Generator Failure

[DST]

Would somebody please be so kind and explain to me what causes that annoying "generator failure" that occurs from time to time whilst flying within completely normal parameters. I got this annoying "failure" only in the Hind, never in Huey, Mi8 or Apache. Is there something to watch out for, like the buffeting before vortex ring state, I don´t get it, it seems to come out of nowhere. Collective never beyond 90 degrees when nit happens, what are parameters that causes this, I find nothing in videos or manuals.

[randomTOTEN]

I hate to be the bearer of bad news, but if you're experiencing this "generator failure" you are most certainly not flying "within completely normal parameters."

Your rotor RPM is life. You must maintain control of it at all times.

[admiki]

11 hours ago, DST said:

Would somebody please be so kind and explain to me what causes that annoying "generator failure" that occurs from time to time whilst flying within completely normal parameters. I got this annoying "failure" only in the Hind, never in Huey, Mi8 or Apache. Is there something to watch out for, like the buffeting before vortex ring state, I don´t get it, it seems to come out of nowhere. Collective never beyond 90 degrees when nit happens, what are parameters that causes this, I find nothing in videos or manuals.

OK, I'll take you on your word that you are flying completely normal and not pulling full collective.

It would be the best if you can give us track file of such flight, but my wild guess is that anti-ice system is on.

Edited June 27, 2023 by admiki

[Hiob]

14 hours ago, DST said:

Would somebody please be so kind and explain to me what causes that annoying "generator failure" that occurs from time to time whilst flying within completely normal parameters. I got this annoying "failure" only in the Hind, never in Huey, Mi8 or Apache. Is there something to watch out for, like the buffeting before vortex ring state, I don´t get it, it seems to come out of nowhere. Collective never beyond 90 degrees when nit happens, what are parameters that causes this, I find nothing in videos or manuals.

What do you mean by "Collective 90 degrees"? What is your rotor pitch?

[DST]

29 minutes ago, Hiob said:

What do you mean by "Collective 90 degrees"? What is your rotor pitch?

Yes I think it´s rotor pitch, the indicator on the left side of cockpit shown in degrees that rises and falls with collective movement? I don´t make any rapid movements with collective, don´t exaggarate, just turning quite slowly around in ca. 100 feet height, like I said the "generator failure" seems to appear out of nowhere.

But I found that pulling throttle levers up to maximum seems to help with this issue. Never cared much about throttle as I always start in parking slot with engines running, I always assumed, the throttle is already in normal position for flying. Remember having read that max position of throttle is only for "emergencies".

[admiki]

Throttles are not your solution.

Are you also sure that you don't have any ghost bindings for correlator (Russian speak for twist grip)?

[DST]

What does the correlator do? Yes indeed, when I raise collective, the grip makes turns, do I have to make extra binding for that?

[corn322]

10 minutes ago, DST said:

Yes indeed, when I raise collective, the grip makes turns

This may be the cause of your problems. Check bindings for "Throttle (Collective)".

[admiki]

53 minutes ago, DST said:

What does the correlator do? Yes indeed, when I raise collective, the grip makes turns, do I have to make extra binding for that?

Grip stays in flight position. You don't touch it unless it is emergency, which AFAIK is not modelled in DCS.

Show us you bindings

Edited June 27, 2023 by admiki

[AeriaGloria]

Anytime your rotor drools below 95% rpm is a bad thing. Less than 90% is borderline emergency and makes you very inefficient. 

In my experience, you can pull 13-14 degrees collective without rotor droop. But it will drop very fast beyond that, especially as rotor rom drops so does tail rotor, means you need more right pedal which drains power even faster. 

On top of right pedal draining power, so does right cyclic which causes a transient torque spike. 

So if using right pedal or right cyclic, it may be much less then 13-14 degrees to cause rotor droop below 95% 

As Miki said ETL throttles won’t do anything. Default/middle is auto and will give you max power. Collective grip twisted all the way.. 

If you were in combat, it takes very little bullets to take out an engines power also……

[DST]

2 hours ago, AeriaGloria said:

Anytime your rotor drools below 95% rpm is a bad thing. Less than 90% is borderline emergency and makes you very inefficient. 

