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"Check" vs. "Pull" Collective

student auto collective

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#1 Willtim

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Posted 17 December 2012 - 15:26

Just a quick question here from a student pilot, and I'd like to apologize in advance for this somewhat stupid question: what is the difference between "check collective" and "pull collective". I figured out early on what the instructor wants when he tells me to check collective in an auto. Other than monitoring RPM and ensuring it stays in the green, does it mean anything else in terms of what I should be doing in an auto?
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#2 Flying Pig

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Posted 18 December 2012 - 14:22

Check collective means he wants you to control your RPM by increasing or decreasing collective. When things like this come up make sure you clarify as soon as your skids hit the ground. Check collective could also mean to lower it. "chek rpm" would probably be more accurate. Confusion can have deadly results in this business. Classic example of using terms without an explanation.

Edited by Flying Pig, 18 December 2012 - 14:26.

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#3 Counterrotate

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Posted 18 December 2012 - 15:23

Your instructor should brief you on exactly what to expect before every lesson, what terms will be used, and exactly what they mean. This is a common error on the instructors part. If your instructor is not doing this, ask them to.
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#4 pilot#476398

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Posted 18 December 2012 - 16:53

Don't ask questions like that here, we could have completely different interpretations as to the meaning of such an abstract term!

Clarify terminology with your instructor,...before you both get killed over miscommunication!

Edited by pilot#476398, 18 December 2012 - 16:54.

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#5 Flying Pig

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Posted 18 December 2012 - 20:40

Don't ask questions like that here, we could have completely different interpretations as to the meaning of such an abstract term!

Clarify terminology with your instructor,...before you both get killed over miscommunication!


^^^^^Actually.... forget what I said.... do what he says
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#6 Pohi

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Posted 21 December 2012 - 12:44

Don't ask questions like that here, we could have completely different interpretations as to the meaning of such an abstract term!

Clarify terminology with your instructor,...before you both get killed over miscommunication!


Good lord, are you kidding?

If people shouldn't ask questions that can have different meanings, then there would be no questions asked here.

People here couldn't agree on what day of the week it is even if they were all in the same room at the same time.

Furthermore, if a student moving a control in the wrong direction is going to get student and instructor killed, then the instructor is a horrible instructor.
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#7 R22139RJ

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Posted 21 December 2012 - 15:18

Pohi, watch out for the question Nazi

YOU MAY GET DIFFERENT OPINIONS!

Spray it Right, Spray it Tight

#8 iChris

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Posted 21 December 2012 - 15:22

Just a quick question here from a student pilot, and I'd like to apologize in advance for this somewhat stupid question: what is the difference between "check collective" and "pull collective". I figured out early on what the instructor wants when he tells me to check collective in an auto. I assume that checking collective is just pulling the collective a little bit, but does it mean anything else in terms of what I should be doing in an auto?



By all means, if you’re unsure of your instructor’s terminology, ask for direct clarification.

In general (there is such a term used), “Collective Check” is a term that relates to an old autorotation technique. It’s used to help level the helicopter following the completion of the flare just prior to landing. This technique is also effective in leveling the helicopter during the completion of a Quick Stop.

In both situations, the helicopter must make the change from a nose-up, deceleration attitude to a level attitude for landing. Conventional wisdom says this is done solely with cyclic. However, cyclic may not be the best control to lead with to level many helicopters.

The reason is the cyclic is only tilting the thrust vector generated by the main rotor. If you pushover with cyclic only, you’re decreasing the angle of attack of the rotor, which is already nearly flat pitched, along with a decreasing thrust vector. The end result is very sluggish responds in the leveling of the helicopter.

However, if you lead with a little up collective, “Collective Check”, followed by cyclic, you’re directly increasing the thrust vector which the cyclic is tilting. The thrust due to the collective increase results in a smoother more rapid leveling.

This works well with semi-rigid rotor systems like the R22 were the CG normally falls forward of the rotor centerline. Remember, with semi-rigid rotor systems, control moments are a by-product of rotor thrust. This means that if a control force or moment is needed to change direction or fuselage attitude, the rotor system must first develop thrust. If you increase the thrust you increase the control force and control moment.

By the way, who’s teaching you things like “Collective Check”? This is one of many secret techniques that were never to be revealed to the general helicopter pilot, outside of elite circles. Or did you or your instructor just stumble over this term by accident?

However, if you're talking about "Check Collective" go with the above post. That term is more a request for action on your part, not any technique.

Edited by iChris, 21 December 2012 - 17:33.

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Regards,

Chris

#9 Spike

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Posted 21 December 2012 - 16:22

The circles for which I travel(ed), “check collective” simply means to control RPM. Normally stated while turning during the auto. In the flare, “initial”, “initial pitch”, “initial pull” or “initial pitch pull” is the term used for the aerodynamic breaking to reduce the machines forward momentum…..

Additionally, at your operation, if simple terminology is the difference between life and death, I suggest you “remain clear” of helicopters….

