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CFI Brief: Solo Flight

In Monday’s post we were introduced to the student pilot’s first solo flight. Today, we will take a look a little more in depth to understand exactly what the instructor needs to do to prepare his or her student for solo flight. As a student, this will give you a behind the scenes look at the regulations in which a CFI needs to follow to prepare you the student for solo flight.

A student pilot may not operate an aircraft in solo flight unless the student pilot’s logbook has been endorsed for the specific make and model aircraft to be flown, and unless within the preceding 90 days his/her pilot logbook has been endorsed by an authorized flight instructor who has provided instruction in the make and model of aircraft in which the solo flight is made, and who finds that the applicant is competent to make a safe solo flight in that aircraft.

Prior to being authorized to conduct a solo flight, a student pilot must have received and logged instruction in the applicable maneuvers and procedures for the make and model of aircraft to be flown in solo flight, and must have demonstrated proficiency to an acceptable performance level as judged by the instructor who endorses the student’s pilot certificate. As appropriate to the aircraft to be flown in solo flight, the student pilot must have received presolo flight training in:

  1. Flight preparation procedures, including preflight inspections, powerplant operation, and aircraft systems.
  2. Taxiing or surface operations, including runups.
  3. Takeoffs and landings, including normal and crosswind.
  4. Straight-and-level flight and turns in both directions.
  5. Climbs and climbing turns.
  6. Airport traffic patterns, including entry and departure procedure, and collision, wind shear, and wake turbulence avoidance.
  7. Descents with and without turns, using high and low drag configurations.
  8. Flight at various airspeeds from cruise to slow flight.
  9. Stall entries from various flight attitudes and power combinations with recovery initiated at the first indication of a stall, and recovery from a full stall.
  10. Emergency procedures and equipment malfunctions.
  11. Ground reference maneuvers.
  12. Approaches to a landing area with simulated engine malfunctions.
  13. Slips to a landing.
  14. Go-arounds.

A student pilot may not operate an aircraft in a solo cross-country flight, nor may he/she, except in an emergency, make a solo flight landing at any point other than the airport of takeoff, until he/she meets the requirements prescribed in Part 61. However, an authorized flight instructor may allow a student to practice solo takeoffs and landings at another airport within 25 NM from the airport at which the student receives instruction, if the instructor finds the student competent to make those landings and takeoffs, and the flight training specific to the destination airport (including the route to and from, takeoffs and landings, and traffic pattern entry and exit) has taken place. Also, the instructor must have flown with that student prior to authorizing those takeoffs and landings, and endorsed the student pilot’s logbook accordingly.

The term cross-country flight means a flight beyond a radius of 25 nautical miles from the point of takeoff. A flight instructor must endorse a student pilot’s logbook for solo cross-country flights. There are three types of these endorsements:

  1. An endorsement in the student pilot’s logbook that the instructor has reviewed the preflight planning and preparation for each solo cross-country flight, and the pilot is prepared to make the flight safely under the known circumstances and the conditions listed by the instructor in the logbook.
  2. The instructor may also endorse the logbook for repeated solo cross-country flights under stipulated conditions over a course of not more than 50 nautical miles from the point of departure if he/she has given the student flight instruction in both directions over the route, including takeoffs and landings at the airports to be used.
  3. The student pilot certificate must be endorsed for cross-country operations.

Hopefully the information above gives you a general idea of what needs to be accomplished prior to your instructor allowing you to conduct solo flight, whether it be your first solo in the traffic pattern or a more extensive solo cross country flight to the next town over.

CT-SOLO-PD_HiRes

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Regulations: First Solo Flight

You are able to fly solo when the instructor believes, with some confidence, that you can fly safely with a degree of consistency and you have mastered the presolo maneuvers defined in the regulations. Most important is evidence that you are taking control and responsibility for your own actions—that you are walking on your own two feet. Today’s post comes from the new fifth edition of The Pilot’s Manual: Flight School (PM-1C).

The instructor is looking to see you make corrections for inaccuracies without waiting to be told and without asking for instructions, responding to radio calls without question and saying what you intend to do rather than asking what is next. These are the signs of aviation maturity, of being in command. They are no different from other life skills, just applied at a higher altitude.

First solo is an unforgettable experience that you will remember and treasure all your life. When your instructor tells you to stop after turning off the runway, steps out of the airplane, secures the harness and then leaves you to your first solo flight, you are being paid a big compliment. Your instructor is confident that you can safely complete a solo traffic pattern. You have demonstrated sufficient awareness, skill and consistency to be trusted to take the aircraft up by yourself.

