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Bell 206/OH-58 Differences

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Bell 206/OH-58 Differences

Old 2nd Jan 2018, 16:19
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Join Date: Mar 2005
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Bell 206/OH-58 Differences

Any one with any idea what drove the two types to have different rotor diameters and different rotor RPM? Were the transmission casing the same, also tail gear box? Obviously different ratio gears in the main as engine input was the same 6,000rpm.

Thanks all, wondered for years having flown both.
megan is offline  
Old 3rd Jan 2018, 01:52
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I don't know too much about the OH-58 and how the differences came about but military and commercial variants of a supposedly common design can differ enormously. From my experience with the Bell UH-1 and Bell 205 helicopters I can tell you that only the silhouette is the same, thereafter everything is different, even the engines and the rivets. Horses for courses.
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Old 3rd Jan 2018, 05:18
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4 seats to 5, smaller petrol tank, no tail drive or tgb cowls etc
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Old 3rd Jan 2018, 06:18
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I know in Oz someone managed to get a lot of 58 bits into a 206.

The resulting vibration from incorrect NR and other issues and the intervention of
the authorities caused a lot of expensive parts to be thrown away!!

Bell are probably kicking themselves that they didn't make the parts just slightly different so they wouldn't physically fit.

A lit of PMA parts were manufactured with data from the DoD info in the "public domain" and reverse engineered.
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Old 3rd Jan 2018, 10:07
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Join Date: Dec 2007
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Apparently, the original OH-58A (1967) had 44 different modifications carried out on the airframe to convert it from the Bell 206A into the then new LOH. Some of the bigger changes included a longer main rotor blade and extended tailboom.

Lots of US Army test reports here that might be of interest.


500 Fan.
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Old 4th Jan 2018, 01:27
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Join Date: Dec 2003
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Some info here:


Though similar in appearance to the civil Bell 206A JetRanger, the OH-58A has significant differences and few parts are interchangeable between models. The Kiowa’s main rotor blades and tail boom are longer than the JetRanger’s. The rotor system turns at a slower r.p.m. Landing skids are mounted differently. The OH-58A has a lower maximum gross weight. There are internal differences as well, for example, the main transmission of the OH-58A has only three planetary gears while the 206B uses four, giving it a greater torque capacity.
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