Transpac787
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727 Design Flaws?

Thu Sep 06, 2007 7:38 am

Hey all,

Fairly self-explanatory title. Does anyone know of any significant / major design flaws of the 727?? I don't mean more minor teething issues, but more things along the lines of issues experienced by the DC10.

Thanks in advance for all responses!!
 
prebennorholm
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RE: 727 Design Flaws?

Thu Sep 06, 2007 9:31 am

Aeh, not really. Well, maybe one design flaw:

The fuselage width is based on the 707 barrel. Originally Boeing proposed it (the 707) for a perfect 5 abreast seating. But some customers wanted a perfect five-and-a-half seating. And Boeing obeyed and widened it a few inches. How stupid!

Even more stupid, those same companies plus many more cramped in 6 abreast seating in the space available.

Apart from that, great plane. Except for the today totally outdated, fuel guzzling and noisy engines.
Always keep your number of landings equal to your number of take-offs
 
L-188
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RE: 727 Design Flaws?

Thu Sep 06, 2007 10:22 am

Quoting Prebennorholm (Reply 1):
The fuselage width is based on the 707 barrel. Originally Boeing proposed it (the 707) for a perfect 5 abreast seating. But some customers wanted a perfect five-and-a-half seating. And Boeing obeyed and widened it a few inches. How stupid

I would hardly call giving the customer what they want stupid.

I think there where some spray issues off the nosewheel that was solved with the use of chined tires.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
bok269
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RE: 727 Design Flaws?

Thu Sep 06, 2007 10:33 am

Quoting Prebennorholm (Reply 1):

Why is it stupid? Because two pax in each row get the middle? At the end of the day its more important to the airlines to make money than whether someone gets the middle. Do people mind the middle? Sure. Do they complain? No. Its not a big deal. Its proven to pay off for Boeing. The same barrel became the 737, the best selling airliner in history. Not to mention 5 abreast aircraft make for undesirable freighters.
"Reality is wrong, dreams are for real." -Tupac
 
Viscount724
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RE: 727 Design Flaws?

Thu Sep 06, 2007 12:39 pm

Quoting Bok269 (Reply 3):
Quoting Prebennorholm (Reply 1):

Why is it stupid? Because two pax in each row get the middle? At the end of the day its more important to the airlines to make money than whether someone gets the middle. Do people mind the middle? Sure. Do they complain? No. Its not a big deal. Its proven to pay off for Boeing. The same barrel became the 737, the best selling airliner in history. Not to mention 5 abreast aircraft make for undesirable freighters.

Totally agree. Had the 707 (and DC-8 which is one inch narrower than the 707) only been able to accomodate 5-abreast economy class seating, passenger fares would have had to be significantly higher to generate the same revenue to cover operating costs but from 17% fewer passengers. That would have meant that fewer people would have been able to afford to fly and the airline and travel industries would have grown at a much slower pace.

Don't forget that the Convair 880/990 were commercial failures in large part because they were designed to accommodate only 5-abreast Y-class seating, and thus were uneconomic since carriers operating them had to charge the same fares as their far more numerous competitors flying 707s and DC-8s.
 
57AZ
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RE: 727 Design Flaws?

Thu Sep 06, 2007 12:49 pm

The design change was the best thing that Boeing could do for sales of the early 700 series jets. The reason that they made the change was that Douglas waited until Boeing had manufactured their tooling and then widened the DC-8 in an attempt to steal potential customers from Boeing. Boeing realized that while calling Douglas's bluff would be financially expensive, it would allow them to retain their advantage over Douglas and pay for itself in the end. While this prevented the production of both civil and military aircraft on the same production line, it paid off. Boeing had some guts to basically stop the 707 program and redesign the fuselage right as it was about to go into production, but it paid off handsomely.

The water spray was indeed an issue which was addressed with the chined tires. As for significant design flaws, the only major aerodynamic flaw it had was the possibility of entering a deep stall. That is a standard issue with the T tailed, swept wing aircraft but I do not believe that any 727 was lost to a deep stall.
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KELPkid
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RE: 727 Design Flaws?

Thu Sep 06, 2007 3:14 pm

One design flaw of the 3-holer was it's propensity for the #3 engine to injest blue ice:


View Large View Medium
Click here for bigger photo!

Photo © Brian Harrison



Fortunately, no aircraft were ever lost over this, only a few #3 engines...  Wink
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Faro
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RE: 727 Design Flaws?

Thu Sep 06, 2007 3:30 pm

Quoting Transpac787 (Thread starter):
I don't mean more minor teething issues, but more things along the lines of issues experienced by the DC10.

