flipdewaf wrote:seabosdca wrote:For this aircraft, an oval fuselage isn't an "exotic" feature to leave out when price negotiations get down to brass tacks. It's the core of the business case. Take it away and you have a 767 MAX with pretty wings, which Boeing knows perfectly well has no hope of competing on operating economics with the A321neo.
So the question is...
Does the reduced lift independent drag outweigh both the increase in induced drag due to increased fuselage weight and the reduced versatility of a smaller cargo compartment?
It would definitely be worth the going oval.
Medium to long thin routes usually have very little demand for cargo other than passenger bags. It is highly likely the 797 will not be built for cargo.
A 787-8 taking off with maximum payload weight can only fill its fuel tanks to approximately 65% capacity before hitting MTOW. The 787-8 would struggle to fly between two airports 5000nm apart which is well inside the MOM range window. The 797 could fly that same route but with passengers and bags only in a 3 class cabin.
On a 4000-5000nm MOM range route you can use the 787-8 if you need cargo or the 797 if you dont need cargo. They would compliment eachother nicely, it would be silly for Boeing to build the 797 as a big cargo mover when you have the 787. You would lose efficiency by adding cargo volume to the 797.
Also regarding structural efficiency and weight of an oval: The fineness ratio usually takes the width to length of an aircraft. The 797 of reduced height cross section might have a normal finesness ratio when viewed from the side but a short and stubby A310 fineness ratio when viewed from the top. As the oval would not be as strong when it comes to bending Boeing can simply make it stubby. That is why i think it will definitely be a tight 8ab cross section with a reduced height lower lobe.