You may feel a little apprehensive (or very confident), but remember that the instructor is trained to judge the right moment to send you solo. Your instructor has a better appreciation of your flying ability than anybody (including you—especially you).

Your instructor will have observed your progress and have assessed your consistency, safety and predictability. It is not the occasional brilliant landing that is looked for, but a series of consistently safe ones. Your instructor will choose the conditions and the traffic so that they are not more demanding than you are used to.

You know instinctively when you are ready to fly solo. In some cases, you may feel you are ready before time. Your instructor knows when the time is right. Trust in that.

Your instructor will also advise the control tower that this is a first solo and the controller will keep a watchful eye open for this new fledgling. The controller will anticipate wind changes and try not to change the active runway while you are flying your first solo traffic pattern.

Presolo Written Exam
Before going solo, you must have passed a written examination administered and graded by the flight instructor who endorses your logbook for solo flight. The written examination will include questions on the applicable Federal Aviation Regulations, and the flight characteristics and operational limits of your airplane. By answering the review questions of each exercise during your training, you will be well prepared for the questions on the flight characteristics and operational limits of your airplane.

These next review questions prepare you for the regulations questions. They direct you into your current copy of the regulations to indicate the level of knowledge you require prior to going solo. Since regulation numbering changes from time to time, the part has been identified—for example, Part 91 and Part 61—but not the individual section, which you can easily find using the table of contents page in your book of regulations.

Application
Fly your first solo traffic pattern in the same manner as you flew the pattern before the instructor stepped out. The usual standards apply to the takeoff, pattern and landing. Follow exactly the same pattern and procedures. Maintain a good lookout, fly a neat pattern, establish a stabilized approach and carry out a normal landing. Be prepared for better performance of the airplane without the weight of your instructor on board. If at any stage you feel uncomfortable, go around. Many students comment on how much better the airplane flies without an instructor and how much quieter it is!

Be in control. Do not be blown with the wind. The tower will try to avoid any interruptions or runway changes while you are airborne but, if there is a need for you to hold overhead the field or to change runway, then take your time, think through the best plan of action, ask for instructions if you are in doubt and then complete a normal pattern and landing.

If an emergency occurs, such as engine failure (and this is an extremely unlikely event), carry out the appropriate emergency procedure that you have been taught. If your radio fails simply complete the pattern and land normally. Be aware of other traffic. You have been taught to go around and it may happen even on your first solo. Simply complete another pattern.

Your flight instructor, when sending you solo, not only considers you competent to fly a pattern with a normal takeoff and landing, but also considers you competent to handle an abnormal situation. One takeoff, one pattern and one landing are the rites of passage to the international community of pilots.
firstsolo

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CFI Brief: Flight Controls of a typical Commercial Airliner

This week on the Learn to Fly Blog the theme has been aerodynamics, and rather than stick to Private Pilot level aeronautical information we’ve hit you with some “graduate level” knowledge. Today, I thought it would be interesting to take a look at the primary flight controls of a typical commercial airliner. Looking at the image below you’ll notice right off the bat that while there’s a few more controls it’s not all that different than the training aircraft you might be flying in today.

One of the biggest differences to point out revolves around the way the flight controls are moved. Because of the high air loads, it is very difficult to move the flight control surfaces of jet aircraft with just mechanical and aerodynamic forces. So flight controls are usually moved by hydraulic actuators. Flight controls are divided into primary flight controls and secondary (or auxiliary) flight controls. The primary flight controls are those that maneuver the aircraft in roll, pitch, and yaw. These include the ailerons, elevator, and rudder. Secondary (or auxiliary) flight controls include tabs, trailing-edge flaps, leading-edge flaps, spoilers, and slats.

ATP-03-05

Roll control of most jet aircraft is accomplished by ailerons and flight spoilers. The exact mix of controls is determined by the aircraft’s flight regime. In low speed flight, all control surfaces operate to provide the desired roll control. As the aircraft moves into higher speed operations, control surface movement is reduced to provide approximately the same roll response to a given input through a wide range of speeds.

Many aircraft have two sets of ailerons—inboard and outboard. The inboard ailerons operate in all flight regimes. The outboard ailerons work only when the wing flaps are extended and are automatically locked out when flaps are retracted. This allows good roll response in low speed flight with the flaps extended and prevents excessive roll and wing bending at high speeds when the flaps are retracted.

Spoilers increase drag and reduce lift on the wing. If raised on only one wing, they aid roll control by causing that wing to drop. If the spoilers rise symmetrically in flight, the aircraft can either be slowed in level flight or can descend rapidly without an increase in airspeed. When the spoilers rise on the ground at high speeds, they destroy the wing’s lift which puts more of the aircraft’s weight on its wheels which in turn makes the brakes more effective.

