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A very unusual aviation event took place on Wednesday January 5th 2016. A Qantas Boeing 747-400 (VH-OJH) normally powered with four Rolls Royce RB211-524 turbofans was seen flying with a 5th engine under its left wing.
The event was commented by a Qantas spokesperson via the web, indicating that due to another Qantas 747-400 being immobilised in Johannesburg, South Africa in urgent need of a replacement engine, a 5 Tonnes spare engine was simply bolted under wing of another 747-400 flight QF63 departing Sydney to Johannesburg for ferrying.
By reason of its tremendous size and weight, expedited shipment of a Rolls Royce RB211-524 turbofan can only be done in the main deck of a dedicated wide body cargo aircraft (or combi) plane. Except if there is an option to transport it externally fastened to the wing of a commercial 747 passenger plane. It seems Boeing engineers thought just that when they incorporated attachment points for a spare fifth engine on the venerable 747 way back in the 1960’s when designing the aircraft. The setup did not involve the need to power nor actually operate the engine but only have it travel securely bolted as an external under wing ‘passenger’.
The practice seems to have been undertaken on many occasions since the 1970’s first with the “Classic” series 747-100/-200/-300 and later with the 747-400. Sadly it was reported that Air India Boeing 747-200 flight 182 that exploded June 23rd 1985 due to a bomb being detonated on board killing all 329 inside was also carrying a spare engine on its left wing when the incident occurred. Pictures exist of various carriers operating 747s with the spare engine attached (notably a 2011 picture of Qantas own 747-400 VH-OJN sister ship of the VH-OJH involved in the latest ferrying flight).
The need to ferry a 5th engine mostly evolves from two situations: 1) a stranded 747-400 needs a spare engine. The spare is ferried to the stricken airliner strapped underneath the wing of another 747-400 or 2). a 747-400 that underwent emergency engine replacement (often leased or loaned from another carrier) while away from its base needs to ferry the unserviceable engine back to its home base where the faulty engine can be fully repaired.
3-engines ferry flights prohibit passenger flight
Yet 747 with have the option to conduct 3-engine ferry flight (back to their repair base) even when one engine is not functional. This may seem less expedient as it has to be done under very restrictive flight conditions involving specially qualified ferry flight crews operating under degraded safety limits margins in speed, weight and altitude. That option eliminates the possibility of generating revenue with paying passengers and goods transported on board. In all the ability to attach an engine under a regular commercial flight is just the least disruptive for flight operations, the most practical and economical by far as well as logistically expedient.
The Qantas announcement specified that the additional weight and drag incurred by the presence of an extra 5-Tonnes engine underneath the wing had warranted a refueling stop in Perth prior to the flight cruising directly to Johannesburg. The announcement made reference of the fact that the presence of that large, characteristically heavy outsize object under the aircraft’s left wing also necessitated adjustments being made by the flight crew of some of the aircraft flight configuration parameters.
Flight analysis and aircraft configuration (a 5th engine can induce as much as 7% less range for that specific mission)
According to flight data available in flightaware.com QF63 operated on January 6th 2015 undertook the Sydney Perth flight leg in 4 hours and 20 minutes and Perth-Johannesburg portion in 10 hours and 08 minutes. Normal QF63 direct flights Sydney-Johannesburg usually span a bit less than 13 and a half hours. The web site also reports an average speed of 445 knots (Mach 0.67) on the Perth leg and 463 knots (Mach 0.70, 857 kn/hr) when bound to Johannesburg. This compares to 495-499 knots (Mach 0.75, 920 km/hr) cruise speed normally on the route (these average speed incorporate slower take-off, climb, descent and approach phase so may be well below actual cruising speed under good or even adverse wind conditions). With a 5th engine, a 747-400 traveling at the optimized 857 km/hr speed on a 13.5 hour journey can only theoretically cover 11,569 km as opposed to the 12,420 km Sydney – Johannesburg span, representing a 7% range shortfall for that specific mission (actual distance flown directly between Sydney and Johannesburg is 6,857 nm; 11,035 km and additional reserve emergency fuel is required).
Does the spare engine needs to be covered with a aerodynamic nose cone?
-in cruise condition the flow of air going in and around the 5th engine can have serious drag penalty. it seems air rushing into the main fan blade can be a bit of an issue too.
