VRS

[Dima89]

I know this topic has been covered a thousand times but I'm struggling to find a real comprehensive answer.

 

I've been flying the Mi-8 for a short amount of time now, I don't have the Huey so I have no experience to fall back on in that regard, and I am struggling quite a bit with landing due to VRS.

 

I suspect I am killing speed off too early and at too high an altitude and then trying to descend around 3m/s before I plummet to the earth...Repeatedly. Highly annoying.

 

What sort of speed should I be looking to approach a FARP at and to what rate of descent? I've had a look on YouTube for some tutorials and what not but struggling to find what I am after in English!

 

(Or if someone has a bit of time on their hands, would it be possible to write out a full procedure/checklist for approach?)

 

Thanks,

D

Edited January 26, 2014 by Dima89
Addition

[Suchacz]

No offence, but if theory of it is already known to you, then without track or video further debate will be only an unuseful chit-chat...

Edited January 26, 2014 by Suchacz

[Cruiser18]

When I wanna do landings with the MI-8 that doesn't look overly cautious and slow, I tend to find that I always use the same method.

 

As I approach my landing zone going at some 250 km/h, I usually drop my collective quite a bit to loose altitude and at the same time I pitch back to kill speed. I keep the collective low to make sure that I dont gain a lot of altitude while braking down.

 

While i am doing this, I keep an eye on the gauge indicating how fast I'm ascending or descending (dont remember its name) and try to keep it around 5 m/s descending. This is usually pretty straight forward.

 

Once I get below 40 km/h forward speed, the descending speed will increase dramatically though, DO NOT LET THIS HAPPEN! I cannot emphasize how important it is that you keep an eye on the descend needle when you approach 40 km/h. It will litterally go from steady 5 m/s, to +20 m/s within a few seconds if you are not paying attention and drop you like a rock.

Adjust with A LOT more collective to keep your descend speed at around 5m/s.

 

From there it should be somewhat easy to put your MI-8 down. When you get close to the ground, keep a descend speed of about 2-3 m/s, and preferrably if you keep a forward momentum of around 5-10 km/h that lets you keep an eye on what you are landing.

[Dima89]

If theory of it is already known to you, then without track or video further debate will be only an unuseful chit-chat...

 

Yes, I know what you are saying, but theory and practical are two different matters! :D

 

I will record a track and post it, I hadn't thought to do that but it will probably help more.

 

 

When I wanna do landings with the MI-8 that doesn't look overly cautious and slow, I tend to find that I always use the same method.

 

As I approach my landing zone going at some 250 km/h, I usually drop my collective quite a bit to loose altitude and at the same time I pitch back to kill speed. I keep the collective low to make sure that I dont gain a lot of altitude while braking down.

 

While i am doing this, I keep an eye on the gauge indicating how fast I'm ascending or descending (dont remember its name) and try to keep it around 5 m/s descending. This is usually pretty straight forward.

 

Once I get below 40 km/h forward speed, the descending speed will increase dramatically though, DO NOT LET THIS HAPPEN! I cannot emphasize how important it is that you keep an eye on the descend needle when you approach 40 km/h. It will litterally go from steady 5 m/s, to +20 m/s within a few seconds if you are not paying attention and drop you like a rock.

Adjust with A LOT more collective to keep your descend speed at around 5m/s.

 

From there it should be somewhat easy to put your MI-8 down. When you get close to the ground, keep a descend speed of about 2-3 m/s, and preferrably if you keep a forward momentum of around 5-10 km/h that lets you keep an eye on what you are landing.

 

That's the sort of thing I was looking for, I will give it a go working to this.

[Suchacz]

I will record a track and post it, I hadn't thought to do that but it will probably help more.

Ok, great. I (we) will be glad if I (we) can help :thumbup:

[canadianbaken]

Follow Cruiser18 advice and practice practice practice . It took me a long time to get the hang of landing the Huey and the Eight has a lot more power than the Huey. Just try and get low and into ground effect before bleeding off all your speed.

[lmp]

Keep in mind that the VVI has some lag. If you're losing ETL rapidly (slowing down rapidly) and thus your descent rate is rising quickly, the VVI may still show you a safe 3m/s when you've already accelerated to, say, 5m/s. To prevent it slow down more gradually and keep a wider margin of error (descent at 1 - 2m/s) at least until you gain a better feel for the helicopter. Also, the hover and low speed control indicator (the instrument in the top right corner of the pilot-commander's instrument panel) also has a VVI that I think is less laggy. I try to keep both my pressure and doppler vertical velocities in the "safe zone".

[Dima89]

Right, just made a quick track following Cruiser18's advice, although compared to you veterans it is poor, it felt a huge improvement for me and I actually managed to get the thing down in one piece!

 

https://mega.co.nz/#!MAZ3RL7Z!attA9qpcWyZE5DjX6Terx4uKpxfZSraq0Tn-FORzmKg

 

@Imp - Ah, I have been wondering what that instrument was! I've been meaning to check but it slipped my mind, going to have a snoop for some more information on that.

Edited January 26, 2014 by Dima89

[Cruiser18]

Good to hear. Any landing you can walk away from is a good landing ;)

[159_Archer]

Yeah -what Cruiser said -as you get to 40kph you need to work the collective to make up for loss of forward lift. You might find the helo judders a bit but once the speed goes the lift isn't coming from your forward movement and thus more collective is required.

 

If you watch any youtube vids of helos on approach, you'll see the pilot watching his instruments like a hawk -you need to also!

