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Aerodynamics: Cruise Flight

Cruise flight centers on two basic principles: how far we can fly, and for how long. How far we can fly is defined as the aircraft’s range. How long we can fly is defined as endurance. Today’s post is an excerpt from our textbook Aerodynamics for Aviators.

When flying, we generally consider range in two ways:

  1. Maximizing the distance we fly for a given fuel load.
  2. Traveling a specified distance while burning minimum fuel.

Endurance
It’s important to understand that range and endurance are not the same. Range relates to distance, endurance relates to time. The formula for endurance is:

endurance = hours ÷ fuel

Hours is simply flight time expressed in whatever units you want: hours, minutes or seconds. Fuel can be expressed in gallons or pounds. A pilot who wants to achieve maximum endurance would slow the aircraft to the minimum power required speed. Figure 5-24 shows the minimum power point being the lowest point in the drag curve.

5-24

Figure 5-24. Maximum endurance.

If the aircraft were to slow even further, to point A, drag would increase rapidly, more power would be required, and the engine would burn more fuel. If the aircraft were to accelerate above point B, drag also increases, which increases fuel burn. As you can see, flying at maximum endurance speed is not practical in the real world; you may save fuel but it would take forever to get to the destination. This speed is also not practical for operations such as holding because it is generally close to stall. From a practical standpoint, endurance comes from the selection of a cruise power setting of 55%, 65%, or 75% endurance charts. The point of this type of flying is generally to minimize or eliminate fuel stops (very time consuming) along the route, or to minimize fuel burn for cost purposes—not necessarily to stay aloft for hours on end.

Range
Range can be broken down into two parts: specific range and total range. An easy way to understand the difference is to use a car trip scenario. If I have a car that has a 20 gallon fuel tank and gets 30 miles per gallon, I can travel 600 miles on one tank of gas. The specific range in this example is 30 miles per gallon, and the total range is 600 miles. In an airplane, specific range is how many nautical miles you can travel on one gallon or pound of fuel. The total range is how far the airplane can fly with the remaining fuel load on board the aircraft. The definition for specific range is:

specific range = NM ÷ gallons of fuel (Note: pounds can be inserted for gallons.)

Specific range is affected by three things: (1) aircraft weight, (2) altitude, and (3) configuration. The maximum range of the aircraft can be found at L/DMAX. Unlike endurance, which is found on the drag curve where minimum power is required, maximum range is found where the ratio of speed to power required is the greatest. This is located on the graph by drawing a tangent line from the origin to the power required curve (Figure 5-24). Another way to think about this is that as you move from the origin point along the tangent line toward L/DMAX you increase airspeed at a greater rate than fuel burn (think of the ratio). At L/DMAX, the ratio of fuel to airspeed should be 1. At any speed above L/DMAX, the fuel burn ratio increases at a greater rate than the airspeed. Therefore, L/DMAX is the point where the speed-to-power ratio required is the greatest.

Another aspect of range that we need to examine is the effect of weight on range. Because L/DMAX occurs at a specific angle of attack, and most general aviation airplanes do not have AOA indicators, the airspeed has to be varied as weight changes to maintain a constant AOA. Figure 5-25 illustrates this: as weight increases, the speed must be increased to maintain the AOA. This is because as weight is increased, the AOA must be increased to produce more lift; the only way to lower the AOA is to increase speed. As weight decreases, the speed must decrease. The reasoning is that as the aircraft becomes lighter, the AOA is lowered to compensate for less weight; the only way to increase AOA is to reduce speed (Figure 5-25).

5-25

Figure 5-25. The effect of weight on range.

The effect of altitude on range can be seen in Figure 5-26. Flights operating at high altitude require a higher TAS, which will require more power.

5-26

Figure 5-26. The effect of altitude on range.

Another aspect of cruise flight relating to range and endurance, one that is often not talked about in textbooks, is cruise performance. From a practical standpoint, the pilot will not fly the aircraft at maximum endurance or range—it is just too slow. In reality, pilots often operate propeller-driven airplanes at 55%, 65%, or 75% best power or endurance.

In order to calculate how to get to your destination as fast as possible, find the highest true airspeed for your aircraft. Most fixed-gear single-engine aircraft that cruise in the 110–130 knot range will have their highest TAS in the 6,000 to 7,000-foot range. This is a good place to start; however, the wind, terrain, and the need for fuel stops will dictate the altitude and speed at which the aircraft ultimately flies.

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CFI Brief: What is Aeronautical Decision Making?

Aeronautical decision making (ADM) is a systematic approach to the mental process used by aircraft pilots to consistently determine the best course of action in response to a given set of circumstances. ADM is vital process allowing pilots to safely and efficiently manage risk. Although there is no way to eliminate the associated risks and hazards that come with aviation the proper application of ADM will allow the pilot to limit exposure to risks and hazards.

Risk Management is the part of the decision making process which relies on situational awareness, problem recognition, and good judgment to reduce risks associated with each flight.

The ADM process addresses all aspects of decision making in the cockpit and identifies the steps involved in good decision making. Steps for good decision making are:

  1. Identifying personal attitudes hazardous to safe flight.
  2. Learning behavior modification techniques.
  3. Learning how to recognize and cope with stress.
  4. Developing risk assessment skills.
  5. Using all resources in a multicrew situation.
  6. Evaluating the effectiveness of one’s ADM skills.