For an idea of the thrust delivered by a 747 engine’s, pilots often rely on N1 value read out in their instrument panel. For Rolls Royce RB211-524G/H that power Qantas 747-400 fleet, a 100% N1 performance value on the pilot engine display indicates that the main fan rotation speed has reached 3,900rpm (rotation per minute). At maximum thrusts N1 values can reach 110.5%, equivalent to 4,310rpm. For the General Electric CF6-80C2-B1F turbofans equipping the 747-400ERs versions that Qantas also operates have N1 value of 100% that translate to 3,280rpm on the fan blade. Those engines have maximum fan blade rotation speed of 3,854 rpm reached when N1 is at 117.5%.
At high altitude cruise, the N1 value selected for thrust setting parameter depends on aircraft weight, altitude etc and only represents a fraction of the fan rotating speed mentioned above (N1 varying roughly anywhere in between 45% and 75%) however we can imagine that the windmill motion impelled by the aircraft speed onto the spare engine fan is meaningless (close to null), preventing high speed air from flowing freely through the fan blade back out through the fan cowling duct and the turbine, hence ultimately producing drag forces that are said to limit the aircraft performance to a speed number value between mach 0.78 and mach 0.81. We see that the 5th engine acting aerodynamically as somewhat of a brake chute under the left wing. Most agree that the proper way to allow a turbofan to travel economically and safely is to either remove the fan or cover it. Boeing wing maintenance manual illustrates this with a drawing of a cone-shaped engine cover fitted to the 5th engine. Even more, turbine blade may need to be secured to avoid windmilling altogether. This would prevent components damage due to frictions when no engine lubricant is supplied.
Here we must also recognize that the 747-100/-200 were designed to be very fast with purpose-built highly swept wing angled at 37.5 degree favoring an excellent cruise speed of mach 0.84. The stretched upper deck modification that first appeared on late model -200SUD (Stretched Upper Deck) in the mid 80s and standard on the later -300 and -400 series were said to provide aerodynamics benefits actually bumping cruise speed performance up a notch to mach 0.85.
Aircraft reconfiguration for flight with more drag on the left wing
The effect of drag induced by the presence of a 5th inoperative engine on the left wing can be modeled by the aircraft motion being slightly slower on the left wing, but faster on the right wing. Thus causing a flight attitude where the aircraft nose tends to turn slightly to the left.
The chrobotics.com web site explains that the difference between course and heading is called crab angle (very close to driving forward in a straight motion but with your head turned slightly to the side). For 747 this is big deal in high cross wind landing and also when operation with ‘one engine out’ requires assymetric thrust compensation.
It seems pilots can have options to compensate for a left turn tendency by trimming the aircraft to turn slightly right. Such trimming of the aircraft can be achieved by applying rudder deflection to the right. The net force resulting from more drag on the left wing and right side turn can cancel out each other and make the aircraft fly straight. This is done via rudder trim controls.
On 747-400 rudder trim ‘Yaw’ controls are located on the center aisle pedestal aft of the engine thrust levers. The crew can select the rudder deflection angle by turning a rotary knob to the desired position as indicated in the above Boeing diagram. This will result in the nose of the aircraft pointing precisely where the pilot intends it to.
The same mechanism also controls the deflection of the low and high speed aileron controlling bank angle trim. This can be applied by pilot input directly by rotating the steering wheel while activating a switch. However bank angle can not be applied past an angle value of 47 degree. Furthermore bank angle trim can not be applied while the auto-pilot is engaged. This where Yaw trim via rudder deflection can be very effective as it can be applied in auto pilot-managed cruising condition.
Aircraft reconfiguration for flight with more weight on the left wing
The addition of a 5th engine under the aircraft left wing does not pose structural issues for the aircraft however the extra 5 tonnes create obvious weight unbalances causing the aircraft to bank more to the left. This condition can easily be remedied by the introduction of a weight counter-balancing mechanism. On 747-400 the sophisticated fuel tank architecture permits to use embarked fuel as a flexible weight ballast system.
Fuel as a 5-Tonnes counter weight
The 747-400 fuel system architecture relies on a system of cross feed valves operated via the pilots overhead fuel management control panel. This links directly to a bus (intricate network of piping, valves and pumps to shift fuel from one tank to another)
the 747-400 fuel system architecture manages and distributes fuel among 8 tanks.
