RAF flying question

[rgraffeo]

I hope I'm asking this question correctly:
After talking to several RAF pilots at Bensen Days, I want the cabin of my gyro to fly with a more nose up attitude. Currently 3-4 degrees down solo.

My question is by changing the position of the cam in the folding mast to a more forward position would this change the flying attitude of the keel/cabin?
I have the cam in the #2 position, was looking at changing to #1.

[KenSandyEggo]

Rudy, before I had the AAI conversion, I moved to position #1. She flew more level and I believe she showed a little extra speed. Just try it. Don't try changing the cam position by yourself like some dumb-ass I know who wound up having to scream for help from his hangar-neighbors.

[Aussie_Paul]

Rudy, my recollection is that the most forward position of the rotor head is number 4. We have found that the number 4, the heads most forward position, is best. I always wished that there was a number 5 position for the Rafs.

When I rearranged a Raf kit into Hybrid I kept moving the head forward untill the keel flew level at gross weight at cruise speed.

For a start shift the head as far forward as you can. Don't forget to adjust the rotor head travel after you shift the mast. The rotor disc AofA will remain the same as before you shifted the head.

My simple answer is to shift the axle back 2" or 3", and if need be, lower the front of the stab a little. This helps with weight and the solo take off. When flying a Raf solo and not much fuel, the nose comes up too early for my liking, and if you put the nosewheel back on the ground the rotors are slow to come up. I see a lot of Raf pilots when flying solo leave the tail wheel on the ground for quite some time.

Aussie Paul. :)

[StanFoster]

Rudy: My mast is in position #3. Postion #4 is the straightest the mast will get and will give you the most nose up.

In my case with position #3....my hangtest with just myself showed the keel at 5.5 degrees nose down. The acceptable range was 5 to 7 degrees....so that part was good. My intial hope was then when my 270 pound son climbed in as a passenger...that the keel angle would still be in limits. The range was supposed to be between 7 and 10 degrees nosedown. Jeff and I in the RAF during the hangtest made the keel measure 9.25 degrees nosedown.

I was glad that I could fly solo or take Jeff at 270 pounds along...without changing my mast tilt. I have never flown in out of postion #3 as my keel in flight stays at 2 degrees nosedown at all my flying speeds. If you recall the bubble protractor I placed on the dash as a fixed point of angle to veriify what my keel actually is flying at.

Could not be happier with my setup. My Air Command I had would lower its nose the faster you flew. I was wanting to get away from that and I did in my RAF.

Stan

[Harry_S.]

Hi Rudy:

When flying my stock RAF, my mast position was in #3 hole and flew fine.
After adding the Ken J stab (19 lbs) and properly positioning it at zero incidence, I found I had to move the mast to #4 hole. My machine flies just fine as it is now.

I'm guessing your weight to be under 190 lbs.?? Real low pilot weight would probably be in Position #1 and require ballast in the passenger seat when flying solo. As pilot weight goes up, the mast position would most likely go up in the numbered hole position, which would move the bottom of the mast to the rear.

I would suggest you make only one change at a time...fly and evaluate the change.

In your case...I would move the mast from #2 to #3...fly and evaluate it.
Let us know how you did.


Cheers :)

[KenSandyEggo]

I never could keep 4 from 1 straight. I meant the most upright position.

[rgraffeo]

I'm 170# & when I fly solo I add extra fuel for weight.
The gyro does like Paul stated it wants to leap off the ground solo.
If I leave the cam in the position its in & just move the bolt to the rear hole would be position #4. According to the manuel that position should give me an extra 1-1/2 degrees nose down.

What do you guys think?

[Harry_S.]

Ken...I believe only the casino's keep the numbers straight. :p :D


Cheers :)

[Harry_S.]

Rudy...No You want to move the hole to the rear.

The holes are as follows:

The holes are numbered and located from front to rear as; looking from either side of the gyro...No.1 hole is towards the nose of your gyro...progressing to the rear, are hole numbers 2, 3 and 4...with hole #4 being the most rearward.

No.1 hole will put the top of your mast towards the rear. No.4 hole will put the top your mast at the most forward position.

The two holes in the *cam* are easily confused as to numbers. Insert the cam so that the nearest hole, edge distance wise, is towards the nose of your gyro. That hole is No.1. The other hole is No.3. Rotate the cam 180 degrees and the nearest hole, edge distance wise is towards the tail of your gyro. That hole is now No.4. The other hole is No.2. Remember...The holes are 1 and 3...2 and 4. Clear as mud, huh?! :confused:

Hope this helps you, Rudy. :D


Cheers :)

[Al_Hammer]

I was also told by decreasing the rearward tilt of the rotorblades would cause less drag & make the rotors more efficient.
All the other RAFs I looked at have the mast position more forward that mine.



I think its worth mentioning that the concept quoted above is not correct.
Although I received my solo sign-off in a RAF, I am not an owner and don't know anything about the mast positions, however, I can tell you that the rotor will not fly at a shallower angle by simply moving the mast.

