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Flying Sideways


eagle5

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A couple of questions;

 

1. Can you recover from Settling With Power by moving sideways instead of forward?

 

2. Can you experience the benefits of ETL from a crosswind?

 

a. Increased hover performance with a 20kt crosswind?

 

b. On approach at 5kts, will a 20kts crosswind make it easier to land while hot and heavy?

 

c. Confined area takeoff, cannot go forward. Will moving sideways get you through ETL so you can climb out?

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1 and 2 yes.

 

Cross winds are trickier for performance gains because of the possible additional tail rotor thrust required. A left crosswind with a helicopter with large vertical stabilizer like the 135 would help reduce tail rotor thrust requirements while also experiencing etl in the rotor disk.

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Yes yes yes

The difficulty is in maintaining directional control with the pedals in some circumstances depending on the make model...the crosswind may cause other difficulties due to impact pressures on the stabilizers and potential of loss of tail rotor effectiveness or vortex ring state of the tail rotor.

You should have your instructor demo a backwards take-off

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c. Confined area takeoff, cannot go forward. Will moving sideways get you through ETL so you can climb out?

 

This was puzzles me. Why wouldn't you just turn the nose to your side, then proceed moving forward?

 

I can think of no situation where you can pick up and only go sideways ... you would simply turn the nose in the direction you want to fly.

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In short, your rotor disk does not have a front and doesn't care which way the winds enter it. But the fuselage will have considerably more drag from other than the front.

 

Moving sideways or in a crosswind below ETL you will need more cyclic to overcome that drag bending your rotor in the direction your moving. Instead of using all your thrust vertically to maintain altitude you will be using more horizontally, so to maintain altitude you will initially need more torque (this is true forward also but not as pronounced). Eventually you'll hit ETL but the drag factor will require more power than if you were facing forward. TR thrust plays a factor as well as winds can try to turn you as they hit the stabilizers and tailboom. Depending on strength and direction winds can create up flows, downflows, and vortex ring states in the TR blades changing power needed to maintain heading.

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This was puzzles me. Why wouldn't you just turn the nose to your side, then proceed moving forward?

 

I can think of no situation where you can pick up and only go sideways ... you would simply turn the nose in the direction you want to fly.

 

 

I was thinking the same thing. Perhaps the poster just didnt think through the question?

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This was puzzles me. Why wouldn't you just turn the nose to your side, then proceed moving forward?

 

I can think of no situation where you can pick up and only go sideways ... you would simply turn the nose in the direction you want to fly.

 

There could be other reasons why sideways flight is required. For example, filming or shooting out the passenger side door.

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I was thinking the same thing. Perhaps the poster just didnt think through the question?

 

We were taking off inside a very tight cauldron like confined area. We had the power to just barely get out, but instructor said that if we hadn't, we could have moved side to side (first to the right, then to the left, then back again) to generate the added lift from ETL. Turning the nose would not have helped, unless we wanted to go forwards and backwards again and again.

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We were taking off inside a very tight cauldron like confined area. We had the power to just barely get out, but instructor said that if we hadn't, we could have moved side to side (first to the right, then to the left, then back again) to generate the added lift from ETL. Turning the nose would not have helped, unless we wanted to go forwards and backwards again and again.

 

Here we go (not the rescue dog that brings you beer), what happens to the total lift vector when the rotor disc is tilted? How much airspeed does it take to have ETL? When you reverse direction, do you not slow down and give up the lift(from your theory)generated and then have to generate it again? How fast can you go sideways in that limited space as described? Only using the book definition, can you get 16 to 24 mph to attain ETL?

 

 

Why do flight instructors make this stuff up? Scary. Very Scary!

 

Maybe use some performance recognition and planning and avoid this situation if possible or own the flight as PIC and change the parameters.

 

Mike

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We were taking off inside a very tight cauldron like confined area. We had the power to just barely get out, but instructor said that if we hadn't, we could have moved side to side (first to the right, then to the left, then back again) to generate the added lift from ETL. Turning the nose would not have helped, unless we wanted to go forwards and backwards again and again.

 

This makes no sense. A "black hat" spinning takeoff (to the right in counter clockwise turning helos) can give you extra power to the MR, but this is a very advanced technique and I don't recommend it unless you're getting shot at. Even fling a tight circle to get a little bit of speed could work if there's enough room to do so safely, but still....

 

Flying sideways back and forth.... I don't see how that would get you anywhere.

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In my opinion, 2 b and c should never happen. ADM. PP level instruction.

 

You need to get out a little more or not limit your imagination so much. I can say for certain that I've been in 2 b and c scenarios with various contracts that I've been on and they were perfectly acceptable operations.

 

Performance charts have their limits and can't cover all operating scenarios. I've been on helidecks with limited entry and exit routes with less than ideal winds and certainly not azimuths that were in the RFM. In those instances you work with what you are dealt.

 

I'm not trying to be harsh, I'm just saying that the OP has a question with a scenario that might not be readily imagined, but could certainly exist with a little more description or imagination.

 

I will say that I can't envision how zig zagging will maintain ETL or a reasonable lift vector. I have done low altitude circles with no prevailing winds in a confined area to get ETL before takeoff, but it was sizeable and allowed for that.

 

I've also seen the clockwise and counterclockwise cyclic movements that will add or reduce hover height. I really don't understand how that works with my limited aerodynamic understandings.

