Takeoff Performance Spreadsheet instead of Graph

midlifeflyer

midlifeflyer

Touchdown! Greaser!
Joined
May 25, 2006
Messages
17,189
Display Name
Display name:
Fly
I'm sure this has come up from time to time but I figure there may be something new. The real-world accuracy of the book numbers aside, has anyone found a way to convert takeoff performance graphs into a spreadsheet or a Cessna-style table? (And no, don't tell me about spending an extra $100 on ForeFlight for the bizjet package.)

Here's an example. This is the airport altitude/temperature end of a Mooney Ovation (1st Gen) takeoff performance chart. Short or printing it out and adding a whole bunch of extra gridlines, entering an airport altitude of, say, 250' msl is close to a crapshoot; nothing more than a WAG. There's gotta be a better way to do these.
upload_2019-9-1_10-40-26.png
 
I used to do a lot of digitizing of charts to tables at my last job. We used an internal program to do it but this free one looks like it might do the trick.

https://sourceforge.net/projects/plotdigitizer/

Once you get the raw data you can generate polynomial equations for the curves and use those to interpolate the points you need. Use one result as in input to the other formulas.

It can be done but it would take a little work.
 
Haven’t seen anybody digitize them into numbers who wanted to share how, liability and such.

But a piece of old fashioned overhead projector film with two permanently affixed and perfectly square nice thin lines on it, will make using them a whole hell of a lot easier and likely more accurate.

Then the question becomes...How accurate do you want to be if you’re going to add a percentage for “mom and the kids”, and how much do you trust that chart? :)

Measure with a micrometer, cut with a chainsaw.
 
I’d measure with a micrometer, take some baseline numbers, compare them to my actual performance, and get one of these:
https://www.sportys.com/pilotshop/takeoff-performance-computer.html
More precise, probably more parameters for better accuracy, and you can get real world numbers instead of test pilot numbers.

As a background point, one of the jets I work with is all tabulated data...2 1/2 three-ring binders full of numeric interpolation. I’d rather have the graphs.o_O
 
Not exactly spreadsheet but there is an app about $15 that will draw that with numbers once you plug in the data on the same POH page. It’s aircraft specific and only works of iPad that I know of, called gyronimo
 
denverpilot said:
Haven’t seen anybody digitize them into numbers who wanted to share how, liability and such.

But a piece of old fashioned overhead projector film with two permanently affixed and perfectly square nice thin lines on it, will make using them a whole hell of a lot easier and likely more accurate.
Click to expand...
I actually figured out a way to do that. I took images of graph paper and a transparent image of the takeoff performance graph and layered them. As you say, it helps. And it's still not a micrometer!
 
Somedudeintn said:
I used to do a lot of digitizing of charts to tables at my last job. We used an internal program to do it but this free one looks like it might do the trick.

https://sourceforge.net/projects/plotdigitizer/

Once you get the raw data you can generate polynomial equations for the curves and use those to interpolate the points you need. Use one result as in input to the other formulas.

It can be done but it would take a little work.
Click to expand...
I'll have to check that out.
 
WannFly said:
Not exactly spreadsheet but there is an app about $15 that will draw that with numbers once you plug in the data on the same POH page. It’s aircraft specific and only works of iPad that I know of, called gyronimo
Click to expand...
A few notes about the Gyronimo app.

Pros:
Very nice presentation and covers WB, takeoff, climb, cruise, descent, landing and rollout
WB is fully configurable, great graphical demo for student pilot after they learn to work actual numbers
The kids thought it was cool during YE flights while waiting.
Very nice for short field takeoff and landing calls.
Very nice for fuel and speed from takeoff to landing. Allows winds, altimeter, temps, etc.

Cons:
Only available on iOS.
You do not enter the data discussed in this thread, there is a dedicated app for each model with the Poh numbers baked in. If your model is not supported there is no way to customize
A few bugs such as they allow MP entries at altitudes where that MP is not possible

If the OP wants tables of numbers this app would disappoint. If however you just want those old tables interpolated for you, you might really like it...provided the poh listed out the scenarios you are interested in.
 
Our maintenance folks used to say measure with a micrometer, mark with a can of spray paint, then cut with a fire axe. Keep in mind all GA piston engine performance data is not something to bet your life on. Always do the math but realize you better apply a fudge factor and as the saying goes when in doubt don't. Some day when you have time and budget load your airplane different from your normal configuration. Normally two folks up front try close to gross and definitely toward (but not past!) aft cg. Be prepared for an a interesting ride.

