Landing the Hip

Not true. Engine RPM is constant in a helicopter. There's no reason why you can't suddenly add lots of power, and the only time you'll get a blade stall is if you enter VRS.

Squirrel, I think you got a few things mixed up there:

1. Engine RPM varies depending on the torque demand. That's just how gas turbines work: low torque / power demand -> low RPM. high demand -> high rpm.

2. Yes, there are good reasons not to add "lots of power suddenly". Gas turbines can surge and stall, when their operational limits are exceeded. And by that loose power immediately.

3. You don't need to get into VRS to get a blade stall. Try flying faster than Vne and you'll get a (retreating) blade stall.

I suggest you try the following: 100m height, maximum weight, maximum speed. Now, reduce collective pitch down to zero. You'll notice the engine rpm decreasing down to 70%. Keep altitude by pulling on the cyclic. Once you reach 70km/h, quickly add collective pitch up to 7-9°. You'll see, the engine won't be able to keep up with the torque demand and only rev up slowly, while the rotor RPM may drastically decrease. This is, when you end up in a blade stall.

In order to maintain airflow and lift at high rotor pitch, you need a high forward speed of the rotor. But with the rotor RPM decreasing rapidly you end up in a blade stall.

And yes, it's fun trying stuff in the sim. And you can achieve all kinds of results - but that doesn't necessarily mean this would work in real life.

Then again, everyone has a different approach to simulations.

Start planning your landing WAAAY before you get there. Like a mile away and I am not joking.

I'd also add: Go slow, and plan your approach in your head before you commit.

Additionally, something often overlooked by us simmers: Practice auto-rotations. Not just the one's that are set up from 1000m altitude, but practice auto-rotations at all points in a flight - take off, approach, cruise, attack run-ins, hard turns, different weight loads, etc. Just shut off your fuel and get down to business.

By practicing auto-rotations, this will condition you to always be on the look out for ideal landing spots at all times. Put the 'look for good spot to land' in your cockpit/outside scan, and it becomes second nature.

Having the auto-rotate skill in my toolbox, helped me tremendously with regular landings.

Yes, autorotations are so important. I like to setup a scenario with an engine failure at random time. DCS is great for that kind of training.

As for my tips for landing- practice, that's it. Make sure you don't descent too quickly (it's all metric in this helicopter!). Also practice controlling rudder as it gets little bit violent as soon as you losse ETL. Reference your landing spot with a spot on the windsheld, and keep it more or less there during approach. Also go slow and avoid rapid de acceleration, keep it smooth. You will learn how to be more dynamic with practice.

I hardly think this is modeled realistically, but you can put a single infantry soldier on average difficulty and he will more often than not shoot you out of the sky with an M4 or AK-74 if you overfly him.

Most of the time he will take out at least one engine. You will see the RPM's drop on it and hear a noticeable change in pitch.

And yes, it's fun trying stuff in the sim. And you can achieve all kinds of results - but that doesn't necessarily mean this would work in real life.

 

Then again, everyone has a different approach to simulations.

The other thing is...how can you know what is realistic or what not (or what you would do in real life) when you're not a real pilot? I can just "guess". From the behaviour of the Hip (compared to the Huey), I definitively tend to fly the Hip more carefully. However, you can still thread her a bit less gently if needed. Also, from my testing on the platform, I had to noticed that it's not easy to do such a manoever.

The other thing is...how can you know what is realistic or what not (or what you would do in real life) when you're not a real pilot? I can just "guess". From the behaviour of the Hip (compared to the Huey), I definitively tend to fly the Hip more carefully. However, you can still thread her a bit less gently if needed. Also, from my testing on the platform, I had to noticed that it's not easy to do such a manoever.

Well, I never said I was not a real pilot. Understanding turbine engines and aerodynamics and being able to interpret operating handbooks helps a lot. Other than that I know Russian language well enough to read books on the topic and talk to type rated Mi-8 pilots.

Yeah, we simply have a complete different background. I'm simply "just" a gamer with no avionik background at all.

Squirrel, I think you got a few things mixed up there:

 

1. Engine RPM varies depending on the torque demand. That's just how gas turbines work: low torque / power demand -> low RPM. high demand -> high rpm.

2. Yes, there are good reasons not to add "lots of power suddenly". Gas turbines can surge and stall, when their operational limits are exceeded. And by that loose power immediately.

3. You don't need to get into VRS to get a blade stall. Try flying faster than Vne and you'll get a (retreating) blade stall.

