Test pilot Paul Smith put Boeing's 737 Max 8 through its paces for FlightGlobal, and here gives his verdict
I flew on Southwest Airlines flight 1389 into Albuquerque International airport on the first leg towards evaluating Boeing's newest model 737 Max 8 – its follow-on to the 737NG. Southwest is a launch customer for the latest model, so before heading out to Boeing's hangar in Roswell, New Mexico, I talked with the flightcrew about what they wanted and expected in the new aircraft.
FlightGlobal's test pilot Paul Smith (left) with Boeing's Keith Otsuka at the controls of the 737 Max 8
They emphasised a requirement for minimal training, as their airline's efficiency relies on a common airframe rating. But, like most pilots, they wanted to see an upgraded, dark cockpit concept that other Boeing aircraft possess. While they may not get the dark cockpit for which they hoped, those pilots and others certainly will not be disappointed with the 737 Max 8.
The day I flew the Max was a busy one for Boeing. As we walked through our pre-flight checks, the company's test pilot and my longtime friend, Keith Otsuka, announced that his team had just started the take-off roll in the 737 Max 9 version of the aircraft I was about to fly. Indeed, it had been a fast-paced month for Boeing, as the company had just celebrated the 50th year of the 737 line and the anniversary of maiden flight on 9 April 1967. The aircraft turned out to be the best-selling commercial type of all time, with more than 9,400 sold. So I was excited to fly the 737 Max.
The aircraft for our evaluation flight was tail number A003 (registration N8703J), which was instrumented and fitted with water ballast tanks. Associated flight-test displays in the passenger cabin were active and in use during our flight, for safety monitoring. This aircraft was in Roswell completing landing-performance testing on an ungrooved runway. The previous day's testing had resulted in some brake damage, which meant that our flight was in jeopardy of being cancelled. Fortunately, the maintenance crew had worked hard overnight to repair the damage, and we were set to go.
While waiting for my turn in the cockpit, I talked with the test pilot of that flight, John Misuradze, who was standing by as the additional safety pilot for our sortie. He explained that setting up for the landing test points was challenging, but that the head-up display (HUD) made that task much easier. I was looking forward to finding out more myself.
THE 737 MAX
Boeing's new 737 family is comprised of the Max 7, Max 8, Max 9 and the Max 200, all of which have been designed to compete with the company's main single-aisle rival, the Airbus A320. The single-aisle 737 Max seats 162 passengers in the two-class version and 189 in a single-class configuration, and has racked up more than 3,700 orders from 86 customers.
By 2006, Boeing was considering a clean-sheet 737 aircraft design incorporating features of the 787 Dreamliner, an aircraft I evaluated for FlightGlobal five years ago. But dreams of a new airframe hit reality in 2010, when Airbus launched its re-engined A320neo – and won large airline orders. The airlines' call for higher fuel efficiency pushed Boeing to react quickly with a competitive alternative. Directors approved the 737 Max project in August 2011, and the Max 8 flew for the first time in January 2016, achieving US Federal Aviation Administration certification on 9 March 2017. It has been an aggressive timetable, with a first delivery to Southwest due later this month.
While the 737 Max is not a clean-sheet design, the programme's engineers made some significant changes to the airframe and propulsion system to achieve the desired fuel efficiency, while also meeting 737 legacy commonality requirements and a high dispatch reliability rate.
Selecting an engine to take advantage of newer technology that increases efficiency with reduced emissions required conducting a fan-size trade study. Choosing a propulsion system is always a design trade exercise. Increased weight from a larger engine also means structural changes and associated weight gains. Boeing's team spent the good part of a year evaluating two fan diameters, both of which would have resulted in airframe and gear changes to accommodate an engine larger than the CFM International CFM56 powering the 737NG.
