717 question:

StraightnLevel

StraightnLevel

Pre-takeoff checklist
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StraightnLevel
While waiting to board, I noticed the elevators on a 717 at the gate, and thought it a bit odd.

Anyone here know if it's normal to see the left and right control surfaces in different configurations?

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I think this is normal. As I recall, the DC-9's/MD-whatever/717 elevators are moved by servo tabs. The elevators are not linked and "float" until air loads on the servo tabs appropriately position them for flight.
 
I realize it is at the gate with ground power. But could you see the aileron at the same time? I do not know about the 717, but some aircraft do have differential elevators tied to aileron for roll assist. I know my old plane, above a certain speed, wing sweep, it was "aileron lockout" and roll control was solely by the differential horizontal stab.
 
BillTIZ said:
I realize it is at the gate with ground power. But could you see the aileron at the same time? I do not know about the 717, but some aircraft do have differential elevators tied to aileron for roll assist. I know my old plane, above a certain speed, wing sweep, it was "aileron lockout" and roll control was solely by the differential horizontal stab.
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You're right. The left aileron is slightly up. Can't see the right, but that makes sense.

Sorry for the stupid question, just hoping to learn something.
 
I thought the 717 like the md-90 had powered elevators…

Even still, they may not be tied together.

@kyleb is right, all dc-9 and md 80s up to the md-88 elevators are free floating. Aerodynamically driven by tabs.

FYI, I think the 717 is a md-95… I’ll bet a dollar.

Edit: no aileron interconnect. And GA pilots warned us all the time about the split elevators, which I NEVER minded, glad they were willing to speak up. Sadly, I was in the minority…

More edit: a md-80 is really a dc-9-80… was renamed to the “dash 80” or md-80 after McDonnell Douglas was formed.
 
StraightnLevel said:
You're right. The left aileron is slightly up. Can't see the right, but that makes sense.

Sorry for the stupid question, just hoping to learn something.
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there are no stupid questions..... wait... I have heard a couple... right after I explained something... just proves he was not listening..
 
BillTIZ said:
there are no stupid questions......
Click to expand...

Sadly just not true… someone once asked me if I wanted to eat Mexican.

Others have asked if I wanted a ride in their airplane.

There are probably other stupid questions. This one about the elevators isn’t.
 
Tools said:
Edit: no aileron interconnect. And GA pilots warned us all the time about the split elevators, which I NEVER minded, glad they were willing to speak up. Sadly, I was in the minority…

More edit: a md-80 is really a dc-9-80… was renamed to the “dash 80” or md-80 after McDonnell Douglas was formed.
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I felt like an ass a good while ago when I warned an MD-80 crew about the ailerons not being coordinated at the gate. The FO kindly explained the the servo tab thing.
 
Bill said:
I felt like an ass a good while ago when I warned an MD-80 crew about the ailerons not being coordinated at the gate. The FO kindly explained the the servo tab thing.
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Sure it wasn’t the elevators? The ailerons are bussed together with cables. Move one the other moves. This is the entire series. The elevator halves are not connected together so they split all the time with wind gusts. With no control lock either, this has caused a few crashes….

Hard to imagine a transport category jet without hydraulic primary flight controls (minus the rudder…). I was dumbfounded in class the first time! Couldn’t believe what I was hearing.
 
Tools said:
Sure it wasn’t the elevators? The ailerons are bussed together with cables. Move one the other moves. This is the entire series.
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Positive. Both ailerons were in the up position. The FO explained that they were controlled by servo tabs, and the winds at the gate had blown both ailerons up. He said they would move into the proper position on the takeoff roll as air flowed across the wings. And he was correct, they both fell into place after we got some speed going.
 
Tools said:
Hard to imagine a transport category jet without hydraulic primary flight controls (minus the rudder…). I was dumbfounded in class the first time! Couldn’t believe what I was hearing.
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On the DC9s, only the rudder was powered. The only hydraulic power to the elevators was for deep-stall recovery. It would push the elevators towards nose-down when the control columns were pushed forward without a corresponding movement in the elevators. I never flew the DC9-50, and longer, variants so they may have been different. The 717 is similarly-sized to the DC9-30 and DC9-40s that I flew. I would assume that is would be the same but I don't know the specifics.

On the DC8, the ailerons and rudder were powered but not the elevator. It was flown via control tabs in a manner similar to the DC9.

Bill said:
Positive. Both ailerons were in the up position. The FO explained that they were controlled by servo tabs, and the winds at the gate had blown both ailerons up. He said they would move into the proper position on the takeoff roll as air flowed across the wings. And he was correct, they both fell into place after we got some speed going.
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Can't happen unless the aileron bus cable is mis-rigged. If it is mis-rigged, the spoilers will not likely work when they are supposed to.