In my experience, you can pull 13-14 degrees collective without rotor droop. But it will drop very fast beyond that, especially as rotor rom drops so does tail rotor, means you need more right pedal which drains power even faster. 

On top of right pedal draining power, so does right cyclic which causes a transient torque spike. 

So if using right pedal or right cyclic, it may be much less then 13-14 degrees to cause rotor droop below 95% 

As Miki said ETL throttles won’t do anything. Default/middle is auto and will give you max power. Collective grip twisted all the way.. 

If you were in combat, it takes very little bullets to take out an engines power also……

Not 100% sure but I think it happend mostly whilst doing right turn with strong right pedal input. So do I have to be careful with right turns in the Hind?

5 hours ago, corn322 said:

This may be the cause of your problems. Check bindings for "Throttle (Collective)".

I don´t have a binding for that. My axis commands in use for the Hind are cyclic, collective and pedals.

[AeriaGloria]

8 hours ago, DST said:

Not 100% sure but I think it happend mostly whilst doing right turn with strong right pedal input. So do I have to be careful with right turns in the Hind?

I don´t have a binding for that. My axis commands in use for the Hind are cyclic, collective and pedals.

Yes often for right turns at max speed you will realize that you will have to reduce collective if you use enough right pedal and right cyclic. You can experiment and see how much, active pause is good for that. 

In the manual, I think it states that for a left vs right turn, the average top sustained speed of said turn will vary by 20-30 kmh depending on direction. 
 

For example you might be able to hold a 45 degree bank left turn at 280 kmh, but only 250 kmh if your are in a 45 degree bank turning right. 

[II.JG1_Vonrd]

Per Chuck's Guide:

If you happen to run into a GENERATOR FAILURE of your own doing, how do you fix this ?

• In case of a Main Rotor underspeed (rotor droop), lower collective to unload the rotor . The RPM will then increase again . Generators will re -engage automatically again by themselves .

• When generators are re -engaged after an electrical power loss , the MAIN 115 VAC XMFR OFF and MAIN 36 VAC XMFR OFF lights will still remain illuminated . You will need to manually set both Transformer switches to OFF, then back to MAIN . The MAIN 115 VAC XMFR OFF and MAIN 36 VAC XMFR OFF lights should then extinguish . Also , the autopilot channels will need to be restarted manually .

• In general , fly smoothly and avoid sudden RPM drops/rotor drooping in the first place .

• Monitor power usage carefully on the relevant gauges (i . e . EPR Gauge, NR Gauge, N 1 Gauge, and PTIT Gauge) whenever flying at high altitudes in the mountains or with heavy cargo, when rotor overload and RPM drop is more likely to happen .

I'm not sure if this works with a failure due to battle damage. I would think that shutting down the damaged Gen and resetting the Transformers and autopilot might keep you flying for an Emerg landing or (hopefully) RTB. I haven't had the wits about me to try it while I'm being shot to burger.

[Jascha]

I had the same issue when playing Mi-24P YoYo's campaign. When entering mountain area, at higher altitude, I noticed that air temperature is close to 0C. I have enabled the clock heater, pitot heater (left and right) and also left and right engine anti-ice heater. Anti-Ice system mode was set to auto (if I understand correctly this switch controls only the anti-ice system for the rotor blades). After 10 minutes or so, I noticed the icing warning light - it was on despite everything being set as described above. It went off after some time. Later, when descending, despite the temperature rising, the warning become visible again. Before trying to perform a vertical landing, I enabled the PZU. Shorty after right engine RPM dropped a bit and soon the "Generator Failure" message could be heard. I have lost all AP settings, rotor RPM dropped to 80% iirc and I almost crashed. Somehow I managed to transition into the forward flight and everything went back to stable.

My questions are:

- How we should actually use anti-icing system in this situation? Is this system modeled properly at current state of the module?

- How exactly does the anti-icing affects the Mi-24P performance? Can it be used together with the PZU?

