Originally Posted by
flyinryan
Here's the real reason: any/all of the following things could be on the tarmac surrounding the aircraft at Gate 79:
Ground vehicles (baggage, tugs, fuel)
Misc other equipment
Ramp workers
Passengers
Read again: Ground idle leads to jet exhaust velocities of less than 35 mph. You'll agree that everything mentioned by you can withstand a wind speed of 35 mph.
As said earlier: I've been running around and working behind a
triple3 with both engines running, sometimes there were less than 40 feet between me and the nozzle. Just hot air - enriched with carbon dioxide. Nothing more.
Exhaust velocities of axial flow turbines will become dangerous only when you go to high EPRs - at 100% N1 you should
not be only 40 feet behind the exhaust, better make it a 1000 feet. The relationship exhaust velocity - % N1 is by far not linear.