What design flaws for the DC10?

There were cargo door latching mechanism issues after an incident with a American Airlines aircraft in 1972, AA flight 96 near Detroit, which sadly was not resolved in the case of Turkish Airlines' Ermenonville aricraft. But that was a regulatory/communications failing, not an aircraft design issue. The American Airlines flight out of ORD which lost an engine in 1979 was due to an AA engine change procedure which was not approved by the manufacturer. The DC10 was lynched by the press at the time, but it was not strictu senso a design flaw which caused the accident.
The chalice not my son
 
411A
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RE: 727 Design Flaws?

Thu Sep 06, 2007 3:59 pm

Quoting 57AZ (Reply 5):
but I do not believe that any 727 was lost to a deep stall.

Not quite correct.
Search the NTSB database for a B727 (NW, as I recall) ferry flight, where the pitot heat was not switched on prior to departure.
The accident was near White Plains, NY.
 
MD11Engineer
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RE: 727 Design Flaws?

Thu Sep 06, 2007 5:11 pm

I have worked on 727s and generally liked them. The worst design flaw IMO were the brakes:
Heavy, big and a pain in the arse to change with the ten mount bolts, which had to be lined up and torqued seperately to get them attached. Also, for #1 and #4 main wheel, there is very little space under the strut door (even if unlocked and folded up) for a brake dolley, so we had to lift the brakes by hand. Since there is only space for two people, it was a truly backbreaking job.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
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DL_Mech
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RE: 727 Design Flaws?

Thu Sep 06, 2007 7:45 pm

I can't think of any major flaws, just minor ones......

E&E door always falls off of its tracks, wheel well/wing wiring frequently damaged by skydrol, autopilot "porpoising" problems (usually elevator position sensors or worn stab bushings), the aforementioned brakes were a b!tch to change and the constant drip of engine oil on the heads of people using the airstair. All in all, it was a pretty good airplane.
This plane is built to withstand anything... except a bad pilot.
 
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Starlionblue
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RE: 727 Design Flaws?

Thu Sep 06, 2007 8:02 pm

Turbulence in the S-duct led to center engine surges at rotation every so often.
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fr8mech
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RE: 727 Design Flaws?

Thu Sep 06, 2007 8:41 pm

You could not open the forward lav door with the cockpit door fully open.
When seconds count...the police are minutes away.
 
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Jetlagged
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RE: 727 Design Flaws?

Thu Sep 06, 2007 9:51 pm

Quoting Faro (Reply 7):
What design flaws for the DC10?

How about routing all the hydraulic lines in close proximity to each other in the tail near the engine. One uncontained engine failure took out all the hydraulics in the Sioux City accident. Hydraulic fuses might have prevented total loss of fluid. Not venting the cabin floor adequately. The THY DC-10 might have survived had the floor not collapsed causing a failure of the flight control cables.

Obviously the DC-10 is not alone in such defects, especially close proximity of hydraulic lines, but it has probably had them highlighted more than most. All hydraulic lines have to be in close proximity at the tail, but having an engine in the tail as well makes this a major weakness.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
NKP S2
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RE: 727 Design Flaws?

Thu Sep 06, 2007 9:54 pm

Quoting MD11Engineer (Reply 9):
I have worked on 727s and generally liked them. The worst design flaw IMO were the brakes:
Heavy, big and a pain in the arse to change with the ten mount bolts, which had to be lined up and torqued seperately to get them attached. Also, for #1 and #4 main wheel, there is very little space under the strut door (even if unlocked and folded up) for a brake dolley, so we had to lift the brakes by hand. Since there is only space for two people, it was a truly backbreaking job.

They sure were as heavy as hell, and I've bashed my head on the "flying" gear door scores of times while changing #'s 1 & 4 brakes/tires. One thing though: I worked on some ex-Alitalia 727-200's and their brakes only required 3 bolts, the other 8 ( 11 total IIRC ) were converted to anti-rotation dowels/studs.
 
boeingfixer
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RE: 727 Design Flaws?

Thu Sep 06, 2007 11:58 pm

Quoting Jetlagged (Reply 13):
Quoting Faro (Reply 7):
What design flaws for the DC10?



Quoting Jetlagged (Reply 13):
How about routing all the hydraulic lines in close proximity to each other in the tail near the engine. One uncontained engine failure took out all the hydraulics in the Sioux City accident. Hydraulic fuses might have prevented total loss of fluid. Not venting the cabin floor adequately. The THY DC-10 might have survived had the floor not collapsed causing a failure of the flight control cables.

