When stressed learning to fly approaches, it is very easy to get behind the airplane. During my IFR training, it was not uncommon for my instructor to ask me, “What is the next thing to do?” And sometimes it was difficult, if not impossible, to answer! In any stressful situation, the human mind easily can become a blank slate. Obviously, this can be a dangerous situation while flying an airplane in the clouds.
Staying ahead of the airplane is much easier if the IFR pilot realizes that 1) there is a generic basic flow to every IFR flight and 2) when the items in the basic flow are memorized, mistakes are minimized. Furthermore, if the IFR pilot knows the items that are needed to fly a specific type of approach (e.g. GPS, VOR, or ILS), stress and mistakes are further minimized. In my experience teaching IFR flying, requiring students to memorize these items results in students having less difficulty learning approaches.
BASIC FLOW OF ALL IFR FLIGHTS
Each IFR flight terminating in an approach has the same basic elements, as outlined below.
1. Get started. Obtain clearance and follow ATC instructions for climbing to a specific altitude and heading. Upon reaching desired altitude, level off and complete the cruise checklist.
2. Run through the approach briefing. Set up for the approach via an approach briefing. Although there may be other useful checklists, my choice has been the WISP and ICE ATM checklists (see below). Each checklist emphasizes different items and, therefore, it may be helpful to run through both checklists to double check that the set up for the approach has been thought through completely and properly.
– ICEATM:
I – Enterthe Localizer or VOR frequencies and identify them via the Morse code or enter the approach into the GPS.
C – Set the inbound course using the OBS knob on the VOR or HSI.
E – State method of approach entry (full or vectored) and make sure it is properly entered in the GPS if flying a GPS approach. If a full approach, make sure to run through the entire procedure (holding pattern, DME arc, etc).
A – Run through the altitudes used in the approach, i.e. 1) initial altitude at start of approach, 2) step down altitudes if present, and 3) MDA or DA altitudes.
T – Is the timer needed – is it a timed approach?
M – Run through the missed approach instructions.
This list is followed by the nice-to-dos, such as: listen to the weather, make sure the marker beacon is on if needed, and make sure the CDI of the VOR or HSI is slaved appropriately to either the VOR or the GPS.
WISP:
W – Obtain the weather.
I – Make sure your flight instruments are set correctly (e.g. set barometric pressure, and CDI correctly).
S – Go through the avionics stack from top to bottom and make sure everything is set correctly (e.g. slave the CDI to the GPS or VOR, activate the marker beacon, tune in radio frequencies, tune in and identify VOR frequencies, or load the GPS approach into the GPS).
P – Run through the approach procedure, including the missed approach directions.
3. Expect missed approach instructions. Expect ATC to deliver these instructions prior to joining the approach course. Be ready to copy them down.
4. Join approach course. Anticipate joining the initial or final approach course. Instrument scan elements that need particular attention include, 1) distance to IAF or FAF shown on the GPS, and 2) CDI movement. Vocalizing the distance to the IAF or FAF aloud each time the eyes look at the GPS during the instrument scan is very helpful in maintaining focus on the IAF or FAF. This minimizes flying past these fixes without realizing it. If flying a full approach, once the IAF has been reached, running through the five Ts is helpful (as it is when passing any waypoint) (see below for the five Ts). For this portion of the approach, the clock becomes a necessary part of the instrument scan. When the time is vocalized aloud each time the eyes look at the clock during the instrument scan, the pilot remains focused on the endpoint of the leg being flown. Again, the mistake of flying past the waypoint and not realizing it is minimized using this technique.
Time – start the clock (or note the time)
Turn – turn to the new heading
Twist – turn the OBS to desired course
Throttle – change power setting if needed
Talk – talk to ATC if necessary
5.Run through the SADS checklist 2 miles prior to reaching the FAF. Two miles prior to reaching the FAF, it is prudent to run through this checklist to ensure a smooth transition to the approach course.
S – Slow down to appropriate speed (e.g. 90 kts for Cessna 172). Incorporate looking at the distance to the FAF into the instrument scan and say the distance aloud each time the eyes look at the GPS during the instrument scan. Again, this keeps the focus on the FAF, making it difficult to fly past it without starting the descent on time.
A – Altitude check. Is the current altitude the altitude allowed in this segment of the approach (i.e. is a descent allowed to a lower altitude?) and reread the DA or MDA.
D – Descent checklist. Perform the descent checklist.
S – Set-up for descent. When arriving at either 1) the FAF for a nonprecision approach (VOR, nonprecision GPS, localizer, or NDB approach), 2) the glideslope of a precision ILS approach, or 3) the glide path for an APV approach, lower the flaps, decrease the power and pitch down to attain the proper descent rate for the approach leg. The pilot should know the approximate pitch and power settings that will result in the airspeed/descent rate needed for a precision and nonprecision approach (e.g. in a Cessna 172 put in 10 degrees of flaps, pull the power back to about 1600 RPMs and pitch down about 4 degrees to maintain 90 kts while descending in a precision approach).
6. Descend to MDA or DA. The instrument scan now should include calling out altitudes as the descent is made down to the MDA of a nonprecision approach or a DA of a precision approach. If the airport environment is not detected at the DA, a missed approach should be initiated. If flying a nonprecision approach, once the MDA has been reached, 1) the distance to the MAP or 2) the clock (if a timed approach) should be included in the scan. As stated previously, it is helpful to say aloud the distance or the time each time the pilot looks at the GPS or clock so that the pilot does not fly past the MAP.
Staying ahead of the airplane is key to reducing stress and successfully completing an IFR approach to a runway environment. Use of the above techniques aid in minimizing errors in flying approaches and similar techniques can be useful in flying holds, as well.
Wishing you safe and enjoyable IFR flights!
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In my last post, I discussed Pressure and Density Altitude calculations and their contribution to the total performance equation. In this post, I’ll cover some of the other values in the takeoff equation that we don’t always keep in mind.
When calculating performance for our airplane, we use the charts found in the Pilot’s Operating Handbook (POH) for our aircraft. These charts generally account for density altitude and include conditions and notes to address other factors. When was the last time that you took a close look at the conditions and notes associated with the chart? They are important and are there for a reason.
As an example, the “Short Field Takeoff Distance at 2550 Pounds” table for the Cessna 172S lists the following conditions:
Flaps 10°
Full Throttle Prior to Brake Release
Paved, level, dry runway
Zero Wind
Lift Off: 51 KIAS
Speed at 50 Ft: 56 KIAS
It also includes the following notes:
Short field technique as specified in Section 4.