There are a number of classic behavioral traps into which pilots have been known to fall. Pilots, particularly those with considerable experience, as a rule always try to complete a flight as planned, please passengers, meet schedules, and generally demonstrate that they have the “right stuff.” These tendencies ultimately may lead to practices that are dangerous and often illegal, and may lead to a mishap. All experienced pilots have fallen prey to, or have been tempted by, one or more of these tendencies in their flying careers. These dangerous tendencies or behavior patterns, which must be identified and eliminated, include:

Peer Pressure. Poor decision making based upon emotional response to peers rather than evaluating a situation objectively.

Mind Set. The inability to recognize and cope with changes in the situation different from those anticipated or planned.

Get-There-Itis. This tendency, common among pilots, clouds the vision and impairs judgment by causing a fixation on the original goal or destination combined with a total disregard for any alternative course of action.

Duck-Under Syndrome. The tendency to sneak a peek by descending below minimums during an approach. Based on a belief that there is always a built-in “fudge” factor that can be used or on an unwillingness to admit defeat and shoot a missed approach.

Scud Running. Pushing the capabilities of the pilot and the aircraft to the limits by trying to maintain visual contact with the terrain while trying to avoid physical contact with it. This attitude is characterized by the old pilot’s joke: “If it’s too bad to go IFR, we’ll go VFR.”

Continuing Visual Flight Rules (VFR) into instrument conditions often leads to spatial disorientation or collision with ground/obstacles. It is even more dangerous if the pilot is not instrument qualified or current.

Getting Behind the Aircraft. Allowing events or the situation to control your actions rather than the other way around. Characterized by a constant state of surprise at what happens next.

Loss of Positional or Situation Awareness. Another case of getting behind the aircraft which results in not knowing where you are, an inability to recognize deteriorating circumstances, and/or the misjudgment of the rate of deterioration.

Operating Without Adequate Fuel Reserves. Ignoring minimum fuel reserve requirements, either VFR or Instrument Flight Rules (IFR), is generally the result of overconfidence, lack of flight planning, or ignoring the regulations.

Descent Below the Minimum Enroute Altitude. The duck-under syndrome (mentioned above) manifesting itself during the enroute portion of an IFR flight.

Flying Outside the Envelope. Unjustified reliance on the (usually mistaken) belief that the aircraft’s high performance capability meets the demands imposed by the pilot’s (usually overestimated) flying skills.

Neglect of Flight Planning, Preflight Inspections, Checklists, Etc. Unjustified reliance on the pilot’s short and long term memory, regular flying skills, repetitive and familiar routes, etc.

Each ADM student should take the Self-Assessment Hazardous Attitude Inventory Test in order to gain a realistic perspective on his/her attitudes toward flying. The inventory test requires the pilot to provide a response which most accurately reflects the reasoning behind his/her decision. The pilot must choose one of the five given reasons for making that decision, even though the pilot may not consider any of the five choices acceptable. The inventory test presents extreme cases of incorrect pilot decision making in an effort to introduce the five types of hazardous attitudes.

ADM addresses the following five hazardous attitudes:

  1. Antiauthority (don’t tell me!). This attitude is found in people who do not like anyone telling them what to do. In a sense they are saying “no one can tell me what to do.” They may be resentful of having someone tell them what to do or may regard rules, regulations, and procedures as silly or unnecessary. However, it is always your prerogative to question authority if you feel it is in error. The antidote for this attitude is: Follow the rules. They are usually right.
  2. Impulsivity (do something quickly!) is the attitude of people who frequently feel the need to do something—anything—immediately. They do not stop to think about what they are about to do, they do not select the best alternative, and they do the first thing that comes to mind. The antidote for this attitude is: Not so fast. Think first.
  3. Invulnerability (it won’t happen to me). Many people feel that accidents happen to others, but never to them. They know accidents can happen, and they know that anyone can be affected. They never really feel or believe that they will be personally involved. Pilots who think this way are more likely to take chances and increase risk. The antidote for this attitude is: It could happen to me.
  4. Macho (I can do it). Pilots who are always trying to prove that they are better than anyone else are thinking “I can do it—I’ll show them.” Pilots with this type of attitude will try to prove themselves by taking risks in order to impress others. While this pattern is thought to be a male characteristic, women are equally susceptible. The antidote for this attitude is: taking chances is foolish.
  5. Resignation (what’s the use?). Pilots who think “what’s the use?” do not see themselves as being able to make a great deal of difference in what happens to them. When things go well, the pilot is apt to think that’s good luck. When things go badly, the pilot may feel that “someone is out to get me,” or attribute it to bad luck. The pilot will leave the action to others, for better or worse. Sometimes, such pilots will even go along with unreasonable requests just to be a “nice guy.” The antidote for this attitude is: I’m not helpless. I can make a difference.

Hazardous attitudes which contribute to poor pilot judgment can be effectively counteracted by redirecting that hazardous attitude so that appropriate action can be taken. Recognition of hazardous thoughts is the first step in neutralizing them in the ADM process. Pilots should become familiar with a means of counteracting hazardous attitudes with an appropriate antidote thought. When a pilot recognizes a thought as hazardous, the pilot should label that thought as hazardous, then correct that thought by stating the corresponding antidote.

If you hope to succeed at reducing stress associated with crisis management in the air or with your job, it is essential to begin by making a personal assessment of stress in all areas of your life. Good cockpit stress management begins with good life stress management. Many of the stress coping techniques practiced for life stress management are not usually practical in flight. Rather, you must condition yourself to relax and think rationally when stress appears. The following checklist outlines some thoughts on cockpit stress management.

