21 May 2025, 21:18 [ UTC - 5; DST ]
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 14:27 |
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Joined: 01/29/08 Posts: 26338 Post Likes: +13079 Location: Walterboro, SC. KRBW
Aircraft: PC12NG
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Username Protected wrote: So far my SR22T is as fast as my A36TN.
Mine too but that's not the point. The point is "how much faster would your SR22T be if it were retract?" There are many more differences to those airframes than retractable gear. For example, how much faster would the A36TN be if it were made of composite?
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 15:03 |
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Joined: 06/16/08 Posts: 3566 Post Likes: +264 Location: San Rafael, CA (KDVO)
Aircraft: 1979 Bonanza A36TC
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Username Protected wrote: For example, how much faster would the A36TN be if it were made of composite? if it was simply the same shape, but composite rather than metal? no speed difference. There's nothing inherently "faster" about composite than metal. Yes there are no rivets, big deal, the bonanza has mostly flush rivets anyway, and even the dome head rivets really don't add any appreciable drag. What composite gives you is the ability to make different shapes. Specifically, you can contour more accurately for optimal airflow and reduce drag etc. so making the bonanza out of composite does not help making a NEW airplane out of composite, BASED on the bonanza design would be very nice.
_________________ Past 12: IPC/BFR, Spins/Upset, WINGSx2, ASFx2
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 15:47 |
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Joined: 09/02/09 Posts: 8671 Post Likes: +9173 Company: OAA Location: Oklahoma City - PWA/Calistoga KSTS
Aircraft: UMF3, UBF 2, P180 II
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Username Protected wrote: Why doesn't Cirrus make an SR-22 with retractable gear? Seems to me that it is a great airplane that is really fast, but could be a lot faster with RG. Is that not correct? It would be a big reduction in drag I would think. Guess I could be wrong though. Would definitely be heavier that I know so the UL would go down. Maybe that is the issue. Back to you Ben: I think because: 1. It weighs less so useful load is enhanced. 2. It eliminates a lot of potential accidents (gear ups) 3. The Cirrus wing is pretty thin for aerodynamic reasons and retractable gear would have been a significant challenge. 4. Fixed gear costs less. I don't know that that's a particularly big deal now with $750k airframes but 12 years ago I think it was. 5. It's fast enough. In other words it's as fast, close to as fast, or faster, than its competitors. It doesn't help the plane's looks I agree. But it looks good enough. Someone else said "real planes have retractable gear" which is, of course, incorrect. Real planes have two wings and the little wheel is in the back.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 15:57 |
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Joined: 11/06/10 Posts: 12136 Post Likes: +3031 Company: Looking Location: Outside Boston, or some hotel somewhere
Aircraft: None
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Username Protected wrote: In terms of the aerodynamics, a few things to consider: 1. Drag is largely based on KIAS, not KTAS. 2. Look at where the fixed gear joins the fuselage on all three examples, Lancair, Cirrus and Cessna. 3. Retract adds a lot of weight, complexity, and size to the plane. Increasing the size of the wings, fuselage, or the join between the two increases drag.
So ya, the impact at the slower speeds these planes fly it really is not that big a hit in terms of speed and a very significant cost, complexity and other factors savings.
Tim
Dave,
We agree. I was talking specifically for the SR20/SR22.
Tim
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 15:58 |
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Joined: 12/19/11 Posts: 3307 Post Likes: +1434 Company: Bottom Line Experts Location: KTOL - Toledo, OH
Aircraft: 2004 SR22 G2
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Username Protected wrote: The point is "how much faster would your SR22T be if it were retract?"
That's very difficult to answer unless you have the wind tunnel data with / without landing gear. Everyone here can offer a guess but not really have an accurate answer. Very, very good landing gear designs with optimal wheel fairings do not have a much drag as you might think. I've seen data to show fixed gear drag contribution in the 5-10% range. I worked for Cirrus but don't have the data to show this actual difference and don't know that it even exists. My best guess is that in the flight regime the SR20/SR22 operate that it is probably in the 5-15 kt range. In the early days of the design, they did no wind tunnel testing - it was all computer simulation back then. I don't recall the topic of fixed vs. retract ever even coming up. It was conceived all along to be a fixed gear design for all the reasons mentioned: simplicity, weight, cost.
