tsugambler From United States of America, joined Jul 2010, 302 posts, RR: 0 Posted (2 years 2 months 3 weeks 3 days 7 hours ago) and read 2939 times:
Many people have commented recently on the relative inefficiency of the MD-80 series vs. the 738, especially in the case of AA's huge fleet of MD-80s. My question is... could the MD-80s be re-engined with the Rolls-Royce BR715 from the 717? They both have approximately the same thrust range, and I assume the BR715 is much quieter and more efficient than the JT8D. Plus, they're both mounted the same way at the rear of the aircraft. Would anything besides cost prevent such a re-engining program?
litz From United States of America, joined Dec 2003, 1745 posts, RR: 0 Reply 1, posted (2 years 2 months 3 weeks 3 days 5 hours ago) and read 2894 times:
Isn't a BR715 FADEC?
If so, that would add considerably to your costs....
PITingres From United States of America, joined Dec 2007, 954 posts, RR: 12 Reply 2, posted (2 years 2 months 3 weeks 3 days 4 hours ago) and read 2866 times:
The BR715 is at least 2000 pounds heavier, and that's going to make life difficult.
I suspect that it would be difficult to recoup certification costs even if the BR715 were very nearly a drop-in.
LHCVG From United States of America, joined May 2009, 1367 posts, RR: 1 Reply 3, posted (2 years 2 months 3 weeks 3 days 4 hours ago) and read 2866 times:
Going off of Litz's point, the BR715 is a much newer powerplant that might require significant modifications. However, the V2500 from the MD90 might work on the assumption that an MD90 is relatively close to a late-build MD88 or one of the MD-82/3s built to MD88 specs. I'd obviously defer to tech people on the specifics, but I'd be intrigued to know what the possibilities are.
OTOH, one issue you run into is the oft-mentioned fact that most of the Mad Dogs out there are probably paid for, or at least on discounted leases at this point, so you'd have to justify the expense of re-engining and associated mods vs. the savings from not having to pay for a new 737NG or A320-series a/c. I would think the fact that an analogous plane, the Super 27, has remained a niche private a/c speaks to the commercial viability of re-engining in most cases.
tsugambler From United States of America, joined Jul 2010, 302 posts, RR: 0 Reply 4, posted (2 years 2 months 3 weeks 3 days 3 hours ago) and read 2837 times:
Quoting LHCVG (Reply 3): I would think the fact that an analogous plane, the Super 27, has remained a niche private a/c speaks to the commercial viability of re-engining in most cases.
So, when I become obscenely rich, I can buy a fleet of used MD-80s for cheap and re-engine them? They'd be like rockets with the V2500! And I could add winglets and extra fuel tanks...
MD-90 From United States of America, joined Jan 2000, 8417 posts, RR: 13 Reply 5, posted (2 years 2 months 3 weeks 3 days 3 hours ago) and read 2825 times:
Quoting LHCVG (Reply 3): However, the V2500 from the MD90 might work on the assumption that an MD90 is relatively close to a late-build MD88 or one of the MD-82/3s built to MD88 specs.
Even worse weight problem than the BR715. MD didn't stretch the MD-8X fuselage to create the MD-90 for no reason.
