22 May 2025, 01:26 [ UTC - 5; DST ]
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:53 |
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Joined: 07/20/08 Posts: 1734 Post Likes: +381 Location: KFOK Westhampton, NY
Aircraft: 1978 V35B, Navy N3N
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It would just look faster and better with the wheels up. No practicality implied Imagine a fixed gear Spitfire ? 
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 16:54 |
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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: 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. A bit apples and oranges. Look carefully at the design of the fixed gear on the Cherokee compared to the fixed gear of the SR22/SR20. There's a big difference in the aerodynamics between the two.
_________________ Don Coburn Corporate Expense Reduction Specialist 2004 SR22 G2
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 17:08 |
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Joined: 03/30/11 Posts: 4152 Post Likes: +2920 Location: Greenwood, MO
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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. Given the choice, I think I'd rather land on the Bonanza gear.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 17:10 |
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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. Given the choice, I think I'd rather land on the Bonanza gear. Vertically?
_________________ 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, 17:18 |
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Joined: 03/30/11 Posts: 4152 Post Likes: +2920 Location: Greenwood, MO
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Username Protected wrote: Given the choice, I think I'd rather land on the Bonanza gear. Vertically? Well, at the same rate of descent. Don't you think it's pretty robust? I'm basing my opinion on anecdotal accounts of rough landings.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 17:36 |
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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: Biggest thing I've learned from this thread is that a fixed gear design may allow a more efficient wing than otherwise possible. In that setting the usual fg vs rg comparisons really don't hold. I don't believe that's entirely an accurate statement. Comparing efficiency of wings is more about comparing airfoil designs, wing taper, flap design, wing loading, etc. The Cirrus has an efficient wing primarily due to it's laminar airfoil and high lift flaps. The impact of a retractable gear on wing design is simply designing the wing root to be deep enough to allow for the gear. This is not that difficult to do and not a huge determining factor on wing efficiency. The bigger impact is as it relates to fuel volume since the retracts take up a considerable space that could otherwise be used to store fuel. Weight, cost and complexity are the bigger factors.
_________________ Don Coburn Corporate Expense Reduction Specialist 2004 SR22 G2
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 18:38 |
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Joined: 05/03/12 Posts: 2279 Post Likes: +704 Location: Wichita, KS
Aircraft: Mooney 201
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Username Protected wrote: Curiously lancair came to the same conclusion about gear. So did cessna with the NGP project. Whatever the reason it must be compelling to have three separate teams reach the same solution to a problem that had previously uniformly been solved with RG. The Columbia/Corvalis was originally lofted to accommodate an RG mechanism with the main gear folding much like they do on the Lancair IV planes into the fuselage. The metallic structure that mounted the gear legs could be easily changed (design-wise, not retrofit!) to have the legs pivot. There were loose plans to make 200 and 300 HP versions as well RG and turbo. Fixed gear, 300 HP was chosen first to beat the Cirrus SR-20 in performance while keeping everything as simple as possible. Of course the company struggles precluded developing the other versions after the turbo... and modern sales figures for all piston singles show an extreme bias towards the higher HP versions if there is a choice, so IMO releasing a 200 HP variant would have been a losing proposition. I agree with the assessment that the juice just isn't worth the squeeze for this class of plane, and that the speed difference would be in the neighborhood of 5 knots at equivalent weight when considering well-faired fixed gear. I also agree that fixed gear looks silly on a high performance plane, but it is what it is!  I'm happy with the my relatively simple retractable gear in my Mooney. Don C's post right above me is excellent too.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 18:44 |
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Joined: 05/03/12 Posts: 2279 Post Likes: +704 Location: Wichita, KS
Aircraft: Mooney 201
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Username Protected wrote: The impact of a retractable gear on wing design is simply designing the wing root to be deep enough to allow for the gear. This is not that difficult to do and not a huge determining factor on wing efficiency. The bigger impact is as it relates to fuel volume since the retracts take up a considerable space that could otherwise be used to store fuel. Weight, cost and complexity are the bigger factors.
I'll add a couple more points to the impact of RG design, especially in relation to composite airframes and especially wings. If the gear folds into the wing cavity AND the pivot points/mounting structure is in the wing as well, then the very high and discrete loads from the gear mounting have to be accommodated in the wing spars and this becomes a substantial issue with composite structure. Composites generally suck at handling fastener bearing loads when compared to metallic materials. To absorb the gear loads in the shear web of a wing spar, for example, you would have to add a lot of extra thickness to the shear web that otherwise isn't needed for wing loads, or spread the load over a large area with lots of fasteners, or a combination of both. This contributes to the weight gain with RG, and often the design space for doing this is fairly small inside the wing.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 18:55 |
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Joined: 04/24/10 Posts: 8901 Post Likes: +7317
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Username Protected wrote: The retract adds a lot of cost...
Tim Tru dat. I've just had my gear motor rebuilt and the mechanic has told me my transmission is leaking, prolly needs a rebuild. (Maybe it's a good thing I didn't buy the $34k factory reman, I'd really be done...)
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 19:07 |
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Joined: 11/03/12 Posts: 2140 Post Likes: +540
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All things being equal, I wonder how much less insurance would be on a fixed gear.
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Post subject: Re: Retractable Gear Cirrus Posted: 09 Jan 2014, 19:09 |
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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: I'll add a couple more points to the impact of RG design, especially in relation to composite airframes and especially wings. If the gear folds into the wing cavity AND the pivot points/mounting structure is in the wing as well, then the very high and discrete loads from the gear mounting have to be accommodated in the wing spars and this becomes a substantial issue with composite structure. Composites generally suck at handling fastener bearing loads when compared to metallic materials. To absorb the gear loads in the shear web of a wing spar, for example, you would have to add a lot of extra thickness to the shear web that otherwise isn't needed for wing loads, or spread the load over a large area with lots of fasteners, or a combination of both. This contributes to the weight gain with RG, and often the design space for doing this is fairly small inside the wing. Premier 1? Lot's of composite RG aircraft out there besides Cirrus.
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