T/O Downwind -v- power available ?
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Help!! I think we all agree!! But we can't agree that we agree!!
Almost all the time, Downwind bad, upwind good - repeat after me.
Roofus says (see >>> ):
>>>Nick Are we calling Helipad profiles Towering? Towering to me means vertical. Helipad profiles are not vertical.
NL -- Nope, "helipad" procedures (I never have called them that, but have at it) are Cat A/Group A procedures. Many helos have towering takeoff procedures that are Cat A. We have one for the C+ or B that allows nearly vertical to 140 feet. I believe similar procedures exist for Bells and EU's as well. In Black Hawk, I have helped make procedures that allow towering takeoffs to 175 feet with single engine capability all along the takeoff.
>>>IAW the ANO any aircraft flying whilst carry pax must conform to Performance Profiles as laid down in the Flight Manual.
NL - Nope, that is not entirely correct. If the operation is part 91 (Private) in the states, the procedure need not be a full Cat A/Group A one, regardless of the number of pax. If for hire (Commercial) it usually requires same, but may be Cat B, where only a safe landing must be assured after failure, even with 6 engines.
>>>Yep...they restrict you. Yep...they ensure single engine climb...um...that's exactly the
point! That is why they are there!
NL - Yep, and some can allow towering procedures, too.
>>>To say not to use the published profiles to allow you flexibility, is shocking! (fingers crossed I misread that!)Professional pilots have a responsibility to those they carry. As such the published profiles must be used...thus giving the greatest chance of a safe conclusion to any'mishap'. To use commercial pressures as justification for going against the aircraft Flight Manual is equally shocking!
NL - You speak of "the Flight Manual" as if there is one procedure, brought down from Moses, and if you ever even think of another, you will be struck down. Gimme a break, there are at least 6 take off procedures for the S-76 family, I helped develop three of them myself. They are remarkably different, and are each designed to help maintain the safety you seek. Some are towering, and if an operator ever wanted one downwind, they can be qualified downwind!!
Of those procedures, none are legally "required" of a private operator.
>>>I stand by my earlier statements. If you're considering downwind approaches or T/Os ask WHY??? Look for an alternative....or use the statement 'I can't get in there' So...I also stick by my earlier statement.... I fly Police & will only consider a downwind approach & T/O if it is Life or Death & I have no other alternative.
NL-- The operative words in the above are "I can't get in there" If you really need to, it is incombant on the professional to figure out how, safely. This is a technical discussion, and there are technical means to achieve almost any point of performance you need. If you say No often enough, someone else will come along just a bit more open minded, and will buy a helicopter with a bit more performance or control, and will say "Yes, I can do it" and he will fly past your house every day, doing your job. Keep on believing that downwind operations are never possible, just don't think that is fact.
>>>Yes helicopters can take off & land downwind, yes instructors teach you these techniques, NO they shouldn't be taken lightly. I'm not saying they can't be done...they can But not as safely as into wind & in some cases not legally. I'd merely like to think that upcoming helo pilots would use the same caution when considering it as I was taught to.
NL - Good stuff here Rufus. I hope upcoming pilots know why downwind ops are bad, and when they should do them, if ever, and also by knowing why, they seek helos with fewer limits, fewer problems and more safety yet. If you think the limits of your helo are the limits of every helo, you are mistaken, and you are also likely to never improve your operations. Recall in the thread that many helicopter operations worldwide can be done downwind, and night, in freezing rain.
>>>I've only been flying 12yrs, a tiny amount compared to some, but in that time I've yet to have to do a downwind departure or approach. Play nicely & Fly Safely
NL - Rufus, clearly, you are doing things well!!
Let me say for myself, I will not advocate violating procedures. But I do advocate understanding them. The purpose of this thread is to open all eyes to the real limits, and create understanding.
The enemy to safety is ignorance, which is fostered by BOTH not knowing the procedure, and by not knowing WHY the procedure does what it does.
Almost all the time, Downwind bad, upwind good - repeat after me.
Roofus says (see >>> ):
>>>Nick Are we calling Helipad profiles Towering? Towering to me means vertical. Helipad profiles are not vertical.
NL -- Nope, "helipad" procedures (I never have called them that, but have at it) are Cat A/Group A procedures. Many helos have towering takeoff procedures that are Cat A. We have one for the C+ or B that allows nearly vertical to 140 feet. I believe similar procedures exist for Bells and EU's as well. In Black Hawk, I have helped make procedures that allow towering takeoffs to 175 feet with single engine capability all along the takeoff.
>>>IAW the ANO any aircraft flying whilst carry pax must conform to Performance Profiles as laid down in the Flight Manual.