  1. Avoid situations that distract you from flying the aircraft.
  2. Reduce your workload to reduce stress levels. This will create a proper environment in which to make good decisions.
  3. If an emergency does occur, be calm. Think for a moment, weigh the alternatives, then act.
  4. Maintain proficiency in your aircraft; proficiency builds confidence. Familiarize yourself thoroughly with your aircraft, its systems, and emergency procedures.
  5. Know and respect your own personal limits.
  6. Do not let little mistakes bother you until they build into a big thing. Wait until after you land, then “debrief” and analyze past actions.
  7. If flying is adding to your stress, either stop flying or seek professional help to manage your stress within acceptable limits.

The DECIDE Model, comprised of a six-step process, is intended to provide the pilot with a logical way of approaching decision making. The six elements of the DECIDE Model represent a continuous loop decision process which can be used to assist a pilot in the decision making process when he/she is faced with a change in a situation that requires a judgment. This DECIDE Model is primarily focused on the intellectual component, but can have an impact on the motivational component of judgment as well. If a pilot practices the DECIDE Model in all decision making, its use can become very natural and could result in better decisions being made under all types of situations.

  1. Detect. The decisionmaker detects the fact that change has occurred.
  2. Estimate. The decisionmaker estimates the need to counter or react to the change.
  3. Choose. The decisionmaker chooses a desirable outcome (in terms of success) for the flight.
  4. Identify. The decisionmaker identifies actions which could successfully control the change.
  5. Do. The decisionmaker takes the necessary action.
  6. Evaluate. The decisionmaker evaluates the effect(s) of his/her action countering the change.

 

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CFI Brief: Would I be a good flight instructor?

Have you ever thought about taking you’re flying career to the next level and becoming a Certified Flight Instructor?  Well, today we are going to take a quick look at some of the characteristics and responsibilities that and aviation instructor must possess. Many students view an aviation instructor as an authority, so it is important for an instructor to project a knowledgeable and professional image at all times.

One of the responsibilities of a good flight instructor is maintaining a high level of professionalism, which relates directly to the instructor’s public image. Characteristics of an instructor’s professionalism include:

  1. Sincerity. Any facade of instructor pretentiousness, whether it be real or mistakenly assumed by the student, will immediately cause the student to lose confidence in the instructor, and little learning will be accomplished. Anything less than sincere performance destroys the effectiveness of the professional instructor.
  1. Acceptance of the student. The professional relationship between the instructor and the student should be based on a mutual acknowledgment that both the student and the instructor are important to each other, and both are working toward the same objectives. Under no circumstances should an instructor do anything which implies degradation of the student.
  1. Personal appearance and habits. A flight instructor who is rude, thoughtless, and inattentive cannot hold the respect of the students, regardless of his/her piloting ability.
  1. Demeanor. The instructor should avoid erratic movements, distracting speech habits, and capricious changes in mood.
  1. Safety practices and accident prevention. A flight instructor must meticulously observe all regulations and recognized safety practices during all flight operations.
  1. Proper language. The use of profanity and obscene language leads to distrust, or at best, to a lack of complete confidence.
  1. Self-improvement. Professional flight instructors must never become complacent or satisfied with their own qualifications and ability.

As a flight instructor you will want to strive daily to practice the items in the “Instructor Do’s” list , and do your best to stay away from the “Instructor Don’ts” list. From the Aviation Instructors Handbook (FAA-H-8083-9A):

CFI Do & Donts

One “don’t” to make mention of; personal hygiene goes both ways. Nothing’s worse then a couple people stuck in a small plane who haven’t showered!

An aviation instructor must also be self-aware of numerous responsibilities. There are five main responsibilities of an aviation instructor.

  1. Helping students learn.
  2. Providing adequate instruction.
  3. Demanding adequate standards of performance.
  4. Emphasizing the positive.
  5. Ensuring aviation safety.

To be an effective instructor you will need to maintain a high level of student motivation by making each lesson a pleasurable experience. It’s important to realize that people are not always attracted to something because it is easy. Most will put forth the required effort to produce rewards such as self-enhancement and personal satisfaction.

As an instructor you should make learning to fly interesting by keeping the students apprised of the course and lesson objectives. Not knowing the objectives leads the student to confusion, disinterest, and uneasiness. Instead instructors should guide their students in exploration and experimentation, to help them develop their own capabilities and self-confidence.

For instruction to produce the desired results, instructors must carefully and correctly analyze the personality, thinking, and ability of each student. Students who have been incorrectly analyzed as slow thinkers may actually be quick thinkers, but act slowly or at the wrong time because of lack of confidence. Slow students can often be helped by assigning sub goals which are more easily attainable than the normal learning goals. This allows the student to practice elements of the task as confidence and ability grows.

Apt students also create problems. Because they make less mistakes, they may assume that the correction of errors is unimportant. Such overconfidence results in faulty performance. A good instructor will constantly raise the standard of performance demanded of apt students and will demand greater effort.

Flight instructors fail to provide competent instruction when they permit their students to get by with a substandard performance, or without learning thoroughly some item of knowledge pertinent to safe piloting. The positive approach to flight instruction points out to the student the pleasurable features of aviation before the unpleasant possibilities are discussed. One example of a positive approach is to include a normal round-trip flight to a nearby airport on the first instructional flight.

