New approach to landing with a tail wind.

[CharyouTree]

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.

 

UH-60: wind?

[Rupert]

Yes, downwind operations take more power, but the real concern with downwind approaches involves settling with power.

 

For those who have not experienced settling with power (probably everyone reading this), settling with power does not mean the vibration one feels in flight school and during rides with the feds, in which the instructor simply decelerates below translational lift while in a descent; rather, settling with power means falling with the full acceleration of gravity, so that the pen you lost last week lifts up from its hiding place on the floor and floats in zero g's before your eyes.

 

If one must absolutely approach downwind (because one lacks the wits or the time to figure out how to do it into the wind or in ground effect), then I advise coming to an out of ground effect hover at 300' AGL (or higher) and slooooowly feeling your way in with significantly less than a 300 fpm rate of descent (helpful to have an IVSI).

 

If you can make your approach so that you get in ground effect before losing translational lift, you can land safely downwind without regard for settling with power.

 

Conversely, downwind takeoffs in ground effect simply require a little more power. As long as you remain in ground effect and/or above translational lift, you remain safe.

 

=====

 

Regarding LTE: stop thinking of it as an emergency. In a left-footed machine, if the nose starts turning right despite full left pedal, push the right pedal and screw your way up out of trouble. The world will not become an incomprehensible blur. You will stay adequately oriented to fly out of the spin when you get above all obstacles. Trust me. Done that more than once.

[nightsta1ker]

Another option for LTE is to chop the throttle and do a hovering auto. You would, of course, need to be in ground effect, but it is an option. Regarding LTE, I have found that as long as you don't freeze on the pedals you can counter most gusts without losing control. Even I you have to go full pedal to do it. The real danger is when the pilot let's the spin accelerate to a point when even full pedal deflection won't stop the turn. Stay frosty on those pedals and you will very likely be able to counter your LTE. Now, I know there are conditions when even full and immediate deflection won't stop our turn, but you should probably not be flying in those conditions anyway, at least not in a perfect world.

 

I've seen two videos where the pilot had LTE and crashed. Both videos clearly show the pilot was dead on the pedals with nowhere NEAR full deflection applied to counter the initial loss of effectiveness. I guess my point here is, don't stop flying the helicopter until all the spinning pieces come to rest. If you stop flying you will surely crash.

[aeroscout]

With enough open area, or a "way out" you can cyclic your way out of LTE. I've always thought of LTE as somewhat of a misnomer anyway.

[Rupert]

DON'T do a hovering auto because of LTE. And forget about flying out of it with cyclic. Flying out of it with cyclic only happens in the movie in your head or in the Brown Sugar story your flying buddy invented to impress you. Just push the right pedal and go up and away from the ground.

 

When you think about LTE, imagine yourself in an out of ground effect situation. LTE so rarely happens in ground effect as to justify saying it doesn't happen in ground effect. Typically, when in ground effect with insufficient tail rotor authority, one hits the stop and the ship whips around and weathervanes into the wind (you go around less than once).

 

The stories about the pilot not getting enough left pedal in or not soon enough usually involve a right yaw on takeoff and the tail rotor getting into the main rotor vortex. In this situation, if the ship swaps ends, it will do so only once. If the ship goes around more than once, push right pedal.

 

Why would the ship yaw right on takeoff? Probably because the pilot took of from a ledge or a pinnacle, in ground effect, and encountered an out of ground effect situation before getting into translational lift. Like, maybe, taking off from a ledge on a slope, with tall trees down slope; the ship begins the takeoff in ground effect but as soon as the ship gets off of the ledge and above the downslope, the ship enters an out of ground effect situation. Suddenly, the ship needs a large input of power/torque in order to maintain altitude. If the pilot already has a boot full of left pedal in, then he doesn't have enough left pedal remaining. Worst case, the pilot can't even maintain rotor rpm and begins to settle between the slope and the trees (done that). In which case, full right pedal takes all the power formerly directed to the tail rotor and puts it back in the main rotor, and the helicopter spins to the right and climbs vertically (done that).

 

Don't let the thought of spinning scare you. Even at full right pedal you can stay oriented.

 

Put this in your bag of tricks:

 

When you hit the left stop and the ship spins right anyway, and you have nothing but skid-chewing rocks and tumbling-airframe slope beneath you, push full right pedal. When you push full right pedal in this situation, something good will happen. You will climb straight up. Do NOT autorotate. When you get well above all obstacles, reduce power, apply left pedal and right cyclic, and fly away.

