smokint
Posts: 4
Joined: Sun Aug 10, 2008 4:32 am

MD-90 Cruising Altitude

Sun Aug 10, 2008 4:38 am

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
 
IAHFLYR
Posts: 3943
Joined: Sat Jun 25, 2005 12:56 am

RE: MD-90 Cruising Altitude

Sun Aug 10, 2008 3:21 pm

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.
 
smokint
Posts: 4
Joined: Sun Aug 10, 2008 4:32 am

RE: MD-90 Cruising Altitude

Sun Aug 10, 2008 5:35 pm

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.
 
AA737-823
Posts: 4905
Joined: Wed Mar 01, 2000 11:10 am

RE: MD-90 Cruising Altitude

Mon Aug 11, 2008 12:21 pm



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.
 
smokint
Posts: 4
Joined: Sun Aug 10, 2008 4:32 am

RE: MD-90 Cruising Altitude

Mon Aug 11, 2008 4:14 pm

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?
 
FlyASAGuy2005
Posts: 3965
Joined: Sun Sep 23, 2007 4:55 am

RE: MD-90 Cruising Altitude

Tue Aug 12, 2008 11:04 am

OK so here's my question. What's the official service ceiling of the MD-90?
What gets measured gets done.
 
KingAir200
Posts: 668
Joined: Sun May 28, 2006 1:37 pm

RE: MD-90 Cruising Altitude

Wed Aug 13, 2008 1:24 pm



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.
 
PGNCS
Posts: 2249
Joined: Sun Apr 15, 2007 5:07 am

RE: MD-90 Cruising Altitude

Wed Aug 13, 2008 3:40 pm



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).
 
Oykie
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Joined: Sat Jan 07, 2006 9:21 am

RE: MD-90 Cruising Altitude

Fri Aug 22, 2008 11:52 am



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
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: MD-90 Cruising Altitude

Fri Aug 22, 2008 4:12 pm



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!
 
Viscount724
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Joined: Thu Oct 12, 2006 7:32 pm

RE: MD-90 Cruising Altitude

Sat Aug 23, 2008 1:53 am



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)
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: MD-90 Cruising Altitude

Sat Aug 23, 2008 2:53 am

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!
 
MD-90
Posts: 7835
Joined: Mon Jan 17, 2000 12:45 pm

RE: MD-90 Cruising Altitude

Sat Aug 23, 2008 5:13 am



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?
 
smokint
Posts: 4
Joined: Sun Aug 10, 2008 4:32 am

RE: MD-90 Cruising Altitude

Sat Aug 23, 2008 7:34 am

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
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: MD-90 Cruising Altitude

Sat Aug 23, 2008 4:20 pm



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!
 
MD-90
Posts: 7835
Joined: Mon Jan 17, 2000 12:45 pm

RE: MD-90 Cruising Altitude

Sun Aug 24, 2008 6:28 am



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.
 
PGNCS
Posts: 2249
Joined: Sun Apr 15, 2007 5:07 am

RE: MD-90 Cruising Altitude

Fri Aug 29, 2008 5:09 pm

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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