Introduction: Folding Wing Technology
The Boeing 777X is notable for its innovative folding wingtips, which retract on the ground to comply with airport size standards. During takeoff, the wings extend to maximize performance and efficiency. Though the 777X is the first commercial aircraft to incorporate this feature, the concept itself is not new to Boeing.
Boeing’s Past Considerations of Folding Wingtips
Boeing had initially contemplated folding wingtips for its original 777 series, but no orders were placed. The company again considered them for the Boeing 747-8 but decided against the option. The 747-8’s wingspan stands at 224 feet 5 inches, shorter than the 777X’s extended span of 235 feet 5 inches.
Folding Wingtips on the Boeing 747-8?
The Boeing 747-8, the longest passenger aircraft, entered service with Lufthansa in June 2012. Measuring 250 feet 2 inches, it surpassed the Airbus A340-600 in length. The considerable length presented design challenges, especially regarding wingspan, which required special attention to balance the aircraft’s length and weight.
| Feature | Boeing 747-400 | Boeing 747-8 |
|---|---|---|
| Wingspan | 211 feet 5 inches (64.44 meters) | 224 feet 5 inches (68.4 meters) |
| Wing Area | 5,823 ft² (541.2 m²) | 5,969 ft² (554.5 m²) |
| Wingtip | Vertical winglets | Raked wingtips |
| Maximum Takeoff Weight | 875,000 lbs (396,900 kg) | 987,000 lbs (447,700 kg) |
| Aspect Ratio | 7.91 | 8.5 |
| Range | 7,260 NM (13,450 km) | 7,730 NM (14,320 km) |
Instead of folding wingtips, Boeing opted for raked wingtips on the 747-8, providing efficiency without the complexity of a folding mechanism. The raked design results in approximately 8% lower fuel consumption compared to the 747-400.
Wingspan Regulations and Certification Challenges
Folding wingtips help aircraft adhere to ICAO Code requirements, which govern maximum wingspan specifications. Code F aircraft like the 747-8 and Airbus A380 are allowed wingspans up to 80 meters, while Code E limits are set at 65 meters.
The 777 is a Code E aircraft, prompting Boeing to ensure the 777X complied with these requirements. On the other hand, the 747-8’s design as a Code F aircraft meant compliance wasn’t an issue, thus avoiding the complexities and potential delays of incorporating folding wingtips.
747-8 Efficiency Improvements
With General Electric GEnx-2B67 engines, the 747-8 achieves 16% lower fuel burn per seat over the 747-400 and complies with ICAO Stage 4 noise standards. The fuel efficiency remains high at 0.142 miles per gallon versus the 747-400’s 0.139 mpg, made feasible by accommodating 50 more passengers.
The Longest Commercial Aircraft Record
Boeing’s longest aircraft history spans the last decades, with the 747 and 777-300 models. The Airbus A340-600 overtook them until the 747-8’s debut. The 777X will soon surpass it with a length of 251 feet 9 inches.
| Rank | Aircraft | Length |
|---|---|---|
| 1 | Boeing 777-9 (777X) | 251 feet 9 inches (76.72 meters) |
| 2 | Boeing 747-8 | 250 feet 2 inches (76.25 meters) |
| 3 | Airbus A340-600 | 247 feet 3 inches (75.36 meters) |
| 4 | Boeing 777-300 / 777-300ER | 242 feet 4 inches (73.86 meters) |
| 5 | Airbus A350-1000 | 242 feet 1 inch (73.79 meters) |
The potential Airbus A350-2000 stretch could challenge the 777X’s record, yet it would require almost a 10-foot elongation to secure the title.
Future Outlook for the Boeing 747-8
The 747-8 marks the end of Boeing’s iconic 747 series, with production stopped in early 2023. Around 150 747-8 airframes, mainly as freighters, remain operational. The chance for a century-long lifespan of the 747 might still be possible depending on freighter longevity.
| Airline | 747-400 | 747-8i | Total |
|---|---|---|---|
| Lufthansa | 8 | 19 | 27 |
| Air China | 2 | 7 | 9 |
| Korean Air | 5 | 5 | |
| Rossiya Airlines | 5 | 5 |
Only four airlines currently schedule 747 passenger flights, with Lufthansa planning a mid-2030s retirement for its 747-8 fleet and Korean Air by early 2030s.
The Future of Folding Wingtips
The 777X will pioneer folding wingtips on a commercial jet in 2027. Airbus’s next-generation single-aisle jet, featuring “long foldable wings,” is expected to follow. With biomimicry offering up to 30% more efficiency, folding wingtip design could be revolutionized. However, other commercial aircraft projects remain unlikely to adopt this technology for the foreseeable future.