- 1 reserve in the horizontal stabilizer optional 9,992 kg
- 1 reserve in each of the wing tips optional 4,003 kg x 2
- 1 main huge tank in the centre wing tank 51,973 kg
- 1 main in each wing outboard section 13,572 kg x 2
- 1 main in each wing inboard section 37,989 kg x 2
- -400ER can have 2 additional fuel tanks installed in the aircraft belly cargo holds (carrying respectively 183,192 kg and 192,912 kg)
The diagram show that the 5th engine is located right under the aircraft left wing main fuel tank. With its 37,989 kg storing capacity, this fuel tank can be filled with just enough fuel to accommodate the extra weight of the 5th ferry engine. Simplistically put filling 5 tonnes less fuel on the left wing’s main tank than on the right wing’s main tank and the aircraft is balanced. But again we must keep in mind that the fuel management system can be a bit more elaborate as 747-400 have automated cross-feed features that continuously monitor fuel levels and can transfer it across different tanks.
Most material on the 747-400 systems in this article relies on the excellent Haynes Owners Workshop Manual BOEING 747 1970 onwards
by Chris Wood
Emirates has announced that it would begin deploying a new seating configuration on its flagship A380. The new aircraft cabin configuration, capable of seating 615 passengers would be the largest yet among all in-service A380s and is set to enter operation on the Dubai – Copenhagen route this coming December. To date the route had been operated by a 777-300ER. The new aircraft variant dubbed Ultra High Density had been up to 3 years in the making, and follows on the two previous cabin configurations spread among the currently 60 aircraft-strong A380 Emirates fleet.
The third A380 variant to fly with Emirates
Emirates was the second carrier to operate the Airbus A380 type right after Singapore Airline with first service taking place on the Dubai – New York JFK route on August 1st 2008. The present day fleet had combined 2 variants: the Long Range A380 variant with a 3-Class cabin configuration that accommodates 517 passengers and the Ultra Long Range A380 aircraft capable of carrying 489 passengers. Both variants had retained a nearly identical 3-Class cabin albeit for an entire section of 28 Economy Class seats that had been removed from the main deck aft section on the Ultra Long Range aircraft. These variations had made possible for the carrier to flexibly assign aircraft giving priority to seat count vs range.
The most seats in the sky
The newer version targeted by the carrier for medium range service operation had been in the making for a few year while initially targeting a 2-class cabin arrangement that could accommodate 604 passengers. With 615 seats; 58 Business Class seats plus 557 in Coach, the final product has been made possible by both eliminating the 14 First Class cabin suites and also reducing the Business Class seat count from 76 to 58. On the two previous variants, the carrier had elected to have an all-premium seats upper deck together with a bar, leaving the main deck to full Coach.
This upper deck premium arrangement has been partly maintained; the bar has been retained there where it is paired to the flat bed Business Class seat.
Full utilization of available space on the main deck has permitted 427 Economy seats to be available. Additional space freed up on the main deck, from the removal of the First Class Suites and the smaller Business Class now permits to fit some 130 Economy seats right behind the Business Class section.
In comparison to other A380 operators, the new Emirates 615 seating capacity variant will only be challenged by up and coming Russian carrier Transaero once deliveries of its 652-seats A380s begin later this year.
For Emirates which has plans to operate up to 140 A380, the pace does not seem to be slowing. The Emirates Dubai hub has efficiently linked travelers to any point on the planet via a single stop. To that end the carrier has skillfully leveraged Open Skies agreements to build up direct long haul routes to and from Dubai. First using smaller A330 to build up demand, incrementally replacing the A330 with its workhorses Boeing 777-300ER while simultaneously adding frequencies before finally pushing the surging traffic to the Super Jumbo A380.
The recipe seems to work: while the Copenhagen A380 route will be flown once daily, the carrier is set to launch a second daily A380 service flight linking Gatwick. Beginning October 1st 2015, Zurich will be bumped from 777-300ER service to A380 service.
The announcement came April 10th as India’s prime minister Narendra Modi was on official visit to France. The contract whose value is estimated at EUR 5 billions will see all 36 aircraft built at Dassault’s Merignac factory in the south of France. Deliveries of the aircraft to the Indian Air Force would occur between 2017 and 2019. India has become the second nation to acquire the type after Egypt this past February.
The deal at last ends a decade long failed acquisition process that initially sought to equip India’s Air Force with a potent future replacement for its obsolescent and accident-prone fleet of Mig-21 which had numbered more than 850 machines. The EUR 15 billion competing tender first issued in the early 2000s put a requirement for 126 Medium Multi-Role Combat Aircraft MMRCA. Crucial to the bidding process was the transfer of technology clause put forth by the client in which only 18 of the 126 aircraft would be built by the original aircraft manufacturer. The remaining 108 airframes would have to be built in India’s Hindustan Aeronautics Limited in India.