During the walk-around, we'd push one aileron up then check that the other one went down when we got to the other side.
 
Larry in TN said:
On the DC9s, only the rudder was powered. The only hydraulic power to the elevators was for deep-stall recovery. It would push the elevators towards nose-down when the control columns were pushed forward without a corresponding movement in the elevators. I never flew the DC9-50, and longer, variants so they may have been different. The 717 is similarly-sized to the DC9-30 and DC9-40s that I flew. I would assume that is would be the same but I don't know the specifics.

On the DC8, the ailerons and rudder were powered but not the elevator. It was flown via control tabs in a manner similar to the DC9.


Can't happen unless the aileron bus cable is mis-rigged. If it is mis-rigged, the spoilers will not likely work when they are supposed to.

During the walk-around, we'd push one aileron up then check that the other one went down when we got to the other side.
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The ailerons were not in phase, which is why I was a bit alarmed. But obviously the flight was normal.
 
NordicDave said:
What airline is still flying these relics? Maybe they have a connecting flight with a 727 or an L1011?
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717? Delta. I have been on 717s for 3 of my last four Delta flights. I get them quite often on the HOU-ATL route.

IIRC, Delta has the old AirTran (Valujet) fleet of 717s.
 
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MD-80s used a lot in ad hoc cargo. Some 727s running around doing that as well, all part 121 supplemental.

Some md87s are fire bombing.

There are some very serious maint issues…

Everts Air Cargo is still running DC-6s and one C-46 in part 121 operations, THOSE are relics!

They’re flying circling approaches to (real) minimums.
 
NordicDave said:
What airline is still flying these relics? Maybe they have a connecting flight with a 727 or an L1011?
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Delta and Hawaiian.

It is not very efficient, compared to modern alternatives, but that isn't as important on the short stage lengths that these airplanes typically fly. The A220 and E195-E2 would be good candidates for replacement. Delta has an A220 fleet.
 
Delta was actually buying MD80s not long ago.

They figured to buy and refurbish then operate over a number of years, they were still cheaper than a new plane with lower fuel consumption.
 
The MD80’s Delta purchased were for parts for their existing MD88 fleet. They did not operate them on revenue flights.
 
Tools said:
Sadly just not true… someone once asked me if I wanted to eat Mexican.

Others have asked if I wanted a ride in their airplane.

There are probably other stupid questions. This one about the elevators isn’t.
Click to expand...
Wanna ride in my plane and we’ll fly to a Mexican restaurant?
 
Tools said:
(S)omeone once asked me if I wanted to eat Mexican.

Others have asked if I wanted a ride in their airplane.
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Well, there is a really good Cantina about 1/4 mile down the road from a very pretty grass strip I know of. Even has blended Virgin Mararitas.

$100 Chiliques . . ..
 
Look, basically two more stupid questions!!

Y E S! Now I’m stahvin…. Ha!!
 
I was at KLGB when the last 717 left the plant and Long Beach for good... Then went the C-17 manufacturing..

Oh well.... end of an era.. But they still have the sign..

fly-dc-jets-heidi-smith.jpg
 
Didn’t Delta also inherit all the world’s DC-9s when they merged with Northwest? I miss those things. The ND routes they had served got CRJs and, if there is a comfortable seat to be found in a CRJ, it’s not in the passenger cabin. Fortunately they are moving some of those routes to ERJs of late. But a 717 would still be more comfortable.
 
iamtheari said:
Didn’t Delta also inherit all the world’s DC-9s when they merged with Northwest? I miss those things. The ND routes they had served got CRJs and, if there is a comfortable seat to be found in a CRJ, it’s not in the passenger cabin. Fortunately they are moving some of those routes to ERJs of late. But a 717 would still be more comfortable.
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Delta has quite the history of operating DC9 variants, including those they acquired from the NWA merger.

Their last DC9 was parked in 2014 and their last MD88/MD90 in 2020. That leaves just the B717s, which would have been MD-95s if not for the MD/Boeing merge.
 
This explains elevator asymmetry the way I had it explained in the past.
(about the 3rd response)
 
Let'sgoflying! said:
This explains elevator asymmetry the way I had it explained in the past.
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The each elevator's movement is not connected in anyway. They are each free to float up or down independently of the other. In flight, they work together only because the each have a control tab. The control tabs work together based on control column input.

Aileron movement is coordinated by the aileron bus cable in a way very similar to a typical G.A. airplane. The difference is that the aileron bus cable is not connected to yoke inputs. Yoke inputs move the control tabs on each aileron but aileron movement does not move the control tabs or the yoke.
 
From what I remember hearing from the few guys that belonged to our club was the Boeing put in better engines, and few other upgrades in avionics, and passenger amenities (more seats less space :)), and such, but pretty much left the airframe alone..