The final choice was CFM's Leap-1B engine, promising CFM56-like reliability, 20% lower emissions and a 40% reduced noise footprint. However, going from the CFM56’s 157cm (61.8in) fan diameter to the Leap's 176cm (69.4in) meant having to extend the nose gear and redesign the engine pylon, shifting the engine forward and raising it to provide enough ground clearance. But the Leap engine's innovative design, incorporating new fan-blade construction techniques, resulted in a 230kg (500lb) weight saving.
The Leap-1B engines, combined with Boeing's advanced-technology winglet and redesigned aft fuselage, deliver increased range and reduced fuel burn compared with the legacy 737. Providing 23,000-28,000lb of thrust (102-124kN), the Leap-1B promises to deliver better efficiency and reliability, and lower emissions. Working in conjunction with CFM, Boeing reports it is successfully hitting the Max's thrust-specific fuel-burn targets. The engine provides approximately 70% of the fuel savings, with airframe changes contributing the other 30%.
As mentioned earlier, accommodating the Leap-1B was accomplished by moving the engines forward and up on the wing, and increasing the nose-gear length. Changing the thrust line can present issues when certifying for commonality between design types; Boeing compensated for this by tuning the flight controls so the handling qualities were similar enough for certification. Other modifications to the basic 737 airframe include fly-by-wire spoilers, improved aft fuselage aerodynamics and a new auxiliary power unit (APU) retractable door to accommodate changes in the aft fuselage. Even with the redesigns to accommodate the new engine, Boeing says it still promises 230kg weight savings over a comparably outfitted A320neo.
DISPATCH AND RELIABILITY
Next to operational costs, an airline looks to dispatch reliability and minimum ground-time turnarounds. The time an aircraft spends on the ground being repaired or serviced is time it is not generating revenue. For the 737 Max, Boeing addresses this issue in several ways. First, it has incorporated a new system to track and report on maintenance issues. The onboard network system provides engine and flight data for an airline's fleet maintenance, which can be used to troubleshoot and provide more rapid response. This information is available in flight, but for common type-rating requirements is not readily available to line pilots. Nor is it incorporated into the engine-indication and crew-alerting system, which provides a more sophisticated caution and warning system.
The 737 Max's cabin and cargo door locations remain the same, and the changes to accommodate the larger engine do not affect the use or positioning of support equipment such as jetways and cargo loaders. The tested turnaround time is advertised at 43min for a full load of passengers to deplane and board.
Mixing fleets, even within types, can cause an issue for airlines requiring positioning of extra spare parts. This should be minimised somewhat, however, as the 737 Max has a 70% parts commonality with the 737NG.
To learn how the 737 Max would perform under real operational conditions, Boeing partnered with launch customer Southwest to conduct a week-long service-ready operational validation, an initiative Boeing started with the 787 programme. Southwest pilots flew the 737 Max from Dallas Love Field to Albuquerque, Austin, Chicago, Denver and Phoenix. Every routine function was evaluated to ensure compatible support equipment and procedures. The lessons learned resulted in minor changes to maintenance procedures but, overall, Boeing received positive feedback on how the Max would interface with current aircraft and operations. Customer pilots reported they felt the aircraft was nicer to fly on approach, and that the larger displays improved situational awareness.
My airline experience, except for a brief couple of years in the McDonnell Douglas DC-8, has been entirely in Boeing aircraft as an international airline pilot in the 757/767, with more than enough rides in 737 cockpits as a jump-seater hitching a lift to work. All the design modifications intrigued me, but I was particularly interested in two specific areas: handling performance and pilot situational awareness. The changes in the wing, aft fuselage area and especially the engines were significant – was Boeing successful in tuning out these changes by modifying the flight control system? These updates would affect pitch with power changes, but I was assured that this had been compensated for with a new flight-control design.
