Interview – Joe Sutter

JS: Technological advances currently under study for possible application on the Advanced 747-300 available toward the end of the decade include:

•Advanced Engines: General Electric CF6-80C2 and Pratt and Whitney PW4000 engines of 56,000 to 59,000 lb static takeoff thrust capability with significantly lower fuel consumption. These engines provide the thrust required to support a maximum gross weight of 833,000 lbs. They will be installed on new struts which relocate the engine in relation to the wing. reducing the aerodynamic drag.

•Advanced Flight Deck: Digital avionics can be incorporated from the 757/767 programs including autopilot, autothrottle and flight management systems. Electronic instruments using “TV” pictures replace current primary flight instruments for attitude and direction, The Current Inertial Navigation Systems (INS) can be replaced by less complex Inertial Reference Systems using laser gyroscopes. A majority of 757/767 avionics can be used without change.

•Increased Gross Weight: 850,000 Ib takeoff weight will provide additional range capability and can be incorporated without major changes to air the craft structure.

•Improved Materials: Substitution of aluminium-lithium alloys for current alloys has a weight-saving potential of 9,000 to 11,000 lb. This weight saving is distributed throughout the aeroplane – wings, fuselage, empennage and powerplant installation. In general, the new alloys can be substituted without redesign, since they have similar Structural properties, but have a den. city 7 to 9% lower. In addition, carbon brakes and radial tyres offer an addition weight saving potential of 2. 301 lb.

•New Interior: New architecture with contemporary styling is planned. In- Creased stowage capacity with larger overhead stowage bins will improve passenger convenience, and New, improved materials will improve maintenance costs and reduce weight. A major objective of the new interior development is to improve interior arrangement flexibility, making it easier for airlines to revise seating arrangements quickly to meet changing market conditions. Aerodynamic Improvements: Modifications in the wing geometry including both wing tip extensions and local revisions to airfoil shapes are being studied for possible performance improvement. Wind tunnel testing is planned to verify preliminary analyses.

Preliminary design analyses will continue throughout the remainder of this year. Each potential improvement item noted above will be analyzed to fully understand the cost of changes and the subsequent improvement for the operator.

JT: Will Boeing be building jetliners with entirely fly-by-wire control systems or using relaxed stability to reduce drag and increase fuel uplift through the utilization of additional tanks in the tail unit?

JS: Fly-by-wire technology has been developing at a rapid pace since the early 1970s, particularly for military aircraft applications where mission effectiveness is considerably enhanced. For commercial aircraft, the incentive for fly-by-wire design lies in the potential for lighter-weight, low-volume systems with improved reliability and maintainability. thus lowering overall operating costs. The 767/757 employ fly-by-wire lateral controls (spoilers) and the first full fly-by-wire engine controls are now in the certification process on the 757. As fav. Durable experience is gained in the performance and reliability of digital microprocessor systems and provided the cost of ownership (initial cost and maintenance costs) Continue on a downward trend, we can expect to apply fly-by-wire technology in additional areas including selected elements of the primary flight control system for aeroplanes entering service in the 1990s.

Fly-by-wire technology also enhances the ability to design “smart” control systems which enable the incorporation of stability augmentation and flight envelope protection to further improve efficiency and aeroplane flying qualities.

The use of aft body/tail fuel tanks to increase fuel uplift is generally less efficient than wing fuel tankage. Modern wing airfoil thickness and planform design normally result in adequate fuel volume for growth range requirements over the aeroplane’s product life. For conventional aeroplane configurations, aft body tankage is an option of last resort employed when the wing is of and equate size for the growth mission.

JT: When will the 747 get an entirely new wing and how far can you continue stretching the top deck passenger hump?

JS: An entirely new wing is not in 747 planning in this decade. Current airline requirements can be met with the present wing or with modifications to the current wing. A new wing will be costly and will not be considered until airline planning shows a need for significant growth in the size (capacity) and weight for the 747.

