Acceptable margin for error in navigation, tests

Discussion in 'Pilot Training' started by LongRoadBob, Apr 7, 2017.

  1. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    I'm trying to learn navigation. I have only a few examples in my textbook.
    I would love to find some quizzes where they lay out the questions and you calculate and check your answer, but I am not finding any such web sites.

    I am trying to be as exact as I can, but notice that my answers can differ from the solution by one or two degrees heading, and a few knots difference (one or two or even more) in ground speed.

    This is the case if I use a ruler and protractor or else the eb-6 variant.

    My question is, is this good enough? Some problems from the book I have redone several times, but I don't know how exact the PPL questions expect one to be.

    I had a similar problem with takeoff distances and fuel consumption using those fuzzy POH diagrams, but there I understood that it was the diagrams. Here I would expect to get the same exact answers, but I always am a little off.

    Is this normal?
     
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  2. Ravioli

    Ravioli Final Approach PoA Supporter

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    the trick on the test questions is that the scale is off a bit for printing... so you can't use a chart and the book (or the test supplement) and get the precise answer. Fortunately the "wrong answers" are far enough from the precision of the printing.

    My initial CFI was pretty good about planning vs flying, and that some of the planning goes out the window when the engine starts.
     
  3. bobmrg

    bobmrg En-Route PoA Supporter

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    Just about everything in flight planning is based on estimates or questionable information, so don't knock yourself out. About the only thing with any vestige of accuracy with which you read the protractor when determining true course. After that things tend to fall apart: The variation on the chart is almost always years out of date, and for vast regions of the country you can fly for an hour or more without the charted variation changing at all....and even then it might be a change of a degree. You can't fly to an accuracy of one degree. So now we have a fuzzy magnetic course and look at the wind forecast. On the knowledge test the FAA will give you a sample Winds and Temperatures Aloft Forecast (FB) to work with. If you fly directly over one of the reporting stations at the exact altitude in the FB at the valid time there is a possibility that the wind forecast will be right...but how often does that happen in the real world? Those forecasts are made twice a day. The knowledge test checks your ability to interpolate between values, nothing more. Take the FB with a large grain of salt.

    Then deviation enters the equation. When was the last time your compass card was updated? Will the darn thing ever settle down so that you can read it more or less accurately? Fat chance.

    Fuel burn? The numbers in the POH are derived by factory test pilot/engineers flying a new airplane with a new engine. Enough said.

    The examiner will want you to explain that you know the elements of flight planning as I have discussed them; s/he will not pore over your flight plan in detail, and when you depart on your planned trip s/he will terminate that portion of the checkride as soon as it becomes apparent that you are going in the right direction. Expect a diversion to an alternate airport and have a plan for that.

    "The book" says that you should hit checkpoints and the destination within five minutes of the planned time (you change your estimates as soon as you experience the real wind, not the forecast wind, of course) but it is seldom if ever enforced.

    Examiners are supposed to accept a flight plan prepared electronically. Go to one of the flight planning sites, enter the details of your trip and print out a flight log. Enjoy.

    Bob
     
  4. jbrinker

    jbrinker Pre-takeoff checklist

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    Bob - this is interesting to me, coming up on PPL check ride. My instructor made me do the nav logs by hand for the first 2 XC's, after that he said I could use a computer prepared one. (I use AOPA's website). For the checkride, I presume the examiner will specify, but if not I can use a computer generated one... For my last XC I did both, prepped manually and did an electronic one. They were very close (using slightly different sources for wind and the checkpoints differed by a couple miles).
     
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  5. denverpilot

    denverpilot Tied Down PoA Supporter

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    FTFY! Haha. Kidding.

    Liked your answer though!
     
  6. ircphoenix

    ircphoenix En-Route

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    For my checkride I did both. And brought my E6B. My DPE wanted me to prove that I knew how to use it.
     
  7. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    Thanks Bob, for the advice, and all of you.

    It's good to hear, and I appreciate the confirmation that in reality it isn't that exact. I understand that but it's good to hear experienced folk say that, and I have no experience as to how much it can and will be different than planned but I assumed always it can be quite a bit. Winds aren't predictable, the compass card may be out of whack, etc.

