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The 717 is actually not an original Boeing or McDonnell Douglas design; it's a refinement of a very old DC-9 airframe from the 60s massively upgraded with moder

by kunai 11y ago

The 717 is actually not an original Boeing or McDonnell Douglas design; it's a refinement of a very old DC-9 airframe from the 60s massively upgraded with modern avionics and modern systems. The DC-9s (and later, the MD-80/90s) were very well-engineered aircraft, and the fact that their core airframe designs are still in operation some five decades later is a testament to how sound Douglas' original engineering and design methodology was.

redthrowaway 11y ago
You'd have to think though that a frame built long before CAD and long before you could stress test member components digitally would be much heavier for the same strength (or weaker for the same weight) than a modern airframe which could be min-maxed to high hell before a single sheet of aluminum was stamped.
- jimmcslim 11y ago
  Is there an opportunity to revisit this design with Dreamliner-style composite materials perhaps?
  - notahacker 11y ago
    Not a commercial one; it's a size of aircraft which already has an anomalously large number of competing new generation rivals.
    - chx 11y ago
      Not only would it need to contend with the massively successful Boeing 737 series and the Airbus A320 family but also the upcoming Bombardier CSeries which is an unusually efficient plane .
- meatysnapper 11y ago
  The Mig-25 was mostly build from steel. Steel! Good engineering can be done without the aid of a computer.
  - jandrese 11y ago
    It was also built with the philosophy that it doesn't really matter what you build the aircraft from as long as the engine is big enough. Of course this hurt its fuel efficiency, but in some ways this was a good thing. The mission it was designed for (intercepting supersonic bombers) doesn't require the plane to loiter and the short range meant it would be difficult to defect with.
    - mikeash 11y ago
      Difficult but not impossible: https://en.wikipedia.org/wiki/Viktor_Belenko https://en.wikipedia.org/wiki/Viktor_Belenko (Not meant to contradict you, just an interesting story.)
    - speeder 11y ago
      Is a steel plane harder to shoot down than an aluminum plane? Or it makes no difference because the fuselage has to be thin?
      - sandworm101 11y ago
        Absolutely no difference. Only a handful of near-modern planes (a-10) have any real armor protecting the plane itself. Pilots often sit in metal tubs, but the overall plane is unprotected from anything physical beyond bird strikes. Any protection is incidental to the structural requirements. There might be something to say for a metal with a higher melting/yield temp that could survive longer in a fire but I don't think that enters into the design equation.
      - meatysnapper 11y ago
        They would have built it from titanium but at titanium welding hadn't been figured out too well then. The Alfa sub hulls were done with plutonium rods if I remember right!
        jessaustin 11y ago
        Plutonium? Apparently weight is not an issue.
- WalterBright 11y ago
  The DC-3 was famously overbuilt because Douglas had no experience with large aircraft and played it safe. The result was the DC-3 was a very robust aircraft, and this contributed to its many decades of service (and still doing so today).
- deleted 11y ago
  [deleted]
sjm-lbm 11y ago
I'm not an airplane engineer, but I think a fair amount of it is technical debt, not the quality of the DC-9 design. For example, the 737 - a competing design that came out around the same time - is not only still being made, it's is getting prepped for another minor revision (the 737 Max), and the newest narrowbody airliner design in common worldwide usage (the A320 series) is going on 30 years old. The 717 was launched as the MD-95, a project at McDonnell Douglas to update the DC-9 series for the 90s, and Boeing (after merging with McDonnell Douglas) mostly just built out the already-sold MD order book and then shut the line down. It would likely be very good for a manufacturer to make a new, clean-sheet design with updates like a carbon fiber fuselage, but the time needed to bring such a product to market would cause major problems for any company attempting such a project.
- cstross 11y ago
  Several such craft exist at the bigger end of the regional jet market. There's the Sukhoi Superjet 100, for example: https://en.wikipedia.org/wiki/Sukhoi_Superjet_100 https://en.wikipedia.org/wiki/Sukhoi_Superjet_100 or the Embraer 190/195. These are both post-2000 airliners that have sold or been ordered in the hundreds (in the case of the Embraer E-jet family, total orders exceed a thousand), which carry around 100-110 passengers in 2+2 or 2+3 seating, and which are designed for much the same market niche. The reason the 717 is popular is because the airframes are fully depreciated; the cost more to run than the newer jets, but are much cheaper to buy or lease. (Source: a guy I know who used to work in Finance for Allegiant, back before they began to diversity from MD-80 family planes.)
  - peckrob 11y ago
    > Several such craft exist at the bigger end of the regional jet market. In fact, there is about to be a veritable boom in that particular market. In addition to the Sukhoi Superjet 100, you have: * The Bombardier CSeries (https://en.wikipedia.org/wiki/Bombardier_CSeries https://en.wikipedia.org/wiki/Bombardier_CSeries) * The Comac ARJ21 (https://en.wikipedia.org/wiki/Comac_ARJ21 https://en.wikipedia.org/wiki/Comac_ARJ21) * The Irkut MC-21 (https://en.wikipedia.org/wiki/Irkut_MC-21 https://en.wikipedia.org/wiki/Irkut_MC-21) * The Mitsubishi MRJ (https://en.wikipedia.org/wiki/Mitsubishi_Regional_Jet https://en.wikipedia.org/wiki/Mitsubishi_Regional_Jet) This is in addition to established offerings from Embraer and Bombardier (and some Airbus and Boeing at the very high end of the regional jet market with the A-318 and the smaller 737s). Each of these is more or less a clean-sheet design. The CSeries is already in flight testing. Dornier was also trying to enter this market with a new design in the late 90s/early 2000s with the 728 series (https://en.wikipedia.org/wiki/Fairchild_Dornier_728_family https://en.wikipedia.org/wiki/Fairchild_Dornier_728_family), but they ran out of money.
hga 11y ago
Indeed, not mentioning it's the last version of the venerable DC-9 is a major omission. When I started flying from home for educational reasons in late high school in the late '70s Ozark Airlines was all DC-9s, and they sure seemed to be excellent. In reference to other comments on the DC-3, Wikipedia says "the last [Ozark] DC-3 flight was October 1968" (https://en.wikipedia.org/wiki/Ozark_Air_Lines#Jets https://en.wikipedia.org/wiki/Ozark_Air_Lines#Jets).

