If allowed to continue to climb, then a stall is likely and as the aircraft may still be relatively close to the ground, so recovery might not be possible.
| Cause | Fix | Comment |
| Insufficient downthrust. | Many models have several degrees of down thrust. Increase downthrust gradually until downthrust is optimum. | For additional information on downthrust see: "Model aircraft dives when throttled back from full RPM to idle". |
| Aircraft over powered. | Check engine/motor sizing and decrease as needed. | This could happen in a case where the the speed of the model exceeds the it's design limits creating excessive lift. |
| Aircraft over elevated. | Check wing/tailplane incidence,(decalage) and correct as needed. | |
| Aircraft over elevated 2. |
1. Check tailplane trim position and correct as needed. 2. If the aircraft is overpowered use flight modes to instantly change elevator trim as needed for different throttle settings. |
If the model pilot is not using Flight Modes and so is using one trim position for the elevator and has set that trim position for the best and shallowest angle of glide possible, (which equates to slowest air speed), then the aircraft will be very sensitive to throttle changes with a full throttle setting causing rapid climbing. The normal counter to this is to add more downthrust while keeping the elevator trim at zero/zero. The downside to this is that the aircraft will zoom i.e. climb rapidly when throttle is cut to zero. This behaviour is especially noticeable if the aircraft is overpowered. |
| Rearward CG. | Adjust the CG position as needed. |
As the center of gravity of an aircraft moves rearward, the aircraft becomes "hot" and if moved sufficiently rearward, the aircraft will become unstable about the pitch axis, see the Neutral Point article. Neutral Point Visualisation Provided the rearward position of the CG is not too excessive, then this can also lead to a rapid climb on takeoff. It occurs because wing moment is greater than the designer planned, thus pitching the nose up. This will almost never occur on an ARTF, as these matters are usually ironed out by the manufacturer. It can easily occur on a traditional build however if care is not taken in the selection of materials etc. This possibility should not occur if the builder ensures the CG is where the designer has indicated. For those who need to check if the position of the CG is optimal, then checks on Static Margin can be carried by using RC Aerobase's on line software. Neutral Point and Static Margin software
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Comments
12th. May 2016
Rearward CG point added. Contributed by Adrian Smith.
31st. May 2017
Added the text:
If the model pilot is not using Flight Modes and so is using one trim position for the elevator and has set that trim position for the best and shallowest angle of glide possible, (which equates to slowest air speed), then the aircraft will be very sensitive to throttle changes with a full throttle setting causing rapid climbing.
The normal counter to this is to add more downthrust while keeping the elevator trim at zero/zero. The downside to this is that the aircraft will zoom i.e. climb rapidly when throttle is cut to zero. This behaviour is especially noticeable if the aircraft is overpowered.
Point contributed in discussion with John Heley.