[nightsta1ker]

I have had LTE in ground effect. It was because I did not catch it in time. Went all the way around once, like you said, and was able to regain control. It was a eye opener. And thinking back on that day, if I had tried to auto to that spot I probably would have rolled it over, so you are probably right. Just push the right pedal and climb out. Or let it go around once and catch it when it's facing the wind. Just don't stop flying the ship. If you freeze, you might go around more than once, or sink and do a dynamic rollover or any other number of things.

 

Giving me the shivers just thinking about it.

[aeroscout]

I have had LTE twice, but was careful enough to approach the pinnacles I was flying to with a very well defined, and clear way out. I was able to cyclic out of them using those ways out.

[johnnyb]

why wouldn't you.

 

Land with a tail wind?

Because the tail wind is effectively blowing your induced flow out in front of you, which you're flying into; even with a very low descend rate you're settling with power, even if gently so. Bad.

[nightsta1ker]

Land with a tail wind?

Because the tail wind is effectively blowing your induced flow out in front of you, which you're flying into; even with a very low descend rate you're settling with power, even if gently so. Bad.

 

Really? Well, lets think about this for a minute. If you are in a situation where the rotor system is flying into it's own induced flow, you may start to develop some vortices within the blade disc. Just because this condition exists on some level within the rotor system does not mean that you are in a settling with power condition. In order to settle with power you would need to be in a vortex ring state so well developed that it overcomes the rotor's ability to create lift sufficient to keep the helicopter in the air. In order for a vortex to develop to this point you need to have a descent rate of more than 300 FPM, be flying at a speed below ETL, and also have 20% or more power applied to the rotor system. As long as you keep your descent rate shallow (and I mean, really shallow, like less than 150 FPM), even with a tail wind you can execute a landing without putting yourself into a settling with power condition. Where settling with power bites pilots is when they are coming in too fast, too steep and trying to slow down and drop down on their spot. A tail wind can exacerbate this condition and make a normal approach become dangerous. If proper precautions are taken, tail wind landings can be executed safely.

[Bobsyouruncle]

There was an interesting discussion on this. Nick Lappos is a respected experimental pilot who works with Sikorsky. Lots of interesting stuff.

 

http://www.pprune.org/rotorheads/18873-t-o-downwind-v-power-available.html

[aeroscout]

Safe landings with tailwinds that are light are a lot more possible than if the tailwind is equal or greater than ETL, then, not so much.

[johnnyb]

Really?

 

Yes, really.

Thanks for quoting textbook settling with power, let's consider the three elements of SWP.

Fact of the matter is, on an approach with a tail wind, you're going to be pulling power, most likely 20% or more, especially in a smaller model, since your induced flow is in front of you you're going to need much more power / pitch; you don't have ETL especially towards the end of your approach since the wind is behind you; yes your descend rate staying under 300fpm technically means you're not settling with power but with all the other variables you're on the verge?

In addition to that a tail wind is going to have you working those pedals, your torque is going to fluctuate which puts additional strain on your power management. Add a bit of hot, heavy and humid and yeah...

That's what I meant with "you're settling with power, even if gently so"

 

There's a very fine line between the classic settling with power proper, with little to no relative airspeed, you're descending like a brick in shitstorm and you're pulling tons of power - you know, the type your instructor induced, where you have tons of time to feel what the "mushy controls" feels like; and the other kind you're on the verge off during every steep approach or when you're stupid enough to do be doing downwind approaches.

 

Downwind approach and landings are possible yes, I didn't say they're not, but there's a reason they should be limited or avoided altogether. And wind, about that, with a downwind approach pray your tailwind is constant, the slightest wind shear and there goes another beautiful helicopter.

 

The theory remains the same, regardless of the aircraft.

[nightsta1ker]

Yes, really.

Fact of the matter is, on an approach with a tail wind, you're going to be pulling power, most likely 20% or more, especially in a smaller model, since your induced flow is in front of you you're going to need much more power / pitch; you don't have ETL especially towards the end of your approach since the wind is behind you; yes your descend rate staying under 300fpm technically means you're not settling with power but with all the other variables you're on the verge?

