Page 36 - Index

34 • TWIN & TURBINE October 2018
Motoring by the Numbers
CFM International, Leap 1B, Twin Spool, 68" diameter intake, high bypass turbofans producing 27,900 lbs. thrust each. Compressor: 1 fan, 3-stage low pressure and 10-stage high pressure compressor, 22:1 ratio. Combustor: second generation, twin-annular, pre-mixing, swirler combustor. Turbine: 2-stage high pressure, 7-stage low pressure. Overall pressure ratio: 50:1. The fan has flex- ible blades manufactured using a resin transfer molding process, which untwist as the fan’s speed increases. The mo- tor also incorporates BRM (Bowed Rotor Motoring). When an engine cools, air rising to the top causes uneven cooling of the core shaft and the shaft will bow. After the engine start switch is moved to GND, the EEC (Electronic Engine Con- trol) performs Bowed Rotor Motoring. BRM will be active from 6 to 90 seconds
and MOTORING will be displayed on the N2 gauge between 18-24 percent. The only inconvenience this presents, other than a lengthy start cycle, is getting “Sister Christian” (Motoring – what’s your price for flight?) by Night Ranger stuck in your head as you stare at the motoring icon. Compared to the NG’s CFM56 en- gines, these features result in 15 percent less thrust specific fuel consumption, 20 percent lower carbon emissions and 50 percent lower nitrogen-oxide emissions. Price tag per engine: about $14.5 million.
Do These Engines Make My Fuselage Look Fat?
It’s not uncommon for airplanes to be quite functional while having very little ramp appeal. The Shorts 360, Piper Apache and 737-100 Guppy come to mind. I’m slightly biased since I own and operate the sexiest airplane ever built by human hands (except for perhaps the
P-51D Mustang, F4U Corsair and T-38 Talon). So for those who have owned, loved or flown any of the previously listed, “un-handsomely-fine” aircraft, I mean no disrespect. Not only was the original 737 fuselage disproportionately short, plump and un-handsome, but the small diameter engines on the original -100 model accentuated the impression of excessive fuselage girth. With a five- foot longer, slender looking body and larger jugs hanging from the wings, the proportions of the MAX are more, well – shapely. While aesthetically pleasing, the fuselage stretch did not come with- out compromise. Its design necessitated some Disney-like Imagineering including moving the engines higher and forward, auto-assisted control of pitch during lift off and in the landing flare to prevent tail strikes, a re-lofted and re-contoured tail cone and a taller nose gear assem- bly for engine cowl clearance. All this to make a shapelier airplane you ask? We can dream, but no. Next to the dollar- sign shaped sugar plums dancing in their heads, the marketing folks dreamed of more fuel-efficient engines propelling a long fuselage full of lots and lots of pay- ing passengers, to places far, far away. I don’t fault them because that’s their job and it’s the paying passengers that make the mortgage payment on a great look- ing Duke. Unfortunately, for the profit- ability thing to work, marketing needs us to carry lots and lots of people all on the same airplane – this means adding more seats.
Size Matters
Responding to the profitability co- nundrum and competition from the Airbus A321neo in September 2014, Boeing launched a high-density version of the 737 MAX: the MAX 200. Named for seating up to 200 passengers in a single-class high-density configuration with “slimline” seats. Variants of the MAX have passenger seating numbers similar to airline ticket prices in that it’s difficult to know which number is the real number due to configuration vari- ables and marketing spin. But published numbers say the MAX-7 version to the MAX-10 version have a seating capacity ranging from 138 to 230 passengers with a maximum takeoff weight ranging from 177,000 pounds to 194,700 pounds. In or- der to squeeze in that much payload, some