Who runs performance numbers on every flight?

KiteEXP

KiteEXP

Filing Flight Plan
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KiteEXP
I’ve been flying for over 30 years now and know how easy it is to fall into the complacency trap. I wonder how many other low land GA pilots are still using their performance charts after they have passed their PPL check rides? When I owned and operated a 135 operation we were required to have W&B and performance data for each revenue flight but when operating as part 91 flight we never did.

I own a, new to me, 1979 Dakota and keep it hangared at a sea level elevation airport that has a 2500’ strip with obstacles on both ends of the runway.

I’m not generally concerned with the runway length given the performance of the Dakota. However, when I’m taking a full load of people, fuel and dealing with density altitude due to summer heat it’s nice to know the expected performance numbers before launching into the air.

I look at this from two aspects. One, is the plane capable of getting into the air and clearing obstacles safely given the airport and runway environment? Two, is my engine and plane performing as it should, aside from the cursory glance at engine instruments on T.O. roll, to get to Vr compared to what was determined on the performance charts?

I leave a healthy margin of error since I know that my abilities and plane will not match that of what is stated in the POH.

Also, my eyes aren’t what they used to be and I for one get migraines when trying to follow the small lines for the various performance charts in the POH. So I went looking to see if there was an app for the Dakota and sure enough there was.

On a recent flight I added the app to my flight planning procedures and decided what I was seeing was possible but fell out of my comfort zone and therefore elected to modify the W&B. On that particular take off I had something happen which required me to return to the airport. In retrospect I’m glad that I decided to modify the W&B since I really didn’t need the extra stress and workload of “am I going to clear those obstacles or not.”

When I purchased the app from the App store it only came with T.O. performance charts for 0 degree of flaps. I reached out to the developer and asked if he would consider adding T.O. performance charts for 25 degrees of flaps as well. Since the Dakota is not as popular as other Piper models the app hasn’t had a lot of downloads. So there wasn’t much financial incentive to update the app compared to the work required to add the ability I was requesting. I decided to sponsor the upgrade to the app for my own benefit but also hoping it will benefit other Dakota owners and pilots.

The app can’t technically be used for actual flight planning due to liability issues but I’ve known too many pilots who didn’t take the time to consult their performance charts and suffered consequences, in some cases fatal. Maybe they didn’t consult their performance charts due to complacency or maybe it was due to the time it takes to follow those small lines in the POH, we will never know.

However, given that many of us are now using iDevices in the cockpit, these type of apps seems like an obvious addition to our EFB for our safety and peace of mind. The app takes less than 5 minutes to run the performance charts for an entire flight, from take off, cruise and landing.

If you are interested in the app I am using you can find it in the iOS app store under the developers name: Geronimo, LLC. The developer has many makes and models, aside from Piper, that are currently available.

::Note, I am not getting compensated or have any affiliation with the app developer::

Thank for your for your time.
 
Owing a 182 I get spoiled and normally do not run performance data but do W&B (or at least weight) as I run close to gross quite a bit...but I did break out the POH last week taking off from a shorter runway on a warm day at gross just to double check I was well within a safety margin.
 
Depends what the conditions are. If it's a high DA day, close to gross weight, crappy runway conditions, short runway, grass or turf I'm running numbers.
 
I have recently been in the habit of just being familiar with the PC-12 and blasting off with a brief run over the numbers. I was never really comfortable with it. Now, I've started using an PC-12-specific app which runs through just about every number I need to know using base numbers from that aircraft's specific POH. Everything from W&B, CG (takeoff through landing), takeoff and landing weights, takeoff run, Vr, accelerate-stop distances, speed @ 50' agl, time to climb, fuel burn, distance used in climb, cruise fuel flow, total fuel burn in cruise (3 different options for cruise power settings), Vref for various flap settings, landing distances with or without reverse thrust, etc.

I feel a lot more comfortable having these numbers available and briefing them with my co-pilot along with the other information necessary for the pre-departure briefing. It really allows us to plan our flight all the way to the ramp.
 
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Cpt_Kirk said:
I have recently been in the habit of just being familiar with the PC-12 and blasting off with a brief run over the numbers. I was never really comfortable with this. Now, I've started using an PC-12-specific app which runs through just about every number I need to know using base numbers from that aircraft's specific POH. Everything from W&B, CG (takeoff through landing), takeoff and landing weights, takeoff run, Vr, accelerate-stop distances, speed @ 50' agl, time to climb, fuel burn, distance used in climb, cruise fuel flow, total fuel burn in cruise (3 different options for cruise power settings), Vref for various flap settings, landing distances with or without reverse thrust, etc.

