Re the 8/9/76 11:15PM event at Ft Campbell. Received a call at home 30 min later, and before noon on the 10th a small Sikorsky team led by Bob Zincone (who had taken over development of the UH-60 in January 1975, after three months of flight test) was on the ground at Ft Campbell.
Note: Have three pics that amplify the situation but even though saved as Jpegs-cannot get them to open for transmittal here.
One main blade displayed a peeled back outer surface, initiated at the point where the blade meets the tip cap. That peeling extended maybe 15 ft inboard and some of the Nomex honeycomb was lost with it. Blade aerodynamics changed dramatically.
Crew was flying a simulated infantry lift, with a squad in the cabin with weapons etc.
Flying a a few hundred feet and 145 KIAS or so, the peeling caused immediate and high one per rev vibrations that even made the primary servo caution capsule blink a few times. ( remember, this was prior to availability of NVG’s ). Decision to land immediately was made and they did that, coming down so vertically that the tail rotor took divots out of the same side of a pine tree as they descended. ( Hopefully the picture I have of one of the other three blades having come to a stop against one of the pine trees with a couple of them that had been hit and broken off by the main blades during landing will be available for later viewing-its a saved jpeg and therefore should work here, but doesn’t ).
There was one injury: upon landing the squad leader told the squad to follow him as he was jumping out of the right cabin. BUT, it was dark, and the ship had come down straight alongside one of the pines so the Sgt went about 12 inches and bloodied his nose on the pine tree.
The SA group had brought some gear and did borescoping of the drive train boxes and engines and found no evidence of sudden stoppage. The UTTAS program included a requirement for blade etc replacement capability in the field, so the contingent of Army maintenance folks ( trained by SA-the same sort of group existed on the Boeing side ) unlimbered the portable maintenance crane and started removing/replacing the rotors. Another team of troops from the 101st* arrived with chain saws etc and started clearing the area where the UH-60 main rotor had started a clearing-unintended.
* Ft Campbell is home to the 101st Airborne Division
That work continued into the next day-followed by doing ground runs for main/tail track and balance ( all done by the Army crews ), and on the next morning ( the 11th ) the Army crew flew it back to the cornfield which was the base of operations for the field evaluation. Army flight regulations required a check ride by a standardization pilot for the two aviators involved , so, the Army not yet having same, it was agreed that I play that roie and in order not to mess up their flight schedule, those two checkrides started at midnight ( as I mentioned-this was the 101st ). Those blades and that drivetrain remained with that aircraft.
We found that our manufacturing procedure was at fault. There are three wraps of fiberglass at differing angles which form the outer blade skin. Out at the end of the blade, we had done a straight cut though the skin. The peeling started there. Corrective action was to change the design by folding the skin over and underneath, closing off the edge.