DC9/MD80 FAMILY

[Yan104]

Hello!

I just registered on this great community obviously frequented by professionals in all fields of aviation, from ground staffes, to the aeronautical engineers and maintenance technicians, trough cabin crew and airline pilots! ! ... Suffice to say that for a passionate of world aviation like me, it's a great honor to be able to rub shoulders and share my ideas and information from various documents that I publish different sites, including Wikipedia, both driving techniques, aircraft design, and even the investigation of air crash which I could draw some reports in french! ...Yes, I am French, and I ask you please to forgive my errors in English ...

So I post my first topic dedicated to the history and career of my great loves garlic! ... I must confess having a special affection for this slender silhouette swallow that was the DC9, especially for seniors family, series 10 to 50. Those planes seem had not yet to have a rest for all, with various incidents and accidents they have experienced, and for many of them, they were not responsible. I thought I noticed however some extreme sensitivity of their electrical system, especially with incident that occurred in 1981 on a DC9-31 of Air Canada, and the terrible accident of DC9-32 of Valujet in 1996 . What can explain this phenomenon?

During the early 60’s , the entity Mc Donell Douglas was not yet formed . It was Douglas Aircraft Corp. , which produced the DC9 -10 in 1963. The direct competitors of DC9 were therefore Caravelle and BAC 1-11 : I may know that the Caravelle was produced in ten variants , while the Bac 1-11 was produced in four versions , the series 100 to 500 . This plane was particularly underpowered with its reactors Spey , which was I think one of the reasons for his business failure. The low modularity of his cell was the other factor ... But was it also the case for the Caravelle, that has not had as much success as the DC9 and B737 ?

More generally, the densification of the traffic in the area of the Middle Courier had she exploded between 1960/1970, that variants adapted to the requirements of each line, displayed with capacities from 80 to 110 seats? U.S. domestic traffic is not boosted the aircrafts sellings more than flights between European countries?


By the hope of answers

[DaveReidUK]

Bienvenue à PPRuNe!

Sadly, your translator has mangled your text to the extent that it's difficult to know exactly what you are asking.

PM me your question (in the original French) and if I can't answer it then at least I will try to re-state it in more easily understandable terms.

[flarepilot]

HI to our Gallant French Friends:

The DC9 is a great plane...the crash by valuejet had little to do with the electrical system

and the fire aboard the air canada flight was an unusual one with the blame on the electric motor operating the toilet pumping ;mechanism and a circuit breaker that was either reset or not working right.

the DC9 has a robust and easy to understand electrical system

The airframe is robust and the engines ( or reactors as you called them...not nuclear) are very reliable.

The DC9 is considered and often called, "The last PILOTs airliner". Less buttons more being one with the plane.

[Yan104]

Hello Flarepilot,

I specified in my text that the majority of incidents and accidents what have known the DC9 were not due to their technical design. On Wikipedia, I read that they have been much victim of fatalities on the ground. Electrical Air Canada incident was effectively provoked by the failure of the electrical system pumping of toilets, which was strongly suspected to have been caused by a discarded cigarette in the tank, but without concrete evidence ... The breaker has nevertheless isolated insufficiently the damaged circuits ... Will has a rule of using that prohibits to reset a breaker if he jumps, and in this case the pilot should he made ​​a mistake?

Regarding the DC9-32 of the Valujet, the cause is clearly external. I would killed by my hands this monster Aerotech CEO who was responsible of the death of hundreds of people in the most horrific conditions, almost in a crematorium! ... Nevertheless, the crew lost the use of all instruments of navigation within 12 seconds after the fire in bunker: the case of avionics is she stood at the front of the plane? The analogic instruments are therefore linked to external sensors for the most part, how is it that the electrical circuit of the aircraft was hit and its navigational instruments?!

[thetimesreader84]

Bienvenue!

I think Monsieur is asking 3 questions;

Why did the DC-9 suffer from technical problems, and suffer fatal crashes early in its career (value jet and air Canada)

Why did the Caravelle not have the same success as the DC-9 and 737

I think the last question is why the. DC-9 wasn't more successful in Europe, as it was very successful in America, being produced in 80-110 seat versions

Apologies if these aren't exactly correct, and I'm afraid I have no answers, someone else perhaps?