In addition to that a tail wind is going to have you working those pedals, your torque is going to fluctuate which puts additional strain on your power management. Add a bit of hot, heavy and humid and yeah...

That's what I meant with "you're settling with power, even if gently so"

 

There's a very fine line between the classic settling with power proper, with little to no relative airspeed, you're descending like a brick in shitstorm and you're pulling tons of power - you know, the type your instructor induced, where you have tons of time to feel what the "mushy controls" feels like; and the kind you're on the verge on doing steep approaches or when you're stupid enough to do be doing downwind approaches.

 

Downwind approach and landings are possible yes, I didn't say they're not, but there's a reason they should be limited or avoided altogether. Something tells me you won't be around for long if you insist on doing them so I'm most likely talking to the wind.

 

I would argue that every approach could be considered "gently settling with power". You are under power. And you are settling, hopefully, gently. Don't mince words here. The term settling with power is associated with a condition in which the helicopter is uncontrollably settling at a rate that will cause a hard landing at best and at worst a crash. It is caused by a fully developed vortex ring that becomes exacerbated when the pilot tries to arrest the descent with increased collective. As long as these risks are considered and the maneuver is executed with caution, it can be done safely. However, there are definitely conditions in which I would not attempt a tailwind landing. Hot, high, heavy with a moderate to strong tail wind is just asking for trouble. Use common sense!

 

I agree with you that downwind approaches should be avoided,but sometimes they simply cannot be. Experience will teach you this. You will not, I can almost guarantee you, go through your entire helicopter pilot career without being forced to execute a tailwind landing at some point. When it happens, use your best judgement and exercise caution.

[johnnyb]

downwind approaches should be avoided,but sometimes they simply cannot be. Experience will teach you this. You will not, I can almost guarantee you, go through your entire helicopter pilot career without being forced to execute a tailwind landing at some point. When it happens, use your best judgement and exercise caution.

 

Well said.

[Gomer Pylot]

"Settling with power", more properly termed vortex ring state, should never be a problem on a properly flown approach. It shouldn't even be possible. It takes a considerable descent rate to get into it, depending on the weight of the aircraft, and with even a 206 it takes close to 500'/min to get it started. A proper approach, downwind, crosswind, or into the wind, should be under 200'/min from between 100 & 200 feet above the landing point. The approach should always terminate with no discernible flare. If you have to flare to stop, you're too hot, and that will always increase the chances of bent metal. Properly flown, a downwind approach should use no more power than one into the wind, but the point where the most power is required occurs much earlier, where ETL is lost and airspeed is zero. Zero airspeed will always require more power than with a wind from any direction. The only problem with a downwind approach is that groundspeed is higher for a given airspeed, and it therefore has to be done slowly, and low airspeed used. The real danger is engine failure, and the result of having to land with groundspeed higher than zero. It's the same with a downwind takeoff, where you transition from possible ETL from the rear, to zero airspeed with considerable groundspeed, and the resultant long takeoff distance and shallower climb angle. If the engine quits, you'll have to put it down with some ground run, depending on the windspeed. It's because of the increased likelihood of damage from an engine-out auto that downwind takeoffs and landings should be avoided. Don't make them lightly, without considering the dangers, but don't completely avoid them if the alternative is even more dangerous. Sometimes they have to be done, and it's far better to practice them occasionally, so you know how to handle before you have to do it for real. And if you plan to make a living flying helicopters, you'll have to do them now and then. Lots of techniques need to be in your bag of tricks, including sideways approaches, downwind approaches, and everything else. Use whatever seems to be the safest at the time, and always make the approach slow. Speed kills.

[KBayDog]

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.

 

Tailwinds certainly have an effect on tandem birds with respect to power required, ETL, etc. The main thing tandems don't have to worry about, of course, is LTE. Prior to TERF (Terrain Flight), we would do power checks by conducting 360 degree pedal turns IGE and OGE, noting our torque. There was always a definite increase in power required when the tail went through the wind line, and gave us a good idea of our actual power margin prior to maneuvering.

[aeroscout]

I don't know if I can agree with you on the 15 knot tailwind chasing a ship going 15 knots away from you scenario.

[ridethisbike]

In what way aero?

[KBayDog]

I don't know if I can agree with you on the 15 knot tailwind chasing a ship going 15 knots away from you scenario.

 

It was an overly simplified scenario for the discussion.

 

It has been removed.