I feel a lot more comfortable having these numbers available and briefing them with my co-pilot along with the other information necessary for the pre-departure briefing. It really allows us to plan our flight all the way to the ramp.
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Turbines are a bit different. You kind of need to run the numbers to get your power settings for the day.
 
Cpt_Kirk said:
I have recently been in the habit of just being familiar with the PC-12 and blasting off with a brief run over the numbers. I was never really comfortable with this. Now, I've started using an PC-12-specific app which runs through just about every number I need to know using base numbers from that aircraft's specific POH. Everything from W&B, CG (takeoff through landing), takeoff and landing weights, takeoff run, Vr, accelerate-stop distances, speed @ 50' agl, time to climb, fuel burn, distance used in climb, cruise fuel flow, total fuel burn in cruise (3 different options for cruise power settings), Vref for various flap settings, landing distances with or without reverse thrust, etc.

I feel a lot more comfortable having these numbers available and briefing them with my co-pilot along with the other information necessary for the pre-departure briefing. It really allows us to plan our flight all the way to the ramp.
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It would've been nice to have an app like that when I owned my PC12, #323, but I got pretty good at using the charts when I had to. With the PC12 t's easy to get lured into complacency by the fact of well it performs. I just wished it was a tad faster.
 
KiteEXP said:
It would've been nice to have an app like that when I owned my PC12, #323, but I got pretty good at using the charts when I had to. With the PC12 it's easy to get lured into complacency by the fact of well it performs. I just wished it was a tad faster.
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Very true and I was on that path for sure.

I wouldn't mind flying a P.180. :)
 
KiteEXP said:
It would've been nice to have an app like that when I owned my PC12, #323, but I got pretty good at using the charts when I had to. With the PC12 t's easy to get lured into complacency by the fact of well it performs. I just wished it was a tad faster.
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That's a older series nine /45, or straight PC12?

The Pilatus app is nice for cruise numbers, still think foreflight makes for a better W&B though

image.jpg
 
James331 said:
That's a older series nine /45, or straight PC12?

The Pilatus app is nice for cruise numbers, still think foreflight makes for a better W&B though

image.jpg
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That was one of the first series nine, if memory serves me correctly #320 was the first. I actually picked up the plane new in Switzerland and flew it to KBJC as a white tail so P&I could be completed in the states. Pretty nice trip overall.
 
I have a general information page in my checklists that has runway required numbers for max gross at sea level and a high density altitude. If I am within the parameters I don't run the numbers. If I am butting up to them, I run the numbers.
 
midlifeflyer said:
I have a general information page in my checklists that has runway required numbers for max gross at sea level and a high density altitude. If I am within the parameters I don't run the numbers. If I am butting up to them, I run the numbers.
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This. We have a spreadsheet for our 182 and I know the limit ranges where it's time to look a little closer.

In the twin, I would love an app because the Piper charts are a freaking test of will to try to get an exact number from a horribly designed chart. Hahah. But you can slide your eyeballs across it fast enough to know if you're hundreds or thousands of feet inside limits like accelerate-stop, for example.

You'd be hard pressed to come up with a book number that matched anything in reality on it, too. The single engine climb rate chart is an excellent work of comedic fiction. ;)
 
In the past I thought it would be cool do develop an app that used performance charts, but that you could also adjust based on actual performance, essentially derate the curves based on actual numbers.
 
KiteEXP said:
That was one of the first series nine, if memory serves me correctly #320 was the first. I actually picked up the plane new in Switzerland and flew it to KBJC as a white tail so P&I could be completed in the states. Pretty nice trip overall.
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Now that sounds like a fun trip!

Always liked the lower button layouts on the series 9 vs the overhead buttons on the 10
 
Somedudeintn said:
In the past I thought it would be cool do develop an app that used performance charts, but that you could also adjust based on actual performance, essentially derate the curves based on actual numbers.
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The problem is, the curve may not have moved linearly.

And maybe more of a problem, jacking with the published numbers is sure to be a massive liability someday eventually in a courtroom when some pilot, even one warned that the software is not for legal planning purposes and makes assumptions based upon likely faulty data the pilot themselves added, and a stack of waiver forms they have to sign to even buy the stuff, and whatnot... Screws up and crashes and dies and their family decides to sue everything and everyone in sight.

No way in hell I would publish a damned thing the manufacturer didn't publish or software that would "tweak" their numbers back to reality.
 
denverpilot said:
The problem is, the curve may not have moved linearly.

