Just wonder if this is expected behavior…
When moving the collective to say 60%, the power needle won’t follow all the way, and with a lag. It might stop at say 50%… If I then move the collective as little as possible to get 61%, the power needle follows to 61-62 ish…
Similar pattern the other direction but the power needle is always below the collector “requested” needle…
When close to the ground i find a nice descend at say 61% but when getting close to the ground the power starts to change either up or down…
Is it expected that the power should change like that without moving the collective further?
As I understood it, the collective controls the requested power and the power needle is the current power… but why is it such a lag and randomness when moving the current needle?
What exactly do you mean by the power needle? What heli are you flying?
The collective is just that – it adjusts the main rotor blades’ pitch collectively, i.e. simultaneously and synchronously. When the MR pitch is increased, the power demand is increased, too. This is anticipated by the rotor governor.
The purpose of the governor is to keep the main rotor RPM constant. It does that by adjusting the engine power output via throttle control. The power output is normally monitored using the torque indication.
The required torque depends on many factors including the main rotor pitch, but also the helicopter airspeed and height above the ground. When hovering near the ground (about 1/2 of the main rotor diameter or less), the helicopter experiences the ground effect: the rotor tip vortices are reduced which affects airflow patters around the blades reducing the rotor induced drag. This results in lower power requirement when hovering in ground effect as compared to hovering out of it.
Could it be that your question is specific to the Asobo Cabri G2? I have noticed the same, and asked myself the same question, but only in this helicopter.
Yes exactly this.
When moving the collective there are two needles, one for requested and one for current.
The current follow the requested input a bit randomly…
I don’t know if this is intended or a bug but it makes it hard to hover since the current might move without moving the collective. And it might also be delayed soo much that one need to move the collective too much just to get the current value to even start moving…
I’ve never encountered such an indication on a helicopter, but I wouldn’t pay attention to this as you describe. You should adjust the collective by the feel of whether it’s enough for the demand: level flight, climbing, hovering, etc. The exact number doesn’t matter unless it’s above the limit. I suggest that you forget about the ‘required collective’ needle at once. Can’t understand what help it might be of.
The power needle is a nice detail but irrelevant. The produced lift depends on blade angle (controlled by the collective) and rotor RPM (kept pretty much constant by the governor).
It also seems natural that the power output would lag slightly behind, because the blade pitch change via collective is pretty much instantaneous, so the engine has to “catch up” to provide the required power to maintain rotor RPM.
collective isn’t a constant it will need constant adjusting in all realms of flight especially as you enter and exit ETL and ground effect.
any movement of the cyclic will need collective adjustment as you are moving the rotor head so that will change the rotor pitch and you will need to adjust collective to compensate.
I’m trying to go by feeling but it feels a bit odd that the current collective angle changes by it self and or is lagging my input sporadically.
I.e. The heli starts to sink and I increase the collective but nothing happens. The current collective is not moving…
I increase some more and suddenly the current collective moves a lot…
It’s difficult to get a good feeling when the current collective does not follow my input…
Perhaps it’s meant to be like this it it just felt a bit odd.
Yes it does not follow the user input linearly. Sometimes it follows my input and sometimes it doesn’t move at all until I’m 5-20% higher than the current. Then it just moves a lot…
How do I get a feeling of that when the current collective angle doesn’t follow my user input?
I wonder if the needle behaviour is related to the simulation of the governor. I cannot say it is something I pay much attention to but if I recall correctly the throttle also moves quite quickly as well. When I flew a real R22 the throttle movements caused by the governor were much more subtle.
You call the two needles “requested” and “current collective”, but how do you know this is how they actually work? Honest question, is it mentioned in some documentation or the manual of the real thing?
I don’t think this is what the two needles mean. I think the small blue needle is what is the required Power for the current pitch angle (collective position) and current RPM is, I guess?
The big white needle, which is laggy and nonlinear, I think shows the current power output of the helictoper engine. It says “PWR” on top of the dial. Power is torque times angular velocity (RPM).
I might be completely wrong here because I don’t know much about helicopter physics, but I have never heard the terms “current” and “requested collective” and I don’t think that’s what the needles are supposed to represent.
I guess what I am trying to say is, as long as you RPM are kept stable by the governor, the change in pitch angle induced by moving the collective will have an immidiate effect. The engine’s power output required to maintain this is secondary, you shouldn’t worry about it at all as long as it is not in the red zone.
Concentrate on what you can control directly in the helictoper, which is the pitch angle of the rotor bladed via the collective. You do not control the throttle/power output directly, so don’t concentrate on the indicated values too much, they will not help you.
This is in contrast to fixed wing aircraft, where you directly control the throttle/power and the blade pitch is automatically adjusted for you to keep a certain RPM (in constant speed propellers).
In a helictoper, you control the blade pitch directly, and the throttle is automatically adjusted to keep a certain RPM.
I’m not at home so can’t take any screen shoots, but found this post which kind of touches my issue.
I’ve read in bit on the mli and it seems the blue needle which I called the requested should only be visible in start mode… However I see it all the time which seems incorrect.
The blue needle is the throttle position during startup.
Since it’s displayed all the time in the sim I guess it’s the governor increasing the throttle as I move the collective up.
The other needle which I called current seem to be a calculated percentage of available power. This is the one I thought was the collective current position but is perhaps more of a indication how much power is available from the engine.
I.e moving the collective up forces more power from the engine to not loose rpm, therefore this needle will move up towards 100% before the rpm starts to drop.
Similarly pressing the right rudder pedal will also require more power from the engine with the result that the pwr needle moving up…
I mistakenly believed this was the collective position but is just an indication of available power left from the engine…
You are absolutely correct. I also did some research and I couldn‘t find a single instance in video or documentation where the blue needle was displayed in the real life display during flight. As you said, it should only show up during startup to indicate the throttle position, as stated in the manual for the Cabri.