Sportstar -takeoff and landing distances hi density altitude

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jandras
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Sportstar -takeoff and landing distances hi density altitude

Post by jandras »

As best as I can tell, the POH for the Evektor Sportstar only gives takeoff and landing distances for a sea level field ("0 ft ISA"). See sections 5.2.3 and 5.2.4 of the following POH:

http://www.aerodynamicaviation.com/docu ... %20POH.pdf

I'm a student and I'm planning a flight from a low level airport (John Wayne SNA) to a mountain airport (Big Bear L35) and need to determine the takeoff run and landing distances for a density altitude of 8,000 ft.

How do I find or calculate distances for a DA of 8,000? I see percentage adjustments for tail wind and runway inclination, but nothing for altitude.

Thanks!
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drseti
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Re: Sportstar -takeoff and landing distances hi density alti

Post by drseti »

See my charts on these pages:

TO distances http://avsport.org/acft/SportStar_takeoff_distances.htm

Landing distances http://avsport.org/acft/SportStar_landing_distances.htm

Note that these are the kind of charts that are required to be in the POH for a certified aircraft. Unfortunately, for an LSA, the AOI requirements are somewhat less rigorous.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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CharlieTango
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Re: Sportstar -takeoff and landing distances hi density alti

Post by CharlieTango »

jandras,

I live in and fly a light sport out of Mammoth Lakes, a bit higher than Big Bear. Flight Design does not provide landing and take off distance charts but since my CT can operate in less than 1,000' the calculation isn't important to me unless the field is extremely short.

From Paul's chart you can see that the distances do not double from 0 to 8,000DA, you can use that as a rough starting point.

Personally I use the 5 second rule. I know that my CT should be flying in roughly 5 seconds and if isn't I begin to question why not and think about aborting the takeoff.

You won't find the runway at Big Bear short for your light sport so this is mostly a mental exercise.
jandras
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Re: Sportstar -takeoff and landing distances hi density alti

Post by jandras »

Paul, CharlieTango - thanks for your replies. Really helpful.

Paul, did you fly all those altitudes to create the charts?
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Re: Sportstar -takeoff and landing distances hi density alti

Post by Jim Stewart »

I was given this problem in advance for my pp oral. My CTSW doesn't have performance charts either. I used a Koch chart to calculate the numbers.
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drseti
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Re: Sportstar -takeoff and landing distances hi density alti

Post by drseti »

jandras wrote:Paul, did you fly all those altitudes to create the charts?
No, I got that data from the factory folks at Kunovice. They had done the tests, put all their data in a spreadsheet, and Excel made the bar graphs.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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Re: Sportstar -takeoff and landing distances hi density alti

Post by FastEddieB »

Thanks for the chart, Jim.

I recall it now, but had forgotten it.

My Sky Arrow POH also lacks much data for higher DA's.

I'll probably print it out and stick it in my POH.

That said, with the extremely short takoff and landing distances of most of our LSA's, I can't recall ever needing precise info for the typical runways I use.
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CharlieTango
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Re: Sportstar -takeoff and landing distances hi density alti

Post by CharlieTango »

When I compare the Koch chart to Paul's I see vastly different results. Is it just me? Use 6,000'.

Paul's chart shows a 1/3 increase in TO. Koch shows 2 1/2 times increase. Why are these not in the same ballpark?
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drseti
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Re: Sportstar -takeoff and landing distances hi density alti

Post by drseti »

At 6000 ft density altitude (or, 6000 ft field elevation at 29.92 in Hg at +15 Celsius), on the Koch chart I get a distance factor of 2.2, relative to an ISA standard day at sea level. On the chart made from the Evektor spreadsheet, the same conditions yield (990/690) = 1.43. Over a 50 foot obstacle, the ratio is (2280/1590) which still equals 1.43. There is indeed a significant discrepancy, which I am at a loss to explain. All I can say for sure is the Evektor data was derived from flight tests, and the Koch chart from theory. Which do you suppose is wrong?
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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CharlieTango
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Re: Sportstar -takeoff and landing distances hi density alti

Post by CharlieTango »

Maybe I shouldn't be using the Koch chart right of my screen :)
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drseti
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Re: Sportstar -takeoff and landing distances hi density alti

Post by drseti »

I just found one apparent error on the Koch chart that I never noticed before. Try drawing a straight line from sea level through a distance factor of 1.0, and extrapolate that line to the airport temperature scale. The line intersects temperature at +17 Celsius. We were taught that standard temperature is +15 Celsius. This is not enough of a discrepancy to explain the difference between the Koch chart and Evektor's data, but it makes one wonder. Am I mistaken in thinking that +15 C is standard temperature?
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
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drseti
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Re: Sportstar -takeoff and landing distances hi density alti

Post by drseti »

FWIW, the takeoff distance factor (ratio) from the Evektor data appears to be the same for any chosen density altitude, between grass and pavement, for either ground run or distance over a 50 foot obstacle. In other words, the data are internally consistent. (Whether they are accurate or not is another question altogether!) :wink:
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
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ct4me
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Re: Sportstar -takeoff and landing distances hi density alti

Post by ct4me »

On take-off at the higher altitude just be prepared for a much longer take-off roll, and very anemic climb after lift-off. It will screw with your mind, as you're used to much better performance at the lower altitude. The first time I took off from Flagstaff (7,000ft, with a DA of 9,300) I really started to think something was wrong. I'm scanning the instruments and checking settings like crazy. I even began to think I'd left a coat hanging on a wing or stabilizer. Be careful of adding fuel or a passenger while at the higher altitude. Here's a video of that take-off: http://www.youtube.com/watch?v=p4CdNP9RNTk... note the DA warning through the window at the start. I think there was a very weak tailwind, too. But things like that get amplified at higher DA.
Tim
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3Dreaming
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Re: Sportstar -takeoff and landing distances hi density alti

Post by 3Dreaming »

15c is standard at sea level. At 6000 feet wouldn't it be 3c?
VL Roberts
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Re: Sportstar -takeoff and landing distances hi density alti

Post by VL Roberts »

15 C at 6000 would be a warm day. I believe the Koch chart is correct when I compare to the numbers in the C162 POH , which uses the standard Cessna performance charts. According to the C162 POH, distance to clear a 50 ft obstacle on takeoff with 8000 pressure alt and 40 C is 2810 ft. High DA obviously not as critical for an LSA as it is for heavier aircraft.
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