Any spelling mistakes are tablet induced.

TTR

[joy ride]

The Caravelle was certainly one of the most elegant airliners ever made. Interesting that its nose was shared with the Comet, interesting too that this nose shape has been re-invented on the Dreamliner!

The Caravelle was not often seen in UK, but the BAC 111 was quite successful here, and even sold in USA.

I think that part of the reason for the greater success of the American planes was that their manufacturers had grown extremely rich and powerful in WW2, partly because UK had to buy their products as our bomb-damaged industry was at full capacity. Our "Lend Lease" payments to US also benefitted them hugely.

After WW2 USA started Operation Paperclip, rounding up lots of German scientists, technologists and engineers to add to their technical knowledge, plus under Lend Lease and other technology share requirements USA also got the benefit of much British technology like Radar, Computers, Jet Engines, Aerodynamic information.....and lots more.

With their huge industries and new technical know-how they were able to outsell UK and European manufacturers and establish a huge command of the world's market.

[tonytales]

There is no doubt that having a huge home market for Boeing and Douglas aircraft was an advantage. However, the European airliners of the time, the Bac 1-11, the Caravelle and the Trident all seemed to be a notch too small. The baggage compartments on the Comet and Caravelle were too small for one. The downsizing of the Trident and the reduction of engine size handicapped the BAC 1-11 and the Trident.
The DC-9 was a simple aircraft. Good hydraulic system design with redundancy. The electrical system generally was good but there was crowding of power relays and contactors behind the Captain. I suspect the Valujet fire in the bag hold cooked the electrical feeders that ran under the floor and therefore above the fire. Structurally it was robust with some problems with gear trunnions.
It did suffer from hidden icing on the top surfaces of the inboard wing skins. Chilled fuel in the tanks could freeze precipitation on the ground forming an almost invisible coating of ice.
The DC-9 being typically Douglas, used cables to move things. The only boosted control surface was the rudder which had manual reversion, The ailerons and elevators were flying tab operated. The elevators had a hydraulic down push in case of a deep stall situation.
The slats were operated by cables driven by a drum that was hydraulically operated. These cables had about the highest tension of any cable system I recall. The DC9-20 to 50 series had individual slat drives for each wing, not cross-connected while the little bit of -80 series I saw had one drive for both wings.
The engine installation was good and clean and quite accessible. The thrust reversers were the easiest to maintain of any I saw being the least complicated. They were good enough that Boeing fitted them to the B737's fitted with JT8D engines.
The folding cockpit jumpseat on the DC-9 was something else. I spent a lot of time on it as a Tech Service rep and being 6 ft 4 in tall it was a tight fit and you had to watch where you put your feet.
But I loved the aircraft. All the pilots seemed to like the Diesel 9.

[Yan104]

Hello everyone,

I had an impediment that did not allow me to come earlier on the forum, but I am pleasantly surprised by your answers and I thank you all for your efforts of reading me! ...

Joy Ride it's true that americans have seen their aviation industry boosted by massive sales of fighter planes and planes of troops transport during the Second World War. They will also undoubtedly benefited from the expertise of the UK in terms of navigation tools (radars among others) , engine (with Frank Whittle father's of reactors to which we did not want to give any credibility in the begining ) and aerodynamics , and especially the extraordinary inventiveness and audacity of German engineers, fell into the wrong hands , and fully deserved to be disputed by the two great powers of this time , the U.S.A and the USSR ...

But I also think that in the late 50s, the airlines in the world should have a huge need to replace their propeller airliners , aged on average 20 to 30 years, and I think that at this time, it was Douglas Aircraft Corporation which dominated the market , with the DC- 3 and its various versions until the last model of the family DC7 . Boeing does not seem to me positioned in the field of civil aviation, he has produced some models of aircrafts, but the seating capacity was limited. But I think it was the first that created a pressurized airplane propellers. We have also to note the presence of Lockheed , with its famous Superconstellation who apparently has a substantial autonomy for this time ... Anyway, I think all these planes were mostly intended to serve the lines of medium-haul , and had all the same reliability problems in their engines and Loadout limited passenger capacity . Is this those factors that decided the leaders of airlines around the world to buy civilian jets ?

