Saturday, February 20, 2010

Hero:

Want to read about a hero? Go read about Tammy Duckworth, a helicopter pilot for the U.S. Army who was shot down in Iraq. Her helicopter was shot down by Iraqi insurgents who fired an RPG at her helo. The RPG exploded on the right side of the helicopter, severing Duckworth's legs and mangling her right arm. Since her recovery from her almost-lethal wounds, she works for the VA system and is learning to fly civilian fixed-wing airplanes in her spare time. What a great story!

Eight Patterns, Eight Landings

A photo I took today at the airport. I call it "Freedom Through the Fence" because I am a dork.

2/20/2010 C-150 N5307Q GIF-GIF
Traffic Patterns and normal landing practice
8 landings 1.5 hours
Grand Total: 21 hours


Today was an awesome day to fly. For starters, the weather was perfect: clear skies, no wind, no clouds, nice mellow temperature. It was without a doubt the most perfect flying day I could have asked for.

Despite this perfect weather, the traffic pattern at the airport was less busy than I had expected. With perfect weather on a Saturday afternoon in Florida, I'd expect tons of traffic aloft, but for the first 45 minutes or so in the air it seemed like it was just me and my instructor. A few planes joined us in the traffic pattern later on in the afternoon, but by and large our company in the air was courteous and not hurried--which is good as our little Cessna 150 has about one horsepower and putts through the traffic pattern at a fairly laid-back pace.

There was some drama on the radio, however. A flight student on a solo had gotten lost and was asking for directions. My instructor suggested he try to use a VOR* signal to triangulate his position, and the student's instructor came on the radio and suggested he try some orienteering, but the student saw some random field and opted to just land the flight and figure out where he was from the ground. Also of note, another aircraft announced that they had experienced engine failure and would be landing on the inactive runway, but fortunately it was just an engine-out drill. No actual emergency--phew!

We spent the day focusing on traffic patterns and on landings. The concept of the day was to grasp was the "Stabilized Approach," which is to say that while approaching for landing the view from the cockpit should be of the runway growing larger but not moving. A lot of pitch or yaw or roll to correct should not be necessary if one's approach is solid. On my first few patterns of the day, my approach was a touch sloppy and the landings were definitely rough. Bryan coached me through the landing: the objective is to float the airplane and not quite let it land until it's niiiiice and easy. There needs to be back pressure on the yoke to prevent the airplane from touching with the nosewheel first. Keeping the pressure on the yoke also prevents the nosewheel from mushing around and making it hard to steer.

Three problems popped up today. First, my instructor noticed that I wasn't paying enough attention to airspeed. This is a huge problem since losing your airspeed while maneuvering near the ground can cause an un-recoverable stall, which can then cause death. I wish to avoid death, and so after my instructor reminded me of the importance of airspeed I worked hard to maintain it. I think I was too throttle-shy at first, but as the day went on I grew more aggressive and learned what sort of maneuvers require additional power. My recent reading on the power curve makes a lot more sense after all that mucking around with the throttle today. I also focused on pitching for airspeed.

Problem two: I had a hard time steering after landing. Ten years of car driving kick in and I try to steer with the ailerons (the yoke) when it is instead necessary to steer with your feet, on the rudder pedals. I tried to focus on fixing that but my brain was full and so I will try to do better next time.

The final problem: when I am making my power and configuration changes at the end of the downwind leg, I have a tendency to steer the airplane to the right. It's not a huge deal, but Bryan mentioned it to me and I feel like I should work on neatening that up. After all, unintentional changes in attitude while changing configuration can become problematic.

After plenty of practice, with eight traffic patterns and seven touch-and-go's, my patterns were tighter, my landings were better, and I felt like I had made some progress and learned a lot. Bryan told me that my landings had gone from not good at all to a C+ grade, and I feel good about that. The objective is an eventual A+, so more practice is in order!

All in all, a productive day. An hour and a half more in the logbook, eight good traffic patterns, and three unassisted landings that went fairly well. In aviation, any landing you can walk away from is a good landing, but any landing that you can walk away from
and still use the plane is a great landing. In that light, I think that today was a great day indeed.

Finally

Finally, I can get back into the air again. It's been a few weeks since I have been in the air, mostly due to my CFI's need for some time off to pursue some professional goals outside aviation. I'll be glad to get back into the air.

Having a few weeks away from the cockpit, though, makes me a little rusty. I have practiced some basics with my flight sim here at the house, though that it not the same as actual time in the left seat. I have also spent a lot of time reading up on the ground school portion of my training, which I feel has been helpful. I've focused a lot on the relationships between power and drag, and on the power curve, which I feel gives me a better understanding of how to maneuver the airplane.

Today, my instructor wants to focus some more on the traffic pattern, and then possibly let me shoot a landing. I have been "afraid of the controls," by which my instructor means I have been a little reluctant to totally take control, but last time we flew I worked on that and I will make a conscious effort to be more assertive behind the wheel. Without being willing to work the controls, making a landing is impossible, and without landing, soloing is impossible, and without a solo flight, the private pilot's license is unattainable; therefore it is important that I learn to take control more effectively and learn how to land.