Prior to takeoff from fields above 3000 feet elevation, the mixture should be leaned to give maximum RPM in a full throttle, static runup.
Decrease distances 10% for each 9 knots headwind. For operation with tail winds up to 10 knots, increase distances by 10% for each 2 knots.
For operation on dry, grass runway, increase distances by 15% of the “ground roll” figure.
Many of these items are related to technique and aircraft configuration and are easy to comply with. Some can be tougher.
Take the “Paved, level, dry runway” condition. This seems simple enough but have you checked the grade on the runway at your home airport? What about the runway where you are planning to land and will have to later takeoff? Do you know where to find this information? Do you know how it will affect your takeoff distances when you find this information?
Runway slope information is published by the FAA in the Airport/Facility Directory. The information can also be found on the Airport Diagram or Airport Sketch for the airport in the Terminal Procedures Publication (approach plates). Many commercial sources, GPS databases, and pilot apps also include the information.
Looking at the Clermont County / Sporty’s Airport, we find a slope of 0.9% uphill on runway 22 and the same slope downhill on runway 4. This equates to about 32′ of elevation change from one end to the other of the 3566′ runway. The grade is not a consistent slope of 0.9% but there isn’t information readily available that tells us what the slope is at different points along the runway so we’ll stick with the 0.9%.
The chart in the POH doesn’t provide any indication as to what we should do when the runway is not “level.”
For help in addressing this adjustment, I would look to an expert in flying on “non-level” runways. The late Sparky Imeson, author of the Mountain Flying Bible Revised suggests the following rule of thumb with regard to gradient. For a 1% upslope, which is approximately runway 22’s slope, increase the takeoff distance by 7.5%. While not specified on the Imeson family’s website, this should be 7.5% of the ground roll. If a 2% upslope, use a 14% increase; 4% upslope, 25.5% increase; and 6% upslope, 39.5% increase.
Another aspect of the notes which has no resolution in the POH is departing from a wet or otherwise contaminated runway.
A wet runway will change the friction between the tires and the surface. While this may decrease friction, I wouldn’t expect it to shorten the takeoff roll.
Standing water will increase the takeoff roll. This is due to “displacement and impingement drag” as the spray from the tires is displaced and strikes the aircraft. The FAA’s AC 91-6A regarding Water, Snow, and Slush on the Runway hasn’t been updated in over 30 years. At that time there was no clear engineering data on how much water or slush on the runway affected the takeoff roll.
You should not attempt a takeoff when standing water or slush on the runway is more than one half an inch deep.
Imeson’s website has some rules of thumb regarding surface contamination as well.
Cessna recommends increasing the ground roll figure by 15% when taking off from a dry, grass runway. This guidance may be incomplete as it does not account for the length of the grass or the roughness or softness of the surface. 15% will be fine when the grass is short and the ground is firm and smooth but may be insufficient if the grass is longer or the ground is softer or rougher. Using a soft-field technique rather than the chart’s indicated short-field technique (see Note 1 above) may also influence this distance.
All this said, the chart in the POH is our best place to start on any takeoff calculations. You just have to keep the conditions and notes in mind and know when they won’t account for your current situation. Have fun and stay safe!
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This week I will celebrate the 29th anniversary of my 29th birthday. Birthdays, which are so anticipated when you’re young.
I can’t wait until I’m 6 and go to school. I can’t wait until I’m 10 and can take a tractor to the field by myself. I can’t wait until I’m 16 so I can drive. There are reasons you want to be 21.
The birthdays just become numbers after you get to be middle aged. I am starting to qualify for some senior discounts so that is a plus, but now birthdays become a time to look back and reflect on a blessed life. I had strict but loving parents. I am married to the most beautiful girl (both outside and inside) in the world and I go to work at an airport. So I have decided to use this space to look back at the 6 decades through which I have lived and reveal what I believe to be the major advancement in general aviation for each one.
1950’s – The Nose Wheel. The decade of my birth saw wide fleet-wide adoption of aircraft with the third wheel under the nose instead of the tail. The first 5 decades of aviation was dominated by so called “conventional gear” or tail-wheel aircraft. Visit the “legacy” aircraft flight line at any big air show and you will see rows of Cubs, C-195s, Stearmans, Staggerwings, and Electras. Early airports (like Bowman Field (KLOU) in Louisville, the oldest continually operating airport) were little more than big flat spots where general aviation airplanes could always land into the wind. Their nose high attitude on the ground kept the propeller safely clear of the uneven turf.
With the advent of heavier aircraft the turf was replaced with pavement. By moving the mains aft and propping up the nose of the airplane manufacturers discovered on ground visibility improved and there was a marked reduction in ground loops during those perilous moments between touchdown and chocks. I guess this trend toward metal nose wheel airplanes started in the 1940s with the Bonanza, but I contend it was the 50’s when the Pacer became the Tri-Pacer and the 170 became the 172 marking the domination of nose wheels we still see today.
1960’s – “That’s one small step for man, one giant leap for mankind.” What did President Kennedy’s declaration vowing to “Before this decade is through, we will put a man on the Moon and return him safely to Earth” have to do with general aviation? Well, for one thing, it inspired a generation of pilots (including this one) to get excited about all things aeronautical. But more importantly technology needed to get smaller and lighter if they were going to reach escape velocity. Tubes were replaced by transistors which were replaced by silicon chips. Power requirements were reduced and computing power increased. All these innovations were forerunners leading to modern avionics, smart phones and iPads upon which we rely today. A guy named Hal Shevers started selling portable aviation radios out of the trunk of his Studebaker, a business that gave birth to Sporty’s Pilot Shop.
1970’s – Expansion of the aviation infrastructure. During this decade, the number and quality of airports dramatically increased. Rural communities came to understand that economic development would come on an airplane, not a Greyhound bus. Corn fields became airports. Piper, Cessna and Beechcraft were producing tens of thousands of airplanes a year. As a testament to industrial efficiency, those airplanes were all made of aluminum and had engines built by Lycoming or Continental with mechanically tuned radios mostly from King or Narco. Almost every FBO was a dealer for one of the manufacturers and thousands of us were learning to fly. It is the decade in which I first flew an airplane opening the door to many adventures.
1980s – The birth of the internet. While not fully developed as the World Wide Web, computers were being linked and email became possible. Prior to this technology, teletypes and fax machines were the way electronic documents moved. Indeed the numerous Flight Service Stations (FSS) relied on these technologies for the surface observations, forecasts and radar maps they provided to pilots of the era. To get a weather briefing, a pilot would either call or visit in person one of the several dozen FSS facilities. Many had local radar, but for cross country planning, the information we received may well have been over an hour old.