NL - Nope, that is not entirely correct. If the operation is part 91 (Private) in the states, the procedure need not be a full Cat A/Group A one, regardless of the number of pax. If for hire (Commercial) it usually requires same, but may be Cat B, where only a safe landing must be assured after failure, even with 6 engines.
>>>Yep...they restrict you. Yep...they ensure single engine climb...um...that's exactly the
point! That is why they are there!
NL - Yep, and some can allow towering procedures, too.
>>>To say not to use the published profiles to allow you flexibility, is shocking! (fingers crossed I misread that!)Professional pilots have a responsibility to those they carry. As such the published profiles must be used...thus giving the greatest chance of a safe conclusion to any'mishap'. To use commercial pressures as justification for going against the aircraft Flight Manual is equally shocking!
NL - You speak of "the Flight Manual" as if there is one procedure, brought down from Moses, and if you ever even think of another, you will be struck down. Gimme a break, there are at least 6 take off procedures for the S-76 family, I helped develop three of them myself. They are remarkably different, and are each designed to help maintain the safety you seek. Some are towering, and if an operator ever wanted one downwind, they can be qualified downwind!!
Of those procedures, none are legally "required" of a private operator.
>>>I stand by my earlier statements. If you're considering downwind approaches or T/Os ask WHY??? Look for an alternative....or use the statement 'I can't get in there' So...I also stick by my earlier statement.... I fly Police & will only consider a downwind approach & T/O if it is Life or Death & I have no other alternative.
NL-- The operative words in the above are "I can't get in there" If you really need to, it is incombant on the professional to figure out how, safely. This is a technical discussion, and there are technical means to achieve almost any point of performance you need. If you say No often enough, someone else will come along just a bit more open minded, and will buy a helicopter with a bit more performance or control, and will say "Yes, I can do it" and he will fly past your house every day, doing your job. Keep on believing that downwind operations are never possible, just don't think that is fact.
>>>Yes helicopters can take off & land downwind, yes instructors teach you these techniques, NO they shouldn't be taken lightly. I'm not saying they can't be done...they can But not as safely as into wind & in some cases not legally. I'd merely like to think that upcoming helo pilots would use the same caution when considering it as I was taught to.
NL - Good stuff here Rufus. I hope upcoming pilots know why downwind ops are bad, and when they should do them, if ever, and also by knowing why, they seek helos with fewer limits, fewer problems and more safety yet. If you think the limits of your helo are the limits of every helo, you are mistaken, and you are also likely to never improve your operations. Recall in the thread that many helicopter operations worldwide can be done downwind, and night, in freezing rain.
>>>I've only been flying 12yrs, a tiny amount compared to some, but in that time I've yet to have to do a downwind departure or approach. Play nicely & Fly Safely
NL - Rufus, clearly, you are doing things well!!
Let me say for myself, I will not advocate violating procedures. But I do advocate understanding them. The purpose of this thread is to open all eyes to the real limits, and create understanding.
The enemy to safety is ignorance, which is fostered by BOTH not knowing the procedure, and by not knowing WHY the procedure does what it does.
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Lama Bear,
You make a good point! If the 0 airspeed point is high above the ground, it will call for a bit less than OGE power (because the approach is descending, which needs less power than a stable hover). I over looked this issue.
I believe most VFR approaches are done with a decel at about 2 knots per second decel (about 4 to 5 degrees nose up from steady flight), so the 0 knot point in a 5 knot down wind is only crossed in the last 2 seconds of the approach, probably not a big deal. At 15 knots of downwind, the 0 is crosses at t minus 7 seconds, which is about 95 feet prior to the helipad. At a 6 degree approach angle (about average for VFR) that would be at a less than 10 feet above the hover height.
So I believe the extra height for the 0 knot point would be about 12 feet above the ground, so the power would be somewhat greater to allow for the extra skid height (12 vs 2 feet).
Thanks, Lama Bear!
[ 08 September 2001: Message edited by: Nick Lappos ]
You make a good point! If the 0 airspeed point is high above the ground, it will call for a bit less than OGE power (because the approach is descending, which needs less power than a stable hover). I over looked this issue.
I believe most VFR approaches are done with a decel at about 2 knots per second decel (about 4 to 5 degrees nose up from steady flight), so the 0 knot point in a 5 knot down wind is only crossed in the last 2 seconds of the approach, probably not a big deal. At 15 knots of downwind, the 0 is crosses at t minus 7 seconds, which is about 95 feet prior to the helipad. At a 6 degree approach angle (about average for VFR) that would be at a less than 10 feet above the hover height.
So I believe the extra height for the 0 knot point would be about 12 feet above the ground, so the power would be somewhat greater to allow for the extra skid height (12 vs 2 feet).