And maybe more of a problem, jacking with the published numbers is sure to be a massive liability someday eventually in a courtroom when some pilot, even one warned that the software is not for legal planning purposes and makes assumptions based upon likely faulty data the pilot themselves added, and a stack of waiver forms they have to sign to even buy the stuff, and whatnot... Screws up and crashes and dies and their family decides to sue everything and everyone in sight.

No way in hell I would publish a damned thing the manufacturer didn't publish or software that would "tweak" their numbers back to reality.
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I would never let the app improve performance, only reduce performance. It's not too hard to take the performance charts back to some basic aerodynamic formulas and with a few data points adjustments could be made based on derating the engine and increasing the drag coefficient. I've already reconstructed the performance tables for the plane I typically fly in Excel based on the formulas.
 
Somedudeintn said:
I would never let the app improve performance, only reduce performance. It's not too hard to take the performance charts back to some basic aerodynamic formulas and with a few data points adjustments could be made based on derating the engine and increasing the drag coefficient. I've already reconstructed the performance tables for the plane I typically fly in Excel based on the formulas.
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Never said you would. In fact I said you'd move the performance numbers more toward reality.

Lawyers killed Cessna once with a single accident, and they can easily bankrupt an individual coder long before anything ever gets to trial, is all I'm saying. There would be no jury of peers, just folks taught by the media that little airplanes are insanely dangerous who'd be hearing about your code mistakes.

It's all about whether the reward exceeds the risk. Most people won't pay a whole lot for an app that would do the numbers.

I have a few for the 182 that just show manufacturer data and they cost a buck. Some of them the authors have completely abandoned them and removed them from the Apple Store rather than update them to the latest iOS du jour.

I have two abandonware e6b apps that are still in the store and won't even launch without crashing on modern iOS. Complaints on the reviews and reports to Apple that they should be removed, and all. They're still there.
 
Somedudeintn said:
In the past I thought it would be cool do develop an app that used performance charts, but that you could also adjust based on actual performance, essentially derate the curves based on actual numbers.
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There are a couple of Excel spreadsheets floating around that do takeoff and landing performance number calculations. Essentially taking the book numbers, doing an interpolation as well as the warned-against extrapolation, and then adding in a fudge "safety" factor.

I've adapted it for takeoff numbers in the airplanes I fly and it's useful as a ballpark. I guess one could test fly one's own airplane to get their own real performance numbers. But whether ballpark or real, the ones I've adapted are only for me and perhaps to use as an illustration.
 
denverpilot said:
This. We have a spreadsheet for our 182 and I know the limit ranges where it's time to look a little closer.

In the twin, I would love an app because the Piper charts are a freaking test of will to try to get an exact number from a horribly designed chart. Hahah. But you can slide your eyeballs across it fast enough to know if you're hundreds or thousands of feet inside limits like accelerate-stop, for example.
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The Piper-style graph is far more common than the Cessna tables, probably why the (old?) knowledge tests used them. That's actually my reason for the spreadsheet I mention in the other post. It's for the Bonanzas, Pipers and Mooneys I fly, not the Cessnas.
 
Somedudeintn said:
In the past I thought it would be cool do develop an app that used performance charts, but that you could also adjust based on actual performance, essentially derate the curves based on actual numbers.
Click to expand...
The numbers in the book for my ride are basically creative fiction written by the kit manufacturer's marketing department. One of these days (yea, right) I should generate some real numbers.

(But, given that I can do a stop and go in less than 1000 feet, I'm good to go anywhere you can get a Cessna in and out of so the motivation to actually get on this is somewhat weak.)
 
Capt. Geoffrey Thorpe said:
The numbers in the book for my ride are basically creative fiction written by the kit manufacturer's marketing department. One of these days (yea, right) I should generate some real numbers.

(But, given that I can do a stop and go in less than 1000 feet, I'm good to go anywhere you can get a Cessna in and out of so the motivation to actually get on this is somewhat weak.)
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I don't really have to motivation right now either. To answer the original question, I don't run the numbers unless I might be close. Me solo flying into a 4000ft or longer runway in the 172 near sea level, I know I'm good.
 
Kite: I always ran the numbers as I spent most of my training time in central Texas during the summer. I ran them enough that I could determine whether I could make the hop by just knowing the current and expected high temp for the flight time and what the fuel load was on the airplane I was taking. If I didn't have enough capability to get out of Killeen without using more than 2000' ( runway was much shorter back in '82), then I scrubbed.
During the summer of 1980, it was so hot at our campus in Waco, that a C-150, with a 150 hp conversion, 5 gallons of gas and a 90 pound pilot needed over 5500' get off the ground...school canceled all flight activities for a couple of months due to the heatwave.
 
