Approach Technique and The Vortex Ring State

[eagle5]

I'm fond of technique #1, but A LOT of CFIs I've flown with say I'm playing with VRS, and prefer technique #2.

 

Thoughts?

Edited May 13, 2013 by eagle5

[Eric Hunt]

How long you going to hold onto 40kt?

 

You are on the right-hand side of the drag curve, with 600fpm ROD. This means you have the lever on the floor and don't know if you will have enough power to stop the descent at the end.

 

Positive forward movement, controlled rate of descent, airspeed higher than groundspeed, with some power left to pull - get below 30 kt and have that power coming in.

 

I don't like either of your "techniques", 1 is a bit slow, 2 is too fast. But what would I know? I only have 14,000 hrs.

[Hand_Grenade_Pilot]

I'm fond of technique #1, but A LOT of CFIs I've flown with say I'm playing with VRS, and prefer technique #2.

 

Thoughts?

 

Maybe I'm misreading this, but "technique #2" sounds like they are dumping the collective while staying above ETL and then 'chasing' the steep approach angle.

 

If this is in fact what they are doing, I would highly discourage anyone from attempting to land this way. You can't terminate an approach to a confined area flying forward at 40kts, without flaring and experience a huge increase in power demand (you'll need to pull a lot of collective). This is what I would consider 'hot-dogging' and would not end well if you are power-limited. It also provides little means for a go-around.

 

The proper way to perform a steep approach is to come in SLOW. ROD should be below 300'/min, even lower for very steep to towering descents. Forward speed (rate of closure) is determined by how steep the approach angle is.

 

The steeper the approach, the slower the rate of closure & ROD.

[eagle5]

I realize that at below 1000hrs I'm not that experienced at this, and I'm doing it in an R44, so I don't have many other aircraft to compare to, but I feel more comfortable with technique #1 (coming in slow and controlled).

 

However on two seperate occasions with two seperate CFIs (one of whom was also a high time old guy and DPE) when they took the controls and showed me how they prefer it to be done, I looked over and 40kts/600fpm was what I saw,...and we were getting pretty damn close (as my butt-cheaks began to clentch)! Both of these CFIs (as well as a few others on seperate occasions) have remarked while I was coming in nice and slow, that we're getting close to VRS (one even reached over and pushed the cyclic forward as he said it)!

 

Coming in "hot" like these guys did, I really hope they always have the power to stop that high ROD! My prefered technique may be too slow for some, but at least I'll know if I have the power to hover high enough to change to something else if I don't!

[SBuzzkill]

Why do it below ETL?

[Hand_Grenade_Pilot]

I realize that at below 1000hrs I'm not that experienced at this, and I'm doing it in an R44, so I don't have many other aircraft to compare to, but I feel more comfortable with technique #1 (coming in slow and controlled).

 

However on two seperate occasions with two seperate CFIs (one of whom was also a high time old guy and DPE) when they took the controls and showed me how they prefer it to be done, I looked over and 40kts/600fpm was what I saw,...and we were getting pretty damn close (as my butt-cheaks began to clentch)! Both of these CFIs (as well as a few others on seperate occasions) have remarked while I was coming in nice and slow, that we're getting close to VRS (one even reached over and pushed the cyclic forward as he said it)!

 

Coming in "hot" like these guys did, I really hope they always have the power to stop that high ROD! My prefered technique may be too slow for some, but at least I'll know if I have the power to hover high enough to change to something else if I don't!

 

I see no logic in coming in "hot". This isn't Vietnam, and that DPE isn't getting shot at on a check-ride. The only other argument would be that it "minimizes your time in the H/V curve". Which is horse s***. Why? Because pilot error (not engine failures) is the leading cause of accidents. And coming in 'hot' to a confined area has pilot error written all over it.

 

As long as you keep a very low ROD and maintain a positive headwind component, you will not get Vortex Ring State or Settling w/ Power (as long as you are not trying to land under DA/Gross Weight conditions that do not allow for an IGE hover)

 

I encourage you to continue flying the right way and take it in "nice and slow".

