Generator Failure

[Jascha]

58 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.

Yeah, there is force anti-ice OFF switch for quick disconnection. I think this only affects the rotor blades anti-ice system (which must be then set to manual and back to auto to be turned on again), but I have to verify this.

As for the 17% power consumption - I wonder if this figure relates to rotor anti-ice system AND engine heaters together. As I understand rotor blades heating system is electric and engine (intake) heating system is based on hot air.

As for the main topic of generator failure, I have reviewed the track. It's too large to upload it here. But I have recorded the video while watching it.

It's a bit long as I have included the descent, you can skip to ~4-5 min.

As it turns out I had engine heaters on with PZU but rotor anti-ice was not on when generator failed. Then shortly after enabling the PZU the right engine RPM and temperature drops a bit, shortly after rotor RPM falls below 85%. Then I was trying to gain control of the aircraft with max right rudder input (it was barely working, letting it spin left would most likely end up in a crash).

If you can find some time to review it and explain to me what exactly happened, I'd be grateful. Are engine heaters the main culprit here? Or some other factors too (PZU probably, but it had to be enabled in these conditions, other than that maybe the wind?).

Edited February 5 by Jascha

[AeriaGloria]

19 minutes ago, Jascha said:

Yeah, there is force anti-ice OFF switch for quick disconnection. I think this only affects the rotor blades anti-ice system (which must be then set to manual and back to auto to be turned on again), but I have to verify this.

As for the 17% power consumption - I wonder if this figure relates to rotor anti-ice system AND engine heaters together. As I understand rotor blades heating system is electric and engine (intake) heating system is based on hot air.

 

You are correct, the anti ice off button only affects rotor anti ice. 
 

Let me clarify some of power bleed and update my numbers, 

PZU removes 125 hp from each engine, or 200 kg of takeoff weight. This is equal to about 5.6% of the 2,225 HP engines. 
 

All anti ice together removes 700 kg takeoff weight, which is equal to about 20% power. However; 150 kg of this is for rotor anti ice. If you keep rotor anti ice off but only use engine anti ice, it will use about 15-16% power. 
 

I will take a look at your video and see what I can find 

Edited February 5 by AeriaGloria

[AeriaGloria]

Okay, watching your video, your generator failed becuase your anti ice just used up so much power, and you used so much collective your engines couldn’t sustain the rotor rpm

. Becuase you had less power then normal, you needed more collective pitch to compensate. This means you also needed more right pedal to counter the torque, which increases tail rotor drag and further lowers rotor rpm. It looked like it wanted to come back and got close to 90%, but wasn’t able to fully recover as you stayed in a condition that required a lot of power (too much collective for your engines burdened with anti ice.)

This is why in the manual, it mentions you might want to turn anti ice off for takeoff, landing, or any situation that needs high power for a short period of time. Sometimes I only use one engine anti ice if I want to compromise. I think if you had turned off engine anti ice, or entered an envelope that had a smaller power requirement (which does get worse at high altitude, which it seemed like you were at). 

19 minutes ago, Jascha said:

As for the main topic of generator failure, I have reviewed the track. It's too large to upload it here. But I have recorded the video while watching it.

It's a bit long as I have included the descent, you can skip to ~4-5 min.

As it turns out I had engine heaters on with PZU but rotor anti-ice was not on when generator failed. Then shortly after enabling the PZU the right engine RPM and temperature drops a bit, shortly after rotor RPM falls below 85%. Then I was trying to gain control of the aircraft with max right rudder input (it was barely working, letting it spin left would most likely end up in a crash).

If you can find some time to review it and explain to me what exactly happened, I'd be grateful. Are engine heaters the main culprit here? Or some other factors too (PZU probably, but it had to be enabled in these conditions, other than that maybe the wind?).

 

 

Edited February 5 by AeriaGloria

[Jascha]

11 minutes ago, AeriaGloria said:

Okay, watching your video, your generator failed becuase your anti ice just used up so much power, and you used so much collective your engines couldn’t sustain the rotor rpm

. Becuase you had less power then normal, you needed more collective pitch to compensate. This means you also needed more right pedal to counter the torque, which increases tail rotor drag and further lowers rotor rpm. It looked like it wanted to come back and got close to 90%, but wasn’t able to fully recover as you stayed in a condition that required a lot of power (too much collective for your engines burdened with anti ice.)