- Should the battery heater be on in this situation? Does it have some impact on Generator Failure?

- How to fix this situation when close to the ground? Lowering the collective is not really an option.

On 6/27/2023 at 10:07 PM, AeriaGloria said:

On top of right pedal draining power, so does right cyclic which causes a transient torque spike. 

Could you please explain this in more detail?

[admiki]

16 minutes ago, Jascha said:

I had the same issue when playing Mi-24P YoYo's campaign. When entering mountain area, at higher altitude, I noticed that air temperature is close to 0C. I have enabled the clock heater, pitot heater (left and right) and also left and right engine anti-ice heater. Anti-Ice system mode was set to auto (if I understand correctly this switch controls only the anti-ice system for the rotor blades). After 10 minutes or so, I noticed the icing warning light - it was on despite everything being set as described above. It went off after some time. Later, when descending, despite the temperature rising, the warning become visible again. Before trying to perform a vertical landing, I enabled the PZU. Shorty after right engine RPM dropped a bit and soon the "Generator Failure" message could be heard. I have lost all AP settings, rotor RPM dropped to 80% iirc and I almost crashed. Somehow I managed to transition into the forward flight and everything went back to stable.

My questions are:

- How we should actually use anti-icing system in this situation? Is this system modeled properly at current state of the module?

- How exactly does the anti-icing affects the Mi-24P performance? Can it be used together with the PZU?

- Should the battery heater be on in this situation? Does it have some impact on Generator Failure?

- How to fix this situation when close to the ground? Lowering the collective is not really an option.

Could you please explain this in more detail?

To keep it short, both anti ice and PZU will rob you of engine power. 

Reason why ice warning was on and off is that on AUTO system would turn on when there is ice and turn off when ice is gone. And it would repeat that as needed. What I like to do is to set it on manual and keep it on whenever there is a possibility of icing. IRL, it's better to prevent ice forming then risk melting ice chunks getting sucked into engine. When you know you will need some extra power (high, heavy, landing) you switch anti-ice off just before you need that power. You're good to fly for some time before ice accumulates enough to become a problem.

As for torque spike, this gives nice explanation 

 

 

[Jascha]

8 minutes ago, admiki said:

To keep it short, both anti ice and PZU will rob you of engine power.

So the reason for Generator Failure in my case was most likely the use of engine anti-ice heaters together and PZU? Are the negative effects of NOT using anti-ice or PZU when supposed to, simulated right now in this module?

As for anti-ice mode MANUAL/AUTO - this is separate from the engine heaters, right?

Thanks for the video link.

[zerO_crash]

5 minutes ago, Jascha said:

So the reason for Generator Failure in my case was most likely the use of engine anti-ice heaters together and PZU? Are the negative effects of NOT using anti-ice or PZU when supposed to, simulated right now in this module?

As for anti-ice mode MANUAL/AUTO - this is separate from the engine heaters, right?

Thanks for the video link.

No, the actual reason why you got the generator failiure, was because you let the main rotor RPM fall below 87% (absolute minimum 85%). The reason is that generators are connected to the main rotor. However, when you engage PZU and anti-ice, it pulls more energy from the engines, effectively reducing the engine's available power for driving the main rotor alone. Consider that generators connected to the main rotor will act as a physical load, and more so when higher electricity levels are required.

 

Simply put, one of those instruments that you have to monitor constantly, is the main rotor RPM. You do that, and reduce the collective when rotor RPM falls close to 87% (again, 85% absolute minimum), and you're good. Remember, that much of the success surrounding successfull helicopter operations, is correctly planning for weight depending on the flight profile. There are restrictions on MTOW depending on weather, temperature, altitude, etc. This has to be closely considered by a helicopter pilot prior to commencing the mission.

[AeriaGloria]

Anti ice takes 17% power, and PZU about 2.5% 

The ice detector turns on and off constantly no matter what becuase it will warm the ice detector while the warning goes off, it will stop warming it after a while and see if it freezes again. As long as it’s going on and off you are in freezing conditions. It’s not a “my engines and rotor are freezing” detector it’s a “you are in freezing conditions detector while I turn off and on.” 
 

