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n752ms(at)softcom.net
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 Posted: Sun Jul 19, 2009 11:13 am Post subject: vg's |
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I'm flying the 701 with a Rotax 912ULS with strut fairings, this morning it was at about 1000 lbs gross weight. Air was about 75 degrees at an alt of 1000 ft that is a density alt of about 2260 ft. On the ground density alt was 1100.
I have just installed the plastic vg's (yesterday) from StolSpeed and spent some time this morning doing some testing. If I had not painted my plane yet the aluminum ones would get some serious consideration. The plastic ones take some time to put the adhesive on and then line them up on the elevator, total install time was about four hours. They don't conform to the radius of the elevator all that well, so we sill see how long they stay on.
I tend to come in on short final with no power, flaps or no flaps. 15 degree flaps take a little more practice with no power. The vg's did most certainly give me more elevator authority.
On a power off stall the vg's seem to make the approach to the non stall much smoother. My CFI was amazed at the power off stall, no dropping of the nose, full aft elevator with a slight buffeting. Just sinks at 900 fpm. Full power stall is about the same except a much higher AOA and about 200 fpm sink rate. And a 5mph ground speed on the GPS.
Also did an engine off approach (prop stops on a Rotax 912) to a full stop landing, wanted to see if the glide ratio was any different than with the engine at idol and prop turning. I did not do a four direction glide to compensate for any wind, this morning I could not detect any wind. It sank at a higher rate than with the prop turning. This is contrary to what I have been told. The only thing I can think is that at idol the prop on a Rotax 912 is turning enough that it helps with the glide. There was a considerably steeper nose down attitude with the prop stopped than with it turning at the same air speed.
I also did my first off airport landing and take off this morning. Used a local hay field, it looked smooth but sure felt rough when I landed. I used 15 degree flaps on take off and that make things lighter on take off and much smoother. I probably have to much air in the tires. How much pressure are some of you using to smooth out the rough fields? I have the tube type tires and don't want to spin the tires on the rim.
Eight more hours to fly off my 40.
Mark S.
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John Bolding
Joined: 23 May 2006
Posts: 281
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| Posted: Sun Jul 19, 2009 11:41 am Post subject: vg's |
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Found the same thing to be true on an RV about 10 yrs ago, mine was NOT a planned event however, sunk a LOT faster than with the engine at idle
LO&SLO John
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Tommy Walker
Joined: 12 Jan 2006
Posts: 442
Location: Anniston, AL 36207
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| Posted: Sun Jul 19, 2009 1:30 pm Post subject: Re: vg's |
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Hi,
Did you put the VG's on both the wings and elevator, or just the elevator?
Thanks for the report!
Tommy Walker in Alabama
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Tommy Walker
N25A - Anniston, AL |
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ronlee
Joined: 25 Dec 2006
Posts: 141
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| Posted: Sun Jul 19, 2009 1:43 pm Post subject: Re: vg's |
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I keep just enough air in my 701 tires so they don't sag much. It is about 10 pounds or less. I don't have tubes in mine though.
I have heard of people running short screws through the rim into the bead of the tire to keep them from rotating on the rim. I think this is common practice on ATV machines that run real low pressure. I have never done this as I don't have that trouble. Now I must say they may have slipped without me knowing it and didn't lose any air.
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Ron Lee
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n752ms(at)softcom.net
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| Posted: Sun Jul 19, 2009 6:11 pm Post subject: vg's |
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Tommy.
Just on the elevator, I still have the slats on.
Mark S.
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vgstol(at)bigpond.net.au
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| Posted: Tue Jul 21, 2009 4:00 pm Post subject: vg's |
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Yeh Mark, I'm glad you raised that engine off prop-stopped issue. Contrary to what is often stated, the glide ratio is much less with the engine stopped than idling. Everyone should be aware of that in case of a real engine out!
Everyone should try it sometime, so that you're prepared for the sensation of the sudden quiet, the different feel of the controls, and the steeper attitude required to maintain safe speed. If it catches you by surprise sometime at a lower altitude, it could be unsettling enough to cause a loss of control.... From 3000 AGL, set up a glide at 50 kts, and note the descent rate with engine at idle, then switch off the engine and notice the difference in nose-down attitude required to maintain the same airspeed. It's a strange experience to hear the wind rushing by, and to be 'flying' the aircraft like a glider rather than just 'driving' along behind the engine. The glide is very stable if you keep the airspeed correct, and the silence is so enjoyable that it becomes a bit addictive!
But a couple of tips - As soon as the engine has stopped, switch the mags back on so it's all ready when you want to re-start. If you don't, sure as heck you'll try to restart with them off, and then when it doesn't start right away you will get a fright..... And do it on a calm day over a long airstrip with no circuit traffic, just in case the starter motor decides to fail.......
Try it, it's a valuable experience, and a lot of fun.
JG
[quote] Also did an engine off approach (prop stops on a Rotax 912) to a full stop landing, wanted to see if the glide ratio was any different than with the engine at idol and prop turning. I did not do a four direction glide to compensate for any wind, this morning I could not detect any wind. It sank at a higher rate than with the prop turning. This is contrary to what I have been told. The only thing I can think is that at idol the prop on a Rotax 912 is turning enough that it helps with the glide. There was a considerably steeper nose down attitude with the prop stopped than with it turning at the same air speed.
Mark S.
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