For the Sioux City accident you are reversing the events of failure. The root cause of the accident was a metallurgical flaw in the #2 engine fan disk. This metallurgical flaw led to a failure of the disk which took out the #1 and #3 hydraulic systems with fan debris and damaged the #2 hydraulic system from the physical shock of the disk failure. The damaged lines were located in the R/H horizontal stab. and were not located in the tail near the engine. BTW, the DC-10 has had changes made to the hydraulics to minimize the effect of such a rare failure of the #2 engine fan disk.

United Airlines Flight 232 Accident report: http://amelia.db.erau.edu/reports/ntsb/aar/AAR90-06.pdf

Cheers,

John
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Jetlagged
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RE: 727 Design Flaws?

Fri Sep 07, 2007 12:28 am

Quoting BoeingFixer (Reply 15):
For the Sioux City accident you are reversing the events of failure.

How have I reversed the sequence of events? My comment is more condensed, but the sequence is the same.

Quoting Jetlagged (Reply 13):
One uncontained engine failure took out all the hydraulics in the Sioux City accident.



Quoting BoeingFixer (Reply 15):
The root cause of the accident was a metallurgical flaw in the #2 engine fan disk. This metallurgical flaw led to a failure of the disk which took out the #1 and #3 hydraulic systems with fan debris and damaged the #2 hydraulic system from the physical shock of the disk failure. The damaged lines were located in the R/H horizontal stab. and were not located in the tail near the engine.

OK, you took my reference to tail to mean the fin. The horizontal stabiliser is still in the tail section of the aircraft, and clearly close enough to the engine to be affected by an uncontained failure. Semantics of the word "tail" aside, the proximity of all three hydraulic lines to an engine in the tail section is a design flaw.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
N231YE
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RE: 727 Design Flaws?

Fri Sep 07, 2007 12:53 am

Surprisingly, no-one mentioned the fact that the ventral airstair could be opened in flight.  wink 

Though not a design flaw, we all know of the infamous case of the aircraft hijacking that prompted Boeing to design a special vane for its namesake to prevent the stair from being opened in flight.
 
Fly2HMO
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RE: 727 Design Flaws?

Fri Sep 07, 2007 1:19 am

I think a major design flaw was putting 3 engines that made more noise than thrust.  Wink
 
CaptOveur
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RE: 727 Design Flaws?

Fri Sep 07, 2007 1:32 am

Quoting N231YE (Reply 17):
Surprisingly, no-one mentioned the fact that the ventral airstair could be opened in flight.

They eventually fixed that.
Things were better when it was two guys in a dorm room.
 
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Stitch
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RE: 727 Design Flaws?

Fri Sep 07, 2007 1:41 am

Quoting Faro (Reply 7):
There were cargo door latching mechanism issues after an incident with a American Airlines aircraft in 1972, AA flight 96 near Detroit, which sadly was not resolved in the case of Turkish Airlines' Ermenonville aricraft. But that was a regulatory/communications failing, not an aircraft design issue.

With respect, I view the cargo door latching issue as an aircraft design issue, along with the fact that explosive decompression of the cargo bay could result in the partial collapse of the passenger deck which severed all the hydraulic control lines that ran through that deck, as happened with the Turkish Airline's plane.

Mind you, I never feared for my life when aboard a DC-10, just as I didn't fear for my life aboard a 737 Classic after the UA, US, and Panama incidents, nor do I fear for it when on MD-8x planes after the loss of AS261.
 
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Faro
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RE: 727 Design Flaws?

Fri Sep 07, 2007 2:03 am

Quoting Stitch (Reply 20):
Quoting Faro (Reply 7):
There were cargo door latching mechanism issues after an incident with a American Airlines aircraft in 1972, AA flight 96 near Detroit, which sadly was not resolved in the case of Turkish Airlines' Ermenonville aricraft. But that was a regulatory/communications failing, not an aircraft design issue.

With respect, I view the cargo door latching issue as an aircraft design issue, along with the fact that explosive decompression of the cargo bay could result in the partial collapse of the passenger deck which severed all the hydraulic control lines that ran through that deck, as happened with the Turkish Airline's plane.

I fully agree, I expressed myself wrongly: the regulatory/communications failing referred to the fact that the Ermenonville aircraft was sadly not suitably modified to correct the cargo door latching problem in time. The problem with the latching mechanism itself was clearly a design flaw.
The chalice not my son
 
N231YE
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RE: 727 Design Flaws?

Fri Sep 07, 2007 3:26 am

Quoting CaptOveur (Reply 19):
They eventually fixed that.