If anti ice is off long enough it will reduce engine power and cause possible shut down or fire

1 hour ago, Jascha said:

I had the same issue when playing Mi-24P YoYo's campaign. When entering mountain area, at higher altitude, I noticed that air temperature is close to 0C. I have enabled the clock heater, pitot heater (left and right) and also left and right engine anti-ice heater. Anti-Ice system mode was set to auto (if I understand correctly this switch controls only the anti-ice system for the rotor blades). After 10 minutes or so, I noticed the icing warning light - it was on despite everything being set as described above. It went off after some time. Later, when descending, despite the temperature rising, the warning become visible again. Before trying to perform a vertical landing, I enabled the PZU. Shorty after right engine RPM dropped a bit and soon the "Generator Failure" message could be heard. I have lost all AP settings, rotor RPM dropped to 80% iirc and I almost crashed. Somehow I managed to transition into the forward flight and everything went back to stable.

My questions are:

- How we should actually use anti-icing system in this situation? Is this system modeled properly at current state of the module?

- How exactly does the anti-icing affects the Mi-24P performance? Can it be used together with the PZU?

- Should the battery heater be on in this situation? Does it have some impact on Generator Failure?

- How to fix this situation when close to the ground? Lowering the collective is not really an option.

Could you please explain this in more detail?

Right pedal increases tail rotor pitch, witch puts more load on your rotor rpm 

Miki posted the video in transient torque spikes above, but yes right cyclic will reduce rotor rpm and left will do opposite, it depends on rotor rotation direction. So right turns will push the rotor rpm more, left turns will push it less 

This is why your left turns, all things being similar, will be 20-30 kmh faster then any right turn 

[Jascha]

17 hours ago, zerO_crash said:

Simply put, one of those instruments that you have to monitor constantly, is the main rotor RPM. You do that, and reduce the collective when rotor RPM falls close to 87% (again, 85% absolute minimum), and you're good.

Ok, thanks. To be honest I haven't been paying much attention to this indicator, as I assumed rotor RPM is auto-controlled anyway. I was focusing more on the pressure ratio indicator.

I'll review the track once more to see what exactly went down.

17 hours ago, AeriaGloria said:

Anti ice takes 17% power, and PZU about 2.5% 

17% or 1.7%? The first figure seems crazy high. This applies to blades anti-ice or engine heaters too?

17 hours ago, AeriaGloria said:

If anti ice is off long enough it will reduce engine power and cause possible shut down or fire

If its "off" or "on" for too long? Since you mentioned fire this seems to be more likely to happen due to overheating and not freezing or am I missing something?

As for the generator failure, I understand that I should turn off anti-ice in situations where I need to increase power (collective up), especially when hovering, correct?

What are the rules for using PZU? When should it be turn off (after take-off) or on (before landing)?

[zerO_crash]

32 minutes ago, Jascha said:

Ok, thanks. To be honest I haven't been paying much attention to this indicator, as I assumed rotor RPM is auto-controlled anyway. I was focusing more on the pressure ratio indicator.

I'll review the track once more to see what exactly went down.

 

When it comes to Russian aircraft, helicopters in this case, for the engines, you need to monitor three gauges specifically - engine RPM, engine temperature and EPR. The last one, is the least important, but you still have to monitor it and be within the limits, if you are flying realistically and replicating what is SOP in the Russian army/air force. Additionally, it's important to check the temperature gauges related to the drives and oil pressures on the upper right side once in a while (every 15-20 minutes). That's for the engine part.