Nowadays, we take out our phone, open an app and receive near real time information on weather and NOTAMS from across the country – courtesy of the internet.
1990s – You are here. Sure, transoceanic airliners and high end corporate jets had inertial guidance and LORAN systems for navigation, but for most of us, navigation and situational awareness was divined by some combination of pilotage, dead reckoning and aligning needles from VORs and ADFs. A competent pilot knew where they were in general, but often, his last known position was the approach end of their departure runway. In 1989 the Global Positioning Satellite (GPS) constellation became operational. The 1990s saw first the introduction of hand held GPS devices into the general aviation cockpits. These incredible little boxes were both accurate and affordable providing both a course line and accurate positioning along it. We marveled at being able to know where we were – exactly. So accurate and reliable pilots would remark, “If it says you are here and you don’t think so, you are wrong!” In 1998 Garmin introduced its GNS-430 Com Navigator relegating the need to align needles to determine a fix to the dust bin of Instrument Flight Rules history.
2000s – The information age hits the cockpit. Avidyne introduces its “glass” displays in the cockpit of Cirrus aircraft. Garmin soon follows with the G1000 in Cessna and Diamond airplanes. Soon the 10 – 17 inch “monitors” are in every new aircraft save some special utility and sport aircraft such as Huskies, Maules and Citabrias. Pilots could literally fly coast to coast and never take a chart out of their flight cases. All the terrain, airways, and airports are graphically presented on Multi-Function Displays (MFDs). Airport information, right down to the phone numbers of the nearest hotels were all stored in the avionics. Early in the decade, Bendix King launched its ground based Flight Information System (FIS) providing near real time weather in the cockpit. Traffic Avoidance Systems (TAS) from King, Ryan and Goodrich became more affordable and prevalent. XM Satellite Radio teamed with WXWorks to stream satellite based weather into the cockpit (along with a couple hundred audio stations). Not having the line of sight limitations of the ground based system those FIS stations were eventually abandoned. This technological revolution so greatly increased situational awareness we all assumed those Controlled Flight Into Terrain (CFIT) and continued VFR into IMC accidents would be eliminated. Unfortunately, it seems pilots are destined to fly into rocks and weather for which they are unprepared.
20 teens – So far it’s the iPad. Only two years old, this decade has seen the nearly ubiquitous acceptance of tablet computers (and their accessories) by pilots. Everything from flight planning, performance planning, weight and balance, cross country navigation, to logging the flight can all be performed on these 10 inch wonders. GPS/ADS-B receivers like the Stratus provide in-cockpit weather and situational awareness for Champs, Gulfstreams and everything in between.
Powered flight is 109 years old. I have been around to see more than half of that. After reflecting on the past, I like to ponder the future and wonder what the next six decades will bring. I offer the following predictions.
The rest of the teens– New engines, new fuels. I predict leaded gasoline will be banned in California. This will lead to the development of new fuels and engines to use them. Cessna introduced its Compression Engine, Jet A burning Skylane at AirVenture this year. Pipistrel has an airframe that will tolerate alcohol in its gasoline. Propellers will become more efficient with new designs and materials allowing us to squeeze more knots from each gallon of whatever we are burning.
2020s – Next Gen goes fully operational. ADS-B in/out technology will allow us to not only know precisely where we are, but where all the other airplanes are around us. ATC can make better use of available runways and offer altitude and speed advisories that will eliminate the need to ever hold at a fix. Unmanned Aerial Systems (UAS) will share the skies with those of us who still desire to fly. Airliners are certified single pilot eliminating the predicted pilot shortage.
2030s – Advances in materials allow airplanes to “morph”. As airplanes have gotten bigger and faster, so has the runway required for them to safely take off and land. My prediction here is that airplanes will not only be able to configure gear and flaps, but the wings and control surfaces themselves, small and thin for high speed cruise – large and thick for slow take offs and landings allowing the largest airliner to operate out of runways less than a mile long.
2040s – Autonomous piloting of both airlines and private airplanes. Aircraft manufacturers are able to eliminate the part that fails the most often. The pilot.
2050s – Teleportation. Just look at an old Star Trek episode.
As we approach the 2012 election season the number of Temporary Flight Restrictions (TFRs) will significantly increase as the president travels more frequently across the US campaigning for re-election. While TFRs can be established for a variety of security purposes, presidential TFRs tend to be the most common and restrictive type. These typically restrict all flight training operations within a 10 or 12 NM radius area around the area where the president is visiting, and extend from the surface to 17,999 feet MSL (this zone is commonly called the inner core). An outer ring then extends around the inner core out to 30 NM, and requires all aircraft to be on an IFR or VFR flight plan, be on a discrete transponder code and be in contact with ATC. You’ll also see smaller TFRs established for other VIPs which typically extend 3 miles out from the center of the visit and up to 3,000 feet AGL.
TFR awareness is towards the top of my priority list during flight planning. With today’s multiple forms of electronic communication and flight planning services there’s no excuse for not being aware of a TFR. Here’s a list of resources to make sure a TFR never sneaks up on you.
1. Official Flight Service Station (FSS) weather briefing
Calling FSS at 1-800-WX-BRIEF is the best way to make sure you’re getting the most current TFR information for your route of flight. And if the briefer doesn’t mention anything about TFRs during the briefing, make it a point to if at the end of the call to verify that there are none scheduled anywhere near your planned flight.
2. FAA TFR website
The FAA’s official TFR website is available at tfr.faa.gov. While this isn’t the most user-friendly website out there, the fact that it comes right from the source and doesn’t rely on third party dissemination adds some value. The easiest way to use this site it is to first zoom into the TFR map for the area you’ll be flying (TFRs are shown with red lines), and then select a TFR from the list below the map for all the details.
3. FAA Safety email notifications
One of the benefits from signing up for an account at the FAA Safety Team (FAASTeam) website is the automatic email notifications, including an option to receive alerts for upcoming VIP Movement and their associated TFRs. After signing up for a free account at www.faasafety.gov, click on your email address in the upper right of the screen and select My Preferences and Profile. Here you can specify email options, and you’ll want to check the box next to Selected ATC Notices to receive the TFR alerts. One thing to point out is you will only receive alerts for the region around your zip code, so you won’t get notices for the entire country.