Thanks, Lama Bear!
[ 08 September 2001: Message edited by: Nick Lappos ]
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Nick, when you say downwind approaches use no more power than zero wind approaches, are you comparing a shallowed, extended downwind approach to a normal zero wind approach?
Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
Final question, after all this discussion about downwind operations, I looked at the H/V charts and noticed that they go down to zero airspeed, not negative ones. Is this common? Why (not)?
Thanks,
Matthew.
Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
Final question, after all this discussion about downwind operations, I looked at the H/V charts and noticed that they go down to zero airspeed, not negative ones. Is this common? Why (not)?
Thanks,
Matthew.
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Heedm said (see >>> ),
>>>Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
NL - My belief is that the momentary peak power is determined at the 0 knot point. Your way of looking at the power relationship defines the total energy (power times time) which probably would be greater in the downwind approach, since the aircraft spends more seconds at higher power during the approach.
>>>Final question, after all this discussion about downwind operations, I looked at the H/V charts and noticed that they go down to zero airspeed, not negative ones. Is this common? Why (not)?
NL - That is what I like about this forum. I would never think of all the permutations to the issue, like this one. We do H/V because the FAA/CAA make us do it. I have never seen an H/V chart with data lower than 0 knots.
The H/V curve is marginally useful for performance planning, almost useless for limit determination (THAT should get this thread going at Mach 1!!) and generally dangerous to test.
We do the curve because FAR says we have to, and nobody asks that we do some from rearward flight. I guess that's why, but it sounds lame. I do know that if we promulgated a takeoff or landing procedure that expressly stated a downwind capability, we would have to substantiate that capability with some engine cuts along the way.
What would happen if you were flying at 0 kts ground speed and 15 knots downwind airspeed at hover skid height and a (the) engine quit? Assuming the helo had good basic handling there (a big assumption, I can see, based on the Robbie report earlier in this thread!) the cut and landing would actually be easier than if done in still air. If the aircraft were in rearward flight at 15 knots in still air (the same aerodynamic situation, but vastly different on touchdown) the problem would be the tendency to ground loop as the mains touched.
>>>Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
NL - My belief is that the momentary peak power is determined at the 0 knot point. Your way of looking at the power relationship defines the total energy (power times time) which probably would be greater in the downwind approach, since the aircraft spends more seconds at higher power during the approach.
>>>Final question, after all this discussion about downwind operations, I looked at the H/V charts and noticed that they go down to zero airspeed, not negative ones. Is this common? Why (not)?
NL - That is what I like about this forum. I would never think of all the permutations to the issue, like this one. We do H/V because the FAA/CAA make us do it. I have never seen an H/V chart with data lower than 0 knots.
The H/V curve is marginally useful for performance planning, almost useless for limit determination (THAT should get this thread going at Mach 1!!) and generally dangerous to test.
We do the curve because FAR says we have to, and nobody asks that we do some from rearward flight. I guess that's why, but it sounds lame. I do know that if we promulgated a takeoff or landing procedure that expressly stated a downwind capability, we would have to substantiate that capability with some engine cuts along the way.
What would happen if you were flying at 0 kts ground speed and 15 knots downwind airspeed at hover skid height and a (the) engine quit? Assuming the helo had good basic handling there (a big assumption, I can see, based on the Robbie report earlier in this thread!) the cut and landing would actually be easier than if done in still air. If the aircraft were in rearward flight at 15 knots in still air (the same aerodynamic situation, but vastly different on touchdown) the problem would be the tendency to ground loop as the mains touched.
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Towering Profiles that allow for a safe reject! Excellent, I learn something new every day!
Sorry NL obviously didn't make myself clear. I wasn't talking about Private Flights. I was talking about Commercial Ops, upon which were sat fare paying members of the public. Incidently I was talking UK ops aswell. Sorry to say I've never flown in the states so wouldn't dream of commenting on US ops.
The Aircraft Flight Manual is the Aircraft 'Bible'. Absolutely agree that they contain more than one procedure. To my, obviously slow, mind they are laid down in it for a good reason, just like the engine limits & flight envelope. I wasn't directing my comments at aviation experts like yourself but more at the upcoming pilot as I felt some of the earlier threads all too easily 'ignored' the profiles & procedures laid down within it's pages.
Again...absolutely agree with you about Private operators. They are not as restricted as commercial operations. Which, in some cases, is a shame as I've been to three of their 'landings' in the last 12 months. One of which was an R-44 after a downwind approach to a confined landing site. (Aircraft CAT5, thankfully no injuries)
I also absolutely agree with you about more capable aircraft & only wish that everyone could have one! (I think we might be getting one in the not too distant future! Fingers Crossed!) However whatever the aircraft 'Caution' is the operative word.
