300 CB - Correlator Conumdrum

[joker]

OK, just because I'm a little bored, here's a question for new 300CB pilots.

 

Aircraft is on the ground. Engine stopped.

 

You raise the collective allowing the throttle grip to move freely.

 

Which way does the throttle grip turn as you raise the collective?

1) In the same direction as rolling on the throttle when you are in flight?

 

2) In the same direction as rolling off the throttle when you are in flight?

 

Joker

[Jocko]

OK, just because I'm a little bored, here's a question for new 300CB pilots.

 

Aircraft is on the ground. Engine stopped.

 

You raise the collective allowing the throttle grip to move freely.

 

Which way does the throttle grip turn as you raise the collective?

1) In the same direction as rolling on the throttle when you are in flight?

 

2) In the same direction as rolling off the throttle when you are in flight?

 

Joker

ok I'm gonna take a stab at this even though I have zero hours of flight time in any bird.

 

Using the thought process that when you use more collective you also need more throttle for power it would make since that it would roll in the direction of more.

 

BUT..... <_ .i have a sneaky suspicion that if the answer were easy you would not be asking it so......>

 

I'm gonna take a guess that when you pull up on the collective the correlator automatically adds more throttle thus making the throttle turn in the direction of less when done manually.

 

and thats my final answer

How'd I do???

 

rock on

[Guest pokey]

i'de say yer dangerously close Jocko, but since this is Joker's question i will just add a few things to it.

 

1) NEVER pull the collective up (w/ a collective actuated hobbs meter) w/ the master on & then go home ! (you cannot legally log that 12 hours on the meter! ) we did that once during maintenance & had a heck of a time trying to convince lease-back/owner how it happened !

 

2) i have more than 40 hours & that was the requirement

 

3) what are the rivets for on the top of the "up-collective" stop for?

[67november]

3) what are the rivets for on the top of the "up-collective" stop for?

 

for people like us to replace when they start smoking

 

(don't know not been in a 300 close enuf to see them )

Edited November 14, 2006 by 67november

[FordMustang0288]

I'm just at about 10 hours in the 300CB.

 

When you raise the collective, it rolls on the throttle same as if you were doing it in flight & visa versa. I'm still pretty tense on that collective/throttle & rarely notice it...so I had to stop and think. lol

 

...i hope thats right anyway...

 

im gonna have to make a mental note tomorrow when i jump in

 

sorry for the post below me...i dont know how to delete it.

[FordMustang0288]

I'm just at about 10 hours in the 300CB.

 

When you raise the collective, it rolls on the throttle same as if you were doing it in flight & visa versa. I'm still pretty tense on that collective/throttle & rarely notice it...so I had to stop and think. lol

[C of G]

OK, just because I'm a little bored, here's a question for new 300CB pilots.

 

Aircraft is on the ground. Engine stopped.

 

You raise the collective allowing the throttle grip to move freely.

 

Which way does the throttle grip turn as you raise the collective?

1) In the same direction as rolling on the throttle when you are in flight?

 

2) In the same direction as rolling off the throttle when you are in flight?

 

Joker

 

 

I always enjoyed this question, Joker. Limiting it to <40 hour pilots might not be fair, as I have often gotten suprised reactions from CFI candidates as well. A funny bit is I was just explaining this to a potential ATP pilot who hasn't flown a CB before and was concerned about the lack of govenor.

 

If I may give a hint: Without restricting the throttle, what action is occuring at the throttle butterfly as you raise the collective?

[joker]

CofG,

 

I know this is one of your pet favourites! You gave it to me, once upon a time! Good to hear from you.

 

Jocko, you remind me of the Sicilian called Vizzini in the film The Princess Bride!

 

I have a sneaky suspicion that if the answer were that easy you would not be asking it so......

 

Remember, don't fall victim to one of the classic blunders. The most famous is "Never get involved in a land war in Asia." But only slightly less well known is this: "Never go in against a Sicilian when death is on the line."

 

Anyway, Jocko, your reasoning is correct - in so far as there is more to this question than meets the eye.

 

So as FordMustang and others go off and try this with their instructors (we would be interested to hear your reports), I open the question to the floor....

 

Joker

[flingwing206]

It's pretty simple, really...

[Jocko]

It's pretty simple, really...

 

 

OOOHHHH!!!

 

Well that explains everything

[Guest pokey]

oh BOY !! pitchers !

