Curyfury Posted January 4, 2016 Report Share Posted January 4, 2016 Been under the assumption that counter clockwise main rotors have tail rotors on the left side like the r22 and opposite for aircraft like the eurocopter. But i just noticed a cal fire huey that seems to have a counterclockwise main rotor with the tail rotor in the right side. Then i googled images of hueys and found other examples of the same, so it wasnt an illusion. Wouldnt that mean the tail rotor is directing its thrust into the vertical stabilizer? Im no mechanical engineer, but that seems inefficient and contrary to logical design. Anyone have design insight as to why? Quote Link to comment Share on other sites More sharing options...
Gomer Pylot Posted January 5, 2016 Report Share Posted January 5, 2016 Tail rotors have been mounted on all sides, and in both rotational directions, seemingly at the whim of the designer. Each placement has advantages and disadvantages, but having the advancing blade on the bottom seems to help with tail rotor authority, IIRC. This has the downdraft from the main rotor helping, rather than hurting, the lift from the tail rotor, and has more effect than whether it's a pusher or tractor design. This isn't a simple, cut-and-dried design choice. Quote Link to comment Share on other sites More sharing options...
AS350 pilot Posted January 5, 2016 Report Share Posted January 5, 2016 If you are looking at "huey's" then you will see them on both sides. The original H models have the tail rotor on the aircraft left side. However, 205's and 212's have the tail rotor on the aircraft right side. That being said, some H models have been converted….as you noticed with the cal fire ships. You might also notice some huey's have a cutaway vertical stabilizer. This is an STC called the fast fin. Things like this happen when you have such a great airframe for such a long time. The design gets tweaked. Quote Link to comment Share on other sites More sharing options...
iChris Posted January 5, 2016 Report Share Posted January 5, 2016 (edited) Been under the assumption that counter clockwise main rotors have tail rotors on the left side like the r22 and opposite for aircraft like the eurocopter. But i just noticed a cal fire huey that seems to have a counterclockwise main rotor with the tail rotor in the right side. Then i googled images of hueys and found other examples of the same, so it wasnt an illusion. Wouldnt that mean the tail rotor is directing its thrust into the vertical stabilizer? Im no mechanical engineer, but that seems inefficient and contrary to logical design. Anyone have design insight as to why? As stated in Gomer pylot’s post above it’s mostly compromises and trade-offs. That’s correct, it does reduce the effective net thrust of the tail rotor, since the induced velocity below the tail rotor is higher than above it, the drag is higher if the tail rotor is blowing against the vertical stabilizer. Therefore, most U.S. type counterclockwise main rotor helicopters have the tail rotor on the left side of the stabilizer. With respect to U.S. type counterclockwise main rotor helicopters, the tail rotor on the left is called the “Pusher” and on the right the “Tractor”. However, with helicopters there’s compromises, and trade-offs to be made. It was discovered late in the game that the direction of rotation was also important and that the tail-rotor rotation should have the blade closest to the main rotor going up. This minimizes main-rotor to tail-rotor interference and the unsteadiness of left sideward flight, as the tail rotor operates in the vortex ring state. Significant improvement resulted from this preferred direction. It was found after the fact, that Bell chose the wrong direction for the early UH-1 and AH-1. Bell’s solution was to flip the tail-rotor installation from the left side of the fin to the right, using the same hardware, since the blades were symmetrical airfoils without any blade twist, redesign was not necessary. The net results, better performance. you have the Bell 212, 412, and the rest of the upgraded UH-1s, 205s with tail rotors on the right side, rotating in the preferred direction, with the blade closest to the main rotor going up. For a different reason, the UH60’s tail rotor is on the right too. Sikorsky chose to tilt the tail-rotor shaft so that part of its thrust helps lift the rear end of the helicopter. In order to provide clearance with the fin without using a very long drive shaft, the tail rotor was placed on the right. Then you have the very successful MD 500 series which has the tail rotor on the left side; however, not rotating in the preferred direction. The designers didn’t find it to be a significant problem, so we have the blade closest to the main rotor going down. It’s all compromises, and trade-offs. Edited January 5, 2016 by iChris 1 Quote Link to comment Share on other sites More sharing options...
Guest pokey Posted January 5, 2016 Report Share Posted January 5, 2016 then there was the Notar, they had no clue which side to put it on, so? they did away with it alltogether 1 Quote Link to comment Share on other sites More sharing options...
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