simjim From El Salvador, joined Aug 2011, 18 posts, RR: 0 Posted (3 years 2 months 2 weeks 3 days 21 hours ago) and read 5741 times:
I recently saw a photo of the GE 747-100 Test Bed Aircraft flying with one GEnx engine and wondered what the CASM would be for the 747-8I, if you placed three GEnx engines and one CFM56-7B27 (738 engine) on it?
On a 4,000 nm mission, fully loaded with passengers and cargo, do you think it would be less efficient, more efficient or about the same as a 77W flying the same mission?
B777LRF From Luxembourg, joined Nov 2008, 1772 posts, RR: 4
Reply 1, posted (3 years 2 months 2 weeks 3 days 15 hours ago) and read 5604 times:
I think it would never be allowed to leave the ground, but if it did it would be with a take-off weight so restricted it wouldn't even by funny. Imagine if you loose one engine right after lift off, and that engines happens to be a GEnx on the same side as the puny little CFM. You'd be in a world of pain unless you're a bonafide test pilot, which very few airline pilots are.
An operation such as the one you suggested falls under "test flight" not "commercial revenue generating" ditto.
From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove
Stitch From United States of America, joined Jul 2005, 33654 posts, RR: 85
Reply 2, posted (3 years 2 months 2 weeks 3 days 12 hours ago) and read 5499 times:
Quoting simjim (Thread starter): I recently saw a photo of the GE 747-100 Test Bed Aircraft flying with one GEnx engine and wondered what the CASM would be for the 747-8I, if you placed three GEnx engines and one CFM56-7B27 (738 engine) on it?
It would be higher because you'd be payload-restricted so you couldn't fill all the seats.
Quite simply, the 747-8 has four GEnx1B-67 engines because it needs four GEnx1B-67 engines.
PapaChuck From United States of America, joined Aug 2010, 136 posts, RR: 0
Reply 3, posted (3 years 2 months 2 weeks 2 days 12 hours ago) and read 5103 times:
The easiest and most cost-effective solution would be to de-rate all four GEnx engines and file the paperwork to operate at a reduced MTOW. Airlines do this all the time when they don't intend to exploit an aircraft's full capabilities.
Edit: Better yet, just get your hands on an aircraft tailored to the type of routes you intend to fly. A 777-300 (non-ER) can carry a full payload close to 4000 miles. Why go through the headache of modifying a 747-8 to do something it was never intended to do when you can just buy the right airplane for the job in the first place?