by kunai 11y ago

redthrowaway 11y ago

You'd have to think though that a frame built long before CAD and long before you could stress test member components digitally would be much heavier for the same strength (or weaker for the same weight) than a modern airframe which could be min-maxed to high hell before a single sheet of aluminum was stamped.

jimmcslim 11y ago
Is there an opportunity to revisit this design with Dreamliner-style composite materials perhaps?
- notahacker 11y ago
  Not a commercial one; it's a size of aircraft which already has an anomalously large number of competing new generation rivals.
  - chx 11y ago
    Not only would it need to contend with the massively successful Boeing 737 series and the Airbus A320 family but also the upcoming Bombardier CSeries which is an unusually efficient plane .
meatysnapper 11y ago
The Mig-25 was mostly build from steel. Steel! Good engineering can be done without the aid of a computer.
- jandrese 11y ago
  It was also built with the philosophy that it doesn't really matter what you build the aircraft from as long as the engine is big enough. Of course this hurt its fuel efficiency, but in some ways this was a good thing. The mission it was designed for (intercepting supersonic bombers) doesn't require the plane to loiter and the short range meant it would be difficult to defect with.
  - mikeash 11y ago
    Difficult but not impossible: https://en.wikipedia.org/wiki/Viktor_Belenko https://en.wikipedia.org/wiki/Viktor_Belenko (Not meant to contradict you, just an interesting story.)
  - speeder 11y ago
    Is a steel plane harder to shoot down than an aluminum plane? Or it makes no difference because the fuselage has to be thin?
    - sandworm101 11y ago
      Absolutely no difference. Only a handful of near-modern planes (a-10) have any real armor protecting the plane itself. Pilots often sit in metal tubs, but the overall plane is unprotected from anything physical beyond bird strikes. Any protection is incidental to the structural requirements. There might be something to say for a metal with a higher melting/yield temp that could survive longer in a fire but I don't think that enters into the design equation.
    - meatysnapper 11y ago
      They would have built it from titanium but at titanium welding hadn't been figured out too well then. The Alfa sub hulls were done with plutonium rods if I remember right!
      - jessaustin 11y ago
        Plutonium? Apparently weight is not an issue.
WalterBright 11y ago
The DC-3 was famously overbuilt because Douglas had no experience with large aircraft and played it safe. The result was the DC-3 was a very robust aircraft, and this contributed to its many decades of service (and still doing so today).
deleted 11y ago
[deleted]

