Boeing 737-800 Delivering on Low-Cost Scheduled Maintenance

Shorter and less frequent hangar visits help make the 737-800 popular with airlines.

The Boeing 737-800 was launched in September 1994, earned FAA certification in March 1998 and first flew with Germany’s Hapag-Lloyd that same year. It became the biggest-selling member of the 737NG family and has been continually enhanced, for example with the option of blended winglets. The aircraft’s cabin also has had multiple upgrades.

At the start of this year, 3,831 -800s were flying; 383 more are due for delivery before year-end. Deliveries will continue at a similar pace though 2017, after which they will drop off sharply to barely 18 aircraft delivered in 2019. By the end of that year, more than 4,640 will have entered service.

One characteristic that makes the type popular with airlines is that hangar visits are less frequent and lengthy. In developing all 737NGs, Boeing aimed to reduce airframe maintenance cost by 15%, compared with 737 Classics.

Several innovations helped reduce MRO costs. NGs’ new wings have nearly one-third fewer parts than Classic wings. Its leading edge was also redesigned for easier maintenance. The main landing gear on NGs is simpler, and the time required for brake changes was cut by 30%. Access to many NG line replaceable units (LRUs) was made easier, and quick-disconnect line fittings were used wherever possible.

Recent Airworthiness Directives, Boeing 737-800  
Agency AD No. Issued Affects Effective Date
FAA 2/26/15 2/18/15 Fuselage 3/11/15
FAA 2014-20-06 9/19/14 Instruments 11/5/14
FAA 2014-16-14 8/1/14 Auto Flight 9/23/14
FAA 2014-17-02 8/13/14 Communications 9/9/14
FAA 2014-15-12 7/17/14 Stabilizers 9/9/14
FAA 2014-13-07 6/19/14 Lights 8/19/14
FAA 2014-13-10 6/25/14 Fuel System 8/19/14
FAA 8/11/14 4/14/14 Landing Gear 6/3/14
FAA 5/30/14 3/3/14 Stabilizers 4/25/14
EASA 014-0093R1 9/2/14 Auto Flight 9/23/14

Source: FAA and EASA


In addition, better ground-support equipment was provided, halving the time required for engine removal and installation. NG auxiliary power units were made easier to access and maintain, as were bays for electronics and other equipment. Boeing improved NGs’ built-in test equipment (BITE) user interfaces to reduce troubleshooting time and errors.

Boeing NGs use digital cabin-pressure controls instead of analog systems, reducing the number of mechanical parts. This redesign helped BITE more quickly identify problem LRUs or wiring defects, reducing troubleshooting time. BITE also cut this system’s mean time between unscheduled removals by three-quarters.

Another NG upgrade integrated stall management and yaw-damper computers in a single unit, improving reliability and reducing maintenance costs. On NG flight decks, Boeing enhanced systems, reliability, redundancy and BITE to increase mean time between failures by 62%.

Even though the 737-800s now require less maintenance, there are still a lot of them out there. Moreover, the first -800s have been flying for 18 years, so this next-generation aircraft is starting to become a senior jet, the kind that usually needs a little more care in the hangar. So maintenance of the 737-800—like that of the more popular members of the A320 family—is big business.

The upshot, according to Aviation Week’s MRO Prospector, is that the 737-800 will require about $31 billion in total MRO spending from the start of 2015 through the end of 2019. Of that, $2.1 billion, or less than 7%, will be spent on heavy airframe checks, with the vast majority of outlay for engines, components, line maintenance and modifications. The 737NGs are still, according to Boeing’s plan, stingy with the touch labor in C and D checks.

The pace of MRO spending follows fleet size, with a slight lag. Carriers will spend nearly $4.8 billion maintaining the 737-800 this year, more than $6.1 billion in 2017, and nearly $7.8 billion in 2019. Again, more than 90% of this will be spent outside airframe-check hangars.

In 2015, the aircraft will require 848 C and 412 D checks—for about $313 million—according to estimates by MRO Prospector. C and D checks will account for $418 million by 2017—then climb to $541 million by 2019.

There were 10 airworthiness directives issued by the FAA or the European Aviation Safety Agency (EASA) from March 2014 through early March 2015, probably indicative of the rough annual pace of extra MRO necessitated by safety regulation for the 737-800. In addition, modifications will be needed for those aircraft that do not yet meet requirements for new navigation and traffic-management equipment where they fly.

Split Scimitar Winglets (SSW) are available for the 737-800, weighing 294 lb. per aircraft and yielding fuel savings of 1.6% on sectors of 1,000 nm, rising to 2.2% at 3,000 nm. SSW requires a trailing edge wedge, strengthened stringers and ballast weight. An upgrade from blended winglets costs about $555,000.

Other modifications will likely be made for passenger convenience. 

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