Anxiety, or fear, is probably the most significant psychological factor affecting flight instruction. The responses to anxiety vary greatly, ranging from hesitancy to act, to the impulse “to do something even if it’s wrong.” Some students may freeze in place and do nothing, while others may do unusual things without rational thought or reason. Normal reaction to anxiety can be countered by reinforcing the student’s enjoyment of flying, and by teaching them to treat fear as a normal reaction rather than ignoring it. Normal individuals react to stress by responding rapidly and exactly, within the limits of their experience and training. Abnormal reactions to stress are evidenced by:

  • Autonomic responses, such as sweating, rapid heart rate, paleness, etc.
  • Inappropriate reactions, such as extreme overcooperation, painstaking self-control; inappropriate laughter or singing, very rapid changes in emotions, and motion sickness under stress
  • Marked changes in mood on different lessons, such as excellent morale followed by deep depressio
  • Severe anger at the flight instructor, service personnel, or others.

So you think you have what it takes to take the next step in your flying career? Instructing can be an extremely fun and rewarding experience for any aviator. The majority of the information discussed above is all available in the Aviation Instructors Handbook (FAA-H-8083-9A). The information contained in this book will be required knowledge for anyone wishing to obtain a flight or ground instructor certificate. I would also encourage you to check out The Flight Instructor Survival Guide by Arlynn McMahon. It’s an insightful, funny at times and enjoyable read. Also a great present for your instructor (hint, hint)!
CFI-SG_Web

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Aircraft Performance: Changing Airspeed in Straight-and-Level Flight

Normal cruise involves setting cruise power, holding cruise altitude, and accepting the airspeed that is achieved, which should be close to the figure published in your Pilot’s Operating Handbook. On occasions, however, there is a need to fly at other than normal cruise airspeed. Today, we’ll discuss the basics of changing speeds in straight-and-level flight with an excerpt from The Pilot’s Manual: Instrument Flying (PM-3D).

This requires a different pitch attitude and a different power setting. To slow the airplane, the pilot reduces power and gradually raises the pitch attitude to maintain altitude; to increase airspeed, the pilot increases power, and gradually lowers the pitch attitude to maintain altitude.

Once the desired airspeed is achieved, the pilot adjusts the power to maintain it. The precise power required for steady flight will depend upon the amount of total drag, which, in level flight, varies with angle of attack and airspeed. Higher power will be required for:

  • high speed cruise (when total drag is high mainly due to parasite drag); and
  • low speed cruise (when total drag is high mainly due to induced drag).

pm-3d_4-25
Medium power is required for normal cruise. The ASI confirms whether or not correct power is set. The ASI is the primary performance guide to power requirements during level flight if you fly a particular airspeed.

Practicing airspeed changes in cruise is excellent instrument flying practice since pitch, bank (and balance) and power changes must all be coordinated to maintain constant altitude and heading. When the pilot changes power, a single-engined propeller- driven airplane will tend to move around all three axes of movement. If the propeller rotates clockwise as seen from the cockpit (the usual case), adding power will cause the nose to pitch up and yaw left, with a tendency for the airplane to roll left.

The pilot can counteract this by applying forward elevator pressure to prevent the nose pitching up, with right rudder and right aileron pressure to overcome the tendency to yaw and roll left. The converse applies when reducing power, hold the nose up and apply left rudder pressure. Refer to the AI to keep the wings level and hold the pitch attitude, and keep the ball centered.

Some hints on changing cruising speed follow:

  • The attitude indicator gives a direct picture of pitch and bank attitudes.
  • The ball gives a direct indication of coordination.
  • Useful performance instruments are the altimeter and VSI—they ensure altitude is being maintained, and the heading indicator to ensure heading is being maintained.
  • The airspeed indicator indicates the power requirements. If too slow, add more power; if too fast, reduce power.

The pilot’s scan rate of the flight instruments during any power change needs to be reasonably fast to counteract the pitch/yaw effects smoothly and accurately. For this reason, it is good to develop the skill of judging power changes by throttle movement and engine sound, rather than only by observation of the power indicator. This allows the pilot to concentrate on the flight instruments until after the power change has been made, at which time a quick glance at the power indicator for fine adjustment suffices.

When you memorize the approximate power settings necessary to maintain the various cruise speeds, then power handling and airspeed changes become simpler to manage.

Small airspeed changes (say five knots either way) can generally be handled by a single small power change, then allowing the airplane to gradually slow down or accelerate to the desired speed. Large airspeed changes, however, are most efficiently achieved within a few seconds by underpowering on the initial power change for a speed decrease, or overpowering on the initial power change for a speed increase. This allows more rapid deceleration or acceleration to the desired speed, at which time the necessary power to maintain that airspeed is set.

Once the desired airspeed is achieved and suitable power is set, the ASI will indicate if further fine adjustment of power to maintain airspeed is required. In level flight, the ASI is the primary guide to power requirements.

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CFI Brief: Caution for the wake turbulence from the departing 757

Today we are going to take a look at wake turbulence, which is the disturbed air left behind an airplane. Why you may ask is this important to us? This disturbed air left behind an aircraft can form tornado like vortices that are dangerous to all aircraft, particularly smaller general aviation aircraft operating behind a larger and heavier aircraft.

I’m sure you have heard of the term wake before, especially if you are a boater. A boats wake is very similar in nature to that of an aircraft. You can see from the image below as the boat motors along it displaces the water leaving behind a wake in the form of waves which spread in an outward direction.

boat wake

An aircraft’s wake is similar but differs in some characteristics and in the fact that typically wake turbulence created by an aircraft is not visible.

