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partner14
Joined: 12 Jan 2008
Posts: 540
Location: Granbury Texas
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 Posted: Wed Jul 08, 2009 7:10 am Post subject: Glide Test |
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Has anyone run a test for approx glide slope. I was flying along side a 182 yesterday and we both were at 4,500' and 150mph. When exactly (withing a tenth) 20 miles from our destination, we pulled throttle and prop. I then trimmed for 87mph and continued until altitude read 2,500'. We had gone 9.8 statute miles. The numbers were so good the 182 pilot said we must have done it wrong. We did determine that at the lower part of the decent we had a tailwind. But that works out to a 25 to 1 glide slope.
So we did the same test on the way back, only continued the decent from 4,500 to 2,000'. This time it was considerably less at 7.3 miles. One factor was that our initial speed entering the test was 30mph less. But even so our glide slope with the headwind was 15.4 to 1.
I guess the true test would be an actual engine shut down.
Comments?
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Don A. McDonald
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jkreidler
Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI
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| Posted: Wed Jul 08, 2009 9:02 am Post subject: Glide Test |
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Glide tests, and time to climb tests should be included in the Phase 1 tests period. The test should at a minimum be repeated at light weight, and gross weight. These numbers are used to develop the POH.
I just calculated our gross weight results last night, seems to me the number was somewhere around 8 (prop full forward).
The procedure to gather the numbers is highlighted in AC 90-89 & in Vans documentation. They have slightly different approaches. But here is what we used.
For descent:
Climbed to ~7500, then pulled power and stabilized at an airspeed. This needs to be done at multiple airspeeds, we did 75, 80, 85, 90, & 95 (knots) lightweight, and 80, 85, 90, & 95 (knots) at gross weight.
Started a timer as passing through 7000 noted time at 6000 feet, and stopped the timer at 5000 feet.
Then:
2000 (this is how far you descended) / time (in seconds)
Then:
The answer from above x 60 This converts the value from Feet per Second to Feet per Minute
This is your sink rate in Feet per Minute
Then:
(Airspeed MPH x 8 / Sink Rate FPM
or
(Airspeed Knots x 101.27) / Sink Rate FPM
This is you Lift to Drag Ratio or Glide Ratio The highest L/D Ratio is the winner and should be used as a guideline for your glide speed.
For Climb:
Use the same sort of procedure, start a climb at 3000 feet, start a timer as you pass through 4000 feet, stop the timer as you reach 6000 feet. Do this at several airspeeds, lightweight and gross weight. If I recall we used 75, 80, 85, 90, 95, (at) 100 (knots).
The process to interpret the data is well outlined in Vans documentation or AC 89-90.
I am no expert, I am sure others on the list have more to offer, but now you know what I know.... What tests did you conduct during Phase 1? We are getting close to wrapping up Phase 1 and want to make sure we don't miss a test others have done....
Thanks, Jason Kreidler
#40617 - N44YH Flying
4 - Partner Build -Sheboygan Falls, WI
Kyle Hokel
Tony Kolar
Wayne Elsner
Jason Kreidler [quote][b]
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Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617 |
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indigoonlatigo(at)msn.com
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dlm46007(at)cox.net
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| Posted: Wed Jul 08, 2009 4:56 pm Post subject: Glide Test |
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Seems to me that best glide should be prop control full aft (high pitch,low RPM). Throttle at idle and prop forward (low pitch , high rpm) causes the prop to act like a big brake?
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Gonzalez
Sent: Wednesday, July 08, 2009 2:54 PM
To: RV 10 group
Subject: RE: Re: Glide Test
All this testing for L/D needs to be done in early morning, calm air. It makes a difference.
To: rv10-list(at)matronics.com
Subject: Re: Glide Test
From: jason.kreidler(at)regalbeloit.com
Date: Wed, 8 Jul 2009 11:55:47 -0500
Glide tests, and time to climb tests should be included in the Phase 1 tests period. The test should at a minimum be repeated at light weight, and gross weight. These numbers are used to develop the POH.
I just calculated our gross weight results last night, seems to me the number was somewhere around 8 (prop full forward).
The procedure to gather the numbers is highlighted in AC 90-89 & in Vans documentation. They have slightly different approaches. But here is what we used.
For descent:
Climbed to ~7500, then pulled power and stabilized at an airspeed. This needs to be done at multiple airspeeds, we did 75, 80, 85, 90, & 95 (knots) lightweight, and 80, 85, 90, & 95 (knots) at gross weight.
Started a timer as passing through 7000 noted time at 6000 feet, and stopped the timer at 5000 feet.
Then:
2000 (this is how far you descended) / time (in seconds)
Then:
The answer from above x 60 This converts the value from Feet per Second to Feet per Minute
This is your sink rate in Feet per Minute
Then:
(Airspeed MPH x 8 / Sink Rate FPM
or
(Airspeed Knots x 101.27) / Sink Rate FPM
This is you Lift to Drag Ratio or Glide Ratio The highest L/D Ratio is the winner and should be used as a guideline for your glide speed.
For Climb:
Use the same sort of procedure, start a climb at 3000 feet, start a timer as you pass through 4000 feet, stop the timer as you reach 6000 feet. Do this at several airspeeds, lightweight and gross weight. If I recall we used 75, 80, 85, 90, 95, (at) 100 (knots).
The process to interpret the data is well outlined in Vans documentation or AC 89-90.
I am no expert, I am sure others on the list have more to offer, but now you know what I know.... What tests did you conduct during Phase 1? We are getting close to wrapping up Phase 1 and want to make sure we don't miss a test others have done....
Thanks, Jason Kreidler
#40617 - N44YH Flying
4 - Partner Build -Sheboygan Falls, WI
Kyle Hokel
Tony Kolar
Wayne Elsner
Jason Kreidler [quote]
ttp://www.matronics.com/Navigator?RV10-List
ronics.com
ww.matronics.com/contribution
href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
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pilotdds(at)aol.com
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| Posted: Wed Jul 08, 2009 6:53 pm Post subject: Glide Test |
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That is consistant with my training and experience with a non feathering prop.Pulling the prop control back gives a very noticable reduction in drag and extends the glide.
Important part of our emergency procedures in the sheriff dept C-206.I have often wondered if it was hard on the equipment,any thoughts?
--
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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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| Posted: Wed Jul 08, 2009 7:07 pm Post subject: Re: Glide Test |
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Yes, pulling the prop control out (coarse pitch, low rpm) will improve the glide. I know of no reason this shouldn't be done, in practice or in an actual emergency. Keep in mind, in a real emergency, that this won't work if the engine failure was due to zero oil pressure - you've got to get oil to the governor to get the prop to coarse pitch. So it might be a good idea to practice both ways!
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Bob Turner
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