warrior29
Senior Heliman
Location: FL
| Yes looping and rolling can be performed while maintaining postive G's throughout the manuever, which means it could be be performed by most helicopters, if performed correctly.
With an underslug rotor system such, as the Huey and Cobra unloading the rotor system during low G manuevers can cause a condition known as mast bump. This is when the rotor head comes in contact with the mast. This usually leads to a catastrophic failure of the rotor system.
The aircraft that you mentioned, the 680, 500 and the daulphin have semi-articulated rotor systems. The gazelle, lynx and BK I believe all have fully articulated system. This is what gives it the manueverablity to actually pull limited negative G's. Notice I say negative G's, which constitutes higher degree of manueverablity.
A loop and roll have not all the aerobatic, a 747 has been rolled and a CH-53 has been looped and rolled. Getting back to how this discussion started about 3D you must look at the pitch and roll rates of the aircraft. I could not quote you roll rates of other helicopters but I speak specifically about the AH64 which has a roll rate of 60degrees/sec. This is about the same as the roll rate of a F-16. Yaw rates are limited to 60 degrees/sec due to structural limitations. This means when I roll an Apache it will roll out with no significant loss of altitude (this was flight tested and proven by McDonald Douglas, now Boeing in 1988). Roll a CH-53 you better have several hundred feet below you because it will take all day be for the dirty side points down again.
I demonstrate high low G manuevers in the Apache almost on a daily basis. It is capable of up to of +3.5 G's to -.5 G's. Test where performed by MD Test Pilots years ago to test these manuevers prior to the 88 Farnbourgh Air Show. The rotor blades did come within 6 inches of the tail boom during the manuever but never made contact.
I seriously doubt that the H-19, H-34 or any of the older birds ever went completely inverted because of mast bump, but those old guys were kind of crazy and sure as I say it didn't happen someone will prove me wrong. But I have flown everything from TH-55, Jet Rangers, MD 500, Daulphins and Apaches, and I you wouldn't catch me trying it in anything that was designed to do it.
60 degrees nose down makes stuff float in the cockpit. Looking nearly straight down at the ground rushing up to you is always a blast. |