I know...I said it in my original post:

Quoting N231YE (Reply 17):
Though not a design flaw, we all know of the infamous case of the aircraft hijacking that prompted Boeing to design a special vane for its namesake to prevent the stair from being opened in flight.
 
prebennorholm
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RE: 727 Design Flaws?

Fri Sep 07, 2007 4:39 am

Quoting L-188 (Reply 2):
Quoting Prebennorholm (Reply 1):
The fuselage width is based on the 707 barrel. Originally Boeing proposed it (the 707) for a perfect 5 abreast seating. But some customers wanted a perfect five-and-a-half seating. And Boeing obeyed and widened it a few inches. How stupid



Quoting Bok269 (Reply 3):
Why is it stupid? Because two pax in each row get the middle?

What I wanted to tell was that Boeing proposed a perfect 5 abreast plane, the 707. The airlines wanted 6 abreast. Boeing should have added 20 inches instead to make it a full grown 6 abreast plane. That way modern time 737s wouldn't have been the most cramped 6 abreast plane in the world today. (It wouldn't be what I called "a perfect five-and-a-half abreast plane"

Ever flown on a Tu-154 or IL-62?

First thing to discover when entering the cabin: Have I entered a time machine and gone a hundred years back in time?

Second thing: Hey, something is different, no need to rub elbows with fellow passengers.
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CosmicCruiser
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RE: 727 Design Flaws?

Fri Sep 07, 2007 6:01 am

Don't get me wrong cuz I loved flying the 727 but it is the only jet I've flown that practicing "dutch roll" recovery in the sim was an annual event.
 
prebennorholm
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RE: 727 Design Flaws?

Fri Sep 07, 2007 8:00 am

Quoting CosmicCruiser (Reply 24):
...it is the only jet I've flown that practicing "dutch roll" recovery in the sim was an annual event.

It is probably also the only tri-jet you have flown with all three engines in the back. That means a lot of mass long distance fore and aft of the CG. Add to that a relatively low fin (saves a lot of weight for structure to support the horizontal tail) and a quite generously swept back wing.

They are all properties which tend to give you quite a handful of flying machine in case of an inop yaw damper.

Other types of similarly configured planes (Tu-154 and VC-10) seem to have proportionally higher fin, less swept wing, or in the case of Tu-154 no dihedral, or even anhedral wing. Which are all properties which (everything else equal) tend to improve dutch roll properties.

But then those same 154/VC-10 properties had other slightly negative effects, mainly on performance figures. Less sweep = less speed, higher fin = higher empty weight = less payload/range. The 154 needed a longer and heavier landing gear not to polish wingtips doing sideslip landings in crosswind. Etc.

All planes are compromises, compromises and even more compromises. You can't have it all.

All planes have their good and not so good properties. And the 727 was not the best friend of dutch roll. But it was certainly - for its time - an excellent performer - speed-, payload-, range-wise.

Having all engines on the tail was also a compromise which allowed the wing more freely to be optimized for combining low cruise drag at high speed and quite good runway performance without the very most complicated (heavy and expensive) high lift devices. Well, they were quite innovative for its time, but sure those Krueger leading edge flaps saved both structure weight and production cost compared to for instance the DC-9-30 and onwards.

Those 727 properties are all properties which tend to move airline bottom lines in direction of red to black. And BTW, why were you a 727 driver? I'm sure that the monthly paycheque had a great infuence.

And since you are a good pilot, and you were well trained on the 727 peculiarities, then the 727 was in good hands with you in the front office. Did I say something wrong? I'm sure I didn't.
Always keep your number of landings equal to your number of take-offs
 
PGNCS
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RE: 727 Design Flaws?

Fri Sep 07, 2007 9:13 am

It made pilots go deaf.
 
KELPkid
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RE: 727 Design Flaws?

Fri Sep 07, 2007 9:48 am

Quoting PGNCS (Reply 26):
It made pilots go deaf.

What, the jet that Eastern Airlines dubbed the "Whisper Jet" because it was so much quieter inside than previous planes* (* provided you weren't in the tail by the engines)  Smile
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CosmicCruiser
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RE: 727 Design Flaws?

Fri Sep 07, 2007 10:59 am

Quoting Prebennorholm (Reply 25):
Did I say something wrong? I'm sure I didn't.

No not at all, I thought the 727 was the most "fun" jet I've flown. It could be man handled, and wrestled around and never give you a moments worry,

Quoting PGNCS (Reply 26):
It made pilots go deaf.

Now that's a true statement; it was loud up front and especially below 30,000'.

I also just remembered the "diving board" effect on the -200s. In turbulence the cockpit would just bounce up and down in the lightest stuff.
 