 

I suggest you try the following: 100m height, maximum weight, maximum speed. Now, reduce collective pitch down to zero. You'll notice the engine rpm decreasing down to 70%. Keep altitude by pulling on the cyclic. Once you reach 70km/h, quickly add collective pitch up to 7-9°. You'll see, the engine won't be able to keep up with the torque demand and only rev up slowly, while the rotor RPM may drastically decrease. This is, when you end up in a blade stall.

In order to maintain airflow and lift at high rotor pitch, you need a high forward speed of the rotor. But with the rotor RPM decreasing rapidly you end up in a blade stall.

I think we can learn from each other here actually. I'm half way through getting my helicopter license so I have some understanding of helicopters, but I expect you have better knowledge of the Mi8.

I just tried the DCS Mi8 again and you're right, there is engine RPM variation, thanks. I'd never noticed this before, and didn't know that any helicopters did this. Do you fly the DCS Huey? In the Huey the rotor and engine RPM are (generally, unless you're throwing it around) constant, and thought this was the case for all helicopters as this is what I've read in my text books. A good reason why every helicopter requires a type rating I guess!

You missed something out about gas turbines though: gas turbine pressure. You can have constant RPM and varying torque by varying fuel flow. Even with an engine running at constant RPM, more fuel, higher temperatures and pressures, more torque. This is how the Huey etc can fly with constant engine RPM through the whole flight, despite changes in torque demand.

You're right about retreating blade stall of course; I was just thinking stall in terms of power application. My bad.

Your last point I'm not so sure about. I think the reduction in rotor RPM resulting from rapid collective lowering then raising and subsequent loss of lift isn't the blade stalling; I think what you're experiencing is overpitching.

Interesting stuff.

I just tried the DCS Mi8 again and you're right, there is engine RPM variation, thanks. I'd never noticed this before, and didn't know that any helicopters did this. Do you fly the DCS Huey? In the Huey the rotor and engine RPM are (generally, unless you're throwing it around) constant, and thought this was the case for all helicopters as this is what I've read in my text books. A good reason why every helicopter requires a type rating I guess!

Huey does a very good job of maintaining turbine RPM. I assume it's accurate, but I have nothing to compare with. However, rotor RPM varies significantly with blade pitch. This should be very noticeable in-game.

--gos

I hardly think this is modeled realistically, but you can put a single infantry soldier on average difficulty and he will more often than not shoot you out of the sky with an M4 or AK-74 if you overfly him.

 

Most of the time he will take out at least one engine. You will see the RPM's drop on it and hear a noticeable change in pitch.

You must hang around getting shot at for a long time..

My experience is that most of the time you hear those rounds plinking the bodywork, but nothing gets damaged (which is fair enough, if you look at the parts that are not cockpit, they're mostly shell).

However, rotor RPM varies significantly with blade pitch. This should be very noticeable in-game.

No it doesn't. Look at the engine/rotor tacho (in the Huey). Both needles sit in narrow green bands at the top of the gauge, and this is where they'll stay unless you do something to really upset the heli.

Huey does a very good job of maintaining turbine RPM. I assume it's accurate, but I have nothing to compare with. However, rotor RPM varies significantly with blade pitch. This should be very noticeable in-game.

 

--gos

If you haven't already, you should check out the 2 videos this guy made testing the UH-1. I didn't have time to find the timestamps, but he did some tests and there was one situation where RPMs did not perform properly, and others when they did..

I think he has a 2nd video on the Huey as well.

Very well done.

No it doesn't. Look at the engine/rotor tacho (in the Huey). Both needles sit in narrow green bands at the top of the gauge, and this is where they'll stay unless you do something to really upset the heli.

Same as with the Mi-8. If you yank the collective, main rotor RPM will drop as the electric governors cannot inject fuel fast enough into the turbines for them to counteract the suddenly requested torque demand.

The whole concept of gas turbine engines and their governors is to keep engine RPM in a small bandwidth that allows for one specific rotor RPM regardless of collective setting and keep it there. Any upsetting of this balance and the system will reset itself to the stable condition it was programmed to. If you upset the balance by a large amount, engine RPM will drop and main rotor RPM will drop as well.

would giving autopilot adjustment orders to engineer help specially before/during landing phase to keep things "smooth" ?

is this done in real life?

If the autopilot is at the edge of its authority you will not get a uniform response to your stick inputs throughout the whole range of movement - if that makes sense. So yes, you want the autopilot adjusted before landing. Just make sure you ask for it before you leave ETL and flare. You don't want to worry about it when you're trying to slow down to a hover.

