converting RAF2000 to the superior Sport Copter rotor system

[Kolibri]

My original comment on flying in crosswinds was about holding a WCA (wind correction angle), which then took more right stick because of insufficient right roll trim at the time.

Then, two people started talking about crabbing, which to me only made sense if ruddering into the wind (for example, just after takeoff, or during a crabbed final before going into a slip). My statement was politely corrected that one doesn't use the rudder for a heading (i.e., the longitudinal axis of the aircraft, not the track) into crosswind to maintain a desired course . . . thus the semantic tangle over "crabbing". I appreciate Vance's supplied FAA Aerosense definition, which is how I've understood/used the term.

__________

My pitch trim is the stabalator,it is a true aerodynamic trim. It really works excellent.
and it is electrically operated (toggle switch). Should be around the end of the month.

eddie, that will help you acclimate to the new rotors.
I wonder how many RAFs with SC blades have the Stabilator? I'd guess at least half.

__________
Weather still a bit crudy, but it clears up a bit later this week, so I look forward to finishing up Phase 1 then.

Regards, Kolibri

 

[eddie]

I am looking forward for you report,hope the adjustments made will help.



Best regards,

 

[eddie]

Vance thats quite a suprise because I have always thought that the explanation fara gave

was the right one. Thats the way it was explaned to me 48 years ago,oh well live and

learn. On second thought I believe your source is wrong and that fara and I are right.




Best regards,

 

[Kolibri]

Since crabbing is certainly performed on final with rudder, perhaps that the best use of the term? A WCA heading, however, does look like crabbing viewed from above.

 

[eddie]

Its called crabbing because crabs move sideways to go forward,thats what happens when

you are turned into the wind to maintain your heading,no rudder input is required.Lowering your wing to hold heading and then using the rudder to

fly in a straight line is not crabbing, its more of a forward slip,because you are cross controlled.



Best regards,

 

[Vance]

Another source

Another source

Vance thats quite a suprise because I have always thought that the explanation fara gave

On second thought I believe your source is wrong and that fara and I are right.

Best regards,

AvSpeak
A Glossary of Aviation
Terms and Abbreviations
Aviation related terms and definitions used in association with civil flight obtained from the Code of Federal Regulations, Federal Aviation Regulations, and many other sources.

CRAB - A rudder-controlled yawing motion to compensate for a crosswind in maintaining a desired flight path, as in a landing approach.

In my opinion this semantics squabble it is about reference.

If I am crabbing to maintain runway alignment I use the rudder.

If I am crabbing to maintain a ground track then I don’t use much rudder.

In both cases I have some side stick in to manage ground track.

It is not uncommon for pilots to imagine a gyroplane rudder is for steering and I feel it is important to recognize it is only to manage yaw.

I feel there is value in coordinated flight in a gyroplane.

 

[Kolibri]

. . . when you are turned into the wind to maintain your heading,no rudder input is required . . .

Actually, eddie, you turn into the wind to maintain your course. In other words, "heading" is "course adjusted for crosswind".

Not to be picky, derail the thread, etc.

 

[PW_Plack]

If I am crabbing to maintain a ground track then I don’t use much rudder. In both cases I have some side stick in to manage ground track.

Vance, now you've got me confused at a higher level. This is a little like the whole downwind turn debate.

If I am in coordinated flight and crabbed to maintain a ground track, I should have neither cyclic nor rudder in. The gyro doesn't know or care about the ground track; it's just flying through a body of air which happens to be moving in a direction other than the one needed to reach the destination.

Aerodynamically, it's just straight and level flight, right? The only time cyclic or rudder would be needed is if the crab angle requires adjustment to maintain course. Once that coordinated turn is completed, there's no aerodynamic difference from flying straight toward your destination on a windless day.

 

[Vance]

A specific example of crabbing to follow a ground track.

A specific example of crabbing to follow a ground track.

Sorry to confuse you Paul. I will use a specific example of crabbing to follow a ground track.