#10 PondJumper

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Posted 31 December 2012 - 21:54

Communication. This is a question that could be answered differently by many guys in this forum. You do need to ask your instructor what he means by ANY terminology if there is ever any doubt, even if it is a few flights later. Don't let any doubt fall into the 'assumption' category. Don't be affraid of looking like a duffus. If you don't know EXACTLY.... ask, and make sure you have a very clear understanding.

I made this mistake (which will never be repeated) a short while back. My instructor at times during non demanding flight operations will take controls and overide my inputs without using the proper hand off terminology. This happened a couple of weeks ago, and at the end of my instructor's input I assumed he would hand off the controls to me using the designated terminology. He did not, and for almost 2 seconds, we both assumed the other was controlling the a/c. Never again. That situation cured me of making assumptions and being hesitant to get full clarification on exactly what is going on in the crew station, and what is expected.

We were both very lucky.

Point is, "check" could mean more than one thing, find out exactly what your instructor means by it.

#11 aeroscout

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Posted 31 December 2012 - 23:33

Good lord, are you kidding?

If people shouldn't ask questions that can have different meanings, then there would be no questions asked here.

People here couldn't agree on what day of the week it is even if they were all in the same room at the same time.

Furthermore, if a student moving a control in the wrong direction is going to get student and instructor killed, then the instructor is a horrible instructor.


I liked your post so much I had to quote it in addition to liking it.
You are right about not agreeing about the day of the week. As for myself, I'm just across the international date line, so that should stir things up.
This thread has you and almost all the other replies talking about good communication. The thought that came to my mind that is a good example of communication is when I was flying ejections seat equipped aircraft, we were admonished to never use the "E" word in flight unless you meant to call for an immediate ejection. For example..."We have a fire light, but don't eject yet...guess what is likely to happen and has happened in similar cases ? Another example...On tower radio a call is heard "A-4 in the pattern you are on fire...EJECT ! Guess what happens if there is more than 1 A-4 in the pattern ?

#12 pilot#476398

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Posted 01 January 2013 - 01:42

Good lord, are you kidding?

If people shouldn't ask questions that can have different meanings, then there would be no questions asked here.

People here couldn't agree on what day of the week it is even if they were all in the same room at the same time.

Furthermore, if a student moving a control in the wrong direction is going to get student and instructor killed, then the instructor is a horrible instructor.


We're talking about the meaning of an obscure term his instructor uses when he wants his students to make a particular control input during an auto,...not "which is the better helicopter for training", or "why does the nose pitch up slightly when I do this"!

If someone this kid trusts here tells him it means to raise the collective, when his instructor intends it to mean the opposite, then yeah, it could get them killed!

...and there are plenty of horrible instructors out there!

My point is that internet forums are not the place to go for IMPORTANT advice! Ask people you ACTUALLY know and trust, not a handful of strangers!

Question Nazi,...give me a break! :rolleyes:

#13 Counterrotate

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Posted 01 January 2013 - 02:11

Stranger things have happened. People get killed over miscommunication every day.

#14 d10

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Posted 01 January 2013 - 02:51

Furthermore, if a student moving a control in the wrong direction is going to get student and instructor killed, then the instructor is a horrible instructor.


This is just one small example of a mistake caused by miscommunication. The bigger issue is the attitude that you don't need to bother clarifying something so minor.

I've encountered hundreds of situations where communication with other crewmembers or ATC was ambiguous or unclear. Maybe one or two on every flight that would seem just as minor as what checking collective meant. In any single instance I could assume with high accuracy what was meant, and the consequences of being wrong were unlikely to result in much. Add all of those situations up though, and I would have been wrong quite a few times, and the chances of just one of those mistakes leading to a violation or accident is higher than I'd like it to be.

The way I see it, clarifying misunderstandings in communication takes such little effort, and the worst that can happen is you confirm your assumptions and build yourself a reputation as a professional pilot who pays attention to detail. What do you have to lose?
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#15 Pohi

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Posted 01 January 2013 - 10:52

IMHO, there are no taboo questions that can be asked on the forums. If somebody asks a stupid question, they will probably catch a lot of crap from members here. Heck, people catch a lot of crap for asking good questions.

If one person is confused and asks a question, perhaps it will answer the same question that a different confused person was afraid to ask. Or, maybe an instructor or two might read and realize that they are using nonstandard terminology to their students and choose to change their methods.

Either way, if confused about a term, yes.. The student should clarify with their own instructor. That instructor could be wanting something that nobody on the planet could imagine but the instructor alone. But also asking on the forum isn't a bad thing.

As far as the last part of my earlier post... If an instructor hasn't had a student try to grab an armpit full of collective while starting a nose dive in an auto, they probably will in the future. Students do wonderful and crazy things that give instructors a new appreciation for life from time to time, that's what makes instructing interesting. But, if a person is concerned that a wrong input is going to kill them, they might want to work for flight safety. That way, the worst thing that can happen is the red screen of death.

I used to joke with my students after they did something silly that there are two jobs going on while we are flying. Their job is to try and kill us, my job is to not let them. Hopefully, at the end of the day, I'm better at my job than they are at theirs.
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