On the subject of engineers doing full bore ground runs. Back in the day at LGW in the 70's, two of us would fire up a Britannia and taxi it to the west end of the airport via the taxi way for part or full bore ground runs. When finished, we would call the tower for permission to return via the main runway. Permission was eventually granted and told to make our journey quickly. So, Locks dropped, brakes off, inboard advanced to achieve about 60 knots then back to brake dwell or reverse in order to make a sedate return to the stand. Shut down and off to Eddie's for tea!!
happy days