Forward IAS changed to backward IAS when trying to completely redude airspeed

[yonyz]

I have a serious problem getting my helicopter to stop so I could engage auto-hover.

 

When I pull the stick backwards and thus the helo by about 30 degress (I don't think the degree matters, though) with an airspeed of say 60 km/h (forward), after a few seconds, that speed (or slightly less) becomes my backwards speed, and I really don't know how to deal with it. I think it's like the third law of physics. It's really frustrating. I'm finding myself entering vortex rings and what have you, simply by trying to stabilize the aircraft at zero airspeed.

 

I have seen tutorial videos about hovering, and it actually looks very easy in those videos. The instructors seem to have no difficulty at stopping the helo at precisely 0 km/h. Wish I could do that, so I could finally aim my weapons without having to fight the movement of the helo.

 

Another problem is that, when I increase the angle of attack, I can't help but also slightly bank. I just find it hard to move the stick straight backward without also slightly moving it on its lateral axis.

 

Please, HELP. :D

[Sarge55]

Yonyz,

The guys in the videos have probably logged hundreds of hours on the sim and may actually be pilots IRL so don't expect to emulate them right away.

 

For slowing down to 0 km/h just take it a bit slower and in smaller steps even from 60 km/h, after time you will get a better feel for it. Try to anticipate your next hover point and start slowing sooner.

 

The lateral drift is proably something to do with aerodynamics (Some one better qual than I could probably explain it). I notice this as well and just use my rudder to off set it.

[26-J39]

You will need to keep an eye on your forward speed and vertical speed. When you pitch up to slow down you will need to reduce your collective to maintain altitude, as the helo slows more collective will be needed to maintain altitude. It's essential here to use you vertical airspeed ind so you don't enter a vortex ring. The velocity vector on your HUD is a good aid also.

Velocity Vector. When airspeed is below 50 kph, a velocity vector line is drawn from the center of the Aircraft Datum. This line points in the direction that the aircraft is traveling and the length of the line represents the aircraft‟s relative speed. The line will be longest when the aircraft is traveling at 50 kph in any direction and shortest when the aircraft is at or near a hover. The Velocity Vector line is a useful tool when used in conjunction with the Hover Point Deviation Marker to hold a battle position.

[Chrischn89]

It took me a while to master Autohovering too. It isnt really simple but I guess I can give you some advice:

 

Be warned as you will have to pay attention to many things simultanously ;) (but we are pilots after all so thats what we always do right?)

 

1. To avoid gaining too much altitude while pitching up to slow down you should reduce the collective to about 10%.

 

2. While slowing down you must keep an eye on the VSI. It is crucial that you dont fall under roughly 400m/minute as this will get you into vortex state when reaching slower speeds! To achive this you must constantly add collective as the lower speed results in less lift produced by the rotors.

 

3. Also try to minimize any changes in bankangle and check your speed (for very detailed speed information you can use the ground speed indicator in the ABRIS information box).

 

4. Reaching 40 Km/h you are able to engage Autohover-mode. Press the Autohover-button and (this is kind of odd) reset your trim. This will result in a somewhat abrupt up pitching in most cases but is necessary so that the Autopilot can stabilize without any input by the pilot.

 

5. You should also consider deactivating the Altitude Hold mode as it will give you far more control over your vertical velocity to avoid the vortex state.

 

6. In order to get it to a perfect hover you must reset the trim again to set a new reference point for the autopilot until it is finally stalbe (most of the time there will still be a backward velocity. You can minimize it by holding a pitch of around -3° and trim it but only after you ensured that the helicopter doesnt yaw or bank anymore)

 

And thats it :)

 

Hope this helps

[Henchman14]

There is a virtual speed tape strip that appears sometimes ( I can't remember exactly in what modes ) in your upper left part of your HUD. It shows when you are at speed. It disappears when you are nearing standstill. So, when it disappears, you know you are going slow and should start trying to carefully come to a stop. Its easy to overshoot and start going backwards, which the three digit speed indicator will show just as if you were going forwards. Watch your HSI ( The thing with the crosshair). When you hit Auto-Hover on, it will show your drift from the initial point. Try to bring the copter as steady as you can, then hit the trimmer. The point will reset, and probably start drifting again slightly. You might be in a wind, and have to bank into it to stay over a point. Trimmer again, and keep doing it till the heli stays where it is. Remember, the auto-pilot only has 20% control over the heli. So, it can only give 20% push over the cyclic, rudder, and collective. If your drifting up or down, hitting F will reset the altitude for the altitude hold. If it doesn't stop, then go up or down on collective as needed to steady, then hit F again. F is the brake on the collective.

