Flightmodel issues

[JG78_horΛz]

I'm not entirely sure if this is a bug, but I suspect it is based on my experiences with other helicopters in DCS.

1. When flying forward at relatively high speed, if you pull the joystick back just a little too much, the helicopter's nose will uncontrollably pitch up to such an extent that it requires a lot of effort to regain control. Besides that, performing such a maneuver can bring the helicopter to a halt so quickly that it seems very unrealistic to me. To test this, accelerate to full speed, pull the nose up sharply, and a cobra maneuver occurs, causing the aircraft to hover without changing altitude.

2. I often notice that while hovering, even with maximum rudder input, my helicopter is unable to maintain the desired direction. Only when transitioning back to forward flight does it become possible to maintain the direction again.

[admiki]

6 hours ago, JG78_horΛz said:

I'm not entirely sure if this is a bug, but I suspect it is based on my experiences with other helicopters in DCS.

1. When flying forward at relatively high speed, if you pull the joystick back just a little too much, the helicopter's nose will uncontrollably pitch up to such an extent that it requires a lot of effort to regain control. Besides that, performing such a maneuver can bring the helicopter to a halt so quickly that it seems very unrealistic to me. To test this, accelerate to full speed, pull the nose up sharply, and a cobra maneuver occurs, causing the aircraft to hover without changing altitude.

2. I often notice that while hovering, even with maximum rudder input, my helicopter is unable to maintain the desired direction. Only when transitioning back to forward flight does it become possible to maintain the direction again.

Neither is a bug.

#1 You are basically stalling it. @AeriaGloria is better at explaining it.

#2 you are running out of tail rotor power. It is not unknown. You are too heavy for conditions. In real life early Bell 206 helicopters were known to run out of pedal.

[T.Power]

Page 7 tells you all you need to know about Rotors, they are dangerous to fly, human error is the single biggest cause of rotor accidents, VRS is a real issue and there was at least one attempt to ban rotors completely at least in the US, circa 1950 IIRC.  I still run out of pedal flying the Hind for around 10 months, these things want to kill you.

https://www.h-a-c.ca/IHSS_Helicopter_Safety_History_05.pdf

You should try desaturating your joy axis if small movements cause you to stall so easily.

Edited Saturday at 08:40 PM by T.Power

[AeriaGloria]

13 hours ago, JG78_horΛz said:

I'm not entirely sure if this is a bug, but I suspect it is based on my experiences with other helicopters in DCS.

1. When flying forward at relatively high speed, if you pull the joystick back just a little too much, the helicopter's nose will uncontrollably pitch up to such an extent that it requires a lot of effort to regain control. Besides that, performing such a maneuver can bring the helicopter to a halt so quickly that it seems very unrealistic to me. To test this, accelerate to full speed, pull the nose up sharply, and a cobra maneuver occurs, causing the aircraft to hover without changing altitude.

2. I often notice that while hovering, even with maximum rudder input, my helicopter is unable to maintain the desired direction. Only when transitioning back to forward flight does it become possible to maintain the direction again.

1. This is a behavior known by the Russians as “Podkhvaht” or “pick up.” It is a blend of two things 

A. Mushing: this is what happens when a helicopter at high speed experiences high enough G load that AOA becomes positive, and up flow of air through the rotor causes it to stall, causing RBS like symptoms as you lose control and thrust 

B. The wing is installed at 19 degree angle. Not coincidentally, the wing also stalls at 19-20 degrees. This means almost any positive AOA will stall the wing. The wing is also quite a distance behind the rotor mast and center of gravity (CG), this means that the lift it creates (up to 25% in cruise) also causes a pitch down moment. It also means that any payload on the wing moves CG back, which increases AOA and thus wing lift. This is one reason that loading weight on the pylons has so little effect on it in cruise.

So when increase G load between 1.4-1.8 G, at some point the Angle of Attack will transition from above your nose to below, your rotor will get up flow and begins to stall and your wing is also stalling. 

The first part of the rotor to stall is the right side, causing a pitch up. The wing being behind the CG/rotor, is causing a lot of pitch down force with its almost 3,000 kg of lift. Now that it’s stalling, suddenly the force pitching the nose down goes away and makes the pitch up worse. 
 

So it’s a cascading intermeshing of issues, that all happen to be caused at around the same time. 
 

There are three ways to recover or prevent this happening! 
 

A. this always happens at a certain G-load, I will post the G chart, a good rule of thumb at medium weights and altitudes is don’t exceed 1.6-1.8 G. If in a level turn, this is around 50-55 degree bank 

B. Decrease collective pitch 1-3 degrees. This will un stall the rotor. You might be surprised how fast it can snap back after just 1-3 degrees less collective. 
 

C. Full stick forward! 
 

Also. If your are nearing the ground, decrease roll angle during recovery. The less your bank angle, the less altitude you lose while this happens 

Also. Manual recommends to increase G to desired load in a turn over the course of 2-3 seconds. This makes a big difference for me 

There is a real G chart for this, but has a huge margin of safety for speed. I usually ignore the speed restrictions, it will always happen at the same G, but the faster you are the more violent it will be. You can get a really good feel for this by doing 50-55 degree angle bank turns. In my experience, weight, altitude, and collective decide what your max G will be

There is dot in the G meter at 1.5 G, it is good reference for minimum G you can sustain at all altitudes below about 2,000m. I made my own color coded picture with yellow/red as danger zones 

Also: the effect of the entire podkhvaht/pick up was made smoother in a patch recently 

 

2. Your second issue, tail authority 

My first suggestion if you you are not overweight or at too high altitude, is watch your Yaw AP. 
 

Your AP can add/subtract anywhere from 18-118% authority, and trim you without your consent. Check if you have an option “Pedal auto move” on. You want to have it off. Turning it off means that if Yaw AP runs out of its 18% authority, it will trim your pedals to use as much authority as it needs. Having it on means that pedals will trim you anytime heading moves more then 7.5 degrees from the heading it’s trying to hold 

I tell most new flyers to keep Yaw AP off. And to only play with it once you are ready to play with the microswitch and all the microswitch options the change the Yaw AP from heading hold to dampening. If you are interested, let me know. I have also written large guides for weapons and autopilot and translated an aerodynamic manual for it. 

Edited Sunday at 12:03 AM by AeriaGloria

[admiki]

I am so happy we have AG, so I don't have to type all this c*ap.

[KoN]

I've encountered this violent pitch up at high speeds avoiding trees and ground fire . Thank you for the information very helpful.