Beyond Flaps

Boeings 727 has always been one of my all-time favorite airplanes. Ive never flown in one as anything other than self-loading freight, but Im old enough to remember when the 727 (and the DC-9) brought jet comfort and performance to smaller, outlying airports where the eras long-haul mainstays-707s and DC-8s-couldnt operate. These days, of course, economics-fuel burn, plus the need to pay three pilots-and noise regulations have relegated the venerable three-holer to tramp-freighter status or the scrapyard.

Joseph E. (Jeb) Burnside

Monday, August 20, 2018 at 12:00 AM ET

Verified

Key Takeaways:

The Boeing 727 achieved its excellent low-speed performance, enabling operations at smaller airports, through advanced wing designs like multi-slotted Fowler flaps and leading-edge slats or Krueger flaps.
These high-lift devices enhance lift at low speeds by increasing wing area and camber, and by strategically using slots to manage airflow, delay flow separation, and allow for higher angles of attack before a stall.
Beyond flaps and slats, other aerodynamic features such as wing fences control spanwise airflow to maintain roll authority, while vortex generators energize the air over the wing to delay separation and enhance control effectiveness at low speeds.
These various high-lift and flow-control mechanisms are crucial for improving low-speed handling, reducing stall speeds, and achieving shorter takeoff/landing distances across diverse aircraft, from general aviation (often with STOL kits) to large transport jets.

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Boeing’s 727 has always been one of my all-time favorite airplanes. I’ve never flown in one as anything other than self-loading freight, but I’m old enough to remember when the 727 (and the DC-9) brought jet comfort and performance to smaller, outlying airports where the era’s long-haul mainstays—707s and DC-8s—couldn’t operate. These days, of course, economics—fuel burn, plus the need to pay three pilots—and noise regulations have relegated the venerable three-holer to tramp-freighter status or the scrapyard.

I didn’t know it at the time, but one of the things that enabled the 727 to reliably operate to and from smaller, regional airports was its wing. Not having pylon-mounted engines helped simplify things a lot, but the real tricks were in the slotted Fowler flaps and leading-edge slats all 727s came with, and which are now commonplace aboard jet transports of almost any size and configuration, as well as general aviation airplanes. What’s so special about these devices, and what else might help with the low-speed handling of the personal airplanes we fly?