Helicopter ground effect transition is abrupt and requires large inputs to recover

With the new SU11 helicopter flight model, operations on elevated platforms
suffer from what appears to be a lack of a transition in handling ground
effect. This effect seems to be worse for heavier helicopters. When
approaching a platform horizontally, the helicopter will get a huge kick of
energy exactly when the RADIO HEIGHT value rapidly decreases, as the center of
the model crosses over the threshold of the elevated platform. This “kick”
seems much worse for a heavier helicopter, and in ours it is also from the
left (as opposed to simply rapidly rising upward). Users don’t like this
behavior, our pilots are saying this isn’t correct and the physics of the
rotor disc will have the behavior spread out over time. It’s not that the
effect is wrong, but the transition case is abrupt which results in behaviors
that aren’t realistic. We’re wondering if there may be some way to stop this
from happening? We have dialed in our flight model now and have it working
well but we can’t find a solution to this ground effect behavior.

Hello @davux3 Can you make a video demonstrating the problem with CFD particle
visualisation enabled please? Regards, Sylvain

Hi Sylvain - thanks for the quick reply. I have included a video with the CFD
visualization turned on. Note that the helicopter is in hands-off AFCS modes
since it’s too difficult to fly precisely otherwise, so the kick here isn’t
representative of how jarring it is for somebody actually flying (as I said
the ground effect overall increasing is expected and isn’t the direct
problem). The video is at a third party scenery but you can get the same
effect on the built-in US Bank tower. Video:
https://drive.google.com/file/d/1iImlcdYk47TwTQXDvlCB6iO3rRrovWui/view?usp=share_link

I agree totally on this. Too aprupt and not what is happening on any real life
approach videos either, not even when coming in “hard and flat”. The “kick” is
somehow exaggerated for “anything” that is higher than plain ground (roofs,
helipads )

Hello @davux3 @ChokDK The developers acknowledged this issue. It’s tracked and
will be addressed in a future update. Regards, Sylvain

There is also a very abrupt change in behaviour for fixed wing craft when
transitioning between land and water - even at high altitudes the turbulence
increases dramatically and suddenly when flying between water and land.

What I have experienced is a bopping effect where you are in a hover and the
helicopter bops up and down slowly. In DCS I can hold the Huey in a hover at a
specific height lets say 5 or 8 feet, only adjusting the collective maybe once
whereas in MSFS I try to use a limited amount of collective but with the
bopping up and down I find myself having to increase and decrease collective
all the time, sometimes requiring large inputs which results in overshooting
the desired power setting. To put it in common words its like the chopper goes
in and out of ground effect constantly to which I have to “catch” it from
falling or from jumping into the air further aggrevated by collective
overshoots.

Bumping this. This issue has existed since SU11 and was reported and confirmed quickly. We’re hoping that this can still be resolved in the lifetime of MFS20.

This issue continues to result in substantial dissatisfaction for our customers and impacts all of the helicopters using the native flight model. This issue also impacts all upcoming helicopters and future helicopters, meaning that it is beginning to represent a risk for platform viability.

Same issue here. Why hasn’t this been addressed yet?

Since this is a user-facing issue, it was posted to the forums: Helicopter ground effect transition is abrupt and requires large inputs to recover - Aircraft & Systems - Microsoft Flight Simulator Forums

The thread was subsequently was locked so end users are disallowed from actively voting for this issue to be fixed. I find this disturbing.

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Just wanted to confirm the issue, and what’s worse, not only rooftop or oil rig helipads with significant altitude difference are affected.

The problem is very noticeable even with helicopter dollies less then 50 cm high.

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For the record, a few other transition scenarios which seem to be unrealistic.

When leaving or entering an elevated helipad in level flight, especially when the course is not perpendicular to the edge of the helipad, a sudden yaw rotation is induced without any pilot input, that can turn the helicopter almost 180 degrees. See the videos linked below, note that there was NO PILOT INPUT on the anti torque pedals that would introduce that yaw nor any collective input. No input obviously means no additional input, other than some pedal needed to maintain the heading while approaching the edge in a straight line

The strength of this effect seem to depend on the rotation direction of the rotor and on which side the helicopter leaves the pad. CCW rotors like the Bell 407 will cause issues when leaving to the left, CW when leaving to the right, see the Cabri videos below.

Bell 407 leaving the pad to the left, abrupt, violent yaw: groundeffect.mp4 - Google Drive

Cabri, leaving the pad to the left, notice the effect is very minor: CabriLeft.mkv - Google Drive

Cabri, leaving the pad to the right, abrupt, violent yaw: CabriRight.mkv - Google Drive

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Users on SU15 beta are reporting a big improvement to helicopter ground effect. :slight_smile:

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