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.

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CFI Brief: Updates to ACS and NEW Testing Supplements

This week, the FAA released updated Airman Certification Standards (ACS) for Private Pilot-Airplane, Instrument Rating-Airplane, and Commercial Pilot Airplane. The Airman Testing Branch will be hosting a webinar next week, June 6th to discuss the updates that are taking place. Webinar information is as follows:

June 6, 2018, at 1430 Central Time, to attend follow the below link.

Private Pilot- Airplane (FAA-S-ACS-6B)
Instrument Rating- Airplane (FAA-S-ACS-8B)
Commercial Pilot- Airplane (FAA-S-ACS-7A)
Remote Pilot- sUAS (FAA-S-ACS-10A)

In addition to the updated Airman Certification Standards, the FAA has also released four new Knowledge Testing Supplements that will go into effect at all testing centers on June 11th. Until then, current testing supplements are in effect. If you plan on taking a knowledge test for one of the below certificates or ratings on or after June 11th, you will want to become familiar with these new supplements.

  • Airman Knowledge Testing Supplement for Sport Pilot, Recreational Pilot, Remote Pilot, and Private Pilot (FAA-CT-8080-2H).
  • Airman Knowledge Testing Supplement for Commercial Pilot (FAA-CT-8080-1E).
  • Airman Knowledge Testing Supplement for Flight Instructor, Ground Instructor, and Sport Pilot Instructor (FAA-CT-8080-5H).
  • Airman Knowledge Testing Supplement for Aviation Maintenance Technician – General, Airframe, and Powerplant; and Parachute Rigger (FAA-CT-8080-4G).

Stay tuned for the June Test Roll, and updates to the knowledge test question databases coming soon.



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CFI Brief: Mach Number

As you progress through a career in aviation you will hopefully one day start flying high speed jet aircraft, a fun and challenging learning experience. However there are many differences when moving from low-speed flight to high-speed flight. Today we will briefly touch on some of the required knowledge associated with high speed flight beginning with mach numbers.

Mach number is the ratio of the true airspeed to the speed of sound (TAS ÷ Speed of Sound). For example, an aircraft cruising at Mach .80 is flying at 80% of the speed of sound. The speed of sound is Mach 1.0. When in high-speed flight we refer to our airspeed in mach rather than true airspeeds or indicated airspeeds. At any airspeeds above Mach 1 you would be breaking the sound barrier.

A large increase in drag occurs when the air flow around the aircraft exceeds the speed of sound (Mach 1.0). Because lift is generated by accelerating air across the upper surface of the wing, local air flow velocities will reach sonic speeds while the aircraft Mach number is still considerably below the speed of sound. With respect to Mach cruise control, flight speeds can be divided into three regimes—subsonic, transonic and supersonic. The subsonic regime can be considered to occur at aircraft Mach numbers where all the local air flow is less than the speed of sound. The transonic range is where some but not all the local air flow velocities are Mach 1.0 or above. In supersonic flight, all the air flow around the aircraft exceeds Mach 1.0. The exact Mach numbers will vary with each aircraft type but as a very rough rule of thumb the subsonic regime occurs below Mach .75, the transonic regime between Mach .75 and Mach 1.20, and the supersonic regime over Mach 1.20.

A limiting speed for a subsonic transport aircraft is its critical Mach number (MCRIT). That is the speed at which airflow over the wing first reaches, but does not exceed, the speed of sound. At MCRIT there may be sonic but no supersonic flow.

When an airplane exceeds its critical Mach number, a shock wave forms on the wing surface that can cause a phenomenon known as shock stall. If this shock stall occurs symmetrically at the wing roots, the loss of lift and loss of downwash on the tail will cause the aircraft to pitch down or “tuck under.” This tendency is further aggravated in sweptwing aircraft because the center of pressure moves aft as the wing roots shock stall. If the wing tips of a sweptwing airplane shock stall first, the wing’s center of pressure would move inward and forward causing a pitch up motion. See the Figure below.

The less airflow is accelerated across the wing, the higher the critical Mach number (i.e., the maximum flow velocity is closer to the aircraft’s Mach number). Two ways of increasing MCRIT in jet transport designs are to give the wing a lower camber and increase wing sweep. A thin airfoil section (lower camber) causes less airflow acceleration. The sweptwing design has the effect of creating a thin airfoil section by inducing a spanwise flow, thus increasing the effective chord length. See the Figure below.