All aircraft leave two types of wake turbulence: Prop or jet blast, and wing-tip vortices.

Prop or jet blast is the thrust stream created by the engine. You will encounter this type of wake on the ground and is hazardous to light aircraft behind large aircraft which are either taxiing or running-up their engines. In the air, jet or prop blast dissipates rapidly.

Wing-tip vortices are a by-product of lift. As a wing produces lift, the higher static pressure area beneath the wing causes airflow around the wingtip to the lower pressure area above. To simplify the high pressure below the wing which creates lift wants to equalize with the lower pressure above the wing. The shortest point for the high pressure to move to the lower pressure area above the wing is at the wing tip. This high pressure moves outward, upward and around each wing-tip. However, because the wing and aircraft itself are moving, by the time the high pressure circulates around the tip to the top, the wing is now gone. This in turn creates vortices that trail behind each wing tip as seen in this image.

TP-P-01-27

The strength of a vortex is governed by the weight, speed, and the shape of the wing of the generating aircraft. Maximum vortex strength occurs when the generating aircraft is heavy, clean, and slow.  A heavy, clean, and slow aircraft will require a greater angle of attack (AoA) to great sufficient lift, as the AoA increases so does the pressure differential. The greater the pressure differential the stronger the vortice.

Vortices generated by large aircraft in flight tend to sink below the flight path of the generating aircraft at a rate of about 500 feet per minute. A pilot should fly at or above the larger aircraft’s flight path in order to avoid the wake turbulence created by the wing-tip vortices. Over time the vortices also tend to move apart and will drift downwind of the aircraft flight path. A common rule of thumb is to fly above and upwind of the path of other aircraft.

Close to the ground, vortices tend to move laterally. A crosswind will tend to hold the upwind vortex over the landing runway, while a tailwind may move the vortices of a preceding aircraft forward into the touchdown zone. Research has also shown that as vorticies come in contact striking the gorund that have a tendency to “bounce” back up as much as 250 feet.

To avoid wake turbulence when landing, a pilot should note the point where a preceding large aircraft touched down and then land past that point.

Wake Landing

 

On takeoff, lift off should be accomplished prior to reaching the rotation point of a preceding departing large aircraft; the flight path should then remain upwind and above the preceding aircraft’s flight path. If departing behind a landing large aircraft delay your takeoff point to a spot past where the landing aircraft touched down.

Wake TO

 

1. When landing behind a large aircraft, the pilot should avoid wake turbulence by staying
A—above the large aircraft’s final approach path and landing beyond the large aircraft’s touchdown point.
B—below the large aircraft’s final approach path and landing before the large aircraft’s touchdown point.
C—above the large aircraft’s final approach path and landing before the large aircraft’s touchdown point.

2. When departing behind a heavy aircraft, the pilot should avoid wake turbulence by maneuvering the aircraft
A—below and downwind from the heavy aircraft.
B—above and upwind from the heavy aircraft.
C—below and upwind from the heavy aircraft.

.

.

.

.
1. When landing behind a large aircraft stay at or above the large aircraft’s final approach path. Note its touchdown point and land beyond it.
Answer (B) is incorrect because below the flight path, you will fly into the sinking vortices generated by the large aircraft. Answer (C) is incorrect because by landing before the large aircraft’s touchdown point, you will have to fly below the preceding aircraft’s flight path, and into the vortices.

2. When departing behind a large aircraft, note the large aircraft’s rotation point, rotate prior to it, continue to climb above it, and request permission to deviate upwind of the large aircraft’s climb path until turning clear of the aircraft’s wake.

 

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CFI Brief: Deciphering the METAR

Today we are going to take a look at your most common type of weather report, the Aviation Routine Weather Report, abbreviated as METAR. A METAR is an observation of current surface weather reported in a standard international format. The purpose is to provide pilots with an accurate depiction of current weather conditions at an airport. METARs are issued on a regularly scheduled basis, usually somewhere close to the top of the hour, unless significant weather changes have occurred. If this is the case then a special METAR or ‘SPECI’ will be issued at any time between routine reports.

Here is an example of a routine METAR report for a station location.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

This METAR reports contains the following typical information in sequential order which is the standard formatted coding for all METAR reports.

1. Type of report. There are two types of METAR reports. The first is the routine METAR report that is transmitted on a regular time interval. The second is the aviation selected SPECI. This is a special report that can be given at any time to update the METAR for rapidly changing weather conditions, aircraft mishaps, or other critical information.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR]

2. Station identifier. A four-letter code as established by the International Civil Aviation Organization (ICAO). In the 48 contiguous states, a unique three-letter identifier is preceded by the letter “K.” For example, Gregg County Airport in Longview, Texas, is identified by the letters “KGGG,” K being the country designation and GGG being the airport identifier. In other regions of the world, including Alaska and Hawaii, the first two letters of the four-letter ICAO identifier indicate the region, country, or state. Alaska identifiers always begin with the letters “PA” and Hawaii identifiers always begin with the letters “PH.” Station identifiers can be found by searching various websites such as DUATS and NOAA’s Aviation Weather Aviation Digital Data Services (ADDS).

