Smokint From , joined Dec 1969, posts, RR: Posted (6 years 10 months 3 weeks 5 days 15 hours ago) and read 10636 times:
I fly out of SLC on DL frequently, many times on the MD-90. I notice we always seem to cruise in the FL290-330 range. Is this due to this type's wing? If so, is this limiting as far as weather, turbulence avoidance, etc?
IAHFLYR From , joined Dec 1969, posts, RR:
Reply 1, posted (6 years 10 months 3 weeks 5 days 4 hours ago) and read 10563 times:
The cruising altitude is determined by many different items such as length of segment, winds, aircraft weight, turbulence, possible vertical restrictions ATC may put in place for certain routes from a particular city, as well as other variables which others in this forum are more versed than myself.
The MD-90-30 (which ended up being the only MD-90 series ever built) got a nose stretch over the MD-80 (heavier) and a tail stretch (heavier) and also new engines (far heavier). Not to mention more avionics (heavier), and new VSCF generators (lights, but they never work, so kind of a moot point).
So it's far heavier.
And they didn't change the wing from the MD-80 at all.
The MD-80 isn't a particularly great cruiser, to start off with... long routes with high fuel loads typically start to cruise at 29000, then climb bit by bit along the way. I myself have experience this many times, typically on AA's MD-82 and even the -83, which has uprated Pratt JT-8D-219C engines over the MD-82's -217s.
The MD-90 is a great aircraft to fly on, in my opinion, and as solid as the rest of the overbuilt Douglas line.
But its wings are its weakest point.
A 4% increase in maximum takeoff weight is not normally considered "far heavier." Especially when you consider the MD90 had a 50% increase in thrust.
Quoting PGNCS (Reply 7): It generally cruises a bit lower than a comparable MD-80...
IF true, it is not due to the design of the plane or its operating economics. When comparing MD80 vs. MD90 operating the same route, the MD90 will normally operate at higher altitudes for longer periods of time --climbs faster, cruises faster, descends quicker-- but for such a comparison to be valid it must be made comparing the same route, same weather conditions and similar payloads. Bottom line is that with no artificial limits (primarily ATC or company issues) the MD90 wants to fly higher, faster and farther than any MD80.
AAR90 From , joined Dec 1969, posts, RR:
Reply 11, posted (6 years 10 months 1 week 6 days 16 hours ago) and read 9680 times:
Thanks for the update Viscount. Not sure when FAA reduced the max altitude, but when I flew it we were regularly at FL410 for the hour long intra-CA flights. Perhaps a "standardization" move ala B757 --which used to have a max altitude of FL42.5, but FAA reduced that in a "clarification" to the charts. As with the MD90... nothing changed on the plane except the official limit.
AAR90 From , joined Dec 1969, posts, RR:
Reply 14, posted (6 years 10 months 1 week 6 days 3 hours ago) and read 9604 times:
Quoting MD-90 (Reply 12): How long did it take to climb to FL410?
Around 15-16 minutes. When we flew this high the cruise portion was very short... perhaps 10 minutes. Then it was a long gliding descent. If we didn't get the high altitude quickly enough, we'd get stuck underneath WN 737s and then ATC would require us to fly slow to stay behind them.
Quoting Smokint (Reply 13): AAR90, are you saying this is just due to Delta policy?
I haven't got a clue as to Delta's policies... I am AA and was flying ex-QQ MD90's.
On FlightAware, MD82's seem to have a wider range of cruising altitudes and are usually higher than at least the Delta MD-90's
There are a lot of reasons used in choosing a cruising altitude... fuel consumption is but one. Whenever we were trying to catch up to published scheduled times we would choose high 20's/low 30's for max ground speed (least time enroute) and there were many times I choose 16-17k just to avoid turbulence near SBA --which is almost always there on N/S coastal routes, but much less at low altitudes. The difference in fuel cost (back then) wasn't very much at all.
MD-90 From , joined Dec 1969, posts, RR:
Reply 15, posted (6 years 10 months 1 week 5 days 13 hours ago) and read 9538 times:
Quoting AAR90 (Reply 14):
Around 15-16 minutes. When we flew this high the cruise portion was very short... perhaps 10 minutes. Then it was a long gliding descent. If we didn't get the high altitude quickly enough, we'd get stuck underneath WN 737s and then ATC would require us to fly slow to stay behind them. Sad