Are service documents mandatory? No. Are they a good idea to implement? It depends, but for the most part, yes, and you’ll soon discover why.

Corrosion comes in all shapes and sizes. It is a natural process in which metals deteriorate due to chemical reactions with environmental elements, such as oxygen, moisture, and pollutants. In aviation, corrosion can manifest in various forms, including surface, pitting, intergranular, and stress corrosion cracking.

Each type poses significant risks, potentially weakening the structural integrity of the aircraft and leading to safety hazards. We’ve recently seen how corrosion affects wing spars like with the Piper PA-28 and Cessna 177 and 210, for example. These started as Service Bulletins (SBs) to inspect for corrosion and escalated to mandatory compliance in the form of Airworthiness Directives (ADs).

• READ MORE: How Do I File a Pilot Weather Report Online?

The implications are severe. Corrosion can lead to structural failures, increased maintenance costs, and, in worst-case scenarios, catastrophic accidents. Once you have the basics and understand the theory, you are ready to progress to the next level.

That’s right, it’s aircraft maintenance time, and here’s one example.

Learjet 45

The Learjet is legendary among corporate aircraft—produced from 1964 to its unfortunate scuttling in 2021. Learjet became synonymous with business aircraft in the early days of private business travel.

“Learjet models are known for their exceptional performance, speed, and range,” said Sky Aircraft Maintenance. “Airframe issues can be a common maintenance concern for Learjet aircraft. Due to the high speeds and stresses placed on the airframe during flight, wear and tear can occur over time, leading to a need for structural repairs. This can include corrosion.”

On July 13, 2007, the Australian Civil Aviation Authority released AWB 57-004 Lear Jet Industries 45 Wing Corrosion. The agency said this correspondence was needed because “recent reports have been submitted indicating that corrosion has been found on the lower skin of both wings fitted to the Lear 45 aircraft. This corrosion resulted in the replacement of the entire lower-wing skins.”

Years later, in February 2019, Learjet, now owned by Bombardier, released a series of Service Bulletins addressing “wing spar inspection.” The reason? Corrosion had been observed on the lower-wing splice plates, requiring a more frequent interval to detect and correct protective coatings.

Remember our chat earlier about adhering to the manufacturer’s recommendations? 

• READ MORE: What Does It Take to Transition From a Jet to a Piston Airplane?

Fast-forward a bit and the series of Learjet bulletins are now the FAA’s AD 2021-23-08.

What prompted this escalation? According to the AD, exfoliating corrosion was found on a particular Lear 45 upper surface of the lower center-wing, midspar splice plate during unrelated maintenance. The corrosion appeared to extend halfway through the thickness of the splice plate. Since the initial report, the FAA has received 23 additional accounts of corrosion from Learjet.

Jerel Bristol, owner of SEAL Aviation in Hollywood, Florida, was not surprised when the call came in. Bristol is aware of the trouble that Learjets have with wing-spar corrosion and knows the AD well. His team deploys to aircraft or ​AOG situations for mobile fuel leak repair, nondestructive testing, and structural repairs anywhere in the world.

During the center-wing inspection, a SEAL technician identified corrosion on the center-wing splice plate. I spoke with Bristol, and he said that it is a common area to find corrosion past repairable limits, which requires the replacement of the forward and aft splice plates.

After pulling the affected parts off the airframe, the SEAL team quickly repaired the area and replaced the damaged parts. The pictures reveal a sea of cleco fasteners. 

The guys buttoned up the Lear, and the owner was wheels-up again. 

The Cause

The big question remains: What causes corrosion?

One follower commented on a SEAL Aviation webpage post about the Lear 45 repair, stating that brine used for deicing could have contributed to the corrosion. He is not far off. Environmental elements can contribute to aircraft corrosion.

These factors include:

• Humidity and moisture, particularly in coastal regions.

• Temperature fluctuations which can cause condensation.

• Exposure to deicing fluids and other chemicals.

• Poor maintenance practices and infrequent inspections.

The environment is not the only player in the corrosion game. According to Aviation Devices and Electronic Components (Av-DEC) in its article “Causes of Corrosion,” industrial pollutants are equally harmful and can be difficult to protect against.