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

3. Date and time of report. Depicted in a six-digit group (161753Z). The first two digits are the date. The last four digits are the time of the METAR/SPECI, which is always given in coordinated universal time (UTC). A “Z” is appended to the end of the time to denote the time is given in Zulu time (UTC) as opposed to local time. This METAR was issued on the 16th at 1753 Zulu.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

4. Modifier. Denotes that the METAR/SPECI came from an automated source or that the report was corrected. If the notation “AUTO” is listed in the METAR/SPECI, the report came from an automated source. It also lists “AO1” (for no precipitation discriminator) or “AO2” (with precipitation discriminator) in the “Remarks” section to indicate the type of precipitation sensors employed at the automated station. When the modifier “COR” is used, it identifies a corrected report sent out to replace an earlier report that contained an error. If this was the case for this example the word AUTO would be replaced with COR.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

5. Wind. Reported with five digits (14021KT) unless the speed is greater than 99 knots, in which case the wind is reported with six digits. The first three digits indicate the direction the true wind is blowing from in tens of degrees. If the wind is variable, it is reported as “VRB.” The last two digits indicate the speed of the wind in knots unless the wind is greater than 99 knots, in which case it is indicated by three digits. If the winds are gusting, the letter “G” follows the wind speed (G26KT). After the letter “G,” the peak gust recorded is provided. If the wind direction varies more than 60° and the wind speed is greater than six knots, a separate group of numbers, separated by a “V,” will indicate the extremes of the wind directions.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

6. Visibility. The prevailing visibility (¾ SM) is reported in statute miles as denoted by the letters “SM.” It is reported in both miles and fractions of miles. At times, runway visual range (RVR) is reported following the prevailing visibility. RVR is the distance a pilot can see down the runway in a moving aircraft. When RVR is reported, it is shown with an R, then the runway number followed by a slant, then the visual range in feet. For example, when the RVR is reported as R17L/1400FT, it translates to a visual range of 1,400 feet on runway 17 left.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

7. Weather. Can be broken down into two different categories: qualifiers and weather phenomenon (+TSRA BR). First, the qualifiers of intensity, proximity, and the descriptor of the weather are given. The intensity may be light (–), moderate ( ), or heavy (+). Proximity only depicts weather phenomena that are in the airport vicinity. The notation “VC” indicates a specific weather phenomenon is in the vicinity of five to ten miles from the airport. Descriptors are used to describe certain types of precipitation and obscurations. Weather phenomena may be reported as being precipitation, obscurations, and other phenomena, such as squalls or funnel clouds. Descriptions of weather phenomena as they begin or end and hailstone size are also listed in the “Remarks” sections of the report. The coding for qualifier and weather phenomena are shown here in this chart. The weather groups are constructed by considering columns 1–5 in this table sequence: intensity, followed by descriptor, followed by weather phenomena. As an example “heavy rain showers” is coded as +SHRA.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

TP-UAS_3-5

8. Sky condition. Always reported in the sequence of amount, height, and type or indefinite ceiling/height (vertical visibility) (BKN008 OVC012CB, VV003). The heights of the cloud bases are reported with a three-digit number in hundreds of feet AGL. Clouds above 12,000 feet are not detected or reported by an automated station. The types of clouds, specifically towering cumulus (TCU) or cumulonimbus (CB) clouds, are reported with their height. Contractions are used to describe the amount of cloud coverage and obscuring phenomena. The amount of sky coverage is reported in eighths of the sky from horizon to horizon as shown in this table. Less than 1/8 is abbreviated as Sky Clear, Clear, or Few. 1/8 – 2/8 Few. 3/8 – 4/8 Scattered. 5/8 – 7/8 Broken. 8/8 Overcast. For aviation purposes, the ceiling is the lowest broken or overcast layer, or vertical visibility into an obscuration.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

TP-UAS_3-6

9. Temperature and dew point. The air temperature and dew point are always given in degrees Celsius (C) or (18/17). Temperatures below 0 °C are preceded by the letter “M” to indicate minus. 10.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

10. Altimeter setting. Reported as inches of mercury (“Hg) in a four-digit number group (A2970). It is always preceded by the letter “A.” Rising or falling pressure may also be denoted in the “Remarks” sections as “PRESRR” or “PRESFR,” respectively.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

11. Remarks—the remarks section always begins with the letters “RMK.” Comments may or may not appear in this section of the METAR. The information contained in this section may include wind data, variable visibility, beginning and ending times of particular phenomenon, pressure information, and various other information deemed necessary. An example of a remark regarding weather phenomenon that does not fit in any other category would be: OCNL LTGICCG. This translates as occasional lightning in the clouds and from cloud to ground. Automated stations also use the remarks section to indicate the equipment needs maintenance.

METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

Putting it all together you would read this sample METAR as follows:

Routine METAR for Gregg County Airport for the 16th day of the month at 1753 zulu automated source. Winds are 140 at 21 knots gusting to 26 knots. Visibility is ¾ statute mile. Thunderstorms with heavy rain and mist. Ceiling is broken at 800 feet, overcast at 1,200 feet with cumulonimbus clouds. Temperature 18 °C and dew point 17 °C. Barometric pressure is 29.70″Hg and falling rapidly.

TAF-METAR

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Regulations: Notices to Airmen

Today, we’ll take a look at NOTAM’s with an excerpt from Bob Gardner’s textbook The Complete Private Pilot (PPT-12). For all of the regulations pertaining to aviation, check out our annual FAR/AIM series.

