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New approach to landing with a tail wind.


bignick
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I would like to bring up the taboo subject of landing with a tail wind. Obviously we are always taught to land with a headwind. At times, landing with a headwind is either impossible or highly restrictive.

 

Up for aerodynamic discussion:

 

I believe if you plan to land in OGE hover power (especially tandem rotor helicopters), you will not require more power. Why would you, or why wouldn't you.

 

Tail rotor helicopters do have issues with tailwinds especially right quartering or left quartering depending on design, but lets step asside from LTE for this discussion.

 

Looking forward to discussion. Thank you.

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Barring LTE, the disadvantage of tailwinds is that it would put you below ETL with a significant groundspeed (depending on how strong the wind is). Lets say the wind is blowing 10 knots from the south. I need to land from the south due to obstacles. Lets say it's a confined area. In order to slow my ground speed for the steep approach, I would lose ETL at around a 15-25 knot ground speed, and in order to hover, I would actually be flying backwards into the wind. This condition can put you in a situation that greatly increases your chances of getting into a settling with power condition. In fact, most settling with power accidents happened when the pilot was attempting to land in a confined area with a tail wind.

 

My advice: Avoid it if you can. But sometimes you gotta do what you gotta do. In those cases, exercise extreme caution, know what you are up against, and keep that descent rate slow.

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The issue is that during a tail wind approach, if flown to the same profile as a still- or headwind approach, you will at some point find yourself with no airspeed, descending, out of ground effect. We all know that this is not generally recommended unless the rate of descent is well controlled, and enough power is available to arrest the descent without the benefit of ETL or ground effect.

 

If enough power is available, and the pilot is expecting the loss of lift, applies collective, maintains heading with the pedals, and controls the ROD, the landing be completed safely.

 

If the pilot is caught off guard, or OGE hover power is not available, the helicopter will "drop" when ETL is unexpectedly lost, a high ROD develops with no airspeed, and there will be an over-torque event, uncommanded yaw, hard landing, or all three in this order.

 

Even if the landing is completed safely, the question remains why the pilot willingly decided to risk a tail wind approach?

With a tailwind approach:

- it is very difficult to abort landing / re-gain forward airspeed.

- There is less chance of successfully landing in case of a power failure.

- brownout/whiteout are more likely if landing on dust or snow.

- there is more risk of running out of pedal in a high torque / tail wind hover situation.

- Some helicopters have maximum tail wind hover limits and can overtemp or even suffer a blade strike.

- etc.

 

If you know it's a tail wind, why not find some way to come in from another angle.

 

 

I believe if you plan to land in OGE hover power (especially tandem rotor helicopters), you will not require more power. Why would you, or why wouldn't you.

 

If you are careful and descent slowly, then OGE power will be enough. If you descent a little too quickly, you will need more than OGE power to arrest the descent as you lose ETL during the approach. Sometimes considerably more. I'm not even talking about vortex ring state here - it's simply a matter of momentum. Hold a 10lbs weight two inches above a table - easy. Now let someone drop the same weight onto your hand - doesn't have to be high, just a few inches - it will smash into the table.

Edited by lelebebbel
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From what I've seen a tailwind or crosswind in the 10-15KTS range amounts to 3 or 4 percent more torque at hover. At one point you would lose airspeed and then you would gain it back again but from the rear. I suppose you could get into settling with power if you descended steep enough but by the time your airspeed gets low enough I doubt any pilot worth a damn would have a rate of descent that high at that low an airspeed especially considering they are likely close to the ground by the time the wind effects a zero airspeed condition.

 

Personally I think if you have the power to compensate for the extra drag than landing with a tail wind isn't very dangerous at all. It's just a matter of why would you do it unless you have to, and of course sometimes you have to.

 

Obviously many people are in aircraft or environments where they don't have power to spare so they live by the rule of landing into the wind.

 

I couldnt tell you about tandem helicopters. It makes sense that a tailwind may have no effect on their power, but I don't know.

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Landing with a tailwind is sometimes the only choice. You have to balance the risks and the other choices. It's certainly possible as long as you are careful and do everything slowly. Be aware that during the final stages of the approach (and this is the same for a downwind takeoff) you'll go from being in ETL, to out of it, and then possibly back into it from the opposite direction. That transition time is dangerous on either takeoff or landing. On approach, if you're moving too fast, you may not have enough power available to stop while still airborne. You'll eventually stop in any case, but it's better to stop with all the parts still attached. Slow is good.

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Slow is good.