I think that in the travel habits of americans, planes had always held an important place. For long distances , connecting states or far away areas as the East and West Cost, there is no faster way than flying. The coach also came in 2nd position in the modes of transport. Who can tell me what was the state of competition between the lines transport in the ground and air in the 50's/60's in the United States ? From when passenger traffic really started to densify in the domestic lines at the point that aircrafts of 80 seats became more attractive to airlines?
In contrast in Europe , given the proximity of their countries , and for short distances within the latter, it has always been more interesting to use the trains than planes. Again, from when the air traffic began to be more important than rail traffic, which allowed the purchase of more efficient aircrafts (and necessarily more expensive) of 80 seats(capacity of DC9-10) or more for lines such as Paris/Berlin or Paris/Madrid ?

Tonytales, I forgot the limited capacity of the baggage of the BAC 1-11 and the Caravelle ... But was it really a handicap factor for the carriage of passengers, affecting passenger capacity? Otherwise you confirm my informations on reducing power reactors Bac 111! ...

I note that you worked as technician on the DC9 and you seem to know him quite well, which rather suits my business! ... The flight control cables and their redundancies were they located on the floor of the plane? Was there a gap in the forward hold dedicated to special equipment that operate navigational instruments?
The DC9 was it equipped with leading edge slats attacks? I recently read that the Fokker 100 that does not, is extremely sensitive to phenomena of icing wings, this was the case for the DC9, and if so for the entire series from 10 to 50?
You seem also to explain a phenomenon of icing tanks of kerosene, that could occur at extremely low temperatures, so how we solved this problem? SAS has been a major customer for this type of aircraft, and this phenomenon would been a serious handicap for the DC9-20 specially designed for this company, as in northern Europe during winter temperatures can be negative!. ..

I'll stop here for today, by the hope of instructive answers.

[Yan104]

Aloooo!!...Is there still someone alived here?!!...

[WHBM]

The Caravelle was not always a direct competitor. Around 1960 there was a considerable effort by Sud to come to a joint manufacturing deal with Douglas of the Caravelle in the USA, they even had a plant identified, the old Douglas prop aircraft facility in Santa Monica they had vacated when DC8 production went to Long Beach, and at least one Caravelle demonstrator was painted up with Douglas titles and toured the US airlines. There was a bad taste left in Sud's mouth when, after all this expenditure and technology transfer, Douglas said "thanks, now we'll do our own".

The reason behind the Boeing/Douglas dominance can be seen in the actual orders placed and jets delivered in the 1960s; more than 50% of the total world jet market at that time was sold in the USA. European airlines ordered 3 or 5 707s at a time, US carriers like American or TWA took 30 or 50 in the same time. A bit of this market was taken by the European manufacturers but mostly it went to the home companies. For example, the only sale the Caravelle made in the USA, to United Airlines, which was done with Douglas's backing, was only concluded when Douglas agreed to take an equal number of United DC7s in part exchange.

[tonytales]

Regarding the baggage capacity of the Caravelle, we worked Varig's (first with jets to South America) up at KIDL (KJFK) and they had to have a main deck baggage compartment which I believe the Comet also had. That would certainly cut into the space for passengers.
There was indeed an E and E compartment forward of the forward baggage. You could access it through a belly hatch but not from the baggage hold. The forward air stairs actually retracted into this compartment when retracted. By the way, they were of excellent design compared to others I saw and worked.
The mechanical control cables were routed under the floor as were the heavy generator feeder cables and wiring looms.
The APU was in a compartment aft and was relatively easy to change. The pneumatic system and the air conditioning system were aft of the rear pressure bulkhead in the tail compartment and quite accessible.
The rear pressure bulkhead was a source of corrosion and structural problems not helped by lavatories against it. This is not uncommon in many aircraft types.
The composite tail cone was jettisonable for emergency egress use. Depending on whether the aircraft had rear airstairs or not, you either pulled a plug type hatch or opened the aft bulkhead door and proceeded along a catwalk in the rear compartment. The tailcone could be released from inside or out and a small slide then was used for exit.
The external emergency release handle looked very much like the rear airstair operating handle. In one week at KEWR the caterer popped three tailcones on us (EAL). It was not appreciated as the fall would damage them.
I often wondered if Douglas had sized the fuselage to that of the DC-8 as Boeing did the B737 to the B707, if Douglas would have survived.