4. AOPA Member TFR email notifications
If you’re an Aircraft Owners and Pilots Association (AOPA) member, I’d recommend signing up to receive their TFR email notifications. To get on the list, email AOPA Member Services at [email protected] and ask to be added to the TFR email alert list. These typically arrive around the same time as the FAA Safety email alerts and have helpful links to both the AOPA & FAA websites for more information.
5. Mobile flight planning apps
Many iPhone, iPad and Android aviation apps incorporate TFR maps and descriptions into their flight planning tools, which is especially helpful since many of us carry these devices with us everywhere we go. I find the ForeFlight Mobile and Garmin Pilot apps especially useful, since they allow you to overlay the TFRs on VFR Sectionals and IFR En Route charts, making it easy to see what airports are affected and how to plan around the restricted area.
6. TFRs on Twitter
Twitter is one of my favorite ways to stay up on current events, and it’s also a great way to keep up on TFRs. One source to follow is the FAA twitter feed (@FAANews), but I find that the TFR info often gets lost with all their other news postings. While not an official source, I like to keep a close eye on the VIP TFR Info feed (@VIP_TFR), which only posts tweets on TFRs and includes a direct link to the official NOTAM on the FAA’s site.
7. In-flight TFR updates over ADS-B
Portable ADS-B receivers have become very popular in the last several months, mainly because they offer subscription-free weather in the cockpit. In addition to providing NEXRAD radar and text weather products, ADS-B also provides near real-time TFR updates in the air. For example when using the wireless Stratus ADS-B weather receiver with ForeFlight Mobile on the iPad, you can see the TFR boundaries depicted on VFR/IFR charts along with your route. This provides great peace of mind in the air to complement the briefings you received on the ground.
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One of the best ways to become a better pilot is easy, free and doesn’t require a flight instructor. Sound too good to be true? Hardly. In fact, you may already do it, at least in some form.
It’s the post-flight evaluation.
Every time you fly, you probably have some gut feel about how well you performed. A solid post-flight evaluation is really just taking this gut feel to the next level. Try to force yourself to review each part of the flight–from pre-flight to landing–in a structured, disciplined way. A good time to do this is on the drive home from the airport, while the details of the flight are still fresh in your mind.
What should you review? Beyond just “that landing stunk,” replay the flight in your mind and go through a quick checklist:
Did I violate any FARs? Hopefully not, but another question might be “what do the FARs say about that situation?” Did your flight raise any questions about the regulations that suggest further study?
Did I break any personal minimums? This is often an uncomfortable question. Breaking FARs is very rare, but more than once I’ve had to admit to pushing my personal limits, whether for crosswinds or weather. If you routinely break your minimums, then they aren’t real minimums. Don’t have personal minimums? Make some. Even if they’re not extremely detailed, you ought to have some sense of what conditions are too much for you and your airplane.
Did I learn any new tricks? Sometimes we do and simply fail to recognize it. If your landings today were all excellent, ask why. You may have discovered a better approach.
Did I uncover any traps? Another place to be brutally honest. I can remember at least one instance when I accepted a clearance I should not have. It was an accident waiting to happen, but I didn’t fully realize it until after the flight. I walked through how it happened and how to avoid it next time–and I haven’t made that mistake again.
Did the weather match the forecast? Even on the shortest flight, there’s usually something weather-related to learn. On cross-country flights, I go so far as to save the weather/radar map I looked at before the flight and compare it to the one right after my flight. Seeing the difference between forecast and actual and then exploring why it changed is a great learning opportunity. You really can and should learn about weather on every flight, even if you only fly VFR.
This approach may sound obvious to some, but a disciplined review of your flying can pay big rewards. For student pilots, this is especially true, as you can learn an awful lot without the Hobbs running (which means it’s free). You might set a goal of getting 3 hours of learning out of every hour of actual flying. Some pilots go so far as to re-fly the flight on a home flight simulator or using a cockpit video camera.
The post-flight evaluation isn’t just for student pilots, though. After you earn your license, there isn’t much of a requirement to keep learning other than the obligatory flight review every two years. The safe pilot has a much higher standard than this, though. The impetus is on you to continually get better, which means every flight should be a learning experience. An honest self-critique can also be a great way to ward off complacency, which is one of the most dangerous traits any pilot can have.
Most importantly, it’s vital to do a post-flight evaluation after every flight, no matter how good it was. After all, that “good flight” may not be so good after some introspection.
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Pressure and Density Altitude on FAA Tests and in the Real World
One of the things that you must learn as a pilot is how to determine the approximate performance you can expect out of your airplane on a given day. I say the “approximate performance” because there are simply too many variables that will affect our airplane’s performance for which we can’t directly account to get exact performance.
Pressure and Density Altitude calculations are key factors in determining performance but these can be confusing. Also confusing is the FAA’s emphasis on precise calculations on the FAA knowledge test when these values are only a part of the total performance equation. I’ll cover some of the other values in the equation in another blog post. In this post, let’s take a look at Pressure and Density Altitude.
The FAA defines Pressure Altitude as the altitude above the standard 29.92″ Hg plane. While Density Altitude is the Pressure Altitude corrected for nonstandard temperature.
Density Altitude is used in computing the performance of an aircraft and its engines. Some manufacturers utilize Pressure Altitude on their performance charts but they address the nonstandard temperature within the chart. In this way, they are actually using Density Altitude but the pilot isn’t required to calculate it.
Variation in Pressure and Density Altitude Calculations
There are several ways that Pressure Altitude can be determined depending on the accuracy and precision required by the calculation.
FAA knowledge test supplements include a table on the “Density Altitude Chart” that shows a “Pressure Altitude Conversion Factor.” The value obtained from this chart is based upon the altimeter setting and is added to the indicated altitude (the correction value will be negative when the altimeter setting is higher than 29.92″ Hg). This correction value is precise to the nearest foot and provides a reasonably accurate measure of Pressure Altitude.
The Density Altitude value obtained from this chart has some minor accuracy issues when using the standard temperature line. The lower anchor point of the standard temperature line is not set at 15° C for sea level as it should be. This lower anchor is set at approximately 16° C. This error in the chart should have less than 100 feet of error with regard to calculations.
There is a precise and rather involved formula for computing Pressure Altitude with exceptional accuracy. It can be used to calculate the Pressure Altitude out to several decimal places if needed. In general, aviation calculations involving POH values and used airplanes do not require this level of precision or accuracy.
If you are at an airplane, Pressure Altitude can be determined by setting 29.92 in the Kohlsman window and reading the altitude from the altimeter.
