Time, Fuel and Distance to Climb calculation: Assistance sought please

Discussion in 'Pilot Training' started by BarryJI, Feb 8, 2020.

  1. BarryJI

    BarryJI Filing Flight Plan

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    First post, thank you for your hospitality.

    Eventually I will probably manage to drive the calculations using the C-172 POH into my thick head but I am struggling; math is my weakness. Does anyone know of either a computerised process for calculating these numbers (there's no such category in Sporty's E6B for iPhone) or a really good step-by-step explanation, online or in a document, for the mathematically challenged? I am struggling a bit with the process. Many thanks.
     
  2. murphey

    murphey Final Approach PoA Supporter

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    Climb takes more fuel. Descents take less fuel. In the end, pretty much evens out.
    As for the time, assume 500 fpm for this discussion, whatever speed that takes.
    To go from 5000 agl to 10,000 agl is 5000 ft.
    Climb distance divided by climb rate or 5000 ft/500 ft per min = 10 minutes.
     
    Last edited: Feb 8, 2020
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  3. woodchucker

    woodchucker Cleared for Takeoff

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    Mind if we know where you are in piloting? Are you a student pilot? If so you will pretty much need to know how to use the cardboard E6B or an approved calculator like a CX-3. Other than that though it’s pretty much d=rt. You know the measured distances from the sectional, and you calculate ground speed based on the back of the E6B. During flight you check actual ground speed using either gps or the distance and time of the leg just flown and use d=rt again. Very useful to do that to ensure your planned fuel will get you to where you need to be.
     
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  4. BarryJI

    BarryJI Filing Flight Plan

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    Thanks, guys. @woodchucker, I’m not a student pilot but a Private Pilot with ~400 hours VFR in type and a lapsed IFR rating. I stopped flying 20 years ago when child #1 arrived and have just started retraining. I’m in Southern California. I am trying to be competent in all aspects of old-school flight planning (albeit with digital E6B) before I get into computerised flight planning. I am surprised not to have found climb and fuel burn calculations in digital form.
     
  5. murphey

    murphey Final Approach PoA Supporter

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    One reason is that different aircraft, even the same aircraft, have different climb speeds, hence different fuel use. If I climb at 80 kts I'll use less fuel than at 100 kts.
     
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  6. woodchucker

    woodchucker Cleared for Takeoff

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    Gotcha! Just wanted to ask to see how to best answer your question. Like @murphey pointed out climb and descent pretty much balance out so it’s still back to just knowing cruise fuel burn for altitude and power settings to plan point A to B. Once past primary nobody asks to see TOC and TOD calculations, at least in my experience.

    If you are somewhat handy with excel you could probably create your own computerized version though.
     
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  7. smv

    smv Pre-takeoff checklist

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    Although I admire your desire to regain your grasp on the "old school" methods, if you are actually planning on going EFB in the end, it might be best to direct your efforts in that direction. IF you need to calculate TSD in the cockpit, do you honestly see yourself reaching for an E6B or are you going to simply punch in your destination on your EFB device and go with those numbers? In all honesty, the only time I touch paper charts or use an E6B these days is when training a Student how to use them long enough to pass their checkride.

    Edit to add: Although I do still print out any IAPs and airport information sheets I expect to need before departing on a cross country flight, it has been years since I purchased a paper sectional, Low/High IFR, Chart Supplement (formerly A/FD), or worked an E6B outside the training environment.
     
    Last edited: Feb 8, 2020
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  8. murphey

    murphey Final Approach PoA Supporter

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    About the only time TOC and TOD are really critical is if you’re a dispatcher and need to make sure the fuel load is correct for the flight based in weather and such.
     
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  9. woodchucker

    woodchucker Cleared for Takeoff

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    Well, out of boredom I just made an excel TOC calculator for the club 172. Just need to input three variables ... takeoff elevation, TOC elevation and temperature. This is assuming zero winds per POH.
     
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  10. WDD

    WDD Pre-takeoff checklist

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    ForeFlight seems to do a nice job of all of this automatically.
     
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  11. AKBill

    AKBill En-Route

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    I cheat. Use 10gph instead of 8.5gph actual, min 1 hour reserve and watch the clock.
     
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  12. Brad W

    Brad W Pre-takeoff checklist

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    i'm in a very similar boat, knocking the rust off I mean...... but 16 years for me.

    I've been spending some time with the old POH.....weight/balance numbers....
    and some time with the Garmin Pilot app free trial.

