Sportstar -takeoff and landing distances hi density altitude

[drseti]

15c is standard at sea level. At 6000 feet wouldn't it be 3c?

Aha! Tom, I think you've resolved the apparent discrepancy.

[dstclair]

OK, so now you've determined a given runway is supposed to be long enough for your aircraft. How do you know that your particular plane with you as the pilot are actually going to successfully accomplish the task? A good rule of thumb is that you must achieve 70% of the take-off speed by the 50% point of the runway.

Probably never have a problem on paved runways at high-altitudes for our LSA's but I used to fly into AXX in a Cherokee 180. Elevation around 8400'. That 8900' runway sure looks long but on a normal summer morning I'd use up over half to lift off. I believe the book value at sea level was 1600' to clear a 50' obstacle. I always exceeded 70% of the speed by halfway but sure was nervous the first few take-offs. Took a looooooooong time to get to rotation speed. Learned the value of patience I also stayed in ground effect for most of the remaining runway to gather airspeed before doing any significant climb.

As others will attest, mountain strips are often one-way. AXX is no different. The terrain to the south rises faster than most non-turbos can climb and has, unfortunately, claimed a lot of lives even though there (at least, used to be) are large warning posters in the FBO and signs on the runway about the danger.

[Jack Tyler]

Excellent discussion topic. Glad we're taking it beyond the Sportstar.

For at least some pilots & owners of LSA's, T/O and landing performance at higher elevations is more (not less) important than for heavier Part 23 a/c. The reason is that the LSA's lower weight (and so inertia) and lower approach speeds makes them more suitable for using smaller airstrips. Swap out the wheel pants for some larger tires, and LSA's can become the preferred choice for accessing many beautiful backcountry airstrips that are all over our country. This was very apparent when talking with some of the Aerotrek, Rans and Just LSA owners at Sun 'n Fun last month. They were choosing these kinds of LSAs for just this kind of use.

We've tried to examine the issue of using non-paved airstrips, along with all the other factors that determine T/O and Landing performance, because our Grumman Tiger wasn't specifically designed for shorter, unimproved runway use and we're often near MTOW. At such strips, landing safely can be easier for the a/c to accomplish than taking off and clearing upwind obstacles. So here's a thumb rule backcountry pilots use to verify a T/O attempt will be safe when they face a multitude of variables (elevation, rough or wet surface area, humidity, temp) and they can't determine a guaranteed T/O distance:

To Verify Runway Length OK and T/O Safe:
1. Walk the runway (something we should do on unimproved strips anyway) while measuring it.
2. Knowing runway length, mark ‘Runway Mid-Point’ on the walk back so it’s visible on T/O (rock formation, stick with rag on top, etc.)
2. Determine your T/O Speed for DA & Weight. Multiply by 70%. (If computed T/O speed is 45 kts, 'decision speed' is 31.5 kts)
3. Determine T/O Distance needed 50’ Clearance @ DA, Weight & Temp. Does runway SEEM long enough for a safe T/O?
5. Assuming it does, on the T/O roll monitor speed & plan a Hard Abort if not @ 70% T/O Speed at Mid-Point of runway

If terrain obstacles are also part of the equation, estimate terrain clearance needed and at what distance. Estimate your likely rate of climb for the DA in feet per min. Then use a Climb Gradient Chart to determine how far 'up' you will climb for how far 'out you will fly before arriving at the obstacle(s). http://www.aopa.org/asf/hotspot/Rate-of ... 0Table.pdf

[drseti]

Good tips, Jack. My old Beechcraft was far from being a bush plane, but I took it routinely into (and back out of!) a private mountain strip in West Virginia. It was heavily modified for this purpose, with a 3 bladed prop (decreased takeoff distance), vortex generators on all three control surfaces (improved slow-flight stability), droop wing tips (decreased stall speed), and Cleveland brakes (much better stopping power than the original Goodyears). And you can bet I walked the runway every trip, because it was never exactly the same twice.

A low pass before landing to chase the deer away was SOP. And (maybe a bit of thread overlap here), I did have to abort the takeoff once because of deer approaching the runway.

BTW, flying the AeroTrek A 220 reminded me that tailwheel aircraft seem to do better in short-field operations than do their otherwise identical tricycle brethren.

[jandras]

Question re Koch Charts -

Is it one size fits all, i.e. close enough for all aircraft, or is each chart adjusted to give answers that are appropriate to a particular aircraft?

I ask because I compared the answers from a couple of Koch Charts on Google, and unless I'm doing something wrong, they give very different answers when reading the line between the same PA and TEMP points.

I get the sense that using a random Koch Chart is like looking at a Beechcraft POH to estimate the altitude performance of my SportStar, i.e. useful to get the gist of the problem, but very inaccurate.

Anybody know for sure?

[jandras]

Never mind. Connecting 100 deg. F and 6,000 ft, one chart says "add this percentage to you normal take-off distance" (240%)' and the other chart says "take-off distance factor from sea level" (3.4).

Same thing stated differently. Doh.

[newamiga]

I guess I would throw out there that living in Colorado and dealing with high DA for a fair part of the year, LSA's do really well at altitude for the most part. I say this based on experience learning at a school in Denver and then buying my Gobosh and flying it out of my home airport at Meadow Lake (KFLY - the coolest ID out there in my opinion) at 6800 feet field altitude. I was doing touch and goes this past weekend with a DA of 8500 feet and getting great performance. I have done touch and goes at 10K DA at FLY in the summer. Lastly we fly up to Leadville when the winds aloft are less than 12 kts. Leadville is the highest paved airport in the U.S. The DA there can easily get above 11K ft and still LSA's can easily operate out of there. The takeoff roll is a little longer but it isn't as harrowing as I have seen some other "traditional" GA planes taking off out of there.

I say LSA's because I have also experienced flying the Remos north of Denver and it did fine. The only plane we saw some level of takeoff performance issues with was the PiperSport. I am not trying to disparage that plane but based on empirical experience in the flying club I am in, it has had performance issues on takeoff. It is no longer in our club.

Carl