Ndege From United States of America, joined Mar 2003, 204 posts, RR: 3
Reply 3, posted (11 years 7 months 1 day 10 hours ago) and read 7261 times:
Everything I've ever heard or read says it's because of ground clearance with possible wing flexing. The 777 has a little more clearance than a 737. I've wondered why Boeing didn't extend the gear struts a little more, but I'm sure as I'm not an engineer and definitely not paid to come up with these questions and excuses for them, there's probably a very valid reason for it.
Cdfmxtech From United States of America, joined Jul 2000, 1341 posts, RR: 27
Reply 5, posted (11 years 7 months 1 day 10 hours ago) and read 7241 times:
The 737-300 shares a common airframe with the earlier 737s. The CFMs are obviously bigger than the Pratss, so the design of the engine with the "flat bottom" was necessary. Accessories were located to the side instead of the bottom.
There is no effect on efficiency. The powerplant itself is just as round as any other. Its the Cowling (Nose, Fan and Core - TRs) that is oval. The accessories on ths side gives the engine its overall oval shape.
P.S. - U r aware that the 2 aircraft that u have pictured are not Next Gen 737s??
Ha763 From United States of America, joined Jan 2003, 3661 posts, RR: 5
Reply 6, posted (11 years 7 months 1 day 9 hours ago) and read 7220 times:
Boeing did not extend the 737 struts on the -300/-400/-500 and only slightly on the NG's to keep the airplane low enough to not need any ground equipment for fueling, cargo loading, engine maintenace. This and the larger size of the CFM engines compared to the P&W, meant there had to be a flattened bottom to ensure that there was enough clearance.
Doug_Or From United States of America, joined Mar 2000, 3414 posts, RR: 3
Reply 9, posted (11 years 7 months 1 day 1 hour ago) and read 7088 times:
Reading an AW&ST article a good while ago re: stage IV noise requirements Boeing basicaly said that further extending the gear (in this case to make room for larger, higher bypass engines) would not be worth it. The amount of redesign necesary for the wing and central fues would be extensive. I guess its already packed pretty tight in there.
Klaus From Germany, joined Jul 2001, 21478 posts, RR: 54
Reply 12, posted (11 years 7 months 22 hours ago) and read 7014 times:
Some knowledgeable forum member once mentioned that the asymmetrical inlet form does indeed reduce the efficiency of the engines by a few percent. But as had been said, this loss was deemed acceptable when considering the overall cost/benefit relation.
Brons2 From United States of America, joined Sep 2001, 3015 posts, RR: 4
Reply 13, posted (11 years 7 months 21 hours ago) and read 7017 times:
Mmmmm, I'm afraid that's not the reason
Mmmmmm, afraid that *IS* the reason.
Read up on your 737 history at the Boeing web site...
The Boeing 737-300
The Boeing 737-300 program was launched in March 1981. The market requirements for this derivative airplane became clear during the late 1970s in an environment of airline deregulation and the fierce competition that followed.
As a result of increased competition, there were changes in the way air routes were served at that time. Airplanes flew into airports operated as hubs, then dispersed into a spoke configuration, often to short distance destinations. The 737 proved ideal for airlines operating frequent short-to-medium-range routes.
A fuselage extension of 104 inches (2.6 m) allowed the 737-300 to accommodate seats for up to 20 more passengers than its predecessor, the 737-200 model. In mixed-class service with 36/32-inch pitch (91/81 cm), the -300 seats 128 passengers; in an all-tourist arrangement at 32-inch pitch (81 cm), seating is 140. For inclusive-tour charter service (30-inch pitch, or 76 cm), a maximum of 149 passengers can be carried.
From the outset, one of the main objectives of the 737-300 program was to maintain commonality with the existing fleet. The airplane would use new and larger CFM56-3 engines, an advanced-technology flight deck and a common airframe. These features afforded airlines a lower investment in spares, interchangeable flight crews, and less ground support equipment and maintenance training. New aluminum alloys and composites were used to reduce the airplane's weight and aerodynamic improvements were adapted from the 757 and 767 airplanes.
Unlike its predecessor, the 737-200, which was powered by Pratt & Whitney JT8D engines mounted against the underside of the wing in long, thin nacelles, the power plants for the 737-300 -- as well as all subsequent versions of the 737 -- are mounted forward of the wing on struts. The ground-clearance problem created by the larger engines was solved by relocating engine accessories from the bottom of the engine to the side and flattening the bottom of the inlet lip. In addition, the nose wheel unit was attached five inches lower on the fuselage.
The 737-300 also received a new flight deck that makes use of digital technology like that of the 757 and 767. These electronics systems provide concise flight information, allowing increased fuel efficiency and improving the airplane's ability to land in bad weather.
The 737-300 also borrowed the 757-200's interior appointments, which include large enclosed bins, galleys and lavatories located fore and aft; and a wider cabin that allows airlines to choose a larger aisle or more window-seat headroom.
The first 737-300 rolled out of the Boeing Renton, Wash., plant Jan. 17, 1984, and made its initial flight Feb. 24, 1984. That began a nine-month flight test program, during which a fleet of three 737-300s logged nearly 1,300 hours in the air.
Certification of the 737-300 by the U.S. Federal Aviation Administration was awarded Nov. 14, 1984. First deliveries of the new aircraft occurred Nov. 28, 1984, to USAir and Nov. 30, 1984, to Southwest Airlines. Both carriers put their new aircraft into revenue service during December 1984. The British Civil Aviation Authority granted certification Jan. 29, 1985, the same day that Orion Airways of Great Britain became the first non-U.S. customer to take delivery of a 737-300.
The world's airlines ordered 1,112 737-300s over the 18 year period from 1981 through 1998. The last 737-300 is scheduled for delivery in December 1999, completing the production transition to its successor, the Next-Generation 737-700. The 737-300 holds a very special place in aviation history as the most popular model of the best-selling jetliner family.
Firings, if well done, are good for employee morale.
Cloudy From , joined Dec 1969, posts, RR:
Reply 18, posted (11 years 6 months 3 weeks 9 hours ago) and read 6440 times:
Its mentioned that "flattening the engines not only solved the ground clearance problem but actually slightly improved the performance"
I have seen this also, but in different sources. But this does not neccesarily contradict earlier comments from Klaus and others. My guess would be that it depends on exactly what kind of performance one is talking about.