We all know about EPR... on Pratts (like the MD-80s) and Rolls noise machines...
We have N1 as an alternative (if EPR is dead) or as a crosscheck.
And if these guys had a good ground school, they would know what FF it takes to get "about" 19,000 lbs (?) thrust.
xxx
I knew what it took (as FF) on ALL engines types I had on my 707s, 727, or DC-8s...
On the JT9D-7Q (747s), it takes 9,000 kg FF (19,850 lbs FF) to get full thrust.
That is the gage I would look at, to crosscheck EPR/N1 in case of doubt.
(Or if either EPR or N1 is MEL'd) -
xxx
Sorry - I do not know the TSFC of the JT8D-217/219s...
I would say - probably around 4,300 kg FF...?
xxx
Sad contrails