 

Another thing to remember when at height. IAS is what your dial indicator shows, but I think the numbers in the hud show TAS, which is different. At height, TAS is a more true indication of your real speed, and IAS will show lower than it really is, which mean its easy to cross your blades before the warning alarm for speed goes off. Also, don't do hard right rudder at high speed. Do left rudder. This will keep your blades from crossing. Right brings them together. Left pulls them apart.

Edited January 15, 2011 by Henchman14

[bogusheadbox]

WHats wrong with the good old "mark 1 eyeball"

 

When pitching up to a hover, just look sideways, its one of the best indicators.

 

Then all you need is a quick glance at vsi to ensure you are not going to enter vortex ring state.

 

 

N.b. you can also engage auto hover when moving forward. Even at 60klm/h Just ensure you reset (by pressing trim) the auto hover when almost stop to keep from drifting backwards

[yonyz]

I'm not familiar with the HSI and VSI. I should read the cockpit part of the manual first.

 

bogusheadbox, looking sideways is one of the best indicators of what exactly?

[GGTharos]

4. Reaching 40 Km/h you are able to engage Autohover-mode. Press the Autohover-button and (this is kind of odd) reset your trim. This will result in a somewhat abrupt up pitching in most cases but is necessary so that the Autopilot can stabilize without any input by the pilot.

 

Sorry but, worst advice ever. You keep trimming as you slow down to MAINTAIN flight parameters. You don't reset.

 

6. In order to get it to a perfect hover you must reset the trim again to set a new reference point for the autopilot until it is finally stalbe (most of the time there will still be a backward velocity. You can minimize it by holding a pitch of around -3° and trim it but only after you ensured that the helicopter doesnt yaw or bank anymore)

 

And thats it :)

 

Hope this helps

 

That's more sound advice, except for 'reset'. You don't reset anything. You set trim to a new position.

[bogusheadbox]

bogusheadbox, looking sideways is one of the best indicators of what exactly?

 

Forward movement.

[Kite]

this what's helped me

From high speed nose up a lot as you do

but as speed is decreasing I put reduce pitch a bit and trim

next to the speed I want I reduce again and trim

at about 0 again nose to zero pitch and trim

them autohover

You have to check always vvi.

Instrument are very important

bye

[yonyz]

Thanks guys, I'm a lot more successful at engaging hover now.

[yonyz]

You will need to keep an eye on your forward speed and vertical speed. When you pitch up to slow down you will need to reduce your collective to maintain altitude, as the helo slows more collective will be needed to maintain altitude. It's essential here to use you vertical airspeed ind so you don't enter a vortex ring. The velocity vector on your HUD is a good aid also.

The term "vertical airspeed indicator" confuses me. Are we talking about the Vertical Velocity Indicator or Airspeed Indicator? Or is there another gauge called Vertical Airspeed Indicator?

[Henchman14]

He means the Vertical Velocity Indicator. You don't want to drop too fast at a hover ( I wouldn't go past 5 Meters / Sec ), or you end up falling into your own spent down wash, and drop like a rock. The best way I've found to get out of it is bank hard sideways. Seems to get you out of it faster, than banking forward. Of course, if your too close to the ground, your just dead.

[yonyz]

I always "escape" vortex rings by pitching forward. Usually I have enough altitude to do that, but knowing another method couldn't hurt, so thanks.

[bogusheadbox]

VSI is vertical speed indicator - Acronym is VSI. Perhaps the term VVI is refering to the same instrument but terminology defferent for different countries ? Here (england - who knows what the french do these days ;-) )in Europe and Australia - we call it a VSI

 

 

Anyhow its the one just left of the shkval with a 0 at "9 O'clock position on the face" and tells you how quick you are climbing or decending.

Edited January 17, 2011 by bogusheadbox

[yonyz]

Anyhow its the one just left of the shkval with a 0 at "9 O'clock position on the face" and tells you how quick you are climbing or decending.

Yup, that's the VVI.

[26-J39]

Sorry for the confusion :) Yes i meant the VVI/VSI same thing.

[yonyz]

So I need to keep the VVI as close to zero as possible? At what rate of descent does the helo enter an uncontrollable vortex ring?

[Henchman14]

If your near hover, usually greater than 5 meters / second. There's actually a switch on the collective ( you have to use a keypress in game ) that lets you down at a sustained 2 or 3 meters per second, to keep you from accidentally entering Vortex Ring. It will stop you at 4 meters radar altitude. If your moving fast, you can of course descend faster ( I've done dives at 30 meters / second easy ) because your leaving the spent air behind you and quickly moving into fresh air. The other thing you want to watch out for, do not descend below 4 meters radar altitude in auto hover, or you will lose your autopilot, which is not good in this not so stable helicopter. I guess emergency autopilot release kicks in. Your autopilot buttons will be flashing.

[yonyz]

Thanks for the intel (TF2 reference). :)