My neighbor worked on the C-17 program and we got a chance to tour the plant on Employee Appreciation Day... wow....
 
Ventucky Red said:
?????????
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It's a joke about the DC-series controls being all cables and pulleys, when in reality we all know the 'DC' in DC-9 stood for 'direct cable.' :cool:

(ETA: H/T to Capt. Doug of rec.aviation :biggrin:)

Nauga,
and his ratio changer
 
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Ventucky Red said:
?????????
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The joke is that DC stands for "Douglas Cable", or "Direct Cable" and references the amount of cables that run from the cockpit to every corner of the airframe. This was particularly true of the DC8.

Here's a DC8 engineer's panel. All those levers on the lower section are fuel valves and are connected, by cable, to all of the fuel valves in the wing. Just to the left is the "cash register" with levers connecting to the outflow valve in the tail and the temperature control valves. The overhead (not pictured) fire handles connect by cables to the engine nacelles to shut off the pnuematics, fuel, electrics (field relays), and hydraulics to isolate an engine at the pylon. The flight controls, of course, have cables running all the way to each flight control including the spoiler handle. I couldn't find a picture of all the cables in the wheel well including the "rocking horse" which was a series of levers and pullies which combined inputs from the aileron bus cable, flap bus cable, and others, to pull cables which operated the spoiler actuators. The wheel well was full of cables.

1736090654207.png
 
nauga said:
It's a joke about the DC-series controls being all cables and pulleys,
Click to expand...

Larry in TN said:
The joke is that DC stands for "Douglas Cable", or "Direct Cable" and references the amount of cables that run from the cockpit to every corner of the airframe.
Click to expand...


Got it... lived in Long Beach for 10 years and never saw a cable car...
 
Jeff767 said:
The MD80’s Delta purchased were for parts for their existing MD88 fleet. They did not operate them on revenue flights.
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There was an article somewhere that they were refurb and flying them. Maybe not -80s, but some series of MDs.

Again, the purchase plus refurb and higher op costs were cheaper over some number of years than a new airplane with lower op costs.
 
Ventucky Red said:
From what I remember hearing from the few guys that belonged to our club was the Boeing put in better engines, and few other upgrades in avionics, and passenger amenities (more seats less space :)), and such, but pretty much left the airframe alone..
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It wasn't Boeing, it was MD that made the changes. Development of the MD-95 was pretty much done when Boeing took over and renamed it the 717.
 
Jeff Oslick said:
It wasn't Boeing, it was MD that made the changes. Development of the MD-95 was pretty much done when Boeing took over and renamed it the 717.
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Interesting.. Mr. Goggle comes back with this

Boeing did change the engines on the 717 compared to its predecessor, the MD-95. The Boeing 717 is equipped with two Rolls-Royce BR715 turbofan engines mounted at the rear of the fuselage

This was a significant change from the original engine plans for the MD-95.Initially, the MD-95 was proposed with two potential engine options:

A 16,500 lbf (73 kN) thrust derivative of the JT8D-200 series
The Rolls-Royce Tay 670
https://en.wikipedia.org/wiki/Boeing_717
However, during the development process, McDonnell Douglas found the BMW Rolls-Royce BR700 engine to be the ideal candidate for the aircraft. On February 23, 1994, the BR700 was selected as the sole powerplant for the airliner
The Rolls-Royce BR715 engines on the 717 offer several advantages over previous designs:

  1. More powerful: They provide up to 21,430 lbf (95.3 kN) of thrust per engine, compared to the up to 16,000 lbf (71 kN) of the Pratt & Whitney JT8D engines used on the earlier DC-9
    https://simpleflying.com/boeing-717-mcdonnell-douglas-dc-9-differences-list/
  2. Fuel efficiency: The new-technology engines are more fuel-efficient, particularly on longer flights
    https://simpleflying.com/boeing-717-mcdonnell-douglas-dc-9-differences-list/
  3. Maintainability: Boeing claims that the BR715 engines are some of the most maintainable engines in the market, enabling longer time between maintenance visits and shorter downtime during maintenance
    https://simpleflying.com/boeing-717-mcdonnell-douglas-dc-9-differences-list/
In summary, Boeing did change the engines on the 717, opting for the more modern and efficient Rolls-Royce BR715 turbofans, which represented a significant upgrade from the originally proposed engines for the MD-95.
Click to expand...
 
Ventucky Red said:
Interesting.. Mr. Goggle comes back with this
Click to expand...
Mr. Google says that a Cub is a lawnmower built by Honda, with a Briggs and Stratton engine, that first flew in 1934.

And although it had several merit badges, it had yet another losing season.
 
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