Although a sweptwing design gives an airplane a higher critical Mach number (and therefore a higher maximum cruise speed), it results in some undesirable flight characteristics. One of these is a reduced maximum coefficient of lift. This requires that sweptwing airplanes extensively employ high lift devices, such as slats and slotted flaps, to get acceptably low takeoff and landing speeds. The purpose of high lift devices such as flaps, slats and slots is to increase lift at low airspeeds and to delay stall to a higher angle of attack.

Another disadvantage of the sweptwing design is the tendency, at low airspeeds, for the wing tips to stall first. This results in loss of aileron control early in the stall, and in very little aerodynamic buffet on the tail surfaces.


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CFI Brief: Complex Airplane, No Longer Required on Checkride

The Federal Aviation Administration has issued a Notice of Change to National Policy regarding use of complex airplanes during Commercial Pilot (Single-Engine Land) or Flight Instructor checkrides. A complex airplane is defined as an airplane with flaps, retractable landing gear, and a constant speed propeller. This change in policy will no longer require the use of a complex airplane on the above named practical tests. Notice 8900.463 reads in part:

This notice outlines a change in policy regarding testing applicants for a commercial pilot or flight instructor certificate, regardless whether the training was received under Title 14 of the Code of Federal Regulations (14 CFR) part 61 or 141. Specifically, it outlines the policy which no longer requires applicants for a commercial pilot certificate with an airplane single-engine rating to provide a complex or turbine-powered airplane for the associated practical test and no longer requires applicants for a flight instructor certificate with an airplane single-engine rating to provide a complex airplane for the practical test.

It is important to note this policy change does not affect the training and experience requirements as outlined in 14 CFR Parts 61 or 141. Applicants working towards a Commercial or Flight Instructor Certificate will still be required to obtain flight time and training in a complex airplane.

Part of the reasoning behind this change is that training providers have noted a concern regarding the availability of complex airplanes, adding to the complexity of scheduling checkrides. In addition, many of these aircraft are older models and require much higher maintenance cost to meet airworthiness standards. The FAA recognizes these flight school concerns and understands it might be cost-prohibitive and difficult to schedule applicant testing in a complex airplane.

Removing the requirements for a complex airplane to be used during the practical test will in turn reduce the overall cost of the practical test and allow applicants to utilize more cost effective and readily available aircraft.

Please note the corresponding changes to the Commercial Pilot ACS (FAA-S-ACS-7) and Flight Instructor PTS (FAA-S-8081-6D) as outlined below.

Change 3

  • Revised the “Equipment Requirements & Limitations” section in Appendix 7: Aircraft, Equipment, and Operational Requirements & Limitations.

Note: This change will also affect the wording in some of the Task, Skill elements. To see all change 3 revisions please refer to the complete document by following the link below. 

Change 6

  • Removed the complex airplane requirement from practical tests for an airplane single-engine instructor rating and made corresponding changes to Task elements and the following sections in the Introduction:
  • “Aircraft and Equipment Required for the Practical Test”
  • “Renewal or Reinstatement of a Flight Instructor Certificate”

An update will be available shortly for the ASA Commercial Pilot ACS and Flight Instructor PTS publications. To stay informed of all updates please follow the link below.

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CFI Brief: sUAS Maintenance & Inspection

In addition to preflight and postflight considerations for small unmanned aircraft systems (sUAS) which was disused in Monday’s post, special attention should be placed on maintenance and inspection procedures. Unlike an airplane or helicopter, a sUAS does not require an airworthiness certificate nor is it required to have maintenance inspections done at certain intervals. It is the responsibility of the pilot in command to determine that the sUAS has been maintained in a condition for safe operation.

Maintenance for sUAS includes scheduled and unscheduled overhaul, repair, inspection, modification, replacement, and system software upgrades for the unmanned aircraft itself and all components necessary for flight.

Manufacturers may recommend a maintenance or replacement schedule for the unmanned aircraft and system components based on time-in-service limits and other factors. Follow all manufacturer maintenance recommendations to achieve the longest and safest service life of the sUAS. If the sUAS or component manufacturer does not provide scheduled maintenance instructions, it is recommended that you establish your own scheduled maintenance protocol. For example:

  • Document any repair, modification, overhaul, or replacement of a system component resulting from normal flight operations.
  • Record the time-in-service for that component at the time of the maintenance procedure.
  • Assess these records over time to establish a reliable maintenance schedule for the sUAS and its components.