The latest 747-300 (stretched upper deck) model has been very popular so far. Future airline growth requirements will determine the size of the next stretch. When that growth requirement does solidify, the approach may be either a further stretch to the upper deck (up to the full length of the main deck), or a stretch of the basic fuselage, including both main and upper decks.

JT: The 747 may be the flagship but the hot seller these past three years has been the Boeing Baby, the 737. Will Boe- ing be proceeding with a 737-400, with modified wing, additional fuselage stretch and a 757/767 compatible flight deck?

JS: We have studied a number of configurations that increase the passenger capacity of the 737-300. These run from a simple stretch to those having larger stretches with new or modified wings, new or derivative engines and cockpits similar to that of the 757/767. We are continuing those studies along with those of the 7-7 and 757 derivatives. As the airline requirements become clearer, we will be able to better assess what our course of action should be.

JT: And what about the 737 Lite?

JS: The 737-200 Lite is a modified 737-200 with engines designed to meet FAR 36 Stage III noise levels at reduced gross weights. The engines incorporate changes that reduce both fan noise and jet noise. Studies are being conducted on configurations meeting Stage III levels at gross weights approximating the 737-200. Range requirements will likely dictate the final configuration.

JT: 737 looks like it may eventually become Boeing’s biggest-ever seller, how many of the marques do you see eventually being sold and how many more years will the type be in production?

JS: Two versions of the 737 are currently in production, the basic 737-200 and the newly developed 737-300 which has been stretched 21 seats and repowered with CFM56-3 engines. We expect the series, including future improvements and derivatives, to remain in production throughout our current forecast horizon which extends to the year 2000. Total 737 deliveries are conservatively projected to exceed 1600 units by that date. . . and the final total could be significantly higher.

JT: I believe you are also looking at further variants of the 757, a freighter and extended-range versions with overwater capability.

JS: The 757-200 continues to be evaluated for further product improvements and new models. Airplane certification has recently been received for both the Rolls Royce RB211-535E4 and PW2037 engines providing added thrust and improved fuel efficiency. Both Freighter and Combi cargo versions are under study with prospective customers. The capabilities of the 757-200F freighter are particularly attractive to the rapidly growing package delivery market in terms of a good match between volume limited payload and structural limited payload, range capability and dispatch reliability. The 757 is also being studied for extended-range overwater operation using the same approach as now being certified for the 767. This added capability could be coupled with a small increase in gross weight to allow North Atlantic operation with payloads of about 220 passengers.

JT: To combat Airbus Industries’ ultra-long haul TA11, will Boeing be looking to develop even longer-range versions of the 767 than are presently available?

JS: Boeing is studying several additional 767 derivatives beyond the 767-200ER currently in service (5000 nautical miles capability) and 767-300 Extended Range aeroplane announced at Farnborough in September 1984. Among these are 767-300 Long Range and 767-200 Long Range aircraft capable of flying full passenger payloads plus cargo over 6500 nautical miles. Depending on engine developments and market requirements, the 767-300 long-range model could be either a twin-engine or a four-engine aircraft. Recent studies suggest a four-engine derivative of the 767-300LR could use substantially the same wing as a twin-engine version.

JT: Propfans are certainly the current buzzword, can you tell us a little more about Boeing’s efforts with NASA and Pratt and Whitney in test flying a working propfan aboard a 727 test aircraft in 1986?

JS: For the past several years Boeing has been carefully studying the possibility for advanced commercial aircraft utilizing high-speed propfan or unducted fan propulsion alternatives. All major engine manufacturers have development programs aimed at exploring the potential of these advanced engine concepts. There are of course major technical challenges involved with such highly loaded propfan systems including airplane interior noise and vibration, community noise, structural and mechanical reliability and other installation issues. However, the performance improvement potential is very large (about 25% reduction in fuel consumption compared to a comparable techno-conventional turbofan engine). hence Boeing is embarked on programs with the major engine companies to answer many of these technical concerns.