This is why in the manual, it mentions you might want to turn anti ice off for takeoff, landing, or any situation that needs high power for a short period of time. Sometimes I only use one engine anti ice if I want to compromise. I think if you had turned off engine anti ice, or entered an envelope that had a smaller power requirement (which does get worse at high altitude, which it seemed like you were at). 

 

 

Great explanation. Thank you.

So my main mistake was to leave engine anti-ice on. Since there is no automatic mode for it (as far as I know) and this system uses so much power, how should it be operated? In icing conditions rotor anti-ice in auto mode work in cycles, the engine anti-ice seems to be most likely continuously on when switches are up. Should I cycle it manually in regular flight?

PS. Oh, and the right engine RPM dropping slightly was caused by engine anti-ice being on too? I wonder why it affected only the right engine.

 

Edited February 5 by Jascha

[zerO_crash]

1. I am fully aware why the rotor RPM lags behind the engines in certain aspects of the flight. You might as well explain it for yourself, because the situations I referred to, are the ones which will provoke the rotor RPM to lag behind, or stay ahead of the engine RPM resulting in fluctuations beyond the preset 95%. If anyone asks, one might explain to them. However I, made it perfectly clear as to what and when. Transient torque is only ONE example, vortex ring state (uncommon as it is) is another. A third would be pulling high levels of acceleration or deceleration (albeit the former is more prononced, as with deceleration, assuming altitude is to be kept, is done at low collective levels, resulting in little effect on rotor speed.). Again, I see no purpose on building this out, as it only solidifies what I claimed.

 

2. I didn't mess with the "free turbine readjustment". No one ever stated it, as such, I do not see where you pull this conclusion from. Many factors affect rotor RPM, as such, trying to pick the anatomy of it apart, with little information to spare, bears little purpose and relevance. With regards to the "free turbine readjustment"-switch, also known as "engine trim switch", there is a very specific procedure regarding it, and that is at startup. You state that it has to be used if "deviates significantly according to manual". Well, no! It has to be performed upon every single startup. When the engines are fully started up, with engine condition levers set to normal, the pilot is supposed to pull collective equal to 3* degrees of blade pitch (AOA), and trim the rotor RPM to 95%. Whether it deviates significantly or not, is your wording, not according to ED or IRL manuals. Thus, it's being done each and every startup, as part of a check. With regards to other uses of this switch, yes, you are right in that one can lower the main rotor RPM in cruise flight in order to save fuel. That is however not the only case, another one would be descending with a higher rate of descent, in order to further create a larger margin for not over revving the main rotor. This is yet another example, just to be complete about it. Again, no one mentioned this switch, I see no relevance here (unless it was used wrong).

 

3. As mentioned prior, when flying in combat, within the envelope of the helicopter, one is perfectly able to move the main rotor RPM away from the default 95%. That happens regardless of helicopter. One thing is manual, another thing is real life and practical applications of the theory. There are more than enough recounts in Russian, where pilots show just how they pushed the aircraft to its limits, and sometimes beyond in combat. There are more than enough videos online as well, showing real life applications in combat, and why for example the rotor RPM is free floating to a degree, given the maneuver performed.

 

4. To clarify it, there is not "a sentence in the manual about allowable rotor RPM speeds" - there is a table showing it! I suggest you take a good look at the manuals again, as this is a very important component of flying. One is not to fly aircraft as if they are stolen (rip the controls apart), however in such a dynamic environment, one is required to often maneuver outside of daisy trips. We can go into the details, be my guest. I have however never given any specifics, here I recommend reading the manuals, because there are many factors to consider, not only engine RPM and main/tail rotor RPM. I never stated how much it deviates, just that it deviates from the 95% +-2%. Sometimes, it's even more than the stated 2%, and that is only due to a short lag of the system. At the end, as I always said as an instructor in real life; "It's not dangerous to do a given action, as long as you know what you are doing.". The danger lies, in doing something, you simply have no idea or knowledge about. That's why, teaching a pilot/driver/captain his craft, isn't only about manuals (in big part it is), but also about teaching them what to look out for, get the feel for it in a safe and controlled environment (instructor overwatch and step in, in case of danger) and ultimately, become familiar with the handling qualities and what to expect.

