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744 vs. 748 - ops

Started by Aleks, Sat, 6 Jan 2024 15:17

Aleks

I wonder what is the difference between 744 and 748 from a pilot perspective.

I have googled and read on technical differences, but couldn't find any pilot insights.

If any of you 744/748 can share your thoughts, it would be interesting to hear :)

boeing747430

Hey Aleks!

Could you elaborate, please? What information is it, you're after?

Best regards,
Kim.

boeing747430

#2
Ok, I give it a try:

I only fly passenger 744/748s. Basic manual flying, I prefer the 744. She feels more "honest" and has no fly by wire at all. Boeing tried veeery hard making them feel similar, but there are still slight differences. The wing is the thing. Landing-flap-setting-wise, there is only a very small difference in flying a 748 on F25 vs F30. It is more pronounced on the 744. Crosswind-wise, the 748 feels more sensitive than the 744, but that may be different on the freighter with its short upper deck. The 742 was much easier to handle in strong crosswinds than even the 744. A combination, I think, of the shorter upper deck and the missing winglets with the shorter wingspan. Rumour has it, that Boeing discovered only quite late during the 748's development, that F30° would give it a negative pitch for approach. Hence, they reduced the extension for F30° until they got a pitch close to the 744s, which is why the extension for F25° is very similar on the 748. Leading edge flap extension sequence is slightly different between 744 and 748, but then again, 741s 742s and 743s had a slightly different sequence from the 744 and 748 and no FOD leading edge flap retraction feature during thrust reverse.

Then they had flutter from an interference in airflow between the wing gear doors and the inboard flaps, which led to a smaller "fold"-angle at the the wing gear doors of the 748 compared to the 744. Also, there were some flutter issues with the horizontal stabilizer, which needs to produce more nose up momentum on the 748. How exactly they fixed this, I'm not sure. Perhaps somebody else knows.

748s are much better gliders. When it comes to calculating descents, you better go for 3 1/2 times altitude, instead of 3 times on the 744. On the 748, you can go all the way to max rec alt. On the 744, you better leave the wing some 1000' margin, especially in turbulence. Initial climbout is usually flatter on the 748. She also starts to fly off the runway with less pitch and there is less of a difference between initial pitch for one engine out vs all engines.

For takeoff with the 744, Boeing certified a "one pack on" takeoff performance option, which is what we usually use. Apparently they did not go the distance for the 748. Here, I can only go for all packs on, which would be the normal option, packs off, or packs to APU, the latter being really only pack 2 to APU and this being the option for performance issues on short runways, or during hot and high operation.

Engine out during takeoff on the 748 gives you some support from the spoilers when you jump into your rudder pedal. They call the spoilers "spudders" for this occasion. There is some augmentation from the spoilers and the elevator for some situations on the 748, but you cannot tell under most circumstances.

Ground maneuvering is a bit more tricky on 748, of course and one has to be aware that those engines produce a lot of idle thrust. Still, it always amazes me, how easy they are both to taxi. Slightly bigger tires on the 748 and cooling outlets on the bottom of the fuselage for the galleys. Also, a RAT, of course. Wing tip marker lights on the 748.

Personally, I'm not a huge fan of the electronic checklist. With complex non-normals, I find it easier to navigate through several open checklists with a QRH. The PTT-Button on the outboard glare shield is a nice feature on the 748. I miss a proper clock on the 748. While we did get the NG FMS upgrade, my company left the old CRTs installed on the 744, which is why the MCDUs are still all green, but I don't miss the different colours one bit. The airport map on the ND of the 748 is a nice feature to have. The interphone on the 748 is more sophisticated but also more complicated to use.

When it comes to fuel burn, the 748 is even better than the flightplan performance models we got from Boeing. She tends to burn almost two tons less fuel on a 12 hour flight than calculated. Still, the 748 fuel burn is very sensitive when it comes to CG. Also, I hear, that the long upper deck gives the -8i a bit better aerodynamics as opposed to the 8F, so less fuel burn at similar weights - a phenomenon it shares with 747-400 pax vs 747-400F.

That's it for now.

Best,
Kim.

Aleks

Thank you for great insights, Kim.

Exactly what I was looking for.