Despite Dassault Rafale winning the competition in January 2012 against such credible competitors as the Eurofighter EF-2000, Boeing F-18E/F Super Hornet, Lockheed Martin F-16E/F, Mikoyan Mig-35 a firm purchase contract failed to materialize. Both sides began haggling around escalating cost since the time the tender was first issued, transfer of sensitive French military technology, and the skepticism of Dassault with regards to quality control issues at India’s Hindustan Aeronautics factories where 108 of the 126 aircraft were to be licensed-built.
Friday’s announcement appears to have been the resultant of India’s Air Force urgent need to fill operational capabilities at a time of escalated growth of Chinese and Pakistani air power capabilities, as well as a need to reassure France’s position as a viable, esteemed long term military commercial partner whose armament industry’s prowess is highly regarded in India.
The demise of the Mig-21 fleet in IAF service, and the diminished availability of the precision-strike capable 1980’s era Mirage 2000 ‘Vajra’ fleet as the 51 aircraft-strong fleet undergoes an upgrade to the more modern Mirage 2000-9 standards (on a EUR 1.5 billion contract with Dassault and Thales) has caught Indian Air Force planners short-handed despite the recent delivery of the 150th locally built Sukhoi-30 MKI.
Facts are India has relied for much of its air operations contingencies (including nuclear weapon deliveries) on the Mirage 2000 fleet, as highlighted during the Kargill war in which the Dassault single-engined aircraft gained seemingly legendary status delivering precision (laser-guided) ammunition in difficult operational conditions. The Rafale, its twin engine bigger and more modern successor brings increased operational range and combat payload, benefiting from an advanced on board integrated offensive/defensive system architecture increasing flexibility, survivability and line availability.
In the current scenario, the heavier Sukhoi 30MKI type is bound to reap the profits of the bungled contract and morph into the MMRCA as it is already built locally to 150+ units and fully deployed with the IAF. The powerful highly maneuverable aircraft has grown sufficiently in maturity, operational capabilities and reliability. It has good endurance, combat range, high A/A and A/G weapons payload and is extremely maneuverable. Its latest iteration deploys and advanced integrated systems architecture using western built sub systems.
Emirates Airlines announced on April 4th 2014 that Dallas / Fort Worth International would become the 28th destination it serves from its Dubai global hub with an A380, replacing a 777-200LR which had operated the direct flight since the route opened in 2012. The new daily flights which are set to begin October 1st, 2014 would also make Dallas / Fort Worth the carrier’s 3rd A380 destination in the US after New York and Los Angeles.
Emirates Airline has grown a sustainable long haul global airline in a relatively short amount of time building a dense network of currently 130 global destinations it can conveniently serve from its global hub in Dubai International (DXB) due to its geographic positioning at 8 hours flying time from most major world destinations (connecting 2/3 of world’s population). At the heart of this deliberate strategy lies a fleet which is exclusively composed of wide body aircraft, whose backbone is now formed by about 130 Boeing 777. The growing scale of the A380 fleet of which it currently operate 47 aircraft (and plans to deploy as many as 96) has been deliberately set in rhythm to increase market share at airports where additional slots may not be readily available. For instance on the New York/JFK – Dubai route, without the giant double decker, the carrier would have otherwise been forced to seek enough slots to carry out three or four flights per day. The same need has rapidly evolved at the carrier’s Dubai home base where the operation of the world’s largest 777 fleet coupled with a high portion of passengers connecting undoubtedly dictated a fleet ratio requirement somewhere near 1 A380 for every 3 Boeing 777.
The traffic numbers need to support this trend. For the year 2013, Dubai airport passenger traffic grew 15.3% to 66.5 million passengers at a relatively contained 7.5% increase in aircraft movement rate. the average number of passenger per aircraft was 198 in 2013 growing 4.5% from 189 the previous year. There were 9,514 Emirates A380 flights in 2013 to about 26 destinations. Finally, that airport is expecting passenger traffic to rise to 78.4 million in 2015 and reach 103.5 million by 2020, from 47 million in 2010. The model is proving sustainable, suggesting articulating steady passenger growth around bigger aircraft instead of additional flights.