[aeroscout]

Before I would attempt to answer your question I would want to get some background information. Are these instructors you are flying with also flying with you during your settling with power maneuvers ? A lot of their reactions to confined area techniques could be explained by their attitudes and reactions when they are teaching or evaluating your settling with power training.

[pilot#476398]

Slower is better I always say, or was that my girlfriend?

[Spike]

OTJ, my ROD and airspeed is dependent on the situation at hand and not with the semantics of theory……..

 

Fly the machine based on the situation. If you need to rationalize why you are, or aren’t, doing something, then consider yourself behind the curve…..

Edited May 14, 2013 by Spike

[pilot#476398]

OTJ, my ROD and airspeed is dependent on the situation at hand and not with the semantics of theory……..

 

Fly the machine based on the situation. If you need to rationalize why you are, or aren’t, doing something, then consider yourself behind the curve…..

 

 

Ditto

Edited May 14, 2013 by pilot#476398

[apiaguy]

I think maybe the reason people don't like your #1 approach is you slow too early...

I prefer to keep the speed up until we are closing on the final phase of the approach. I have flown with a number of pilots who do as you suggested and here we are 200 yards from the spot slowing below 20 kts and it feels uncomfortable to me. I feel like they are about to get themselves on the underside of the power curve and if we were pushing the limits of HOGE I would be concerned about VRS.

[Wally]

10 knots and 176 fpm is a 10 degree angle by my calculation.

 

But:

I've never seen an airspeed indicator that would accurately indicate at 10 knots.

If you had such gear, it would require precise and accurate knowledge of surface wind speed to make the 10 deg angle good, and then only for the brief interval of the smooth and constant deceleration of a good approach.

I want my eyes outside at the point where that combination would be, the low recon continues until you have landed, the lower you are the more important it is to have eyes out. The greatest hazards are an unsuitable landing area, main rotor striking something you never saw or lost track of, sticking your tail rotor into something with a flare, and insufficient power at termination.

VRS considerations are in there somewhere, you need to have that plan in place well before 10 knots makes 10 degrees good.

 

 

The well flown approach starts at a specific airspeed that is held while you initiate descent with power, hold that airspeed until you visually determine rate of closure is increasing, at which point you start a deceleration to arrive at a hover/ground contact motionless and with minimal (if any) discernible attitude change. Crosscheck indications of airspeed, power and rate of descent to ensure the plan is sound so you can abort early if it isn't. If my attitude (deck angle), power, airspeed and rate of descent are good at 200' AGL, the approach assumptions were at least ball park and concentrate on holding that through surface turbulence and looking for obstructions that will appear as I near.

Edited May 14, 2013 by Wally

[eagle5]

Before I would attempt to answer your question I would want to get some background information. Are these instructors you are flying with also flying with you during your settling with power maneuvers ? A lot of their reactions to confined area techniques could be explained by their attitudes and reactions when they are teaching or evaluating your settling with power training.

 

Some of them yes. The last guy, no.

[eagle5]

I think maybe the reason people don't like your #1 approach is you slow too early...

I prefer to keep the speed up until we are closing on the final phase of the approach. I have flown with a number of pilots who do as you suggested and here we are 200 yards from the spot slowing below 20 kts and it feels uncomfortable to me. I feel like they are about to get themselves on the underside of the power curve and if we were pushing the limits of HOGE I would be concerned about VRS.

 

That's just it though. If I can't go that slow, then I'll find out with plenty of altitude to do something about it. If I came screaming in (fast and steep) I wouldn't find out that I can't HOGE until its too late and the skids are flat as a pandcake!

 

About 50' up the last guy looked over at me and said, "You know this is the condition that leads to VRS right?" I looked down at the VSI which was at about 150fpm, looked outside to see that we were barely moving and thought, "How can I get into VRS descending this slowly?"

