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Questions tagged [dc-9-family]

A twin-engine, T-tail, regional to medium-range jet airliner produced from 1965 until 2006, first by Douglas, followed by McDonnell Douglas, and then, finally, by Boeing.

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Why does the DC-9 have engines that are angled slightly upwards?

As per subject, I see that the above mentioned aircraft and some others that have engines mounted on the rear of the fuselage, have the engine intakes tilted slightly upwards. Why has this solution ...
Fabrizio Mazzoni's user avatar
18 votes
1 answer
5k views

Why is the DC-9-80 ("MD-80") prohibited from taking off with a flap setting between 13 and 15 degrees?

A bit of digging into the 7Z9363 accident investigation has brought up some interesting information regarding the DC-9-80 ("MD-80")'s flap system: Flaps may be positioned in any of the six ...
Vikki's user avatar
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16 votes
7 answers
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Why was the DC-9-80/MD-80 so successful despite being obsolete almost from birth?

The McDonnell Douglas DC-9-80/MD-80 series of narrowbody jetliners was the second-to-last DC-9 major version produced (from 1979 through 1999), the second-largest, the most-produced (just under half ...
Vikki's user avatar
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16 votes
1 answer
4k views

Why is the MD-80 magnetic compass behind the first officer's seat?

I was watching this video about the MD-83 magnetic compass and I found it interesting that it's designed the way it is. I'm not sure which of the airplanes in this series featured this strange ...
ryan1618's user avatar
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13 votes
4 answers
5k views

Why does the DC-9-80/MD-80 have this cusp in its fuselage?

The fuselage of the McDonnell Douglas DC-9-80 (also known as the "MD-80") has a pronounced cusp at floor level, as can be seen in this diagram (courtesy of Boeing, eater of McDonnell Douglas - at ...
Vikki's user avatar
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13 votes
1 answer
1k views

Why does the MD-87 have strakes on its engines?

Apparently, the MD-87 has a strake on both engines: Source: Airliners.net If I'm not wrong, the engine strake attaches the airflow at high angles of attack on the wing. But in this case the engine is ...
user13197's user avatar
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12 votes
5 answers
15k views

Why do airliners have "pressure bulkheads"?

Image source: FAA What part of the fuselage aft of the bulkhead would leak pressure? Or is it just there to reduce stresses? How does a DC-9/MD-80/90 incorporate aft bulkheads when there's a ...
user avatar
12 votes
1 answer
2k views

What is this hole on the tail of an MD-88?

There's a little hole on the leading edge of the vertical stabilizer of this plane: What is that? What is its purpose? Thanks Source: Airliners.net
user13197's user avatar
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11 votes
2 answers
3k views

Does the MD-80 seat layout affect the balance of the aircraft?

The MD-80 family has a 2-3 seat layout as seen in this image: Does the layout have any influence on the balance of the aircraft and if so what is used to balance out the weight? Image from seatguru....
SMS von der Tann's user avatar
10 votes
1 answer
2k views

Was this a successful deployment of an MD-88 tail cone evacuation slide?

In this video, the tail cone is popped off as part of the evacuation. It stays attached on a lanyard which seems to be more of a hazard than letting it fall free. Additionally, the slide doesn't ...
Simon's user avatar
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8 votes
2 answers
3k views

Why is the empennage of some aircraft not placed on the centerline?

Check the MD80's empennage below. Can easily tell it's not built on exactly centerline by naked eyes. Is that because aluminum joint or consider aerodynamics? I don't think it is manufacturing ...
ReinFore's user avatar
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8 votes
1 answer
900 views

Did the DC-9 ever use RATO in revenue service?

While reading the NTSB report on the crash of ALM Flight 980, I came across this interesting tidbit: ... The fuel charts used for the study made allowance for a higher consumption rate than the ...
Vikki's user avatar
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7 votes
2 answers
1k views

What is the round thing on the tip of an MD-90 wing?

I like to pretend I know about airplanes, but have always wondered what the round things on the tip of MD-90 wings are. Here is an image of what I am talking about: To be clear, my question is what ...
Murenrb's user avatar
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5 votes
1 answer
637 views

Does the MD-90 use a different elevator system from the other DC-9 versions?

While reading the 7Z9363 (a 2017 DC-9-80 [“MD-80”] very-high-speed rejected takeoff and runway overrun resulting from an undetectable wind-induced elevator jam that rendered the aircraft unable to ...
Vikki's user avatar
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3 votes
1 answer
3k views

How is the debris deflector on the DC-9-80 ("MD-80")'s nose gear kept from striking the ground during landing?

The DC-9-80 (marketed as the "MD-80") has, mounted to its nose gear, what I presume to be a debris deflector (a sled-shaped device to keep the nose gear from kicking up pieces of gravel or ...
Vikki's user avatar
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3 votes
3 answers
833 views

MD81: Why are there so many lights on the fuselage?

Looking at this photo I can see lots of lights on the fuselage of this MD81. It can't be a reflection, can it? Source: Airliners.net Why are there so many lights?
user13197's user avatar
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3 votes
2 answers
715 views

Why do the DC-9’s three-phase electrical systems use separate, unconnected breakers for each phase?

Aircraft electrical systems use two types of electricity: Direct current (DC),1 which always travels in the same direction (can be supplied directly from the aircraft’s battery, if necessary, but ...
Vikki's user avatar
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3 votes
1 answer
403 views

What about the DC-9's wing makes wingletting it so difficult?

A common way of making older airliners more efficient without increasing their wingspan is to add winglets, either as a retrofit for existing aircraft or as a new, wingletted derivative of a ...
Vikki's user avatar
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1 vote
1 answer
828 views

What prevents DC-9 series aircraft from being reengined with more-efficient engines?

All DC-9s except for the MD-90\B717 series use old, inefficient Pratt & Whitney JT8D series low-bypass turbofans, even the best of which have a paltry 1.74:1 bypass ratio. We know that a DC-9 can ...
Vikki's user avatar
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1 vote
1 answer
558 views

Why does the DC-9's antiskid system have to be manually disarmed during landing rollout following a ground-shift-mechanism malfunction on takeoff?

An aircraft's ground-shift mechanism (usually a sensor wired to the nosegear strut that looks to see whether the strut is compressed or not) tells the aircraft whether it's on the ground or in the air....
Vikki's user avatar
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1 vote
2 answers
802 views

Can I act as SIC with these specific type ratings?

Can I act as SIC on a part 91 ferry flight, if I hold... a DC-9 type rating and the flight is in an MD-80? a B-737 type rating, can I act as SIC on a B-737NG?
Steven sullivan's user avatar
1 vote
1 answer
252 views

How much do a DC-9's wings weigh?

How much do the wings weigh? How much does the landing gear weigh? How much fuel does it take to fill the tanks? We, at Confederation College are trying to donate a DC-9 for training purposes and ...
Charlene Hansen's user avatar
1 vote
0 answers
173 views

What is the big hole at the bottom of the vertical stabilizer on the Boeing 717? [duplicate]

What is the big hole located on the forward vertical stabilizer's bottom used for? (Image source)
J. Casas's user avatar
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0 votes
1 answer
119 views

Where can I find information on the DC-9's turn radius in flight?

Does anyone know where I can find information on a DC-9-30's turn radius at various altitudes and airspeeds? I've tried Googling it, but all I've found is information about its turn radius while ...
Vikki's user avatar
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