    But what I was trying to get at was more the written exam part. In my ground school book I haven't yet gotten the answers on the mark. Best I get is one parameter perfect with another (maybe wind heading, or sometimes ground speed, but never both) with one or two degrees or knots difference.

    This is the same whether I use the ruler and protractor or the E6B. I'm very close, but I just don't know if the exam will expect exact. The quizzes at the school do.

    I mentioned the takeoff and fuel consumption because it was similar there. But with headings, I was expecting with the E6B (and I am careful about parallax too, I'm looking directly down at the settings) to match and be exact.

    So, I'm pretty sure in "real life" it is ridiculous to sweat a degree or a knot (given that it is pretty impossible to fly even at these exact speeds or headings).

    As a student, the thing that amazes me most of all, the instruments and their "sloppiness", compass, altimeters, airspeed indicators, etc. but like a carpenter that measures carefully, what is that...I used to hear in factories and worksites "measure with a micrometer, Mark with chalk, and cut with an axe" something like that. That one wants to be exact as possible with the goal, even though things change and one cannot hold exact course or speed all the time.

    I just wonder if answers on the exam will offer "042 degrees 150 knots ground speed" and anothalternative of "043 degrees at 149 knots" etc. if you are close, will you get the answer right?

    Bonus question (with no prize but enlightening a newbie), as I read about how they "swing" a compass (did I get that term right?) when calibrating, and also adjusting CG in the compass for "dip" it made me realize or think that that would imply that if you flew a plane from say Norway, down to Italy, your compass could be off quite a bit more?

    Am I missing something or is that the case? If so, how big an area will the calibrated compass be valid in before it gets way out of whack?
     
    Last edited: Apr 7, 2017
  8. MAKG1

    MAKG1 Touchdown! Greaser!

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    For the written, some of the questions differ by only a few minutes. So, you'll have to make the same approximations and all that.

    IRL, you'll seldom care that precisely. BUT, I don't entirely agree with Bob. He's right about wind forecasts, at least for now. There are sources that can do A LOT better, but that one sucks. With practice, you can nail heading and airspeed, and if the wind is very steady or calm, you can hit targets 50 miles away. And an airplane in good shape can easily make book performance (if you really want precision, plan a little under maximum performance and set throttle to make the planned airspeed), and can exceed it if lightly loaded. Variability in time or space will indeed spoil that, though. But remember, VFR, you only have to hit the target within 3 miles to spot it. That's not anywhere near the kind of precision the written assumes; it's over 5 deg in heading over 30 miles, for instance.

    For the written, you'll have to learn pilot conventions. For instance, it's conventional to assign one wind vector to a given segment. You can do a lot better than that, but not easily.
     
  9. bobmrg

    bobmrg En-Route PoA Supporter

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    Examiners have moved into the digital age more rapidly than some instructors. The thinking now is that the checkride should reflect the procedures that the applicant will use after getting their ticket...no more bright line between training and real life. I'm not denying that value is derived from being exposed to manual planning...heck, I devote several pages in my private pilot book to that subject...but once the basics are grokked they are a waste of brain cells.

    Bob
     
  10. bobmrg

    bobmrg En-Route PoA Supporter

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    Haven't you popped for a test prep guide from one of the many suppliers (I am a supporter of ASA, for obvious reasons)? There should be no guessing about the form that the questions will take. I have looked at the 2017 ASA Private Test Prep book and none of the navigation problems have answer choices as close together as you posit.

    Insofar as deviation is concerned it is based on the aircraft's electrical system and metal structure and it changes with heading, thus the need for a correction card. Doesn't matter where in the world you are flying. Your question sugests to me that you have deviation confused with variation; variation is a function of the earth's magnetic field and changes with location. You will find notations on sectional charts warning of significant compass errors due to magnetic anomalies deep in the earth. You need to do a little reading. Go to www.asa2fly.com and look under Products.

    Bob
     
  11. bobmrg

    bobmrg En-Route PoA Supporter

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    Mustn't forget to mention that the Airplane Flying Handbook and the Pilot's Handbook of Aeronautical Knowledge are available for free at www.faa.gov

    Bob
     
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  12. denverpilot

    denverpilot Tied Down PoA Supporter

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    I was a little stunned when my DPE asked if I had my Commerical flight plan on my iPad as well as the paper chart sitting on the desk.

