Why the different wing and tail designs in similar sized jets vs turbo prop?

geoffc
  • Why the different wing and tail designs in similar sized jets vs turbo prop? geoffc

    I was flying on Porter Airlines and they had an info card about how similar the Bombardier (I still say DeHavallind) Dash 8 Q400s are to the Bombardier CSeries they have ordered are.

    There was a cool overlay photo to show relative sizes and shapes:

    Dash 8 vs CSeries

    Looking at that image, it got me wondering about the straight vs angled wing. Straight vs angled tails, etc.

    I get that a jet is faster than a turbo prop.

    Cseries cruise speeds are: Mach 0.78 (828 km/h, 447 kn, 514 mph)

    Dash8 Q400 cruise speeds are: 414 mph (667 km/h) 360 knots

    Those are pretty close and yet that is a pretty radical wing design change.

    Is this just the history an old design (Dash 8) vs a very modern design?

  • Well, for starters, the speeds are actually pretty significantly different. The Cseries is almost 25% faster than the Q400. Swept airfoils are much more efficient at those higher speeds, as are jet engines.

    The Q400 is also a wildly stretched version of the original DeHavilland Canada DHC-8 (Dash 8), which was itself based on the 4-engine DHC-7 (Dash 7) STOL airliner. DHC has a lot of history building short takeoff and landing aircraft with pretty extreme performance, and a lot of that colored the design of the Dash 8. What you see today in the Q400 is the result of about 70 years of backcountry aircraft design, applied to a commuter airliner.

    The Cseries, on the other hand, is a clean-sheet Bombardier design meant to compete with the E-jets and the smallest 737s (and 717).

    Hopefully that answers your questions!

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