Aero Teck
I think tdracer are talking about an 767 and AirCanada did some testing with regards to this from FL410. They did a good 100 plus Nm glide and made Gimli airport famous. No climb. Some sideslip on final as they were high tough.
With regards to test pilots and what they do and dont , with critical testing , extra sensors and engineers involved they do a lot we would never consider.
Super planed.
I have seen some interesting non-standard stuff being pulled off by testpilots.
Checklist , CRM and SOP not a strong side . Great gang , but old boring standard stuff , Naahh.
Murphy has his ways!
But going from testpilot for Boeing to glider pilot in one day ,
As one testpilot once told me with a blush; We testpilots make mistakes too!
( Turned out the engine started much better with the firebutton in again, as we had just concluded it worked as intended when pushed and released!)