The 747 Stretched Upper Deck (SUD)
After being made standard on the 747-300, the SUD was offered as a retrofit, and as an option to earlier variants still in-production. An example for a retrofit were two UTA -200 Combis being converted in 1986, and an example for the option were two brand-new JAL -100 aircraft (designated -100BSR SUD), the first of which was delivered on March 24, 1986 but the JAL exaples built and deli8vered originally with extended hump.
The SUD gave airlines operating older -100 and -200 747 models, the ability to stretch the upper deck and increase the number of passengers flown. When plane spotting, it is typically easy to tell the difference from a 747-100/200 and the 747-300 by check out the stretched upper deck, but the SUD makes it a bit more complicated.
The design of the Stretched Upper Deck option allows a 10 percent increase in capacity with only a 2 percent change in operating empty weight. This means added profit potential, lower seat-mile costs and 5 percent lower fuel consumption per available seat-mile.”
“This new option, available for the -100B/SR/-200B and -200B Combi models adds 280 inches of structure to the upper deck cabin.”
“The change is accomplished using current engine options and brake release gross weights of -100B/-200B models. Five maximum brake release gross weights are available ranging from the basic weight of 775,000 pounds (351 520 kg) to 833,000 pounds (377 780 kg). In addition to the basic JT9D-7AW, the -200B Stretched Upper Deck option is available with the following optional engines: Pratt & Whitney JT9D-JFW, -7J, -7Q and -7R4G2, General Electric CF6-50E/E1/E2 and Rolls-Royce RB211-524B2/C2/D4.”
In the end, just two airlines took up this option for their 747-200s. French carrier Union de Transports Aériens (UTA) did so for two aircraft, although KLM made a more significant investment by converting 10. This modification increased the length of the aircraft's conspicuous hump by around seven meters. The stretch was a complex, multi-step procedure that required work on more than just the upper deck crown itself. Indeed, engineers also had to remove the roof behind the original upper deck, and the cab crown. These steps left sufficient space for the stretched upper deck, which was positioned and secured in place following the necessary structural preparations. KLM also used this as a chance to remove the plane's overwing exits and slides, making space for more seats.
Boeing modified 3 full pax KLM 747-206B aircraft and also seven 747-206BC (combi) aircraft. Plus MSN 21110 and 21111 were aso modified and became later again victim of a major modification and both re-appeared as 747-206B(SUD)SF, the first converted “747 special freighter” aircraft with a stretched upperdeck. Rest were MSN 21848, 22376, 22379, 21550, 21549, 21660, 22380, 21659. Overall, these represented nearly 60% of KLM's total contingent of 747-200s. While the concept of the stretched upper deck didn't exactly take off as a retrofit, it shaped the future of the 747.
UTA converted MSN 22515, 22514.
While the 747-300 sold fairly poorly (81 examples), the stretched upper deck was retained by the 747-400 that followed. This quickly outsold its predecessor (694 examples), thanks to factors like its increased range and two-person glass cockpit. The stretched upper deck's story came to an end when the 747-8 came into being, with an even longer second floor.
