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larry(at)macsmachine.com
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 Posted: Mon Aug 06, 2007 8:27 am Post subject: in-flight adjustable props |
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Hi guys,
Is anyone flying a Stratus Subaru with an in-flight adjustable prop with
any success?
I understand that a re-drive may have some adverse effect on these things,
but I'd still like to know if it's doable, practical, safe or not.
Warp Drive has an in-flight adjustable in development, but they've made no
further comments.
Larry McFarland
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frank.hinde(at)hp.com
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larry(at)macsmachine.com
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| Posted: Mon Aug 06, 2007 12:21 pm Post subject: in-flight adjustable props |
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Hi Frank,
I agree with you entirely, but the reason I'd like an adjustable is for
the low end. I fly with my pitch at 17-degrees and the performance
is very acceptable, but getting out of short grass strips with long corn
is sometimes a concern. Being able to put it into low gear would
be the best value to me. The high end is not at issue, but if I could
adjust to 18 or 19-degrees, it might be interesting to know where
the prop begins to labor. My worry is that some of these in-flight
adjustable props really don't like re-drive harmonics.
Larry McFarland 601HDS at www.macsmachine.com
Hinde, Frank George (Corvallis) wrote:
[quote]
I have no data Larry but I would doubt if the cost is worth it for the
performance gains you would see in a Zodiac.
If you have a ground adjustable prop you can do is to ground adjust
pitch and measure your cruise speed increase vs fuel burn data.
I.e set your cruise up at say 5000 ft, pull your fuel burn down to 5GPH
and see what speed you get over a 3 way course using one of the online
calculators.
Do this for various pitches and see what benefit you will get form being
able to increase the pitch in flight.
My personal guess is that it won't be worth it an a draggy airplane like
the Zodiac.
Now in the RV...its a different story..
Frank
601HDS modified Stratus 400 hours
RV 7a IO360 Constant speed 200 hours
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frank.hinde(at)hp.com
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| Posted: Mon Aug 06, 2007 12:39 pm Post subject: in-flight adjustable props |
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Hey Larry,
I did try 14 deg (if I remember correctly) and I did not gain anything
in terms of cruise performance above that pitch. This would make sense
for a relatively draggy airplane, i.e for any particular pitch the
relative angle of attack reduces with increases in speed and prop
efficiency decreases. Thus as speed goes up you want to increase pitch.
For an airplane that only cruises at 100mph anyway then further
increases in pitch are unlikely to help much...except that RPM will
reduce which may aid a bit.
Anyway, you could still do the same experiment and see how much your
short field performance increases and what it does to your cruise speed
as you reduce pitch.
There is a bit of getting used to an engine that is turning faster than
your used to in cruise but that's a just a "head thing"..
Certainly 11 degrees it makes the HDS a rocket ship off the ground, but
then your stuck in low gear.
How short is your short strip?
I was working out of 1600ft grass with big trees at the end of a
displaced threashold and 14 deg with the same engine made it quite
comfortable.
If I were in your shoes I would avoid the variable pitch prop...As you
said a few unkowns that would make me nervous.
Of course I'm a little spoiled right now...On a cool morning I see
2600FPM solo at 250MSL...Woohoo!
Frank
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larry(at)macsmachine.com
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| Posted: Mon Aug 06, 2007 2:18 pm Post subject: in-flight adjustable props |
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Yes Frank,
Flying at 15-degrees seemed much like being in a slingshot. After the
climb out, the rpm and airspeed stayed pretty much
the same. I eventually got everything faired in nicely and worked up to
17-degrees. Lightly loaded at 3500 feet the top end is 133 mph.
Cruise is 120 and it sounds better with that pitch and burns 4 gph. Go
faster and it burns 5. The flying I do is more
about access than destination and there are two strips that are called
"1500 ft" with tall corn each end. Mowing is questionable.
I get off concrete in 800 ft with a full header tank, but not with a
passenger. Does make one feel a little nervous trying to drop over the
corn
and then worry about running into it at the other end on takeoff. I
don't like flying the HDS at less than 17-degrees so the in-flight
adjustable is
an intriguing consideration for shorter fields.