CosmicCruiser
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RE: 727 Design Flaws?

Fri Sep 07, 2007 11:02 am

Quoting Prebennorholm (Reply 25):
Did I say something wrong? I'm sure I didn't.

No not at all, I thought the 727 was the most "fun" jet I've flown. It could be man handled, and wrestled around and never give you a moments worry,

Quoting PGNCS (Reply 26):
It made pilots go deaf.

Now that's a true statement; it was loud up front and especially below 30,000'.

I also just remembered the "diving board" effect on the -200s. In turbulence the cockpit would just bounce up and down in the lightest stuff.
 
Viscount724
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RE: 727 Design Flaws?

Fri Sep 07, 2007 11:57 am

Quoting 411A (Reply 8):
Quoting 57AZ (Reply 5):
but I do not believe that any 727 was lost to a deep stall.

Not quite correct.
Search the NTSB database for a B727 (NW, as I recall) ferry flight, where the pitot heat was not switched on prior to departure.
The accident was near White Plains, NY.

Yes, this one:
http://aviation-safety.net/database/record.php?id=19741201-1
 
OldAeroGuy
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RE: 727 Design Flaws?

Fri Sep 07, 2007 2:10 pm

Quoting Faro (Reply 7):
What design flaws for the DC10?

What about not fitting mechanical slat locks to prevent slat retraction when hydraulic fluid is lost? This was a major factor in the AA DC-10 accident in Chicago.

Quoting 411A (Reply 8):
Not quite correct.
Search the NTSB database for a B727 (NW, as I recall) ferry flight, where the pitot heat was not switched on prior to departure.
The accident was near White Plains, NY.

The correction for this on the 757 & 767 was to remove pitot heat from direct pilot control. Pitot heat is on whenever the engines are operating.

Unfortunately a 757 was lost in similar circumstances to the White Plains 727 when it took off with the pitots plugged by wasp nests.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
TrijetsRMissed
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RE: 727 Design Flaws?

Fri Sep 07, 2007 3:38 pm

I don't know of any design flaws regarding the 727. It's always been known as a dependable plane, aside from some nuisances mentioned by pilots and mechanics.

I think we need to remember a system malfunction is not always the result of a design flaw. IMO, a design flaw involves a part/device on the plane that needs changing immediately to prevent itself from causing future accidents. The rudder on the 737 and cargo door on the DC-10 are great examples. The DC-10's hydraulic system and MD-80's jackscrew are not. Rather, contributing factors in a mechanical failure that brought down the plane.

Quoting OldAeroGuy (Reply 31):
Unfortunately a 757 was lost in similar circumstances to the White Plains 727 when it took off with the pitots plugged by wasp nests.

I think it was duct tape that the grounds crew forgot to remove prior to departure, unless I am thinking of a different accident.
There's nothing quite like a trijet.
 
OldAeroGuy
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RE: 727 Design Flaws?

Fri Sep 07, 2007 11:46 pm

Quoting TrijetsRMissed (Reply 32):
I think it was duct tape that the grounds crew forgot to remove prior to departure, unless I am thinking of a different accident.

There have been two 757 crashes due to unreliable airspeed. One involved plugged pitots (the one I was describing) and one where the statics were taped over (the one you're thinking about).

Quoting TrijetsRMissed (Reply 32):
I think we need to remember a system malfunction is not always the result of a design flaw. IMO, a design flaw involves a part/device on the plane that needs changing immediately to prevent itself from causing future accidents. The rudder on the 737 and cargo door on the DC-10 are great examples. The DC-10's hydraulic system and MD-80's jackscrew are not.

However an AD was issued that required revisions to the DC-10 hydraulic/slat systems. This is indicative of a design flaw.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
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SEPilot
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RE: 727 Design Flaws?

Sat Sep 08, 2007 6:09 am

Quoting Faro (Reply 7):
What design flaws for the DC10?

The DC-10 design was completed after the M-D merger, and McDonnell personnel were calling the shots. They had only designed military planes before, where you designed to specification. Boeing, Douglas, and Lockheed had all learned to design planes to be as safe as they knew how, regardless of specifications, and hence went to great lengths to achieve redundancy in systems and to minimize the effects of any failures. The result was that numerous short cuts were taken in the design of the DC-10 that the other manufacturers would not have made (such as the routing of the hydraulic lines along the leading edge of the wing and the lack of check valves in the hydraulic systems.) These were small, relatively insignificant details that came back to bite, and gave the DC-10 the reputation of being not as well built as the other airliners.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
CanadianNorth
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RE: 727 Design Flaws?

