Landing patterns and reverse thrust!

I don't know how long of a distance it takes for most of you to land, but when diving in below the treeline from 200 feet I pick up tremendousspeed on my EasyStar to the point of hitting 50 mph and overshootingthe runway, ending up in the trees.

Of course I can land in 500 feet easy, but making my autopilot do it wasnot. I was curious if anyone wanted to chime in on how they solvedtheir landing issues and minimizing the length of space required.

I was able to get mine down to 500 feet diving in from 200 feet and leveling off. The attached photo is my landing pattern.

1) Circle the landing zone, sample the winds
2) Go downwind
3) Turn for final approach
4) DIVE! with a feedback loop on airspeed able to do reverse thrust
5) flare and land.

My reverse thrust is done with a car speed controller. I can get +1 lbthrust as well as -1 lb of thrust. (Wasn't expecting that either.) Thisis just by running a typical 5x5 prop backwards!

The end result is that I slow down from 50 mph to 20 mph in a few seconds after the dive.

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  • There are a couple of strategies in real aviation for steep approaches. One of them is a short field landing and the other is the forward slip.

    Generally a short field landing will allow you to maintain a higher than normal glide slope to a runway. The short field landing generally has the characteristics of a slightly slower than normal approach speed. In a Cessna 172, the short field approach is easy to "detect" because the plane actually goes to a nose up attitude when at the proper airspeed. I suspect the same can be achieved with your easy star as it is similar in design to the Cessna. You will need a real airspeed sensor and you will also need to know with some certainty what the stall speed of the aircraft is.

    The forward slip is achieved by applying right rudder and opposite roll such that the plane remains level. This is technique is frequently used on planes such as the Katana where the glide ratio is very high.

    Landing is really it's own mode, you need to enter final in the right configuration, or you will miss the runway.

    You might also consider having less altitude, or be in a stabilized decent when turning to final. In a normal plane you are usually already descending when turning from base to final. Additionally you might also consider extending your final.
  • It seems to me that if the airframe can do the job when being controlled by a human and not when controlled by the computer, then the problem is with the algorithm.

    You state that you have more success in low wind situations. Assuming that stability is not the issue, then I wonder if you are allowing for the "gradient effect". That is the reduction in airspeed as you get closer to the ground. I suspect that when you are flying it yourself, you are making automatic corrections for this. The autopilot is following some other rule.

    And always remember - "There are three rules for a perfect landing every time . . . unfortunately, noone knows what they are."
  • You should be able to trim the airplane's pitch attitude to maintain your Vref speed (approach and touchdown speed) in level flight. I would fly at a safe altitude and slowly reduce the power while trimming the elevator to maintain level flight. Once you find a comfortable approach speed (about 1.3X stall speed), just reduce the power to start a decent. The airplane is trimmed and should maintain that approach speed even if you bring the power to idle. Now you can just use power settings to control your descent rate.

    This is how real airplanes are flown, so I assume it should work fine with the easystar as well.
  • I keep forgetting yours isnt a normal one :D
    Once mine can be trusted, I'll start doing landings and give you all the data.
  • I'm probably going to show how much of an amateur I am (if I could even be ranked as highly as that), but I figured I'd give my two cents, however devalued they may become.

    What about some sort of arresting gear?
  • Can anyone give me some landing stats for their plane? Mine: From 200 feet up going 30 mph it takes me 600 feet to land.
  • @bGatti - I'm sure the prop is somewhat unhappy and stalling and/or otherwise being inefficient. Heck, it's running the airfoil backwards! But it does produce drag very well, and plenty of it.
  • I imagine your dynamic negative thrust is about half of your static negative dynamic thrust; if the plane is moving forward, and the props are churning backwards, surely they must be stalled?
  • Yep- using the breaking functionalty. Mostly because I am forced to with this ESC.
  • @Ritchie - I have specific landing bearings that effectively define runways. Right now there's a waypoint for the landing spot, and a list of up to 4 approach bearings. It picks the closest one. Now for landing patterns, I have 2 modes. One is beam follow, the other is radius follow. I radius follow around the landing point, then set up a new radius waypoint which is at the end of the runway, offset perpendicular by the radius length. So after I'm done orbiting and measuring winds, I fly to the other radius which lines me up with the runway. I added one last tweak which returns to beam following along the runway when I'm pointing perpendicular. That helps in cases when the wind is blowing and the last turn following the radius doesn't quite line you up.

    Anyway, reverse thrust is pretty easy- just get a model car speed controller and allow your throttle values to go negative from a speed PID loop.
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