Cannot do autorotation

Whenever I loose an engine, Gazelle just falls right out of the sky like a brick. None of the rules and immediate actions to do for autorotation seem to work.

Immediate action to enter autorotation

Collective down

Cyclic fwd to maintain rotor RPM

Turn into wind

Maintain cyclic to maintain rotor RPM.

Flare a little to arrest vv prior to settle. Maintain VV of no more -1m/s for touch down, no more then -5 m/s on autorot.

But what happens, upon loss of engine, is that helicopter immidiately falls, and nothing I do arrests the rate of descent.

OK.

I have no takeaway from this video. As Gazelle autorot segment did not have control diagram up, I can't see what he is doing with controls.

Autorots have three base actions, as I understand rotary wing flight.

-Collective down

-Cyclic forward to maintain rotor RPM

-Cyclic flare just at right time to arrest sink rate.

But in my case, the aircraft just falls down straight or almost straight, and no amount of cyclic FWD seems to cause it to pick up speed prior to flare. It just falls and explodes.

That can't be right. Diving a helicopter like Stuka, then pulling out. That can't be right. I cant see any helo manufacturer doing that. Or any service accepting a helicopter with a single engine, that cannot auto rotate safely. The fact that DCS version drops like a brick immediately after power loss, as if the simulated freewheeling gearbox does not disconnect automatically from main rotor, makes me think that this is a issue with base simulation.

Whenever I loose an engine, Gazelle just falls right out of the sky like a brick. None of the rules and immediate actions to do for autorotation seem to work.

 

Immediate action to enter autorotation

 

Collective down

Cyclic fwd to maintain rotor RPM

Turn into wind

Maintain cyclic to maintain rotor RPM.

Flare a little to arrest vv prior to settle. Maintain VV of no more -1m/s for touch down, no more then -5 m/s on autorot.

 

But what happens, upon loss of engine, is that helicopter immidiately falls, and nothing I do arrests the rate of descent.

Collective down

Cyclic BACK, if you push forward with no engine you'll lose rotor rpm

I think you need to maintain around 130kmh.

The secret at the bottom end is to flare at 50 feet with no collective, then you pull in collective to cushion it.

An auto in the gazelle will be a running landing.

hello:)

Remember that gazelle is a small helicopter with a small rotor with less inertie than other helos.Thus she loose more fast her energie.Take a look at this video,and check out speed and sink-rate.

If you need more help PM please

Cyclic BACK cannot be right, it will increase AOA of rotor blades, increasing drag and slowing them. Cyclic BACK is only to flare to arrest descent rate right before touchdown.

I don't get any of this behavior as seen in YT videos here. I loose engine, I collective down, cyclic slightly up to maintain RPM. But it does not matter, it just falls straight down and accelerates there is no arrest of descent rate by rotor. Somebody is lying to me.

TL;DR:

• Descend at 120-140 km/h, 430 RPM

• at 20m AGL flair and increase collective

• At 7m (IGE) increase the collective further to reduce descent rate / forward speed

• touchdown for a skid landing at 15-20 km/h

Practice lots i.e. I'm still breaking the Fenestron/tail but I'll get better eventually (or go back to doing autos in the Huey :lol: ).

Detail:

Here are my WIP auto-rotation notes.

Gazelle Auto-rotation practice

 

• Entry - 150-200 km/h @ 500 m AGL

 

• Training - Disengage SAS

• Fuel Control - Closed (PgDn)

 

• Full low collective

• DO NOT pitch FORWARD unless less than 100 km/h (55kts)

• Manage Rotor Speed 430 RPM, increase collective as req'ed

• Turn into wind if necessary

• Approach speed 120-140 km/h (65-75 kts)

• At 20m (65ft) moderate flair

• At 7m slight increase in collective

• Maintain Flair Attitude (pitch up) until 1-2m AGL

• At 1-2m Increase collective to maintain height/slow down

• At 15-20 km/h level out and contact the ground

 

DO NOT ATTEMPT TOUCHDOWN WITH ZERO FORWARD SPEED

It doesn't matter if I am going 50 kph, 100, or 200 kph, if I loose engine, it falls straight down. Collective down, cyclic up/down, doesn't matter. Just falls straight down,.

It doesn't matter if I am going 50 kph, 100, or 200 kph, if I loose engine, it falls straight down. Collective down, cyclic up/down, doesn't matter. Just falls straight down,.

I don't know what to say, here's an example of a (poor) auto-rotation approach profile ...

... I think I've half a tank of fuel and no weapons/ammo.

Note: It looks like I messed up the flair in this attempt as it's high i.e. @ 50m

In book "Chickenhawk", a memoir of UH-1H pilot in Vietnam, authpor describes autorotation properties of UH-1. There is an example of how instructor shows students autorotation properties of UH-1H. With instructor at controls, and student in cabin, with UH-1 on ground with rotor at power RPM ready to take off. Instructor demonstrates high inertial rotor of Huey. He cuts off throttle, with rotor freespinning, he adds collective, and lifts the helicopter, then lowers the collective settling the helo back down. All without power, with rotor entirely on inertia and autorot. Now, our DCS:UH-1H cannot do that. Our Gazelle is a brick without power. I tend to beleive that rotary physics as they impact autorotations are not as good as we thought, they are.