KELPkid From United States of America, joined Nov 2005, 5929 posts, RR: 4 Reply 6, posted (2 years 2 months 3 weeks 3 days 2 hours ago) and read 2799 times:
Yeah, it seems that tail mounted engines usually lock you into what you got from the factory, mostly due to what replacing them will do to the aircraft's CG...any replacement engine is going to have to be of a similar weight to what it is replacing. You could maybe move the engines forward or back, but then your engineering costs go up, because you are then re-doing even more work that the McDD engineers did back in the late 1970's/early 1980's. Wing mounted engines have an advantage when it comes to re-enginning because the engines are much closer to the aircraf'ts center of gravity
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
SEPilot From United States of America, joined Dec 2006, 6256 posts, RR: 39 Reply 7, posted (2 years 2 months 3 weeks 3 days 2 hours ago) and read 2795 times:
I believe that AA has looked into the possibility of reengining the MD-80's as they have so many of them and they are such a durable airframe, and came to the conclusion that it is just not feasible. With a rear engined plane reengining is much more complicated than it is for one with engines on the wing; when they are on the wing they are very close to the CG and center of lift, so it is easy to compensate for different weights. On the tail if the new engine weighs significantly more than the original engine you have big problems and no good solutions.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
bohica From United States of America, joined Feb 2004, 2407 posts, RR: 0 Reply 8, posted (2 years 2 months 3 weeks 3 days 2 hours ago) and read 2794 times:
Quoting tsugambler (Thread starter): Many people have commented recently on the relative inefficiency of the MD-80 series vs. the 738, especially in the case of AA's huge fleet of MD-80s. My question is... could the MD-80s be re-engined with the Rolls-Royce BR715
A friend of mine who is an AA MD-80 pilot told me AA looked at the possibility of re-engining them with the BR715 but it would be too expensive and AA would have to replace them anyway.
boeing767mech From United States of America, joined Dec 2000, 992 posts, RR: 3 Reply 9, posted (2 years 2 months 3 weeks 2 days 18 hours ago) and read 2636 times:
Quoting bohica (Reply 8): A friend of mine who is an AA MD-80 pilot told me AA looked at the possibility of re-engining them with the BR715 but it would be too expensive and AA would have to replace them anyway.
AA looked into it, and did not want to go forward with the project due to the fact the of the cost versus return on investment, also due to the fact that you don't just slap the engines on. You have to rework the pneumatic system, remove and install different pylons and the electrical system had to be reworked to take a Intergrated Drive Generator IDG which includes an extra box installed to control, where the orginal Constant Speed Drive which the generator rides along with is all mechanical and doesn't require the extra black box. Also given the fact than the MD-80's have a major AD on the aft pressure bulkhead for cracking, adding another 4000 pounds to the aft pressure bulkhead to an alriady 15 plus year old airplane leads to more problems.
Just what I heard when I was at the MD-80 produce meeting a while ago when the subject came up.
Max Q From United States of America, joined May 2001, 3288 posts, RR: 19 Reply 10, posted (2 years 2 months 3 weeks 2 days 16 hours ago) and read 2602 times:
Its rarely economic to sink a lot of money into such an old airframe. Technological advances over the years have provided such a clear benefit to buying new generation Aircraft it's just not worth it.
There are exceptions, such as the reengining of the DC8 with the CFM56 but this program provided such an unprecedented leap in performance it was worth the expense.
AA also considered reengining their 727's and decided against it
They were also persuaded by an amazing deal to lease 260 MD80's from M Douglas.
Despite that, I think they made a poor choice as the MD80 was not really an adequate replacement for the 727, certainly in it's capacity.
They should have bypassed the MD's and waited for the 73NG
The best contribution to safety is a competent Pilot.
SEPilot From United States of America, joined Dec 2006, 6256 posts, RR: 39 Reply 11, posted (2 years 2 months 3 weeks 2 days 10 hours ago) and read 2524 times:
Quoting Max Q (Reply 10): There are exceptions, such as the reengining of the DC8 with the CFM56 but this program provided such an unprecedented leap in performance it was worth the expense.
The singular confluence of events that made this possible was really unique; an extraordinarily robust airframe, an engine already developed that was perfect for the plane, and the engine physically fitting without major modifications, and enough airframes available to make it financially worthwhile. Similar circumstances have not happened again, nor are they likely to.
Quoting Max Q (Reply 10): They should have bypassed the MD's and waited for the 73NG
They would have had to wait a long time; didn't they take the MD's in the late 80's? That would have been a long time to feed and maintain the thirsty 727's. Also, Boeing had just started delivering the 737Classic, and at that point had no intention of redoing it again. It was the success of the A320 that forced them into it.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
Max Q From United States of America, joined May 2001, 3288 posts, RR: 19 Reply 12, posted (2 years 2 months 3 weeks 1 day 19 hours ago) and read 2344 times:
Quoting SEPilot (Reply 11): The singular confluence of events that made this possible was really unique; an extraordinarily robust airframe, an engine already developed that was perfect for the plane, and the engine physically fitting without major modifications, and enough airframes available to make it financially worthwhile. Similar circumstances have not happened again, nor are they likely to.