Often aircraft have both flight and ground spoilers. The flight spoilers are available both in flight and on the ground. However, the ground spoilers can only be raised when the weight of the aircraft is on the landing gear. When the spoilers deploy on the ground, they decrease lift and make the brakes more effective. In flight, a ground-sensing switch on the landing gear prevents deployment of the ground spoilers.

Vortex generators are small (an inch or so high) aerodynamic surfaces located in different places on different airplanes. They prevent undesirable airflow separation from the surface by mixing the boundary airflow with the high energy airflow just above the surface. When located on the upper surface of a wing, the vortex generators prevent shock-induced separation from the wing as the aircraft approaches its critical Mach number. This increases aileron effectiveness at high speeds.

As you progress through the ranks of aviation and begin flying larger aircraft you will start noticing some of these secondary flight controls installed on your aircraft. But many of the training aircraft like the Cessna 172’s, Piper Archers, or piston powered aircraft you might be flying today won’t have secondary controls such as spoilers installed. The majority of the time these aircraft are just not large enough, heavy enough or fast enough that spoilers would be an effective or beneficial flight control. It is however beneficial to gain experience in the knowledge of these flight control systems as it will help you later on in training when you merge your private and professional aerodynamics lessons into practice.

For more advanced information on aerodynamics check out our collegiate level textbook, Aerodynamics for Aviators, 2nd Edition.

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Aerodynamics: High Speed Flight

Today’s post comes from the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B).

In subsonic aerodynamics, the theory of lift is based upon the forces generated on a body and a moving gas (air) in which it is immersed. At speeds of approximately 260 knots or less, air can be considered incompressible in that, at a fixed altitude, its density remains nearly constant while its pressure varies. Under this assumption, air acts the same as water and is classified as a fluid. Subsonic aerodynamic theory also assumes the effects of viscosity (the property of a fluid that tends to prevent motion of one part of the fluid with respect to another) are negligible and classifies air as an ideal fluid conforming to the principles of ideal-fluid aerodynamics such as continuity, Bernoulli’s principle, and circulation.

In reality, air is compressible and viscous. While the effects of these properties are negligible at low speeds, compressibility effects in particular become increasingly important as speed increases. Compressibility (and to a lesser extent viscosity) is of paramount importance at speeds approaching the speed of sound. In these speed ranges, compressibility causes a change in the density of the air around an aircraft.

During flight, a wing produces lift by accelerating the airflow over the upper surface. This accelerated air can, and does, reach sonic speeds even though the aircraft itself may be flying subsonic. At some extreme angles of attack (AOA), in some aircraft, the speed of the air over the top surface of the wing may be double the aircraft’s speed. It is therefore entirely possible to have both supersonic and subsonic airflow on an aircraft at the same time. When flow velocities reach sonic speeds at some location on an aircraft (such as the area of maximum camber on the wing), further acceleration results in the onset of compressibility effects, such as shock wave formation, drag increase, buffeting, stability, and control difficulties. Subsonic flow principles are invalid at all speeds above this point.
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The speed of sound varies with temperature. Under standard temperature conditions of 15 °C, the speed of sound at sea level is 661 knots. At 40,000 feet, where the temperature is –55 °C, the speed of sound decreases to 574 knots. In high speed flight and/or high-altitude flight, the measurement of speed is expressed in terms of a “Mach number”—the ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions. An aircraft traveling at the speed of sound is traveling at Mach 1.0. Aircraft speed regimes are defined approximately as follows:

  • Subsonic—Mach numbers below 0.75
  • Transonic—Mach numbers from 0.75 to 1.20
  • Supersonic—Mach numbers from 1.20 to 5.00
  • Hypersonic—Mach numbers above 5.00

While flights in the transonic and supersonic ranges are common occurrences for military aircraft, civilian jet aircraft normally operate in a cruise speed range of Mach 0.7 to Mach 0.90.

The speed of an aircraft in which airflow over any part of the aircraft or structure under consideration first reaches (but does not exceed) Mach 1.0 is termed “critical Mach number” or “Mach Crit.” Thus, critical Mach number is the boundary between subsonic and transonic flight and is largely dependent on the wing and airfoil design. Critical Mach number is an important point in transonic flight. When shock waves form on the aircraft, airflow separation followed by buffet and aircraft control difficulties can occur. Shock waves, buffet, and airflow separation take place above critical Mach number. A jet aircraft typically is most efficient when cruising at or near its critical Mach number. At speeds 5–10 percent above the critical Mach number, compressibility effects begin. Drag begins to rise sharply. Associated with the “drag rise” are buffet, trim, and stability changes and a decrease in control surface effectiveness. This is the point of “drag divergence.”

