In 2015, I contracted Ken Krueger, of Sky Designs Engineering, to perform a preliminary feasibility study on a taildragger version of the RV-10. Ken was fantastic to work with and I thoroughly enjoyed the opportunity to speak with him.
To quote Ken: “The idea of a taildragger RV-10 does not seem so far fetched as to be unfeasible but there will be some unknowns.”
Perhaps this may inspire someone, already inclined towards taildraggers, to pursue this project.
Here is the response from Ken discussing the initial layout decisions as well as further thoughts and concerns:
“RV-10 TD Preliminary Configuration Study Results
Prepared by: K. Krueger
Revision: 0 Date: 07-10-15
Customer contacted Sky Designs asking if it would be possible to modify the RV-10 design from a tricycle landing gear configuration to a conventional or “taildragger” landing gear configuration. The taildragger RV-10 shall in this summary be referred to as the “RV-10TD”.
The following decisions were arrived at during the initial telephone discussion with the customer:
The preferred way to mount the main landing gear of the RV-10TD would be to use tapered steel rod legs supported in tubular sockets that are integrated into the engine mount. This is the “typical” main landing gear configuration for most RV aircraft and is a well proven and well understood way of attaching main landing gear. This was chosen for reasons of both the overall look of the aircraft and for simplicity as attaching the main landing gear in this way requires the least amount of new parts to achieve the taildragger configuration compared to the tri-gear configuration.
A preliminary landing gear layout was made and the following preliminary design decisions were made:
6.00-6 tires (17.15 inch diameter) will be used on the RV-10TD instead of the 6.00-6-15 (15.00 inch diameter) tires of the tri-gear RV-10.
7 inch diameter tailwheel. An 8 inch diameter tailwheel was considered but that would have resulted in a shallower angle in the 3 point landing attitude.
The length of the main gear legs and fore/aft location of the wheels was chosen to be the best
compromise between providing a reasonable 3 point landing attitude, adequate prop clearance, and reasonable ground handling characteristics.
The 3 point landing attitude angle chosen was 11 degrees. It would have been nicer to have 12 degrees but that would have resulted in even longer main gear legs and their length is already a concern as rod-type gear legs have a greater tendency to “shimmy” the longer they are.
The main wheel centers were located 1.5 inches forward of the wing leading edge. It would have been preferred to locate the wheels closer to or even with the leading edge but that, again, would have resulted in even longer main gear legs.
Prop ground clearance is quite adequate at 15” (FAR Part 23 requires 9 inches prop clearance)
The biggest structural design concern is the sweepback angle of the legs as the RV-10 has a relatively large distance between the firewall and the wing leading edge. The sweepback is more than both the RV-9 and RV-14 aircraft. This landing configuration may work well but it also may have a greater tendency to shimmy than other rod type leg aircraft.
An aircraft design concern is the adverse effect on directional stability that the main gear leg fairings will have as they are small fixed “wings” but being located forward of the aerodynamic center, they are de-stabilizing. The removal of the nose gear fairing will be helpful but the main leg fairings will more than offset the effect of removing the nose fairing. The RV-10 has reasonable directional stability so it may be acceptable to “give away” a little and still have good flying qualities.
A practical concern is that the taildragger engine mount will occupy a different space forward of the firewall than the space that the nosewheel mount occupies. This difference may require re-configuring of the standard arrangement of firewall forward items. The location of the oil cooler on the firewall will almost certainly be different for a taildragger RV-10 since the sockets for the rod type main landing gear will need to be where the oil cooler is. There will certainly be other changes but the oil cooler is the only one I know of at this time.
The main gear legs can be expected to be about two inches in diameter at their max diameter.
The tail spring can be expected to be about one inch in diameter at its max diameter.
The main wheels and brakes in the standard RV-10 kit can be used.
A new engine mount will need to be developed.
New main landing gear legs will need to be developed. The brake mount flanges in the standard RV-10 kit can be used.
A tail spring mount will need to be developed and integrated into the aft fuselage. The tail spring mount would, ideally, be the same design concept as the well proven WD-409 tail spring mount. Similarly, a new tail spring and tailwheel mount will need to be developed.
Retractable ground handling “handles” will need to be developed and integrated into the aft fuselage.”
