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MD-90 Cruising Altitude  
User currently offlineSmokint From United States of America, joined Aug 2008, 4 posts, RR: 0
Posted (5 years 11 months 3 weeks 2 days 1 hour ago) and read 8841 times:

Greetings aviators,

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?

Thank you for your time,

Robert

16 replies: All unread, jump to last
 
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 1, posted (5 years 11 months 3 weeks 1 day 15 hours ago) and read 8768 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.


Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineSmokint From United States of America, joined Aug 2008, 4 posts, RR: 0
Reply 2, posted (5 years 11 months 3 weeks 1 day 12 hours ago) and read 8724 times:

Thanks, IAH, but it seems to me that this aircraft type is always in the lower flight levels, e.g. :

http://flightaware.com/live/aircrafttype/MD90

I fly a lot of RJ's as well and even the anemic CRJ-100 will fly to FL350 on shorter routes.

Seems I remember something about this plane having a "relatively" small wing, could that be true?

Thanks again.


User currently offlineAA737-823 From United States of America, joined Mar 2000, 5725 posts, RR: 11
Reply 3, posted (5 years 11 months 3 weeks 18 hours ago) and read 8589 times:



Quoting Smokint (Thread starter):
I fly out of SLC on DL frequently, many times on the MD-90.

Lucky you.

Quoting Smokint (Thread starter):
Is this due to this type's wing?

Yes.

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.


User currently offlineSmokint From United States of America, joined Aug 2008, 4 posts, RR: 0
Reply 4, posted (5 years 11 months 3 weeks 14 hours ago) and read 8549 times:

Thanks AA737,

I like flying it because it has the 2 + 3 seating and seems very quiet.

Is it much of a disadvantage to be stuck in the lower FL's?


User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 5, posted (5 years 11 months 2 weeks 6 days 19 hours ago) and read 8409 times:

OK so here's my question. What's the official service ceiling of the MD-90?


What gets measured gets done.
User currently offlineKingAir200 From United States of America, joined May 2006, 1611 posts, RR: 2
Reply 6, posted (5 years 11 months 2 weeks 5 days 16 hours ago) and read 8251 times:



Quoting FlyASAGuy2005 (Reply 5):
OK so here's my question. What's the official service ceiling of the MD-90?

I can't say for sure, but I think it is 37,000 feet.



Hey Swifty
User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 7, posted (5 years 11 months 2 weeks 5 days 14 hours ago) and read 8234 times:



Quoting FlyASAGuy2005 (Reply 5):
What's the official service ceiling of the MD-90?

37,000 feet.

It generally cruises a bit lower than a comparable MD-80, but has much better takeoff and climb performance up to somewhere in the 20's (exactly where depends on weight and temp).


User currently offlineOyKIE From Norway, joined Jan 2006, 2726 posts, RR: 4
Reply 8, posted (5 years 11 months 1 week 3 days 18 hours ago) and read 7990 times:



Quoting Smokint (Thread starter):
If so, is this limiting as far as weather, turbulence avoidance, etc?

The benefit with that small wing is that the wing loading per square feet is much higher and that makes the plane more stable in turbulence than it's competitors.



Dream no small dream; it lacks magic. Dream large, then go make that dream real - Donald Douglas
User currently offlineAAR90 From United States of America, joined Jan 2000, 3466 posts, RR: 47
Reply 9, posted (5 years 11 months 1 week 3 days 14 hours ago) and read 7952 times:



Quoting FlyASAGuy2005 (Reply 5):
What's the official service ceiling of the MD-90?

FL410.

Quoting AA737-823 (Reply 3):
So it's far heavier.

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.



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineViscount724 From Switzerland, joined Oct 2006, 24843 posts, RR: 22
Reply 10, posted (5 years 11 months 1 week 3 days 4 hours ago) and read 7894 times:



Quoting PGNCS (Reply 7):
Quoting FlyASAGuy2005 (Reply 5):
What's the official service ceiling of the MD-90?

37,000 feet.



Quoting AAR90 (Reply 9):
Quoting FlyASAGuy2005 (Reply 5):
What's the official service ceiling of the MD-90?

FL410.

Excerpt from FAA Type Certification Data Sheet for DC-9/MD-80/MD-90/B-717:

Maximum Operating Altitude
35,000 ft. (DC-9-11 thru DC-9-51)
37,000 ft. (DC-9-81, -82, -83, -87, MD-88, MD-90-30 and 717-200)


User currently offlineAAR90 From United States of America, joined Jan 2000, 3466 posts, RR: 47
Reply 11, posted (5 years 11 months 1 week 3 days 3 hours ago) and read 7885 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.


*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineMD-90 From United States of America, joined Jan 2000, 8502 posts, RR: 12
Reply 12, posted (5 years 11 months 1 week 3 days 1 hour ago) and read 7868 times:



Quoting AAR90 (Reply 11):
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

How long did it take to climb to FL410?


User currently offlineSmokint From United States of America, joined Aug 2008, 4 posts, RR: 0
Reply 13, posted (5 years 11 months 1 week 2 days 22 hours ago) and read 7849 times:

Hmmm, I fly the MD90 quite a bit and I've never been above FL340 in it (as a passenger, of course).

AAR90, are you saying this is just due to Delta policy?

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


User currently offlineAAR90 From United States of America, joined Jan 2000, 3466 posts, RR: 47
Reply 14, posted (5 years 11 months 1 week 2 days 14 hours ago) and read 7809 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.  Sad

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.

Quote:

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.



*NO CARRIER* -- A Naval Aviator's worst nightmare!
User currently offlineMD-90 From United States of America, joined Jan 2000, 8502 posts, RR: 12
Reply 15, posted (5 years 11 months 1 week 1 day 23 hours ago) and read 7743 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

Now that definitely makes sense.


User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 16, posted (5 years 11 months 3 days 13 hours ago) and read 7515 times:

Quoting AAR90 (Reply 9):
Quoting FlyASAGuy2005 (Reply 5):
What's the official service ceiling of the MD-90?

FL410.

Not in our limitations section, nor on the FAA type certificate; it is FL 370.

[Edited 2008-08-29 10:14:19]

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