These include several contaminants such as:

• Ozone (exposure from high altitude, motors, and welding)

• Carbon compounds (exposure from combustion engine exhaust)

• Sulfur dioxide (exposure from engine exhaust, smokestacks, and acid rain)

Operators and GA aircraft owners alike are well advised to take heed when an SB shows up in the mailbox. A recommended inspection, especially when it can be coordinated with other scheduled or unscheduled maintenance, may help ultimately reduce the total cost of ownership and down time if/when an issue becomes an AD.

Perhaps the best reason to take a closer look is personal safety and peace of mind through identifying a problem before it manifests in something tragic.

This column first appeared in the September Issue 950 of the FLYING print edition.

The post Corrosion 101: What Causes It? appeared first on FLYING Magazine.

Answer: Whether in the form of a METAR or by the ground-to-air radio broadcasts, every pilot uses surface observations to make many routine operational decisions during any particular flight. As we listen to the broadcast prior to taxi, it provides us with an altimeter setting and will likely determine the runway we use for departure.

When approaching an airport under instrument flight rules (IFR), it will help us determine if we’ll be flying a visual approach or need to execute a standard instrument approach procedure. And when Mother Nature is at her worst, it will let us know when we should skip the airport altogether and fly to our alternate destination.

Surface observations are one of those data points that we often take for granted. The truth is that they play a monumental role in many of our most routine decisions. They are not just used by pilots, however, as they also provide air traffic controllers, dispatchers, and weather forecasters with a reasonable depiction of the weather conditions at an airport.

Even with something as ubiquitous as a surface observation, there are some nuances you should understand.

Pilots at all experience levels should be familiar with the two primary automated observing systems deployed at many airports throughout the United States. This includes the Automated Surface Observing System (ASOS) and the Automated Weather Observation System (AWOS). Both of these automated systems consist of a collection of electronic sensors that measure the environment and then process the data to create an observation once every minute.

Sampling the Atmosphere

While many high-impact airports throughout the U.S. still rely on a trained weather observer to construct the routine or special observation (SPECI), automated systems supply them with uniform and objective data for the observation.

However, automated systems measure only the weather that passes directly through the sensor array so it is not able to report what’s happening outside the airport’s runway complex or what is referred to as the airport’s vicinity. Weather observers can certainly augment the observation to add these details.

At airports without a trained observer, pilots must completely rely on the “raw” automated observation. This, however, isn’t as raw as you might think. In order to provide a representative observation, the automated hardware must continuously collect the sensor’s real-time data over a period of time. The automated system applies an algorithm to the collected data to extrapolate the weather to cover a wider area referred to as the terminal area.

When the weather is sampled over a specified period, it will tend to “smooth out” the conditions but also will account for the normal meteorological variations that we see in the weather. Each of the various weather elements shown in the table below identifies the required sample times for its algorithms and provides a summary of where the data are considered valid.

For example, 30 minutes of data provides a fairly reasonable description of sky conditions. This means that the system will detect and process all the clouds (if any) passing over the sensor in the past 30 minutes.

To account for the latest sky conditions, the result is biased by double weighting (counting twice) the last 10 minutes of data. Using the last 30 minutes of data in this way will allow the system to determine the cloud base height and sky coverage included in the surface observation and becomes a reasonable estimate of the sky conditions over a three to 5 sm radius around the location of the sensor (usually sited on the field). 

Beware of Rapidly Changing Weather

Even though an ASOS creates a completely new observation every minute, automated systems must have adequate sensor samples to develop an accurate observation. Therefore, in rapidly changing conditions, pilots should expect that most of the weather elements from the automated observations to trend slightly behind the actual weather.

For example, if skies are clear and a sudden broken sky appears on the sensors, ASOS will take only two minutes to report a scattered deck of clouds even though a trained observer may report a broken sky cover. It will take nearly 10 minutes before the observation system will catch up and indicate a broken cloud layer. 

This may or may not trigger a SPECI (special observation) for an ASOS (most AWOSs cannot report a special observation). It depends on the height of the broken layer. In other words, a sudden broken ceiling at 600 feet has a significant operational impact and will generate a SPECI since the flight category changed from VFR to IFR. But it will take nearly 10 minutes before the SPECI is issued given the discussion above.  