Off to the airport for a 2:30 flight. More when I return.

Friday, February 12, 2010

More Aeroydnamics!

As part of my continuing study of the ground school materials for my private pilot's license, I have been reading through two separate references. The primary is the ASA textbook for private pilot ground school; the secondary is "The Proficient Pilot" by Barry Schiff.

I have not gotten too far into the text. My last series of notes on aerodynamics is continued here, mostly to reinforce it in my own head but also for your reading if you're into this sort of thing.


Continuing on the concept of drag, it is important to understand that parasite and induced drag will vary in their proportional influence depending in your airspeed. As you accelerate to higher airspeed, parasite drag increases exponentially; a doubling of airspeed quadruples parasite drag. Induced drag, on the other hand, is a result of lift development and varies with angle of attack. At slower airspeeds induced drag becomes a major concern.

This talk of induced versus parasite drag brings us to the concept of the region of reversed command. The term "reversed command" refers to the phenomenon that occurs wherein more power is required to maintain less airspeed. Barry Schiff uses the example of a pilot approaching a mountain airstrip: as the pilot approaches the strip, he notices that he is a little low on altitude, and so he raises the nose to climb. Unfortunately for the pilot, rather than climbing, his airplane slows down and sinks. The pilot reflexively raises the nose again and adds power, but it is too little too late, and he smashes to earth, banging his airplane up and wondering what the deuce happened.

What happened was: the pilot was in the region of reversed command. Flying low and slow, he made the error of pitching up without adding power, which caused him to slow down and fall from the sky, not to climb as he expected. In slow flight, approaches, or other maneuvers requiring lowered airspeed, it is necessary to add power to stay aloft even though your airspeed is lower. Not what you might think at first, but it's important to understand the concept.

The practical upshot of all this: control your altitude with power, your airspeed with pitch. Pitching to altitude will cause you to enter mushing flight and lose the altitude you seek to gain. Especially in low and slow flying, remember this concept.


Continuing on, we come to control and control surfaces. Control surfaces are important because they enable you to, well, control the airplane. A plane is controlled along three different axes:
  • The LATERAL or PITCH axis, which extends from wingtip to wingtip and is controlled with the ELEVATOR;
  • The LONGITUDINAL or ROLL axis, which extends from nose to tail and is controlled by the AILERONS; and
  • The VERTICAL or YAW axis, which extends from the central floor to ceiling of the aircraft and is controlled by the RUDDER.




Control surfaces work by redirecting airflow in a specific manner. When the plane is controlled on the ROLL axis by the AILERON, it will enter a bank attitude with one wing higher and one wing lower than the other. When the RUDDER is activated, airflow is directed around it and the plane YAWS. And when the ELEVATOR is used, airflow will push or pull the tail and PITCH the airplane one way or another.

Pitch control:

Pitch control is achieved by using the elevator, which is the movable control at the backside of the horizontal stabilizer. Control around the Lateral (pitch) axis is also achieved to some extent with the throttle. Increasing the throttle in a low-tailed prop plane will "blow the tail down" by blasting air back and over the top surface of the elevator. A reduction in power will also reduce the pressure on the elevator, which will pitch the nose down. This effect of the propellor on the elevator helps the plane to maintain a stable angle of attack and thereby maintain a stable airspeed.


Roll control:
Roll is controlled by ailerons, which are located on the outer trailing edge of the wing. When the ailerons are deflected, the airplane will "roll" by banking. When one aileron is lowered, the camber and the angle of attack increase the lift of that wing and raise it. At the same time, the aileron on the opposite side is raised, the change in camber and angle of attack will lower the lift of that wing and sink it.

Also contributing to bank and turn is adverse aileron drag. This occurs when the wing of the down aileron is dragged backwards, slowing the turn. Adverse aileron drag is compensated for by the rudder, though some aircraft are designed to overcome this imbalance by equalizing aileron drag.

Yaw control:
The rudder is a movable surface attached to the back of the tailfin that is used for yaw control. Like the ailerons, it alters camber and angle of attack on the tailfin, varying the forces on either side of the tail. It is used to offset forces moving the nose of the aircraft from side to side, such as P-forces from the turning propeller.

Since the rudder is located at the far back of the airplane, there is a long lever arm between the rudder and the nose. Small rudder inputs often translate to large movements of the nose. Some planes have shorter tails or a shorter "lever arm" and require greater rudder input. These planes are known as "short coupled" aircraft.

That's about it for control axes. Next up: control and stability!

Wednesday, February 10, 2010

I Win!

Last night, I drove from my home in central Florida over to Tampa for a free safety seminar hosted by the AOPA Air Safety Foundation. Safety is number one when aviating, and as a student pilot especially I feel it is my duty to learn as much as I can about safe flying.