 

So much so, I don't even think of it as an "approach". For me, it's basically hovering into the LZ. My angle is dependent of the terrain and/or environment. At this point, the number one concern becomes LTE and not SWP. That is, I control the ingredients necessary for SWP. Mother Nature (aka the wind) can be unpredictable, thus my concern for LTE....

 

Sometimes when conditions dictate, I'll shoot the approach to a preferable LZ, or point in space, and then hover, slowly, DW to the primary LZ. Simply put, there is no reason to shoot a DW approach from 500ft AGL....

 

Lastly, this shouldn't be thought of as a taboo subject. If you fly for money, you will be required to do DW approaches. This is why you're paid to do this....

Edited by Spike
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Depends on the wind and the obstacles, of course. Taking off downwind or crosswind takes more power, so you have to balance the extra power needed for that against the power that would be required to clear the obstacles into the wind. There is certainly not one correct choice. Everything is always a compromise, and judgement is always necessary.

Edited by Gomer Pylot
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One might argue that the same theory is appropriate for downwind takeoffs. Power permitting, IMO, I'd rather take off with a slight tailwind into an clear flight path than to shoot over an extremely unforgiving set of obstacles.

 

Certainly. It's all about mitigating your risks. It's a choice. And needs to be a conscious one. A big risk in downwind maneuvers is the possibility of not knowing you are downwind. I used to be involved with a mountain course in Reno, and I recall a time I elected to depart downhill with a slight tail wind. This is where experience picks up where the performance charts leave off. There are certainly hover charts, but no headwind component, no climb gradient chart. The idea was to turn into the wind and proceed up the mountain. There was another aircraft there that kept trying to bunnyhop up the hill and was struggling to get through ETL. I called out my intentions and the other pilot kept responding in earnest "YOU'RE TAKING OFF DOWNWIND!!!". I told him I was aware and knew what I was doing. I told them to note the difference in altitude between us and the tree line we were both working to cross and the clearance they gave themselves. Ultimately, though, the terrain we were flying over was rough and a forced landing would not have been pretty into wind or not.

 

I was fortunate to be based at a flight school that taught downwind maneuvers in their courses so I had made plenty of downwind takeoffs prior to being on the edge of the envelope.

 

Regarding decision making: As an instructor, teaching downwind takeoffs, patterns and approaches, when the pilot in training had done several patterns and was getting used to the whole process, on a turn to base, I would simulate an engine failure and see what direction the pilot would turn. It was hard for many to turn into the wind instead of making the same turn they had made 5 times leading up to this. I know I would probably fall into the trap of continuing the same way I had for the past several patterns. I thought t was a good exercise in situational awareness and also the human element.

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Certainly. It's all about mitigating your risks. It's a choice. And needs to be a conscious one. A big risk in downwind maneuvers is the possibility of not knowing you are downwind. I used to be involved with a mountain course in Reno, and I recall a time I elected to depart downhill with a slight tail wind. This is where experience picks up where the performance charts leave off. There are certainly hover charts, but no headwind component, no climb gradient chart. The idea was to turn into the wind and proceed up the mountain. There was another aircraft there that kept trying to bunnyhop up the hill and was struggling to get through ETL. I called out my intentions and the other pilot kept responding in earnest "YOU'RE TAKING OFF DOWNWIND!!!". I told him I was aware and knew what I was doing. I told them to note the difference in altitude between us and the tree line we were both working to cross and the clearance they gave themselves. Ultimately, though, the terrain we were flying over was rough and a forced landing would not have been pretty into wind or not.

 

I was fortunate to be based at a flight school that taught downwind maneuvers in their courses so I had made plenty of downwind takeoffs prior to being on the edge of the envelope.

 

Regarding decision making: As an instructor, teaching downwind takeoffs, patterns and approaches, when the pilot in training had done several patterns and was getting used to the whole process, on a turn to base, I would simulate an engine failure and see what direction the pilot would turn. It was hard for many to turn into the wind instead of making the same turn they had made 5 times leading up to this. I know I would probably fall into the trap of continuing the same way I had for the past several patterns. I thought t was a good exercise in situational awareness and also the human element.

 

That's why that school produced "ready for the real world pilots" and eventually sold for 15 million. Never again will we see such an operation.

 

1992 Alumni

Edited by Spike
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That's why that school produced "ready for the real world pilots" and eventually sold for 15 million. Never again will we see such an operation.