Sat Sep 08, 2007 10:55 am

Quoting Fr8Mech (Reply 12):
You could not open the forward lav door with the cockpit door fully open.

Our 737s are the same way - theres a door to the fwd lav and a door to the flight deck, but only one at a time can be opened.


CanadianNorth
What could possibly go wrong?
 
ex52tech
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RE: 727 Design Flaws?

Sat Sep 08, 2007 1:01 pm

Quoting MD11Engineer (Reply 9):
I have worked on 727s and generally liked them. The worst design flaw IMO were the brakes:
Heavy, big and a pain in the arse to change with the ten mount bolts, which had to be lined up and torqued seperately to get them attached. Also, for #1 and #4 main wheel, there is very little space under the strut door (even if unlocked and folded up) for a brake dolley, so we had to lift the brakes by hand. Since there is only space for two people, it was a truly backbreaking job.

I was thinking about the brakes also, and the 25/32 12 point socket that you needed to torque the nuts on the brake.......those are hard to find. I did see some with the three bolts, and the anti-rotation pins in the other holes, we had started to modify some of the fleet to this design, but then they stopped and went back to the bolts in all the holes.....not sure why. Management probably thought that it made the job way to easy, and you just can't have that. The -100's with nose brakes were not fun to work with either.
The brake control valves in the wheel wells always leaked, and you usually found out when you looked up after you walked into the wheel well.

The issue with the flying door on the outboard tires was compounded on the 727s with the big flotation tires. Anybody remember changing an inboard tire when it was raining......the water ran right down the back of your neck, and it seemed like about a half a gallon a second.

How about the APU. Change the APU generator, it can be done without removing the APU, but I found it to take about the same amount of time to just pull the whole thing out and then change the generator.

The early pneumatic outflow valves caused some write ups, they were found in the -100s, they were slow and hung up, and caused the cabin to altitude to porpoise when they weren't operating properly. Sometimes it was cigarette tar causing them to stick.

Oh....and if you had to accomplish an overnight check on one, you could find yourself changing an oxygen bottle about 90% of the time.

I had a forward cabin door write up once, and when I took the cover off, I found the mechanism inside of the door appeared to have more moving parts than a helicopter transmission. I found someone who knew how to rig one to help me, it felt like we were cracking a safe.

Removing a CSD without draining the wet spline was one of those things you only did once, but hey that was on any JT8.

All in all I really liked the 727, it is a relatively trouble free aircraft when it's out in service, it is easy to work on, and it is tough, like a flying tank.
"Saddest thing I ever witnessed....an airplane being scrapped"
 
MD11Engineer
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RE: 727 Design Flaws?

Sat Sep 08, 2007 4:01 pm

Quoting Ex52tech (Reply 36):
I had a forward cabin door write up once, and when I took the cover off, I found the mechanism inside of the door appeared to have more moving parts than a helicopter transmission. I found someone who knew how to rig one to help me, it felt like we were cracking a safe.

The same door design has been used from the 707 onwards up to the 737NG. Once you have figured out how the mechanism works, T/S and rigging are fairly easy.

Jan
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redflyer
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RE: 727 Design Flaws?

Sun Sep 09, 2007 1:30 am

Quoting Prebennorholm (Reply 23):
Ever flown on a Tu-154 or IL-62?

First thing to discover when entering the cabin: Have I entered a time machine and gone a hundred years back in time?

Second thing: Hey, something is different, no need to rub elbows with fellow passengers.

Which means if they were ever flown by an airline in the West, they'd have 7-abreast seating.  Wink
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aeroweanie
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RE: 727 Design Flaws?

Sun Sep 09, 2007 8:12 am

Quoting 411A (Reply 8):
Not quite correct.
Search the NTSB database for a B727 (NW, as I recall) ferry flight, where the pitot heat was not switched on prior to departure.
The accident was near White Plains, NY.

This was not a deep stall. This was a more conventional stall, followed by a "graveyard spiral". Here is the NTSB accident summary:

Quote:
PROBABLE CAUSE: "The loss of control of the aircraft because the flight crew failed to recognize and correct the aircraft's high-angle-of-attack, low-speed stall and its descending spiral. The stall was precipitated by the flight crew's improper reaction to erroneous airspeed and Mach indications which had resulted from a blockage of the pitot heads by atmospheric icing. Contrary to standard operational procedures, the flight crew had not activated the pitot head heaters."

There are several 727 accidents that could be deep stall related, but none was ever proven to be so. Brian Trubshaw, in his autobiography "Test Pilot" says that he was told that a 727 did get into a deep stall during flight testing, but quick thinking by the pilot saved the situation.
 
