Groen Bros. DARPA Award

Kevin O'Brien wrote:

On 2005-11-11 17:06:20 -0500, boB said:

boB... there are so many Bob's that I spell my name backwards. I
didn't know about Brewton. The IP I called was something like "dolph"
something.


That would be Dofin Fritts. I've flown with him.


That's him....


an alternative to the RAF is the AAI Sparrowhawk, made,
oddly enough, by the selfsame Groen Brothers of this thread.

http;//gbagyros.com/


Thank you for the link. Now I have some time to look at it and from
what you say I would need a flight in each before buying.


If you're in P'cola, the nearest AAI dealer to you is probably Terry
Eiland in the Tampa area.


I'm quite a distance away here in Central Texas. It's a day plus trip
to p'cola


My Toy
http://img247.imageshack.us/img247/3...rastrip8lz.jpg


That page made me grin

That was a fun little aircraft. I always had the feeling of a slow
hovering helicopter when flying it.

Thanks for the information, I really appreciate it.

--

boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)

an alternative to the RAF is the AAI Sparrowhawk, made,
oddly enough, by the selfsame Groen Brothers of this thread.

http://gbagyros.com/

Well I'm just an armchair pilot folks.....

So correct me if I am wrong.

It's unfortunate that Ken Sandy EGGO isn't kicking around the group
these days, as I'm sure he would have jumped into this thread by now.

He lives in San Diego and has been flying Gyros for years.

He is a big big champion of the vertical (centerline) stabilizer on
gyros and I do believe has had his share of arguements with the
developers of the RAF gyros on this subject. He has talked about the
dangers of buntover with resulting death in this group at various
times.

If my feeble memory is correct a few years ago Ken sent his unit
to Groen brothers and had some conversion work done by them, which
they mention on their website

http://www.americanautogyro.com/Phot...%20Gallery.htm

Scroll down the photo page to see pix and surf their website for
written info.

Shiver wrote:

He is a big big champion of the vertical (centerline) stabilizer on
gyros and I do believe has had his share of arguements with the
developers of the RAF gyros on this subject. He has talked about the
dangers of buntover with resulting death in this group at various
times.

Buntover??? In my reading I haven't run across that term. I know how to
keep from causing the normal spike knock, tail boom strikes, 0 G pitch
down and mast bumping problems. From the word, is it a forward
pitchover caused by the horizontal stabilizer being too low?

--

boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)

boB wrote:

Buntover??? In my reading I haven't run across that term. I know how to
keep from causing the normal spike knock, tail boom strikes, 0 G pitch
down and mast bumping problems. From the word, is it a forward
pitchover caused by the horizontal stabilizer being too low?

From the Groen Brothers website

http://www.americanautogyro.com/Cent...line%20Thrust%
20P1.htm

Watch for the URL wraparound

It's described in the first couple of paragraphs.

That link by the way is about four pages long and is interesting
reading.

If my feeble memory serves me correctly.... Oh Mr. Sandy Eggo where are
you......

Ken bought an RAF gyro that did not have a vertival stabilzer.

Correct me if I am wrong.

He became aware of various accidents involving buntover due to no
stabilizer and many of those pilots were killed or seriously injured.

As a result he became a convert to the idea of having a centerline
stabilzer added ( with dihedral I do believe ).

He got into arguements with the RAF people who I presume did not feel
it was necessary.

When Groen brothers offered a factory kit for his RAF gyro he sent it
off to them for upgrading and as far as I know he is a very satisfied
customer.

Shiver wrote:
boB wrote:


Buntover??? In my reading I haven't run across that term. I know how to
keep from causing the normal spike knock, tail boom strikes, 0 G pitch
down and mast bumping problems. From the word, is it a forward
pitchover caused by the horizontal stabilizer being too low?


From the Groen Brothers website

http://www.americanautogyro.com/Cent...line%20Thrust%
20P1.htm

Watch for the URL wraparound

It's described in the first couple of paragraphs.

That link by the way is about four pages long and is interesting
reading.

If my feeble memory serves me correctly.... Oh Mr. Sandy Eggo where are
you......

Ken bought an RAF gyro that did not have a vertival stabilzer.

Correct me if I am wrong.

He became aware of various accidents involving buntover due to no
stabilizer and many of those pilots were killed or seriously injured.

As a result he became a convert to the idea of having a centerline
stabilzer added ( with dihedral I do believe ).

He got into arguements with the RAF people who I presume did not feel
it was necessary.

When Groen brothers offered a factory kit for his RAF gyro he sent it
off to them for upgrading and as far as I know he is a very satisfied
customer.

Thanks. I'll do some reading

--

boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)

"boB" wrote in message
...
Shiver wrote:

He is a big big champion of the vertical (centerline) stabilizer on
gyros and I do believe has had his share of arguements with the
developers of the RAF gyros on this subject. He has talked about the
dangers of buntover with resulting death in this group at various
times.

Buntover??? In my reading I haven't run across that term. I know how to
keep from causing the normal spike knock, tail boom strikes, 0 G pitch
down and mast bumping problems. From the word, is it a forward pitchover
caused by the horizontal stabilizer being too low?