As for your reference to my ability & flexibility, with the result being someone else flying past my house doing my job.
No-one has complained yet! & I really have no wish to get into a personal slanging match. My company clearly doesn't mind as I'm a Line Training Captain & the Flight Safety Officer.
I've also never said that downwind approaches & T/Os can't physically be done. I've merely advised extreme caution when looking to do them. A point I believe we've finally all agreed on. I've always found an alternative that I believe as the pilot to be safer. & lets be honest some aircraft just ain't as capable as others (particularly when loaded with all the toys relevant to the job in hand)
I've read this thread with interest & learnt alot. Obviously my input isn't welcome, a shame as surely none of us know it all & all of us can learn from each other.
NL yes you touched a nerve.
I try to operate with the largest safety margins I can manage.... I believe that is my responsibility as a pilot.
Sorry NL obviously didn't make myself clear. I wasn't talking about Private Flights. I was talking about Commercial Ops, upon which were sat fare paying members of the public. Incidently I was talking UK ops aswell. Sorry to say I've never flown in the states so wouldn't dream of commenting on US ops.
The Aircraft Flight Manual is the Aircraft 'Bible'. Absolutely agree that they contain more than one procedure. To my, obviously slow, mind they are laid down in it for a good reason, just like the engine limits & flight envelope. I wasn't directing my comments at aviation experts like yourself but more at the upcoming pilot as I felt some of the earlier threads all too easily 'ignored' the profiles & procedures laid down within it's pages.
Again...absolutely agree with you about Private operators. They are not as restricted as commercial operations. Which, in some cases, is a shame as I've been to three of their 'landings' in the last 12 months. One of which was an R-44 after a downwind approach to a confined landing site. (Aircraft CAT5, thankfully no injuries)
I also absolutely agree with you about more capable aircraft & only wish that everyone could have one! (I think we might be getting one in the not too distant future! Fingers Crossed!) However whatever the aircraft 'Caution' is the operative word.
As for your reference to my ability & flexibility, with the result being someone else flying past my house doing my job.
No-one has complained yet! & I really have no wish to get into a personal slanging match. My company clearly doesn't mind as I'm a Line Training Captain & the Flight Safety Officer. I've also never said that downwind approaches & T/Os can't physically be done. I've merely advised extreme caution when looking to do them. A point I believe we've finally all agreed on. I've always found an alternative that I believe as the pilot to be safer. & lets be honest some aircraft just ain't as capable as others (particularly when loaded with all the toys relevant to the job in hand)
I've read this thread with interest & learnt alot. Obviously my input isn't welcome, a shame as surely none of us know it all & all of us can learn from each other.
NL yes you touched a nerve.
I try to operate with the largest safety margins I can manage.... I believe that is my responsibility as a pilot.
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heedm
you said:Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
but you should photo copy the h\v diagram and put them back to back. now it reads hight and +&- velocity (not 100% safe)
from 0 to -15 would use less power
you said:Looking at the total drag curve, the power required for level flight (or constant vertical deceleration) increases as your airspeed slows below min drag airspeed. This makes me think that in a level deceleration you would use more power to decelerate from 50 to -15 knots than from 65 to 0 knots.
but you should photo copy the h\v diagram and put them back to back. now it reads hight and +&- velocity (not 100% safe)
from 0 to -15 would use less power
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Roofus,
Didn't want to touch a nerve, but I did want to get the juices (and creativity) flowing. The issue is that we do both agree, and all I want to do is to get us all to agree on what are the differences between fundamentals that are immutable, and those that are variable between types of helos, operations, etc.
A danger all of us face is when we believe that there is an infallibility associated with our procedures. They must be followed, they are the best we have (right now) but they can be adapted and changed, with the proper technical and regulatory help. They are also not optimal, and they are not the bible.
Should anyone want to change them, because there is something else thay want to do, I strongly recommend that a quick call or email to the manufacturer might work wonders.
A US operator had an S-76 at an outlying airfield with a dead engine (and a good one, too). He asked for a letter from us to allow single engine ferry, we responded with the weights and a brief sketch of the procedures by fax, he ammended his ops manual for a one time flight, faxed it to the local FAA office, and launched the flight in about 3 hours. Try changing the bible that fast!
I really like this forum, it gives us all a chance to talk! While we can disagree, I also feel that each has a legitimate point of view, well worth discussing and defending.
Throughout my career, I have tried to know why we do something, and I strongly urge the new folks to ask "why" always. Memorizing a group of rules and procedures is the first step to knowledge, but it is not really knowledge by itself. No rule is immutable (Law of Gravity graciously excepted!) and no rule is sacred.