Many people calculate Pressure Altitude using the rule of thumb that 1″ Hg change equals 1000′ of altitude change. This rule of thumb is accurate enough for most aviation calculations, as long as you know its limitations. The rule assumes a linear change in pressure with altitude. This assumption is not correct but the answer doesn’t stray far from the truth when the values being calculated are below 10,000′ MSL. The rule, while easy to use, also has a minor inaccuracy as such that 1″ Hg change is not exactly 1000′ of altitude change but this issue should produce less than 100 feet of error per inch of change.
Density Altitude calculations have many of the same issues. In aviation, we use Pressure Altitude and temperature to calculate Density Altitude. Yet, in reality, humidity also has an impact on Density Altitude since water molecules in gaseous form are lighter than the typical molecules in the atmosphere. The more gaseous water (higher humidity) found in the atmosphere, the less dense the air and thus the higher the Density Altitude.
Why do we ignore humidity in common aviation calculations of Density Altitude? Apparently, it was decided at some time in the past that it doesn’t make that big of difference with regard to the performance of the airplane for practical purposes.
Performance Calculations
This brings us back to why we compute Pressure Altitude and Density Altitude in the first place. We want to know how the airplane is going to perform on a given day.
FAA test questions would have you believe that you should calculate your performance to the nearest foot. As most experienced pilots will tell you, this is not grounded in reality. POH performance numbers were developed with a brand new airplane being flown by a test pilot. Do you want to bet your life on a calculation with no error margin in your 5 (or 25) year old airplane being flown by a newly minted Private pilot?
The truth is, you need a safety factor.
One way to build in a safety factor and ease your need to calculate performance to the nearest tenth of a foot is to always round the value. Ignore the rounding rules that you learned in school and round to the next safest value. For example, if your Density Altitude calculation tells you that the Density Altitude for the day will be 3213.65 feet, use 3300 feet or better yet 4000 feet when you go to your POH to calculate your takeoff and landing performance.
You may notice some minor difference in the output for Pressure and Density Altitude when you compare various charts and models of E6Bs. This variation is likely due to the method that the manufacturer selected to compute these values. These differences are generally not significant for practical purposes and should not be a concern.
For the less than practical FAA tests, these differences may mean that you won’t get the exact answer as the FAA. Just use the closest answer and you should be fine. Don’t become overly concerned about this minutia; there are other minutiae on the tests that should have your attention.
In the real world, you are better off rounding up to the next safest value. This does away with things like interpolation on tabular data. It is also a simpler and safer practice.
Keep it simple and stay safe!
https://media.flighttrainingcentral.com/wp-content/uploads/2012/06/05183543/PHAK-TakeoffDistance-25A-Small.png328600studentpltnewshttps://media.flighttrainingcentral.com/wp-content/uploads/2022/01/05155154/FTC-logo-horizontal-fianl.pngstudentpltnews2012-06-29 09:59:542021-06-08 19:23:49Performance on FAA Tests and in the Real World – Part 1
Tips to Help Streamline IFR Training
/in Tips and technique/by StudentpltnewsStaying ahead of the airplane is much easier if the IFR pilot realizes that 1) there is a generic basic flow to every IFR flight and 2) when the items in the basic flow are memorized, mistakes are minimized. Furthermore, if the IFR pilot knows the items that are needed to fly a specific type of approach (e.g. GPS, VOR, or ILS), stress and mistakes are further minimized. In my experience teaching IFR flying, requiring students to memorize these items results in students having less difficulty learning approaches.
BASIC FLOW OF ALL IFR FLIGHTS
Each IFR flight terminating in an approach has the same basic elements, as outlined below.
1. Get started. Obtain clearance and follow ATC instructions for climbing to a specific altitude and heading. Upon reaching desired altitude, level off and complete the cruise checklist.
2. Run through the approach briefing. Set up for the approach via an approach briefing. Although there may be other useful checklists, my choice has been the WISP and ICE ATM checklists (see below). Each checklist emphasizes different items and, therefore, it may be helpful to run through both checklists to double check that the set up for the approach has been thought through completely and properly.
– ICEATM:
I – Enter the Localizer or VOR frequencies and identify them via the Morse code or enter the approach into the GPS.
C – Set the inbound course using the OBS knob on the VOR or HSI.
E – State method of approach entry (full or vectored) and make sure it is properly entered in the GPS if flying a GPS approach. If a full approach, make sure to run through the entire procedure (holding pattern, DME arc, etc).
A – Run through the altitudes used in the approach, i.e. 1) initial altitude at start of approach, 2) step down altitudes if present, and 3) MDA or DA altitudes.
T – Is the timer needed – is it a timed approach?
M – Run through the missed approach instructions.
This list is followed by the nice-to-dos, such as: listen to the weather, make sure the marker beacon is on if needed, and make sure the CDI of the VOR or HSI is slaved appropriately to either the VOR or the GPS.
WISP:
W – Obtain the weather.
I – Make sure your flight instruments are set correctly (e.g. set barometric pressure, and CDI correctly).
S – Go through the avionics stack from top to bottom and make sure everything is set correctly (e.g. slave the CDI to the GPS or VOR, activate the marker beacon, tune in radio frequencies, tune in and identify VOR frequencies, or load the GPS approach into the GPS).
P – Run through the approach procedure, including the missed approach directions.
3. Expect missed approach instructions. Expect ATC to deliver these instructions prior to joining the approach course. Be ready to copy them down.
4. Join approach course. Anticipate joining the initial or final approach course. Instrument scan elements that need particular attention include, 1) distance to IAF or FAF shown on the GPS, and 2) CDI movement. Vocalizing the distance to the IAF or FAF aloud each time the eyes look at the GPS during the instrument scan is very helpful in maintaining focus on the IAF or FAF. This minimizes flying past these fixes without realizing it. If flying a full approach, once the IAF has been reached, running through the five Ts is helpful (as it is when passing any waypoint) (see below for the five Ts). For this portion of the approach, the clock becomes a necessary part of the instrument scan. When the time is vocalized aloud each time the eyes look at the clock during the instrument scan, the pilot remains focused on the endpoint of the leg being flown. Again, the mistake of flying past the waypoint and not realizing it is minimized using this technique.
Turn – turn to the new heading
Twist – turn the OBS to desired course
Throttle – change power setting if needed
Talk – talk to ATC if necessary
5. Run through the SADS checklist 2 miles prior to reaching the FAF. Two miles prior to reaching the FAF, it is prudent to run through this checklist to ensure a smooth transition to the approach course.