_________________ Don Coburn Corporate Expense Reduction Specialist 2004 SR22 G2
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:05 |
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Joined: 07/26/10 Posts: 4296 Post Likes: +196 Location: West Palm Beach, FL (KLNA)
Aircraft: 1979 Duke B60
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Username Protected wrote: Why doesn't Cirrus make an SR-22 with retractable gear? Seems to me that it is a great airplane that is really fast, but could be a lot faster with RG. Is that not correct? It would be a big reduction in drag I would think. Guess I could be wrong though. Would definitely be heavier that I know so the UL would go down. Maybe that is the issue. Why bother? they didn't even care to add a steering mechanism which would add complexity, weight and additional drag!
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:08 |
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Joined: 12/19/11 Posts: 3307 Post Likes: +1434 Company: Bottom Line Experts Location: KTOL - Toledo, OH
Aircraft: 2004 SR22 G2
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Username Protected wrote: The gear is also quite important in a landing under parachute. There have been very few significant injuries from chute landings, but one of the significant ones was from a guy who landed in water where the gear had no shock absorber function. That's a very good point as well. The gear play a significant role in energy absorption during a CAPS event.
_________________ Don Coburn Corporate Expense Reduction Specialist 2004 SR22 G2
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:20 |
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Joined: 01/31/10 Posts: 13407 Post Likes: +7490 Company: 320 Fam
Aircraft: 58TC, E-55, 195
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Username Protected wrote: The gear is also quite important in a landing under parachute. There have been very few significant injuries from chute landings, but one of the significant ones was from a guy who landed in water where the gear had no shock absorber function. My first ride in a Cirrus ended with the pilot dropping it in (stall...like we're not flying any more Willis kinda stall) from about 5 feet at night. I expected a few compressed discs and to see the wheels punch through the wings. To my surprise, the gear sucked it all up and made it feel good. There would have been broken parts in any other aircraft I've flown. I bet the wheel pants touched the wings.
_________________ Views are my own and don’t represent employers or clients My E55 : https://tinyurl.com/4dvxhwxu
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:23 |
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Joined: 11/03/12 Posts: 2140 Post Likes: +540
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Isn't the seat pan/pad also designed to minimize compressive spinal injuries from chute landings? Username Protected wrote: The gear is also quite important in a landing under parachute. There have been very few significant injuries from chute landings, but one of the significant ones was from a guy who landed in water where the gear had no shock absorber function. My first ride in a Cirrus ended with the pilot dropping it in (stall...like we're not flying any more Willis kinda stall) from about 5 feet at night. I expected a few compressed discs and to see the wheels punch through the wings. To my surprise, the gear sucked it all up and made it feel good. There would have been broken parts in any other aircraft I've flown. I bet the wheel pants touched the wings.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:36 |
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Joined: 12/19/11 Posts: 3307 Post Likes: +1434 Company: Bottom Line Experts Location: KTOL - Toledo, OH
Aircraft: 2004 SR22 G2
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Username Protected wrote: Isn't the seat pan/pad also designed to minimize compressive spinal injuries from chute landings?
Yes - the seats are dynamically tested seats to 26g. However, the landing gear certainly help absorb energy as well.
_________________ Don Coburn Corporate Expense Reduction Specialist 2004 SR22 G2
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:42 |
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Joined: 08/26/13 Posts: 31 Post Likes: +3
Aircraft: Piper Arrow
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It has to be more than 5 knots going from fixed to retract. I went from a 180HP Cherokee to a 180HP Arrow, and my cruise speed is 15 knots faster.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:47 |
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Joined: 03/10/11 Posts: 849 Post Likes: +260
Aircraft: B95, F33A
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Username Protected wrote: It has to be more than 5 knots going from fixed to retract. I went from a 180HP Cherokee to a 180HP Arrow, and my cruise speed is 15 knots faster. That's true, but the Cherokee is already a slab-bottomed aluminum fuse with cavernous Hershey-bar wings and small gas tanks making it easy to hide the wheels. Not really an apples-to-apples comparison.
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