30 to 0 Knots

[Caldera]

Hey All,

I have noticed something that seems odd, but I do not know for sure.  I am looking for opinions.

For example, say that I am attempting a spot landing.  And lets say that is is on a FARP so I have a limit touch down area that I must hit.  During this process I am applying more and more aft cyclic, while at the same time managing power so that my glide slope intersects my landing spot.

As I am dropping altitude and speed I notice that:

• 50 knots --> I am good
• 40 knots --> I am good
• 30 knots --> I am good
• >30 knots --> the reverse thrusters engage

So as I exit flight and begin transition to a hover I am adding power.  Some where under just 30 knots the speed drops off much more quickly than it had been doing at just above that critical speed.  If I am not absolutely on top of it, then I will rapidly go from forward flight to backward flight.

Why is that?

Caldera

Edited June 17, 2022 by Caldera

[Grennymaster]

under 30 knots the bird gets very "unstable" evety input that you make has big effekts. A lot of factors are counting here. Wind, Humiditi, weight of your Bird, temp. etc.

i try to explain how i do my approches

try to trimm your bird a bit over 40knots as stable as you can get. take your time. when going under the 35 mark try to do as little inputs as possible. Talking about mm movements, dont forget that you are flying an very heavy bird with an realativ big rotordisc.

slowly give left rudder, let it set an go again a bit more. You also need to be very gently on the collektive. if you overdo inputs it will be a very bad bird

I hove you understand what i try to explain, its hard to write down

Also check out Casmos Channel on Youtube, he is an formen Apache Pilot an explains everthing very very good. Helped me out a lot.

[mcfleck]

I think the key word is "during this process I apply more and more aft cyclic".
You are not supposed to do that. Try to keep your aft cyclic constant and have a constant declarative attitude. By applying more and more aft cyclic you increase the deceleration.
Compare it to a car: you can either apply some force on the brake pedal and keep it constant until you stop and maybe even release it slightly at very slow speeds to prevent the head nod... Or you can apply more and more force on the pedal the slower you go. What will happen in the latter case? The declaration is getting stronger the slower you go.

Generally speaking your aerodynamics change once you drop below approx 30 kts. and all sorts of things happen. Luckily the transverse flow is not simulated, because that would mean a pretty noticeable tendency to drift to the right (additional to the simulated translating tendency to the right).
I was told that your perceived speed looking out of your side window should be as fast as a brisk walk all the way through your approach. I have to admit that it is quite hard to estimate that without using VR though

This procedure here describes perfectly how you would learn it in a flight school:
https://forum.dcs.world/index.php?/topic/296437-AH-64D-Flight-School-(w/-Track-Files)#entry4941039

[Razor18]

The more your main rotor is tilted backwards (aerodynamically), the more force is "pulling" your helo backwards. This force decelerates your helo. If you keep it that way all the way until your speed is zero, you are already late to the party, because you will only stop for a second, as with your stick back the main rotor still apply huge decelerating/backward force, so you will immediately transit to backwards flight after stopping. You can see the diretion and strength of this "force" on the Transition (and on the Hover) symbology, when you look at the small circle, that is wandering around the centre. So as you near stopping (I would say around 30 kts, after applying more collective to compensate loss of transitional lift, you should start push the stick forward again to bring the helo back to neutral pitch instead of nose high attituda, so by the time the helo stops, there should be no more backward rotor tilt/stick pull, and the small circle should be in the centrer, or as close to it, as possible.

Edited June 19, 2022 by Razor18

[gav88888]

Slowing to a hoover has been a big issue for me since the start, although ATT hold seemed to help stabilize the process a bit but since the last update this hold no longer helps, just seems to make things worse if anything. I am hoping the next update with ALT hold will help. I have spoken to Wags who thinks its a hotas issue as he has no issues. I don't know though as my mate is a helo pilot and uses the same hotas a me and he also has issue. We can also fly the other helos without issue. Lets see how things progress as it develops more...