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VMO/MMO is defined as the maximum operating limit speed. VMO is expressed in knots calibrated airspeed (KCAS), while MMO is expressed in Mach number. The VMO limit is usually associated with operations at lower altitudes and deals with structural loads and flutter. The MMO limit is associated with operations at higher altitudes and is usually more concerned with compressibility effects and flutter. At lower altitudes, structural loads and flutter are of concern; at higher altitudes, compressibility effects and flutter are of concern.

Adherence to these speeds prevents structural problems due to dynamic pressure or flutter, degradation in aircraft control response due to compressibility effects (e.g., Mach Tuck, aileron reversal, or buzz), and separated airflow due to shock waves resulting in loss of lift or vibration and buffet. Any of these phenomena could prevent the pilot from being able to adequately control the aircraft.

For example, an early civilian jet aircraft had a VMO limit of 306 KCAS up to approximately FL 310 (on a standard day). At this altitude (FL 310), an MMO of 0.82 was approximately equal to 306 KCAS. Above this altitude, an MMO of 0.82 always equaled a KCAS less than 306 KCAS and, thus, became the operating limit as you could not reach the VMO limit without first reaching the MMO limit. For example, at FL 380, an MMO of 0.82 is equal to 261 KCAS.

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CFI Brief: ATC Tower Light Gun Signals

A while back I was on a local area pleasure flight with a couple of friends showing off the sights in the club’s Piper Cherokee. I was so wrapped up in making sure my passengers were having a good time that I failed to immediately notice the illuminated low voltage light. By the time I did notice, my alternator had already completely failed and I was working with about 20 minutes of remaining battery. Lucky for me at the time I was operating on a VFR flight plan in uncontrolled airspace on a beautiful sunny day. The failure in itself did not present any sort of emergency situation but I knew I would soon lose all electrical power, including my radios and would be unable to communicate with air traffic control (ATC).

My home airport was about a 25 minute flight away and located in Class D airspace, meaning in a normal situation I would need to establish two-way radio communication prior to entering into the airspace and further clearance to land from the control tower. However, I knew with every click of the radio I would be draining the battery of precious power and more than likely have no battery left by the time I got near the airport. After running through the checklists and reducing the electrical load by switching off all non-essential equipment, I tuned in the control tower frequency for the class D airport. My goal at this point was to make a quick radio call to the tower advising them of my impending communications failure, intentions, and current position. Unfortunately for me I was in a bit of a mountainous area and still a little too far out that I was not able to hear any response back from the tower, so I was unsure if they had received my transmission or not. This still was not that big of a concern for me since I knew there were communication procedures in place for situations just like this one.

Light Gun

In the event of a radio communications failure, ATC towers have set procedures to communicate with aircraft via light gun signals. Every operating control tower is outfitted with hand held light guns like the one pictured that emit, Red, Green, and White Light.

After my failure to establish radio communication with the tower, I dialed 7600 into the transponder, which is the squawk code for communications failure. Keeping in mind that when my battery finally did die, my transponder would as well, the squawk code would disappear from ATC radar, and I would just appear as a blip on the screen. About 10 miles out from the airport I went to call tower again and sure enough lost battery power mid transmission. I was close enough to the airport now that I figured someone in the tower probably saw my 7600 squawk and knew I had a communications failure, but I still needed to be extremely cautious and aware of other traffic in the airspace and traffic pattern. I bee-lined it directly for the airport at an altitude of 2,500 ft MSL which was about 1,000 ft above traffic pattern altitude (TPA). My goal here was to overfly the airport looking for other aircraft in the traffic pattern so I could safely descend to TPA and enter into the pattern. Upon overflying the airport I noticed a bright green light emitting from the control tower window. Now remember those aforementioned light gun signals a paragraph earlier? The steady green light is visual communication for cleared to land. Tower must have either noticed my squawk code or put two and two together that some random aircraft was in their airspace without prior clearance and is one, either an idiot or two, more than likely has a communication failure. Without further incident I was able to safely land, receiving another steady green light while on final approach. Once taxing clear of the runway I looked back behind me at the tower and received a flashing green light which is the visual light cue for cleared to taxi.

There is a whole set of Airport Traffic Control Tower Light Gun Signals that you should become familiar with and know by memory. You can find all of these signals and procedures outlined in the AIM Section 4-3-13. I have also included a visual image for each of the light gun signals below.