sjm-lbm 11y ago

I'm not an airplane engineer, but I think a fair amount of it is technical debt, not the quality of the DC-9 design. For example, the 737 - a competing design that came out around the same time - is not only still being made, it's is getting prepped for another minor revision (the 737 Max), and the newest narrowbody airliner design in common worldwide usage (the A320 series) is going on 30 years old. The 717 was launched as the MD-95, a project at McDonnell Douglas to update the DC-9 series for the 90s, and Boeing (after merging with McDonnell Douglas) mostly just built out the already-sold MD order book and then shut the line down. It would likely be very good for a manufacturer to make a new, clean-sheet design with updates like a carbon fiber fuselage, but the time needed to bring such a product to market would cause major problems for any company attempting such a project.

cstross 11y ago
Several such craft exist at the bigger end of the regional jet market. There's the Sukhoi Superjet 100, for example: https://en.wikipedia.org/wiki/Sukhoi_Superjet_100 https://en.wikipedia.org/wiki/Sukhoi_Superjet_100 or the Embraer 190/195. These are both post-2000 airliners that have sold or been ordered in the hundreds (in the case of the Embraer E-jet family, total orders exceed a thousand), which carry around 100-110 passengers in 2+2 or 2+3 seating, and which are designed for much the same market niche. The reason the 717 is popular is because the airframes are fully depreciated; the cost more to run than the newer jets, but are much cheaper to buy or lease. (Source: a guy I know who used to work in Finance for Allegiant, back before they began to diversity from MD-80 family planes.)
- peckrob 11y ago
  > Several such craft exist at the bigger end of the regional jet market. In fact, there is about to be a veritable boom in that particular market. In addition to the Sukhoi Superjet 100, you have: * The Bombardier CSeries (https://en.wikipedia.org/wiki/Bombardier_CSeries https://en.wikipedia.org/wiki/Bombardier_CSeries) * The Comac ARJ21 (https://en.wikipedia.org/wiki/Comac_ARJ21 https://en.wikipedia.org/wiki/Comac_ARJ21) * The Irkut MC-21 (https://en.wikipedia.org/wiki/Irkut_MC-21 https://en.wikipedia.org/wiki/Irkut_MC-21) * The Mitsubishi MRJ (https://en.wikipedia.org/wiki/Mitsubishi_Regional_Jet https://en.wikipedia.org/wiki/Mitsubishi_Regional_Jet) This is in addition to established offerings from Embraer and Bombardier (and some Airbus and Boeing at the very high end of the regional jet market with the A-318 and the smaller 737s). Each of these is more or less a clean-sheet design. The CSeries is already in flight testing. Dornier was also trying to enter this market with a new design in the late 90s/early 2000s with the 728 series (https://en.wikipedia.org/wiki/Fairchild_Dornier_728_family https://en.wikipedia.org/wiki/Fairchild_Dornier_728_family), but they ran out of money.

hga 11y ago

Indeed, not mentioning it's the last version of the venerable DC-9 is a major omission. When I started flying from home for educational reasons in late high school in the late '70s Ozark Airlines was all DC-9s, and they sure seemed to be excellent. In reference to other comments on the DC-3, Wikipedia says "the last [Ozark] DC-3 flight was October 1968" (https://en.wikipedia.org/wiki/Ozark_Air_Lines#Jets https://en.wikipedia.org/wiki/Ozark_Air_Lines#Jets).