The other major change I wanted to evaluate was the new large-screen flight displays and how they have improved situational awareness. Large LCD panels provide critical information in a much better format and visibility than older cathode-ray tube displays and especially round-dial legacy aircraft. Larger-format integrated displays and especially the HUD typically improve lines of sight to critical information and vastly improve situational awareness. To be fair, I have not flown other 737 models so I could not draw a comparison between legacy versions and the Max. I trust the certification process, and one flight would not necessarily reveal any differences anyway. But being qualified to fly both the 757 and 767 sensitises me to the necessity of having very similar systems and handling qualities to successfully and safely operate two vastly different-sized aircraft. For the 737 Max, the differences training will typically require classroom academics lasting only three to five days, depending on the airline, its operations and the aircraft configuration it orders.
I climbed into the left seat as the aircraft sat ready for take-off in the number one position for runway 21. Otsuka set up the flight management system for me, with a planned departure out to the working area. Co-ordinating with air traffic control is easy out west, in an area where there is little traffic, and we were quickly cleared for take-off. Taxiing on to the runway and pushing up the throttles for a rolling take-off was intuitive and the aircraft easy to control in the transition from tiller to rudder.
Our take-off weight was an estimated 65,000kg, and we were quickly airborne. At rotation speed, the HUD rotation cue became active and commanded the proper rotation rate. There is no active flight-control feature to prevent a tail-strike, but the cue was intuitive and well harmonised with my flight-control inputs. In our flight plan, we requested to fly direct to Ciudad del Carmen International airport (CME) in Mexico, then TXO V280 back to CME with a 20min en route delay. We cancelled the routing and requested a block altitude and airspace shortly after take-off. I hand-flew the aircraft on the way to the working area, levelling off at 15,000ft.
I was more interested in the aircraft's handling qualities, as today's modern autoflight systems put the burden of flying more on managing the system and less on the pilot's ability to fly – and I was planning on testing that out in the pattern, where situational awareness and system intuitiveness is much more important. The pitch and power response were well matched, requiring little trim to establish level flight, and reducing the power resulted in a very easy and controllable level-off. Once in the area, I rolled into a 30° left bank to establish a level turn at 250kt (462km/h). The HUD was particularly useful and the flight attitude marker made trimming to establish the level turn easy. I pushed the power up to attain 300kt and during the turn with increasing airspeed, aircraft handling and pitch response were normal and easily managed.
Rolling more than 30° resulted in an audible callout of "Bank angle – roll right", with an intuitive HUD display. Rolling into 45° of bank was just as easy, and maintaining level flight with speed changes was once again relatively easy, even with the constant command to correct my bank back to limits. I found that the display and the audible command caught my attention, and it took a lot of concentration to not follow the command to return to wings level. The HUD display was also very alerting and there was no confusion in my mind on how to correct.
I rolled out from the turn and set up for the stick-shaker profile. Pitch and roll harmony were satisfactory and I found that the required yoke force for turns was heavier than the 757 but certainly suitable. Pulling the power levers back to sustain a deceleration rate of about 1kt/s and maintaining level flight, I slowly entered a pre-stall condition and after about 2s of stick shaker, promptly applied full power and recovered nicely. Again, the added thrust from this condition resulted in an easily controlled acceleration to Vref.
Once under control, I set up for the simulated single-engine-out handling demonstration. Pulling back the right engine lever resulted in typical asymmetric yaw, which was easily controlled by the appropriate rudder input. With almost full thrust on the operating engine, I could easily maintain level flight with approximately two-thirds rudder and slight aileron.
These few manoeuvres proved to me that Boeing had compensated for the aerodynamic and propulsion changes and that the Max met certification standards for up-and-away flight, but I wanted to get back to the pattern and test the aircraft where the mission is critical: sticking the landing and getting to the gate.
Boeing has made significant changes in the flight spoiler system – the Max has a new fly-by-wire spoiler system. An added benefit with the new design is also a reduction in weight. Spoilers improve in-flight roll performance and extend symmetrically as speed brakes on the ground to destroy lift and increase braking efficiency. The 737 flight spoilers rise on the wing with up aileron and remain faired on the wing with down aileron, and are initiated when the control wheel is displaced more than approximately 10°.