--

boB,
SAG 70

Buntover is just another term for a power push over (PPO). From what I've
gathered in my reading through the years, it's not as much an issue with the
horizontal stabilizer as it is with the placement of the engines thrust line
relative to the vertical CG of the aircraft. Gyros like the stock RAF2000
have the thrust line at a significant distance above the vertical CG of the
aircraft. That imparts a nose down moment when under power. The main
rotor, because it's tilted aft in flight, offers a counter force to the
forward pitching moment. If you unload the main rotor enough, there's not
counter force to that forward pitching moment caused by the engine thrust
line being above the CG and over she goes.

A properly placed and sized horizontal stab can go a long way toward
reducing the possibility of this problem but it doesn't address the root
cause. That being a thrust line that's not properly in line with the
vertical CG of the aircraft. At least that's my understanding. If I'm too
far off on this, I'm sure someone will correct me! :-)

Fly Safe,
Steve R.

Steve R wrote:
"boB" wrote in message
...

Shiver wrote:


He is a big big champion of the vertical (centerline) stabilizer on
gyros and I do believe has had his share of arguements with the
developers of the RAF gyros on this subject. He has talked about the
dangers of buntover with resulting death in this group at various
times.

Buntover??? In my reading I haven't run across that term. I know how to
keep from causing the normal spike knock, tail boom strikes, 0 G pitch
down and mast bumping problems. From the word, is it a forward pitchover
caused by the horizontal stabilizer being too low?

--

boB,
SAG 70


Buntover is just another term for a power push over (PPO). From what I've
gathered in my reading through the years, it's not as much an issue with the
horizontal stabilizer as it is with the placement of the engines thrust line
relative to the vertical CG of the aircraft. Gyros like the stock RAF2000
have the thrust line at a significant distance above the vertical CG of the
aircraft. That imparts a nose down moment when under power. The main
rotor, because it's tilted aft in flight, offers a counter force to the
forward pitching moment. If you unload the main rotor enough, there's not
counter force to that forward pitching moment caused by the engine thrust
line being above the CG and over she goes.

A properly placed and sized horizontal stab can go a long way toward
reducing the possibility of this problem but it doesn't address the root
cause. That being a thrust line that's not properly in line with the
vertical CG of the aircraft. At least that's my understanding. If I'm too
far off on this, I'm sure someone will correct me! :-)

Fly Safe,
Steve R.



Thanks Steve. That sounds like two forces working against each other.
That doesn't seem to be efficient as far as strain on the systems.
Something similar on my Sprint II with the engine and prop above the
vertical CG. If the engine quits or even when throttling down the nose
pops up which screwed up my landings early on. I had been fixed on the
RAF2000 but hadn't really looked at the competition before. I
appreciate all the advice.


--

boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)

"boB" wrote in message
...

Thanks Steve. That sounds like two forces working against each other. That
doesn't seem to be efficient as far as strain on the systems. Something
similar on my Sprint II with the engine and prop above the vertical CG. If
the engine quits or even when throttling down the nose pops up which
screwed up my landings early on. I had been fixed on the RAF2000 but
hadn't really looked at the competition before. I appreciate all the
advice.

boB,
SAG 70

Your welcome Bob! You're right, these forces are working against each
other, and not in a good way. Designs like this have been flown for years
and there are still people out there that insist that it's perfectly safe.
They may have learned to deal with it but the unfortunate fact is that too
many people have died because of the high thrust line designs that didn't
have to.

Personally, I wouldn't touch an RAF2000 with a 10 foot pole but the Groen
Bros version of it looks like a very nice alternative if you've really got
your heart set on a fully enclosed cabin. Of the more open designs around,
I'm really impressed with the Air Command. They are one of the few kit
manufacturers that had the guts and integrity to completely redesign their
gyros when it finally became clear what the high thrust line issues were
doing to the aircrafts stability. They don't sell anything now that's not
centerline thrust and they offer a very reasonable upgrade kit for those who
still have the older high thrust line gyros sitting in the barn. They also
issued, if I'm not mistaken, and air worthiness directive to all owners of
the old high thrust line machines, advising them to "not" fly until it's
been converted to centerline thrust!

Are you familiar with the PRA (Popular Rotorcraft Association)? They can be
found at www.pra.org and are a great source of info on experimental gyros
and helicopters. Also, check out this forum if you're not already familiar
with it,

http://www.rotaryforum.com/index.php

Lots of really great people and good information. Just be aware that the
gyro folks can be, shall we say, "passionate," about their machines so it
sometimes helps to have a thick skin around there. ;-)

Best of luck,
Steve R.

Steve R wrote:

Lots of really great people and good information. Just be aware that the
gyro folks can be, shall we say, "passionate," about their machines so it
sometimes helps to have a thick skin around there. ;-)

Best of luck,
Steve R.

Thanks Steve. I really hope someday to fly again. Until then I have a
lot of time to research. I'm very glad I found you all.
--

boB,
SAG 70

U.S. Army Aviation (retired)
Central Texas - 5NM West of Gray Army Airfield (KGRK)