Light Gun Signals

After parking and securing the aircraft I gave tower a quick phone call to make sure everything was good. They gave me the A-OK and said they had received the first transmission I made when still 30 miles out, so they had been expecting my arrival and tracked my 7600 squawk code up until I lost power. All in all everything worked out fine that day, other than our scenic flight being cut a bit short—but oh well, saved me a few bucks on the rental fee.

Light gun signals are something that you should know by memory; radio communication failures are not as rare as you might think they are. I have had two in my 15 years of flying. The second of which was a similar circumstance to the first, however that time ATC tower was not exactly on their A-game. After overflying the airport for about 5 minutes and entering the traffic pattern I never received any sort of visual light signal from the tower. I ended up landing, taxing, and parking without ever getting any clearance. I was starting to think their light gun was broken. After I parked and secured the aircraft, I called tower to see what was up. Turns out it was a slow day at the airport and no one in the tower ever even noticed me in the pattern or landing for that matter! I taxied to parking none-the-wiser to the controller’s. It’s not really advisable to land without clearance but sometimes everything doesn’t work out the way it should and you must adapt to the circumstances you are dealt with.

You have the light gun signals memorized yet? Time to find out!

1. A steady red light from the tower, for an aircraft on the ground indicates
A—Give way to other aircraft and continue circling.
B—Stop.
C—Taxi clear of the runway in use.

2. A flashing white light signal from the control tower to a taxiing aircraft is an indication to
A—taxi at a faster speed.
B—taxi only on taxiways and not cross runways.
C—return to the starting point on the airport

3. An alternating red and green light signal directed from the control tower to an aircraft in flight is a signal to
A—hold position.
B—exercise extreme caution.
C—not land; the airport is unsafe.

Answers posted in the comments section.

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Procedures and Airport Operations: The Go-Around

Today we’re excited to announce a new fifth edition of our foundational textbook The Pilot’s Manual: Flight School (PM-1C). Flight School breaks down all the tasks required for Private and Commercial certification. Each chapter outlines the objective, consideration, application, technique, and airmanship of a maneuver as well as a visual explanation of the task and all of its steps. Today, we’ll share the PM-1C’s chapter on the go-around.

Objectives

Raise the flaps in stages.

Raise the flaps in stages.

To describe:

  • the circumstances under which a go-around may be safer than a continued landing; and
  • the technique to transition from a powered approach with flaps (and landing gear) extended to a positive climb with flaps (and landing gear) retracted.

Considerations
Why Go Around?
It may be necessary to perform a go-around for various reasons:

  • the runway is occupied by an airplane, a vehicle or animals;
  • you are too close behind an airplane on final approach that will not have cleared the runway in time for you to land;
  • the conditions are too severe for your experience (turbulence, wind shear, heavy rain, excessive crosswind, etc.);
  • your approach is unstable (in terms of airspeed or flight path);
  • you are not aligned with the centerline or directional control is a problem;
  • the airspeed is far too high or too low;
  • you are too high at the runway threshold to touch down safely and stop comfortably within the confines of the runway;
  • you are not mentally or physically at ease; and
  • a mishandled landing (balloon or bounce).
Going around.

Going around.

Effect of Flaps
Full flap causes a significant increase in drag. This has advantages in the approach to land: it allows a steeper descent path, the approach speed can be lower and the pilot has a better forward view. Full flap has no advantages in a climb: in fact establishing a reasonable rate of climb may not be possible with full flap extended. For this reason, when attempting to enter a climb from a flapped descent, consideration should be given to raising the flap. It should be raised in stages to allow a gradual increase in airspeed as the climb is established.

Application
Establish a Descent for a Practice Go-Around
Follow the usual descent procedures and lower an appropriate stage of flap. Initially, it may be desirable to practice the go-around maneuver with only an early stage of flap extended (or perhaps none at all), as would be the case early in the approach to land. A go-around with full flap requires more attention because of the airplane’s poorer climb performance and generally more pronounced pitching moment as the power is applied and flaps retracted.

Technique
Initiating a Go-Around
A successful go-around requires that a positive decision be made and positive action taken. A sign of a good pilot is a decision to go around when the situation demands it, the maneuver being executed in a firm, but smooth manner. The procedure to use is similar to that already practiced when entering a climb from a flapless descent: power, attitude, trim (PAT). The additional consideration is flap, which is raised when the descent is stopped and the climb (or level flight) is initiated.

