Hola Mathy - re. the "steady on" BelArgUSA here above, and SFCs...
xxx
I have used engine SFC as instructor when I was in classrooms.
The figures used were provided from reliable source, i.e. engineering.
xxx
Our flight crews were briefed about the SFC of engines.
This as an alternate means of setting takeoff thrust.
Engines normally using EPR can use N1 as approved alternate power setting.
But we also provided the SFC as a NON-approved method of "crosscheck".
I wish the Air Florida 737 crew with iced PT2 had been in my class.
xxx
My 747 crews knew the JT9D-7Q fuel flow of 19,000 lbs for 53,000 lbs thrust.
That JT9D has an SFC of .36 - Just a crosscheck... agreed...?
So it looks that I am not comparing apples and oranges.
I used SFC in the above manner through my career as pilot and instructor.
xxx
As I recall, having flown and taught various airplanes, my notes show -
JT8D (727 or 737) as .58 SFC, no reason the DC9's is any different;
JT3D (707 or DC8) as .53 SFC, their JT4Aa were .75 SFC;
CFM53 (DC8) as .35 SFC, no reason the A320's - 737's CFMs to be different.
JT9D (747) as .36 SFC...
CF6E and RB211 (in 747) are about same .34-35 class SFC.
xxx
Incidentally - if you compare flight total fuel burn comparisons at random.
The SFC factors gives you a very good yardstick.
The 707 with JT3D (.53) used about 2/3 of the fuel of 707 with JT4A (.75)...
So, Mr. Mathy... review your statement about the JT8D...
xxx
The above comes from PanAm, an airline you might not recall, of little value.
And I continued teaching same in a "third world nation" of South America.
In the country you are, you have more accurate/superior expertise.
I wonder how we, were lucky not to crash with our defective knowledge.
xxx
Respectful cheers, too... or "salud"
Happy contrails