 

When it comes to flying however, rotor RPM is one of the most important gauges you have to watch. Depending on the flight regime, maneuver, you will never have enough engine power to maintain one constant engine RPM across the whole flight envelope. Understand that the EEG/FADEC/fuel regulators, do as best as they can do keep the rotor RPM within the designated limit, but they won't be able to hold it, when you are already running the engines at maximum RPM. It's also important to make the distinction here that Russian and US helicopters are inherently different in design. US helicopters run their rotor at pre-set 100%, and the pilot has to monitor any increase or decrease outside of what the regulators can handle himself. In the Russian helicopters, the common standard is to have the rotor operate within 85% - 100% RPM, however there are small variations. One can argue for or against one or the other, however it stems from a difference in design philosophy. One of the main advantages of the Russian way, is that the pilot always knows which side of the spectrum the rotor is (lower or higher), meaning that he will be pre-emptivly prepared with proper reaction. On the other side, in US helicopters, you really only monitor the torque gauge for engine operation (outside of occasional checks on temperatures and oil). Regardless, rotor RPM is what you have to monitor non-stop, regardless of helicopter. IRL, you hear little through muffled helmets, and as such, you often notice technical problems from the main gauges, one being rotor RPM. It's an important habit to have.

Edited February 5, 2024 by zerO_crash

[zerO_crash]

1 hour ago, Jascha said:

17% or 1.7%? The first figure seems crazy high. This applies to blades anti-ice or engine heaters too?

If its "off" or "on" for too long? Since you mentioned fire this seems to be more likely to happen due to overheating and not freezing or am I missing something?

As for the generator failure, I understand that I should turn off anti-ice in situations where I need to increase power (collective up), especially when hovering, correct?

What are the rules for using PZU? When should it be turn off (after take-off) or on (before landing)?

 

Also, yes, 17%! For the Mi-24 and Mi-8, when engine and rotor anti-ice system is running, the maximum take-off weight is reduced by 1000kg. When PZU (particle dust separators) are running alone, the reduction in take-off weight is 200kg.

 

Lastly, AeriaGloria didn't quite clarify it. When you engage rotor anti-ice due to icing conditions, there are bound to be chunks of ice around the engine inlets. Those can either melt gradually, or fracture and get sucked into the engine. If a big enough piece of ice get's sucked, then what happens is actually a flamout due to disruption of air from the compressor and towards the cumbustion chamber. That's one possibility. Another one, is that it damages the engine inside, causing fire due to catastrophic engine failiure. In this case, you got fire. It's also important to remember that the automatic anti-ice, only works for right engine. The reason why it doesn't work on both engines, is exactly what's mentioned above. If the system engaged anti-ice on both engines simultaneously, you could potentially risk a dual engine failiure, which is a very different emergency, than having one engine run autmatically anti-ice and failing, while the other one still works. Becuase of this, when automatic anti-ice comes on the right engine, you have to wait circa 5 minutes, ensure safe operation of right engine, before you engage anti-ice on the left one. That way, you ensure at least one operating engine, should a flamout or fire occur.

 

If you need extra power, be it hovering or flying (increase altitude before passing a mountain), you can always turn off anti-ice to gain that extra power. However, don't let it run too long, as you will get icing on the engines, and that is a sure catastrophic failiure to happen. Generally speaking, a 5 minute rule is a good on to go by. It's 5 minutes between turning on anti-ice for both engines, five minutes maximum operation without anti-ice in icing conditions. You'll be good to go. 

 

EDIT: Just to make it clear, I described the Mi-8's automatic anti-ice system. In the Mi-24, that system engages both engines autmatically, due to only the pilot and CPG sitting at the instruments. The crew chief is more often than not, not on board, meaning that as a safety measure, for the pilot not forget to turn on one of the engines manually, the automatic system works on both engines. In this case, the probability of forgetting to turn on anti-ice manually for one engine, is higher than the probability for both engines to cease working at the same time.

Edited February 5, 2024 by zerO_crash

[Jascha]

Thanks. Very informative.

2 hours ago, zerO_crash said:

Just to make it clear, I described the Mi-8's automatic anti-ice system. In the Mi-24, that system engages both engines autmatically, due to only the pilot and CPG sitting at the instruments.

That is still not clear to me. Yes there is automatic anti-ice mode, but engine anti-ice heaters seems to be manual only, as they have independent switches:

And they have separate notification lights:

It seems to me that the first switch with manual and auto mode controls rotor blades anti-ice system only. But I'm nut 100% sure.

[Screens taken from Chuck's Guide for Mi-24D.]

