Plane Descends Too Fast

[scioly12345]

Hello,
My partner and I have gotten our planes to fly around 1:50 consistently, but we’ve noticed that the plane descends to the ground too fast. How can we decrease the descent rate? We tried moving CG back but it only helped a little bit (~5 sec ish).

[SaberwulfSC]

Try shimming the horizontal stabilizer up in the rear 1/32" and then retrim the plane. That should help and you may have to add more shims. I hope this helps.

[pumptato-cat]

Moving CG changes stability. If you want to control cruise/descent change incidence. Shimming the stab is one way(although I find it harder than the other method, and iirc changing the stab also changes the thrustline), but I prefer moving wingposts. Try increasing the wing angle until you see stalling during descent, and then decrease from that point very slightly until stall is gone.

EDIT: Now that I think about it, not sure if shimming is necessary. I'll wait on someone else to comment on that.
https://www.freeflight.org/wp-content/u ... -23-1.pdf
https://www.freeflight.org/wp-content/u ... rNFFS.pdf

Those links are very helpful, in case you haven't seen them.

[coachchuckaahs]

There are many things that affect the descent, including basic trim (see Cat's links) such as incidence of the wing and stab, CGC location, rubber selection, prop pitch, and winding.

It would help if you could give information about your trim setup measurements, your rubber selection (preferably in g/in), and your winding (max winds, max torque, unwinds, launch torque).

Coach Chuck

[bjt4888]

Hello,
My partner and I have gotten our planes to fly around 1:50 consistently, but we’ve noticed that the plane descends to the ground too fast. How can we decrease the descent rate? We tried moving CG back but it only helped a little bit (~5 sec ish).

Good job getting to 1:50. If you supply all or most of the below information we will be able to give very specific recommendations:

For the particular flight being analyzed, supply a google drive folder link containing the flight log which should include the following data

Airplane kit that you are using.

1. Rubber motor length (before use; not including knot)
2. Rubber motor weight
3. O-ring(s) weight
4. Total turns in motor
5. Maximum torque
6. Backoff turns
7. Launch torque
8. Remaining turns
9. Number of motor uses
10. Climb height
11. Flight time
12. Propeller type
13. Propeller pitch (indicate prop radius of measure)
14. Center of gravity (CG) - balance point of airplane with motor attached, measured as distance forward of, or back from, the wing trailing edge (TE)
15. Wing incidence measure
16. Stabilizer incidence measure (vertical tail boom offset)
17. Left wing washin measure
18. Tailboom offset measure (horizontal measure)
19. Stabilizer tilt measure

Other helpful info: Time from launch to highest point of flight.

If unsure of how to take these measurements, see the new for 2024 season National Free Flight Society (NFFS) website “Science Olympiad Basic Trimming” here: https://www.freeflight.org/wp-content/u ... 5-23-1.pdf

A google drive folder/file link with a video of the flight is also very helpful. Video should be taken from a vantage point to the side of the flight so that the entire flight can be viewed with minimal camera movement. Use the camera (phone) in landscape orientation. A video taken from the vantage point inside of the flight circle with the camera moving and following the airplane as it circles is difficult to analyze.

Brian T