C-310s and Aztecs really drove this home for me. The 310 was fast and fun when light but demanding and fickle when loaded. Sweet ol Aztruck was a little slower when loaded but virtually no change in handling. Potentially interesting tidbit, one each 310 and Aztec that we used out in Hawaii were former DOD aircraft. The 310 was a U-3 while the Aztec (N5076U) was a U-6 I think, been a long time ago. Still get a smile remembering picking up IFR clearances in pidgeon english...eh 76uunniiiform gottem one IFR Hilo for you brudder.
 
Seems like an interesting project. Few years ago I created an excel flight planner which outputs all of the headings and such needed for a Nav log. That in itself was a challenge but works for any airplane. For this you would need to build a specific profile for each variation.

The math is different for each. Something to think about.
 
woodchucker said:
Seems like an interesting project. Few years ago I created an excel flight planner which outputs all of the headings and such needed for a Nav log. That in itself was a challenge but works for any airplane. For this you would need to build a specific profile for each variation.

The math is different for each. Something to think about.
Click to expand...
I did a similar Excel flight planner years ago, including an airport and VOR database. Regularly do weight and balance ones. And I've been playing with this spreadsheet project for a while. Yes, the numbers are going to be different for each make and model. I've actually gotten as far as lookup tables using the ISA numbers taken from the graphs, some interpolation, and application of conservative rules of thumb for things like weight reduction. (I won't share; aside from being a work in progress, it's ok for me but my confidence level is too low to pass on to others.)
 
you do realize those curves came from.....actual flights from a test pilot....and were plotted?
 
Sporty’s has a T.O.P. computer. It’s a slide rule that inputs temp, PA, runway type & slope, wind, weigh, etc. All you need to know is the plane’s take off distance at sea level and standard atmosphere.
It’s proving fairly quick and accurate. Using a GoPro with gps to verify.
Of course it has a standard bs disclaimer to add 50%.
There is also no correction for humidity and temps are in 10 deg F steps.
 
I'd commission a math major to knock them out. Could get it for as little as a real meal!
 
manac said:
Sporty’s has a T.O.P. computer. It’s a slide rule that inputs temp, PA, runway type & slope, wind, weigh, etc. All you need to know is the plane’s take off distance at sea level and standard atmosphere.
It’s proving fairly quick and accurate. Using a GoPro with gps to verify.
Of course it has a standard bs disclaimer to add 50%.
There is also no correction for humidity and temps are in 10 deg F steps.
Click to expand...
I've had a TOP for a few decades. It would interesting to see the formulas it is using.
 
midlifeflyer said:
I've had a TOP for a few decades. It would interesting to see the formulas it is using.
Click to expand...
I’m sure most of it is the standard engineering formulas used to create POH data.

What I did figure out was 7% for turf, 10% for grass, and I think something like 17% for long grass.

Never did find official definitions for those, but I could look at what was growing and figure out what would be accurate.
 
TOP uses a temp and pa curve.
Everything else is just a percentage
 
MauleSkinner said:
What I did figure out was 7% for turf, 10% for grass, and I think something like 17% for long grass.
Click to expand...

City slicker question: what's the difference between "turf" and "grass"? To me, those are synonyms.
 
kath said:
City slicker question: what's the difference between "turf" and "grass"? To me, those are synonyms.
Click to expand...

Think like manicured stuff or stuff with very little grass and lots of dirt for turf.

Grass will be thicker. Maybe mowed but not mowed way dow to like, a golf green height.
 
kath said:
City slicker question: what's the difference between "turf" and "grass"? To me, those are synonyms.
Click to expand...
Turf is defined as grass and the layer of soil that is held together by the grass roots. I’m not sure of MauleSkinner’s usage, but my guess is that he is contrasting ground that is evenly covered by grass that gets mowed and doesn’t have clumps, probably human-planted and -maintained (turf) from ground that is unevenly covered in clumps of grass, naturally occurring and possibly mowed, grazed. or cut for hay (grass).
 
kath said:
City slicker question: what's the difference between "turf" and "grass"? To me, those are synonyms.
Click to expand...
See the part of the post you didn’t quote.