 

1992 Alumni

 

Ha! I don't know if your comment is in reference to an interview some trade magazine did with me when I was there or not. That would be pretty impressive on your end if it was. I was just thinking the other day how the identities of various members here are known by other members you'd not ordinarily think. Not that it's any big secret really.

 

Re: the 15 million. The examiners were to blame for the success of that (Ad)venture. And, it also came down to the individual, because there were no shortage of muppets that came from there, too. (Not trying to be too harsh, because I am certainly half muppet myself, mostly on my father's side)

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Ha! I don't know if your comment is in reference to an interview some trade magazine did with me when I was there or not. That would be pretty impressive on your end if it was. I was just thinking the other day how the identities of various members here are known by other members you'd not ordinarily think. Not that it's any big secret really.

 

Re: the 15 million. The examiners were to blame for the success of that (Ad)venture. And, it also came down to the individual, because there were no shortage of muppets that came from there, too. (Not trying to be too harsh, because I am certainly half muppet myself, mostly on my father's side)

 

Does this remind you of anything?

 

 

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I think I have to claim muppet status on that one? Maybe another hint?

 

Theme song to the promo video. Maybe that was before your time. I still have a VHS copy. I should convert it to digital and put it up on YouTube. It'd be a good example of what used to be.......

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I would like to bring up the taboo subject of landing with a tail wind.

 

This condition can put you in a situation that greatly increases your chances of getting into a settling with power condition. In fact, most settling with power accidents happened when the pilot was attempting to land in a confined area with a tail wind.

 

I was fortunate to be based at a flight school that taught downwind maneuvers in their courses so I had made plenty of downwind takeoffs prior to being on the edge of the envelope.

 

 

Instead of teaching students how to handle downwind maneuvers, many flight schools still promote these taboos, myths, and fears about downwind flight. This has been one of the training weaknesses that may have led to many settling and LTE accidents.

 

Had they received some training and experience in downwind maneuvers they could have remained steps ahead of their aircraft, by being aware and comprehending the feel of the aircraft and what it’s telling them.

 

If you’re planning on working utility, were you’re working at gross weight most ever turn, you’re going to have to takeoff, maneuver, and land with winds from all directions. You’ll have to learn and experience working in conditions with full left pedal, at the stops. All part of production oriented projects that require you to get the most out of the helicopter.

 

You’re on a powerline job in mountainous terrain doing skid transfers in 10-15 knot gust. The project manager doesn't want to hear you can’t get it done because the tower wasn’t built facing in the prevailing wind direction. The manager knows better, he’s seen it done.

Edited by iChris
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Quote from Chris...

 

"You’re on a powerline job in mountainous terrain doing skid transfers in 10-15 knot gust. The project manager doesn't want to hear you can’t get it done because the tower wasn’t built facing in the prevailing wind direction. The manager knows better, he’s seen it done. "

 

This type of attitude can quickly turn to disaster, or get a properly cautious pilot dismissed.

 

Regarding downwind landings, if the wind is at a speed at or above ETL, the final portion of the landing will induce ETL backwards.

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I honestly think it's on the BS side to not teach students downwind maneuvers for some of the very reasons mentioned.

 

On my check ride my examiner had me try a down wind "no collective" take off. Looking back, I know I can do it, but at the time I wasn't able to. I was just trying to force ETL and had to raise the collective once to avoid ground contact. After getting back to the airport I realize I have done "no collective" take offs plenty of times into the wind by being patient and not trying to force anything. "Hover power is takeoff power" after all...

 

For clarification purposes, no collective take off just means not raising the collective to MCP when pitching forward.

 

I think I'm going to ask my instructor if we can do some downwind maneuvers. Hopefully he says yes...

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Big brush fire here recently, bunch of aircraft fighting it. One of them was a Washington State DNR Huey/205/UH-1H/whatever with a bucket on a very short line that was staging out of our airport. For the first two days the wind was out of the west. The ground crews oriented the parking spot with the fuel truck, etc. facing west. The pilot simply made his approaches right to the spot.

 

The third day the wind shifted around to the east. Sure enough the Huey pilot made the exact same approach he'd made for the last two days, landing directly downwind. The ground guys were throwing dirt in the air, showing the pilot the wind, but he took off downwind as well. Did this repeatedly, all day long. At least one of the ground-pounders was an airplane pilot (we overheard them talking) and even *he* knew the "rotor" pilot was operating downwind.

 

At one point a LongRanger came in, following the Huey, landed directly downwind, fast and shallow. After switching out pax, he lifted off and departed into the wind. Must've finally realized his mistake (not that the wind wasn't visible on the windsock right near the ramp).