During the course of a preflight inspection, you may discover that an sUAS component requires some form of maintenance outside of the scheduled maintenance period. For example, an sUAS component may require servicing (such as lubrication), repair, modification, overhaul, or replacement as a result of normal or abnormal flight operations. Or, the sUAS manufacturer or component manufacturer may require an unscheduled system software update to correct a problem. In the event such a condition is found, do not conduct flight operations until the discrepancy is corrected.

In some instances, the sUAS or component manufacturer may require certain maintenance tasks be performed by the manufacturer or by a person or facility specified by the manufacturer; maintenance should be performed in accordance with the manufacturer’s instructions. However, if you decide not to use the manufacturer or the personnel recommended by the manufacturer and you are unable to perform the required maintenance yourself, you should:

  • Solicit the expertise of maintenance personnel familiar with the specific sUAS and its components.
  • Consider using certificated maintenance providers, such as repair stations, holders of mechanic and repairman certificates, and persons working under the supervision of a mechanic or repairman.

If you or the maintenance personnel are unable to repair, modify, or overhaul an sUAS or component back to its safe operational specification, then it is advisable to replace the sUAS or component with one that is in a condition for safe operation. Complete all required maintenance before each flight—preferably in accordance with the manufacturer’s instructions or, in lieu of that, within known industry best practices.

Careful recordkeeping can be highly beneficial for sUAS owners and operators. For example, recordkeeping provides essential safety support for commercial operators who may experience rapidly accumulated flight operational hours/cycles. Consider maintaining a hardcopy and/or electronic logbook of all periodic inspections, maintenance, preventative maintenance, repairs, and alterations performed on the sUAS. See the figure below. Such records should include all components of the sUAS, including the:

  • Small unmanned aircraft itself;
  • Control station;
  • Launch and recovery equipment;
  • Data link equipment;
  • Payload; and
  • Any other components required to safely operate the sUAS.

You can find a UAS Operators Log here.

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CFI Brief: Pop Quiz—Clouds

If you are reading today’s blog then you have already committed yourself to this mandatory 5-question pop quiz. Too late, you can’t leave now! Plus, who doesn’t love a good pop quiz to test your level of aviation meteorology knowledge. Meteorology you say? That’s right todays pop quiz is on clouds, so I hope you read Monday’s blog post, if not go back and give it a quick read thru by following the below link.

Blog Post – Weather: Clouds

Before you jump right into the quiz let’s highlight some knowledge pertaining to clouds you should know.

  • Stability determines which of two types of clouds will be formed: cumuliform or stratiform.
  • Cumuliform clouds are the billowy-type clouds having considerable vertical development, which enhances the growth rate of precipitation. They are formed in unstable conditions, and they produce showery precipitation made up of large water droplets.
  • Stratiform clouds are the flat, more evenly based clouds formed in stable conditions. They produce steady, continuous light rain and drizzle made up of much smaller raindrops.
  • Steady precipitation (in contrast to showery) preceding a front is an indication of stratiform clouds with little or no turbulence.
  • Clouds are divided into four families according to their height range: low, middle, high, and clouds with extensive vertical development.
  • The first three families—low, middle, and high—are further classified according to the way they are formed. Clouds formed by vertical currents (unstable) are cumulus (heap) and are billowy in appearance. Clouds formed by the cooling of a stable layer are stratus (layered) and are flat and sheet-like in appearance. A further classification is the prefix “nimbo-” or suffix “-nimbus,” which means raincloud.
  • High clouds, called cirrus, are composed mainly of ice crystals; therefore, they are least likely to contribute to structural icing (since it requires water droplets).

Ready, set, pop quiz!

Pop Quiz – Weather, Clouds

1. Clouds, fog, or dew will always form when
A—water vapor condenses.
B—water vapor is present.
C—relative humidity reaches 100 percent.

2. If an unstable air mass is forced upward, what type clouds can be expected?
A—Stratus clouds with little vertical development.
B—Stratus clouds with considerable associated turbulence.
C—Clouds with considerable vertical development and associated turbulence.

3. The suffix ‘nimbus,’ used in naming clouds, means
A—a cloud with extensive vertical development.
B—a rain cloud.
C—a middle cloud containing ice pellets.

4. Clouds are divided into four families according to their
A—outward shape.
B—height range.

5. What clouds have the greatest turbulence?
A—Towering cumulus.

So, how do you think you did? Check out the Answers & Explanations.

