying with an angle of attack that is not 0, some of the lift force generated goes to the rear, causing drag).

Thrust either pushes or pulls an aircraft through the air. This is done through propellers or jets. Thrust overcomes drag on airplanes. If you are playing with a paper airplane, you throwing it is the thrust.

Weight, or gravity, pulls the airplane down. This is made up of the airplane and whatever you’ve put in or on it.

Silly joke – an Alaskan bush pilot took a tourist on a hunting trip. They bagged a moose and strapped it onto the plane. They took off and the plane struggled and strained and finally ran into a mountain, about 3/4 of the way up. The pilot and passenger landed safely, amazingly enough, and the passenger was not pleased. He became even less pleased when he noticed that the pilot was laughing. “What are you laughing about? We’re stuck in the middle of nowhere and your plane is on top of my moose!” The pilot replied, “No! this is great! Last time I only got halfway up!”

Just a little too much weight.

During take off, thrust must be greater than drag and lift must be greater than weight. If those requirements are not met, the airplane doesn’t take off.

Control surfaces are fun. They’re especially fun once you get into training that deals with how to handle control surface failures and you learn that opening a door can help you control a plane in flight, but that’s probably another post.

There are three directions an airplane can move.

When you are looking at the front of the airplane, roll makes the wings go up and down but the nose stays pointed directly at you. Ailerons control roll, and the stick or yoke controls the ailerons. Ailerons are located on the trailing edge of the wing and are hinged so they go up and down in opposition – when one is up, the other is down.

When you are looking at an airplane from the side, pitch moves the nose up and down. The elevator, located on the trailing edge of the tail. Pushing the yoke or stick forward moves the elevator down and pushes the nose down as well.

When you are looking at an airplane from the top, yaw moves the nose and tail from side to side. The pivot point is basically the cockpit, and the nose and tail circle around that on the horizontal axis. Yaw is controlled by the rudder pedals. If you are making a turn in an airplane, you have to control yaw or the tail slides out. If you have passengers, they are more likely to turn green from yaw than from pretty much anything else. It feels weird, like your rear end is trying to escape from your spine and move off to the side. That’s an overstatement, of course, but it’s the reason “flying by the seat of your pants” starts to make sense when you are in the pilot’s seat. You can feel yaw.

The flaps are the final control surface. I discussed them some in the section on lift. They are most commonly used for takeoff and landing.

That about does it for the very basic parts of control surfaces. I think perhaps I’ll get into weather next time.

How do airplanes fly?

I have a fun one today, which includes an experiment so you can understand a little better.

Take a smallish piece of normal copy paper, not much bigger than 3″x5″. Hold the short end under your lower lip, so you can blow over it but no air will go under it. Blow.

Didn’t expect the paper to move, did you?

Another experiment – hold two pieces of paper up to your face, on either side of your mouth, about 3″ apart. Blow between the pieces of paper. My first thought was that they would push apart, but they don’t. They come together.

How is lift generated? How do airplanes fly? Intuitively, at least for me, they shouldn’t. Airplanes are getting pushed forward, not up. This gave me a headache for a while, but then I started to understand a little more. I didn’t have to do the actual physics equations, either, so those of you who have issues with physics don’t have to worry about hard math.

The problem we face when trying to figure this out is that there are two separate camps, both of which have part of the answer. The actual answer is very complex, so we’ll go through it as simply as possible.

Bernoulli’s equation says that air going over a surface that is curved on top and flat on the bottom will have less pressure on the top because the air is going faster there. The lower pressure provides lift. Things will move towards an area of lower pressure. This kind of lift is dependent on the shape of the wing. Gliders are almost completely dependent on this kind of lift. No engines to push them forward and create relative wind. This kind of lift is also very stable.

Newtonian lift is created when air hits the bottom of a tilted surface (remember the angle of incidence?). The air is deflected downward, which creates the equal and opposite reaction of upward lift on the wing. If you have ever stuck your hand out the window of a moving car and tilted your hand, you have felt the air push your hand up as you deflect it down. This kind of lift doesn’t depend on the shape of the wing. It’s somewhat unstable, which, again, you can find out by sticking your hand out the car window – you’ll feel the adjustments you have to make to keep your hand from going in unexpected directions.

Between these two kinds of lift, you have pretty stable flight.

People have huge arguments over which one of these equations is correct. They both are, in combination. Before powered flight, humans used Bernoulli’s lift pretty much on its own. With powered flight, we can use Newtonian lift to get more lift and Bernoulli to stabilize the flight.

