Originally Posted by
JohnDixson
Re CC Post 423. Comment: the low speed agility requirements in existence when the UTTAS requirements were published might have been met by the UH-1! But there were other maneuverability requirements that were more demanding, and of course meeting those led to a vastly more capable low speed aircraft. Let me be direct: there is no way that sideways tandem can outmaneuver the UH-60 at slow speed.
Just a follow-up: Sans posted the new ADS-33 handing requirements, and I wonder which category applied to the 280, if anyone knows.
I should add: every helo configuration brings with it some compromises. That is true for the single rotor as well as the tandem, be it fore/aft or lateral. My comment re the low speed maneuverability comparison is not a shot at the Bell designers-they are good troops-its simply noting the fallout of the relative compromises one inherits with the selected configuration.
John, for what it’s worth, the V-280 video appears to show a 45 degree yaw maneuver in about 2 seconds, so ~22 deg/sec (I didn’t do a frame by frame level analysis). Based on the table Sans also posted, sounds like they’re shooting for Level 1 of the “Moderate Agility” classification. The “Aggressive Agility” class seems tailored for a scout aircraft. I don’t know what the UH-60 yaw rate in a hover is, but I recall a design requirement of 15 deg/s yaw in a 35 knot wind, so perhaps it’s 20-some odd deg/s in a no wind hover.
Yaw (and roll) inertia are certainly high on a tiltrotor, but Bell is clearly trying to address this by a large increase in flapping capability. Additionally, every pound removed from the nacelles is enhanced agility, so I’m sure the rotor, drive, and nacelle teams are feeling the steely-eyed gaze of the mass properties engineers.