Boeing 737 MAX8 Walkarounds
by Dan Dornseif
Our walk around inspection of the 737 MAX-8 begins at the bottom of the jetway stairs which land us near the nose of the airplane. Like the NG, the MAX has one pitot probe and one Alpha (angle of attack) probe on the left side of the nose. The pitot tube on the captain side supplies information to the captain’s air data computer. Note the strips on the nose cone which are installed to dissipate static electricity. On the top of the nose, just forward of the windshield wipers, are a set of vortex generators. These modify the airflow over the windshields, thus reducing aerodynamic noise in the cockpit during flight.
The nose gear on the MAX series has been extended eight inches longer in order to provide adequate clearance under the larger LEAP 1B engine cowls. This change gives the MAX a noticeably different stance while parked on the ramp. On late NG and all MAX aircraft, the nose gear-mounted taxi light has been replaced with LED lights in the wing roots. The nose gear doors are mechanically attached to the nose gear itself through a series of actuator rods, eliminating complex hydraulic installations. The red REMOVE BEFORE FLIGHT tag is attached to the nose wheel steering lockout pin. This safety device is removed and shown to the pilot after pushback is complete.
The aircraft’s avionics equipment is installed below the cockpit, with similar access hatches both forward and aft of the nose gear bay. These compartments are inside the pressure hull of the aircraft and the access doors are plug-type doors, similar in principle to the cabin and cargo doors on the 737.
This view of the nose landing gear from the rear shows the scissor links in good detail. The vertical white line on the nose gear door indicates the castor angle limit of the nose gear for the tug driver during pushback.
The static ports are installed on either side of the forward fuselage. These provide ambient air pressure to the air data computers, which supply airspeed and altitude information to the pilots and various aircraft systems.
A variable geometry air conditioning pack cooling air intake is located just below the leading edge of each wing, in the wing-to-body fairing. A deflector door (shown in the extended position) is only deployed when the airplane is on the ground. This prevents debris, kicked up by the nose wheels, from damaging the heat exchangers. During times when the air conditioning packs are not operating, conditioned ground air is supplied via the attached yellow hose.
All of the landing lights, turnoff lights, and taxi lights are located behind the glass fairing in the wing root. These lights are LED-based and focused with an array of tiny parabolic mirrors. The updated lighting system is very effective.
On the inboard side of both engines, this large vortex generator is installed to energize the air flowing around the cowl and over the wing at high angles of attack.
One of the obvious features of the MAX’s LEAP 1B cowling is the serrated fan duct exhaust.
Another view of the LEAP engine from behind showing the fan duct which encompasses a much larger volume than the older CFM56-7 engines used on the NG series.
The main landing gear is largely unchanged from the NG series. Like the nose landing gear doors, the main landing gear doors move into position mechanically with gear retraction. Since the tire is retracted flush with the lower surface of the aircraft, an aerodynamic hub cap is installed on the outboard wheel only.
The fan blades of the LEAP 1B engine are a major departure from the earlier engines and contribute greatly to the lower noise levels and greater fuel efficiency of the MAX. These composite blades themselves are designed to untwist slightly under load as the engine accelerates and centrifugal forces increase, making the blade angle closer to optimum for all thrust settings.
The wing of the MAX is externally identical to the NG airplanes, with a few exceptions. Each MAX wing has six small vortilons mounted to the lower leading edge of the wing, instead of only three installed on the NG.
The Advanced Technology Winglet, while similar in appearance to the Scimitar winglet on the NG series, is entirely different. These winglets are designed to have complete laminar flow to reduce aerodynamic drag by an additional 1-2%. Each wingtip has six static wicks to dissipate static electricity. Interestingly, the portion of the wing trailing edge outboard of the ailerons is not sharp, but blunt (about ½ inch thick), which is an aerodynamic change from the rest of the 737 fleet.
A busy place! This is a view of the main landing gear well, with aircraft forward to the left. Notice the opening is perfectly shaped for the main tire to make a snug seal when retracted. The hydraulic reservoirs are painted zinc chromate green. The reservoir on the left is for the B system, and the one close to the camera on the right is for the Standby system. The red and black striped driveshaft spins to deploy and retract the trailing edge flaps.
This image is photographed facing starboard and slightly forward, showing the complex piping and wiring installed in the main landing gear well. The reservoir shown to the far left, against the forward bulkhead, supplies the A hydraulic system.
This photo shows the aft wall of the main landing gear well. Just above the Standby reservoir, the trailing edge flap drive system is seen is good detail. This transmission can be driven by the B hydraulic system (normal) or via an electric motor during non-normal conditions.
Another drag reduction was reaped by re-contouring the aft fuselage (Section 48). Note the APU exhaust which is much more pointed than on the NG. The MAX-8 has a tail skid to protect the aft fuselage during takeoff. The white navigation lights have been moved from the aft wingtip to the tail cone.
A close-up of the tail skid shows a red and green compression indicator. Should a tail strike occur, this indicates the compression of the shock absorbing, crushable cartridge. If the green portion is not showing, a repair must be made prior to flight. A fluid drain mast is installed directly behind the tail skid.
The MAX has a flush APU inlet door, unlike the NACA type duct on the rest of the 737 fleet. When the APU is not operating, it is closed. When the APU is operating, on the ground it opens at a 45-degree angle, and in flight the door sequences part way open to 17 degrees.