To initiate a go-around, move the carburetor heat to cold and smoothly apply full power (counting 1-2-3 fairly quickly is about the correct timing to achieve full power). Be prepared for a strong pitch-up and yawing tendency as the power is applied. Hold the nose in the desired climb attitude for the flap that is set, balance and then trim. The initial pressure and retrimming may be quite significant, especially with full flap.

Full flap creates a lot of drag and only marginal climb performance may be possible. In this case level flight might be necessary while the flap setting is initially reduced. If only partial flap is extended, a reasonable climb can be entered without delay.

The go-around.

The go-around.

As the airplane accelerates to an appropriate speed, raise the flap in stages and adjust the pitch attitude to achieve the desired speeds and climb performance. Trim as required.

Airmanship
Make a positive decision to go-around, then perform it decisively. Exert firm, positive and smooth control over the airplane. Firm pressure must be held on the control column and rudder pedals when the power is applied. Correct trimming will assist you greatly. Ensure that a safe airspeed is achieved before each stage of flap is raised. Once established comfortably in the climb-out, advise the air traffic service unit (and the other aircraft in the traffic pattern) by radio that you are going around.

It is usual, once established in the go-around, to move slightly to one side of the runway so that you have a view of airplanes that may be operating off the runway and beneath you. The dead side, away from the pattern direction, is preferred. However, stay on the centerline if there are parallel runways.

Following the go-around, delay turning onto crosswind leg until at least at the upwind end of the runway to avoid conflicting with other traffic in the pattern.
goaroundtask

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CFI Brief: Don’t Be Afraid of the Dark!

One of my favorite times to fly is during the night or in the wee hours of the morning while it’s still dark. Ever since my first night cross-country flight, I have enjoyed being in the skies when most people are at home sound asleep. Often, flying during these nighttime hours can be a much more peaceful experience; radio frequencies are quieter, air traffic is less, winds and turbulence have settled down a bit, and it’s just you and the open sky. That’s not to say night flying doesn’t come without it’s inherit risks, sometimes more so then flying during daylight hours. One of the greatest differences or associated risks that results from flying under the moonlight is your vision.

Night vision is the ability of the human eye to detect objects at night. The rods and cones that make up the retina of your eye are the receptors which record the image and transmit it through the optic nerve to your brain for interpretation. The cones are concentrated toward the center of your field of vision and are responsible for all color vision and detecting fine detail. Your rods on the other hand are more suited for detecting movement and providing vision in dim light. Unlike cones though, rods are concentrated further away from your center of vision. One downside to rods is the fact they are very light sensitive; any amount of light can overwhelm them and they will need to go through a reset process to adapt to dark. I’m sure this is something you have noticed before. For example when high beam headlights from a car hit you while driving on a dark road you will essentially feel blinded until your rods are able to adjust back to the dim light. It can take the rods up to 30 minutes to fully adjust.

The rods and cones are capable of functioning in both daylight and moonlight, although the process of night vision is placed almost entirely on the rods. It is because of the rods being almost 10,000 times more sensitive to light which makes them the primary receptors for night vision. Since we discussed the cones being concentrated near the fovea (or center of your eye) and rods being concentrated further off center from the fovea it is important to note that the majority of your night vision will be through off-center viewing. Darkness will result in a night blind spot toward the center of your eye where the bulk of those cones are. Rather than trying to look straight on at an object like a plane in the night sky, the pilot is better off looking 5° to 10° off-center exposing the rods to that object as shown in the below image.

Night Blind Spot

The best technique for night scanning is to scan from left to right (or vice versa) starting at the furthest point the eye can see and move inward toward the airplane. While scanning, you will want to spend about 2 or 3 seconds looking at approximately 30° wide sections of the sky, overlapping each section by 10° as you move to the next. This is depicted in the image below.

Night Scanning

 

One of the most important things you must do during night flying is to protect your night vision. Stay away from bright white lights and keep your eyes adapted to the darkness. Chapter 17 of the Pilot’s Handbook of Aeronautical Knowledge (FAA-8083-25B) outlines several ways and steps in which you can protect your night vision. If you plan on flying at night it is a must that you fully understand how your eyes function and differ during moonlight then during daylight. This will help to mitigate those inherent risks associated with night flying.

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Human Factors: Night Vision Adaptation

Flying at night? Several things can be done to help with the dark adaptation process and to keep a pilot’s eyes adapted to darkness. Some of the steps pilots and flight crews can take to protect their night vision are described in this excerpt from the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25B).

Sunglasses
If a night flight is scheduled, pilots and crew members should wear neutral density (N-15) sunglasses or equivalent filter lenses when exposed to bright sunlight. This precaution increases the rate of dark adaptation at night and improves night visual sensitivity.