I have been to one other ASF seminar in the past; in November or December I went to a seminar entitled "What went wrong?" which focused on the causes of fatal accidents*. The seminar hosted in Tampa last night was entitled "10 Things Other Pilots Do Wrong," and it focused on the unsafe or annoying habits of other flyers that can affect your safety and the public's perception of General Aviation.

I arrived at the seminar at about 7, turned my registration card in at the door (registration is free--no excuse not to go!), and found a seat just in time to see the beginnings of the seminar. I relaxed, sat back, and absorbed the knowledge as best I could.

Halfway through the seminar, we took a ten-minute break. As we left the speaker reminded us that there would be door prizes given away, five DVDs, three copies of 2010 FAR/AIM, and one GPS locator thingy. As I stretched my legs I thought to myself, "I bet I could win a prize tonight. I'm feeling lucky. Maybe I'll get me a copy of the FARs..."

We returned to our seats, and the speaker drew names. Five gentlemen before me won the DVD, and two copies of the FAR/AIM were passed out. The speaker drew a card from the box, looked for a second, and then spoke my name.



"Hoi!" I surprised myself by jumping up from the seat and waving at the guy passing out the prizes. What excitement! A copy of the Federal Aviation Regulations and Airmans Information Manual for 2010, all mine, for free! I hardly ever win anything, so I was very excited.

I know that not many normal people would be excited by a copy of the legislation that permits their hobby to exist, but dang it, I'm not that normal to begin with. Reading the FARs is maybe a little dry, but knowing what you're permitted to do is vital in this modern age, and the Airman's Information Manual has a lot of great material inside it.

I, for one, am thrilled with my new gift and am grateful to the ASF for handing it over to me.

*Hint: the human factor is the common denominator. Pilots who choose to fly in unsafe conditions, pilots who let themselves run out of options, and pilots who push themselves beyond the limits of what they can safely do in the cockpit tend to be involved in fatal accidents. Humility and a firm grasp on your own limitations is key in aviation.

Friday, February 5, 2010

Moths

Apparently, Moths can use some sort of ingrained sense not only to navigate, but to detect and take advantage of wind currents. According to this article from NPR, not only can these tiny little marvels navigate using some kind of internal compass, but they can also detect wind speed and direction and use that information to select the altitude with the most favorable winds.

Amazingly sophisticated, for such a small animal. Makes me feel a little sad that the cats will occasionally eat one of these little silken marvels.

Wednesday, February 3, 2010

Aerodynamics!

Time for aerodynamics! I bought the ASA Complete Private Pilot, and so I have been making an effort to crack the books and learn the principles of flight. I've got several other supplements, but since the ASA book is reportedly the test prep for the FAA knowledge exam, I've been reading it and taking notes. It's very good and I recommend it to any student pilots out there. That plus Rod Machado's guide should get you ready.

I'm on aerodynamics, which is all wings and lift and Center-of-Gravity and drag. Very important information to know--it's good to understand the unseen hand of lift that will guide you as you fly, because it can reach out and swat you from the sky if you misuse it.

So, to reinforce it in my own head, here are some of the terms and concepts I have been trying to grasp:

Camber: The curvature of the upper surface of a wing.

Angle of Incidence: The angle at which the wing is fastened to the fuselage of the aircraft--usually the Angle of Incidence is one to three degrees.

Downwash: Airflow that is "washing off" the trailing edge of the wing. Related to Newtonian lift, in that "each action must have an equal and opposite reaction."

Chord Line: An imaginary line drawn from the leading edge of the wing to the trailing edge of the wing.

Relative Wind: The wind relative to the flight path. Typically opposite and parallel the flight track. If you are stationary and the wind is blowing from 020 degrees, that is the wind; if you are on a bicycle moving north at 20 knots the relative wind is south 20 knots.

Angle of Attack:
The angle between the chord line and the relative wind.

Mushing Flight: An attempt to maintain altitude with angle of attack alone and no power. Leads to a nose-up attitude with a loss in altitude. STALL IMMINENT IN MUSHING FLIGHT.

In addition to these concepts, I am trying to master the relationship between velocity and lift. According to the text, when you double your airspeed, you quadruple your lift. However when you halve your airspeed, you quarter your lift. The practical upshot of all this is that staying aloft requires speed. Don't slow down lest the ground rise up to befriend you.

Lift is also balanced by drag, which is broken into "parasite drag" and "induced drag." Parasite drag is from protuberances off the airframe (landing gear, antennae, etc.) Parasite drag will quadruple if you double your airspeed, which is the practical limiting factor in attaining high speeds.

Induced drag is a result of the meeting of high and low pressure air off the wing. Rotational forces as air spirals off the wingtips can also cause induced drag, and changes in the angle of attack will increase or decrease induced drag.

Fascinating stuff, no? These concepts are the building blocks of flying. Not as glamorous as slamming throttles and doing loop-de-loops, but by gum it's important to know the principles of flight.