S – Slow down to appropriate speed (e.g. 90 kts for Cessna 172). Incorporate looking at the distance to the FAF into the instrument scan and say the distance aloud each time the eyes look at the GPS during the instrument scan. Again, this keeps the focus on the FAF, making it difficult to fly past it without starting the descent on time.
A – Altitude check. Is the current altitude the altitude allowed in this segment of the approach (i.e. is a descent allowed to a lower altitude?) and reread the DA or MDA.
D – Descent checklist. Perform the descent checklist.
S – Set-up for descent. When arriving at either 1) the FAF for a nonprecision approach (VOR, nonprecision GPS, localizer, or NDB approach), 2) the glideslope of a precision ILS approach, or 3) the glide path for an APV approach, lower the flaps, decrease the power and pitch down to attain the proper descent rate for the approach leg. The pilot should know the approximate pitch and power settings that will result in the airspeed/descent rate needed for a precision and nonprecision approach (e.g. in a Cessna 172 put in 10 degrees of flaps, pull the power back to about 1600 RPMs and pitch down about 4 degrees to maintain 90 kts while descending in a precision approach).
6. Descend to MDA or DA. The instrument scan now should include calling out altitudes as the descent is made down to the MDA of a nonprecision approach or a DA of a precision approach. If the airport environment is not detected at the DA, a missed approach should be initiated. If flying a nonprecision approach, once the MDA has been reached, 1) the distance to the MAP or 2) the clock (if a timed approach) should be included in the scan. As stated previously, it is helpful to say aloud the distance or the time each time the pilot looks at the GPS or clock so that the pilot does not fly past the MAP.
Staying ahead of the airplane is key to reducing stress and successfully completing an IFR approach to a runway environment. Use of the above techniques aid in minimizing errors in flying approaches and similar techniques can be useful in flying holds, as well.
Wishing you safe and enjoyable IFR flights!
Performance in the Real World – Part 2
/in Tips and technique/by StudentpltnewsMore Than Just the Calculations
In my last post, I discussed Pressure and Density Altitude calculations and their contribution to the total performance equation. In this post, I’ll cover some of the other values in the takeoff equation that we don’t always keep in mind.
When calculating performance for our airplane, we use the charts found in the Pilot’s Operating Handbook (POH) for our aircraft. These charts generally account for density altitude and include conditions and notes to address other factors. When was the last time that you took a close look at the conditions and notes associated with the chart? They are important and are there for a reason.
It also includes the following notes:
Many of these items are related to technique and aircraft configuration and are easy to comply with. Some can be tougher.
Take the “Paved, level, dry runway” condition. This seems simple enough but have you checked the grade on the runway at your home airport? What about the runway where you are planning to land and will have to later takeoff? Do you know where to find this information? Do you know how it will affect your takeoff distances when you find this information?
Runway slope information is published by the FAA in the Airport/Facility Directory. The information can also be found on the Airport Diagram or Airport Sketch for the airport in the Terminal Procedures Publication (approach plates). Many commercial sources, GPS databases, and pilot apps also include the information.
Looking at the Clermont County / Sporty’s Airport, we find a slope of 0.9% uphill on runway 22 and the same slope downhill on runway 4. This equates to about 32′ of elevation change from one end to the other of the 3566′ runway. The grade is not a consistent slope of 0.9% but there isn’t information readily available that tells us what the slope is at different points along the runway so we’ll stick with the 0.9%.
The chart in the POH doesn’t provide any indication as to what we should do when the runway is not “level.”
For help in addressing this adjustment, I would look to an expert in flying on “non-level” runways. The late Sparky Imeson, author of the Mountain Flying Bible Revised suggests the following rule of thumb with regard to gradient. For a 1% upslope, which is approximately runway 22’s slope, increase the takeoff distance by 7.5%. While not specified on the Imeson family’s website, this should be 7.5% of the ground roll. If a 2% upslope, use a 14% increase; 4% upslope, 25.5% increase; and 6% upslope, 39.5% increase.
Another aspect of the notes which has no resolution in the POH is departing from a wet or otherwise contaminated runway.
A wet runway will change the friction between the tires and the surface. While this may decrease friction, I wouldn’t expect it to shorten the takeoff roll.
Standing water will increase the takeoff roll. This is due to “displacement and impingement drag” as the spray from the tires is displaced and strikes the aircraft. The FAA’s AC 91-6A regarding Water, Snow, and Slush on the Runway hasn’t been updated in over 30 years. At that time there was no clear engineering data on how much water or slush on the runway affected the takeoff roll.
You should not attempt a takeoff when standing water or slush on the runway is more than one half an inch deep.
Imeson’s website has some rules of thumb regarding surface contamination as well.
All this said, the chart in the POH is our best place to start on any takeoff calculations. You just have to keep the conditions and notes in mind and know when they won’t account for your current situation. Have fun and stay safe!
Happy Anniversary
/in Personal stories/by StudentpltnewsThis week I will celebrate the 29th anniversary of my 29th birthday. Birthdays, which are so anticipated when you’re young.
I can’t wait until I’m 6 and go to school. I can’t wait until I’m 10 and can take a tractor to the field by myself. I can’t wait until I’m 16 so I can drive. There are reasons you want to be 21.
The birthdays just become numbers after you get to be middle aged. I am starting to qualify for some senior discounts so that is a plus, but now birthdays become a time to look back and reflect on a blessed life. I had strict but loving parents. I am married to the most beautiful girl (both outside and inside) in the world and I go to work at an airport. So I have decided to use this space to look back at the 6 decades through which I have lived and reveal what I believe to be the major advancement in general aviation for each one.
1950’s – The Nose Wheel. The decade of my birth saw wide fleet-wide adoption of aircraft with the third wheel under the nose instead of the tail. The first 5 decades of aviation was dominated by so called “conventional gear” or tail-wheel aircraft. Visit the “legacy” aircraft flight line at any big air show and you will see rows of Cubs, C-195s, Stearmans, Staggerwings, and Electras. Early airports (like Bowman Field (KLOU) in Louisville, the oldest continually operating airport) were little more than big flat spots where general aviation airplanes could always land into the wind. Their nose high attitude on the ground kept the propeller safely clear of the uneven turf.
With the advent of heavier aircraft the turf was replaced with pavement. By moving the mains aft and propping up the nose of the airplane manufacturers discovered on ground visibility improved and there was a marked reduction in ground loops during those perilous moments between touchdown and chocks. I guess this trend toward metal nose wheel airplanes started in the 1940s with the Bonanza, but I contend it was the 50’s when the Pacer became the Tri-Pacer and the 170 became the 172 marking the domination of nose wheels we still see today.
