Studs, nuts a couple of Ft/lb and a aircraft crash

Plenty of Merlin still flying, and they must be 70 ish years old. The trick is to not expose them to full load, unlike the wat they seem to operate preserved steam, thrash it up the S&C or Shap to break some record or other.

That's exactly what I thought at first, but the Spiralock diagram shows their female is cut full length with a wedge ramp:

The problem, I think, is what the wedge did to a stud that was already torqued close to maximum. As can be seen the wedge concentrates the tightening force on the tip of the male thread, giving it an extra hard time. Good idea, but a step too far on this engine! I wonder if the Spiralock instructions suggest backing off the torque when these are substituted for conventional nuts. If so does the maintenance engineer go with the new nut guidance or what's in the aircraft manual?

Dave

I found the technical report to very interesting, but since when was torque measured in Ft/lbs?

This is a meaningless unit, since torque is defined as force applied at a standard radius and should of course be written as lbft. For ease of visual interpretation it can sometimes include a dot or dash, such as lb.ft or lb-ft. The lb part can even be expanded to lbf denoting pounds force, so then torque is expressed as lbf.ft.

I think our American cousins write it the other way round, as ft.lbs, but not as the version shown in the report.