Note, the question above are sample questions representative to what you might see on your FAA Private Pilot Knowledge Exam. 

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CFI Brief: Airport Hot Spot

Ever heard of an airport hot spot, or wondered what that is? No, it’s not a scorching hot section of an airport, it’s more along the lines of the cool hip place to be at an airport. A hot spot is defined as a location on an airport movement area with a history of potential risk of collision or runway incursion, and where heightened attention by pilots and drivers is necessary.

These hot spot areas on the airport are found to be particularly complex and/or confusing and often times heavy traffic areas. Many times accidents, incidents, or runway incursions have been known to occur in these areas. The Chart Supplement U.S. will list a textual description of hot spots and a graphical depiction is shown on the Airport Diagram. Below is an example of a hot spot area for SUX airport labeled as HS-1. You can see that due to the crossing runways and taxiways this area could be rather confusing to a pilot not familiar with the airport.

By identifying hot spots, airport operators and air traffic controllers are able to plan for the safest possible movement of aircraft and vehicles operating on the movement area. As a pilot try to pre-plan your expected route to/from the runway and have a good idea of where your final destination is ahead of time and be aware of any hot spot areas which you might encounter. By making sure that aircraft surface movements are planned and properly coordinated with air traffic control, pilots add another layer of safety to their flight preparations.

Remember, the ultimate goal of hot spots is to prevent a ground based or runway incursion.

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CFI Brief: Airport Signage

Airport signage is an extremely important concept that all pilots will need to have a thorough understanding of prior to earning any  pilot certificate, whether it’s Private Pilot, Sport Pilot, or even a Remote Pilot Certificate.

Right of the bat you should take note that as an airport layout grows in complexity so will the signage associated with that airport. For example an airport with multiple runways will consist of a lot more signage then say an airport with one small runway. The reason being is more runways will require more taxiways and the greater likelihood for a runway or ground based incursion to occur. A pilot will need to pay a lot more attention at signage when operating at complex airports. In addition you will often see different types of signage at a Part 139 airport conducting commercial operations then you might at a small rural airport with no commercial operations.

There are six types of signs that may be found at airports.

Mandatory instruction signs—red background with white inscription. These signs denote an entrance to a runway, critical area, or prohibited area.

Location signs—black with yellow inscription and a yellow border, no arrows. They are used to identify a taxiway or runway location, to identify the boundary of the runway, or identify an instrument landing system (ILS) critical area.

Direction signs—yellow background with black inscription. The inscription identifies the designation of the intersecting taxiway(s) leading out of an intersection.

Destination signs—yellow background with black inscription and arrows. These signs provide information on locating areas, such as runways, terminals, cargo areas, and civil aviation areas.

Information signs—yellow background with black inscription. These signs are used to provide the pilot with information on areas that cannot be seen from the control tower, applicable radio frequencies, and noise abatement procedures. The airport operator determines the need, size, and location of these signs.

Runway distance remaining signs—black background with white numbers. The numbers indicate the distance of the remaining runway in thousands of feet.

The image below are further examples along with their action or purpose of the six types of airport signage discussed above. For further information on airport signage you can refer to the Aeronautical Information Manual (AIM) 2-3-7 or the Pilots Handbook of Aeronautical Knowledge, Chapter 14 Airport Operations.

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CFI Brief: February 2018 Test Roll

The FAA February test cycle resulted in few changes or updates to the FAA Airman Knowledge Tests. The FAA Aviation Exam Board continues to work to align questions within the context of a specific Area of Operation/Task as outlined in the various Airman Certification Standards publications. The goal of this boarding process is to ensure all test questions correlate to a knowledge, risk management or skill element. The FAA makes their intentions clear by the Frequently Asked Questions and What’s New documents which are posted each test cycle. The next test cycle update is expected June 11th 2018.

Below is a list of the most recent changes affecting all pilot knowledge test question banks.

  • 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.
  • New questions based on FAA Form 7233-4, International Flight Plan (ICAO format)— release date is TBD.
  • Student Pilot/Medical Certificate – New questions based on the Student Pilot Certificate rule that took effect on April 1, 2016 are being developed. We expect to add these questions to appropriate knowledge tests by June 11, 2018.

Instrument Rating Airplane (IRA), Airline Transport Pilot Multi-Engine (ATM), Aircraft Dispatcher (ADX)  – All VOR/DME RNAV questions have been removed from the question banks for these knowledge tests.