[Yan104]

Hello Tonytales,

I allowed myself to send you a PM to ask you more techniques questions! ... And I hope that our discussions will be even more successful! ... I thank you very much for your answers! ...


See you soon

[DaveReidUK]

The composite tail cone was jettisonable for emergency egress use. Depending on whether the aircraft had rear airstairs or not, you either pulled a plug type hatch or opened the aft bulkhead door and proceeded along a catwalk in the rear compartment. The tailcone could be released from inside or out and a small slide then was used for exit.

Not forgetting the other feature of the Caravelle's tailcone:



I remember watching it being used on many occasions when they flew rugby charters into Edinburgh's 1800m runway.

[WHBM]

I was indeed going to ask Tonytales about his early experiences with the Varig Caravelle IIIs, one of the features of which was the braking parachute. maybe it wasn't used on JFK's long runways. They were a real nuisance, especially as they were dropped once off the runway, where they might blow about and hold up further movements until they were captured by the base engineer in their van.

When United was getting serious about the Caravelle there were two details the FAA just would not accept. One was the braking parachute in mainstream US airports. The Caravelle with Rolls-Royce Avon engines initially came as the Caravelle III, and then VI-N, and Rolls did a re-engineer of the Avon to include thrust reversers (instead of the parachute), and this was the difference with the VI-R (for reversers) version, which is the one United bought. The other unacceptable feature was the III and VI-N had passenger supplementary oxygen only available as (a limited number of) hand-held units taken round by the cabin crew if required in a depressurisation; the aircraft relied on a lower maximum altitude and the crew performing an emergency descent if pressure failed (an interesting challenge for the cabin crew to be going round asking if you could breathe or not while the nose was down like this - wonder how they trained for this). The FAA absolutely said NO to this, and Sud had to come up with a "proper" drop-down oxygen system on the United and subsequent aircraft. But I wonder how those early Varig aircraft, operating from New York through Miami down to Brazil, were handled in US airspace for this eventuality.

I often wondered if Douglas had sized the fuselage to that of the DC-8 as Boeing did the B737 to the B707, if Douglas would have survived.

The limiting factor in the early short haul jet days was a combination of insufficient engine thrust and handling in engine-out conditions on a twin. This is why the early twin jets, before the 737, were all narrower (5-across) fuselages and rear engines nearer the aircraft centreline. The 737 depended on more powerful versions of the JT8D being finally available, a bigger rudder, and other aspects to make them capable with an engine out. Remember the DC9 was initially designed around earlier, less powerful JT8Ds. Those of you with an aeronautical engineering background can probably explain the details better than me.

[blind pew]

Flew the 32,33f,34,51 and 80.
Wonderful aircraft.there was a problem occasionally with clear ice on the top surface of the wing...generally after a long cruise with lots of fuel and a short turn around in humid conditions when clear ice would form on the top of the tanks.
Very difficult to see and our company painted black lines to aid mark one eyeball detection.
We had a fire in the overhead panel on a 51..emergency battery switch...but some very good work got it out and on the ground within 15 mins.
Pilots aircraft and great fun to fly.
Fokker 100 was a heap IMHO...never had problems with ice to my knowledge...but unsuited to European major airline and backward avionics as well as poor hold volume and low cruise speed due to thick wing. Then cockpit very noisy due to air con packs which also iced up and in or out airbrakes.
Very easy to fly

[tonytales]

