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High DA Landings


r22butters
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Not too long ago I was making an off-airport approach up in the mountains.

 

I was doing my usual, slow, walk-in type approach (just on top of ETL), when the Cfi told me to "keep my speed up, because if this were the middle of Summer, you wouldn't be able to come in that slow". :huh:

 

Later, upon reflection, I thought; the LZ was OGE, so if I wouldn't have the power to bring it in slowly (due to the hot weather/high DA), then surely I wouldn't have the power to hover OGE, and therefore should not attempt the landing anyway? :blink:

 

I like to bring it in slowly for off-airport LZ's because I feel more in control (with less worries for Settling with Power, or LTE), plus I also think its a good way to make sure I have enough power to land OGE.

 

I have, although, over the years, had many instructors tell me to "keep up my speed" on approach, for the same power reasons.

 

So I guess my question is; How do you High DA Guys do it, and why?

B)

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I hate fast approaches, if you drew a power required curve for the duration of the landing, a higher speed approach would have lower power required until just before touchdown.

 

Once you need to reduce the forward speed and rate of descent the power required will spike to a value higher then what would be necessary had you been going slower.

 

In addition if you choose a steep approach angle, an increase in forward speed equates to a much larger rate of descent required to maintain angle.

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I like slow if I have lots of power... if it IS high DA and I'm going to be near the hover ceiling then I would agree with those instructors that told you to keep your speed up because as you slow way down and start to settle you're going to find yourself practically touching the skids before you can get up on the power curve if you let it dip at all. So should you not have landed there? Depends on the particular LZ and how you're going to come out of it....

 

Even though you probabally have enough power to arrest the decent if you're above ETL... you do gain even greater efficiency if you're a little faster than riding the etl bumps and that just helps you stay up on your rpm and on the high side of the power curve in these piston helicopters.

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Fast slow, are all relative. To my mind, a defined decel after the approach is started is the definition that means I planned poorly or I'm being hasty.

Unless somebody's shooting at you, the best approach is the one that avoids surprises while maximizing options. I want the power in early while there's time to change my mind. I don't hang on the engine any longer than I have to, but there are times when I have it all in and I'm controlling the approach, angle, etc. with other flight controls, not the power, so that a low decel isn't required.

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Wally decribed it the exact same way I do it. A nice and easy approach that is smooth and controled. Power is in sooner rather than later in most cases and ROD is 200' or less. I tend to make the approach angle flatter unless there is plenty of wind and turbulence. In which case I would want a steep approach to avoid turbulence and down drafts.

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I'm with the Wally and JD. Whether it was the GOM or the HEMS world, slow is best. Matter of fact, once established to my point in space landing(most of the places we go have wires and poles completely around the pads) I don't touch the collective except to set her down. 200' or less is right on. Anything else and you're asking for trouble with no way out (unless you're at an airport). My pad at Hobbs is 100' or less once I hit my point in space.

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