Recall that the DC-10 in Chicago that lost an engine was climbing at 2000 fpm when the captain took out his checklist, slowed to Vy, lost control and killed a planeful. Air Florida hit a bridge rather than go above max EPR. Procedures must be understood in as much detail as possible, and then followed as closely as possible, improved as often as possible, and violated when necessary.
One weakness of this forum is that we are speaking to a vast group with experience levels. All you have posted is correct, considering who you are trying to reach, and I certainly respect that.
[ 09 September 2001: Message edited by: Nick Lappos ]
Didn't want to touch a nerve, but I did want to get the juices (and creativity) flowing. The issue is that we do both agree, and all I want to do is to get us all to agree on what are the differences between fundamentals that are immutable, and those that are variable between types of helos, operations, etc.
A danger all of us face is when we believe that there is an infallibility associated with our procedures. They must be followed, they are the best we have (right now) but they can be adapted and changed, with the proper technical and regulatory help. They are also not optimal, and they are not the bible.
Should anyone want to change them, because there is something else thay want to do, I strongly recommend that a quick call or email to the manufacturer might work wonders.
A US operator had an S-76 at an outlying airfield with a dead engine (and a good one, too). He asked for a letter from us to allow single engine ferry, we responded with the weights and a brief sketch of the procedures by fax, he ammended his ops manual for a one time flight, faxed it to the local FAA office, and launched the flight in about 3 hours. Try changing the bible that fast!
I really like this forum, it gives us all a chance to talk! While we can disagree, I also feel that each has a legitimate point of view, well worth discussing and defending.
Throughout my career, I have tried to know why we do something, and I strongly urge the new folks to ask "why" always. Memorizing a group of rules and procedures is the first step to knowledge, but it is not really knowledge by itself. No rule is immutable (Law of Gravity graciously excepted!) and no rule is sacred.
Recall that the DC-10 in Chicago that lost an engine was climbing at 2000 fpm when the captain took out his checklist, slowed to Vy, lost control and killed a planeful. Air Florida hit a bridge rather than go above max EPR. Procedures must be understood in as much detail as possible, and then followed as closely as possible, improved as often as possible, and violated when necessary.
One weakness of this forum is that we are speaking to a vast group with experience levels. All you have posted is correct, considering who you are trying to reach, and I certainly respect that.
[ 09 September 2001: Message edited by: Nick Lappos ]
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Rufus,
Your input here is always welcome and is just as important as anyone else's. Please continue to weigh in anytime you can...that is the beauty of this website.....it is a means to draw together pilots from all over the world. We may not always agree...but then whenever did two helicopter pilots agree upon anything?
We just got to remember that just because our position is not universially accepted or applauded, it does not mean we are not welcome.
Your kipper comment reminds me of ordering a fellow captain an 0430 wake up, kippers and warm milk breakfast, with a Guardian newspaper, after he had scarfed 19 pints of the foaming ale and the second ugliest woman in the bar...I had the ugliest ! He never did forgive me...seems he fancied the gal I was with I think?
Your input here is always welcome and is just as important as anyone else's. Please continue to weigh in anytime you can...that is the beauty of this website.....it is a means to draw together pilots from all over the world. We may not always agree...but then whenever did two helicopter pilots agree upon anything?
We just got to remember that just because our position is not universially accepted or applauded, it does not mean we are not welcome.
Your kipper comment reminds me of ordering a fellow captain an 0430 wake up, kippers and warm milk breakfast, with a Guardian newspaper, after he had scarfed 19 pints of the foaming ale and the second ugliest woman in the bar...I had the ugliest ! He never did forgive me...seems he fancied the gal I was with I think?
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Well said Nick! I completely agree with you, it's just that here in the UK the prevailing attitude is often - It was good enough for Nelson at Trafalgar, it will be good enough for you! One day attitudes will change - one day!
As for taking off downwind, as a UK police pilot it is often the quickest way to the job, but when departing downwind, I have a long,long taxi way, then open fields gently sloping down hill should the worst happen. Landing off airport? Make your approach downwind then turn into wind at about LDP.
Indecision is the key to flexibility!
As for taking off downwind, as a UK police pilot it is often the quickest way to the job, but when departing downwind, I have a long,long taxi way, then open fields gently sloping down hill should the worst happen. Landing off airport? Make your approach downwind then turn into wind at about LDP.
Indecision is the key to flexibility!
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Semi-rigid rotor,
Better get back into step young man! Word of your disloyalty shall get you into trouble with the thought police within the establishment!
You should have been around for the discussion when I had the sheer effrontery to suggest that GPS would be an effective, cheap improvement over the MK I unaided visual viewing device for navigation in Nigeria during the dusty season and height of rainy season. You cannot believe the rabid frothing that ensued when I suggested that a device installed and maintained by the Yank DOD might ever be of any possible use in civilian aircraft much less acceptable to any system based upon the UK system.