    I had done up both and cross-checked them with each other so the answer was "yup", since I would be flying with the iPad unless it magically "failed".

    He said to send it to his iPad over the wifi in the office. Then reviewed it there before asking questions.

    I figured it was all going to be a paper exercise. Turns out, the charts went back in the bag and never came back out.

    Doesn't mean everyone's experience will be the same in this regard, but I had the "belt and suspenders" mentality about it, so was prepared to go either way.

    Slightly more annoying later on was having to FLY to an airport quite a ways away to find an ABQ sectional. Everyone everywhere was sold out of them in DEN and a different examiner had said to plan a route down that'a'way... so I finally found one at an FBO halfway to ABQ (Ironic? I flew further along that flight plan to go GET the chart than I flew it the day of the checkride... LOL) and the desk staff chuckled at me when I said I flew all the way down there for a chart, and I'd also probably grab a soda before flying home.

    I call it my $200 ABQ sectional. LOL. Probably expired by now, too. I should go look. Hopefully won't need it again. Might have to go get another one. Haha.
     
  13. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    Hey. I've been away studying and taking the ground school tests online. I was knocked out to find I got 100% right on the last one which had wind triangles, finding compass course, etc. etc. it was multiple choice and my numbers were on the mark this time. Also the first Question where one had to use the circular slide rule, flight computer, and it had four alternative answers with the fourth being "none of the above are correct". It's tricky because it is hard to hit that none of the above, it feels "wrong" somehow, and of I tried I could get some ballpark answers that fit some of the criteria in one of the other alternatives. Pshycologically choosing none of the above seems "wrong" but I did and was right!

    No, I understand the difference between variation and deviation, but deviation has to be checked from time to time, and there is DIP involved as well as when they "swing" the compass it is at a particular latitude, and they make some corrective weights if I understand correctly to even out the variances but that also can cause slight other variations. Dip in the higher latitudes like Norway would be more significant than dips at the equator right? Thy displace the compass center of gravity to best fit the are where the compass swing is done.
    I don't have experience enough to judge how much this would affect, but there is no question that the dip would change, which I could imagine also can change how well the compass takes to stabilize, etc.?

    As for books, I did buy a couple ASA books. My main books though are ground school books in Norwegian which is a second language (learned late in life at 36) and I have to know terms in Norwegian. So for each new term like TAS I have to know in Norwegian it is SFF (Sann Flyfart), GS is BF (bakkefart) etc.

    So I have opposing needs here. I find I have to use English supplemental books to make sure I understand the technical theories, points, especially "nuance" in terminology, etc. BUT I have to make sure I am not learning something that is different about rules, regulations, etc. I picked up Pooleys navigation book, and it is pretty amazing. Best turtorial I have come across for using the flight computer too. I'm getting the hang of it.

    But I also go into th ASA handbook of aeronautical knowledge, and student pilots flight manual. I knew I could download for free (it's great that it is online as well!) but I go through these with highlighter, write in the margins, draw...write in the Norwegian equivalent for terms.

    So far it seems between my actual student course Norwegian books (unfortunately too, black and white) (and in Norwegian) my ASA, and the Pooleys, plus I have your book! For radio communications, and a few others. At times I get bogged down, but find suddenl I get the AHA moments. Still, it would have been much quicker and easier to learn all this in English. I considered going to either USA or England and trying an intense course to get the written out of the way, but I feel like this makes it stick a little better I think.

    Thanks for all the help.
     
  14. MAKG1

    MAKG1 Touchdown! Greaser!

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    100%? Not bad....

    When are you taking the exam?
     
  15. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    I was really surprised at getting all right. I was pretty sure I had some wrong answers in there, and it's progressive, if I got early calculations wrong, all after that would be off. I think it's weird that they treat each progressive answer on its own, when one bad calculation will slew the whole thing off...

    I still have to get through the online courses for my flight school, I think I'm halfway through navigation. Other than the new concepts and theory, there is a LOT of overlap with both weather and aircraft systems, it's hard to read yet again about QNH, QFE, Air pressure, etc. but I have to concentrate in case there is new information, and repatition I don't mind, it helps cement things.

    Anyway, short answer, I don't know. After Nav still have to go through medical, and laws. I dread that one...lots of Norwegian lawyerspeak with no real English version to be able to read to get it in my head. No good alternate sources in English. My plan when I get to that point is to assume it is very similar to the UK and try to root out the differences. I know Norwegian is different from the USA in a number of points.