The next project will likely be a gyro. Some are shortening lift off and
using higher
inertia blades to round out the flight envelope. I attended Mentone
this past week for the rotary aircraft gathering and it was interesting.
Didn't bother to go to Oshkosh this year because innovation has
essentially been replaced by sales hype.
Thanks,
Larry McFarland 601HDS at www.macsmachine.com
Hinde, Frank George (Corvallis) wrote:
[quote]
Hey Larry,
I did try 14 deg (if I remember correctly) and I did not gain anything
in terms of cruise performance above that pitch. This would make sense
for a relatively draggy airplane, i.e for any particular pitch the
relative angle of attack reduces with increases in speed and prop
efficiency decreases. Thus as speed goes up you want to increase pitch.
For an airplane that only cruises at 100mph anyway then further
increases in pitch are unlikely to help much...except that RPM will
reduce which may aid a bit.
Anyway, you could still do the same experiment and see how much your
short field performance increases and what it does to your cruise speed
as you reduce pitch.
There is a bit of getting used to an engine that is turning faster than
your used to in cruise but that's a just a "head thing"..
Certainly 11 degrees it makes the HDS a rocket ship off the ground, but
then your stuck in low gear.
How short is your short strip?
I was working out of 1600ft grass with big trees at the end of a
displaced threashold and 14 deg with the same engine made it quite
comfortable.
If I were in your shoes I would avoid the variable pitch prop...As you
said a few unkowns that would make me nervous.
Of course I'm a little spoiled right now...On a cool morning I see
2600FPM solo at 250MSL...Woohoo!
Frank
--
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frank.hinde(at)hp.com
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| Posted: Mon Aug 06, 2007 2:30 pm Post subject: in-flight adjustable props |
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Sounds like you got some significant drag reduction to work on the HDS
there Larry.
Good for you.
I was tempted to start doing this work but realised my priorities had a
changed a bit from when I built the HDS...I.e IFR, aerobatics and fast
cross country.
Would have been a fun project though.
Cheers
Frank
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d3dw(at)sbcglobal.net
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| Posted: Mon Aug 06, 2007 6:13 pm Post subject: in-flight adjustable props |
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When I started flying the HDS in 1999, I found very quickly that keeping the bird light is the key. It didn't take long to see that the "published" or popular prop setting weren't for me. Experiementing from the gitgo, I set it at 17 and found no tendency to feel loaded at all. that let me climb at 1800 fpm initial clomg with an all out speed of 125. that was with a 612 lb empty weight and loaded light...150 lb. pilot. With this I was off the ground and climbing like heck after 450Ft. take off roll. No problem getting off anywhere. Reiner told me my Stratus was putting out 113 hp. Of course I wrung that engine out pretty quickly with the valve guide problems. don
LarryMcFarland <larry(at)macsmachine.com> wrote: [quote]--> Stratus-List message posted by: LarryMcFarland
Yes Frank,
Flying at 15-degrees seemed much like being in a slingshot. After the
climb out, the rpm and airspeed stayed pretty much
the same. I eventually got everything faired in nicely and worked up to
17-degrees. Lightly loaded at 3500 feet the top end is 133 mph.
Cruise is 120 and it sounds better with that pitch and burns 4 gph. Go
faster and it burns 5. The flying I do is more
about access than destination and there are two strips that are called
"1500 ft" with tall corn each end. Mowing is questionable.
I get off concrete in 800 ft with a full header tank, but not with a
passenger. Does make one feel a little nervous trying to drop over the
corn
and then worry about running into it at the other end on takeoff. I
don't like flying the HDS at less than 17-degrees so the in-flight
adjustable is
an intriguing consideration for shorter fields.
The next project will likely be a gyro. Some are shortening lift off and
using higher
inertia blades to round out the flight envelope. I attended Mentone
this past week for the rotary aircraft gathering and it was interesting.
Didn't bother to go to Oshkosh this year because innovation has
essentially been replaced by sales hype.
Thanks,
Larry McFarland 601HDS at www.macsmachine.com
Hinde, Frank George (Corvallis) wrote:
[quote] --> Stratus-List message posted by: "Hinde, Frank George (Corvallis)"
Hey Larry,
I did try 14 deg (if I remember correctly) and I did not gain anything
in terms of cruise performance above that pitch. This would make sense
for a relatively draggy airplane, i.e for any particular pitch the
relative angle of attack reduces with increases in speed and prop
efficiency decreases. Thus as speed goes up you want to increase pitch.
For an airplane that only cruises at 100mph anyway then further
increases in pitch are unlikely to help much...except that RPM will
reduce which may aid a bit.
Anyway, you could still do the same experiment and see how much your
short field performance increases and what it does to your cruise speed
as you reduce pitch.
There is a bit of getting used to an engine that is turning faster than
your used to in cruise but that's a just a "head thing"..
Certainly 11 degrees it makes the HDS a rocket ship off the ground, but
then your stuck in low gear.
How short is your short strip?
I was working out of 1600ft grass with big trees at the end of a
displaced threashold and 14 deg with the same engine made it quite
comfortable.
If I were in your shoes I would avoid the variable pitch prop...As you
said a few unkowns that would make me nervous.
Of course I'm a little spoiled right now...On a cool morning I see
2600FPM solo at 250MSL...Woohoo!
Frank
--
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http://www.matronics.com/Navigator?Stratus-List |
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frank.hinde(at)hp.com
Guest
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| Posted: Tue Aug 07, 2007 5:50 am Post subject: in-flight adjustable props |
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Yes that little dabacle was a real shame. It was a good package if it wern't for the valve guides and the ignition modules.
Sad really, but at least we found a good solution before anyone got hurt!
Frank
Do not archive
From: owner-stratus-list-server(at)matronics.com [mailto:owner-stratus-list-server(at)matronics.com] On Behalf Of Don Walker
Sent: Monday, August 06, 2007 7:14 PM
To: stratus-list(at)matronics.com
Subject: Re: in-flight adjustable props
When I started flying the HDS in 1999, I found very quickly that keeping the bird light is the key. It didn't take long to see that the "published" or popular prop setting weren't for me. Experiementing from the gitgo, I set it at 17 and found no tendency to feel loaded at all. that let me climb at 1800 fpm initial clomg with an all out speed of 125. that was with a 612 lb empty weight and loaded light...150 lb. pilot. With this I was off the ground and climbing like heck after 450Ft. take off roll. No problem getting off anywhere. Reiner told me my Stratus was putting out 113 hp. Of course I wrung that engine out pretty quickly with the valve guide problems. don
LarryMcFarland <larry(at)macsmachine.com> wrote: [quote][b]
| | - The Matronics Stratus-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Stratus-List |
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Bruce
Joined: 20 Jul 2007
Posts: 1
Location: Portland, OR
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| Posted: Tue Aug 07, 2007 9:22 pm Post subject: Re: in-flight adjustable props |
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Hi Frank,
I'm looking to purchase a Stratus system, could you fill me in on the valve guides and ignition system problems and what the fix was? I'd really appreciate the info.
Thanks,
Bruce
[quote="frank.hinde(at)hp.com"]Yes that little dabacle was a real shame. It was a good package if it wern't for the valve guides and the ignition modules.
Sad really, but at least we found a good solution before anyone got hurt!
Frank
Do not archive
From: owner-stratus-list-server(at)matronics.com [mailto:owner-stratus-list-server(at)matronics.com] On Behalf Of Don Walker
Sent: Monday, August 06, 2007 7:14 PM
To: stratus-list(at)matronics.com
Subject: Re: in-flight adjustable props
When I started flying the HDS in 1999, I found very quickly that keeping the bird light is the key. It didn't take long to see that the "published" or popular prop setting weren't for me. Experiementing from the gitgo, I set it at 17 and found no tendency to feel loaded at all. that let me climb at 1800 fpm initial clomg with an all out speed of 125. that was with a 612 lb empty weight and loaded light...150 lb. pilot. With this I was off the ground and climbing like heck after 450Ft. take off roll. No problem getting off anywhere. Reiner told me my Stratus was putting out 113 hp. Of course I wrung that engine out pretty quickly with the valve guide problems. don
LarryMcFarland <larry> wrote:
| | - The Matronics Stratus-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Stratus-List |
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_________________
Bruce Sturgill
www.pursuitofflight.com |
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