[AeriaGloria]

Yes Zero_crash is incorrect. The only anti ice function that is automatic is for rotor blades. I also don’t know what you mean about the rotor rpm, in the Mi-24 and Mi-8 the rotor rpm is held by a governor to maintain 95% +/-1-2%. 
 

45 minutes ago, Jascha said:

Thanks. Very informative.

That is still not clear to me. Yes there is automatic anti-ice mode, but engine anti-ice heaters seems to be manual only, as they have independent switches:

And they have separate notification lights:

It seems to me that the first switch with manual and auto mode controls rotor blades anti-ice system only. But I'm nut 100% sure.

[Screens taken from Chuck's Guide for Mi-24D.]

so yes. If you flip auto switch up, when you enter icing, only the main and tail rotor anti icing turns on. You can see this happen with their respective indicator lights

Zero_crash described the Mi-8 procedure, which is totally different from Mi-24 procedure where you turn on both engines at the same time.
 

And you are also right, the engine anti ice is completely manual. The reason this is different then Mi-8 is because instead of reacting to icing warning, for Mi-24 you are supposed to turn on anti icing under 5 degrees Celsius no matter what. However, in DCS you won’t have icing degrade engine performance until 0 degrees Celsius, so you’ll be fine as long as you turn on engine anti ice at 0 degrees or below to “protect” the engines from anti ice. Things like ice chucks from turning it on after ice forms isn’t modeled in DCS, only the slow degradation of engine performance that happens if engine anti ice stays off. Nothing bad happens if you keep rotor anti ice off either. It only draws power more. 

The 17% is a lot, so it’s totally fine to keep it off for takeoff/landing or other times a short term power excursion is needed 

l

Edited February 5, 2024 by AeriaGloria

[zerO_crash]

13 minutes ago, AeriaGloria said:

Yes Zero_crash is incorrect. The only anti ice function that is automatic is for rotor blades. I also don’t know what you mean about the rotor rpm, in the Mi-24 and Mi-8 the rotor rpm is held by a governor to maintain 95% +/-1-2%. 
 

so yes. If you flip auto switch up, when you enter icing, only the main and tail rotor anti icing turns on. You can see this happen with their respective indicator lights

Zero_crash described the Mi-8 procedure, which is totally different from Mi-24 procedure where you turn on both engines at the same time.
 

And you are also right, the engine anti ice is completely manual. The reason this is different then Mi-8 is because instead of reacting to icing warning, for Mi-24 you are supposed to turn on anti icing under 5 degrees Celsius no matter what. However, in DCS you won’t have icing degrade engine performance until 0 degrees Celsius, so you’ll be fine as long as you turn on engine anti ice at 0 degrees or below to “protect” the engines from anti ice. Things like ice chucks from turning it on after ice forms isn’t modeled in DCS, only the slow degradation of engine performance that happens if engine anti ice stays off. Nothing bad happens if you keep rotor anti ice off either. It only draws power more. 

The 17% is a lot, so it’s totally fine to keep it off for takeoff/landing or other times a short term power excursion is needed 

l

 

 

I am looking it up, and with regards to the anti-ice in the Mi-24, yes, my bad. On the anti-ice panel (right console by the pilot's door), the left most switch is for rotor anti-ice, beside it the "force anti-ice off" button, and next to that, two switches (one for each engine) to turn on/off the anti-ice. So yes, it is fairly different from the Mi-8 in this case.

 

As to the main rotor RPM, I mean exactly what I write. While the rotor will be mostly held in the "95% +-1%/2%"-range when cruising level, as soon as you start maneuvering, or performing any kind of high-performance turns, the main rotor will be moving outside of that range. The maneuvers can be anything from acceleration/deceleration, hovering (heavy loaded), reducing/increasing altitude quickly, etc... Even when you go faster (speed), you will see that pushing the helicopter in speed, you'll lower the main rotor RPM. The manual for pretty much any Russian helicopter gives under "operating limitations" the permissable high's and low's during different phases of the flight. This is encountered during normal flight, combat/high-performance flight, and emergency.