The initial DC9 model, the -10 series had JT8D-1 @ 14,000 lb thrust engines which could be operated at -5 ratings or 12,000 lbs thrust for increased life. The B737-100 and many -200 had essentially the same engine although I don't think they offered the derate so I don't know why the DC-9 couldn't have had a similar width cabin.
The -10 series had a hard wing with no slats. All subsequent DC9/MD80 models had L/E slats.
The hard wing models were especially sensitive to wing contamination. We did a "C" Check on a customer's DC9-14 and he requested at the last minute we polish the wing leading edges. My cleaners only got the left wing L/E done before a post check test hop. I watched the T/O, a full power one and being empty, he pulled it up pretty sharply after liftoff. The right wing dropped very suddenly and he was at about 45 degrees right bank. Nose went down and he recovered but came right back. It was difference between polished left L/E and unpolished right L/E. He got a partial stall on the dirty wing. Scared hell out of me and I was on the ground.
Re the Caravelles drag chute, never were used at New York. Don't remember the pax emergency oxygen system, it is now 50 years. The Suds didn't last long on that route fir which they were never designed for. They had very limited seating with huge legroom between rows as they were really stretching the range of the aircraft. Varig replaced them on the route with Conway powered B707-400 models.
I did get a rid in a Varig Caravelle though. They wanted to go pilot train but needed aft ballast for CG control. Instead of sandbags, they invited us and other airline workers to come along. My wife was picking me up at work that day and I talked her into going up for a "Jet Demonstration Ride", a real novelty at the time. Up we went and out to the East End of Long Island did approaches and go-arounds. No touch downs to save tires. When the cockpit door came open on one of the steep climbs she saw they had pillows stuffed over the windshields and almost fainted. Smooth, quiet and oh my, those big windows.

[Yan104]

Dear Tonytale,

I honestly appreciate your technical descriptions of DC9 , that I was anable to find anywhere else on the Web ! ... I printed technical and historical records of this beautiful family of aircrafts , but none describes me as precisely each parts of this plane. It seems to me that the DC8 has a much broader fuselage than the DC9 , as it was designed for transatlantic flights , and the tradition among manufacturers is that the big carriers haved 3 lanes . I have had a sketch of the configuration of the passengers cabin of the DC9 -10 , and I saw that there were five rows of seats in front, three on the right side, and two on the left , a little as regional aircrafts of today ERJ 170/190 and ATR72 ! ... I do not know if this configuration has been stored on the MD80 . Have you had the opportunity to do maintenance on them? Have you discovered the other aircrafts in the family, such as 20 and 30 series ?
I do not know if you've noticed it , if necessary look at a close-up photo of the nose of the DC8 , it has two slots on each side of his nose, which is not found on the DC9 . What can it fit ? Is it hatches for the weather radar ? If so, where do we have then moved the sensors on the DC9 ?


I have a little trouble understanding the technical terms translated from English to French ! ... What is the E and E compartment ? I think I have guessed that this is about the avionics of the aircraft. So this compartment was located just after the forward baggage compartment , and just before the door of the front landing gear ( also called in French nose wheel ) , is that right? I guess these equipments were totally different from those of Glass Cockpits with digital units and circuits : what it was exactly like devices, this was hydraulic or pneumatic sensors, probes or other ?

I'm terribly annoyed that the redundancy of the flight control cables were installed in the same location as the main controls , on the floor . And more to the main electrical circuits ... So we can better understand why the loss of all control circuits, electrical as mechanical was devastating for the DC9- 32 of the Valujet... I even believe that the control cables of reactors power also passed through the floor because those of No.1 engine was disrupted , Kandy(the girl captain) was no longer able to modulate his power ... Do you think engineers of MDD could organize the distribution of cable redundancy otherwise, were there other possibilities?

It did not seem to me that the DC9 was equipped with an APU ! ... How is it that there was no exhaust nozzle at the tail? How did it work compared to other gas turbines on other planes?
So if I understand your explanation , air conditioning and pressurization systems were neighbors of the APU ? Is valve pressurization was stood back and forward fuselage ?

I know that the wet parts of an aircraft such as toilets are sources of internal corrosion. But why the pressure bulkhead , supposed to be waterproof, producing it from moisture ? ! ... Was it after each cycle of depressurization in the descent of the plane ? Are there already had technical problems here ? What was the cycle of visits of this very sensitive part of the aircraft, and which elements were to replace frequently?