Each minute an ASOS processes the most recent 10 minutes of visibility sensor data to obtain a representative value. Therefore, when visibility drops suddenly (in one minute) from 7 sm to 1 sm, the ASOS needs about four minutes before the 10-minute mean values reach the 3 statute mile criteria. This criterion forces SPECI to alert pilots to a significant change in visibility in this instance. A total of nine minutes will pass before the ASOS will report the 1 sm visibility.

On the other hand, when the visibility rapidly improves from 1 mile to 7 miles, the ASOS generates a SPECI four minutes after reaching the 1.5 sm threshold. In about 11 minutes, the ASOS will report 7 sm. The system is intentionally designed to raise surface visibility more slowly than to lower it.  This design provides a margin of safety and buffers rapid changes when the visibility is widely fluctuating over a short period.

Hourly and special observations are the only ones created by human observers. In contrast, ASOS relentlessly measures the weather and could inundate pilots with more frequent special observations than a human observer when the weather is changing rapidly.

Thus, the system is purposely throttled to only provide SPECIs at no more than a five-minute interval to limit the number of observations that can be transmitted during the hour. An even slower response is seen at controlled airports where only the hourly and special observations must be prepared and broadcast on the Airport Terminal Information System (ATIS). At uncontrolled airports pilots can also receive the one-minute weather by calling the voice phone link or by the ground-to-air radio broadcasts. 

The FAA has created a Google map presentation online showing the locations of all automated weather systems across the country, which may be found here. This includes the frequency and phone numbers for each ASOS and AWOS currently in operation.  

Lockout Period

If you pay attention to the issuance time on METARs, you will notice that many are issued a few minutes before the top of each hour. This allows the observation to be transmitted and ingested into other computer systems such as numerical weather prediction models.

Some models get executed at the top of the hour or shortly thereafter. Starting at 47:20 past the hour, the ASOS begins to make its routine observation. By 53:20, the hourly observation has been prepared and edited and should be ready for transmission.

This period of time between 47:20 and 53:20 minutes after the hour is known as the lockout period. During this time, the ASOS is prevented from issuing any other reports, including SPECIs. The ASOS still continuously monitors and records the weather during the lockout period.

However, it just can’t issue a formal surface observation. This does not affect the one-minute weather you receive by calling the voice phone link or by the ground-to-air radio broadcasts, but it will affect any formal observations that are transmitted that you may see on your datalink weather broadcast.  

Can I Trust Automated Observations?

All observations, whether automated or taken by human observers, should be used with care.

Pilots must be aware of how long ago the observation was taken, under what conditions, and whether or not they are special observations. Even though automated systems are totally objective and maintain a certain uniformity among all sites, it does not mean they match what a pilot sees out the windscreen.

ASOS may occasionally report cloud decks lower than what is actually encountered. Sometimes precipitation, lower cloud fragments, or fog triggers these lower values. Pilots have said that these “lower” reported values often indicated the height below which they had to fly before gaining enough forward visibility to see an airport and land.

The key lesson here is to evaluate all reports closely before dismissing them as inaccurate.

Even though the visibility sensor is designed to objectively represent the visibility of the atmosphere over a wide range of weather conditions, day or night, it occasionally reports a visibility more optimistic than what a human perceives.

During the day, the human eye can be overwhelmed by bright light reflected in clouds, light precipitation, fog, or haze. Many pilots will resort to wearing sunglasses to obtain some relief from the glare.

The ASOS visibility sensor is not as sensitive to this condition and sometimes reports a visibility approximately twice as high as what an individual may determine. Be alert for these bright conditions and expect a more optimistic value from the automated system.

What Will Automation Not Provide?

We can easily become complacent when it comes to automation. We learn to trust automation and sometimes don’t acknowledge that it has real limitations.

 Therefore, to finish this discussion, it is just as important to know what automation will not provide.

Automation systems can only report the weather that passes through the sensor array. They do not provide a horizon-to-horizon evaluation of the weather. This means that weather in the vicinity of the airport will not be measured. A rain shower that passes just to north of the airport, for instance, may reduce visibility in that immediate area but will not be reported by the automated system.

Next, the ASOS only reports clouds that are below 12,000 feet. This means that an overcast cloud deck at 14,000 feet will be reported as clear. Effectively, a clear sky report from an automated station means clear below 12,000 feet.

For airports with a human observer, this report can be augmented to include clouds above 12,000 feet. Some of the new AWOSs being installed can automatically report clouds above 12,000 feet up to and including 30,000 feet.  

Automated systems can only report one precipitation type at a time. For instance, if freezing rain and snow are detected, snow is reported. Certainly, weather observers can edit the observation before transmission to include additional precipitation types. 

Lastly, the ASOS is not designed to report virga, tornadoes, funnel clouds, ice crystals, snow pellets, ice pellets, drizzle, freezing drizzle, and blowing obstructions such as dust or sand. All of these elements can be provided at locations that employ a trained observer. Often with drizzle, freezing drizzle, ice pellets, or a mixture, you will see the automated system report an unknown precipitation type (UP). 

Nevertheless, automated reporting is in its infancy, so it’s likely new sensors will be added to measure some of these other weather elements in the future.

The post Are Surface Observations Based on Instantaneous Measurements? appeared first on FLYING Magazine.

QUESTION: I just noticed something odd about an airplane on the ramp. The right wheel of the Cessna 172 has what looks like a lug nut sticking out of it, and this lug nut is missing from the left wheel. Is there supposed to be another part there? What is the lug for? Is the aircraft still airworthy?

• READ MORE: Why Are Some Military Airplanes Gold?

Answer: For this one we reached out to our cadre of A&P and A&P/IAs. They tell us that the part was probably used to attach wheel pants once upon a time.

There may have been a lug nut on the other wheel that was taken off, or fell off. Wheel pants are not required on Cessna 172 under FAR 91.205, so this is not a grounding issue.

• READ MORE: Does the FAA Punish Pilots for Logbook Mistakes?

The post What Is the Lone Lug Meant for on This Cessna 172? appeared first on FLYING Magazine.

• READ MORE: Why Aren’t Cessna 140s/150s Considered Light Sport Aircraft?

Answer: The biplanes you mention—Stearmans, Kaydets, and Navy SNJs—were mostly likey trainers.

They were yellow because if they went down on a training mission—as they often did—they were easier to spot from the air.

• READ MORE: How Can an Aircraft Get Struck by Lightning Without a Close Thunderstorm?

Often the trainees made unscheduled off-airport landings in hayfields, swamps, forests, and the desert. Having an aircraft painted to look like terrain would have made it more difficult to find them.

The post Why Are Some Military Airplanes Gold? appeared first on FLYING Magazine.

Answer: The LSA rule as it stands limits aircraft to a gross weight of 1,320 pounds for land aircraft.

• READ MORE: Pilots Have Questions When It Comes to MOSAIC

Gross weight is determined when the aircraft is certificated. The Cessna 140 GW is 1,450 pounds, and the Cessna 150 is between 1,500 and 1,600 pounds, depending on the year of manufacture. You can take the other seat out and fly partial fuel, and that will make the aircraft lighter, but it won’t change the certificated gross weight.

Understand that the LSA rule is under review with MOSAIC, and if approved as written, will increase the gross weight of aircraft to 3,600 pounds.

When that transpires, many of the single-engine light trainers flown today in the utility and normal category will likely become LSA compliant.

The post Why Aren’t Cessna 140s/150s Considered Light Sport Aircraft? appeared first on FLYING Magazine.

Answer: There are many observed cases of lightning strikes to aircraft inside or near clouds that had not previously produced natural lightning. Studies show that about 90 percent of the lightning strikes to aircraft are thought to be initiated by the presence of the aircraft itself. The scary statistic, however, is that 40 percent of all discharges involving airborne aircraft occurred in areas where no thunderstorms were reported.

Apollo 12

One of the more famous cases of aircraft-initiated lightning is the Apollo 12 launch at the Kennedy Space Center, Florida, in November 1969. The Saturn V rocket was struck not once but twice on its way into orbit.

According to the 1970 NASA findings, other than these two strikes, there was no other lightning activity reported six hours before or six hours after the launch. At the time of the launch, a cold front was moving south into the launch area. Broken towering cumulus topping out at 23,000 feet with light to moderate rain showers were reported.

Rarely Fatal

Damage to airborne aircraft struck by lightning includes minor pitting or scarring to the aircraft’s skin to complete destruction of the aircraft.

Besides direct damage at the point of entry and/or exit, indirect effects that include the loss of VHF communication, loss of navigation equipment, and loss of instrument panel gauges are also possible.

In 1963, a Pan American Airlines Boeing 707 over Elkton, Maryland, was struck by lightning while in a holding pattern at 5,000 feet. The outermost fuel tank in the left wing exploded causing two other fuel tanks to follow suit. There were no survivors.  

• READ MORE: Does the FAA Punish Pilots for Logbook Mistakes?

It’s certainly true that a catastrophic accident such as this is extremely rare, but lightning strikes to aircraft are more common than you might imagine—most of which are aircraft-initiated strikes.

Based on compiled data it is estimated that in the U.S. a commercial airliner is struck once for every 3,000 hours flown. That’s an equivalent of about one strike each year. 

Melting Level

While aircraft-initiated lightning is still being actively studied, there are a few important characteristics to consider.

Based on the current research, it doesn’t take flying in or near a mature thunderstorm to become the victim of a lightning strike. The mere presence of the aircraft in an environment conducive to an electrical discharge is all that is necessary.

Most of the aircraft-initiated lightning strikes occur when the aircraft is flying at or near the melting level (0 degrees Celsius). The preferred temperatures include a range from plus-3 C to minus-5 C, with the highest number of incidents occurring right at the melting level.  

A few of the strikes down low are the result of an aircraft intercepting a lightning strike in progress. Essentially, this is the case of being in the wrong place at the wrong time.

On the other hand, aircraft-initiated strikes are observed the most are between 3 km and 5 km or 10,000 to 16,000 feet during the warm season. Once again, temperature is a key factor. The melting level that typically occurs is in this same range of altitudes throughout the summer months.  

Low-Topped Convection

In general, natural lightning in deep, moist convection doesn’t form until the tops of the storm build well above the melting level.

For lightning to form, three ingredients must be simultaneously present. These include vapor-born ice crystals, graupel, and supercooled liquid water. If any one of these three is missing in sufficient quantities, natural lightning doesn’t generally occur, but this not to say the cloud is void of all electrical activity—some still remains.    

Therefore, an aircraft-initiated lightning strike typically occurs within local air mass instability within low-topped convection.

Often low-topped convection doesn’t produce natural lightning. The updrafts are rather weak in comparison to those that do produce lightning. Consequently, the updrafts do not carry enough supercooled liquid water into the upper part of the cloud where it is needed. 

• READ MORE: What Are Echo Tops?

Clouds and Precipitation

An overwhelming number of lightning strikes occur within the cloud itself. Only a very small percentage of strikes occur outside of the cloud boundary or below the cloud.

Here’s the key: A very large percentage of the strikes occur within precipitation to include rain, snow, snow grains, ice pellets, and hail. It is not uncommon to find a mixture of these near the melting level. 

Keep Your Distance?

The FAA encourages all pilots to keep a safe distance from an active thunderstorm for obvious reasons.

Unfortunately, this practice alone isn’t quite enough. Even when thunderstorms (natural lightning) are not occurring or expected to occur, an aircraft-initiated lightning strike can still be a risk.

In order to avoid an encounter with lightning, the best advice is to remain in cloud-free air whenever possible, especially when the atmosphere is conditionally unstable and capable of producing marginally deep, moist convection extending well above the melting level.

While it may be difficult, the best advice is to operate outside of areas of precipitation and minimize your time in clouds and precipitation near the melting level.

The post How Can an Aircraft Get Struck by Lightning Without a Close Thunderstorm? appeared first on FLYING Magazine.

Answer: The short answer is no. But unfortunately there’s a lot of “tribal knowledge” surrounding logbooks and what can happen. FLYING contacted the FAA for the correct information.

Endorsements

The CFI should be familiar with Advisory Circular 61-65 (H), which contains the endorsements an instructor is allowed to give. The language is copied verbatim. If you are a learner pilot, the first endorsement you will get is the TSA citizenship verification endorsement in accordance with 49 CFR 1552.3(h).

FAR 61.51 covers pilot logbooks and details how to log “training time and aeronautical experience.” It states that each person must document and record the following time in a manner acceptable to the administrator:

(1) Training and  aeronautical experience used to meet the requirements for a certificate, rating, or flight review of this part.

(2) The aeronautical experience required for meeting the recent flight experience requirements of this part.

Part B covers logbook entries, stating that “for the purposes of meeting the requirements of paragraph (a) of this section, each person must enter the following information for each flight or lesson logged:

(1) General—

(i) Date.