    I haven't yet understood the differences in the USA between "types" of flight training. It seems to me there is a less taxing, less demanding type of training,and a more rigorous type, but I don't know for sure... yet you all still have to pass the FAA exam? Am I even close to right here? I've heard from local pilots that the Norwegian requirements are more similar to a commercial pilots license requirement in the USA...but I don't know if that is just something they say.

    I do know we have a high failure rate in testing here. There is a consensus that the current system is designed to try and trip you up, but I hear a bit of the same with the US version. It's as if they don't care what you know. But if you can be tripped up. I've learned to take my time and really be sure about what information is given, check that it is all in the same units (or convert) and really think about my answer, so maybe there is a method to the madness.

    It was a hard decision, but I decided to stop flying so that I could concentrate on passing the exam, at least the subjects that would allow me to solo. They are strict here and I was coming up to the point of soloing, but since I didn't meet the requirements, decided to get the exam out of the way ASAP so that when I resume flying lessons, there were no hinders to going all the way. Could plough through and get actual experience. I'm glad for the 10+ hours I have logged. It helps me with theory. I'm a novice.

    There is a chance I am over careful in my training, but I honestly do want to understand as best I can all the salient points. I'm an old guy, so I want to understand what I am doing, how to fly safely.

    After I pass all the online quizzes (I haven't failed one yet, and usually get from 80-96% with an occasional 100%) I'm kind "cheating" in that I answer then check the book when possible. Adjust when I find I had a wrong answer before I send it in, but I learn from that too. Also calculation exercises like with course plotting have worked out well.

    After I pass all, if I do, I will have to take at least 30 hour classroom education, and pass their tests. It is a weeklong course, and I hope it will refresh things I "learned" but may have forgotten now.
     
    Last edited: Apr 13, 2017
  16. MAKG1

    MAKG1 Touchdown! Greaser!

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    I don't know if this is helpful or not, but might the Norwegian rules be the same as the UK? They have unified ATC, right?
     
  17. mtuomi

    mtuomi En-Route

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    The EASA QB's are available online, so there's no need to snakke norsk to study them.
     
  18. Rykymus

    Rykymus Line Up and Wait

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    During my PPL I actually did both paper logs and mechanical E6B, and then computerized flight plans online, and with FF. I always did the paper logs first, so as to be sure I knew what I was doing. Then I used the computerized flight plans to check my work. Most of the time, they were close enough to not matter. But a few times the differences between my paper flight plan and FFs flight plan were enough to cause me to check my work. I remember one time finding that I had used statue miles instead of nautical miles by inadvertently using the wrong scale on the plotter. I think using both is a good self-teaching tool.
     
  19. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    Another question I have now on cross country planning.

    In most cases, how close do you generally find the actual times vs. planned?
    I ask because in my textbook they give an example flight where the takeoff is delayed but once in the air the pilot is seeing at the first checkpoint he is +1 min, at the next +2 minutes from planned and thereafter it pretty much stays at +2 min. In the example there are clear skies no real weather. I ours have expected even in ideal weather that planned could be off more than this. How realistic is this scenario?
     
  20. jsstevens

    jsstevens Final Approach PoA Supporter

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    Depends on how accurately you 1) Plan and 2) Fly.

    Also, how close together are your checkpoints? If you're going 10-15 minutes between checkpoints, 1 minute is 8-10%. That's pretty bad. If you're going an hour between checkpoints, now we're in the 2-3% range.

    So, it depends (Which, in Dilbert speak, means abandon all hope of a useful answer). I did my 2nd long cross country from KORL (Orlando Executive) to KSJG (Saint Augustine) which, on the day I flew it, was just over an hour and I dog legged out to X04 and then back to KDED (Deland) to stay out of the Class C at KSFB (Sanford). I was within 2 minutes of my ETA for St. Augustine. But I only flew it at 2500' so very little time to top of climb, I had checkpoints every 10-15 minutes on the whole route and I stayed on the course line very well. It can be done.

    John
     
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  21. Matthew

    Matthew Touchdown! Greaser!