[Yan104]

Re hello,

I come to answer courtesy to other participants whose responses and testimonials are interesting .

WHBM I did not doubt a moment that the aircraft orders in the United States , mostly for domestic flights , had been 10 times greater than those of European companies ! ... And then we must consider the context output of war, where with the U.S. aid, European countries began in the 1950s and 60’s to restore their economy and had nothing else to do more urgent and vital that renew their fleets companies .. . Should also say that the majority of airline fleets in the world in this period included aircrafts built in the 1920-1930' , they had limited radius of action and weak engines , and thus gradually the leaders of European and American airlines have decided to move to civilian jets ... This created a windfall for medium-haul jets ... It should be noted however that is trough the long-haul sector , with the B707 and DC8 in the 50s , that are introduced civil jets ... It’s a little bit strange, because the logic would dictate that starts with the smallest to reach the largest don’t you think so ! ! ...

Blind Pew , your experience as a pilot on DC9 seems interesting to me : I had no idea that there had been a sub- series 34 of series 30 , I thought there were only 2 sub- series 31 and 32 ... But all these names are they not related to changes in the structural mass of the DC9 -30 and variants of JT8D engine developed specifically for them? If so , what changes are made to the fuselages to strengthen their empty weight ?
Speaking of engines , I doubt that the JT8D of DC9’s have had the same dimensions as those equipped the 737 100 and 200 , the engines seems shorter in the DC9 . You will kindly correct me Tonytale if I’m wrong ! ...
Is the DC9- 51 does not foreshadowed in his characteristics MD80 series ? Did we started to introduce informatics technology in the cockpit ? Blind Pew , what was the fire in the overhead , why switch battery was messed up ? Was it on the ground or in flight ? How the problem was solved ?

Finally, concerning the icing , I confirm to have read the story of a serious incident occured in a Fokker 100 of Air France in 1999, that the lack of nose leading edges caused a sudden stall dice the plane he had left the track, and that it therefore has a special sensitivity that has been underestimated by the crew ... And besides, Tonytale confirms this phenomenon on the DC9 -10 that was not equipped with spouts leading edges ... I do not understand how these devices reduce the risk of stall condition frost ( of course without canceling completely ) ...

[WHBM]

Douglas seemed to have a tradition of advancing the aerodynamic configuration of their wings as they went along, almost as if their design office didn't have the best tools for development. Did I read once that Boeing's directors in the 1950s paid out for their own full wind tunnel but Donald Douglas didn't think it was necessary and just bought minimal time elsewhere ?

The DC8 did exactly the same advancement, the original DC8-11 had no leading edge devices and was re-engineered as early as the DC8-12 using slots, which all the original ones were converted to. They also found the original wingtips were high drag, and these were redone. Later on they found that it was more efficient to cruise with 1 degree of flaps set. These aspects should really have come out in the initial design analysis.

It is not correct to say that any airliners from the 1920s-30s were in service after 1945, the whole lot had been replaced by immediate post-war designs, or wartime military ones converted. Even the postwar DC3 fleets were generally from the last couple of years production 1944-45. Then there were multiple rollovers of fleets during the 1950s, few of the DC4s or L049s from 1945-50 were still with first line operators by 1960. The later piston aircraft of the late 1950s, the Lockheed L-1649Starliner or the DC7, had especially short lives before being scrapped - American Airlines scrapped pretty much their entire large DC7 fleet after no more than about 5 years service as the jets came along - American didn't want them any more, nor did anybody else.

[tonytales]

When I was a maintenance instructor I had some old projector transparancies of the original DC-8 with the squared off wingtips.
The DC-8 wing did undergo a major change and many were retrofitted with new leading edges resulting in a sharper profile. They also did Project 61 reworking the hydraulic system and adding the flap lockout cylinders to provide system redundancy. The -62 and -63 models of course had the wingtip extensions. which really improved things.
Not having a wind tunnel was shortsighted. Our senior VP had worked at Douglas and told us how the commercial operation had to assist the design group on the C-133 due to high drag of wing to fuselage fillets.