The starboard side aft fuselage is shown here with the aft cargo door in the closed position. The door itself, which opens inward, is larger than the opening in the fuselage, preventing the cargo door issues suffered by other airliner types in the past. While assisted by latching mechanisms, the cabin pressurization actually holds the door closed. The Panasonic Wi-Fi antenna dome is mounted to the top of the fuselage. On the lower right corner of the photo, the white #2 VHF communications antenna is visible. Note that the cabin windows are the same shape and size as previous 737 models. From the inside, the window frame appears oval for a modernized appearance. In this view, one can see difference in shape through the transparency.
The starboard main landing gear as viewed from the rear. Just inboard of the tires, the brake calipers are visible. The MAX (and some NG airplanes) use carbon fiber brakes versus the steel-based units on the legacy 737 fleet. The mechanically actuated landing gear door arrangement allows for very simple operation and equally simple free-fall emergency landing gear extension if hydraulic pressure from the A system were to be lost.
The hydraulic brake lines can be seen from the front. This aircraft was being fueled at the time. Note the grounding cable clipped to the gear well opening. This removes any static electricity, bonding the fueling apparatus to the aircraft.
A closer view of the braking system. The tires are rated to a maximum speed of 205 knots to allow for the unlikely event of an emergency flaps-up/slats-up landing.
A view of the underside of the aircraft. The air conditioning packs are installed inside the wing-to-body fairing, with access provided through flush doors on the lower surface for maintenance.
This image shows the open forward cargo door, along with the two static ports located forward of the opening. Inside the compartment, the grey cargo nets keep contents from shifting and blocking the swing of the door. The #3 VHF communications antenna is positioned directly below the compartment opening. During normal operations, the #3 radio is used to transmit and receive textual and aircraft performance data.
Beneath the cockpit on the starboard side of the aircraft is the ground power and communications access. The large cable supplies 115-volt, 400 cycle AC power while the engines and APU are not operating. Communication jacks are provided to allow direct voice communication between the tug driver and the cockpit.
The right side of the nose is home to the pitot tubes for the first officer’s air data computer and the standby airspeed indicator. A second Alpha vane is installed for redundant stall warning and pitch stability augmentation systems. Below the first officer’s side window, a release handle is provided to allow the window to be opened from the outside in an emergency.
Climbing back up the jetway stairs allows a good vantage point for viewing the details on the top of the left wing. Each wing has eight small vortex generators on the upper surface to enhance aircraft handling.
Although the basic wing design is common between the MAX and the older NG airplanes, the engine was moved up and forward approximately eighteen inches to accommodate the larger fan diameter. Internally, metal gages were increased and the engine pylon was redesigned. The average Empty Operating Weight of a MAX-8 (compared to the -800 series) is roughly 5,000 pounds higher partially due to structural changes. The painted black outline on the top of the wing corresponds to the position of the wing fuel tank. Thin frost on this area of the wing, due to cold soaked fuel and high ambient humidity, is permissible without a need for deicing.
Although similar to the well-established 737 NG series, the newer 737 MAX offers fuel efficiency that is approximately fourteen percent improved over the latest NG series airplanes. Since the MAX has roughly the same volumetric fuel capacity, this equates to a longer-range capability. The airplane is also amazingly quiet in flight, which makes it very friendly toward the neighborhoods surrounding major airports. To optimize flight control operation, the flight spoiler/speed brake system has been changed from a hydro-mechanical to a fly-by-wire system. However, like all 737s, the ailerons and elevators are powered by dual hydraulic systems, with a cable driven backup system. The rudder is also triple redundant through the use of the Standby hydraulic system. Unlike most modern jetliners today, all 737s are capable of being controlled and landed in the absence of all hydraulic and electrical power. That being said, multiple redundancies in both systems render this eventuality virtually impossible. With the new MAX series, the 737 will be plying the skies of the world for many years to come, offering airlines low fuel burns, and passengers a comfortably quiet flight.
Member Comments :
comment by: planecrazy posted on 11-17-2018, comment #30000
Dan, thanks for the walkaround. Will be very useful for the many who will build a Southwest MAX, myself included. Still puzzles me why Boeing did not change the location of the #3 VHF antenna. One of the more common "ramp rash" accidents is that antenna being sheared off by a belt loader.
comment by: Jeff Jarvis posted on 11-18-2018, comment #30001
Very nice, and the addition of explanations of what you're looking at in each photo is long overdue, so thanks for thoughtfully including it! These photos make it very clear that this is not just a few small changes to the NG -800 to arrive at the MAX-8, and I will make good use of the details for the new Zvezda MAX-8 kit, especially for the nose gear. Well done!
comment by: aro757 posted on 11-20-2018, comment #30019
Thanks Dan, for this awesome, comprehensive walkaround. Really like the descriptions of each photo.
comment by: Ray posted on 11-27-2018, comment #30108
Very nice and detailed walk around of BOEING-737 MAX8 with informative discription of each part. I can see the reflection of DIA's control tower on the right side of the planes nose
comment by: Redbelliedjet posted on 12-05-2018, comment #30143
Thank you for the kind comments and well spotted Ray!