Sport Pilot Talk

Hello everyone,

My Sportstar manual has very little about takeoff performance. It basically just lists a ~600 ft takeoff roll is needed at gross weight and standard conditions if I remember correctly. I am interested in how it is affected by different density altitudes, weights, winds, slopes etc. You know that stuff us pilots are supposed to compensate for. It is hard to factor these things into decision-making without the data.

I have so far operated at fields that are not in anyway pushing the limits. The shortest is about 2500 ft and low elevation. Maybe someday I'll want to do a 2000 ft runway at a much higher elevation and a hot day. How would I know if I am taking a big risk?

Do other LSA manufacturers publish more performance information? Is there a way to approximately estimate the effects of density altitude and aircraft weight with very limited aircraft data?

What do you all do?


-Dave

Good question!

Here are two real-world examples that I experienced with my SportCruiser:

1) Cold Winter day, +/- 1,300’ MSL: The plane would almost be in the air by the time my throttle hit the full power stop.
2) Hot, humid, Summer day in Florida, 0’ MSL: Go to full throttle, wait about 4 to 6 seconds watching the airspeed climb to rotation airspeed.

Density altitude is real. Weight, headwind and runway slope are other contributing factors to ground roll.

Besides runway length, another consideration is rate of climb that might be required to clear terrain.

Good short-field takeoff skills can help.

Some aircraft manuals provide detailed performance charts for ground roll, taking into account density altitude, and weight. In the absence of such performance charts, knowing your aircraft is critical. Using a long runway you can take note to observe and estimate your ground roll keeping in mind the conditions of temperature, density altitude and weight. Expand your limits gradually.

Practicing short field techniques on shorter runways with a good instructor that is familiar with your plane can help immensely to build skills and understand your limits. Expand your skills with a trusted instructor. Fly well under your limits when solo. Learning never stops.

Perhaps others can chime in here with some rules of thumb and further suggestions?

Dave C wrote: ↑Wed Nov 08, 2023 6:39 pm I have so far operated at fields that are not in anyway pushing the limits. The shortest is about 2500 ft and low elevation. Maybe someday I'll want to do a 2000 ft runway at a much higher elevation and a hot day. How would I know if I am taking a big risk?

Short answer:

Look for an airport in the area with a long runway. Start there and note your takeoff roll, along with all contributing factors.

Not much in my owners manual … just one note …

It's true that ASTM requirements for takeoff and landing distance data in the AOI are limited to a single example for sea level performance in standard atmosphere conditions. But many manufactures go beyond ASTM requirements (if not in the manual, then at least for internal use to document their flight test experience). Here are a couple of examples for a SportStar, showing both ground roll and distance to clear a 50 foot obstacle for both grass and pavement, at various density altitudes (which correlate to MSL altitudes on standard days):

https://avsport.org/acft/SportStar_take ... tances.htm
https://avsport.org/acft/SportStar_land ... tances.htm

I have found that, for both SportStars I have owned, these numbers correlate rather well with my own experiences.

Thanks for everyone's input. This has been something that I have been thinking about for awhile but doesn't matter much for my typical operations. I do remember in ground school looking at the elaborate charts available from Cessna for their planes.

Paul, I figured you have dealt with this question before. Those charts are just what I need. They account for DA which is the biggest variable in my mind. I am going to assume you got those from Evektor somehow. They really should be in the manual.

-Dave

Your assumption is correct, Dave. They can't be in the manual, because they do not comply with ASTM standards. But you can be pretty sure that most (if not all) LSA manufactures collect similar data for internal use.