 

ya see that "thingy" all the way to the left of the picture?--THAT's where yer throttle cable hooks on. Now when ya pull up on the collective?--that "thingy" rotates and pulls on the throttle cable, opening the throttle. That "thingy" is also connected via a shaft and a 90 degree gearset to the throttle twistgrip (#21) (BTW, tube #24 connects the pilot & co-pilot twistgrips) (ALSO, that vertical spring assy is just to "lighten" the collective in flight)

 

Now as to what the twistgrip is dong in Joker's scenerio?---it all depends on the friction in the system, ie throttle cable & associated bearings. IF the cable is well oiled and the carburetor/fuel servo is giving no resistance to the system?----the twistgrip will not rotate. Have someone physically hold the throttle arm on the servo?--the twistgrip will rotate in direction that will be "simulating" rolling the power off.

 

The correlator on the 300's (if set up properly) is excellent ! I have flown some that once in a hover, lock the throttle friction & ya can fly ALL day ( well depending on fuel on board) w/ out having to adjust throttle. (ok, i exaggerated a bit ) but its "almost" as good as a governor.

 

And as far as the rivets? NO 67 ( i quit smoking them long ago)

[joker]

Pokey,

 

Nice explanation! I was worried that I would have to explain it! You saved me a lot of bother.

 

Thanks Fing too, for the diagram!

 

IF the cable is well oiled and the carburetor/fuel servo is giving no resistance to the system?----the twistgrip will not rotate.

Is this a design objective or were you talking theoretically? I understand what you're saying, but I have never found a machine that has acheived this! To that end, I thought the roll was 'normal' and infact, desireable. In one respect, it forces a manual 'engagement' of the correlator system (by either hand or 'throttle-friction control').

 

If it is indeed a quirk, then it is a useful one, as it is this which allows you to raise the collective without there being a change in throttle valvue position (if you wanted). In effect, you are able to disengage the correlator, if you let the twistgrip roll freely. i.e. when at flat pitch, just about to pick up, you raise collective, but let the twistgrip roll freely until blade pitch starts to droop the ERPM.

 

Schweizer must agree that some friction in the system is inevitable - hence the need for the 'throttle friction control' - which is required to oppose the friction in the cables / carburettor etc..etc..

 

You are completely right though...the correlator works really well in this aircraft. Just to expand on what Pokey says about not having to adjust the throttle:

 

**Consider your grip on the collective / throttle grip. The best way I found was to use only the thumb and the forefinger on the throttle-grip or throttle friction. The rest of the fingers are curled under the 'shaft' of the collective. The hand can be slid up and down the shaft to enable manipulation of the throttle friction, or the throttle grip, or collective friction as required. With everything set up properly, only a light touch is needed to 'tweak' the throttle when necessary.

** This applies for normal cruise flight of course. Sometimes a firmer grip will be required for a more manual maniuplation of the throttle (or even overriding) of the correlator.

 

For all the new students out there, this system does take a bit of time to get your head round. Don't worry if you don't get it first time. Just have a play (WHEN ENGINE IS OFF) when you have a couple of minutes spare whilst waiting for your instructor. Better still, talk it through with your instructor or a mechanic.

 

Thanks to others for having a go. (Jocko and Ford Mustang) Even if others did not post, I hope this thread got some readers thinking or helped in some way. As CofG said, even many experienced CFIs will have trouble with this concept, simply because they have never been shown!

 

Safe flying!

 

Joker

 

P.S.

 

Pokey,

 

w.r.t the rivets you mention, I have to admit that it is such a long time that I saw a 300 CB up close, that my memory fades. I do remember something about them sometimes causing a 'sticky' collective and needing to be refiled. Are they there simply to serve as an 'end-stop' and protect (take the wear and tear) the collective friction slide (Part 14). That's a long shot.

 

P.P.S. I can't imagine the testing and calculations that went into finding the 'mechanical' relationships between power demand, butterfly position, collective position, blade pitch and the radius of the lever on the 'thingy at the left of the diagram'. Some clever stuff methinks!

Edited November 16, 2006 by joker

[Guest pokey]

Joker,

 

The friction i noticed in the system (cable & servo/vs gears & twistgrips) is from one time when i changed a throttle cable in an older 300 that we were running, old cable----ya could "blow" on the twist grip to add power,,,,new cable?--needed help of Herman Munster ! ,,,and while i was rigging the correlator? i noticed it seemed "different" (wanted to roll throttle OFF as i pulled pitch during the rigging process).

 

I hope also that others have learned something from this post. After all? This is why we are all here --right?!

