Froma an earlier post:
There was one ferry from PHNL to KOSC where the #3 engine was physically removed and placed on the main deck due to bad pylon mounts found during an inspection.
It did take an EO from Boeing and the blessing of the FAA due to the unusual nature of it.
Now that is intriguing. Cue an explanation from a structural engineer at this point: My understanding of pylon mounted engines was that the downforce of the engine's weight protruding out in front of the wing, and spreading its load, via the pylon to the wing spar, helped to stabilize the wing and give it rigidity,
Hence, possibly, the QRH instruction in 75, &76 QRH under "Engine severe damage or separation"
6 If high airframe vibration occurs and continues after engine shutdown:
Without delay, reduce airspeed and descend to a safe altitude which results in an acceptable vibration level.
If high airframe vibration returns and further airspeed reduction and descent are not practical, increasing the airspeed may reduce the vibration.
A bit like a mass balance on a control surface placed there to reduce flutter.
Could it be that only the inboard engines on a 4 engined aeroplane could be removed?
Someone, pleas enlighten me!