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RE: 727 Design Flaws?

Sun Sep 09, 2007 9:16 am

Can anyone confirm or deny that the DC-10 was only aircraft to have the hydraulic system routed through the leading edge of the wing near the slats? If other aircraft from that time had the same design, what were they?

Quoting OldAeroGuy (Reply 33):
However an AD was issued that required revisions to the DC-10 hydraulic/slat systems. This is indicative of a design flaw.

True, and one could argue that point. But there was also an AD issued requiring stick shakers to be implemented on both control columns following that accident, (it was an option before then). Is that a design flaw too?

And while we're at it, an AD should have been issued requiring safety valves in the hydraulic system. The lack of one proved costly some 10 years later.

Quoting SEPilot (Reply 34):
The result was that numerous short cuts were taken in the design of the DC-10 that the other manufacturers would not have made (such as the routing of the hydraulic lines along the leading edge of the wing and the lack of check valves in the hydraulic systems.)

The DC-10 was rushed and it showed, as in comparison the L-1011 was far more advanced. Yet ironically, the DC-10 outperformed the Tristar and the -30 exceeded expectations. Years later, plenty of time was spent on the MD-11 and it didn't meet performance expectations initially, go figure.

Quoting AeroWeanie (Reply 39):
There are several 727 accidents that could be deep stall related, but none was ever proven to be so.

Most of those were classified as pilot error on approach, flying from the "seat of their pants" instead of by the book. I wouldn't doubt a deep stall played a part in one of those accidents, however.
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RE: 727 Design Flaws?

Sun Sep 09, 2007 4:18 pm

Quoting TrijetsRMissed (Reply 40):
And while we're at it, an AD should have been issued requiring safety valves in the hydraulic system. The lack of one proved costly some 10 years later.

Right after the ORD crash the DC-10's slats had lockouts installed so that the air loads would not cause them to retract in the event of a loss of hydraulic pressure on the slat drive actuators.
The slats on the left wing of the AA DC-10 retracted after the engine departed and the hydraulic system bled out causing the stall. It is my understanding that the pilot flew the airplane at the engine-out speed, not the speed needed when one wing has the slats retracted, I'm sure that they had an asymmetry light on, but were to busy with the engine out.

The shutoff valves installed after the Sioux City crash shut off the fluid in the #3 system to the tail if the reservoir level went below 4 gallons. Those three systems come together in one place on that airplane, and that is on the top of the horizontal stabalizer, it was just shear luck that the blades that came out of that engine just happened to travel straight down and forward to that exact point.
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RE: 727 Design Flaws?

Mon Sep 10, 2007 12:21 am

Quoting Ex52tech (Reply 41):
Those three systems come together in one place on that airplane, and that is on the top of the horizontal stabalizer, it was just shear luck that the blades that came out of that engine just happened to travel straight down and forward to that exact point.

This is what is known as Sod's Law. If a thing goes wrong it will go wrong in the worst possible way. Often confused with Murphy's Law (including on Wikipedia), which states that if something can go wrong it will.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
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RE: 727 Design Flaws?

Mon Sep 10, 2007 4:53 am

Quoting Ex52tech (Reply 41):
The slats on the left wing of the AA DC-10 retracted after the engine departed and the hydraulic system bled out causing the stall. It is my understanding that the pilot flew the airplane at the engine-out speed, not the speed needed when one wing has the slats retracted, I'm sure that they had an asymmetry light on, but were to busy with the engine out.

One other factor on the AA DC-10 was that the asymmetric slat warning was powered by the generator on the departed engine, so the pilots had NO indication of the asymmetric condition. One procedural change that was made after this accident was that the engine-out speed was raised so that the plane would fly with asymmetric slats at engine-out speed, which was not the case with the old speed (which was essentially minimum flying speed.) The AA pilots had followed the book and reduced to the engine out speed, but since they didn't know about the asymmetric slats (they didn't know the engine had departed; they just knew it wasn't working) they couldn't control the plane at that speed.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
Blackbird
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RE: 727 Design Flaws?

Mon Sep 10, 2007 7:42 am

SEPilot,

I thought the merger was an even merger... I didn't know McDonnell Douglas was in a position of control over the DC-10 program. Either way, I don't know why they let Douglas continue designing it's aircraft -- they were fools to ignore that kind of experience.


Andrea Kent
 
TrijetsRMissed
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RE: 727 Design Flaws?