When I fly north up the beach with an on shore breeze the nose of the aircraft is pointed out to sea (crabbing) so I have a little right cyclic in so that I follow the shoreline (ground track) rather than heading out to sea as I would with the cyclic neutral. In The Predator I would be rudder neutral.

I often shoot my pictures in The Predator straight over the nose. In the first picture I am pointed more out to sea because of the onshore breeze and have some right stick in to follow the shoreline (ground track), in the second not as much of either because there is less of an onshore breeze and she is pointed more up the beach (same ground track less wind).

In both pictures the yaw string is straight back indicating coordinated flight.

 

[Stan V]

Sorry to confuse you Paul. I will use a specific example of crabbing to follow a ground track.

When I fly north up the beach with an on shore breeze the nose of the aircraft is pointed out to sea (crabbing) so I have a little right cyclic in so that I follow the shoreline (ground track) rather than heading out to sea as I would with the cyclic neutral. In The Predator I would be rudder neutral.



In both pictures the yaw string is straight back indicating coordinated flight.

Vance, if you are having to hold a little right cyclic in this example, you have a trim issue, nothing more. A crab while turned some into the wind to maintain track is neutral rudder and cyclic, a slip is cross controlled to maintain alignment as well as track .

 

[Vance]

Vance, if you are having to hold a little right cyclic in this example, you have a trim issue, nothing more. A crab while turned some into the wind to maintain track is neutral rudder and cyclic, a slip is cross controlled to maintain alignment as well as track .

The Predator doesn’t have inflight adjustable trim Stan.

She flies in the direction the nose is pointed with the cyclic and rudder neutral with the yaw string straight back.

At this time she is trimmed for 65kts indicated air speed.

If I want to fly in a different direction than the nose is pointed in coordinated flight I introduce some cyclic.

In my example I would fly out to sea if I didn’t introduce some right cyclic.

When I flew an RAF I didn’t use left and right trim to manage a crab because I was training and doing ground reference maneuvers. I didn’t go in one direction long enough to want to trim it out. I can’t imagine using left and right trim for flying a rectangular course.

I wouldn’t trim an RAF to the right for flying up the beach because the wind changes from one end of the beach to the other (Guadalupe to the cliffs of Shell Beach is about ten miles).

 

[Stan V]

The Predator doesn’t have inflight adjustable trim Stan.

If I want to fly in a different direction than the nose is pointed in coordinated flight I introduce some cyclic.

In my example I would fly out to sea if I didn’t introduce some right cyclic.

If you're having to introduce some right cyclic and you are flying at what you think is your trimmed speed in coordinated flight then you need to adjust your trim spring for a little more right cyclic. A crab is coordinated flight. If you are having to hold cyclic or rudder in to maintain coordinated flight, you are out of trim.

 

[Stan V]

Vance, now you've got me confused at a higher level. This is a little like the whole downwind turn debate.

If I am in coordinated flight and crabbed to maintain a ground track, I should have neither cyclic nor rudder in. The gyro doesn't know or care about the ground track; it's just flying through a body of air which happens to be moving in a direction other than the one needed to reach the destination.

Aerodynamically, it's just straight and level flight, right? The only time cyclic or rudder would be needed is if the crab angle requires adjustment to maintain course. Once that coordinated turn is completed, there's no aerodynamic difference from flying straight toward your destination on a windless day.

Vance, Paul said it best.

 

[Abid]

Sorry to confuse you Paul. I will use a specific example of crabbing to follow a ground track.

When I fly north up the beach with an on shore breeze the nose of the aircraft is pointed out to sea (crabbing) so I have a little right cyclic in so that I follow the shoreline (ground track) rather than heading out to sea as I would with the cyclic neutral. In The Predator I would be rudder neutral.

I often shoot my pictures in The Predator straight over the nose. In the first picture I am pointed more out to sea because of the onshore breeze and have some right stick in to follow the shoreline (ground track), in the second not as much of either because there is less of an onshore breeze and she is pointed more up the beach (same ground track less wind).