Well.....as history now shows...and only after the Nigerian CAA made the installation mandatory, did my company acquire the GPS receivers we now use and love so much. They even said they would install them to meet the legal requirement but when they went U/S then that would be that!
I am not making this up....such enlightened attitudes as that can only be a barrier to progress... but we all know tradition should not be impeded by progress.
Better get back into step young man! Word of your disloyalty shall get you into trouble with the thought police within the establishment!
You should have been around for the discussion when I had the sheer effrontery to suggest that GPS would be an effective, cheap improvement over the MK I unaided visual viewing device for navigation in Nigeria during the dusty season and height of rainy season. You cannot believe the rabid frothing that ensued when I suggested that a device installed and maintained by the Yank DOD might ever be of any possible use in civilian aircraft much less acceptable to any system based upon the UK system.
Well.....as history now shows...and only after the Nigerian CAA made the installation mandatory, did my company acquire the GPS receivers we now use and love so much. They even said they would install them to meet the legal requirement but when they went U/S then that would be that!
I am not making this up....such enlightened attitudes as that can only be a barrier to progress... but we all know tradition should not be impeded by progress.
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Fellow Ppruners,
I am so glad that I asked the question at the head of this thread, at first I did think all you "pro pilots" would have a right go at me, but I am awash with information that would take me years to learn.
Hey Roofus, just because some comments dont fit your mindset, dont be angered, we all have opinions, what is wrong to one person may be "possibly wrong" to you and vice versa, dont ever close your mind to opinions, that is just what they are, after all, what you say makes a lot of sense to me, and remembering what you and the others have said, may one day stop me doing something that would be regretable!
I am so glad that I asked the question at the head of this thread, at first I did think all you "pro pilots" would have a right go at me, but I am awash with information that would take me years to learn.
Hey Roofus, just because some comments dont fit your mindset, dont be angered, we all have opinions, what is wrong to one person may be "possibly wrong" to you and vice versa, dont ever close your mind to opinions, that is just what they are, after all, what you say makes a lot of sense to me, and remembering what you and the others have said, may one day stop me doing something that would be regretable!
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Vorticey, you are correct, the power required at 0kts is greater than that required at -15kts.
The average power required from 0 to -15kts is greater than the average power required from 65 to 50 kts. I compared the 65 to 0 kts range with the 50 to -15 kts range. In both the helicopter slows between 50 and 0 kts. It's the deceleration ranges that aren't common that produces the difference.
While the peak power requirement should be the same, I was considering an approach where you don't change your power setting substantially throughout the approach. If you're power limited, this is a good practice.
Matthew.
The average power required from 0 to -15kts is greater than the average power required from 65 to 50 kts. I compared the 65 to 0 kts range with the 50 to -15 kts range. In both the helicopter slows between 50 and 0 kts. It's the deceleration ranges that aren't common that produces the difference.
While the peak power requirement should be the same, I was considering an approach where you don't change your power setting substantially throughout the approach. If you're power limited, this is a good practice.
Matthew.
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Heedm,
I just got back, missed the fireworks.
Your point about being power limited and how to work with that is well taken and just about takes this around full circle. It's a much more critical decision gate you face in a very heavy underpowered ship then a light sporty one.
If anyone's still questioning whether a downwind t/o requires more power I would suggest the following;
Go out to a big fat runway and stabilize your aircraft at a 1 foot hover into the wind. Take your hand off the collective and slowly transition into forward flight using the smallest cyclic movements you can. Remember to not touch the collective.
Now try the same excercise downwind.
The time you spend in the interferance region is a power penalty, the longer you are in it the more you will drop. Going downwind you are in it for a longer period of time.
It's really a simple test and if you haven't flown a really heavy ship in a while it will remind you of power management in critical phases of flight.
Really good thread here,
Fly safe !
I just got back, missed the fireworks.
Your point about being power limited and how to work with that is well taken and just about takes this around full circle. It's a much more critical decision gate you face in a very heavy underpowered ship then a light sporty one.
If anyone's still questioning whether a downwind t/o requires more power I would suggest the following;
Go out to a big fat runway and stabilize your aircraft at a 1 foot hover into the wind. Take your hand off the collective and slowly transition into forward flight using the smallest cyclic movements you can. Remember to not touch the collective.
Now try the same excercise downwind.
The time you spend in the interferance region is a power penalty, the longer you are in it the more you will drop. Going downwind you are in it for a longer period of time.
It's really a simple test and if you haven't flown a really heavy ship in a while it will remind you of power management in critical phases of flight.