[TimeKilla]

Just before entering VRS, you'll feel the copper shaking and the RoD will increase very fast, I normally increase collective just there and catch it before we enter VRS its a little hit or miss and I suppose it's not the best way to enter a hover from forward flight.

 

Been flying the Huey and Mi8 since day one and it's something am not sure of even though I've watched countless videos and read countless documents on the subject.

[fjacobsen]

I think the best way to land both the Mi-8 and the UH-1 is to approach the runway/landingspot is to make the approach as You would do in a fixed wing aircraft i.e "glideslope" should be appr. 3°.

 

The hardest thing is not to come in too high, cause that will add too much workload for You.

 

As You slow down be prepared to add more collective and even be prepared to add more than You think, just don´t add so much that You start to climb.

 

Start the approach from a greater distance and take Your time to decellerate and descend.

[TimeKilla]

Yep thats the easy way only problem is going from forward flight to hover should be something every helicopter pilot can do and can do well. thats why it bothers me so much and likely others.

[lmp]

@Imp - Ah, I have been wondering what that instrument was! I've been meaning to check but it slipped my mind, going to have a snoop for some more information on that.

 

You mean the hover and low speed control indicator (that's how it's called on the DCS website anyway)? It's a great thing to have when landing, as the name suggests. Bellow about 40kph of IAS your (horizontal) velocity indicator will become unreliable because of the helicopter downwash. And, as I said, your vertical velocity indicator is laggy. The hover and low speed control indicator remedies this somewhat. It's part of the DISS-15 doppler navigation system and it tells you your forward (up to 40kph), sidewards and backwards (up to 25kph) velocity as well as vertical velocity. The big "inverted cross" thing in the middle is your horizontal velocity scale and the arc on the left side is the vertical velocity scale. One thing to keep in mind though, the doppler navigation system uses ground speed (GS), not air speed (IAS) - wind and altitude may cause your IAS to be significantly different from your IAS.

[Slazi]

Practice moving from speed into hover at height. That way, if you mess it up, you can pull out of the VRS. Just add lateral speed and you'll recover. Once you get good at doing it higher up, then work on landings.

[Dima89]

Massive help, thanks all.

[esb77]

As a beginner there are two strategies for safe VRS avoidance that work pretty reliably even before you get the feel for the helicopter.

 

1. Run on (aircraft style) landing with enough airspeed so you never loose ETL before touchdown. About 50 km/h in the Mi-8.

 

If you're worried about a FARP not having enough room for your skill level, consider looking to see if there's a safe landing area nearby that you land at and then hover taxi to the FARP.

 

2. High altitude (say at least 100m above highest obstruction) transition to hovering flight. Gives you enough time and space to get back out of VRS if you get into it during the transition. You have to be gentle with the controls after you've made the transition, it may not work at high altitudes, high temperatures, high humidity, and high helicopter cargo loadings. It's also very hard on the engines in real life if you do it a lot.

[fjacobsen]

I cannot recommend situation 2.

 

The normal reason why users get into VRS is because they come in too high and thus try to get down with too high a descend rate.

 

Pattern altitude should be around 1000 feet AGL.

Sart the approach so far out that You get ample of time to both descend at a low rate and bleed of airspeed at the same time. Keep VS< 3m/s, especially below 100 km/h.

[GunfighterSIX]

If you guys are trying to do running landing to avoid VRS then there is something wrong. Just keep your speed up if you have high rates of descent. You can land the helicopter straight down if you want. Just keep the your rate of descent below 200 to 300 FPM. If you are low on power, which is what is kill most people, not VRS. Then stay above ETL until you are in ground effect. (one rotor disk about the ground) ETL is 16 to 24 Knots, so always land into the wind. If you have 10 knots of wind, then you may only need a few knots of ground speed to keep about ETL. And keep you approach slow but above ETL and start father out. Set up early and keep the rotor loaded. Don't come in fast with the engines spoiled down then try to pull the guts out of it. Then engines wont be able to catch up, your rotor will droop and you will fall out of the sky. Then you will be on the forms crying about VRS when you were never in it. You just stopped flying. VRS is not really the problem for most of you, its power management. If descent rate is high keep speed up. If speed is slow keep descent slow. Plain ever move and stay ahead of the helicopter. Sorry I didn't convert units for you guys.

 

I also dont agree with situation 2

 

Helicopter pastern in USA are 700 feet AGL though. FAR AIM

Edited January 27, 2014 by GunfighterSIX

[fjacobsen]

The pattern altitude I mentioned was only approximatly....

 

Using a higher descend rate at higher speeds is no problem, but inorder to learn landing a helo from a hovering position, it´s a good idea to focus on the descend rate.

 

Comming in too high or too fast simply means that You will have to do too many things at once during the final seconds before getting into hover.

 

Making a shallow approach means that You will have less adjustments of the collective and thus better focus on managing speed and rate of descend.

 

Comming into high will often make You feel urged to descend faster and at the same time slow down and that will often overload You and make You loose focus on either speed management or descend management.

 

It all boils down to understand the "Deadmans curve" or more specific the "Height-velocity diagram":

http://en.wikipedia.org/wiki/Height%E2%80%93velocity_diagram

 

While the one shown in the link shows it as "Take off profile" it still holds true for landing.

 

Just note that in the mi-8 airspeed is in Km/h, Altitude in meters and V/S in m/sec.

 

This is not only to avoid VRS but also in case of engine failure.