 

Again, there really is no discussion here. You need to read up on this matter (what I gather from you stating). This is very essential for extracting the most out of the aircraft. Attached are supplements from manuals of Mi-8MTV2 (albeit with the TV3-117VM and VR8 gearbox, it applied to more than just our MTV2), Mi-24D and Mi-35P. Notice, that in certain cases, the permissable, and even max. RPM goes down with speed (mostly a maintenance consideration with regards to bearings of the rotor heads and blades) or flutter (there are more considerations to be made). If you've flown at 320km/h with 95%, then you have actually had 1% higher main rotor RPM, than what the manuals stipulate. It's not dangerous, and these rules are broken IRL often, as there is only so much a pilot can physically monitor, but if we're specific, then yes!

EDIT: 1st graph is from a Mi-24 manual (general) from 1976.

         2nd, 3rd and 4th graphs, are from ED's Mi-8 manual.

         5th graph is from Mi-35P operators manual.

         6th graph is from Ka-50 ED's manual.

 

I could list many more, but they are all in Russian. To keep the thread clear, I post only one (Mi-24) manual which is Russian.

 

50 minutes ago, Jascha said:

Great explanation. Thank you.

So my main mistake was to leave engine anti-ice on. Since there is no automatic mode for it (as far as I know) and this system uses so much power, how should it be operated? In icing conditions rotor anti-ice in auto mode work in cycles, the engine anti-ice seems to be most likely continuously on when switches are up. Should I cycle it manually in regular flight?

PS. Oh, and the right engine RPM dropping slightly was caused by engine anti-ice being on too? I wonder why it affected only the right engine.

 

 

 

No, it is never a mistake to leave anti-ice on, if you need it that is. The mistake was, you were too heavy for a flight in that weather. That's the way to think about it. You could have solved that problem in a different way. Most helicopters (count in those that we have in DCS), climb most efficiently at 130km/h indicated airspeed. You were flying at approximately 250km/h. If you had reduced your airspeed to 130km/h, or at least lowered it, you would have needed less power to sustain altitude, as well as climb. There are many things to consider, being decent pilot requires knowing the manual/rules with some experience, being a good pilot adds more experience, however being a superb pilot, requires being clever about how you deal with problems. Another thing that I notice, is that it seems to me like you didn't set your barometric altimeter to QNH, rather QFE. The area you are in, does not look to be at the height of the ocean. Neither does it make sense that, regardless of loadout, with less than 50% fuel, you struggle to maintain hover. Remember to set your barometric altimeter to QNH, otherwise, you will have a wrong perception on what altitude you are at, and thus misjudge whether you can enter hover, or not.

Edited February 5 by zerO_crash

[Jascha]

14 minutes ago, zerO_crash said:

No, it is never a mistake to leave anti-ice on, if you need it that is. The mistake was, you were too heavy for a flight in that weather. That's the way to think about it.

Well the aircraft in this case had no external stores whatsoever and only ~900L fuel left. It's hard to imagine that normally it was to heavy to transition into hover.

15 minutes ago, zerO_crash said:

You were flying at approximately 250km/h. If you had reduced your airspeed to 130km/h, or at least lowered it, you would have needed less power to sustain altitude, as well as climb.

Yeah but eventually I'd have to transition into hover anyway which requires more power that the engines were not able to provide due to working anti-ice system draining it. At least that's how I understand it.

[zerO_crash]

12 minutes ago, Jascha said:

Well the aircraft in this case had no external stores whatsoever and only ~900L fuel left. It's hard to imagine that normally it was to heavy to transition into hover.

Yeah but eventually I'd have to transition into hover anyway which requires more power that the engines were not able to provide due to working anti-ice system draining it. At least that's how I understand it.