Two Emirates A380 configurations: Long Range vs Ultra Long Range versions
Emirates identifies two different configurations for the A380 it operates. The carrier differentiates the Long Range A380 version from the Ultra Long Range A380 as offering respectively 517 and 489 seats both in 3 classes of service. The lower number of seats inside the Ultra Long Range configuration corresponds to the removal of several center rows of seats mainly at the rear end of the aircraft’s main deck. The resulting difference in weight saving can add up to more than 3 tonnes of additional fuel for the Ultra Long Range, in comparison to the Long Range version. Accordingly Emirates normally use the Long Range on regional high density routes to Saudi Arabia, India etc.
The 777-200LR which had previously operated the route since its opening in 2012 was configured with a 3-Class 266 seating capacity while flight duration on the US bound leg had averaged 15 1/2 hours, and 14 hours for the return trip.
At Dallas / Fort Worth, the A380 will operate on the recently-expanded Terminal D which is now also being upgraded with a second level jet bridge, in addition to ramps and taxiways enhancements being undertaken to smooth out the giant aircraft maneuvering. To date the largest passenger aircraft to serve Dallas Fort Worth had been 747-400 mainly from British Airways and Qantas.
By taking delivery of its first ever Boeing 777-300ER, China Southern Airline became Asia’s newest operator of Boeing’s highly successful higher passenger capacity long range -300ER variant offer of its 777 twin engine family.
The official acceptance ceremony held on February 25th 2014 at Boeing’s Everett facility highlight the new era that China’s largest carrier by fleet size was entering as another 9 new 777-300ER are scheduled to join the fleet through the year 2016 including 3 additional aircraft to be delivered this year alone.
A replacement for the 777-200ER
The new aircraft has been configured to accommodate 309 passengers in a four-class layout with 4 seats in First Class, 32 in Business Class, 44 in the ubiquitous Premium Economy Class in addition to the 227 Economy seats layered in 10 seats abreast. In this format the 777-300ER are set to relieve the 4 Boeing 777-200ER first acquired in 1997 and 1998 for which the carrier has already began the bidding process that will lead to the sale of the 4 aircraft.
The new aircraft which will first be deployed on the daily Guangzhou (CAN) and Shanghai (SHA) Hongqiao service this March and subsequently on the Guangzhou (CAN) to New York City (JFK) route this coming summer is well positioned to bring unprecedented value to the airline as a replacement for the 24 First class, 53 Business and 207 Economy (284 seats total) seats-configured 777-200ER particularly on the China – North American routes where these aircraft have already proven highly effective.
Modernizing The Fleet Around The A380
The deployment of the new aircraft also occurs in a context of a fleet modernization effort which was initiated by the entry in service of the 5 Airbus A380 from 2011 to 2013, the arrival of 8 state-of-the-art Boeing 787 Dreamliner throughout 2013 (with one more 787 expected) together with the employment of a fairly young A330 fleet as the backbone of long haul service.
The acquisition of the 777-300ER may be proving critical for the carrier ability to establish its Guangzhou Baiyun International Airport as a credible hub for international long haul travel. This shortcoming proved too realistic in 2012 when the carrier A380 fleet was denied unrestricted access to the higher density international travelers market at Beijing International where it had sought to fill its A380 to profitable load factor. The subsequent re-deployment of the super jumbo on less traveled domestic routes instead, allowed the carrier to bleed 200 million Yuan analysts say. In fact in the absence of an aircraft type capable to seat more than 300 passengers in its fleet, China Southern would have been hard pressed to generate enough international passenger density at its Guangzhou hub to bring its 506-passengers A380 to decent load factors and profitable revenues. With a 309 passengers seating capacity, the Boeing 777-300ER can combine operational flexibility to operating economics in order to build the market brand that the carrier needs to attract more passengers to its hub.
Clearly the induction of the 777-300ER gives the carrier the ability to execute a strategy conducive to the consolidation and expansion of its Guangzhou operation into a fully fledged global hub for international travel by virtue of its twin engine operating economics paired with a 300-plus seating capacity well proven in high density long haul market where enhancing passenger comfort and building brand are a must. With the recent introduction of the state-of-the-art 787 Dreamliner for opening new direct long haul routes such as Vancouver – Guangzhou, the shift of the A380 fleet back to the international markets where a premium can best be extracted has already contributed to establishing Guangzhou at a reputable spot. With focus on the Guangzhou – Los Angeles route and the most competitive Guangzhou – Sydney “Kangaroo” route, the A380 can best benefit from the addition of the 777-300ER.