[Raptor9]

Attitude Hold won't help you since it will switch to Velocity Hold once you are below 30 knots.

[PilotNeedGunner]

You're thinking about the relationship between velocity, cyclic, pedal, and throttle input in a linear fashion. Also, the way to fly a helicopter is not to wait until something happens before you react, as this will lead to always chasing the equilibrium. Rather, you want to anticipate what the helicopter will do for any given input and counter it with opposing input before the helo responds. In a hover for instance, you simultaneously apply left pedal while raising the collective. In above ETL forward flight, you may need to apply forward cyclic to keep level flight as well as left pedal when adding collective. Don't wait until you see the helo rotating right before applying counteracting input. This goes for transitioning from forward flight to hover during landing as well. As you approach the landing zone and getting slower, you'll need to apply more collective to arrest descent all the while applying more left pedal. As you get below ETL, you'll have to reduce or increase pitch up attitude depending on your closure rate and account for translating tendency by more applying left cycling as well. As you get used to the helicopter's behavior you begin to recognize the telltale signs of when you need counteracting inputs. Hope this helps.

Edited June 22, 2022 by PilotNeedGunner

[DmitriKozlowsky]

On 6/17/2022 at 3:05 PM, Caldera said:

Hey All,

I have noticed something that seems odd, but I do not know for sure.  I am looking for opinions.

For example, say that I am attempting a spot landing.  And lets say that is is on a FARP so I have a limit touch down area that I must hit.  During this process I am applying more and more aft cyclic, while at the same time managing power so that my glide slope intersects my landing spot.

As I am dropping altitude and speed I notice that:

• 50 knots --> I am good
• 40 knots --> I am good
• 30 knots --> I am good
• >30 knots --> the reverse thrusters engage

So as I exit flight and begin transition to a hover I am adding power.  Some where under just 30 knots the speed drops off much more quickly than it had been doing at just above that critical speed.  If I am not absolutely on top of it, then I will rapidly go from forward flight to backward flight.

Why is that?

Caldera

 

When going below ETL speed (about 20 knots indicated), put nose into wind as much as mission (at that time) allows. Definitely, when landing, hover taxi, T_ACQ hover, point helicopter into wind. With tail wind, it will be unstable and twitchy. Use trim system to steady the helicopter.

[TrevorMcNeill]

 

On 6/22/2022 at 1:32 AM, DmitriKozlowsky said:

When going below ETL speed (about 20 knots indicated), put nose into wind as much as mission (at that time) allows. Definitely, when landing, hover taxi, T_ACQ hover, point helicopter into wind. With tail wind, it will be unstable and twitchy. Use trim system to steady the helicopter.

When you're below 50ft takeoff and landing you need to be nose in direction of landing/departure (ie runway)as to prevent dynamic rollovers, once over 50ft then keep aircraft in trim. Also 16-24kts for ETL

[DmitriKozlowsky]

38 minutes ago, TrevorMcNeill said:

 

When you're below 50ft takeoff and landing you need to be nose in direction of landing/departure (ie runway)as to prevent dynamic rollovers, once over 50ft then keep aircraft in trim. Also 16-24kts for ETL

Helicopters take off and land into the wind. Unless you are so heavy that you need a rolling takeoff. A helicopter may be directed by ATC onto runway, but there is no requirement or need to take off linearly along runway as fixed wing. Even if you need a rolling takeoff you can diagonal across runway in a helicopter. Fly helicopter as helicopter, not as fixed wing.

[Razor18]

And how much degree you can correct by rolling "diagonal" on a 2-3 km long, 100 m wide runway? 2-4 degrees?...

Edited June 24, 2022 by Razor18

[DmitriKozlowsky]

You can roll quite a good distance . Not that you need much in a helicopter. For GW get above ETL, and as soon as helicopter is light on wheels pedal nose into wind, and correct for dynamic roll with cyclic deflection. If you need long roll, or can't hover in ground effect, you are too heavy for safe flight, and certainly you can't fight. 

