LY744 From Canada, joined Feb 2001, 5536 posts, RR: 11 Reply 1, posted (4 years 3 months 6 days 6 hours ago) and read 3139 times:
Like any door/emergency exit issue, this probably boils down to passenger capacity. More exits = more passengers that the aircraft is allowed to carry. Comes into play when an aircraft is stretched, or when an airline decides to use a high-density seating arrangement (e.g. charters).
Viscount724 From Switzerland, joined Oct 2006, 21495 posts, RR: 24 Reply 2, posted (4 years 3 months 5 days 23 hours ago) and read 3052 times:
Quoting Eadc910 (Thread starter): Good Morning! Why did some 707's have ten exits versus the eight exit's. I am talking about the floor level exits behind the wing? I know American and Northwest had some of these, not sure about TWA?
The 707-320C with main deck cargo door had the extra exits behind the wing to meet evacuation requirements in cases where the aircraft may be used in combi configuration with the cargo compartment blocking the use of the overwing exits. 707s without the main deck cargo door lacked those extra exits.
NW's first 5 707-320Bs (N351US through N355US) were a strange hybrid of the all-passenger -320B and the convertible -320C. Although they were built with the main deck cargo door of the -320C, they lacked the extra emergency exits, stronger floor, and other structural reinforcements of the -320C. They're basically just a -320B with a cargo door. I believe that may have been because NW only planned to operate them with a small forward cargo compartment carrying relatively lightweight cargo, and where the cargo section didn't extend aft of the overwing exits. NW's 31 other 707s were standard -320Cs. The first 5 are usually referred to as 707-351B(SCD). The full -320C was the largest-selling 707 model, accounting for just over 1/3 of production.
Two of those NW hybrid -320Bs with cargo door below: