问GPT, 现在BOEING747都退役了,说4台发动机耗油. 问了它, 改成两台行不行. GPT回答如下:
引用于 minsheng 在 2025-09-28, 下午3:17其实我们知道答案, 就是问问. 停产归停产, 但是很多旧飞机就是便宜, 所以全世界还有小公司, 私人公司, 土豪在用747, MD-80这种经典. 改成货机, 或者空中监狱CON AIR.
Great technical question 👍 Let me unpack it clearly.
The short version: No, Boeing can’t just swap the four engines on a 747 for two big GE90 or GEnx engines.
Here’s why:
1. Design Certification & Structure
The Boeing 747 was designed, certified, and structurally built as a four-engine aircraft.
Engine thrust isn’t just about power — it affects wing structure, weight distribution, fuel systems, hydraulics, and landing gear loads.
Re-engineering it to handle two massive engines would basically require a new aircraft design and certification program, which costs billions.
2. Engine Thrust vs Aircraft Weight
A GE90-115B (used on the 777-300ER) produces ~115,000 lbs of thrust.
Four engines on a 747-8 (GEnx-2B67) produce ~66,500 lbs each → ~266,000 lbs total.
Two GE90s (230,000 lbs total) are less than the original four (266,000 lbs). Not enough thrust margin for a safe 747 takeoff with max weight.
3. Wing Design
A 747’s wings are designed for outboard engine placement to balance lift and reduce wing bending.
With only two inboard engines, the aerodynamic loads change dramatically — the wing would need a total redesign.
4. Economics
Developing a “twin-engine 747” would cost nearly as much as designing a new aircraft.
Boeing already has the 777X, which is basically a modern “twin-engine replacement” for the 747 on many routes — same payload range in many cases, but far more efficient.
5. Regulatory
FAA/EASA certification for a re-engined 747 with only two engines would be treated as an entirely new aircraft type, not just a “variant.”
That means years of testing and costs in the billions — not practical for an aircraft family Boeing already ended production on.
✅ Bottom line:
Boeing can’t just bolt two GE90s or GEnx engines onto a 747 to keep it alive. The economics, engineering, and certification hurdles are too great. That’s why Boeing transitioned to aircraft like the 777X and 787 — they were designed from the ground up as efficient twin-engine jets.
其实我们知道答案, 就是问问. 停产归停产, 但是很多旧飞机就是便宜, 所以全世界还有小公司, 私人公司, 土豪在用747, MD-80这种经典. 改成货机, 或者空中监狱CON AIR.
Great technical question 👍 Let me unpack it clearly.
The short version: No, Boeing can’t just swap the four engines on a 747 for two big GE90 or GEnx engines.
Here’s why:
1. Design Certification & Structure
-
The Boeing 747 was designed, certified, and structurally built as a four-engine aircraft.
-
Engine thrust isn’t just about power — it affects wing structure, weight distribution, fuel systems, hydraulics, and landing gear loads.
-
Re-engineering it to handle two massive engines would basically require a new aircraft design and certification program, which costs billions.
2. Engine Thrust vs Aircraft Weight
-
A GE90-115B (used on the 777-300ER) produces ~115,000 lbs of thrust.
-
Four engines on a 747-8 (GEnx-2B67) produce ~66,500 lbs each → ~266,000 lbs total.
-
Two GE90s (230,000 lbs total) are less than the original four (266,000 lbs). Not enough thrust margin for a safe 747 takeoff with max weight.
3. Wing Design
-
A 747’s wings are designed for outboard engine placement to balance lift and reduce wing bending.
-
With only two inboard engines, the aerodynamic loads change dramatically — the wing would need a total redesign.
4. Economics
-
Developing a “twin-engine 747” would cost nearly as much as designing a new aircraft.
-
Boeing already has the 777X, which is basically a modern “twin-engine replacement” for the 747 on many routes — same payload range in many cases, but far more efficient.
5. Regulatory
-
FAA/EASA certification for a re-engined 747 with only two engines would be treated as an entirely new aircraft type, not just a “variant.”
-
That means years of testing and costs in the billions — not practical for an aircraft family Boeing already ended production on.
✅ Bottom line:
Boeing can’t just bolt two GE90s or GEnx engines onto a 747 to keep it alive. The economics, engineering, and certification hurdles are too great. That’s why Boeing transitioned to aircraft like the 777X and 787 — they were designed from the ground up as efficient twin-engine jets.