[Raptor9]

31 minutes ago, DmitriKozlowsky said:

and as soon as helicopter is light on wheels pedal nose into wind, and correct for dynamic roll with cyclic deflection.

You try that in real life and you will ball up your aircraft. If you are able to do that in DCS, there's probably something wrong.

[DmitriKozlowsky]

Works, in DCS for wheeled geared helicopters. More difficult with skids, due to dynamic roll risk.

[Raptor9]

19 minutes ago, DmitriKozlowsky said:

Works, in DCS for wheeled geared helicopters. More difficult with skids, due to dynamic roll risk.

Sounds like the wheels in DCS are coated with oil or jelly then. Tires should have more friction than a skid, unless the skid has some sort of rubber boot installed on the underside itself.

I've done roll-on landings in helicopters with skids and helicopters with tires, and when the nose is cocked off to one side when landing with tires, it's a much more traumatic event than one with skids.

Edited June 25, 2022 by Raptor9

[DmitriKozlowsky]

Safest is proper approach with fwd speed (relative to landing spot), with near zero fwd speed at touch down. Difference is when deck landing, which I am practicing in Apache, is slow fwd approach to parallel the deck spot. Then side fly over the spot to IGE hover and settle down on spot. Navy/USMC style. Looking at deck qualls of Army Apaches on LHA on YT, sometime they land and T/O with slight angle to the deck . However Marine AH-1W and AH-1Z land straight.   

[Raptor9]

8 minutes ago, DmitriKozlowsky said:

 Looking at deck qualls of Army Apaches on LHA on YT, sometime they land and T/O with slight angle to the deck . However Marine AH-1W and AH-1Z land straight.   

If you are talking about landing with zero relative airspeed to the deck, then yeah, of course the nose direction doesn't matter. I was responding to your earlier comment here:

2 hours ago, DmitriKozlowsky said:

You can roll quite a good distance . Not that you need much in a helicopter. For GW get above ETL, and as soon as helicopter is light on wheels pedal nose into wind, and correct for dynamic roll with cyclic deflection.

If landing or taking off with forward speed, you keep the nose pointed in the same direction as your flight path.

[Scaley]

1 hour ago, Raptor9 said:

Sounds like the wheels in DCS are coated with oil or jelly then. Tires should have more friction than a skid, unless the skid has some sort of rubber boot installed on the underside itself.

They absolutely are. You can drift the jets at 15-20 knots. Been that way forever. 

[DmitriKozlowsky]

I think , in DCS, friction works correctly for rubber wheels, becouse pedaling into wind while rolling can only be done safely when light on wheels.  With collective down, the helicopter won't pivot due to pedal , as easily, and should not be done.

[TrevorMcNeill]

On 6/23/2022 at 5:09 PM, DmitriKozlowsky said:

Helicopters take off and land into the wind. Unless you are so heavy that you need a rolling takeoff. A helicopter may be directed by ATC onto runway, but there is no requirement or need to take off linearly along runway as fixed wing. Even if you need a rolling takeoff you can diagonal across runway in a helicopter. Fly helicopter as helicopter, not as fixed wing.

I only used Runway as a reference/example, what I'm saying is that you need to keep the nose into the direction of travel up to 50ft. I'm saying this as someone in army flight school being taught by IPs with thousands of hours. Yes, its a game but it's still good practice. To use skidded aircraft as a reference if you're taking off amd immediately turn into then catch a rock with the skid at an angle you're much more likely to have dynamic rollovers where as if it caught the skit dead on(unless you catch the very front of the skid)

Edited June 25, 2022 by TrevorMcNeill

[Raptor9]

3 minutes ago, TrevorMcNeill said:

what I'm saying is that you need to keep the nose into the direction of travel up to 50ft. I'm saying this as someone in army flight school being taught by IPs with thousands of hours.

