MD-80's 35% less efficient than A321's?

[typhoonpilot]

aa73 1500 pph per side is a little optimistic. Most loads we carry in the 717 are so heavy that anything above 350 is unusual. Even at that alt at max weight you're at 23-2500 pph. What hurts the 717 though is the DC-9 30 wing. Those BR715s can take us a lot higher, the problem is that wing. If I'm not mistaken the 80 will make the low 40s and with those BR715s that fuel flow could likely be in the 1500-1700 pph range. I have seen the 717 at 370 at 94000 lbs ( as heavy as I'll go up there with that ole 9 wing) consume 18-1900 pph. For us that is not a very good (half) load. That said the 717 is a DC-9 and not a maddog, and the wing is what holds us down. The engines are overpowered and I think will complement the 80 nicely.

The wing would cause the same problem with the MD-80 and any re-engining program. The MD-90, with IAE V2500 engines at 25,000 or 28,000 pounds of thrust, still burned 5000 pounds an hour in cruise. A 1000 pound per hour decrease over the -80 carrying essentially the same load, but that is as good as it got because the wing is the exact same as the -80. This is one of the things the killed the -90. If McDonnell Douglas had re-designed the wing to be more efficient for longer range flying it would have been a more capable airplane with longer range and a greater payload at a lower fuel burn.

The MD-80 was designed to be a 1000 to 1500 mile aircraft, just like the DC-9 was designed to be a 500 to 1000 mile range aircraft. The wings were optimized for that flight profile, not for the longer range flights that seem to occur more and more often with narrow body equipment. When Boeing re-designed the 737 the smartest thing they did was make the wing better suited for higher speed cruise and longer range flight. That is why the NG line is so successful.


TP

 

[aa73]

aa73 1500 pph per side is a little optimistic. Most loads we carry in the 717 are so heavy that anything above 350 is unusual. Even at that alt at max weight you're at 23-2500 pph. What hurts the 717 though is the DC-9 30 wing. Those BR715s can take us a lot higher, the problem is that wing. If I'm not mistaken the 80 will make the low 40s and with those BR715s that fuel flow could likely be in the 1500-1700 pph range. I have seen the 717 at 370 at 94000 lbs ( as heavy as I'll go up there with that ole 9 wing) consume 18-1900 pph. For us that is not a very good (half) load. That said the 717 is a DC-9 and not a maddog, and the wing is what holds us down. The engines are overpowered and I think will complement the 80 nicely.

Actually the 80 only gets up to 370, could probably go higher but was only certified as such because it just does not come down fast enough in the event of a Rapid D.

As far as I know, the 80 has a slightly modified -30 wing... it is a bit longer. However, just like the -30 it is a crappy altitude wing. 9 times out of 10 the engines are good for an altitude but the wing is not.

That said, even 2300-2500pph is still a pretty good improvement over 3000 and adds up the fuel savings over a 20 year span.

Our gouge for altitudes is 115,000(FL370), 125,000(FL350), 135,000(FL330). I also hate doing FL370 at no matter what weight, too thin up there for my taste and that wing.

 

[jimcav]

Interesting, I thought the 80 had a better wing design than the 9.

 

[aa73]

Interesting, I thought the 80 had a better wing design than the 9.

It does, it's a tad longer and tapered at the wing tips - better climb and carries a little more weight. But it still sucks at altitude, so it goes without saying that the original wing just wasn't made for high altitudes, no matter how much they've improved it.

 

[Jeff Helgeson]

MD80 wing is more like the DC10 than the DC9

Interesting, I thought the 80 had a better wing design than the 9.

The shape of the wing of the MD80 more resembles the DC10 than the DC9.

The DC9-50 handles much different than the MD87 due mostly to the wing, even though they are about the same size in length. I am only talking about aerodynamic performance, not engines, thrust or weight.

It would be interesting to take a DC9-50 and an MD87 at similar weights for some pattern work, say a Pepsi challenge.

If somebody wants to bring a -50 out to SFB with a gas card, we might be able to work out a "midnight" test flight!

 

[aa73]

The shape of the wing of the MD80 more resembles the DC10 than the DC9.

The DC9-50 handles much different than the MD87 due mostly to the wing, even though they are about the same size in length. I am only talking about aerodynamic performance, not engines, thrust or weight.

It would be interesting to take a DC9-50 and an MD87 at similar weights for some pattern work, say a Pepsi challenge.

If somebody wants to bring a -50 out to SFB with a gas card, we might be able to work out a "midnight" test flight!

Jeff, I think the -50 is longer than the -87.... the -87 is the same length as a -30.

Count me in on your test flight, though, I'll bring the beer... err, Pepsi.