 

As to not turning on anti-ice, I'm fairly sure that you can get a engine fire, if you leave it off for too long in icing conditions. Not turning on anti-ice for the main/tail rotor, degrades performance. I'm am fairly sure of it.

[AeriaGloria]

52 minutes ago, zerO_crash said:

 

I am looking it up, and with regards to the anti-ice in the Mi-24, yes, my bad. On the anti-ice panel (right console by the pilot's door), the left most switch is for rotor anti-ice, beside it the "force anti-ice off" button, and next to that, two switches (one for each engine) to turn on/off the anti-ice. So yes, it is fairly different from the Mi-8 in this case.

 

As to the main rotor RPM, I mean exactly what I write. While the rotor will be mostly held in the "95% +-1%/2%"-range when cruising level, as soon as you start maneuvering, or performing any kind of high-performance turns, the main rotor will be moving outside of that range. The maneuvers can be anything from acceleration/deceleration, hovering (heavy loaded), reducing/increasing altitude quickly, etc... Even when you go faster (speed), you will see that pushing the helicopter in speed, you'll lower the main rotor RPM. The manual for pretty much any Russian helicopter gives under "operating limitations" the permissable high's and low's during different phases of the flight. This is encountered during normal flight, combat/high-performance flight, and emergency.

 

As to not turning on anti-ice, I'm fairly sure that you can get an engine fire, if you leave it off for too long in icing conditions. Not turning on anti-ice for the main/tail rotor, degrades performance. I'm am fairly sure of it.

 The rotor rpm deviates from 95% +/-2%, so really 93-97%. It is for a few reasons. But generally, the governor will do everything it can to keep it right at 95% 

1. If lower then 93-97% it is becuase the engines do not have enough power to maintain the rpm at the commanded rotor collective pitch. Or that they lag and need time to accelerate. Or even transient torque spikes from right pedal and right cyclic 

2. If rotor rpm is higher then 93-97%, it is becuase the engines can’t rev down enough or fast enough to stop the rotor from going to fast, such as in a fast pitch up 

3. You messed with the “turbine adjust rpm” switch on the collective, which changed the governor setting from 95% to as low as 91% or as high as 97-98%. You adjust the governor with this switch, which you often need to do depending on air pressure if it deviates significantly according to manual

If you rotor rpm is deviating from that 93-97% it is for one of those three reasons. I can go to 320 kmh and still maintain 95% rotor rpm. The governor is always trying to maintain it, unless it doesn’t have enough power to overcome the rotor drag, too much rotor inertia/speed that it can’t slow down engine enough, or you deliberately play with the switch that changes governor setting.
 

The sentence in the manual about allowable rotor rpm is for a few reasons 

1. The manual knows that pilots may push collective pitch, or right pedal/cyclic and lower rotor rpm, and that this is allowed to a certain extent, with a rough cutoff of 87%
 

2. The manual knows that pilot may pitch up fast or get into conditions where the rotor rpm goes up too much or too fast for the governor to stop it, and 103% is the hard limit here becuase of the rotor or generator structural limits 

3. It flies best at 95% rpm, and the less the rotor rpm gets the more sluggish its response, the more pitch and thus more torque is needed. The manual even describes it being okay to raise rotor rpm with the “turbine adjust rpm” switch at high altitudes to increase tail rotor authority, or to decrease it to 92-93% with the same switch to help save 2-3% fuel in cruise 

You will find that if you let off collective pitch enough for the engines to have enough power to drive the rotor at 95%, it will do so and keep it there no matter your speed, attitude, or maneuvers. The only exception being transient torque spikes from right cyclic/pedal 

From manual: “When deflecting the collective pitch lever, the gas generators RPM of both engines change, the main rotor RPM are maintained within 95 +/-2% automatically;”

Anytime in the checklist or emergency procedures it wants you to check for best rotor rpm at any speed, it asks you to make sure it is 95% +/-1-2%, and this is how it acts in game except it very perfectly keeps it right at 95% 

Edited February 5, 2024 by AeriaGloria