[apiaguy]

Also... Have you ever been into a confined area where you didn't have sufficient power to hover OGE? I don't mean a confined area the size of the rotor disc or double that even but maybe a place amongst 50' trees but where you don't have to make a vertical decent in the final landing. Maybe the ship will hold 10-15' but that's it. The reason I ask this is when I have pilots demonstrate under these conditions and they slow early I am just anticipating that 50-100 rpm rotor droop as they start to slow when they are still 30-50' agl... the ship will barely hold 10-15' at max rpm.... Basically I feel like they are going to droop the rotor in the final phase and we will settle thru and possibly have to touch the skids to stop the decent. It is one of my favorite tests with lower time pilots and sometimes it is a pinacle not a confined area... They get all scared like they are crashing and keep pulling up on the collective as they keep mushing thru with low rpm.

 

Edit: I think you just need to practice some different variations with the understanding that each circumstance is variable and may warrant a different technique. Most of where we fly in the mountains is above HOGE but that doesn't mean we can't land in a confined area... it merely adjusts the definition.

Edited May 14, 2013 by apiaguy

[kodoz]

[apiaguy]

yeah ok kodos... but according to Prouty (which I don't have in front of me) that onset can be much lower ROD in the R22 or similar...

 

I believe Kodos and I have had this very conversation in flight some years ago... he preferred the slower approach... i preferred the faster... when I demonstrated what I meant I was TOO fast! Haha..

[Hovergirl]

I agree that 10 kts is a bit too slow - probably just below rather than just above ETL, which is where I would like to be. Coming in faster will use less power but that high rate of descent will require a larger power adjustment to stop, and if you are coming into an off airport site there is always the possibility of the wire or obstacle you didn't see before - I'd rather be approaching that at 15 kts than 40. I generally start the descent at 40 kts, but have slowed down both airspeed and ROD by the time I reach treetops and make my go/no go decision.

[eagle5]

Also... Have you ever been into a confined area where you didn't have sufficient power to hover OGE? I don't mean a confined area the size of the rotor disc or double that even but maybe a place amongst 50' trees but where you don't have to make a vertical decent in the final landing. Maybe the ship will hold 10-15' but that's it. The reason I ask this is when I have pilots demonstrate under these conditions and they slow early I am just anticipating that 50-100 rpm rotor droop as they start to slow when they are still 30-50' agl... the ship will barely hold 10-15' at max rpm.... Basically I feel like they are going to droop the rotor in the final phase and we will settle thru and possibly have to touch the skids to stop the decent. It is one of my favorite tests with lower time pilots and sometimes it is a pinacle not a confined area... They get all scared like they are crashing and keep pulling up on the collective as they keep mushing thru with low rpm.

 

Edit: I think you just need to practice some different variations with the understanding that each circumstance is variable and may warrant a different technique. Most of where we fly in the mountains is above HOGE but that doesn't mean we can't land in a confined area... it merely adjusts the definition.

 

No I haven't, but then again, if it'll hold 10-15' then it does have sufficient power to hover OGE, so I don't really get what you're driving at?

 

I've never been in your test situation because if after doing a power check I see that I cannot HOGE then I just don't attempt the landing, since even if I did make it I might not be able to take off.

 

Besides, if you don't have the power to hover OGE, and the LZ's OGE and you're coming in fast, when will you realize that you don't have the power to hover OGE?

[apiaguy]

If it will hold ONLY10-15' and won't climb further that is not going to hold a OGE hover... you are definitely getting some ground aid at that point. The point I'm suggesting is that alot of times we find ourselves limited in one fashion or another and being able to still accomplish the task may just take a little adjustment of our skill set.

 

That is fine if you don't attempt the landing if it won't HOGE... you're safe. The reality of flight is that you may need to land there or somewhere near there for the job you're doing and being a professional I would hope you have learned somewhere in your training how to accomplish that without simply saying "I can't HOGE so we are not landing"

 

I also am not saying come in fast..... I shoot the approach above 40kts until the last 150 agl at which I'm in a slow controlled decent (think linear) that arrives me at my predetermined spot. I'm only at 10 kts as I am about 20 ft. I'd say.

