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Right quartering headwind?


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Ok, more questions...I know, I should be saving these for my instructor...or waiting for this to (finally) come up in a ground lession...but...long story short, we've both been sick/busy/holidays/weather and I haven't had ground in forever.

 

 

Anyway.....

 

I keep coming across "quartering" winds in my studies.

 

I really can't find any good explaination.

 

One of the Test Prep questions (#3809 for example) states:

 

The segmented circle indicates what a landing on RW 26 will be with a:

 

a-right-quartering headwind

b-left-quartering headwind

c-right-quartering tailwind

 

 

I've tried to logic out the correct answer, search texts, etc.....to no avail.

 

Can yah'll explain?

 

I have honestly tried to ignore it, and just wait until I get to that point in ground....but I can't stand it anymore!!!!!!

 

 

THANK YOU!!!

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Ok, more questions...I know, I should be saving these for my instructor...or waiting for this to (finally) come up in a ground lession...but...long story short, we've both been sick/busy/holidays/weather and I haven't had ground in forever.

 

Quartering winds are in between crosswinds and head/tail winds. If you're landing on 36 and the wind is from 090, you have a crosswind. If the wind is 045, you have a quartering head wind, and if the wind is 120, you have a quartering tail wind.

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Hmmmmm. Now that makes sense. Thanks, Kodoz.

Figured it'd be pretty simple once s'plained.

 

 

Now, is what you described a RIGHT quartering headwind? (meaning it's on the a/c's right side?)

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And....THANKS everybody for putting up with my newbie questions. I do appreciate all the help and explainations.

 

I am not one to just learn something part-way...I need to really feel that I understand things completely. Probably a good thing in this profession, eh?

 

What's a girl to do.

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Hmmmmm. Now that makes sense. Thanks, Kodoz.

Figured it'd be pretty simple once s'plained.

 

 

Now, is what you described a RIGHT quartering headwind? (meaning it's on the a/c's right side?)

 

Yes, just as with head/tail winds, it's relative to the a/c. So in my example the wind from 045 while you're landing 36 is a right quartering headwind, and a wind from 090 is a right x-wind.

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  • 3 weeks later...

ok, next issue.

 

Why is it bad to land with a tailwind?

 

I can guess you'd need more cyclic authority to keep the nose from pitching down, and you'd have decreased TR effectiveness, what else?

 

 

Just trying to get a real grip on how winds can affect helicopters (specifically R22's).

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Don't know whether you have gotten this far yet, but landing with a tail-wind greatly increases the chances of encountering Settling with Power, the state in which the helicopter descends into its own rotor wash.

 

Landing with a tailwind is not a "Bad" thing to do, as long as you do it right, (maintain ETL as long as possible through the descent, keep your descent rate slower than 300fpm, etc). It is just preferable to land with a head wind.

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Don't know whether you have gotten this far yet, but landing with a tail-wind greatly increases the chances of encountering Settling with Power, the state in which the helicopter descends into its own rotor wash.

 

Landing with a tailwind is not a "Bad" thing to do, as long as you do it right, (maintain ETL as long as possible through the descent, keep your descent rate slower than 300fpm, etc). It is just preferable to land with a head wind.

 

 

BINGO !!!!!!!!!!!! Especially, as we all know, in high weight, high DA conditions.

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I can't even begin to tell yah'll how stupid I now feel for asking about TW.....settling w/ power....DUH!

 

Was I correct with my other 2 examples?

 

" I can guess you'd need more cyclic authority to keep the nose from pitching down, and you'd have decreased TR effectiveness...."

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I can't even begin to tell yah'll how stupid I now feel for asking about TW.....settling w/ power....DUH!

 

Was I correct with my other 2 examples?

 

" I can guess you'd need more cyclic authority to keep the nose from pitching down, and you'd have decreased TR effectiveness...."

 

Sort of. You have to go one step deeper and ask yourself why does the nose pitch down. It's because as you slow down, the airflow through the rotor system becomes less horizontal, which increases induced flow. As induced flow increases, the angle of attack decreases, so more aft cyclic is required to compensate.