Really good thread here,
Fly safe !
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tgrendl,
That is a great test, but I suggest a slight modification.
Don't hold the collective set, that doesn't tell you much about power. There are big torque changes for small airspeed changes in the low speed region. Hold the aircraft off the ground with collective, and spot the max torque needed to keep the aircraft from touching during the takeoff. Now try the takeoff at the same weight in still air (at about the same DA and OAT) and compare the torque to the downwind try.
Remember, an up wind takeoff will use less power than a downwind one, but a still air takeoff will use more power than an upwind one, too. The only assertion I defended was that downwind power needs are not measurably different than still air.
[ 10 September 2001: Message edited by: Nick Lappos ]
That is a great test, but I suggest a slight modification.
Don't hold the collective set, that doesn't tell you much about power. There are big torque changes for small airspeed changes in the low speed region. Hold the aircraft off the ground with collective, and spot the max torque needed to keep the aircraft from touching during the takeoff. Now try the takeoff at the same weight in still air (at about the same DA and OAT) and compare the torque to the downwind try.
Remember, an up wind takeoff will use less power than a downwind one, but a still air takeoff will use more power than an upwind one, too. The only assertion I defended was that downwind power needs are not measurably different than still air.
[ 10 September 2001: Message edited by: Nick Lappos ]
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Nick, I'm not trying to be picky, but normally you have a choice between upwind or downwind (or some crosswind component). You rarely have a choice between downwind and still wind approach/departure paths.
I understand you were just commenting on power requirements and not the full decision process, but from a practical point of view, when you have a wind the downwind choice has the biggest power requirement of all the wind options.
I still contend that the same approach downwind uses more power. Looking forward to getting back to work so I can try.
Matthew.
I understand you were just commenting on power requirements and not the full decision process, but from a practical point of view, when you have a wind the downwind choice has the biggest power requirement of all the wind options.
I still contend that the same approach downwind uses more power. Looking forward to getting back to work so I can try.
Matthew.
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Matthew,
You are absolutely right, the choice is always upwind, crosswind or downwind, so the test is pertinent (and unnecessary!)
My response about power going downwind being equal to power in still air was related to those who advocated never going downwind. To reduce that argument to absurdium, I propose showing that downwind equals no wind, ergo never take off without a wind, and then only into it!
It is obvious that a headwind starts you off further down the power required curve, and also with a faster airspeed, steeper climb angle and easier power off landing.
You are absolutely right, the choice is always upwind, crosswind or downwind, so the test is pertinent (and unnecessary!)
My response about power going downwind being equal to power in still air was related to those who advocated never going downwind. To reduce that argument to absurdium, I propose showing that downwind equals no wind, ergo never take off without a wind, and then only into it!
It is obvious that a headwind starts you off further down the power required curve, and also with a faster airspeed, steeper climb angle and easier power off landing.
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Nick,
I believe we're after the same data but going about it in different ways.
The reason I use the "don't touch the collective" idea is that it is a very big bell going off when you're dragging your skids down the pavement. A still air departure with minimum cyclic movement (and no collective change) will still take less time to get to ETL then a downwind one. The power requirement can either be listed as how much collective you pull or how long your skids make the grrr-grrr-grrr sound.
In this case I think it's also safer doing this then trying to concentrate on a tiny gage while making the departure.
I will try your idea tommorrow as best I can,
Thanks,
I believe we're after the same data but going about it in different ways.
The reason I use the "don't touch the collective" idea is that it is a very big bell going off when you're dragging your skids down the pavement. A still air departure with minimum cyclic movement (and no collective change) will still take less time to get to ETL then a downwind one. The power requirement can either be listed as how much collective you pull or how long your skids make the grrr-grrr-grrr sound.
In this case I think it's also safer doing this then trying to concentrate on a tiny gage while making the departure.
I will try your idea tommorrow as best I can,
Thanks,
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IMHO downwind does not equate to no wind departues. My reasoning:
No wind invariably involves transition to/from a hover in ground effect with a transition at some stage to/from translational lift, therefore both effects reducing power requirements.
Downwind departure or arrival may mean the ground effect in the hover is reduced (blown away) therefore a larger power requirement. In addition as you transition you will go from negative airspeed to positive airspeed passing through a zero airspeed point. At this point you will have zero airspeed and a groundspeed of variable speeds upto 30kts therefore achieving no ground effect. Although you may be close to the ground you will recieve no help from either translationl lift of ground effect therefore effectively requiring out of ground effect power requirements.
Into wind operations provide translational lift earlier, sometimes in the hover and this exceeds that lift achieved from ground effect, which may be blown behind you, therefore further reducing power required.