 

Edit: The time to realize you can't hover OGE is during your preflight performance planning. I'm not a big advocate of piston engine "power checks" for attempting altitude landings because the identification of a particular map setting doesn't mean you'll be able to climb vertically unless you have some huge availability which doesn't exist in real flight in the mountains. We are usually right on the line or very close to either the OGE or IGE ceilings. When the air is stagnant in that hole and the grass and trees are making a nice convective oven your real performance may be considerably less than HOGE charg says. Be prepared to know where you can go. That's my idea of training; realistic.

Edited May 14, 2013 by apiaguy

[eagle5]

If it will hold ONLY10-15' and won't climb further that is not going to hold a OGE hover... you are definitely getting some ground aid at that point. The point I'm suggesting is that alot of times we find ourselves limited in one fashion or another and being able to still accomplish the task may just take a little adjustment of our skill set

 

I take it then, that if you're at 10' and max power (over say, grass or dirt) and you push forward, takeoff, then come back around and try to pull it into a hover at 50', you won't be able to do it?

 

...or in other words. I could do my power check higher up, see that I can't HOGE, but still be able to land because I could get "some" help from the ground, allowing me to land, just not climb without ETL?

Edited May 14, 2013 by eagle5

[Spike]

I realize that at below 1000hrs I'm not that experienced at this, and I'm doing it in an R44, so I don't have many other aircraft to compare to, but I feel more comfortable with technique #1 (coming in slow and controlled).

 

However on two seperate occasions with two seperate CFIs (one of whom was also a high time old guy and DPE) when they took the controls and showed me how they prefer it to be done, I looked over and 40kts/600fpm was what I saw,...and we were getting pretty damn close (as my butt-cheaks began to clentch)! Both of these CFIs (as well as a few others on seperate occasions) have remarked while I was coming in nice and slow, that we're getting close to VRS (one even reached over and pushed the cyclic forward as he said it)!

 

Coming in "hot" like these guys did, I really hope they always have the power to stop that high ROD! My prefered technique may be too slow for some, but at least I'll know if I have the power to hover high enough to change to something else if I don't!

 

Question:

What approach angle should you use during confined area operations?

 

[apiaguy]

correct. When you are above the HOGE ceiling you can pick it up and do a very slow vertical ascent. As you start to get to the top of that "bubble" the ship will slow down and stop... you can pull just a pinch more pitch and it will climb a few feet as rpm starts to drop... then if you are not real soft on letting off some pitch and "milking it" your ascent will become a nice descent as rpm is now lower than max and the engine is already giving everything she's got scotty. More than a few pilots I've flown with do this the first few times and want to keep pulling pitch as the descent starts (that's a no-no) they get scared and start shaking the cyclic all over (as if that helps).

As soon as you get back on your bubble the descent will slow and hopefully you'll be able to regain your rpm without having to touch the skids (if you didn't drag it down too much).

Just did this with my primary student at his house (a pinnacle on top of a 4600' hill with trees everywhere) Temp was 90 F. It is great practice to know that if you're really smooth you can go higher by keeping that rpm peaked and to not get so scared when you start to go down... ease up on the collective, there is still cushion for you.

[eagle5]

 

Question:

What approach angle should you use during confined area operations?

 

 

Depends on what you have to fly over to get in, and how much room you have once there.

[eagle5]

correct. When you are above the HOGE ceiling you can pick it up and do a very slow vertical ascent. As you start to get to the top of that "bubble" the ship will slow down and stop... you can pull just a pinch more pitch and it will climb a few feet as rpm starts to drop... then if you are not real soft on letting off some pitch and "milking it" your ascent will become a nice descent as rpm is now lower than max and the engine is already giving everything she's got scotty. More than a few pilots I've flown with do this the first few times and want to keep pulling pitch as the descent starts (that's a no-no) they get scared and start shaking the cyclic all over (as if that helps).

As soon as you get back on your bubble the descent will slow and hopefully you'll be able to regain your rpm without having to touch the skids (if you didn't drag it down too much).

Just did this with my primary student at his house (a pinnacle on top of a 4600' hill with trees everywhere) Temp was 90 F. It is great practice to know that if you're really smooth you can go higher by keeping that rpm peaked and to not get so scared when you start to go down... ease up on the collective, there is still cushion for you.

 

Sounds cool, perhaps someday I'll get to try it?