    I like the previous suggestions from a practicality standpoint....but to answer the question if you really want to deep dive into old school math....My advice....
    I think the best way is with pencil and paper.
    write variables...
    distance, speed, time, etc...
    break it down into segments (climb, cruise, etc.) ..... draw pictures or whatever to get your head into it. Figure out each piece. not as complicated in smaller pieces.
     
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  13. dtuuri

    dtuuri En-Route

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    You mean using this chart ?

    C-172 POH.JPG
     
  14. WDD

    WDD Pre-takeoff checklist

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    For my practical I dug into these poh tables and made a nice little excel spread sheet

    I did it because the DPE needed to see all it

    I’ll probably never use it again because all the ForeFlight and what not apps all do this automatically.
     
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  15. Jim Carpenter

    Jim Carpenter Pre-Flight

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    Using the Cessna chart, such as dtuuri shows above, the basic routine is:
    Read across the table for the values shown at your top altitude, realizing that those numbers start from sea level.
    If starting from other than sea level, read across the table for the values at that starting altitude.
    Then simply subtract those starting altitude values from the top altitude numbers. Appropriate adjustments for pressure altitude and non-standard temperature are applied as noted on the table. Further, if altitudes to be used are (most likely) not even thousands, interpolate the numbers for in-between altitudes.
    Search youtube, lots of mini- ground school lessons available for viewing.
    And, as everyone has noted, these calculations may be built in to flight planning apps, and they may use some average speed and fuel burn profile for your aircraft.
     
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  16. BarryJI

    BarryJI Filing Flight Plan

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    These responses are very helpful, many thanks. I am comfortable with tech, so, given my lack of comfort with math, common sense suggests that I should do this sort of thing with ForeFlight ASAP rather than trust my own calculations. A part of me wants to be able to understand it well enough to be able to figure it all out on the fly but, as I said, I am hearing the voice of common sense reminding me of my limitations. Of course, here in southern CA, an iPad can overheat in the summer, so I intend to have some sort of navigational backup and good SA on cross-country flights that are not completely familiar. And, after my 20-year hiatus, I'm delighted to see GPS in the cockpit, too! So, even though I will try my best to convince my CFI that I can do the numbers, he and I both know that ForeFlight will be the go-to option in the end. Thanks again for all the sage counsel.
     
  17. Ravioli

    Ravioli Final Approach

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    Dear God, let this be a joke.

    Do NOT EVER place your fate on an app. If you actually don't understand the calculations for your aircraft you should stay on the ground where your are safe.
     
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  18. dtuuri

    dtuuri En-Route

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    Um, other than for a math teacher using this chart on an interpolation exam or FAA written test, you only need to have a conservative mind in real life. Just use the value for the next higher cruising altitude and subtract the value for the next lower departure elevation. That puts the difference in fuel consumption from the theoretical correct answer — in your tank. Chances are that won't even be enough.
     
    Last edited: Feb 9, 2020
  19. BarryJI

    BarryJI Filing Flight Plan

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    A little over-emphatic, I think.

    Of course I understand your point but a lot depends on the kind of flying one does. For me, it’s all fair-weather, low-stress VFR. I would never rely on an app for all flight-planning, navigation and situational awareness; I am too experienced for that.

    I think if you want to be helpful you should consider moderating your tone. I appreciate help but I don’t need a lecture replete with sarcasm.
     
  20. murphey

    murphey Final Approach PoA Supporter

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    Cessna has a great collection of tables for practically every situation. Piper, on the other hand....naught. A few graphs which if I were to religiously adhere to them, I'd never fly because most never go past 7000 msl.
     
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  21. murphey

    murphey Final Approach PoA Supporter

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    1 gal for taxi
    12 gal for climb (sometimes, even 11) I've got a JPI engine monitor and can see exactly (if you believe it) fuel consumption (I always believe on the high side)
    10 gal cruise (in reality, 8.5-9 gal but again, I always assume worst case)
    7 gal for descent.

    Comparing my real numbers (total fuel from engine start to shut down) against the JPI, I use about 8-10% less fuel than the JPI indicates. So if I plan using the JPI numbers, it's a warm fuzzy feeling. But I don't. I use my more conservative numbers.

    Example: From ground (6500 msl) to LaVeta Pass (9000 msl but I cross at 12.5K msl) I was burning 13 gph with the mixture properly leaned and climbing 500-700 fpm. However, on the far side down to KALS (Alamosa), I was seeing 3.5 gph. Frankly, I pulled the mixture back ( engine never coughed or stumbled) and basically glided down. In a cherokee. You know, a flying brick. At about 2K agl I put in more mixture. Really wanted to see the effect on altitude and what would happen in an emergency if I lost the engine.

    Update: The stated numbers are what I use for flight planning. I have more than 10 years of JPI numbers (all phases of flight) that I can compare against. But I still use my conservative numbers for planning. Has kept me out of trouble for many years.

    Note on FF: Putting in the characteristics for the aircraft, FF will generate estimated times and fuel consumption for each phase and leg of flight. I haven't bothered to check against my JPI numbers because I don't really care. Those types of numbers are more relevant and needed for the high-performance and jet aircraft than our bugsmashers.

    I don't trust software. 'Specially the software I write!
     
    Last edited: Feb 9, 2020
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  22. WDD

    WDD Pre-takeoff checklist

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    Yeah! And he's probably one of those hipsters who also think it's safe to use a battery powered calculator. If he doesn't understand how to use an E6B paper wheel and an abacus, he's doomed...... DOOMED...

    And get off my lawn!
     
  23. LB 408A

    LB 408A Filing Flight Plan

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    "Of course I understand your point but a lot depends on the kind of flying one does."
    My plan is to be flying in a manner that will save your life and mine. I'm just a LSA student so I will always be flying so I can see the ground under 10 K agl and ending the flight with a half hour minimum in the tank at tie down. Precision flight planning can be best done on the ground. Segments of flight should be calculated and then proved by practice and memorized.
     
  24. WDD

    WDD Pre-takeoff checklist

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    We're all united with you on that. A few thoughts.

    30 min is a bit light on reserve.

    And you have to think about precision. You can spend hours using the POH tables and various calculations. But a lot of variables come into play. How old is the engine? How efficient is it? What kind of prop do you have? (Lot of schools put a high pitch prop on for climbing power, which cuts back on the cruise per RPM). How old is the plane? Panels that don't fit as tight as they used to, no skirts on the wheels, etc. Has the school or flight club added a high flow exhaust? All of these variables change things a bit.

    I've used the POH to calculate the start up, taxi, take off, climb, and cruse fuel burn at the cruise IAS converted to TAS (and subsequent GS) the POH says I should have. I've also done the calculations using the fuel burn I've observed the plane having and just use 9 gal an hour, and use the IAS I've personally seen for the usual RPM. The latter method is more accurate.......
     
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  25. Ravioli

    Ravioli Final Approach

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    I wasn't sarcastic at all. You said: "common sense suggests that I should do this sort of thing with ForeFlight ASAP rather than trust my own calculations"

    I said if you can't trust your own calculations, stay on the ground.

    Actual factual. How would you know that the app on your iJunk is correct?

    EX: I should have 2 hours of endurance but the ForeLosers app says I have 3. It must be right, right, cause it costs $100/yr and knows if I put my fuel burn and waypoints in correctly.
     
  26. LB 408A

    LB 408A Filing Flight Plan

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    "30 min is a bit light on reserve."
    Well I kinda agree with that but my thinking was along the lines of when i flight plan it is for fuel used during time flown of climb cruise and distance. My understanding is while flying VFR the FAA wants me to add 1/2 hour at the destination in reserve. I want to have an additional 30 minutes in my tank after that.(when tied down) From lots of hours and miles interstate in a service truck the thought that I should be there already is no time to be looking for a gas station. On the other hand if I look at my flight plan and say to myself I should be there already and i'm not, I only have to think 'I've only got an hour where is the best place to land'. I like the idea of sitting on the ground trying to figure out whether I did sloppy flight planning or sloppy flying and whether or not I like this new airport.
     
  27. Rgbeard

    Rgbeard Cleared for Takeoff

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    Where was the sarcasm?
     
  28. WDD

    WDD Pre-takeoff checklist

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    I believe it was the "Dear God, please let this be a joke. You should just stay on the ground" "Forelosers" "I Junk" Just guessing.
     
  29. denverpilot

    denverpilot Tied Down

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    Before trusting any software in flight, I always sit down and plan a fake flight or two with it and confirm the calculations match mine from the POH.

    If there’s discrepancies they’re usually due to some dumb assumption the programmer made. I figure out what they were thinking.

    Once done, I can decide if I can live with their assumptions. There’s usually a way to use their math in a conservative way.

    Other examples of “surprises” are things like waaaaay back not knowing that ForeFlight always calculates things including the current winds aloft, which is useless if you’re planning and printing out the plan the day before.

    So you look up how to trick it into not using winds and have a nice no-wind plan and update it closer to the flight.

    All software has silly assumptions. Always know what they are. I don’t trust software anymore further than I can throw it, because I’ve done software QA, and sat on Software Release committees and Murder Boards.

    But I can test most stuff and figure out what dumb assumptions the programmer made. Even give a solid educated guess as to why they did it. And then use it knowing its built in assumptions or biases of the developers and design team.