(ii) Total flight time or lesson time.

(iii) Location where the aircraft departed and arrived, or for lessons in a full flight simulator or flight training device, the location where the lesson occurred.

(iv) Type and identification of aircraft, full flight simulator, flight training device, or aviation training device, as appropriate.”

The savvy CFI logs all instruction given, including ground time and the topics covered. If the learner takes the time to be there, they should get credit for the experience.

As far as “messing up an entry in a logbook,” FLYING posed a series of questions gleaned from scenarios encountered in more than 30 years of flight training on both sides of the CFI certificate.

Ink Color

I start with this because when I was working on my CFII certificate, I logged time in my own logbook with blue ink and the CFII who I was training with positively clutched her pearls over that one.

According to the FAA, they do not require a specific ink color for a paper logbook.

The logging of time spent using an advanced aviation training device (AATD) can be controversial as there are some CFIs who refuse to do it, saying it will “ruin” a logbook.

According to the FAA: “Simply logging time (in any capacity) does not ruin a logbook, but the pilot must ensure they are properly categorizing the flight time logged. For example, if a pilot decided to record their time spent using an AATD in their logbook, that is acceptable. However, the AATD time could not be counted toward cross-country time for pilot certification.”

Set Up Your Own Logbook

As most logbooks have a few blank columns, it’s a good idea to designate them to suit your needs. For example, you might have one for ground training received or given, AATD, solo flight, etc. You can have an entire section set aside for ground instruction, dual instruction given, etc.

Endorsements

There are many logbooks with preprinted endorsements, but you may run out of room. The FAA does not require endorsements to be on a specific page or in a specific location in the logbook. 

“Endorsements can be made in a pilot’s logbook or other documents acceptable to the administrator if the learner uses an electronic logbook rather than paper, in order to show they meet the aeronautical experience requirements for the certificate or rating that may be in paper form or electronic,” FAA said. “Keep in mind that many endorsements require a CFI’s signature which may not work with an electronic logbook.” 

For check rides most learners print out spreadsheets of their experience and have the CFI sign those.

Mistakes

Mistakes do happen. Usually they are math errors.

Filling out a logbook takes a fair amount of concentration, as does totaling up the columns and double checking the math before you sign the page. Take care when you do this, and please be extra careful when it comes to totaling up required experience for a check ride. You do not want a learner to go for a check ride and be turned away because they are missing 0.2 of something, or a takeoff and night landing or two. 

If you make a mistake, correct it. Please note that the FAA does not have specific guidance on correcting logbook errors. According to the source at the FAA, “choosing a particular correction style (white-out, crossing out the error and correcting, crossing out the line and making a new entry, etc.) is up to the pilot.”

The post Does the FAA Punish Pilots for Logbook Mistakes? appeared first on FLYING Magazine.

Answer: In the scenario you described and since ATC asked you to do the maneuver in the pattern, it’s not unexpected.

• READ MORE: What Are Echo Tops?

S-turns and 360-degree turns are methods of creating space between aircraft. This keeps you from overtaking another, most likely slower, aircraft. It’s similar to the way bands march in place for a few minutes during parades to create more space between them and the parade floats, horses, or other bands ahead of them. At a towered airport, if the controller tells you to do this, they are trying to create space between you and the aircraft you are following.

While in the pattern, listen carefully for what kind of aircraft you are sharing space with. If you are flying a Cessna 182 or a twin and there is a slower aircraft like a Cessna Skycatcher or Piper Cub ahead of you, you’re probably going to need to slow down.

• READ MORE: What to Do When You Lose Your Logbook

At all times it is up to the pilot in command (PIC) to determine if it is safe to do these maneuvers If ATC asks you to do a 360-degree turn and there is an aircraft in the way, don’t do it and advise “unable.” At a nontowered airport, 360-degree turns in the pattern are a little dicey. A better option is to depart the pattern and reenter on the 45.

The post When Is It OK to Perform Unexpected Maneuvers in the Pattern? appeared first on FLYING Magazine.

Answer: The short answer is no. Echo top height is a volume product that originates from the NWS WSR-88D NEXRAD Doppler radars.

This is the same network of radars that is used to build the familiar radar mosaic pilots readily use in the cockpit. While not provided in the FIS-B broadcast, the echo top height product, however, is arguably the most misused data that is broadcast by SiriusXM to your satellite-based weather receiver.