 

The Huey pilot must've just been complacent. We figured that he was used to all that OGE work and really didn't care anymore about wind direction. Dip, drop, dip, drop, dip, drop...over and over and over...wind coming from...wherever...what did it matter?

 

But more than that, he was sloppy. PIckups and setdowns were rough and careless. He dragged his bucket across the pavement on every landing and takeoff. No hover check, just pull and go once the bucket was in the air. On every approach you could see the ship get squirrely as he lost ETL while still moving forward at a good clip. You know that feeling? That uncomfortable feeling that you get when you're still 100 feet up and you realize, "Oh sh*t, the wind is behind me" and the ship starts wobbling around and getting goofy and you're working hard to keep it all together. I hate that.

 

I am not the best pilot in the world - heaven knows I make mistakes even at this hour level. But I tell ya, I'd shoot myself if I ever got that sloppy.

 

Let's say you make a downwind approach to our airport and you have the dreaded engine-failure-at-the-worst-possible-time. Lower the pitch and keep her level. You know you're going to run it on, so okay. Only...our airport is super-soft sand. If you don't manage to get it onto the runway (no parallel taxiway here!) you are GOING to ball it up, no doubt.

 

Sure, downwind operations are possible, and sometimes preferable, and sometimes necessary, and should be taught to all pilots. But we should still strive to land and takeoff into the wind whenever possible, and not accept a downwind situation merely because of convenience or carelessness.

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To those of you that are still in training and thinking about doing some "downwind" training sparked by this thread, I suggest that you evaluate who will give you this training?

 

Ask your CFI if they ever had such training, how much & how long ago?

 

Ask your CFI if they have given this training recently and to what certificate level of pilot?

 

Ask your CFI if it involves some formal ground school and flight training from a syllabus or lesson plan and for what Certificate level?

 

Ask yourself if it is prudent to ask "your" CFI to do this?

 

Stay safe.

 

Mike

Edited by Mikemv
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I will admit that I have no "downwind" training other than being taught to avoid it like the plague. I know this is not really how real world flying works though, so I do cover it with my students during ground. Aside from a few operational situations (doing real work by myself) where I was forced to do tailwind landings or tailwind OGE hovering, I don't really have much experience in this area. But I understand the dangers and do my best to pass that knowledge onto my students, even though I have not taught anyone how to do downwind landings. That to me is very advanced stuff from a training perspective with potentially disastrous results. If I teach Joe Blow 200 hour commercial pilot how to do downwind operations, even if I preach the dangers and blow safety out my butt like sunshine, he is still going to go into some situation cocky thinking "that's no big deal, I've done that before". I think a little fear is a very healthy thing in the helicopter world. Having been taught that doing a tailwind confined area approach is extremely dangerous and should be avoided at all costs taught me that when I was faced with a situation where I had no choice, I exercised EXTREME caution and guess what, I'm still here.

 

Not to say there are no good or experienced instructors out there that are perfectly capable of teaching these techniques effectively. There are. But I would say that a lot of pilots out there are taught the basics and the advanced stuff is self-taught.

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Something funny happened in Army training.

 

Primary - Dont land with a tailwind

Instruments - Dont land with a tailwind

BWS - TSLOW - Dont land with a tailwind

 

OH58D course - sometimes sh*t happens, you get a tailwind. Deal with it.

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To those of you that are still in training and thinking about doing some "downwind" training sparked by this thread, I suggest that you evaluate who will give you this training?

 

Ask your CFI if they ever had such training, how much & how long ago?

 

Ask your CFI if they have given this training recently and to what certificate level of pilot?

 

Ask your CFI if it involves some formal ground school and flight training from a syllabus or lesson plan and for what Certificate level?

 

Ask yourself if it is prudent to ask "your" CFI to do this?

 

Stay safe.

 

Mike

 

Very good point. I shall take heed.

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Something funny happened in Army training.

 

Primary - Dont land with a tailwind

Instruments - Dont land with a tailwind

BWS - TSLOW - Dont land with a tailwind

 

OH58D course - sometimes sh*t happens, you get a tailwind. Deal with it.

 

Yup, sh*t happens, and it's good to know how to deal with it. We get cleared in often times with a tailwind, sometimes we accept it, sometimes we request a different approach.

 

Sometimes the only way in is with a tailwind, and sometimes you don't know exactly what the wind is doing until you make the approach.

 

As for tailwind approaches in a tandem, they still suck for us too.

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