I leaned many things about planes in my aviation career. And often, I studied "rules and facts" that I found to be erroneous later with other airplanes. Fuel feed configuration is one of these subjects. Each airplane is "specific", there is NO GENERIC way to operate an airplane's fuel system.
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I started my career with PanAm, first position was F/E on 727... Was my first "big plane"... The ground school instructors were good, we swallowed all they said as gospel from the bible. I remember them saying "you feed fuel from tank to engine for takeoff"... "on a Boeing, you cannot transfer fuel from one tank to another"... "you keep the crossfeed line pressurized"... "all boost pumps ON for takeoff and landing" were the many words highlighted in my manuals.
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Then I had to learn the 707 and 720... was great... just many more tanks, lots of more fuel, and the basic rules studied for the 727 were applicable to the 707/720. Was almost like a difference course more than a new initial... And I honestly believed ALL PLANES were like that...
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For the next 12 years or so, I got to fly the 707 and 727s... from F/E, then F/O, then captain... very little study to do, nothing new, except flying 707 or 727 airplanes coming from other airlines, and learning where the switches were. Different weights, different limitations, different red lines on EGT... "dash this" and "dash that" for engines...
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Then flying on a contract with 707s as captain, the company had good and bad news for us 707s crews... "We lost the 707 contract" (oh oh! - is it a loss of a job, and furlough again) - No... it was not, we were going to be trained on DC-8s...
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My next fear was - "Well, never flown a DC-8, so THEY will put me in the F/O seat for a few months"... and fears of a reduction in salary... Was not the case. I was going to check-out as captain immediately, despite no experience on DC-8 type.
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So we went to ground school again. This time was United in Denver. Different manuals and procedures, different vocabulary for the Douglas machines. And completely different fuel system than Boeing. No sleeping in the classrooms. We had to study this Douglasosaurus. In a DC-8, we could transfer fuel from any tank to any tank, or to any engine. Sure, it was tank to engine for takeoff and engine (finally a similarity) but NO BOOST PUMPS ON for takeoff and landing... Had to highlight lots of differences...
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So I flew a few years with the Diesel-8, going back occasionally on the 707 for other contracts... Then finally back to PanAm, on the 727... and the 747, the whale... What a delight to study the 747... was like a big and fat 707, with all the advanced systems of the 727... a delight to study... And the 747 turned out to be the easiest airplane to handle, of all the types I flew.
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But the Boeing "rules" on the 747 were at times different. I learned that "tank to engine" did not apply for takeoff. Inboards were to be "tank to engine", while outboard engines were fed from the CWT... And that you could "transfer fuel from any tank to any tank" using the jettison system. Then it was "empty reserve tanks 2 and 3 after takeoff - keep reserve tanks 1 and 4 full until the end of cruise"...
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NO GENERIC airplane to explain fuel systems. All planes are different.
In my F/E and F/O days, I flew the Learjet as type rating CFI to make extra money. Fuel management was quite a bit different with these machines as well, and many differences within the 20 series, 30 series, and the 55... They did not have "crossfeed" - they had "crossflow"... jet pumps... And worse, the maximum ZFW included the weight of any fuel in the fuselage tank. In a Learjet ZERO FUEL INCLUDES FUEL... sounds like Hebrew to me...
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Happy contrails