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    Don't forget to continuously adjust your calculations in-flight. Planning is great but the real winds will always be different. If you are off by a minute or two on a checkpoint, use that as an opportunity to recalculate your time to the next checkpoint as well as your time to your destination and write it down.
     
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  22. jsstevens

    jsstevens Final Approach PoA Supporter

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  23. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    All great points, thanks. One of the assumptions on the test was that consumption was 41liters/hr, and they pointed out directly that one would use that value throughout, ignoring climb out consumption being more until hitting cruise alt.

    In the real world, when VFR planning a trip do you guys always calculate that climb rate consumption, or only when conditions like density alt. or other factors make you think it might be a good idea?
     
  24. jsstevens

    jsstevens Final Approach PoA Supporter

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    That depends on how high I intend to climb to which is a function of winds aloft and how long the flight will be. For a 60-100 mile flight, I'll usually fly at 2500-3500 feet. So I don't bother. Climb out time is something like 4-6 minutes.

    I also don't push to my reserve on fuel so it's not so big a deal to me. If I was flying 3+ hours, I'd 1) check winds aloft for any level between 3000 and 9000 that would give me best groundspeed and plan the climb (and it's consumption) accordingly.

    John
     
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  25. Vance Breese

    Vance Breese Line Up and Wait

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    In my opinion my way point is my opportunity to find out how I am doing with my flight plan and adjust my estimated time of arrival at the following way points and the final destination so I can decide if I need to make a fuel stop sooner than planned.
     
  26. jsstevens

    jsstevens Final Approach PoA Supporter

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    Exactly.
     
  27. Matthew

    Matthew Touchdown! Greaser!

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    In my training nav logs I would calculate time, distance, and fuel of climb at full rich and Vy. Then a checkpoint for starting cruise time, distance, and fuel calculations at lean. Add 5 minutes for non-towered and 10 minutes for towered destination airports for landing sequences and as long as winds were close to forecast it seemed pretty reasonable.
     
  28. denverpilot

    denverpilot Tied Down PoA Supporter

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    Like someone else said, depends on how long I'm going to be climbing. Long climbs are brutal on both fuel burn and speed.

    Also I tend to do a little fudge factor for descents, and plan them as if I'll slow down a bit but not use less fuel, then in the real world if there's no turbulence I'm going to leave the throttle up and probably push up to the yellow arc. Might as well get there. Didn't buy the airplane to go slow.

    But in turbulence I'll slow down. If it gets nasty enough, slowing to Va turns my airplane from a 11-13 GPH airplane into a 9-10 GPH airplane but I'm also not going anywhere fast. So there's one real world scenario where you may be doing a few major recalculations "on the fly". ;-)

    IFR is a whole different story. I'm going to try to take a reasonable guess at where they're going to vector me all over hell and back. And then still carry more fuel. Lots more fuel if I can. And usually I can. Plus the airplane will ride better if it's bumpy with full tanks.

    And then there's my rule that I will not land without an hour in the tanks in my airplane. VFR minimums are a bit light for my tastes and with our long range tanks it's exceedingly hard to measure that accurately unless you started with them completely full. Being off by a number of gallons even with a calibrated stick isn't uncommon.

    The planning is more to see if something is going seriously wrong with the planning itself as much as it is trying to get it dead on. One should always debrief the flight to yourself and see if everything matches up. If it doesn't, stop and figure out why. Once you can line up what happened in the real world to what's on the paper with reasonable reasons, then the flight it truly over. Sometimes it takes ten seconds to figure out, other times...

    One flight, two pilots who know my airplane well in the cockpit. Landed. Sticked tanks to see how much to put on because we were flying very heavy. Couldn't take a full load of fuel. Sticks showed 1/2 left in the tanks and we had planned and agreed that we were landing with an hour. Next leg was also at night.

    A mystery of missing fuel and another long night leg ahead. We stopped. And sat down. And grabbed the flight log and POH. And thought for a bit while we ate something from the airport vending machine in Iowa and sipped on Diet Cokes.

    Scratched our heads for a bit (beginnings of fatigue was also a factor but not huge... just a long leg in the airplane) and realized a low cloud layer had kept us 3000' lower than we intended and the engine burnt two gallons per hour more at that altitude at WOT (still within power limits) and also flew a little faster.