For example, General Electric with NASA participation are developed a full-scale demonstrator engine of an unducted counter-rotating propulsion system known as the GE Unducted Fan (UDF). The demonstrator engine will first run ground tests in the latter half of 1985 and will be ready for flight tests in 1986. Boeing has designed and built for GE/NASA scale model counter-rotating simulators for wind tunnel testing to measure performance and noise characteristics of the UDF engine. For the full-scale flight test phase of the GE UDF demonstrator engine. Boeing and GE will test the engine by installing it in the right-Hand position on a Boeing-owned 727 flight test bed. This flight demonstration program is currently planned to take place in the mid to late 1986 time period. The Boeing 727 advanced engine flight test vehicle will be available for large-scale demonstration testing of alternative development engine concepts from each of the major engine manufacturers in the future.

JT: Will the 7-7 be a propfan?

JS: Boeing uses the term 7-7 in a generic sense to identify a new Boeing entry in the 150-seat arena. The ultimate configuration will be heavily dependent on introductory timing which, in turn, is driven by the marketplace on one hand and the development of propfan techno- logy on the other. The technology could be available to support aeroplane delivery in the 1992 time period.

Market timing is more difficult to predict in view of the ever-increasing turbulence of the marketplace, particularly in the post-deregulation environment in the U. S. The optimal product mix by type of aircraft within each airline fleet is constantly changing as both new and established carriers position themselves in an effort to seek out specialized “market niches” within which they can prosper. The end result is that few, if any, U. S. carriers today can predict with any degree of accuracy what their optimal fleet mix requirements will be five years from now. And fewer still are willing to commit to large, long-lead launch orders for a new design, such as the 7-7. Should propfan technology and market demand materialize simultaneously, the 7-7 may well be a propfan. . . but for reasons stated, it is perhaps premature to make such a judgement today.

JT: It has been reported in the specialist media that you have shown a distinct preference for aluminum-lithium over composites in gaining a weight reduction in future aircraft programs. Is this so, and why?

JS: The use of aluminum-lithium in lieu of composites is strictly a matter of spec1f1c applications. Studies have shown that for a number of applications the use of aluminum lithium alloys will produce a weight saving comparable to that achievable with composites but at quite a lower cost. This is the case in general for aircraft fuselage structure and in particular the case for achieving weight improvements on current modern airplanes such as the 747. While the use of either of these materials will give a weight saving, the aluminium-lithium alloys involve less development and are more readily available for use in primary structure, and the current airplane manufacturing procedures require little change. Therefore, any airplane program whether derivative or “all-new” if launched in the next few years will ‘use this material in its prime structures.

JT: What are your thoughts on alternative fuels for commercial aircraft?

JS: Fuels derived from petroleum will be used in commercial aircraft well into the next century. When economically feasible, these fuels will be supplemented by fuels derived from oil sands, oil shale, and coal, with no significant change to aeroplane systems or to the worldwide fuel distribution system.

The cost of developing the entirely new aeroplanes and fuel handling systems required for the use of unconventional alternative fuels, such as liquid hydrogen, would be enormous. Hydrogen would be considered feasible for commercial aircraft only if the world had exhausted its fossil fuel resources or if a low-cost, abundantly available source of electric power was developed. Neither of these occurrences is likely in a time frame that would require the development of hydrogen-fuelled commercial aircraft in this century.

JT: Finally, with Concorde now providing technological and commercial success in airline service, particularly with British Airways, do you foresee a replacement SST being developed during the 1990s and what shape would it take?

JS: I do not believe a second generation of Supersonic transport will be developed before the turn of the century. Speed is marketable in long-range operations if it can be offered with acceptable economics. . . and this is the key. To assure economic viability, a great deal of basic research in the areas of aero-propulsion, structural and acoustic disciplines is required before detailed configuration studies can begin. In view of the enormous investment required to fund a dedicated, long-term development program leading to a production vehicle, it is unlikely that any single manufacturer will be willing to accept the financial risks involved. . . and a multi-national joint venture concept will probably be required. This process, in itself, could take several years to structure an acceptable agreement, Until the basic research is complete, speculation on size, performance and configuration details is premature.