Oxygen Supply
Unaided night vision depends on optimum function and sensitivity of the rods of the retina. Lack of oxygen to the rods (hypoxia) significantly reduces their sensitivity. Sharp clear vision (with the best being equal to 20–20 vision) requires significant oxygen especially at night. Without supplemental oxygen, an individual’s night vision declines measurably at pressure altitudes above 4,000 feet. As altitude increases, the available oxygen decreases, degrading night vision. Compounding the problem is fatigue, which minimizes physiological well being. Adding fatigue to high altitude exposure is a recipe for disaster. In fact, if flying at night at an altitude of 12,000 feet, the pilot may actually see elements of his or her normal vision missing or not in focus. Missing visual elements resemble the missing pixels in a digital image while unfocused vision is dim and washed out.

For the pilot suffering the effects of hypoxic hypoxia, a simple descent to a lower altitude may not be sufficient to reestablish vision. For example, a climb from 8,000 feet to 12,000 feet for 30 minutes does not mean a descent to 8,000 feet will rectify the problem. Visual acuity may not be regained for over an hour. Thus, it is important to remember, altitude and fatigue have a profound effect on a pilot’s ability to see.

High Intensity Lighting
If, during the flight, any high intensity lighting areas are encountered, attempt to turn the aircraft away and fly in the periphery of the lighted area. This will not expose the eyes to such a large amount of light all at once. If possible, plan your route to avoid direct over flight of built-up, brightly lit areas.

Flightdeck Lighting
Flightdeck lighting should be kept as low as possible so that the light does not monopolize night vision. After reaching the desired flight altitude, pilots should allow time to adjust to the flight conditions. This includes readjustment of instrument lights and orientation to outside references. During the adjustment period, night vision should continue to improve until optimum night adaptation is achieved. When it is necessary to read maps, charts, and checklists, use a dim white light flashlight and avoid shining it in your or any other crewmember’s eyes.

Airfield Precautions
Often time, pilots have no say in how airfield operations are handled, but listed below are some precautions that can be taken to make night flying safer and help protect night vision.

  • Airfield lighting should be reduced to the lowest usable intensity.
  • Maintenance personnel should practice light discipline with headlights and flashlights.
  • Position the aircraft at a part of the airfield where the least amount of lighting exists.
  • Select approach and departure routes that avoid highways and residential areas where illumination can impair night vision.
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Navigation: Basic Radio Principles

A radio wave is an electromagnetic (EM) wave with frequency characteristics that make it useful. The wave travels long distances through space (in or out of the atmosphere) without losing too much strength. An antenna is used to convert electric current into a radio wave so it can travel through space to the receiving antenna, which converts it back into an electric current for use by a receiver. Today, we’ll take a look at an excerpt from the Instrument Flying Handbook (FAA-H-8083-15B).

How Radio Waves Propagate
All matter has a varying degree of conductivity or resistance to radio waves. The Earth itself acts as the greatest resistor to radio waves. Radiated energy that travels near the ground induces a voltage in the ground that subtracts energy from the wave, decreasing the strength of the wave as the distance from the antenna becomes greater. Trees, buildings, and mineral deposits affect the strength to varying degrees. Radiated energy in the upper atmosphere is likewise affected as the energy of radiation is absorbed by molecules of air, water, and dust. The characteristics of radio wave propagation vary according to the signal frequency and the design, use, and limitations of the equipment.
9-1
Ground Wave
A ground wave travels across the surface of the Earth. You can best imagine a ground wave’s path as being in a tunnel or alley bounded by the surface of the Earth and by the ionosphere, which keeps the ground wave from going out into space. Generally, the lower the frequency, the farther the signal travels.

Ground waves are usable for navigation purposes because they travel reliably and predictably along the same route day after day and are not influenced by too many outside factors. The ground wave frequency range is generally from the lowest frequencies in the radio range (perhaps as low as 100 Hz) up to approximately 1,000 kHz (1 MHz). Although there is a ground wave component to frequencies above this, up to 30 MHz, the ground wave at these higher frequencies loses strength over very short distances.

Sky Wave
The sky wave, at frequencies of 1 to 30 MHz, is good for long distances because these frequencies are refracted or “bent” by the ionosphere, causing the signal to be sent back to Earth from high in the sky and received great distances away. Used by high frequency (HF) radios in aircraft, messages can be sent across oceans using only 50 to 100 watts of power. Frequencies that produce a sky wave are not used for navigation because the pathway of the signal from transmitter to receiver is highly variable. The wave is “bounced” off of the ionosphere, which is always changing due to the varying amount of the sun’s radiation reaching it (night/day and seasonal variations, sunspot activity, etc.). The sky wave is, therefore, unreliable for navigation purposes.