1960’s – “That’s one small step for man, one giant leap for mankind.” What did President Kennedy’s declaration vowing to “Before this decade is through, we will put a man on the Moon and return him safely to Earth” have to do with general aviation? Well, for one thing, it inspired a generation of pilots (including this one) to get excited about all things aeronautical. But more importantly technology needed to get smaller and lighter if they were going to reach escape velocity. Tubes were replaced by transistors which were replaced by silicon chips. Power requirements were reduced and computing power increased. All these innovations were forerunners leading to modern avionics, smart phones and iPads upon which we rely today. A guy named Hal Shevers started selling portable aviation radios out of the trunk of his Studebaker, a business that gave birth to Sporty’s Pilot Shop.
1970’s – Expansion of the aviation infrastructure. During this decade, the number and quality of airports dramatically increased. Rural communities came to understand that economic development would come on an airplane, not a Greyhound bus. Corn fields became airports. Piper, Cessna and Beechcraft were producing tens of thousands of airplanes a year. As a testament to industrial efficiency, those airplanes were all made of aluminum and had engines built by Lycoming or Continental with mechanically tuned radios mostly from King or Narco. Almost every FBO was a dealer for one of the manufacturers and thousands of us were learning to fly. It is the decade in which I first flew an airplane opening the door to many adventures.
Nowadays, we take out our phone, open an app and receive near real time information on weather and NOTAMS from across the country – courtesy of the internet.
1990s – You are here. Sure, transoceanic airliners and high end corporate jets had inertial guidance and LORAN systems for navigation, but for most of us, navigation and situational awareness was divined by some combination of pilotage, dead reckoning and aligning needles from VORs and ADFs. A competent pilot knew where they were in general, but often, his last known position was the approach end of their departure runway. In 1989 the Global Positioning Satellite (GPS) constellation became operational. The 1990s saw first the introduction of hand held GPS devices into the general aviation cockpits. These incredible little boxes were both accurate and affordable providing both a course line and accurate positioning along it. We marveled at being able to know where we were – exactly. So accurate and reliable pilots would remark, “If it says you are here and you don’t think so, you are wrong!” In 1998 Garmin introduced its GNS-430 Com Navigator relegating the need to align needles to determine a fix to the dust bin of Instrument Flight Rules history.
20 teens – So far it’s the iPad. Only two years old, this decade has seen the nearly ubiquitous acceptance of tablet computers (and their accessories) by pilots. Everything from flight planning, performance planning, weight and balance, cross country navigation, to logging the flight can all be performed on these 10 inch wonders. GPS/ADS-B receivers like the Stratus provide in-cockpit weather and situational awareness for Champs, Gulfstreams and everything in between.
Powered flight is 109 years old. I have been around to see more than half of that. After reflecting on the past, I like to ponder the future and wonder what the next six decades will bring. I offer the following predictions.
The rest of the teens – New engines, new fuels. I predict leaded gasoline will be banned in California. This will lead to the development of new fuels and engines to use them. Cessna introduced its Compression Engine, Jet A burning Skylane at AirVenture this year. Pipistrel has an airframe that will tolerate alcohol in its gasoline. Propellers will become more efficient with new designs and materials allowing us to squeeze more knots from each gallon of whatever we are burning.
2020s – Next Gen goes fully operational. ADS-B in/out technology will allow us to not only know precisely where we are, but where all the other airplanes are around us. ATC can make better use of available runways and offer altitude and speed advisories that will eliminate the need to ever hold at a fix. Unmanned Aerial Systems (UAS) will share the skies with those of us who still desire to fly. Airliners are certified single pilot eliminating the predicted pilot shortage.
2030s – Advances in materials allow airplanes to “morph”. As airplanes have gotten bigger and faster, so has the runway required for them to safely take off and land. My prediction here is that airplanes will not only be able to configure gear and flaps, but the wings and control surfaces themselves, small and thin for high speed cruise – large and thick for slow take offs and landings allowing the largest airliner to operate out of runways less than a mile long.
2040s – Autonomous piloting of both airlines and private airplanes. Aircraft manufacturers are able to eliminate the part that fails the most often. The pilot.
2050s – Teleportation. Just look at an old Star Trek episode.
Happy anniversary.
7 ways to stay informed about Temporary Flight Restrictions (TFRs)
/in Tips and technique/by StudentpltnewsTFR awareness is towards the top of my priority list during flight planning. With today’s multiple forms of electronic communication and flight planning services there’s no excuse for not being aware of a TFR. Here’s a list of resources to make sure a TFR never sneaks up on you.
1. Official Flight Service Station (FSS) weather briefing
Calling FSS at 1-800-WX-BRIEF is the best way to make sure you’re getting the most current TFR information for your route of flight. And if the briefer doesn’t mention anything about TFRs during the briefing, make it a point to if at the end of the call to verify that there are none scheduled anywhere near your planned flight.
2. FAA TFR website
The FAA’s official TFR website is available at tfr.faa.gov. While this isn’t the most user-friendly website out there, the fact that it comes right from the source and doesn’t rely on third party dissemination adds some value. The easiest way to use this site it is to first zoom into the TFR map for the area you’ll be flying (TFRs are shown with red lines), and then select a TFR from the list below the map for all the details.
3. FAA Safety email notifications
One of the benefits from signing up for an account at the FAA Safety Team (FAASTeam) website is the automatic email notifications, including an option to receive alerts for upcoming VIP Movement and their associated TFRs. After signing up for a free account at www.faasafety.gov, click on your email address in the upper right of the screen and select My Preferences and Profile. Here you can specify email options, and you’ll want to check the box next to Selected ATC Notices to receive the TFR alerts. One thing to point out is you will only receive alerts for the region around your zip code, so you won’t get notices for the entire country.
4. AOPA Member TFR email notifications
If you’re an Aircraft Owners and Pilots Association (AOPA) member, I’d recommend signing up to receive their TFR email notifications. To get on the list, email AOPA Member Services at [email protected] and ask to be added to the TFR email alert list. These typically arrive around the same time as the FAA Safety email alerts and have helpful links to both the AOPA & FAA websites for more information.
5. Mobile flight planning apps
Many iPhone, iPad and Android aviation apps incorporate TFR maps and descriptions into their flight planning tools, which is especially helpful since many of us carry these devices with us everywhere we go. I find the ForeFlight Mobile and Garmin Pilot apps especially useful, since they allow you to overlay the TFRs on VFR Sectionals and IFR En Route charts, making it easy to see what airports are affected and how to plan around the restricted area.