Wow those Geronimo apps look awesome...just don't want to spend $13 until I know which model of plane I will be flying most the time
 
I don't, but then I don't fly from 2,500' strips or higher altitude airports. For me a short runway is under 5,000'; almost every airport I fly to has one or more 5,000'+ runways. If I were going somewhere with a 2,500' runway I would definitely run the numbers for that as it's well outside of my normal experience.

When I'm flying a "new to me" aircraft I run the numbers for W&B to get a good feel for them. I'll look at full fuel payload, payload at tabs, different weights in front/rear seats and baggage to check the balance. While I look at take-off and landing distances they're usually so much shorter than the runways I rarely look at them much afterwards. The only exception is the start-stop distances for twins. Some airports have a second or third runway that is shorter, but could be better depending upon the wind. That's typically the only runway that might be too short for me. It would take a hot day, 2,000'+ altitude and max gross to get down ~3,700' start-stop for the Baron.

When I get a "heavy" or "odd" load, I'll run the W&B to make sure if it's good or not. From flying my family and various Angel Flight missions I have a good feel for the W&B of the plane I'm flying.
 
You are very experienced with 30 years of flying. I'm a beginner and have only done the takeoff calculations in online ground school. Out flight club requires W & B forms be filled out before each flight and carried with us on the flight, but in my total three flights so far, we haven't done takeoff/landing distances and other calculations.

I see a danger here for me in getting complacent and also not getting in the habit of doing those. It seems this early on it is not required, but your post made me realize I should be doing these anyway and checking to see if (judging best I can the distance needed for takeoff) see how realistic my calculations end up being.

I thought it was just the tiny, tiny, difficult to see lines in our textbooks, but made me laugh to realize that's how it is in real life too. I have the POH for the plane so from now on thanks to your post I'm gong to do those to get in the habit, and to get competent at it.

Thanks for the idea!
 
I use a W&B app on my iPhone and iPad for flights that have different conditions than my typical me and the Bride and x number of gallons. If runway length is an issue or density altitude, I'll look over the chart. I also included the performance charts in my checklist, if I need them.
 
1. Canopy closed - within weight.
2. Nose gear still on ground after engine start - within balance
 
Nope...most often it's just me and maybe a friend.

I ran the numbers last year for the Oshkosh trip. It didn't much make a difference for my 285HP turbo'd BO. At gross, cough cough, we climbed out at +1,200fpm all the way up to 16,500 feet. :D
 
denverpilot said:
The problem is, the curve may not have moved linearly.

And maybe more of a problem, jacking with the published numbers is sure to be a massive liability someday eventually in a courtroom when some pilot, even one warned that the software is not for legal planning purposes and makes assumptions based upon likely faulty data the pilot themselves added, and a stack of waiver forms they have to sign to even buy the stuff, and whatnot... Screws up and crashes and dies and their family decides to sue everything and everyone in sight.

No way in hell I would publish a damned thing the manufacturer didn't publish or software that would "tweak" their numbers back to reality.
Click to expand...

I think the premise was that the app would assist you by recording actual numbers for that airplane. I think such an app would have great application in the experimental world by recording the performance matched with actual weather. In a certified plane, my expectation would be that the performance would be worse than the published numbers, but who knows. If your airplane is performing at numbers 30% worse than the book numbers, that would be useful information.

The disclaimer that the software is not for planning when it's performing a planning function falls flat. In fact, pilots ARE using them for planning and "legal" would just mean that the FAA would say that you didn't run the numbers. It doesn't really protect the publisher very much. What would be useful is a disclaimer of accuracy, state that the app is after all just an app and it should not be deemed accurate or even consistent in it's errors. While the app can produce consistent output, it cannot receive consistently accurate inputs and is therefore error prone.
 
In a 172, no, unless I have a third body in the plane. It might be possible to get a 172 outside the gross weight or CG limits with two people, but it'd be tough. And the CG is more critical than a couple pounds over gross. . .

Regarding performance, with a high DA, shorter runway, I open the performance chart in the POH, extrapolate and add a bit.
 
I don't even own a POH for my airplane, so performance charts... nope..
 
I won't split hairs for a result. If I use a higher weight and temp in the tables than what actually exists and runway and obstacles can still be negotiated, then no big deal. I'll launch with those. If things are getting close, then yeah, I'll break out the calculator or E6b.

If you're having trouble reading the graphs, then go to Kinkos's or someplace and make a Xerox copy 20% or 30% larger than what you're seeing in the book.
 
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