Information that might affect the safety of a flight, such as a runway closure, Temporary Flight Restriction (TFR), NAVAID outage, lighting system change, etc., is available from your flight service station briefer.

Your briefer has access to NOTAMs. So do you, at PilotWeb. If you use one of the computer flight planning products such as DUATS or the AOPA flight planner, you will also receive current NOTAMS—but be aware that TFRs can pop up without warning. Always check for them with flight service before takeoff to avoid being intercepted by F-16s or Coast Guard helicopters and forced to land.

If you want to know about VOR outages, runway closures, men and equipment on the runway, etc., look for or ask for D NOTAMs. For long cross-countries it is always valuable to call one of the fixed-base operators at the destination airport for last-minute information, such as “the power is out and we can’t pump gas!”

To make it easier for pilots to scan through a list of NOTAMs for information specific to their flight, the FAA uses “key words” in the first line of text. See the figure below—although this FAA document does not include recent additions: ODP, SID, STAR, CHART, DATA, IAP, VFP, ROUTE, SPECIAL, or (O); also, the keyword RAMP will no longer be used. As a VFR pilot, you are definitely interested in Visual Flight Procedure (VFP) and Obstacle Departure Procedure (ODP) NOTAMs which, although intended for instrument pilots, might contain information useful to you.

Every 28 days the FAA releases the Notices to Airmen publication that contains all current NOTAM (D)s and FDC NOTAMs, except for Temporary Flight Restrictions. When a NOTAM is published here (or in the Chart Supplements U.S.) it no longer shows up on the briefer’s screen; if you don’t ask the briefer for any published NOTAMs that will affect your flight, you will never find out about them. You can get this publication online at https://pilotweb.nas.faa.gov/PilotWeb/.

notamD

Example of FAA NOTAM “key words” (see AIM Table 5-1-1 for more keywords and definitions). (Click to expand)

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CFI Brief: New GFA Supplement Figures

In the latest Airman Knowledge Testing Supplement for Instrument Rating (CT-8080-3F), the FAA has added several Graphical Forecast for Aviation (GFA) figures. These figures are 260 through 271 in the supplement and although the FAA has not yet added questions to the Instrument knowledge test on GFA, this weather tool is still something to become familiar with.

The GFA at the Aviation Weather Center (AWC) website is an interactive display providing continuously updated observed and forecast weather information over the continental United States (CONUS). It is intended to give users a complete picture of weather critical to aviation safety. The GFA display shows user-selected weather categories, each containing multiple fields of interest at altitudes from the surface up to FL480. Depending on the field of interest chosen, weather information is available from -6 in the past (observed) to +15 hours in the future (forecast).

The GFA is not considered a weather product but an aggregate of several existing weather products. The information and data from the various weather products are overlaid on a high-resolution basemap of the United States: www.aviationweather.gov/gfa. The user selects flight levels and current time period for either observed or forecast weather information. Mouse-clicking or hovering over the map provides additional information in textual format, such as current METAR or TAF for a selected airport. The GFA replaces the textual area forecast (FA) for the CONUS and Hawaii with a more modern digital solution for obtaining weather information. The Aviation Surface Forecast and Aviation Cloud Forecast graphics are snapshot images derived from a subset of the aviation weather forecasts.

The Aviation Surface Forecast displays surface visibility with overlays of wind and gusts, predominant precipitation type (i.e., rain, snow, mix, ice, or thunderstorm) coincident with any cloud and predominant weather type (i.e., haze, fog, smoke, blowing dust/sand). The graphical AIRMETs (Airmen’s Meteorological Information) for instrument flight rules (IFR) and strong surface wind are overlaid. See FAA Figure 260. Forecast surface visibility is contoured for Low IFR (0 – 1 statute miles), IFR (1 – 3 statute miles), and Marginal VFR (MVFR; 3 – 5 statute miles) conditions. Visibilities in excess of 5 statute miles are not shown. Winds are depicted with a standard wind barb, in red when indicating gusts (see the figure below).

TP-I-02-02

Below are some sample questions for what you could expect to see on an FAA knowledge test in the near future using those aforementioned GFA figures.

1. (Refer to Figure 261.) The precipitation type forecast to occur over southern ND (area C) is
A—Freezing rain.
B—Freezing drizzle.
C—Moderate snow.instrument_261

2. (Refer to Figure 266.) Precipitation throughout Washington and Oregon is predominantly
A—Light rain and rain showers.
B—Heavy rain showers.
C—Freezing rain.instrument_266
3.(Refer to Figure 269.) The cloud coverage around area B on the Aviation Cloud Forecast is forecast to be
A—Bases at 6,000 feet, tops at 7,000.
B—BRKN tops at 7,000 feet.
C—OVC at 7,000 feet.instrument_269

Answers and explanations

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Human Factors: Optical Illusions

Of the senses, vision is the most important for safe flight. However, various terrain features and atmospheric conditions can create optical illusions. These illusions are primarily associated with landing. Since pilots must transition from reliance on instruments to visual cues outside the flight deck for landing at the end of an instrument approach, it is imperative that they be aware of the potential problems associated with these illusions and take appropriate corrective action. Today, we’ll take a look at the major illusions leading to landing errors with an excerpt from the Pilot’s Handbook of Aeronautical Knowledge.

Runway Width Illusion
A narrower-than-usual runway can create an illusion that the aircraft is at a higher altitude than it actually is, especially when runway length-to-width relationships are comparable. The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects along the approach path or landing short. A wider-thanusual runway can have the opposite effect with the risk of the pilot leveling out the aircraft high and landing hard or overshooting the runway.