50 feet is just a cookie cutter standard for task/conditions. There isn't any reason to keep the nose pointed in the direction of travel at 50 feet any more than 40 or 60.

But it is situational, so if you are flying low enough or close enough to obstacles or hazards, you do need to be cognizant of where components of your aircraft are potentially going to be impacting if you aren't paying attention.

[TrevorMcNeill]

6 hours ago, DmitriKozlowsky said:

You can roll quite a good distance . Not that you need much in a helicopter. For GW get above ETL, and as soon as helicopter is light on wheels pedal nose into wind, and correct for dynamic roll with cyclic deflection. If you need long roll, or can't hover in ground effect, you are too heavy for safe flight, and certainly you can't fight. 

I believe you may not understand what dynamic rollovers is. Dynamic rollover is a typically ground based incident as dynamic rollovers require three things: a pivot point, a rolling motion, and to exceed the critical angle(not a specific angle its just simply the angle where safe recovery is no longer possible) for an apache a good example would be if you attempt to take off and start drifting left, the wheel catches the ground(now the pivot point) then because the aircraft is now pivoting on that wheel you have the rolling motion, if you continue to try and climb you will most likely expedite that rolling motion and exceed the critical angle then bobs your uncle and you crashed. Proper correction for this specific scenario is to decrease collective(literally one instructor said just to slam it through the floor) as early into the roll as you possibly can. Also of youre at ETL or above and catch something causing a dynamic roll you aren't saving it unless you have god as a copilot lmao. Dynamic rollovers typically happen very fast as it is at very slow speeds <10kts (literally a random number) so 16-24kts....good luck

15 minutes ago, Raptor9 said:

50 feet is just a cookie cutter standard for task/conditions. There isn't any reason to keep the nose pointed in the direction of travel at 50 feet any more than 40 or 60.

But it is situational, so if you are flying low enough or close enough to obstacles or hazards, you do need to be cognizant of where components of your aircraft are potentially going to be impacting if you aren't paying attention.

Yeah I get that and I'm not saying you have to fly straight until 50ft just keep the nose front thats all. Again I'm mainly talking for take offs but even during masking/unmasking if you're relocating left or right more than 100ft or so its just safer to turn, move then turn back to target. No need to slide right for 100yrds. So yeah situation dependant but most situations it's just a good idea to keep the nose front skids and wheels don't work great from the side haha

Edited June 25, 2022 by TrevorMcNeill

[DmitriKozlowsky]

I beg to differ. I know exactly what helicopter dynamic rollover is. 

[TrevorMcNeill]

1 minute ago, DmitriKozlowsky said:

I beg to differ. I know exactly what helicopter dynamic rollover is. 

Okay well maybe its how you worded it but if you, at that speed, you turn your nose to the wind with your wheels now running angled inches above the ground you're asking for an unrecoverable rollover because chances are you catch something at that speed you're gonna hit the ground faster than you can react. Again It's a game and you'd prob just bounce off of it but if we are bringing realistic terminology into this equation then you might as well fly or at least discuss flight as if they are a real concern

[Scaley]

6 hours ago, DmitriKozlowsky said:

I think , in DCS, friction works correctly for rubber wheels, becouse pedaling into wind while rolling can only be done safely when light on wheels.  With collective down, the helicopter won't pivot due to pedal , as easily, and should not be done.

Friction exists for sure, but if you go for a fast taxi in any of the jets your discover that the friction is WAY too low. They all drift laterally in conditions that the manuals suggest would cause rollover. Similar odd things happen lie the fact you can pedal turn the Apache at relatively low torque settings with the tail wheel locked, and taxi forwards at 1-2 knots with the tail wheel pointing sideways and the friction will be so low it won't caster to the centre. There are a lot of threads in the forums about this over the years, some with numerical test data, that support the idea that DCS just has too little friction between rubber tyres and the ground. 

Edited June 25, 2022 by Scaley