For aeronautical communication purposes, the sky wave (HF) is about 80 to 90 percent reliable. HF is being gradually replaced by more reliable satellite communication.

Space Wave
When able to pass through the ionosphere, radio waves of 15 MHz and above (all the way up to many GHz), are considered space waves. Most navigation systems operate with signals propagating as space waves. Frequencies above 100 MHz have nearly no ground or sky wave components. They are space waves, but (except for global positioning system (GPS)) the navigation signal is used before it reaches the ionosphere so the effect of the ionosphere, which can cause some propagation errors, is minimal. GPS errors caused by passage through the ionosphere are significant and are corrected for by the GPS receiver system.

Space waves have another characteristic of concern to users.Space waves reflect off hard objects and may be blocked if the object is between the transmitter and the receiver. Site and terrain error, as well as propeller/rotor modulation error in very high omnidirectional range (VOR) systems, is caused by this bounce. Instrument landing system (ILS) course distortion is also the result of this phenomenon, which led to the need for establishment of ILS critical areas.

Generally, space waves are “line of sight” receivable, but those of lower frequencies “bend” somewhat over the horizon. The VOR signal at 108 to 118 MHz is a lower frequency than distance measuring equipment (DME) at 962 to 1213 MHz. Therefore, when an aircraft is flown “over the horizon” from a VOR/DME station, the DME is normally the first to stop functioning.

Disturbances to Radio Wave Reception
Static distorts the radio wave and interferes with normal reception of communications and navigation signals. Lowfrequency airborne equipment, such as automatic direction finder (ADF) and LORAN (LOng RAnge Navigation), are particularly subject to static disturbance. Using very high frequency (VHF) and ultra-high frequency (UHF) frequencies avoids many of the discharge noise effects. Static noise heard on navigation or communication radio frequencies may be a warning of interference with navigation instrument displays. Some of the problems caused by precipitation static (P-static) are:

  • Complete loss of VHF communications.
  • Erroneous magnetic compass readings.
  • Aircraft flying with one wing low while using the autopilot.
  • High-pitched squeal on audio.
  • Motorboat sound on audio.
  • Loss of all avionics.
  • Inoperative very-low frequency (VLF) navigation system.
  • Erratic instrument readouts.
  • Weak transmissions and poor radio reception.
  • St. Elmo’s Fire.
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CFI Brief: 14 CFR §91.211 Supplemental Oxygen

I hope you thoroughly read Monday’s post on oxygen regulations, if not you could be in trouble answering this two question pop quiz to start of today’s blog. NO cheating!

1. When operating an aircraft at cabin pressure altitudes above 12,500 feet MSL up to and including 14,000 feet MSL, supplemental oxygen shall be used during
A—the entire flight time at those altitudes.
B—that flight time in excess of 10 minutes at those altitudes.
C—that flight time in excess of 30 minutes at those altitudes.

2. Unless each occupant is provided with supplemental oxygen, no person may operate a civil aircraft of U.S. registry above a maximum cabin pressure altitude of
A—12,500 feet MSL.
B—14,000 feet MSL.
C—15,000 feet MSL.

The correct answer to question 1 is C, No person may operate civil aircraft at cabin pressure altitudes above 12,500 feet MSL up to and including 14,000 feet MSL, unless the required minimum flight crew uses supplemental oxygen for that part of the flight at those altitudes that is more than 30 minutes duration.

The correct answer to question 2 is also C, No person may operate a civil aircraft at cabin pressure altitudes above 15,000 feet MSL unless each occupant is provided with supplemental oxygen.

You can find both of these answers outlined in 14 CFR §91.211, specifically section (a) as shown in the excerpt below.

§91.211 Supplemental oxygen.
(a) General. No person may operate a civil aircraft of U.S. registry—
(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;
(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and
(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant of the aircraft is provided with supplemental oxygen.

One thing I like to point out when discussing regulatory requirements for the use of oxygen is that everybody’s physiology is a bit different. Based on an individuals physical condition and characteristics, oxygen deprivation may be felt at altitudes below those outlined in the regulations. With that said it is always a good idea to have oxygen available and in use when flying above 5,000′ MSL at night and 10,000′ MSL during the day.

If you want to learn more about the types of oxygen systems available to pilots check out section 7 of the Pilots Handbook of Aeronautical Knowledge (FAA-H-8083-25B).

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