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20 MD80s retired in one day by American Airlines

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August 26th, 2016 at 7:13:29 AM permalink
Pacomartin Member since: Oct 24, 2012 Threads: 1068 Posts: 12569	Even the remaining ones average 22 years old.

August 26th, 2016 at 7:21:58 AM permalink

Nareed

Member since: Oct 24, 2012
Threads: 346
Posts: 12545

The DC-9 and its descendants right up to the B-717, had a sleek look for an airliner, which hasn't been matched since. Thought he B727 and its variants came closest.

Not to mention that years of having flown in DC-9s and 727s, got me used to a wing unencumbered by engines. To this day, I find it odd that most narrow bodies have engines on the wings. it feels wrong.

Donald Trump is a one-term LOSER

August 26th, 2016 at 8:25:15 AM permalink
Fleastiff Member since: Oct 27, 2012 Threads: 62 Posts: 7831	Quote: Nareed ... have engines on the wings. it feels wrong. Not to the maintenance personnel.

August 26th, 2016 at 9:04:52 AM permalink

Ayecarumba

Member since: Oct 24, 2012
Threads: 89
Posts: 1744

Quote: Fleastiff
Not to the maintenance personnel.

I always thought about it like a train. I don't know why, but it is harder to push a train than to pull it. I think the same about the DC-9, MD-80, and L-1011.

Here is a neat summary from Quora.com of an article on Stanford University's Aircraft Aerodynamics and Design Group web page:

Quote: Quora Summary

Reasons for aft fuselage-mounted engines:

-- The wing will produce more lift and less drag without engines on it.
-- Less asymmetric yaw after engine failure since the engines are closer to the middle of the fuselage
-- The aircraft can be closer to the ground, allowing shorter (and therefore lighter) landing gear and airstairs.

Reasons for wing-mounted engines:

-- With aft fuselage-mounted engines, the center of gravity of the empty aircraft is significantly aft of the center of gravity of the payload, resulting in a large difference in center of gravity locations when the aircraft is full and empty. This generally requires a larger tail (which is heavier and produces more drag) to be able to balance the aircraft in all conditions.
-- A T-tail is required for aft fuselage-mounted engines to avoid disturbing the flow into the engines at high angles of attack. However, at high angles of attack, the wake from the engines will blanket the tail, so the tail must be of long enough span to still provide control authority in this case.
-- Wings naturally want to bend upwards while producing lift, and must be structurally strengthened so that they don't bent too much, which adds weight. Wing-mounted engines counteract the upwards bending moment and allow the wing to be lighter.
-- The wheels kick up water on wet runways and special deflectors on the gear may be needed to avoid water ingestion into aft fuselage-mounted engines.
-- Vibration and noise isolation for fuselage-mounted engines is a difficult problem.
-- Aft fuselage-mounted engines reduce the rolling moment of inertia. If there is a significant rolling moment created by asymmetric stalling, the result can be an excessive roll rate at the stall

August 26th, 2016 at 9:20:39 AM permalink
Pacomartin Member since: Oct 24, 2012 Threads: 1068 Posts: 12569	Prototype of an electric plane that does vertical take off and landing.

August 26th, 2016 at 10:54:42 AM permalink

Nareed

Member since: Oct 24, 2012
Threads: 346
Posts: 12545

Quote: Ayecarumba
I always thought about it like a train. I don't know why, but it is harder to push a train than to pull it. I think the same about the DC-9, MD-80, and L-1011.

Let's look at single-engine planes. Prop planes usually have the engine on the nose (witch exceptions, mostly by Burt Rutan). Jets have the engine at the tail.

Come to think of it, almost all jet fighters have their engines at the tail.

And how'd you classify Concorde? A delta wing is its own tail. In any case, the engines were at the very back of the wing.

As with most everything else, the placement of the engines is decided by a series of design and effect trade-offs.

In passenger jets, smaller ones tend to have rear engines, while larger ones get engines on the wings. The DC-10, MD-11 and L-1011 had a tail engine because they made do with three engines. You could have placed two engines on one wing and one on the other, but then the plane would yaw in the direction of the one-engine wing, requiring rudder to keep it flying straight. In general you ant the thrust to be symmetrical. So two engines on the wings and one on the tail. The third engine might have gone anywhere on the centerline, BTW. But putting it, say, on top of the fuselage would have required a split vertical stabilizer and rudder. Under the fuselage would require a very tall landing gear (think a plane that looks like a stork).

The other advantage of rear engines on a passenger jet is a quieter cabin forward. Though if you ever sat near the back on a DC-9 or 727, it was very loud back there.

Donald Trump is a one-term LOSER

August 26th, 2016 at 11:25:36 AM permalink
DRich Member since: Oct 24, 2012 Threads: 51 Posts: 4967	Quote: Nareed Let's look at single-engine planes. Prop planes usually have the engine on the nose (witch exceptions, mostly by Burt Rutan). Jets have the engine at the tail. How would you classify the Skymaster? At my age a Life In Prison sentence is not much of a detrrent.

August 26th, 2016 at 11:50:50 AM permalink
Nareed Member since: Oct 24, 2012 Threads: 346 Posts: 12545	Quote: DRich How would you classify the Skymaster? I'd have to see one. But I'm sure I hedged my statements with a "usually" or an "almost." I almost always do this :) Donald Trump is a one-term LOSER

August 26th, 2016 at 12:14:37 PM permalink
DRich Member since: Oct 24, 2012 Threads: 51 Posts: 4967	Quote: Nareed I'd have to see one. But I'm sure I hedged my statements with a "usually" or an "almost." I almost always do this :) At my age a Life In Prison sentence is not much of a detrrent.

August 26th, 2016 at 12:28:24 PM permalink
Nareed Member since: Oct 24, 2012 Threads: 346 Posts: 12545	Oh, I see. Thanks. Obviously it's not meant to move at all :) Regardless, I'd classify it as textbook eccentric. But I do notice the thrust is balanced. Donald Trump is a one-term LOSER

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