If you think about it, the rotor must fly at a given angle(relative to the airstream) to support the weight of the gyro. If you change the mast angle, the keel will fly at a different angle, which is what you want. It has nothing to do with reducing rotor drag, because, again, the rotor will always fly at the same angle and have the same drag for a given weight and rotor rpm, etc.

[Harry_S.]

I agree with Al.


Cheers :)

[rgraffeo]

Harry,
you gave me lots to think about. I'm working nights this weekend & will go to the airport monday to check out the cam postitions. I was looking at the manuel when I typed my last post.
It will be a few weeks before I can test fly my gyro since I sent off the hubbar to RAF to get the replacement parts.

[KenSandyEggo]

Thanks for reminding us of that, Al. So all we're doing is adjusting the angle of the cabin/keel as we fly through the air. Would I be correct in stating that the more level the keel, the more efficient, or not necessarily so?

[Al_Hammer]

Would I be correct in stating that the more level the keel, the more efficient, or not necessarily so?

I would think so, in terms of cabin aerodynamics, Ken. It also depends on what angle of attack the stab is seeing and what the download is in level flight.

[Aussie_Paul]

..... I was testing at that time to see if having the nose of the Raf higher would alleviate some of the down force that the windscreen creates the faster you go.
I believe that I was using position 4 (rotor head as far forward as possible) the thrust line 3 degrees pointing down, ie the front of the engine lower. I was using the engine crank as the horizontal datum, and set the controls to that datum. I had to go this way as I could not change the cabin on the Raf frame.

My thoughts were "less down force from the windscreen would mean less work for the stab."

This was nothing to do with how Rafs fly, but to gain experience for Firebird.

Am, I on the correct track or not Al?

Aussie Paul. :)

[C. Beaty]

I was also told by decreasing the rearward tilt of the rotorblades would cause less drag & make the rotors more efficient.


Interesting statement, Rudy that illustrates just how dumb grown men can be.

Since the stick controls the rotor angle of attack, why not just push it a couple of inches forward to lower the rotor drag?

The angle at which a given rotor flies is fixed in space and is determined solely by load and airspeed.

[birdy]

Ya beet me to it Chuck B.
I'v heard and read some very interesting and outright dangerous 'theories' bout gyros over time, so its not supprising some people git a bit confused now n then ay.

[C. Beaty]

The discouraging thing about these voodoo theories, Birdy, is that most originated from RAF and/or their agents.

I was first informed that the cabin dangle angle affects rotor drag a number of years ago by an RAF dealer/CFI.

The length of tenure of RAF agents is a pretty good go/no go gauge of intelligence. Those with IQs in the 100+ range either quit in disgust or were sacked by RAF for their back talk. Those with IQs in the 100- range found a happy home and stayed.

That’s not to imply that brilliance is a prerequisite to be a skilled pilot or even to be a good instructor. But an instructor ought to be bright enough to be able to provide his students with factual information.

[Doug Riley]

The fact that RAF's with stock thrustline locations and prop-above-crankshaft redrives fly best with the head moved forward is consistent with what we know about HTL machines.

Moving the head forward allows the CG to sit behind the rotor thrust line while the craft still flies level. If you try to fly a HTL machine with Bensen-style hang specs (keel hangs at -11 or so), you'll find that it flies very nose-down. It HAS to fly this way in order for the CG to get behind the RTL and balance everything out.

Having the RTL ahead of the CG works OK to balance out the prop thrust in steady flight. It's less satisfactory in rough air, since the changes in rotor thrust haul the nose up and down in directions that tend to exaggerate the bumps. If you can get the RTL to land BEHIND the CG, the changes in rotor thrust haul the TAIL up and down in a way that actually smooths out the bumps. E.g., the best way to fly a Dominator in turbulence is to hold the stick steady -- no "floating" the stick or chopping throttle. The airframe itself acts a giant weathervane (but in the ptich axis) and helps keep the rotor's angle of attack constant.

One way to get the RTL behind the CG is to go to something approximating CLT (a la the Sparrowhawk and new Air Command conversions) . Another is to crank a bunch of down-load into a powerful enough H-stab. If you make either of these changes, you'll have to move the rotor head back to comply with the Bensen hang spec, or you'll fly way too nose-high. IOW, when you make such changes, you eliminate the need for a tail-heavy setup.

(A H-stab with little or no incidence will improve the HTL machine's stability. However, in turbulence, the machine will have to pitch a few degrees -- in the wrong direction -- before the HS gets an adequate "bite" on the air to arrest further pitching. A "loaded" HS requires you to change your hang spec, but, if powerful enough, it will eliminate any tendency toward wrong-way pitch excursions.)

[Aussie_Paul]

Geez Chuck, I had better get my IQ tested. Maybe I should have stayed in the "happy Raf home"!!!!

Aussie Paul.:)

[LARRYEBOYER]

Rudy, It was good to meet you and thank you for the tour of the Wachovia area!!!I think your machine flies great. In answer to your question of position, try position number 48. Opps, I was thinking about something else.I have tried all 4 positions and have found #4 to be the best. The mast is the most forward.