Runway and Terrain Slopes Illusion
An upsloping runway, upsloping terrain, or both can create an illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this illusion will fly a lower approach. Downsloping runways and downsloping approach terrain can have the opposite effect.

FAA-H-8083-25B

(Click to expand)

Featureless Terrain Illusion
An absence of surrounding ground features, as in an overwater approach over darkened areas or terrain made featureless by snow, can create an illusion that the aircraft is at a higher altitude than it actually is. This illusion, sometimes referred to as the “black hole approach,” causes pilots to fly a lower approach than is desired.

Water Refraction
Rain on the windscreen can create an illusion of being at a higher altitude due to the horizon appearing lower than it is. This can result in the pilot flying a lower approach.

Haze
Atmospheric haze can create an illusion of being at a greater distance and height from the runway. As a result, the pilot has a tendency to be low on the approach. Conversely, extremely clear air (clear bright conditions of a high attitude airport) can give the pilot the illusion of being closer than he or she actually is, resulting in a high approach that may result in an overshoot or go around. The diffusion of light due to water particles on the windshield can adversely affect depth perception. The lights and terrain features normally used to gauge height during landing become less effective for the pilot.

Fog
Flying into fog can create an illusion of pitching up. Pilots who do not recognize this illusion often steepen the approach abruptly.

Ground Lighting Illusions
Lights along a straight path, such as a road or lights on moving trains, can be mistaken for runway and approach lights. Bright runway and approach lighting systems, especially where few lights illuminate the surrounding terrain, may create the illusion of less distance to the runway. The pilot who does not recognize this illusion will often fly a higher approach.

How To Prevent Landing Errors Due to Optical Illusions
To prevent these illusions and their potentially hazardous consequences, pilots can:

  1. Anticipate the possibility of visual illusions during approaches to unfamiliar airports, particularly at night or in adverse weather conditions. Consult airport diagrams and the Chart Supplement U.S. (formerly Airport/Facility Directory) for information on runway slope, terrain, and lighting.
  2. Make frequent reference to the altimeter, especially during all approaches, day and night.
  3. If possible, conduct an aerial visual inspection of unfamiliar airports before landing.
  4. Use Visual Approach Slope Indicator (VASI) or Precision Approach Path Indicator (PAPI) systems for a visual reference, or an electronic glideslope, whenever they are available.
  5. Utilize the visual descent point (VDP) found on many nonprecision instrument approach procedure charts.
  6. Recognize that the chances of being involved in an approach accident increase when an emergency or other activity distracts from usual procedures.
  7. Maintain optimum proficiency in landing procedures.

In addition to the sensory illusions due to misleading inputs to the vestibular system, a pilot may also encounter various visual illusions during flight. Illusions rank among the most common factors cited as contributing to fatal aviation accidents. Sloping cloud formations, an obscured horizon, a dark scene spread with ground lights and stars, and certain geometric patterns of ground light can create illusions of not being aligned correctly with the actual horizon. Various surface features and atmospheric conditions encountered in landing can create illusions of being on the wrong approach path. Landing errors due to these illusions can be prevented by anticipating them during approaches, inspecting unfamiliar airports before landing, using electronic glideslope or VASI systems when available, and maintaining proficiency in landing procedures.

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CFI Brief: Sunset Weather

What could be better than taking your significant other on a romantic sunset flight around your local airport? I’ll tell you what, taking your significant other on a romantic sunset flight during an absolutely epic sunset! Sounds awesome right, but just how are you suppose to know when an epic sunset is going to happen? Easy… check the forecast.

SunsetWX.com has come up with an algorithm to forecast the sunrise and sunset quality throughout the United States and all over the world! Take a look below at the sample sunset forecast for the United States.

Sunset Forecast

Areas of better sunset quality are denoted by warmer colors like the yellows, oranges and reds. It appears that the highest quality sunset will be visible throughout Central California according to this forecast. So if you happen to live in say Sacramento, CA it would be an excellent evening for that sunset cruise.

For the latest forecast visits www.SunsetWX.com and follow them on twitter @sunset_wx .

Now remember, since you will potentialy be flying prior to civil twilight, it is important to make sure your aircraft has the minimum required equipment under 14 CFR 91.205 for night flight. This is in addition to required equipment for day flight.

14 CFR 91.205

…(c) Visual flight rules (night). For VFR flight at night, the following instruments and equipment are required:

(1) Instruments and equipment specified in paragraph (b) of this section.

(2) Approved position lights.

(3) An approved aviation red or aviation white anticollision light system on all U.S.-registered civil aircraft. Anticollision light systems initially installed after August 11, 1971, on aircraft for which a type certificate was issued or applied for before August 11, 1971, must at least meet the anticollision light standards of part 23, 25, 27, or 29 of this chapter, as applicable, that were in effect on August 10, 1971, except that the color may be either aviation red or aviation white. In the event of failure of any light of the anticollision light system, operations with the aircraft may be continued to a stop where repairs or replacement can be made.

(4) If the aircraft is operated for hire, one electric landing light.

(5) An adequate source of electrical energy for all installed electrical and radio equipment.

(6) One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight.

 

To help you remember you can use this simple mnemonic ‘FLAPS’.

F uses (spare) or circuit breakers

L anding light (if for hire)

A nticollision lights

P osition lights

S ource of electricity

 

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