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CFI

CFI

ASA’s CFI offers insights on difficult concepts posed in FAA exams. Each post will break down an FAA question and deconstruct the answer in a way aimed to teach aviators how to more effectively prepare themselves for their FAA examinations.

Email your questions to CFI@asa2fly.com

CFI Brief: June 2017 Test Roll

June has been a busy month here at ASA headquarters and for the FAA. Let’s recap what all is going down in terms of Airman Testing.

The FAA has released updated Airman Certification Standards for both Private Pilot Airplane (FAA-S-ACS-6A) and Instrument Pilot Airplane (FAA-S-ACS-8A) effective June 2017. Additionally, the Commercial Pilot Airplane ACS was released, replacing the Practical Test Standards (8081-12). These are now available for purchase through the ASA website and can be found following the two links below, out with the old in with the new!

Private Pilot Airplane (ACS-6A)
Instrument Pilot Airplane (ACS-8A)
Commercial Pilot Airplane (ACS-7)

ACS-7_HiRes

Getting ready to take the Instrument Knowledge Exam? Be aware the FAA has released the new Airman Knowledge Testing Supplement for Instrument Rating (FAA-CT-8080-3F) now in effect at all testing centers. This supplement includes several new and updated figures and is available for purchase through the ASA website. This new supplement will be included in the 2018 Instrument Pilot Test Prep books and Prepware software and apps, available late July.

Airman Knowledge Testing Supplement for Instrument Pilot (FAA-CT-8080-3F)

CT-8080-3F_HiRes

In terms of the Airman Knowledge Exams, the FAA is reporting no substantial changes with respect to topics covered in pilot certificate/rating test banks for this June test roll cycle. We are getting a lot of calls asking if the FAA has begun testing on the new BasicMed rules and the answer is no. The FAA expects to develop test questions on the new BasicMed regulation in the future. Third-Class Medical questions will remain, since BasicMed is an addition to the medical certification structure, not a replacement of the Third-Class Medical Certificate.

The following topics have been removed from FAA Knowledge Tests (effective June 12, 2017):

  • 4-panel prog charts
  • Weather depiction chart
  • Area forecasts
  • Aerobatic flight

June 2017 ASA Test Prep Question Updates are now available! Check the link below.

www.asa2fly.com/testupdate

 

 

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CFI Brief: 5 Major Items Pilots Miss During Their Preflight Inspection – InfoGraphic

Today on the Learn to Fly Blog we are featuring a guest article by Alec Larson of Sun State Aviation. Thanks for the excellent article, Alec, and for all the hard work that went into producing this this!

Perhaps the most critical part of any general aviation flight is the preflight inspection of the aircraft. For most pilots, the preflight inspection follows a checklist along with a routine flow around the aircraft. Most pilots and student pilots perform what would be considered a sufficient inspection, following their checklist and routine items.

Surely 100% of pilots would be able to find discrepancies if they were present right?

Sunstate 1

Well………not exactly. Sit down, strap yourself in and get ready to read some interesting real-life statistics!

Every year at the Sun N Fun airshow the FAA partners with a local flight school to host the Project Preflight event. The purpose of the event is to test the preflight efficiency of pilots and student pilots of all ages, hours and experience. A flight school volunteers one of their airplanes for the event.

Participants are invited to preflight the aircraft like they would before any other flight – checking the fuel, oil, tire pressure and anything with blue tape is unnecessary. The catch is, the aircraft has several intentional discrepancies, some are major squawks! This year we hosted the event and gathered the data from 144 total participants.

Here are the results………

Water Bottle Lodged Behind Rudder Pedals – Out of 144 participants only 30% found this major discrepancy.

Cotter Pin Missing In Right WheelOnly 28% found this one!

Elevator Nut Missing – 39% found the nut to missing from the right side of the elevator.

Rag Behind The Alternator – Easy to spot but only 63% of participants found the rag!

Cotter Pin In Control Lock – Only 42% found a small cotter pin in place of the control lock, hard to miss but deadly if left in.

Sunstate 2

Interesting right?! The statistics are concerning to say the least, but what a great insight into a previously unknown sector of general aviation that can be used to educate pilots and future pilots.

So how can we improve these statistics?

Yes, of course we can say “pilots need to be more thorough in their inspections” or “we need to apply more focus and attention to detail during a preflight” but what are some other realistic strategies we can implement to actually achieve that?! Here’s one – maybe it’s extreme and definitely hypothetical but it’s worth pondering.

“Try to preflight the airplane as if you had just built it part by part, or just finished working on it yourself”. 

Again, hypothetical but let’s break it down. We need pilots to perform thorough inspections, how can you put yourself in that “attentive” frame of mind? If you’ve ever rotated the tires on your vehicle yourself, isn’t it likely that you’ll double check and triple check the tightness of the lug nuts before you call it a job done? The theory is that you’ll be taking more responsibility for the state of the aircraft rather than assuming the mechanic or previous pilot left the aircraft in an airworthy condition. This doesn’t mean you should become an aircraft mechanic or add an hour to your preflight, the goal is to find a way to improve our attention and focus when preflighting an airplane.

Project Preflight was certainly educational and we had an absolute blast hosting the event. On behalf of SunState Aviation we would like to thank all of the 144 participants for stopping by and giving us your time, without you this educational piece and the safety of future pilots would not be a reality!

