Why does a Boeing 747-8 take more runway length to take off, compared to an Airbus A380?

Question

The Airbus A380 is the largest passenger airliner. That also includes the Boeing 747-8. Meaning, the Boeing 747-8 is smaller than the Airbus A380. As far as I know, smaller planes use less runway length to take off, compared to bigger planes. So, the Boeing 747-8 should consume less runway length than the Airbus A380 to take off, right?

I went to Google, and searched how much runway length is required for a Boeing 747 to take off. The top result showed 3040 m. I then searched how much runway length is required for an Airbus A380 to take off. The top result showed 2900 m.

How is this possible?

Answer 1

This table compares some relevant numbers for the two aircraft:

Aircraft	Airbus A380	Boeing 747-8i
MTOW	575 000 kg	447 700 kg
Wing Area	845 m²	554 m²
Wing Loading	680 kg/m²	808 kg/m²
Thrust	4x 348 kN	4x 296 kN
Thrust / Weight	2.42 N/kg	2.64 N/kg

^{(All values from Wikipedia (A380, 747-8), all at MTOW, standard sea level conditions)}

As you can see, the 747-8 has a slightly higher thrust to weight ratio (about 9% higher), which means it can accelerate a bit faster (at MTOW). However, the A380's wing is much larger resulting in a smaller wing loading (about 14% lower) at MTOW. This results in a lower takeoff speed and therefore reduces the required runway for takeoff.

If you want to compare the takeoff distances at different takeoff weights, I recommend to look at the Airport Planning Documents. These will contain graphs like these:

^{(Airbus Aircraft Characteristics document for the A380, ISA conditions, Trent 900 engines)}

^{(Boeing Airplane Characteristics for Airport Planning document for the 747-8)}

The second graph shows that at MTOW the 747-8 requires a little over 3000 m of runway for takeoff (at sea level). At the same weight (about 448 t), the A380 only requires about 1750 m according to the first chart. This is because it has a much lower wing loading of only 530 kg/m² now. With a 3000 m runway, the A380 can lift off at over 570 t, more than 100 t heavier than the 747-8.

Answer 2

I'd like to add:

_{— Loftin Jr, Laurence K. "Subsonic aircraft: Evolution and the matching of size to performance." (1980).}

Note how there are widebodies that need less runway than some narrowbodies.

If you play around with wing-loading, T/W ratio, and $C_L$, you can get the same or even better result. For instance, the A380 has less wing sweep, which lowers the takeoff distance (increases the $C_L$ in the relation above). Case in point, the A380's indicative performance V2 speed is 150 kts, compared to 175 kts for the 747-8.