Here’s a link to the original documents:
https://drive.google.com/drive/folders/1oHfKM9exJAA4JpyyZBobEDjG0_FsEtdS?usp=sharing
To quote Ken: “The idea of a taildragger RV-10 does not seem so far fetched as to be unfeasible but there will be some unknowns.”
Perhaps this may inspire someone, already inclined towards taildraggers, to pursue this project.
Here is the response from Ken discussing the initial layout decisions as well as further thoughts and concerns:
“RV-10 TD Preliminary Configuration Study Results
Prepared by: K. Krueger
Revision: 0 Date: 07-10-15
Customer contacted Sky Designs asking if it would be possible to modify the RV-10 design from a tricycle landing gear configuration to a conventional or “taildragger” landing gear configuration. The taildragger RV-10 shall in this summary be referred to as the “RV-10TD”.
The following decisions were arrived at during the initial telephone discussion with the customer:
The preferred way to mount the main landing gear of the RV-10TD would be to use tapered steel rod legs supported in tubular sockets that are integrated into the engine mount. This is the “typical” main landing gear configuration for most RV aircraft and is a well proven and well understood way of attaching main landing gear. This was chosen for reasons of both the overall look of the aircraft and for simplicity as attaching the main landing gear in this way requires the least amount of new parts to achieve the taildragger configuration compared to the tri-gear configuration.
A preliminary landing gear layout was made and the following preliminary design decisions were made:
6.00-6 tires (17.15 inch diameter) will be used on the RV-10TD instead of the 6.00-6-15 (15.00 inch diameter) tires of the tri-gear RV-10.
7 inch diameter tailwheel. An 8 inch diameter tailwheel was considered but that would have resulted in a shallower angle in the 3 point landing attitude.
The length of the main gear legs and fore/aft location of the wheels was chosen to be the best
compromise between providing a reasonable 3 point landing attitude, adequate prop clearance, and reasonable ground handling characteristics.
The 3 point landing attitude angle chosen was 11 degrees. It would have been nicer to have 12 degrees but that would have resulted in even longer main gear legs and their length is already a concern as rod-type gear legs have a greater tendency to “shimmy” the longer they are.
The main wheel centers were located 1.5 inches forward of the wing leading edge. It would have been preferred to locate the wheels closer to or even with the leading edge but that, again, would have resulted in even longer main gear legs.
Prop ground clearance is quite adequate at 15” (FAR Part 23 requires 9 inches prop clearance)
The biggest structural design concern is the sweepback angle of the legs as the RV-10 has a relatively large distance between the firewall and the wing leading edge. The sweepback is more than both the RV-9 and RV-14 aircraft. This landing configuration may work well but it also may have a greater tendency to shimmy than other rod type leg aircraft.
An aircraft design concern is the adverse effect on directional stability that the main gear leg fairings will have as they are small fixed “wings” but being located forward of the aerodynamic center, they are de-stabilizing. The removal of the nose gear fairing will be helpful but the main leg fairings will more than offset the effect of removing the nose fairing. The RV-10 has reasonable directional stability so it may be acceptable to “give away” a little and still have good flying qualities.
A practical concern is that the taildragger engine mount will occupy a different space forward of the firewall than the space that the nosewheel mount occupies. This difference may require re-configuring of the standard arrangement of firewall forward items. The location of the oil cooler on the firewall will almost certainly be different for a taildragger RV-10 since the sockets for the rod type main landing gear will need to be where the oil cooler is. There will certainly be other changes but the oil cooler is the only one I know of at this time.
The main gear legs can be expected to be about two inches in diameter at their max diameter.
The tail spring can be expected to be about one inch in diameter at its max diameter.
The main wheels and brakes in the standard RV-10 kit can be used.
A new engine mount will need to be developed.
New main landing gear legs will need to be developed. The brake mount flanges in the standard RV-10 kit can be used.
A tail spring mount will need to be developed and integrated into the aft fuselage. The tail spring mount would, ideally, be the same design concept as the well proven WD-409 tail spring mount. Similarly, a new tail spring and tailwheel mount will need to be developed.
Retractable ground handling “handles” will need to be developed and integrated into the aft fuselage.”
Here’s a link to the original documents:
https://drive.google.com/drive/folders/1oHfKM9exJAA4JpyyZBobEDjG0_FsEtdS?usp=sharing
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