In both pictures the yaw string is straight back indicating coordinated flight.

Huh?
Something seems off here Vance. May be the words are not coming out right. You should not have any cyclic, you should be S&L and co-ordinated here once the nose has been pointed the right amount into the wind, your ground course may be different than the direction your nose is pointing but no rolling or slipping is required for crabbing. The FAA definition seems to be defining the establishing of the crab action not actual crabbing to me also. Not a good one imo.

 

[PW_Plack]

The FAA definition seems limited to the specific circumstances of a landing approach and, even then, it's not technically correct.

 

[Kolibri]

for eddie

for eddie

Vance kicked off a thread about crabbing, so let's all go there:

How does a gyroplane follow a ground track?
https://www.rotaryforum.com/forum/showthread.php?t=44919


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eddie, since you will require stronger trim forces with your new SC rotors, please have a look at all your RAF cable trim system parts.

In particular, the fender washers on the lower control yoke to which the trim springs are attached. I thought single washers were insufficient, and doubled them (you may need the next longer bolt, such as AN4-17). My original washer holes had nearly been pulled through (only .065" of metal remaining). Any hardware store should have SS ¼" x 2" washers.

During your rotor upgrade, I would recommend that you replace all the control system bolts (i.e., cabin and outside lower control yoke) with drilled shank bolts and nyloc castle nuts (double the safety). Clean and carefully inspect that yoke for any cracks. You may want to consider at this time going to RAF's Product Notice 40 (thicker walled yoke tubes).

You'll probably need stronger trim springs, and others here may have some suggestions/sources. I liked to put a zip-tie in them to keep them from going through the prop. Leave plenty of slack for spring stretch during flight.

If you still have RAF's old control rod ends, dump 'em now for Heim or Auroras.

I highly recommend Mayfield's mod of the pitch control rod using 5/16" shank Aurora rod ends. Until you've removed that OEM aluminum rod with its ¼" rod ends, you won't appreciate how dainty such a flight critical part is. I'm astonished more of them haven't failed, especially during rough ground handling.

You may have to adjust your torque tube pitch stop bolts, and this would be a good time to replace them as a precaution. One RAF fatal crash apparently resulted from a backed out bolt (and thus he couldn't pitch up). Have a look at the indentations the pitch stop bolt heads have made on the aluminum stands (Boo Kindersley!), and check for any cracks.

Somebody had this good advice:

Oh, and don't forget to turn your cotton reels (teeter bolt bushes) whenever you remove or refit the rotors, so teeter bolt doesn't always bear the weight and wear the cotton reels in exactly the same place, forever.

You've much more RAF experience than I have, but I thought I'd mention the above nonetheless.

Regards, Kolibri

 

[eddie]

Thanks for the suggestions,have you anymore flight data on your rotors.



Best regards,

 

[SARAF]

torque tube ajusters

torque tube ajusters

"You may have to adjust your torque tube pitch stop bolts, and this would be a good time to replace them as a precaution. One RAF fatal crash apparently resulted from a backed out bolt (and thus he couldn't pitch up). Have a look at the indentations the pitch stop bolt heads have made on the aluminum stands (Boo Kindersley!), and check for any cracks"

If you still have the bolts that acted as stops in the torque tube then you have an outdated system.

This application has been changed.

Regards
Eben

 

[Kolibri]

If you still have the bolts that acted as stops in the torque tube then you have an outdated system.

This application has been changed.

Glad to hear that, thanks Eben.
Was there a Product Notice about this? I didn't know the stops had been changed.

______
eddie, no further flight data yet, winds have still been over 20kts or it's been snowing. Next week is supposed to clear up.

 

[eddie]

Yep, wind is still blowing here I thought it would have calmed down by now,but thats what

I get for thinking. I wont be suprised if I dont have my rotors on by the end on this month

and am flying before you.





Best regards,