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CFI Brief: FAA Taxi Test

Monday on the blog we briefly discussed runway incursions and recommended practices for pilots to avoid such an occurrence. As air traffic grows and airports become busier, both general aviation and commercial, runway incursions become more of a growing concern to pilots and airport operators. In an effort to cut down on the potential of surface movement issues the FAA has implemented programs such as defining runway hotspots and identifying standardized taxi route.

Runway Hotspots
ICAO defines runway hotspots as a location on an aerodrome movement area with a history or potential risk of collision or runway incursion and where heightened attention by pilots and drivers is necessary. Hotspots alert pilots to complex or potentially confusing taxiway geometry that could make surface navigation challenging. Whatever the reason, pilots need to be aware that these hazardous intersections exist, and they should be increasingly vigilant when approaching and taxiing through these intersections. These hotspots are depicted on some airport charts as circled areas. [Figure 1-6] The FAA Office of Runway Safety has links to the FAA regions that maintain a complete list of airports with runway hotspots at http://www.faa.gov/airports/runway_safety/.

Hot Spots

Standardized Taxi Routes
Standard taxi routes improve ground management at high-density airports, namely those that have airline service. At these airports, typical taxiway traffic patterns used to move aircraft between gate and runway are laid out and coded. The ATC specialist (ATCS) can reduce radio communication time and eliminate taxi instruction misinterpretation by simply clearing the pilot to taxi via a specific, named route. An example of this would be Los Angeles International Airport (KLAX), where North Route is used to transition to Runway 24L. [Figure 1-7] These routes are issued by ground control, and if unable to comply, pilots must advise ground control on initial contact. If for any reason the pilot becomes uncertain as to the correct taxi route, a request should be made for progressive taxi instructions. These step-by-step routing directions are also issued if the controller deems it necessary due to traffic, closed taxiways, airport construction, etc. It is the pilot’s responsibility to know if a particular airport has preplanned taxi routes, to be familiar with them, and to have the taxi descriptions in their possession. Specific information about airports that use coded taxiway routes is included in the Notices to Airmen Publication (NTAP).

Standardized Taxi Routes
The best way you as a pilot can prevent a runway incursions is by being familiar with your surroundings and understanding the airport environment and standardized procedures that are in place. The FAA Safety Team has put together an excellent video and taxi test that will test your knowledge of procedures and operations on the airport movement area. I encourage you to spend 60 minutes and take the course.

The FAA Taxi Test

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CFI Brief: Calling all Student Pilots!

Share your flying story with the Learn to Fly Blog

We’re looking for student pilot stories dealing with overcoming challenges, lessons-learned, or insights-gained, humorous or serious. If selected, your story will be published on the Learn to Fly Blog! This is an ongoing call for submissions and there’s no deadline. Once selected your story will be professionally edited and published this summer to the Learn to Fly Blog for all your family, friends, and future employers to see!

Send you story (minimum 500 words) as a .doc or .rtf file to cfi@asa2fly.com

Include your name, school, current number of hours, and a short bio (optional).

 

home-office-599475_960_720

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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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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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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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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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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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CFI Brief: Atmospheric Stability

Today we will take Monday’s post on temperature inversions a step further  with a discussion on atmospheric stability and the types of weather we can expect with a stable and unstable air mass.

Atmospheric stability is defined as the resistance of the atmosphere to vertical motion. A stable atmosphere resists an upward or downward movement. An unstable atmosphere allows an upward or downward disturbance to grow into a vertical (convective) current.

Determining the stability of the atmosphere requires measuring the difference between the actual existing (ambient) temperature lapse rate of a given parcel of air and the dry adiabatic rate (a constant 3°C per 1,000 feet lapse rate).

A stable layer of air would be associated with a temperature inversion. Warming from below, on the other hand, would decrease the stability of an air mass.

The conditions and characteristic of stable or unstable air masses are shown in the figure below.
Air Masses

Like most things in life their are benefits and drawbacks to both atmospheric conditions. While the visibility may be excellent in an unstable air mass you are likely to encounter turbulent conditions and possibly wind shear. In a stable air mass because the air is stagnant (or lack of vertical motion) you will have a much smoother ride however visibility could be decreased due to hazy conditions.

Take a look at some of these sample FAA knowledge test questions and see if you can answer them. The AC 00-6B is a great additional reference to help with your knowledge on atmospheric stability.

1. What type weather can one expect from moist, unstable air, and very warm surface temperatures?
A—Fog and low stratus clouds.
B—Continuous heavy precipitation.
C—Strong updrafts and cumulonimbus clouds.

2. What are the characteristics of stable air?
A—Good visibility; steady precipitation; stratus clouds.
B—Poor visibility; steady precipitation; stratus clouds.
C—Poor visibility; intermittent precipitation; cumulus clouds.

3. A moist, unstable air mass is characterized by
A—poor visibility and smooth air.
B—cumuliform clouds and showery precipitation.
C—stratiform clouds and continuous precipitation.

4. Which is a characteristic typical of a stable air mass?
A—Cumuliform clouds.
B—Showery precipitation.
C—Continuous precipitation.

Answers will be posted in the comments section.

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