 

oh and the rivets? they act as an "up" stop for the collective during "normal" flight---but during auto's ya can over-ride them & "pull" a bit more pitch into the blades. (and NO 67, i am NOT gonna start smokin' again)

[67november]

(and NO 67, i am NOT gonna start smokin' again)

 

and neither am I (4 years and 5 months now)

 

now back to learning.

[Guest pokey]

P.S.S. I can't imagine the testing and calculations that went into finding the 'mechanical' relationships between power demand, butterfly position, collective position, blade pitch and the radius of the lever on the 'thingy at the left of the diagram'. Some clever stuff methinks!

 

especially back in the 50's !

 

them old books on Kinematics sure did "pave the way"---was one of my favorite subjects in skool two BTW----speelin' shir waznt tho,,, kantcha tell?

 

PS. i've put together many a ships (300's) & they ALL have their own "personalities" and have plenty of adjustments built into the machine to make fly "acceptable"

 

67? ya got me beat by a year & 5 months,,,,, UNLESS i can count the time 15 years ago for 5 years?

[FordMustang0288]

As we landed today. I asked my instructor this question & when he raises it...you can clearly see the throttle rolling off. which really surprised me. I guess all of you covered that pretty well today :-p

 

Btw, these questions are pretty neat. They keep us students on our feet...

[Guest pokey]

As we landed today. I asked my instructor this question & when he raises it...you can clearly see the throttle rolling off. which really surprised me. I guess all of you covered that pretty well today :-p

 

Btw, these questions are pretty neat. They keep us students on our feet...

 

mustang? take a closer look. Is the actual "throttle" (arm on the carburetor/servo) closing? OR just the twistgrip rolling off?

 

i think you will find its just the twistgrip & the throttle is still at its "idle position" (due to friction tho- you may see some movement of the throttle arm)

[FordMustang0288]

mustang? take a closer look. Is the actual "throttle" (arm on the carburetor/servo) closing? OR just the twistgrip rolling off?

 

i think you will find its just the twistgrip & the throttle is still at its "idle position" (due to friction tho- you may see some movement of the throttle arm)

 

Not sure if you can see the servo while strapped into the seat or not...but the the twistgrip was rolling off...

[Jocko]

OK, just because I'm a little bored, here's a question for new 300CB pilots.

 

Aircraft is on the ground. Engine stopped.

 

You raise the collective allowing the throttle grip to move freely.

 

Which way does the throttle grip turn as you raise the collective?

1) In the same direction as rolling on the throttle when you are in flight?

 

2) In the same direction as rolling off the throttle when you are in flight?

 

Joker

 

 

AAHHH but now let us get technical in another direction, <_ what was the original question correct me if i wrong but it wasn way does connector thingy or servomahosit move throttle grip turn. src="%7B___base_url___%7D/uploads/emoticons/default_cool.png" alt="B)">

 

I’m only trying to make a point here kids. Allot (ok not allot but some) of you guys are quick to jump on that lets split hairs and devil’s advocate train on some of the threads here (some, just maybe, a little too quick) so when in Rome…….Don’t get me wrong I understand when it comes to flying I know that a lot of hair splitting is called for. That’s what can make the difference between a good pilot and a so so pilot. I just wanted to mix up the pot so to speak. Besides us newbies need to stick one in when we get the chance after all it is all in the spirit of learning as well as having some fun (and that’s not a dig)

 

 

rock on

Edited November 16, 2006 by Jocko

[joker]

Jocko,

 

My question was indeed, "Which way does the throttle grip turn?" Thanks to those who had a go (you). I think we have sorted that out. The idea was for that question to lead into a discussion (or questioning) of the reason for that, and subsequently a better understanding of the correlator system. That's what happened... I think!

 

For some people the concept discussed above is a minor 'technicality'. It won't help them hold a hover or make the spot in an autorotation. Others will be ready (at the stage of learning) where they will question that 'anomoly'. The twistgrip appearing to roll off when you raise the collective? That had me stumped when I first saw it. So, I guess the question is targeted at those people.

 

I posed that question for a couple of reasons. Here are the main ones.

 

1) The posts on this board have become a little stale...not much helicopter talk going on just now.

 

2) I was a student. I was an instructor. Questions like these are the ones which I found interesting during my training. Questions which I asked and struggled with. Now I ask them to others in hope they help students and instructors to learn a little bit more about the aircraft they are flying.

 

I think the replys from Pokey and others are truely there for those reasons too.