I can see by your curve that you Gazelle is a brick without power. Just like mine. Grim reapers example, they have to dive bomb to the deck in no power Gazelle, then pull cyclic back to flare, and they crash. Just like me. THe only difference is amount of damage.

I can see by your curve that you Gazelle is a brick without power. Just like mine.

Then it's likely correct as the Gazelle's rotor doesn't have as much inertia as the Huey and I'm using the autorotation procedure as described in the 1995 SA-341G POH.

From 500m AGL I have approx. 30 seconds of approach @ 120-140 km/h / 430 RPM and ~7 seconds to do everything else.

Here's the real thing ...

... note the time/height at which the pilot flairs and when he lands, it's ~9 seconds, so pretty close to the time in DCS, perhaps it'll change with the new FM.

Note the flare at 1:40. When I do that, VV is not arrested or even retarded in a significant way. Helo falls, crashes and explodes in DCS.

Cyclic BACK cannot be right, it will increase AOA of rotor blades, increasing drag and slowing them. Cyclic BACK is only to flare to arrest descent rate right before touchdown.

Negative;

A quick google search brought me this http://www.copters.com/pilot/autorotation.html

"While the collective is being lowered, the nose of the helicopter has a tendancy to pitch down. The pilot needs to use aft cyclic to prevent this. Allowing the nose to pitch down creates two problems: it tends to reduce RPM because it decreases the amount of airflow through the rotor disk, and it tends to increase airspeed, usually far above the range you want to use while autorotating."

I wonder if you doing cyclic forward at the start of the auto is losing rotor RPM so you don't have enough rotor RPM stored to trade for lift near the ground.

I haven't flown a gazelle, but I do fly a 3 bladed + fenestron Cabri G2.

Then it's likely correct as the Gazelle's rotor doesn't have as much inertia as the Huey and I'm using the autorotation procedure as described in the 1995 SA-341G POH.

 

From 500m AGL I have approx. 30 seconds of approach @ 120-140 km/h / 430 RPM and ~7 seconds to do everything else.

 

Here's the real thing ...

 

 

 

... note the time/height at which the pilot flairs and when he lands, it's ~9 seconds, so pretty close to the time in DCS, perhaps it'll change with the new FM.

This represents exactly what I posted to do on the previous page. Flare at fifty feet then use collective to cushion, and plan on a running landing.

And yes, you have to go cyclic back. Either trim it or hold it there. Otherwise you won't be able to maintain RPM's which is a necessary component of any autorotation.

Come on :)

i'm ready to share a session with you and see what happens.

You as a pilot and me as a passenger.

Choose your day and hour,i will be there.

i'm sure that you are doing something wrong with cyclic and collective coordination.

Or curves are bad and your collective stays not completly down.

Result is that energie goes away.

Or you flare after collective action,a stuff like that.Or you pull too soon on collective.Or you don't make the flare at the correct height.

Pm me and we could organise a meeting.

Cyclic BACK cannot be right, it will increase AOA of rotor blades, increasing drag and slowing them. Cyclic BACK is only to flare to arrest descent rate right before touchdown.

Cyclic goes back to increase the airflow threw the blades. In an autorotation the air going up threw the rotor disk keeps them spinning and generating enough lift to keep you from dropping like a brick. Adjusting the collective changes the size of three aerodynamic regions of the blade: the driven region, the driving region and the stall region. The overall lift vector of the driven region is behind the vertical so that lift also adds drag to the rotor system. The driving region's lift vector is forward of the vertical with respect to the rotor blades. That is where the energy is coming from to keep your blades spinning. The stall region contributes nothing but drag where as the driven and driving regions are producing the lift that keeps you in the air. You control the size of these regions with the collective and control the airflow through rotor disk with the cyclic. This gives you two ways to manage rotor rpm. Lower collective and aft cyclic both increase rpm while raising collective and forward cyclic decrease it. You can also look at it as trading airspeed for rotor rpm. My 206 has a little blue line at 100 knots to indicate that above that speed you will be in such a nose low attitude as to not have enough airflow to maintain rpm. It varies for every helicopter but generally speaking around 52-55 knots is going to give you your lowest rate of decent and around 90 knots will give you your longest glide. Between 60 and 70 knots is usually a good compromise because you'll have enough energy in your airspeed to convert to rpm in your flare to landing.

To be fair the Gazelle does seem to lose an excessive amount of rpm compared to a real world helicopter like an astar. But an auto in the gazelle is definitely still doable. Have to talk to the mechanics and have em make a few turns down on the pitch links.