6. TFRs on Twitter
Twitter is one of my favorite ways to stay up on current events, and it’s also a great way to keep up on TFRs. One source to follow is the FAA twitter feed (@FAANews), but I find that the TFR info often gets lost with all their other news postings. While not an official source, I like to keep a close eye on the VIP TFR Info feed (@VIP_TFR), which only posts tweets on TFRs and includes a direct link to the official NOTAM on the FAA’s site.
7. In-flight TFR updates over ADS-B
Portable ADS-B receivers have become very popular in the last several months, mainly because they offer subscription-free weather in the cockpit. In addition to providing NEXRAD radar and text weather products, ADS-B also provides near real-time TFR updates in the air. For example when using the wireless Stratus ADS-B weather receiver with ForeFlight Mobile on the iPad, you can see the TFR boundaries depicted on VFR/IFR charts along with your route. This provides great peace of mind in the air to complement the briefings you received on the ground.
Are you grading yourself as a pilot?
/in Tips and technique/by StudentpltnewsBe honest–how would you grade your last flight?
One of the best ways to become a better pilot is easy, free and doesn’t require a flight instructor. Sound too good to be true? Hardly. In fact, you may already do it, at least in some form.
It’s the post-flight evaluation.
Every time you fly, you probably have some gut feel about how well you performed. A solid post-flight evaluation is really just taking this gut feel to the next level. Try to force yourself to review each part of the flight–from pre-flight to landing–in a structured, disciplined way. A good time to do this is on the drive home from the airport, while the details of the flight are still fresh in your mind.
What should you review? Beyond just “that landing stunk,” replay the flight in your mind and go through a quick checklist:
This approach may sound obvious to some, but a disciplined review of your flying can pay big rewards. For student pilots, this is especially true, as you can learn an awful lot without the Hobbs running (which means it’s free). You might set a goal of getting 3 hours of learning out of every hour of actual flying. Some pilots go so far as to re-fly the flight on a home flight simulator or using a cockpit video camera.
The post-flight evaluation isn’t just for student pilots, though. After you earn your license, there isn’t much of a requirement to keep learning other than the obligatory flight review every two years. The safe pilot has a much higher standard than this, though. The impetus is on you to continually get better, which means every flight should be a learning experience. An honest self-critique can also be a great way to ward off complacency, which is one of the most dangerous traits any pilot can have.
Most importantly, it’s vital to do a post-flight evaluation after every flight, no matter how good it was. After all, that “good flight” may not be so good after some introspection.
Performance on FAA Tests and in the Real World – Part 1
/in Tips and technique/by StudentpltnewsPressure and Density Altitude on FAA Tests and in the Real World
Pressure and Density Altitude calculations are key factors in determining performance but these can be confusing. Also confusing is the FAA’s emphasis on precise calculations on the FAA knowledge test when these values are only a part of the total performance equation. I’ll cover some of the other values in the equation in another blog post. In this post, let’s take a look at Pressure and Density Altitude.
The FAA defines Pressure Altitude as the altitude above the standard 29.92″ Hg plane. While Density Altitude is the Pressure Altitude corrected for nonstandard temperature.
Density Altitude is used in computing the performance of an aircraft and its engines. Some manufacturers utilize Pressure Altitude on their performance charts but they address the nonstandard temperature within the chart. In this way, they are actually using Density Altitude but the pilot isn’t required to calculate it.
Variation in Pressure and Density Altitude Calculations
There are several ways that Pressure Altitude can be determined depending on the accuracy and precision required by the calculation.
The Density Altitude value obtained from this chart has some minor accuracy issues when using the standard temperature line. The lower anchor point of the standard temperature line is not set at 15° C for sea level as it should be. This lower anchor is set at approximately 16° C. This error in the chart should have less than 100 feet of error with regard to calculations.
There is a precise and rather involved formula for computing Pressure Altitude with exceptional accuracy. It can be used to calculate the Pressure Altitude out to several decimal places if needed. In general, aviation calculations involving POH values and used airplanes do not require this level of precision or accuracy.
If you are at an airplane, Pressure Altitude can be determined by setting 29.92 in the Kohlsman window and reading the altitude from the altimeter.
Many people calculate Pressure Altitude using the rule of thumb that 1″ Hg change equals 1000′ of altitude change. This rule of thumb is accurate enough for most aviation calculations, as long as you know its limitations. The rule assumes a linear change in pressure with altitude. This assumption is not correct but the answer doesn’t stray far from the truth when the values being calculated are below 10,000′ MSL. The rule, while easy to use, also has a minor inaccuracy as such that 1″ Hg change is not exactly 1000′ of altitude change but this issue should produce less than 100 feet of error per inch of change.
Density Altitude calculations have many of the same issues. In aviation, we use Pressure Altitude and temperature to calculate Density Altitude. Yet, in reality, humidity also has an impact on Density Altitude since water molecules in gaseous form are lighter than the typical molecules in the atmosphere. The more gaseous water (higher humidity) found in the atmosphere, the less dense the air and thus the higher the Density Altitude.
Why do we ignore humidity in common aviation calculations of Density Altitude? Apparently, it was decided at some time in the past that it doesn’t make that big of difference with regard to the performance of the airplane for practical purposes.
Performance Calculations
This brings us back to why we compute Pressure Altitude and Density Altitude in the first place. We want to know how the airplane is going to perform on a given day.
The truth is, you need a safety factor.
One way to build in a safety factor and ease your need to calculate performance to the nearest tenth of a foot is to always round the value. Ignore the rounding rules that you learned in school and round to the next safest value. For example, if your Density Altitude calculation tells you that the Density Altitude for the day will be 3213.65 feet, use 3300 feet or better yet 4000 feet when you go to your POH to calculate your takeoff and landing performance.
You may notice some minor difference in the output for Pressure and Density Altitude when you compare various charts and models of E6Bs. This variation is likely due to the method that the manufacturer selected to compute these values. These differences are generally not significant for practical purposes and should not be a concern.
For the less than practical FAA tests, these differences may mean that you won’t get the exact answer as the FAA. Just use the closest answer and you should be fine. Don’t become overly concerned about this minutia; there are other minutiae on the tests that should have your attention.
In the real world, you are better off rounding up to the next safest value. This does away with things like interpolation on tabular data. It is also a simpler and safer practice.
Keep it simple and stay safe!