No it doesn't. Look at the engine/rotor tacho (in the Huey). Both needles sit in narrow green bands at the top of the gauge, and this is where they'll stay unless you do something to really upset the heli.

Agree, you can overload the turbine/rotor to split needles on turbine/rotor RPM, but why?

Can only vouch for Huey and Gazelle so far. :thumbup:

practice practice practice...

You must hang around getting shot at for a long time..

 

My experience is that most of the time you hear those rounds plinking the bodywork, but nothing gets damaged (which is fair enough, if you look at the parts that are not cockpit, they're mostly shell).

Nah, you'll get tagged routinely on a strafing run. Set up with a guv pod and go over a group of five insurgents on average skill level. Go back and forth on strafing runs going out of range then coming back in until you get them all. You will see that you get tagged up really good.

could've used this thread about a year ago. all good stuff, that I learned the hard way... :-)

thanks for the informational posts.

The other thing is...how can you know what is realistic or what not (or what you would do in real life) when you're not a real pilot? I can just "guess". From the behaviour of the Hip (compared to the Huey), I definitively tend to fly the Hip more carefully. However, you can still thread her a bit less gently if needed. Also, from my testing on the platform, I had to noticed that it's not easy to do such a manoever.

Yes this is true of the Hip, I am much gentler with this machine than any other DCS Helicopter Module. All landings are thought about and planned on approach or whilst circling, from wind direction to ground obstruction to hasty egress if VRS may be entered. I do not do this with any other DCS Chopper.

@rge75,

Yes more or less what I meant, although you did it on an elevated platform and missed the opportunity to drop down into ground effect until you were over the platform. Being in ground effect while in steep bank does nothing and you dont get to VRS in a bank since the rotor wont sink into its own air. But as you reduce bank angle and speed, you can start settling and being in ground effect helps to not settle too fast and enter VRS.

@Viktor UHPK

Does this look a gently flown Mi-8 and not like an agile attack helicopter to you? :)

@Flamin Squirrel

Engine RPM in a helicopter is not constant, but the design tries to keep the RPM as consistent as possible within the acceptable range. You are not adding lots of power, you are increasing the pitch of the blades.

Under certain circumstances it is quite possible to increase the pitch of the blade so rapidly that the RPM decreases due to the increased torque and the engine cant maintain RPM. The blade is still biting heavily at the air but now since the rotor is slowing down the lift decreases, the RPM keeps dropping, the lift decreases more and by now you have warning lights and buzzers going off and you have started descending. You either reduce the collective/pitch of the blade and let the RPM increase then try to fly it out or you keep descending.

This can happen in hover or forward flight at high weights and is not VRS, although in hover or close to hover this condition can turn into VRS. More akin to settling with power and the recovery is more or less the same at low speeds/hover.

@rge75,

Yes more or less what I meant, although you did it on an elevated platform and missed the opportunity to drop down into ground effect until you were over the platform. Being in ground effect while in steep bank does nothing and you dont get to VRS in a bank since the rotor wont sink into its own air. But as you reduce bank angle and speed, you can start settling and being in ground effect helps to not settle too fast and enter VRS.

Looks like I'll have to try it at Normandy in that case :joystick:. I agree, the missing ground effect didn't make it easier with the oil platform.

Okay first time Mi 8 flyer and yes easy is the word and steady is the action.

Gotta RTFM :lol:

Wot read the flight manual. :D

Engine RPM in a helicopter is not constant, but the design tries to keep the RPM as consistent as possible within the acceptable range. You are not adding lots of power, you are increasing the pitch of the blades.

 

Under certain circumstances it is quite possible to increase the pitch of the blade so rapidly that the RPM decreases due to the increased torque and the engine cant maintain RPM. The blade is still biting heavily at the air but now since the rotor is slowing down the lift decreases, the RPM keeps dropping, the lift decreases more and by now you have warning lights and buzzers going off and you have started descending. You either reduce the collective/pitch of the blade and let the RPM increase then try to fly it out or you keep descending.

 

This can happen in hover or forward flight at high weights and is not VRS, although in hover or close to hover this condition can turn into VRS. More akin to settling with power and the recovery is more or less the same at low speeds/hover.

Read what I wrote properly. I said that you can upset a heli to cause rotor RPM to fluctuate, but in normal operating conditions, RPM will remain constant. That's what a governor is for.