 

You had some stores, as I'm seeing at least ATGM's (Kokoon/Ataka) at 0:51 in the left mirror (tubes on wingtip). That's not completely empty, but if that's all, then it's light. Again, the key here is the result of all components. Altitude, to name one. Also, yes, you would have to come to hover, but you could do it at lower altitude, somewhere outside of that mountain range. No one demands that you land on top of Mt. Elbrus, if you cannot guarantee a safe hover. If a pilot IRL would e.g. work on OEI (one engine inoperational), then if he took off from a FARP, he could as well talk with the traffic controller and divert to an airfield with runway, or land on a road. Again, it's about being clever.

 

Understand me properly, if you intended to land anyways on top of that hill, then sure, for the duration of the landing, turn off anti-ice. However, in general, if there are icy conditions, you ought to consider going lighter loaded, and in certain cases forget hovering, as it will pose an elevated danger. I cannot see if you had too much wind in the mission, but that is yet again something you could have considered - to land head on wind. It will increase your lift coefficient and allow for landing, even when normally without wind, you would be advised against it.

 

Understand that aircraft, and their operations, are so complex in nature, that you cannot always do what you had decided for. When Soviets were flying Mi-24's out of Bagram, often, in order to take off, they had to go as light as they could, and lift as a plane (with forward movement). Their whole sortie, including landing was performed like a plane. Not once, could they hover at the altitudes over there (2km+), otherwise it would be a controlled crash-landing. That's why Mi-8s, which have greater MTOW and are generally optimized for lift - not speed, were often used to transport troops/equipment. The Mi-24 is optimized for speed, and those wings that you have, are doing you a very bad favour in hover. This helicopter loves speed, more than any other that we have in DCS, or IRL for that matter. Again, know your strengths, AND limitations. It's essential.

Edited February 6 by zerO_crash

[AeriaGloria]

2 hours ago, Jascha said:

Great explanation. Thank you.

So my main mistake was to leave engine anti-ice on. Since there is no automatic mode for it (as far as I know) and this system uses so much power, how should it be operated? In icing conditions rotor anti-ice in auto mode work in cycles, the engine anti-ice seems to be most likely continuously on when switches are up. Should I cycle it manually in regular flight?

PS. Oh, and the right engine RPM dropping slightly was caused by engine anti-ice being on too? I wonder why it affected only the right engine.

 

 

I’m sorry, I didn’t mean to imply that anti ice used more power over time, it was not a mistake to leave it on. Just that it means you have nearly 20% less power going to your engines, so you get low rotor rpm much easier from the less power. Less power going to rotor = less collective pitch can be used  

Currently in DCS, the right engine decreases in power from anti ice much more. I’m not sure if that’s accurate, but that’s why EPR and PTIT will show different values for them. There are great hover charts that show how much altitude and temperature gives you hover performance, but they are not for anti ice

Charts are from Chucks guide 

Edited February 6 by AeriaGloria

[AeriaGloria]

2 hours ago, zerO_crash said:

1. I am fully aware why the rotor RPM lags behind the engines in certain aspects of the flight. You might as well explain it for yourself, because the situations I referred to, are the ones which will provoke the rotor RPM to lag behind, or stay ahead of the engine RPM resulting in fluctuations beyond the preset 95%. If anyone asks, one might explain to them. However I, made it perfectly clear as to what and when. Transient torque is only ONE example, vortex ring state (uncommon as it is) is another. A third would be pulling high levels of acceleration or deceleration (albeit the former is more prononced, as with deceleration, assuming altitude is to be kept, is done at low collective levels, resulting in little effect on rotor speed.). Again, I see no purpose on building this out, as it only solidifies what I

 

EDIT: 1st graph is from a Mi-24 manual (general) from 1976.

         2nd, 3rd and 4th graphs, are from ED's Mi-8 manual.

         5th graph is from Mi-35P operators manual.

         6th graph is from Ka-50 ED's manual.

 

I could list many more, but they are all in Russian. To keep the thread clear, I post only one (Mi-24) manual which is Russian

 

I am aware of all these charts and manuals, I have read Mi-24A/D/V/P and 35M manuals ranging from 1976 to 2011, believe me, I am aware of these. 
 