 

Landing with a tailwind simply makes all of the above happen sooner and while at a higher forward airspeed. For example, if you have a 15 kt tailwind on final approach for landing, then when you are moving forward at 15 kts IAS, you are effectively at a hover already (and more power is needed because of the greater induced flow). Also as you slow down on approach, the tailwind will "blow" vortices that you were previously outrunning back onto the main and tail rotor, so you also enter "disturbed air" sooner.

 

The opposite is true with a headwind. Imagine doing an approach to landing with a 15 kt headwind. In effect, you may never get below ETL for the entire approach. This more horizontal airflow and being able to stay ahead of vortices for the whole approach means significantly less power (and power changes) is required for the entire approach.

 

Hope that makes sense...

Edited by palmfish
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For example, if you have a 15 kt tailwind on final approach for landing, then when you are moving forward at 15 kts IAS, you are effectively at a hover already (and more power is needed because of the greater induced flow).

If you are at 15 KIAS, wouldn't you be in ETL regardless of where your wind is from? My understanding is that airspeed is airspeed. If you have 15kts indicated, you are moving forward through the air at 15kts and if you have a direct tailwind of 15kts that just means your ground speed is going to be 30kts.

Edited by me shakes fist
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If you are at 15 KIAS, wouldn't you be in ETL regardless of where your wind is from? My understanding is that airspeed is airspeed. If you have 15kts indicated, you are moving forward through the air at 15kts and if you have a direct tailwind of 15kts that just means your ground speed is going to be 30kts.

 

To say ETL starts right at 16 kts is a "generalization" at best. So is my example of flying forward at 15 kts with a 15 kt headwind or tailwind - I used those numbers just to illustrate a point. 15 minus 15 may not always exactly equal zero from the pilot seat, but generally speaking, compared to a no wind situation, a tailwind increases induced flow and a headwind reduces induced flow.

 

If you take off into a 20 kt headwind, you are effectively in ETL the instant your skids leave the ground. It doesn't matter what your airspeed indicator says - it's all about the airflow through the rotor system. If you pick up to a hover facing into a 20 kt headwind, then the airflow through the rotor system is already somewhat horizontal and the rotor vortices are already being blown past the rotor system.

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if you have a 15 kt tailwind on final approach for landing, then when you are moving forward at 15 kts IAS,

 

This statement is wrong.

 

That's what 'meshakesfist' picked up on.

 

However, I think Palmfish put IAS instead of GS deliberately as a test to see who was observant. Well done 'meshakesfist'.

 

Quarting tailwind was explained well.

 

I'm surprised none of these posts have mentioned 'weathercock stability' as a specific LTE issue.

 

In short:

 

-SWP

-LTE (Weather cock stability) when groundspeed is less than wind speed.

-High Power requirements to arrest forward speed

-Excessive Nose Up Attitudes

 

That's all I can think of. If you're on top of those issues, then they can be relatively safe if there is no alternative. Given a choice though, into wind is peace of mind and safer.

 

Joker

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The tricky part is taking off with a tailwind. With a 15 kt tailwind, you're hovering in ETL, probably. As you start moving forward, you lose ETL, and need more power, which you may not have available. You have to get up to maybe 30 kts groundspeed before you regain ETL, and you can hit the ground before you're really flying, but with enough forward momentum to really prang it.

 

Landing with a tailwind you lose ETL earlier, and higher, and you end up trying to hover OGE on the approach, and you may not have enough power available to do that, nor enough tail rotor authority to keep it straight while pulling max available power.

 

Tailwinds are bad, mostly for reasons we never think of. Sometimes you have to maneuver with a tailwind, but you really need to think it through before you do it, and only do it if it's absolutely necessary, and be really alert and on your toes while doing it.

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However, I think Palmfish put IAS instead of GS deliberately as a test to see who was observant. Well done 'meshakesfist'.

 

No, not a test - but thanks for the vote of confidence. :huh:

 

I should have said GS instead of IAS. Maybe I should leave this area to the CFI's from now on...

Edited by palmfish
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