See? No physics equations, and a couple of neat things to try. Not as hard as you thought, was it?

Flying – defining terms

Today I’m going to define some very basic terms for flying. As I work through the Private Pilot test preparation, I’ll be using the terms at times, and if you understand what I’m talking about it will be easier to follow. It also gives me a good review of what I used to remember easily.

First, the airfoil. An airfoil is a structure or body which produces a useful reaction to air movement. This includes airplane wings, rudders, propellers, and helicopter rotor blades. Today we’ll talk about wings on fixed-wing aircraft.

Here is the cross section of a wing:

“A” is the leading edge. That’s the front of the wing. “B” is the trailing edge. The dotted line going through the wing is an imaginary straight line from the leading edge to the trailing edge called the chord line. The chord line does not necessarily go through the wing, depending on the wing’s shape.

If you lower the flaps, the chord line will drop and go from the leading edge to the bottom of the flap.

Before we go any further, I’d like you to wrap your brain around a concept. When we’re talking about the movement of air around an object, the air acts like a fluid. The next term I want to introduce is relative wind. This is the wind felt by an airfoil, but it can be produced by either the airfoil moving or the air moving past the airfoil. Possibly the easiest way to explain that idea is by poking a stick into a stream bed. The water is moving past the stick. That is the relative wind. Even though the stick is not moving, there is a relative wind. Relative wind is parallel and in the opposite direction of the path of the airfoil, so if the wing is pointing up at an angle, the relative wind is going down. Straight and level flight produces wind coming from the front of the airfoil going straight back. If your flight path goes down, the relative wind is upwards.

This explanation is important because it defines one of the very basic terms that will be used when we’re talking about climbing and stalling. The angle of attack is the angle between the chord line of the wing and the relative wind. You can change your angle of attack by changing the control surfaces of the airplane.

The angle of incidence is the angle at which the wing is attached to the rest of the airplane. This doesn’t change.

That’s it for now for the test prep. Next time I write about flying we’ll go through lift and a few explanations of how airplanes fly.

Ice, ice, baby

I was talking to a person on a bus while I was in Washington DC recently. He was from Florida, and he was talking about the storms they’ve been having this winter. He said he completely understood why airplanes couldn’t fly with ice on their wings and tails; it’s because the ice is so heavy that it pulls the plane down.

He was rather surprised to learn that he was wrong.

The weight of the ice can be a problem, especially if you are talking about ice picked up in flight. The main problem, though, and the reason a visual check of the wing may not be enough to keep you out of trouble for your preflight check, is that ice on the wings spoils the airflow. Even bits of ice as small as grains of salt can decrease lift and increase drag. If you’ve planned a flight based on the normal flight capabilities, ice on the wings can cause you to run out of fuel, for instance, or stall at a speed and attitude that is usually safe. Another issue, if you are talking about bigger pieces of ice, is that a piece of ice can come off the wing and hit some other part of the airplane.

The lift generated by the wing is dependent on the shape of the wing. Even tiny changes in the shape can change the airflow. If the air coming off separates from the wing too soon, you don’t get the lift you need. Ice can also form on propellers, limiting the efficiency and increasing the work required from the engine. Some planes have boots on the leading edge of the wings that can be inflated so the ice breaks off. There are also several other options, including bleeding heat off of jets to keep the wings warm enough so they don’t ice up (which I think is really neat).

Checking for ice before you fly is a good start. There is another problem, though, that you need to keep in mind. Moisture in the air can be supercooled. This means that the water can actually be below freezing, but because there is nothing for the water to freeze around, it stays in a liquid state. If you introduce something new, such as the wing of an airplane, the water immediately crystallizes into ice. A pilot flies into a cloud with no ice on the wings and suddenly has a noticeable accumulation of ice. Not a good thing. If you fly VFR (visual flight rules – no cloud flying!) this part of wing icing shouldn’t be an issue, but if you are flying IFR (instrument flight rules) and it’s cold outside, this can cause you pretty serious issues. You can still get wing ice if it’s cold and you aren’t flying through clouds, but it isn’t quite as dramatic.

Wing icing is not something you want to take chances on. If it’s cold out, run your hand over the flight surfaces when you are doing your preflight. You’ll feel ice if it’s there, and you’d rather find out before you take off than realize there’s an issue when you can’t make the turn out of the pattern.