Summary:
You need more power to operate down wind, you need to understand the performance of your own machine, my experience lies just with three. This is a cracking thought provoking thread, may there be more like them!
No wind invariably involves transition to/from a hover in ground effect with a transition at some stage to/from translational lift, therefore both effects reducing power requirements.
Downwind departure or arrival may mean the ground effect in the hover is reduced (blown away) therefore a larger power requirement. In addition as you transition you will go from negative airspeed to positive airspeed passing through a zero airspeed point. At this point you will have zero airspeed and a groundspeed of variable speeds upto 30kts therefore achieving no ground effect. Although you may be close to the ground you will recieve no help from either translationl lift of ground effect therefore effectively requiring out of ground effect power requirements.
Into wind operations provide translational lift earlier, sometimes in the hover and this exceeds that lift achieved from ground effect, which may be blown behind you, therefore further reducing power required.
Summary:
You need more power to operate down wind, you need to understand the performance of your own machine, my experience lies just with three. This is a cracking thought provoking thread, may there be more like them!
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With all due modesty, I have had the opportunity to fly in a variety of environments.
In all of them downwind and towering departures have come into play.
Considerations in our jobs include a/c limits and recommended procedures yes, but when the performance is there we also have to consider noise and passenger comfort and getting the job done efficiently.
Too many pilots get it in their head either that the H/V diagram in inviolable or that downwind will always kill you. Neither is true.
Sometimes the power to vertical isn't there and a downwind departure is required, the key is to know when and to know your machine.
I think a lot of this comes from a misunderstanding of the H/V diagram. I get this from the posts above. We all know that you can perform simulated engine failures in the 100' hover in a Bell 206 without much pucker. Chopping the throttle in the red of the H/V in an R22 is possible too, if your reactions are there.
Don't do these things for fun though, unless you can understand the risks, and accept them.
In all of them downwind and towering departures have come into play.
Considerations in our jobs include a/c limits and recommended procedures yes, but when the performance is there we also have to consider noise and passenger comfort and getting the job done efficiently.
Too many pilots get it in their head either that the H/V diagram in inviolable or that downwind will always kill you. Neither is true.
Sometimes the power to vertical isn't there and a downwind departure is required, the key is to know when and to know your machine.
I think a lot of this comes from a misunderstanding of the H/V diagram. I get this from the posts above. We all know that you can perform simulated engine failures in the 100' hover in a Bell 206 without much pucker. Chopping the throttle in the red of the H/V in an R22 is possible too, if your reactions are there.
Don't do these things for fun though, unless you can understand the risks, and accept them.
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Heloteacher, I think we've established that downwind takeoffs are safe enough when all factors are being considered. What is really being focused on relates to what you said, "when the performance is there".
If you're faced with a choice between a downwind takeoff or a towering departure when hot, high and heavy, how do you determine if the performance is there? Do you think downwind takeoffs and approaches use as much or more power as zero wind?
The way I understand the h/v diagram is that it's based on aircraft performance and pilot skill. LOH, Ag, longline, etc. all operate in areas that are normally red zones of the h/v diagram, but those jobs usually demand an experience level, demonstrated skill, and often extra training pertinent to the environment.
You say a 100' hover chop in a bell 206 is possible, but do you think it's possible for every brand new PPL(H)? I find that it's not an extremely difficult exercise, but it is something that needs experience or instruction that's not required even for a commercial licence.
You're right that it appears that some don't recognize the h/v diagram for what it is. It is not inviolable, it doesn't say that downwind takeoffs will kill you, but it does give you a low level/speed flight regime that has been demonstrated to be safer. Even if you have the skills to survive engine failures in any regime, the red zone of the h/v diagram is still an area for you to avoid. For safety.
Matthew.
If you're faced with a choice between a downwind takeoff or a towering departure when hot, high and heavy, how do you determine if the performance is there? Do you think downwind takeoffs and approaches use as much or more power as zero wind?
The way I understand the h/v diagram is that it's based on aircraft performance and pilot skill. LOH, Ag, longline, etc. all operate in areas that are normally red zones of the h/v diagram, but those jobs usually demand an experience level, demonstrated skill, and often extra training pertinent to the environment.
You say a 100' hover chop in a bell 206 is possible, but do you think it's possible for every brand new PPL(H)? I find that it's not an extremely difficult exercise, but it is something that needs experience or instruction that's not required even for a commercial licence.
You're right that it appears that some don't recognize the h/v diagram for what it is. It is not inviolable, it doesn't say that downwind takeoffs will kill you, but it does give you a low level/speed flight regime that has been demonstrated to be safer. Even if you have the skills to survive engine failures in any regime, the red zone of the h/v diagram is still an area for you to avoid. For safety.
Matthew.