Quoting Max Q (Reply 10):
They should have bypassed the MD's and waited for the 73NG
They would have had to wait a long time; didn't they take the MD's in the late 80's? That would have been a long time to feed and maintain the thirsty 727's. Also, Boeing had just started delivering the 737Classic, and at that point had no intention of redoing it again. It was the success of the A320 that forced them into it.
Good points SEPilot,
As you say, the DC8 was a unique program.
And you're right AA would have to have waited a long time to replace the 727 with a modern Aircraft of similar capacity.
I still think they would have been better off waiting but, it's true when they arranged the deal for the -80's the only 150 seat option was the A320 which they wouldn't buy and, later the 734 which was also, an inadequate replacement.
The MD80 was a compromise and a good deal at the time but they have held on to them way too long. It now represents a huge, inefficient part of their fleet and a constant drag on their already shaky finances.
The best contribution to safety is a competent Pilot.
SEPilot From United States of America, joined Dec 2006, 6256 posts, RR: 39 Reply 14, posted (2 years 2 months 3 weeks 1 day 11 hours ago) and read 2248 times:
Quoting Max Q (Reply 12):
I still think they would have been better off waiting but, it's true when they arranged the deal for the -80's the only 150 seat option was the A320 which they wouldn't buy and, later the 734 which was also, an inadequate replacement.
Hindsight is always 20-20. When AA had to make a decision the choices were the 737 and the MD-80. I had thought that they bought the MD-80's in the late 80's; after looking it up the first one was delivered in 1983, which meant that the 737Classic was not even yet available (although it was in development, and AA would have known it.) The A320 wasn't even launched when AA made their decision. At the time AA made the decision the MD-80 was really the best available option, and the only other option at the time, the 733, did not meet the requirements. Fuel was also much less of an issue then. What has emerged as the real problem has been the economic turmoil of the last 20 years that has kept all airlines in almost continual difficult financial straits, and AA, by not following all of the others into bankruptcy has made a more difficult, if more honorable, road, with little money for new aircraft.
Quoting Aviopic (Reply 13):
With tailpipe and reverser included I am quite sure the BR will weigh less than the JT
AA has investigated reengining, but have come to the conclusion that it is not economically viable. i don't know the details, but I do know that they investigated it.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
PITingres From United States of America, joined Dec 2007, 954 posts, RR: 12 Reply 15, posted (2 years 2 months 3 weeks 1 day 5 hours ago) and read 2188 times:
Wikipedia, which is of course fallable, gives 6155 lbs for the BR715-58. I couldn't find specific weight specs for the JT8D-2xx in just a few minutes of poking around; the -219 was listed as 4740 and presumably the -209 is a bit lighter. I ran across an FAA pdf that gives your BR-7xx number, but it looks like it's talking about the 700-30 which I understand is a bizjet engine.
Aviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 47 Reply 16, posted (2 years 2 months 3 weeks 1 day 4 hours ago) and read 2175 times:
There is always a danger incompatible weights are compared, the numbers I gave are dry engine weights without tailpipe and reverser.
A + 2000 lbs weight difference isn't logical though, that's almost 50% which is a number unheard of in our aviation world.
tsugambler From United States of America, joined Jul 2010, 302 posts, RR: 0 Reply 17, posted (2 years 2 months 3 weeks 20 hours ago) and read 2058 times:
Quoting Max Q (Reply 10): They should have bypassed the MD's and waited for the 73NG
The MD-80s may be inefficient by today's standards, but they weren't when they came out--they were considered quite efficient and very quiet. I'm sure AA thought they were making a good decision in acquiring them, and I think that (bearing the context in mind) they were right.
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