Mon Sep 10, 2007 3:22 pm

Quoting Ex52tech (Reply 41):



Quoting SEPilot (Reply 43):

At the time of the accident, the normal engine out procedure on take-off climb was to reduce speed to V2. Of course we know now this is the worst thing one can do, as the FAA realized following this accident. Conceivably, the pilot could have flown the aircraft out and made an emergency landing at higher than normal speed. It's been done in simulators.

Additionally, the left engine also powered the captain's stick shaker. Since AA did not exercise the F/O stick shaker option, the crew had no idea they were entering the stall until it was too late.

Quoting Blackbird (Reply 44):
I thought the merger was an even merger... I didn't know McDonnell Douglas was in a position of control over the DC-10 program.

The McDonnell side of the company pretty much self destructed Douglas. Because the DC-10 program did not run smoothly, McDonnell would not allow Douglas to design a completely new type again. As you can see, from then on it was improved variants of existing types.
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777236ER
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RE: 727 Design Flaws?

Mon Sep 10, 2007 6:59 pm

Quoting AeroWeanie (Reply 39):

There are several 727 accidents that could be deep stall related, but none was ever proven to be so. Brian Trubshaw, in his autobiography "Test Pilot" says that he was told that a 727 did get into a deep stall during flight testing, but quick thinking by the pilot saved the situation.

From this http://www.aiaa.org/content.cfm?pageid=360&id=394 book, Boeing seemed absolutely convinced that the 727 couldn't get into a deep stall, with the loss of lift from the stalling wings and horizontal stabiliser pitching the nose down before the horizontal stabiliser would enter the separated wake of the wing. I don't know whether it's true, almost true, a bit of spin or a complete lie.
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RE: 727 Design Flaws?

Tue Sep 11, 2007 12:50 am

Quoting Blackbird (Reply 44):

I thought the merger was an even merger... I didn't know McDonnell Douglas was in a position of control over the DC-10 program. Either way, I don't know why they let Douglas continue designing it's aircraft -- they were fools to ignore that kind of experience.

It was touted as such, just as the Daimler-Chrysler merger was touted as "a marriage of equals." But in fact it was McDonnell taking over Douglas, just as it was Daimler taking over Chrysler. You are absolutely correct that they were fools in the way they managed it; the McDonnell people knew as much about the commercial aircraft business as our government knows about efficiency. The fact that they thought they knew better than the Douglas people is IMHO the biggest reason why they failed, and the McDonnell influence on Boeing (re Stonecipher and the fact that the biggest Boeing stockholder is a McDonnell) is again IMHO not at all positive. McDonnell knew military aviation and how to win military contracts. That has as much relation to civil aviation as chess has to football.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
N231YE
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RE: 727 Design Flaws?

Tue Sep 11, 2007 1:06 am

Quoting SEPilot (Reply 47):

To add to the discussion, I read that the DC-9 program was at fault for the Douglas "merger" (takeover).

Back in the early-mid 60's, Douglas designed the DC-9 as an indirect competitor to the 727.

Boeing, if you remember, went with three engines on the 727 as a compromise: UA wanted 4 in order to operate out of DEN, while EA wanted 2 for efficiency-operationg out of MIA. After the 727 was a reality, EA was still not thoroughly happy, although they did place an order for the 727. So Douglas designed the DC-9 to fill in that niche (remember, the 737 was not around-it was Boeing's answer to the DC-9). During the design of the DC-9, Douglas severely underestimated the DC-9, and they decided not to invest much capital towards tooling, labor, etc., since Douglas thought the DC-9 would never be a big seller (I believe they estimated only 250 frames, but not exactly sure of the original estimate).

Time would prove this estimate wrong, and this was a classic case of where too much demand will put a company out of business. Douglas essentially bled themselves to death, and needed money to purchase more tooling, pay more labor, etc. to increase capacity of the DC-9 production. That is when the McDonnell Corporation came in...
 
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RE: 727 Design Flaws?

Tue Sep 11, 2007 1:27 am

Quoting N231YE (Reply 48):
Time would prove this estimate wrong, and this was a classic case of where too much demand will put a company out of business. Douglas essentially bled themselves to death, and needed money to purchase more tooling, pay more labor, etc. to increase capacity of the DC-9 production. That is when the McDonnell Corporation came in...

This is my recollection as well. I also remember that Donald Douglas was paying more attention to his secretary (I believe it was) with whom he was fooling around than to business, and never was that great a businessman to begin with. He was one of the great plane designers of history, but his business skills did not match. The end result was that by the time the M-D merger came about Douglas was in desperate financial straits, and had to merge with somebody or fail. The McDonnell merger looked good from a financial standpoint, but it was a disastrous combination of conflicting cultures.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler

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