"Boeing 737. The Next Generation." (Part One)
Somewhere across the globe a Boeing 737 takes off or lands every 5 seconds and over 1200 of their compatriots are aloft at any given time. With the 7000th aircraft rolled out in December 2011, the 737 has truly brought the term ‘prolific’ to airliner production and considering the maiden flight of the 737-100 took place in 1967, it is quite appropriate that the latest metamorphism be dubbed the “Next Generation”.
With its title clipped to the more easily handled, “NG”, the ‘next generation’ covers the -600 through to the -900 series of the 737. Of Boeing’s latest offering the 700 and larger 800s have gone on to dominate the skies, while the ‘Max’ is still yet to come. The NGs predecessors, the -200, -300 and -400 had provided the backbone of short haul travel in a very similar way. Whilst the number of earlier models is ever dwindling, they have gone on to be referred to as ‘The Classics’ as they reflect a last bridge between the analogue and digital flight deck. Whilst a highly visible transition, the clocks and dials are but one area of many in which the Classic has been superseded.
737 Next Generation Development:
The 737NG program was launched in 1993 under the title of 737-X. Boeing recognized the time-tested qualities of the type, but needed to bring the efficiency of new technology and systems to its most enduring machine. Fundamentally, the 737-X was to fly higher, farther, faster and more fuel efficiently than its predecessor without evolving into a new machine requiring a new designator and certification. A challenging task to say the least.
Much of the efficiency revolved around the redesigned wing. With 25% more total surface area and potentially 30% more fuel capacity, the new wing has much to offer. Boasting a higher span than the Classic, the new wing is a more swept with a constant angle of sweep and double-slotted continuous span flaps. Gone is the double swept leading edge and characteristic ‘kink’ of the earlier wing. Similarly, there have been changes to the leading and trailing edge flaps that have resulted in weight saving as well as aerodynamic efficiency. For all of the improvements to the aerofoil and lift augmentation devices, the most visible change to the wing and the aircraft generally, is the emergence of blended winglets on the 737.
The smooth, upward sweeping fairings at the tips stand a prodigious 2.4 metres and increase the span by a metre and a half. Simply put, the winglets benefit the aircraft through the reduction of induced drag and consequently improved operational and economic performance. Whilst yielding an impressive 4% saving in mission block fuel, the winglets also increase the 800s range by over 100nm. (Source: Boeing) Improved performance out of ‘hot, high and humid’ airfields is another advantage of the blended winglet. In fact, this aerodynamic device has proved so successful that it is now being retrofitted to 757s as well as 737s.
The Flight Deck of the Boeing 737-800.
The NG also sees the introduction of GPS to the 737 navigation system. Previously only equipped with dual Inertial Reference Systems (IRSs), the system relied upon ‘updates’ from ground based VORs and DMEs to continually refine the aircraft’s present position. Without such updates, the pictorial presentation on the map display could be inaccurate requiring the crew to heavily rely on ‘raw data’ from conventional radio navigation aids. GPS provides a far more consistently accurate map display for the crew and allows for more integration of the aircraft’s Lateral Navigation (LNAV) and Vertical Navigation (VNAV) systems. Additionally, the NG is equipped with a Predictive Windshear Warning and Enhanced Ground Proximity Warning System (EGPWS). This ‘forward-looking’ form of the original GPWS provides improved terrain clearance by such mechanisms as Terrain Clearance Floor, Look Ahead and Runway Clearance Floor algorythms.
Efficiency and costs savings can also be achieved on the ground. Production line improvements saw the final assembly of a 737NG in a record-breaking 11 days in 2005. On the maintenance side, the NG was developed with an eye to reducing airframe maintenance costs by 15%. Comprised of significantly less parts than the Classic, the NG was also designed with far more ‘ease of access’ for maintenance crews. Redesigned leading edges, landing gear, electronics, APU and the 15% more efficient CFM56-7 engines all contributed to the bottom line. In conjunction with improved maintenance documents, corrosion prevention and extended scheduled maintenance intervals, the 737NG has won the battle of the dollar over its forerunner.
On the flight deck, the 737NG strongly resembles its twin-engined big brother, the Boeing 777. The panel is dominated by the presence of 6 LCD panels arranged side by side, replacing the combination of EFIS and analogue that was found on the Classic. For the pilots, this means a degree of modification of their instrument scan from the vertical to the horizontal. The flight deck was designed in response to the demand by operators that a new type endorsement not be needed. As a consequence, the overhead panel closely resembles the Classic with its array of toggle switches and dials, though the operation of the system behind the switch may well be different.
A QANTAS Boeing 737-800 awaits its take-off clearance as another 737NG comes 'over the fence'.
As for achieving higher, faster, farther and more fuel efficient performance; Boeing delivered. The NG possesses greater range by more than 400nm over the earlier model, whilst topping out at FL410 (41,000 feet) as opposed to the Classic ceiling of FL370 (37,000 feet). With a typical cruise speed of 0.78M and a sprint capability to 0.82M, the NG draws away from the Classic’s average cruise of 0.745M, whilst all the while burning less fuel. Furthermore, depending on the cabin configuration, the -800 can achieve all of this while carrying around 40 more passengers than its predecessor. From humble beginnings as the 737-100 nearly 40 years ago, the 737 has kept pace with the times through ongoing development and improvement. The 737NG is no exception.
Technologically, some 737 NGs can be equipped with a ‘Head-Up Guidance System’ or ‘HGS’. The HGS 4000 system features a transparent drop-down screen in front of the Captain on which is projected an array of flight information, allowing the pilot to operate in lower visibility situations than would otherwise be possible. Head-Up Display (HUD) technology has been available for years on military aircraft and Alaska Airlines started flying HUD on their 727s back in the mid-80s and all of their 737-400s are equipped with the technology.
Some airlines have opted for the Vertical Situation Display (VSD) on their aircraft. The VSD displays the current and predicted flight path of the aircraft and indicates potential conflicts with terrain. The VSD is designed to enhance situational awareness on the flight deck and is yet another way in which the Next Generation is offering advances over its predecessor......
Check back later this week for the conclusion to "Boeing 737. The Next Generation."