POH corrections that I’ve seen are the same...7% for turf, 10% for grass.
 
iamtheari said:
Turf is defined as grass and the layer of soil that is held together by the grass roots. I’m not sure of MauleSkinner’s usage, but my guess is that he is contrasting ground that is evenly covered by grass that gets mowed and doesn’t have clumps, probably human-planted and -maintained (turf) from ground that is unevenly covered in clumps of grass, naturally occurring and possibly mowed, grazed. or cut for hay (grass).
Click to expand...
My usage is from the T.O.P. Computer, POHs, AFMs, etc., that use those terms.
 
Last edited:
MauleSkinner said:
My usage is from the T.O.P., POHs, AFMs, etc.
Click to expand...
After I responded, I noticed that you mentioned not finding an official definition. I also looked a bit. I tried Googling turf vs. grass and all I learned was what kind of owies to expect if your kids play soccer on artificial turf vs. natural grass. That's when I gave up and checked the dictionary, which led to my previous post.

Now I've checked FAA sources. Searching for "turf" doesn't get any results in the iPhone FAR/AIM app and "grass" comes up with two hits: AIM 7-5-7's comment about tall and wet grass affecting the rule of thumb that says you should have 70% of your liftoff speed by the time you use up half the runway; and the Blue Grass airport in Kentucky mentioned as a class C airspace area in AIM 3-2-4. So there is apparently no official definition. I haven't seen both terms used with apparently contrasting meanings in a specific POH or AFM that comes to mind, but I've only read a couple of those so I'm not a good source of data regarding them.

Then I checked the A/FD entries for airports with grass runways that I've visited. None was listed as having a surface of "grass." I saw 1 "Turf in Poor Condition," 9 "Turf in Fair Condition" (two of which are being pretty generous with that description; don't buy any baseball cards in those towns!), and 8 "Turf in Good Condition." One of the "fair" turf runways mentioned "numerous grass clumps" in the remarks but that was the only mention of "grass" that I saw.

So it seems to me that "turf" is the word in use to describe any grass runway surface. I wonder if the POH/AFM references to "grass" you've seen are just subjective descriptions of turf that needs to be mowed one of these days and "long grass" is turf that is way overdue to be mowed. I suppose a manufacturer is free to test performance however they want when it comes to things like this.

For posterity, welcome to POA. Instructions for use: Pick an obscure topic you want to learn trivial facts about. Post a thread about something completely unrelated. Then wait for results. :)
 
A great Youtube comparing a Bonanza and Skylane to their respective POH take-off & landing performance numbers.

Makes a pilot remember why their CFI probably said add 30%-50% to POH numbers for flight planning.

 
Checkout_my_Six said:
you do realize those curves came from.....actual flights from a test pilot....and were plotted?
Click to expand...
In a sense, but not before a lot of data massaging and corrections to get everything standardized and corrected to conditions on the charts. More likely these days the perf numbers were generated from a mathematical model/simulation and validated through flight test. Given that you already have a source for the data, it's faster, cheaper, and probably more accurate to just digitize the plots.

Nauga,
from both sides of the equation
 
NordicDave said:
A great Youtube comparing a Bonanza and Skylane to their respective POH take-off & landing performance numbers.

Makes a pilot remember why their CFI probably said add 30%-50% to POH numbers for flight planning.

Click to expand...
Unfortunately many pilots’ technique is so far from the technique used to build the charts that 50% often isn’t enough.
 
MauleSkinner said:
Unfortunately many pilots’ technique is so far from the technique used to build the charts that 50% often isn’t enough.
Click to expand...
That’s why building one’s own chart takes all their techniques into account vs the expert test pilot.

...and +\_ 50ft is probably close enough... no need to get all mathematical when you’re not going to be all that good at repeating it.
 
Checkout_my_Six said:
That’s why building one’s own chart takes all their techniques into account vs the expert test pilot.
Click to expand...
Performance charts should represent the performance of the airplane, not the pilot.

Nauga,
and another 40 hours in the W/delta box
 
nauga said:
Performance charts should represent the performance of the airplane, not the pilot.

Nauga,
and another 40 hours in the W/delta box
Click to expand...
They are useless if you can’t fly it. It’s a package deal bro....
 
You must log in or register to reply here.
Back
Top