This chart does not say the governor changes the RPM it holds, only that at takeoff power, to expect it’s rpm to be on the lower side as you are pushing the limit of the engine. There is no “switch” in the system that changes the governor RPM based on power level. You can fly in DCS plenty on takeoff power with 95% rotor rpm or higher, but it’s often on the lower end becuase you are pushing your engine to limit and it can’t always give more to balance the increasing drag of more rotor pitch. 
 

In that chart, the manual is telling you what to expect on average, not that the governor lowers rotor rpm automatically when you enter takeoff power

I only mention the turbine adjust rpm and transient torque as potential causes for why you see rotor rpm as low 87-88% in flight. Outside of those, in steady state conditions, the governor will command max engine power below 94% and command less engine power above 96%, trying its hardest to keep rotor rpm in that 95% +/-1-2% range as much as it can and this is what you see in DCS also. 

Edited February 6 by AeriaGloria

[zerO_crash]

31 minutes ago, AeriaGloria said:

I am aware of all these charts and manuals, I have read Mi-24A/D/V/P and 35M manuals ranging from 1976 to 2011, believe me, I am aware of these. 
 

This chart does not say the governor changes the RPM it holds, only that at takeoff power, to expect it’s rpm to be on the lower side as you are pushing the limit of the engine. There is no “switch” in the system that changes the governor RPM based on power level. You can fly in DCS plenty on takeoff power with 95% rotor rpm or higher, but it’s often on the lower end becuase you are pushing your engine to limit and it can’t always give more to balance the increasing drag of more rotor pitch. 
 

In that chart, the manual is telling you what to expect on average, not that the governor lowers rotor rpm automatically when you enter takeoff power

I only mention the turbine adjust rpm and transient torque as potential causes for why you see rotor rpm as low 87-88% in flight. Outside of those, in steady state conditions, the governor will command max engine power below 94% and command less engine power above 96%, trying its hardest to keep rotor rpm in that 95% +/-1-2% range as much as it can and this is what you see in DCS also. 

 

Nor have I ever stated that the governor detracts from whatever one trims the engine at. I stated very clearly, that in an ideal world, 95% wouldn't even need a margin of +-2%, but in the real world, due to maneuvering, lag in the system, potential lack of/or too much power, and frankly physics, the rotor will move outside of even the +-2%, and that is perfectly fine! This topic is originally talking about "generator failiure". I mention, that one of the reasons for losing generators, outside of a mechanical failiure, is the main rotor RPM falling below 85%. That is not a recommendation to fly such that the main rotor RPM lowers to 85%, that is simply a technical limitation. The manual sets a practical operational minimum of the main rotor RPM at 87%, and that to have a buffer, but the technical limitation is 85%. Still, during any flight, with heavier maneuvering or not, you will see the main rotor RPM move outside of 95%, and even the stipulated +-2%. That's how helicopters work. Any other helicopter (AH-64 or UH-1H) is no different in this respect, other than different thresholds and available power levels (typically lower hp/tonne).

 

Since the virtual pilot here is unaware why he gets generator failiure, the simple answer is; he let's the main rotor RPM droop below 85%. Now, how to mitigate this issue, is another thing, and I have already recommended him what he should and shouldn't do. It's important to attack the issue where it occurs and before, and not after it affects.

 

I guess you confused yourself by assuming much here, by arguing against claims that have never been made. The devil lies in the details - semantics. You also argued not understanding the main rotor RPM moving out of the 95% range in flight. I made it very clear; during cruise flight, it will hold it, but during a complicated flight profile, it will move up and down, depending on what you perform.

 

At this point, the issue is solved.

Edited February 6 by zerO_crash

[Mermoz]

I had it a couple of times today too. But I know why.

Helicopters need to be piloted smoothly and after an afternoon of dogfight in WW2 planes I got used to yank the stick. As a result I was too rough with the cyclic.

If you are too brutal with the controls you put additional torque on the rotor and if you put too much its RPM will momentarily drop. If it happens the generators loose power since they run on the rotor shaft.

in the AH64 if you yank the cyclic too brutaly you will get the "rotor RPM low" warning.

I'm pretty sure I got it in the Hind too but I don't understand russian so not sure what Mirovska was telling me.

if you have the problem too often maybe add a curve to your axis setting to give you more smoothness  and limit your inputs. it may help you avoid the situation