 

I am sorry that you think sometimes people are 'splitting hairs'. Remember, there is one more reason why I (and I am sure others) post in these forums.

 

3) I come here to split hairs! Believe it or not, I enjoy getting to the nitty gritty of something. What is 'splitting hairs' to you is actually interesting and relevant conversation to me. By the same token, what is interesting to you may be 'splitting hairs' to a complete novice or non-pilot.

 

Although the question is posed for the beginner, the ensuing conversation can run much deeper.

 

So please don't see 'hair splitting' as an attempt to patronise.

 

Pokey's reply to FordMustang noted FM's slip in stating the 'throttle' when he meant the 'twistgirp'. This could have been a simple mistake, or it could have been a misunderstanding. Either way, Pokey chose to correct it...just in case.

 

Anyway, I hope that you enjoy reading, and contributing here. As I said, there are many here who post purely for the love of helping others.

 

Please ask your questions everyone...let's split hairs!

 

Joker

Edited November 16, 2006 by joker

[Guest pokey]

AAHHH but now let us get technical in another direction, What was the original question? Correct me if I’m wrong but it wasn’t what way does the connector thingy or servomahosit move but what way does the throttle grip turn.

 

Yes, you are right Jocko, and i agree----this question's answer should have been "either door #1 OR #2" AND, you were "dangerously close" with a correct answer/explanation. However the correlator does NOT as you stated:

" I'm gonna take a guess that when you pull up on the collective the correlator automatically adds more throttle thus making the throttle turn in the direction of less when done manually"

 

The correlator will only add more throttle IF the twistgrip is NOT allowed to turn. IF its allowed to turn, it defeats the correlator's job & rolls the twistgrip off & then no power to the engine. (the butterly stays closed)

 

This isnt an easy thing to understand/explain w/ out seeing it in person, or having a picture like fling posted--altho one picture is hardly enough to see the whole perspective of what is happening.

 

And i am not trying to split hairs---and i dont think any others were either, just trying to 'splain things.

 

BTW? i checked both the helicopters i have here,,,, on the A model?---the twistgrip rolls OFF & the throttle 1/2 way on when collective pulled up,,, the B model just barely opens butterfly off the idle stop.----the B has a "stiffer" feel to the twistgrip tho ( more friction)--need to oil that cable !

Edited November 16, 2006 by pokey

[Jocko]

WHOOAA there big fella……

 

You missed my point entirely I never meant to imply that it was a bad thing (the splitting hairs comment) It teaches those of us who don’t have the experience, like many of you do to look at things a bit more critically then we would normally. I was only trying to use a little humor (and I guess the key word here was Little) to make the point that those of us who are new can get the feeling of being patronized when each and every word of a post is taken so literally. I do enjoy reading and posting here or I wouldn’t visit as often as I do. It forces me to use alternative thought process that a non pilot wouldn’t normally use. That’s the point right? to help us with limited views in this area to open our eyes so to speak to other views and ways of looking at things in the aviation industry. Don’t get me wrong I do enjoy a good argument and I am not above saying something just to see the reaction I get from ya‘ll. All I’m saying is not everything needs to be taken so literally.

 

I hope I made myself a little easier to understand

 

And please

 

Rock on

 

P.S.

 

Pokey,

(your post went up when I was typing)

 

Thanks for that explanation that was much easier to follow, I’m amazed that I was even in the same ball park

Edited November 16, 2006 by Jocko

[joker]

LOL!!!

 

OK, I see what you mean! When I was typing my reply, I was wondering if I understood your post properly. Sorry!

 

Anyway, in short, this board is one of the better ones because most of the posts are not meant to be patronising, but genuinely there to help.

 

Whether we call it 'hair splitting' or 'being accurate' is for the reader to choose. Sometimes people will hair split because they enjoy it, other times they will be accurate because they feel it warrants that.

 

Joker

 

And by the way...I will 'Rock on' if I knew how!!!!

[Pogue]

I've found this whole thread really interesting... My total experience with the 300 series consists of watching one fly overhead once in a while. In the Robbie, if you have the governor of (assuming 100% rpm collective down) you have to roll the throttle off as you pull pitch because of the way the correlator is set up. I've never noticed the throttle move independantly though.... Kind of neat...

[C of G]

And by the way...I will 'Rock on' if I knew how!!!!

 

Perhaps not, but I know you've been "Jamin Hard".

 

I think the 300 correlator has been exposed, but what about the R22, has anyone seen it? What does it look like?