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Hmmmm.... Ive done a number of very tight confined areas at some decent altitudes. 5000+, been to a couple of pretty good mountain courses, all done in turbines and was taught some pretty intense mountain techniques by our unit instructor who had over 30,000hrs and about 15yrs flying in 10,000+ mountains and Ive never heard this technique. Now I have been taught to spiral up (flying foward not sideways) in a tight confined area but never sideways left to right. Because flying say, to the right, then stopping and going back to the left, you are going to find yourself, even if for a brief moment, in an out of ground effect hover, in an area where you did not have the power to just climb vertical. At a decent altitude or on a high DA day, your going to run out of left pedal and start your uncontrollable death turn to the right in your "cauldron" as you put it. If you climbed vertical, and didnt have the power you would just decend sgtraight back down to a known spot. If you have the power to do this left and right thing, you should have the power to climb vertical. If you have the power and space to get thruogh ETL flying sideways, Im just not envisioning a scenario where you couldnt turn in that direction and just fly straight ahead.

 

Just out of curiosity, what were you flying and what is your instructors experience in the mountains? I dont mean hills, mountains. Ive done all my mountain stuff in a 500E and never heard this "technique". Im still learning, but Ill run it past the guys here. Heck.....Ill go out today and try it and see if I can even get through ETL sideways! :D

 

Thats my only thing. You cant teach every scenario, but Ive never been taught to climb out sideways. Youll be using a lot of power to keep any helicoopter with a decent sized vertical fin flying against the wind. Now, Ive come off of a pinnacle sideways to get around a tree and keep the nose into the 20kt wind that was present until I was clear and could fly away. Obvioulsy in the real world you need to take all your ingedients and make your own cake, but I dont know that the instructors reasoning about the left and right is very legit. I just see it using a lot of power

Edited by Flying Pig
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The sideways thing I've done if I have wind on my nose, but an obstruction in front of me. It can be like a lateral towering take-off, so you maximize weathervaning, headwind component, but not moving forward, if that makes sense.

Edited by C of G
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Never heard of the side to side pendulum take-off, but Shawn Coyle describes a forward and back takeoff in a similar fashion- from his Torque Talk article "Up, Up, and Away":

 

"***The Pendulum Method:*** I call this technique the pendulum method because I don’t know of any other name for it, and it actually describes it perfectly at any rate. It requires a large enough area to get some flying speed, but initially not enough to clear the obstacles. It also requires good judgment, which is always in short supply.

 

Basically, you start by charging the barrier, then slow down and not just stop, but allow yourself to move backwards. The height gained in the first part of charging the barrier is used to gain a bit more speed moving backwards than you had moving forward, and that speed is used to gain height as you accelerate rearward. The acceleration rearward is continued to an acceleration forward, which in turn gains even more height, and so on. Eventually, the height will clear the trees as you move forward, or the speed will be sufficient to let you zoom

to clear the trees — or perhaps both will happen.

 

The problem with this method is that it takes a good deal of judgment and skill, and since every confined area will be different, a good deal of adaptability as well. If things go wrong at an inopportune moment, the result may not be pleasant."

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Man.... Ive read his books to and he is definitley an expert. I just see baaaaaad juju. Charging a barrier and then running out of power pedal and options at the point your are transitioning to reward flight.......... Id have to have someone show me that one! because at some point, even if briefly, your going to end up at 0 airspeed while you transition backwards. I guess Id have to study it more. Obviously not for every scenario. I just have to think transitioning from forward to rearward flight, youd have the power to just go vertical. One day Ill try it in a low altitiude, wide margin area and just see what happens.

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"Just out of curiosity, what were you flying and what is your instructors experience in the mountains? I dont mean hills, mountains. Ive done all my mountain stuff in a 500E and never heard this "technique". Im still learning, but Ill run it past the guys here. Heck.....Ill go out today and try it and see if I can even get through ETL sideways! :D"

 

He was a cfii who'd just made it to 1000hrs, I don't know if he had any mountain experience, and we were pretty close to sea level at the time, training in an R22.

 

Never tried the technique myself, but what I'm getting here is that is bogus, so I won't pass it on.

Edited by eagle5
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To the original questions- translational is translational, it's there even before ETL, no matter the azimuth relative to the aircraft fuselage. The issue becomes how much TR power is used to hold that azimuth?

 

As to power limited out of a confined area- What you don't want to do is have all the power available applied, out of ground effect and aircraft moving towards the obstacle but not clearing it... That's an even more dangerous position than operating in the dead man's curve. That's the issues I have with "charging the barrier" and the "pendulum method", which are numbers 2 and 3 of "Methods to potentially avoid" listed in the attached Shawn Coyle article. It's a lot safer to get to the top of a vertical, decide you can't clear, abort and land.

The article describes an interesting variation, "Back it up", which I've never tried. Issues would be the down wind hovering climb while backing.

Edited by Wally
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If you can fly sideways then move a little to that side and then kick your tail rotor into the space you just created with a torque turn. Wallah! Problem solved.

 

Now my nose is facing a wall and I either have to go straight up, or fly backwards!

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Now my nose is facing a wall and I either have to go straight up, or fly backwards!

 

My question would be...... How the heck did you get there to begin with???? Did someone build an apartment complex around your helicopter while you were getting lunch?

Edited by Flying Pig
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