Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Jets Of The Eighties (Speed Or Fuel Consumption?)  
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Posted (7 years 3 months 4 weeks 1 day 2 hours ago) and read 4890 times:

I noticed how many airplanes built in the eighties, the 767, the 757, the A-320, and such (technically the MD-80 was a derivitive of the DC-9, so I'm not listing it) were designed to fly at a slower Mach 0.80 or Mach 0.82

Did the aircraft designers choose the speed for efficiency, or did the airlines specifically ask for a slower aircraft hoping to save fuel?

Andrea

12 replies: All unread, jump to last
 
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 1, posted (7 years 3 months 4 weeks 1 day 2 hours ago) and read 4880 times:

Through my research, I found that the 757 and 767, based on the 727-300/727XX/7N7/7X7 projects, were conceived right after the explosion in fuel costs in 1973. I also found this, which will answer your question (at least for the Boeing aircraft):

Quote:
Unlike the 727, which was designed for high performance in the 1960s, the 7N7 was aimed specifically at the economy minded short-haul routes where speed was less vital. Boeing calculated that climb consumed 60 percent of the fuel that the 7N7 would use on a 500-nautical-mile trip. It was therefore expected to spend almost as much time climbing and descending as cruising. As a result, the wing was optimized for a Mach 0.8 cruise, substantially less than the 727's Mach 0.9 top speed (147)

Norris, Guy. Boeing. MBI Publishing Company. Osceola: 1998


User currently offlineKELPkid From United States of America, joined Nov 2005, 6264 posts, RR: 4
Reply 2, posted (7 years 3 months 4 weeks 1 day 1 hour ago) and read 4876 times:

The fallout from the two oil cricises of the 1970's (1973 and 1979-and I remember the gas lines in '79  Wink ) had caught up with us by the eighties, and I think that's the reason that many airliner designs that began in the late 1970's and saw the light of day in the 1980's (e.g. 757/767) emphasized fuel effeciency. I also remember my first 767 flight, and thinking what a quiet plane it was compared to the 727's/DC-9's/737-200's  Smile


Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 3, posted (7 years 3 months 4 weeks 22 hours ago) and read 4830 times:

So if there was a plane that could do Mach 0.85 with the desired fuel efficiency, it would have been accepted by the airlines?

Andrea K


User currently offlineZeke From Hong Kong, joined Dec 2006, 8642 posts, RR: 75
Reply 4, posted (7 years 3 months 4 weeks 10 hours ago) and read 4762 times:

Quoting Blackbird (Reply 3):
So if there was a plane that could do Mach 0.85 with the desired fuel efficiency, it would have been accepted by the airlines?

The Convair 990 entered service in 1961, it cruised at M0.91, sadly it used too much fuel.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineKELPkid From United States of America, joined Nov 2005, 6264 posts, RR: 4
Reply 5, posted (7 years 3 months 4 weeks 10 hours ago) and read 4747 times:

Quoting Zeke (Reply 4):
The Convair 990 entered service in 1961, it cruised at M0.91, sadly it used too much fuel.

Wasn't that more a conesquence of Convair's choice of engines, though? The GE J79 wasn't exactly the most effecient engine around...  Wink



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 6, posted (7 years 3 months 4 weeks 5 hours ago) and read 4688 times:

So, the airlines would have accepted a Mach .85 plane if it was just as efficient as the 757/767/A-320?

Blackbird


User currently offlineStarlionblue From Greenland, joined Feb 2004, 16908 posts, RR: 67
Reply 7, posted (7 years 3 months 4 weeks 3 hours ago) and read 4665 times:

Quoting Blackbird (Reply 6):
So, the airlines would have accepted a Mach .85 plane if it was just as efficient as the 757/767/A-320?

Sure. They would have accepted a Mach .95 plane. Even a Mach 1.2 plane if it had had the same fuel burn, the same noise footprint, the same maintenance cost etc....



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 3 months 4 weeks 3 hours ago) and read 4657 times:

Of course....

They didn't know HOW to build a mach 0.85 airliner that could meet the fuel-burn requirements back then. I don't know if extensive wing/body blending, supercritical foils, and a 30-degree sweep even would have done the trick.

Andrea K


User currently offlineKELPkid From United States of America, joined Nov 2005, 6264 posts, RR: 4
Reply 9, posted (7 years 3 months 4 weeks 3 hours ago) and read 4654 times:

Quoting Blackbird (Reply 8):
Of course....

They didn't know HOW to build a mach 0.85 airliner that could meet the fuel-burn requirements back then. I don't know if extensive wing/body blending, supercritical foils, and a 30-degree sweep even would have done the trick.

Andrea K

Would that even do the trick today? Visions of unsold Sonic Cruisers flying past my head...  spin 



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 10, posted (7 years 3 months 4 weeks 2 hours ago) and read 4637 times:

I'm actually not entirely sure!

People knew about supercritical airfoils back then, but I'm not sure if they really had the technical know-how to make one extremely efficient. And it's not just the aerodynamics, it's the engine too! (although jet engines are affected by aerodynamic laws, I meant that even with a spectacularly advanced aircraft design, if you powered it by a crappy engine, it wouldn't work all that well.)

Andrea K


User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1639 posts, RR: 1
Reply 11, posted (7 years 3 months 3 weeks 6 days 15 hours ago) and read 4594 times:

Airliners used to be all about speed, romance, luxury and a whiff of danger. If you flew somewhere, you were important, on an important mission or stinking rich. Adjusted for inflation, a hop across the pond in a flying boat cost about as much in 1940 as a rocket ride in the Concorde in the modern era.

Somewhere along the way, airliners switched to hauling beef instead of passengers. Shorts, flip-flops and sleeveless T-shirts became the favored dress. Your seat mate turned into your 5-abreast row mate and he might just be stinking, rather than stinking rich.

Speed has become unimportant versus the ability to loft paying tonnage over vast distances. It is worse than sardines-in-a-can; it is more like rats-in-a-trap.

I expect that Greyhound will, someday, become an airline.


User currently offlineBlackbird From , joined Dec 1969, posts, RR:
Reply 12, posted (7 years 3 months 3 weeks 6 days 14 hours ago) and read 4581 times:

Actually, how effective were 1975-85's supercritical airfoil designs? I'm actually curious

Top Of Page
Forum Index

Reply To This Topic Jets Of The Eighties (Speed Or Fuel Consumption?)
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Speed Of Air Out Of The GE-90-115's Back End posted Sun Sep 10 2006 01:47:24 by UAL747
What Is The Cruising Speed Of A A300 B4? posted Fri May 26 2006 20:25:43 by 747400sp
Effect Of Temperature On Fuel Consumption & Height posted Sat Dec 24 2005 16:48:29 by Julesmusician
Does Video Footage Exist Of The CV-880/990 Jets? posted Fri Sep 30 2005 21:10:51 by Happy-flier
Gas/Fuel Tank Size Of The 763ER posted Mon Oct 4 2004 15:20:33 by Imonti
Details And/or Photos Of The MD-90-EFD posted Wed Aug 6 2003 06:40:01 by Mirrodie
Help: Fuel Consumption On A C172 Or A C182 Plz posted Wed Oct 23 2002 06:41:08 by Jgore
Specific Fuel Consumption Of Jet Engines posted Sun Jun 16 2002 23:11:43 by YoungDon
Yak-40 Vs Modern Regional Jets Fuel Consumption posted Wed Mar 13 2002 11:28:26 by Turbolet
Cruising Speed Of The A340 posted Sun Sep 23 2001 06:04:28 by Mr.BA

Sponsor Message:
Printer friendly format