Another feature in the fly-by-wire spoiler system is the landing attitude modifier (LAM), which performs two functions. The first occurs when the flaps are in the 30 or 40 position. To maintain an acceptable nose landing gear contact margin, LAM creates a higher angle of attack by symmetrically deploying flight spoilers on approach to reduce lift. The amount of spoiler deflection depends on the approach speed and begins at approximately 10kt above Vref. With flaps at 15 to 30 and the thrust levers near idle, the system symmetrically deploys flight spoilers, to generate additional drag.
Standard airline procedures require a go-around for an unstable approach, and I wondered if this system would help the pilot stay out of that situation. My manoeuvring had placed us close to Roswell, and as Otsuka co-ordinated for the approach, I started the descent by extending the speed brakes all the way out and pulled the throttles to idle. I watched him select the first approach in the flight management system – he was a great first officer and I noticed that the system was very familiar to me and reminiscent of my time in the 757 and 767. Even with full speed brakes and idle power, we were still high on approach and LAM could not save me, but it gave me the perfect excuse to execute a missed approach. Missed approaches are always challenging in a large-crew aircraft because they are rarely practiced and the crew are often very busy in a time-critical situation.
In this case, the aircraft response as power was added and the go-around executed was a non-event. Retracting flaps on schedule and cleaning up the aircraft, we requested the next approach: an autopilot area navigation approach. Again, Otsuka set it up in the box and we accepted vectors to final approach. The HUD provided great approach awareness with all the required cues on the display. I found myself using it primarily and only occasionally referencing the head-down displays. I disconnected the autopilot at decision height and continued with a manual landing. The HUD cues were exceptional and I hit my touchdown aim point. On landing, Otsuka reconfigured the aircraft while I applied power and returned to the visual pattern. The visual approach was also easily flown: luckily, it was a left base and I had great view of the runway environment.
It was during this approach that the HUD and the well-harmonised flight controls really demonstrated how well they are integrated in the 737 Max. The final approach to the full stop was a coupled instrument landing system autoland to runway 21. Once again, Otsuka set up the flight management system and, on final, I coupled the second autopilot to activate the autoland system. I monitored the full autoland approach through the HUD. In a full CAT III approach, having the HUD available really makes monitoring all the required systems' performance very easy. Using the autoland system resulted in a perfect landing – and rightfully so. This satisfied me that the flight management and flight control system were well integrated.
Throughout the flight, I found the displays, HUD and mode control panel to be very intuitive and significantly increased pilot situational awareness and reduced workload. My days in the Joint Strike Fighter programme as the cockpit working group's lead convinced me that larger, well-laid-out displays are the key to flowing information, not useless data, to the pilot in a clear and compelling way.
Clicking off the autopilot released the aircraft back to me and I taxied clear of the runway. Returning to our parking spot was convoluted and required many turns. It may seem trivial, but manoeuvring an airliner in a congested airport environment should not require excessive concentration or technique. I found it very easy to accomplish this task in the 737 Max.
No evaluation of a passenger aircraft would be complete without some mention of the revenue-producing part: the cabin. Boeing decided to make the wildly successful cabin-lighting system found on the 787 standard, and having flown as a passenger in that aircraft, I found it just as appealing in the 737 Max. On the flight out, I had talked with the Southwest flight attendants and they were excited to hear about the new aircraft, because it will provide more room for them to do their job while remaining out of the way of passengers. A minor thing perhaps, but one that helps to provide great customer service on those short flights.
As of this date, flight testing for the 737 Max 8 is essentially complete, and line pilots can expect to be flying it in service soon. As for the 737 Max 9 that flew its first flight on the same day as my evaluation flight in the Max 8? Boeing's test pilots completed a 2h 42min first flight, taking off from Renton Field in Washington and landing at Seattle's Boeing Field. Unfortunately, I was not able to convince Otsuka, my fellow test pilot, to invite me back to fly this newest 737 model, but I may continue pestering him until he does.