Despite what many pilots are taught, this product does not represent the height of the cloud tops and should never be used as such since it is often likely to produce unreliable and inconsistent results.

When looking at any ground-based radar depiction, the colors you see are mapped to a quantity in decibels of Z, often abbreviated dBZ, where Z is the reflectivity parameter. As the name implies, reflectivity is the amount of energy that is returned (reflected) back to the receiver after hitting a target.

For precipitation, these targets are called hydrometeors that include rain, snow, ice pellets, and hail. There are a few exceptions, but generally speaking, the higher the dBZ value, the heavier the precipitation.

All deep, moist convection or thunderstorms have both a cloud top (the highest point of the cloud as measured from sea level) and top of the precipitation core within the convection. The “top” of the precipitation core is defined as the msl height of the highest radar reflectivity of 18 dBZ. This altitude is referred to as the echo top height.   

For example, imagine taking a vertical “slice” through a typical thunderstorm, such as the one shown above. The white dashed line shows the west-to-east slice with the echo top height shown on the left and the base reflectivity from the lowest elevation angle shown on the right. The radar depiction on the right is the view most familiar to a pilot.

However, to better illustrate how the echo tops are determined, the depiction below is this same slice from above that is shown as a vertical cross section of the radar reflectivity. In other words, it depicts all possible elevation angles from the radar’s volume scan through this slice.

The colors are the reflectivity values in dBZ. The highest values shown in the precipitation core are about 55-60 dBZ and are all below about 7 kilometers (about 23,000 feet). As height increases in the core, notice the values drop off to less than 15 dBZ.

By connecting the points where the values in the core drop off to the 18 dBZ value, this represents the echo top height (shown by the white squiggly line). For this cell, the highest point in this cross-section is 17 kilometers or roughly 56,000 feet msl.

Cloud top height, on the other hand, is higher than the echo top height. In fact, it can be 5,000 to 10,000 feet higher in some of the most intense storms.

The visible satellite image below is a good example of thunderstorms with overshooting tops. Given the time of day, the highest tops actually cast a shadow on the thunderstorm anvil. This is the column of air in the thunderstorm that will usually have the highest echo tops due to the vigorous updraft. 

Echo top heights are specifically used by forecasters to identify the most significant storms by locating the highest echo regions. Stronger updrafts are seen in regions where the highest echo tops are located.

Moreover, the parameter that has the highest apparent correlation with lightning is not the highest cloud top but rather the highest detected radar echo top of 30 dBZ or greater.

Shown above is the SiriusXM composite radar mosaic shown with the Garmin Pilot app. In addition to the radar reflectivity, storm cell identification tracking (SCIT) markers are shown.

These attempt to identify the movement and echo top height of various cells in the radar mosaic. The height provided is measured in hundreds of feet. If there’s an arrow, this defines the direction of movement, and the end of the arrow represents where the cell might be located in the next 60 minutes given its current speed and direction of movement.  

Lastly, this may seem obvious, but echo tops are not going to help identify the vertical extent of many weather systems unless those clouds are producing some kind of precipitation in the form of rain, snow, hail, or ice pellets.

Therefore, a stratus deck, even one that has some depth, won’t likely be picked up by the radar. In fact, it’s not likely you will see echo tops shown below 20,000 feet because of this. Echo tops are more appropriate for convective precipitation where the clouds have significant vertical depth.  

The post What Are Echo Tops? appeared first on FLYING Magazine.

Answer: You’re in luck. The paper student pilot certificate was issued by the aviation medical examiner (AME) and not done through IACRA as we know it, so it is doubtful the learner already has an IACRA account.

• READ MORE: Is There an Official Weather Briefing

All you have to do is sit down with the learner and create a new application. Simply follow the prompts and fill out the application. In a few weeks he will get a plastic student pilot certificate in the mail.

Also, don’t forget to also verify the learner’s citizenship and give him a TSA endorsement, which have become requirements since 2002.

Do you have a question about aviation that’s been bugging you? Ask us anything you’ve ever wanted to know about aviation. Our experts in general aviation, flight training, aircraft, avionics, and more may attempt to answer your question in a future article.

The post How Do You Obtain a Student Pilot Certificate After a Break in Training? appeared first on FLYING Magazine.