These changes have been noted by ASA and updates for Prepware Software, Prepware Online, and Test Prep books will be available shortly. If you would like to be notified when these updates have become available be sure to follow the link below and sign-up for notifications.


Handbook and Advisory Circular Updates

New and cool from ASA!

 The Complete Remote Pilot – Available NOW

The Droner’s Manual – Available NOW

The Flight Instructors Manual – NEW Sixth Edition

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CFI Brief: Aviation Weather Services (AC 00-45H) – UPDATE

The FAA has issued a Change 1 to Advisory Circular AC 00-45H effective January 8th 2018. AC 00-45, more commonly referred as Aviation Weather Services, is the go-to resource for U.S. aviation weather products and services. This document is organized using the FAA’s three distinct types of aviation weather information: observations, analyses, and forecasts. This is a vital resource and should be a part of any aviators library.

Here are some of the highlights on what you need to know regarding Change 1:

  • DUATS II no longer requires an airman medical to access the system (
  • A new section was added to Chapter 3, Terminal Doppler Weather Radar (TDWR). The TDWR network is a Doppler weather radar system operated by the FAA, which is used primarily for the detection of hazardous windshear conditions, precipitation, and winds aloft on and near major airports situated in climates with great exposure to thunderstorms in the United States. To review this information refer to Section 3.4.
  • A new sub-section was added to Chapter 3, POES. POES stands for the Polar Orbiting Environment Satellites, although more recently the U.S. polar satellite program has been rechristened the Joint Polar Satellite System (JPSS). Polar satellites are not stationary. They track along various orbits around the poles. Typically, they are somewhere between 124 and 1,240 mi above the Earth’s surface. The satellites scan the Earth in swaths as they pass by on their tracks. To review this information refer to Section 3.5.3.
  • Note in chapter 5 section 6 that Collaborative Convective Forecast Planning (CCFP) is now Convective Forecast (TCF). The figures and language throughout this section have been updated to reflect this updated weather product. To review this information refer to Section 5.6.3.
  • A new section was added to Chapter 5, Graphical Forecasts for Aviation (GFA). The GFAs are a set of Web-based displays which are expected to provide the necessary aviation weather information to give users a complete picture of the weather that may impact flights in the CONUS. These displays are updated continuously and provide forecasts, observational data, and warnings of weather phenomena that can be viewed from 14 hours in the past to 15 hours in the future. This product covers the surface up to FL420 (or 42,000 ft MSL). Wind, icing, and turbulence forecasts are available in 3,000-ft increments from the surface up to 18,000 ft MSL, and in 6,000-ft increments from 18,000 ft MSL to FL420. Turbulence forecasts are also broken into low (below 18,000 ft MSL) and high (above 18,000 ft MSL) graphics. A maximum icing graphic and maximum wind velocity graphic (regardless of altitude) are also available. The graphic below is an example of an aviation forecast for clouds. To review this information refer to Section 5.9.
  • A new section was added to Chapter 5, Localized Aviation Model Output Statistics (MOS) Program (LAMP). The LAMP weather product is a statistical model program that provides specific point forecast guidance on sensible weather elements (perceivable elements such as temperature, wind, sky cover, etc.). LAMP weather product forecasts are provided in both graphical and coded text format, and are currently generated for more than 1,500 locations. The LAMP weather product is entirely automated and may not be as accurate as a forecast generated with human involvement. However, information from the LAMP weather product can be used in combination with Terminal Aerodrome Forecasts (TAF), and other weather reporting and forecasting products and tools, to provide additional information and enhance situational awareness regarding a particular location. To review this information refer to Section 5.10.  
  • Hawaii was added to Section 5.11.1 as an area of issuance for an Area Forecast (FA). You will find new figures and detailed information regarding the Hawaii Area Forecast. To review this information refer to Section 5.11.1.
  • A new sub-section was added to Chapter 5, Low-Level Wind Shear Alert System (LLWAS). The LLWAS system was originally developed by the FAA in the 1970s to detect large-scale wind shifts (sea breeze fronts, gust fronts, and cold and warm fronts). It was developed by the FAA in response to an accident at JFK Airport in New York. The aircraft (Eastern 66) landed during a wind shift caused by interacting sea breeze and thunderstorm outflows. To review this information refer to Section

ASA will have an Change 1 update available shortly to go along with all printed copies of the Aviation Weather Handbook (ASA-AC00-45H). The update will be posted on the Textbooks Update page at

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CFI Brief: Icing

Ice sucks, unless of course you are a hockey player, figure skater, or just want a nice, cold, tasty beverage. But in terms of aviation, ice sucks. In general, icing is any deposit of ice forming on an object. In aviation icing is considered to be one of the major weather hazards affecting flight. We refer to icing as a cumulative hazard, meaning the longer an aircraft collects structural icing the worse the hazard will become. Structural icing is the stuff that sticks to the outside of the airplane, it occurs whenever supercooled condensed droplets of water make contact with any part of the airframe that is also at a temperature below freezing. An inflight condition necessary for structural icing to form is visible moisture (clouds or raindrops). Structural icing is categorized into three types: Rime, Clear, and Mixed.

