Boeing 747 engines compared

A turbofan works by throwing a large mass of air backwards slowly, most of it bypassing the hot core entirely. It is quieter and more efficient than the pure turbojet it replaced, and it is the reason the 747 can cross an ocean economically.

The question this page answers is: what do you get when you put three different turbofans under the same wing?

The engines and the aircraft they powered

Engine family	Typical thrust	747 generations
Pratt & Whitney JT9D	~46,000–50,000 lbf	747-100, later -200 and -300
General Electric CF6	~53,000–63,300 lbf (later variants)	747-200, -300, -400
Rolls-Royce RB211	~56,500–63,300 lbf (G/H models)	747-200, -300, -400
Pratt & Whitney PW4000	~63,000+ lbf	747-400
General Electric GEnx-2B	66,500 lbf	747-8 only

The JT9D

The 747-100 had one engine choice, and the choice was the JT9D — the first high-bypass turbofan on a commercial airliner. It was rushed to meet the programme schedule, and its early reliability was bad enough that the first 747s were nearly grounded.

Later models — especially the JT9D-7R4 — fixed the worst of the problems, but the reputational damage was enough that airlines asked for alternatives. The JT9D’s difficult start is the reason the 747-200 offered three engines. It is also the reason Pratt & Whitney needed the PW4000 for the 747-400 generation.

The CF6

General Electric’s high-bypass turbofan arrived in the 1970s and proved reliable and flexible. On the 747 it spanned the entire family from the -200 to the -400, in variants including the CF6-80C2 — a workhorse that powered thousands of 777s and A330s as well.

The RB211

Rolls-Royce’s entry was the three-shaft high-bypass engine: a design that gave it an unusually smooth power delivery and a distinctive high-pitched whine. The RB211-524G and -524H, available from the 747-400, delivered similar thrust to the CF6-80C2.

Why three engines mattered commercially

Three things did the work:

• Risk management. No airline betting a billion dollars on a new aircraft wanted a single-source engine. Three options meant three competing proposals.
• Customisation. Pacific carriers flew different missions from Middle Eastern ones; different engines suited different routes.
• Commercial leverage. Three manufacturers competing kept pricing and delivery honest — and this was the programme’s commercial problem-solver.

The 747-8 reversed this. A GE exclusivity agreement meant the GEnx-2B was the only engine available, for at least ten years — the exact opposite of the strategy that had made the 747-200 a commercial success.