Originally Posted by
Easy Street
Seized jet engines definitely create more drag than windmilling. Think of the windmilling engine as offering less resistance to the passage of air; it only extracts enough energy from the airflow to overcome rotational friction (= not a lot at windmilling RPM). The seized engine effectively presents a flat plate to the airflow, so while there is no work done on the shaft, there is plenty done on the whole airframe by the intake-sized airbrake thus ‘extended’. I’ve suffered both types of failure (fortunately in twin-engined aircraft) and the difference in thrust requirement from the remaining engine was very noticeable.
Interesting to hear of your experiences. I suppose the rotational friction includes the ancillaries (pumps, generators etc..) and of course the compressor.
I wonder what the procedure was when ferrying the 5th engine on the 747? But I suppose they may have had problems lubricating the shafts. Similarly for dead engine ferry flights.