Rime Ice

Rime ice is rough, milky, and opaque ice formed by the instantaneous freezing of small, supercooled water droplets after they strike the aircraft. It is the most frequently reported icing type. Rime ice can pose a hazard because its jagged texture can disrupt an aircraft’s aerodynamic integrity.

Rime icing formation favors colder temperatures, lower liquid water content, and small droplets. It grows when droplets rapidly freeze upon striking an aircraft. The rapid freezing traps air and forms a porous, brittle, opaque, and milky-colored ice. Rime ice grows into the air stream from the forward edges of wings and other exposed parts of the airframe.

Clear Ice

Clear ice (or glaze ice) is a glossy, clear, or translucent ice formed by therelatively slow freezing of large, supercooled water droplets. Clear icing conditions exist more often in an environment with warmer temperatures, higher liquid water contents, and larger droplets.

Clear ice forms when only a small portion of the drop freezes immediately while the remaining unfrozen portion flows or smears over the aircraft surface and gradually freezes. Few air bubbles are trapped during this gradual process. Thus, clear ice is less opaque and denser than rime ice. It can appear either as a thin smooth surface, or as rivulets, streaks, or bumps on the aircraft.

Clear icing is a more hazardous ice type for many reasons. It tends to form horns near the top and bottom of the airfoils leading edge, which greatly affects airflow. This results in an area of disrupted and turbulent airflow that is considerably larger than that caused by rime ice. Since it is clear and difficult to see, the pilot may not be able to quickly recognize that it is occurring. It can be difficult to remove since it can spread beyond the deicing or anti-icing equipment, although in most cases it is removed nearly completely by deicing devices.

Mixed Ice

Mixed ice is a mixture of clear ice and rime ice. It forms as an airplane collects both rime and clear ice due to small-scale (tens of kilometers or less) variations in liquid water content, temperature, and droplet sizes. Mixed ice appears as layers of relatively clear and opaque ice when examined from the side.

Mixed icing poses a similar hazard to an aircraft as clear ice. It may form horns or other shapes that disrupt airflow and cause handling and performance problems. It can spread over more of the airframe’s surface and is more difficult to remove than rime ice. It can also spread over a portion of airfoil not protected by anti-icing or deicing equipment. Ice forming farther aft causes flow separation and turbulence over a large area of the airfoil, which decreases the ability of the airfoil to keep the aircraft in flight.


Effects of Icing

Remember when I said a few paragraphs earlier that ice sucks? Well I didn’t really explain myself as to why.

When structural icing forms, it reduces aircraft efficiency by increasing weight, reducing lift, decreasing thrust, and increasing drag. Each effect will either slow the aircraft or force it downward.  As ice accumulates the performance characteristics of the aircraft will continually deteriorate eventually to a point where the aircraft can no longer maintain sustained flight and stalls.  The image below is a good depiction of this.

As ice forms on an airfoil, it will destroy the smooth flow of air over the surface of the wing resulting in drag and diminishing the maximum lift capable of the wing. NASA wind tunnel testing has shown that icing on the leading edge or upper surface of a wing no thicker then coarse sandpaper can reduce lift by 30 percent and increase drag by 40 percent.

In addition icing can also cause instrumentation errors, frozen or unbalanced control surfaces, engine failures and/or structural damage due to chunks of ice breaking off.

Additional Knowledge to Know

  • Icing in precipitation (rain) is of concern to the VFR pilot because it can occur outside of clouds.
  • Aircraft structural ice will most likely have the highest accumulation in freezing rain which indicates warmer temperature at a higher altitude.
  • The presence of ice pellets at the surface is evidence that there is freezing rain at a higher altitude, while wet snow indicates that the temperature at your altitude is above freezing.
  • A situation conducive to any icing would be flying in the vicinity of a front.



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