    In the end it burnt 6 more gallons than we planned for, and we arrived slightly ahead of schedule. Both items together showed what had happened after we thought about it for a while.

    If we were the types to plan it down to VFR minimums, and cut it that close, we may have found ourselves landing in a field a mile away from the destination airport. People have done that. Higher fuel burn than expected can be insidious.

    With our "one hour minimum" rule it became an eye opening event but not a dangerous one. We got a lesson in flying our airplane down closer to sea level. It burns a consistent 11.5 GPH up here at our usual cruise altitudes. Down there it was burning 15. We had planned for 13. The plan was flat wrong. Neither of us forgets it now.
     
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  29. dmspilot

    dmspilot En-Route

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    That example from your book isn't unrealistic. On flights less than 100 miles the time is usually accurate within a couple minutes. This assumes you plan TAS based off of real-world data rather than POH optimism. The heading is usually where more error lies (it's harder to fly straight than at a constant speed, compass deviation could be off, gyro could have drifted off, etc).
     
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  30. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    Thanks guys, the answers here were very instructive. It helps me prioritize and know a little more about the factors that need consideration, and what I can expect. I've gotten a lot of help here since I joined and am very glad for that.
     
  31. hockeyrcks9901

    hockeyrcks9901 Pre-takeoff checklist

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    The chief instructor at my school told me this exactly this weekend during our mock oral. He said that the DPE he has been using not only is okay with modern technology but she encourages it! I'm fully comfortable planning a flight on paper manually but will be using Foreflight for my checkride with an iPhone backup and FltPlan Go on my Android as a backup.

    As close as I can remember his exact words were "She wants to test students using the way they will use after taking the checkride."
     
  32. LongRoadBob

    LongRoadBob Cleared for Takeoff

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    I can only speak for myself, but I definitely benefit with better understanding by plotting on paper. It's a similar thing though, plotting on paper gets me a better feel for what and why, and how. Still, in a recent quiz on Xcode flight planning, I used the E6B, but to check my answer, drew a few wind triangles. All checked out, and I was satisfied I had used the E6B correctly. It could be argued the E6B being a type of computer is not different really from plugging in on the EFB. I do think plotting at my stage helps me also with estimates on the fly. That it trains me to better estimate and that helps me feel more confident when the answers or values are near what I expected.

    Where I am, I believe we can use E6B and or ruler/protractor but not electronic on the exams.
    I hope to and plan to (first build up, then...) keep up my skills on both those methods, if only as backup.
     
  33. FastEddieB

    FastEddieB Final Approach

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    Back before GPS, I had to fly long overwater legs using nothing but a calculated heading.

    If I'm recalling correctly, 1┬░off means 1 mile off over a 60 mile leg. Since one can and should usually flight plan legs shorter than 60 miles, even if a few degrees off should still result in being within sight of a checkpoint if heading has drifted or if winds are different than forecast.

    It was still a relief when the next island came into view after as much as an hour out of sight of land!
     
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  34. MAKG1

    MAKG1 Touchdown! Greaser!

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    If you want accuracy, plan for a specific airspeed less than maximum performance, and maintain it.

    You can do very well, but full throttle will not yield a predictable speed. You're at the mercy of rising and descending air.
     
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  35. Matthew

    Matthew Touchdown! Greaser!

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    Another tip: Choose landmarks slightly off to one side of your course. If you mark something on that course line there is a pretty good chance your cowl will hide it from view.
     
  36. danhagan

    danhagan Pattern Altitude

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    Mine are very close. But these practices are for your test and to insure you have the concepts before changing over to automation. Later, after flying awhile, you'll know every little landmark within 200 miles of the home drome. You'll see massive headwinds that totally destroy your fuel plan, but will know how to use your instruments (fuel totalizer and G530) and will know in about .4 of a second if an additional fuel stop is needed.

    You can ... but if you have your own AC you'll know your taxi and climb burn rates. Training in a C152 and changing to a Grumman Tiger totally spoils. The Tiger, properly leaned between 8500-9500 MSL usually burns about 8.8 per hour with 51 gallons useable (most bladders will require a stop before the fuel tanks do):confused::p I still pad the flight plan calculating at 10GPH fuel burn. At lower altitude it is at that rate and if I'm flying from West Texas to lower altitudes, I expect a higher fuel burn if I don't stay high.