columba
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Question About The 737-100 Design

Sat Jul 26, 2008 10:11 am

I was wondering why Boeing has opted for the 737 design as we know it.
Most shorthaul jets of that time like the Caravelle, Bac 1-11 or Dc 9 were T-tailed aircraft with rear mounted engines, also the 727 was designed and built that way.
Would be interesting to know if the 737 was designed as a t-tailed aircraft, too ?
It will forever be a McDonnell Douglas MD 80 , Boeing MD 80 sounds so wrong
 
MYT332
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 11:05 am



Quoting Columba (Thread starter):
Would be interesting to know if the 737 was designed as a t-tailed aircraft, too ?

Well if it was then the guys that put it together sure couldn't read instructions.
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Oykie
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 12:05 pm

The 737 was a fast development from Boeing to counter the DC-9. Boeing based the 737-100 on the 727, but with a new wing to ease development. It shares 60 % of the structure of the 727. Why they did not went on with a T-tail, I do not know.

but you can read more about the development on Wikipedia.

http://en.wikipedia.org/wiki/Boeing_737
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PlunaCRJ
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 12:16 pm

I have seem some early concepts of the 737 with the t-tail.

Eventually, Boeing discarded it because they didn´t want to deal with the deep stall problems inherent to the t-tail design.
 
columba
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 12:29 pm



Quoting Myt332 (Reply 1):
Well if it was then the guys that put it together sure couldn't read instructions.

 grumpy  I guess you understood what I have really meant so no need for such great statements.
It will forever be a McDonnell Douglas MD 80 , Boeing MD 80 sounds so wrong
 
MYT332
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 12:37 pm



Quoting Columba (Reply 4):
I guess you understood what I have really meant so no need for such great statements.

British humour, I couldn't resist. It's not like I mentioned the war?

If you go to the below link and read the "Where to put the Engines" section then you'll see the B737 was originally considered as a T-Tail aircraft like PlunaCRJ mentioned and that the final design of the B731 resulted in a weight saving of 700kgs vs the original T-Tail layout.

http://www.b737.org.uk/history.htm
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milesrich
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 4:17 pm



Quoting PlunaCRJ (Reply 3):

You are exactly correct. After the four 727 accidents in 1965-66 involving deep stalls, UA approaching ORD over Lake Michigan, UA at SLC, AA at CVG and AK, Beoing was done with placing the engines in the rear. Also placing an engine there, meant running fuel lines through the rear of the fuselage.
 
BI601BN
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 5:24 pm

The 737-100 configuration resulted in a slightly lighter and better balanced aircraft (for such a short fuselage length) than a T-Tail design. Once it became clear that such a design would work, it was also realized that the 737 would be easier and cheaper to maintain. Joe Sutter's book "747: Creating the World's First Jumbo Jet and Other Adventures from a Life in Aviation" has a bit on the "why" of the 737 design.

BN601BN
 
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UltimateDelta
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 5:45 pm



Quoting BI601BN (Reply 7):
Once it became clear that such a design would work, it was also realized that the 737 would be easier and cheaper to maintain.

And that was the whole premise of the 737. That's why the engines were attached directly to the wings without real pylons.
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jogales
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 6:23 pm



Quoting UltimateDelta (Reply 8):
And that was the whole premise of the 737. That's why the engines were attached directly to the wings without real pylons.

According to Joe Sutter's book, the engine placement is because putting them on pylons would make the engine inlets too far forward.

Josh
-
 
cf6ppe
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RE: Question About The 737-100 Design

Sat Jul 26, 2008 6:40 pm



Quoting Milesrich (Reply 6):
You are exactly correct. After the four 727 accidents in 1965-66 involving deep stalls, UA approaching ORD over Lake Michigan, UA at SLC, AA at CVG and AK, Beoing was done with placing the engines in the rear. Also placing an engine there, meant running fuel lines through the rear of the fuselage.

The B727 accidents listed were due to high sink rates established for which recovery wasn't possible at the flight conditions. In at least the SLC and CVG incidents the main landing gears were pushed up through the fuel lines which attributed to the severity of the accidents.
Following those accidents, Boeing built a test rig to simulate the main gear being rammed up through the fuel lines (hoses) in excess of 75 mph. I don't remember how many fuel hoses were destroyed to find suitable replacements which could withstand the tests, but they were successful.
At the time that the above described tests were being conducted, I worked in the same (Boeing Field) Ellis Avenue laboratory. After the replacement hoses were spec'd out, I worked on additional tests of the new hoses determining seepage rates, etc.

The T-tail deep stall happened on the prototype BAC One-Eleven
http://aviation-safety.net/database/record.php?id=19631022-0

At the time, the DC-9 was in design. DAC extended the span of the DC-9 stabilizer by two feet on each end (four feet overall span increase) to get the ends of the stabilizer out of the wake created by the engines with the aircraft in a high nose up - i.e., deep stall - attitude.
 
SlamClick
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RE: Question About The 737-100 Design

Sun Jul 27, 2008 3:12 pm

No, actually it is funny. (and it is not making fun of your English) (And it's not like the Brits speak good English anyway!)

A T-tail has to be a much heavier structure than a conventional tail. There are incredible air loads imposed on the horizontal and vertical tailplanes, especially maneuvering at high mach numbers. When the horizontal stabilizer can be mounted off the fuselage itself, you can build a tapering vertical stabilizer that gets progressively lighter toward its tip. But when the horizontal stab is mounted to the top of the vertical all of the airloads from both vertical and horizontal surfaces must be carried by the base of the vertical fin. Frankly I don't know how they do it.

Quoting Milesrich (Reply 6):
UA at SLC,

As noted above, high sink rate; not a T-tail issue but, rather, a lack of famiarity with swept-wing flying characteristics.

Quoting Milesrich (Reply 6):
AA at CVG



Quoting CF6PPE (Reply 10):
CVG incidents

Wouldn't call this one (AA 383) either of the above. More of a CFIT. They were on a night 'visual' into 18 (now 18R) at KCVG. They were losing sight of the airport in deteriorating weather and, probably misled by their radio altimeter since they were over the Ohio River instead of the plateau where the airport sits, they descended to below field elevation. It wasn't a matter of sinking, but, rather, inability to start a climb fast enough that led to their striking trees.

That was 8 November 1965. It is a short walk from this crash site to that of TWA 128 a Convair 880 that crashed under very similar circumstances on 20 November 1967.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
Viscount724
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RE: Question About The 737-100 Design

Mon Jul 28, 2008 12:45 am



Quoting BI601BN (Reply 7):
The 737-100 configuration resulted in a slightly lighter and better balanced aircraft (for such a short fuselage length) than a T-Tail design.

The T-tail also results in a longer aircraft. Both the 737-100 and -200 are shorter than the shortest DC-9-10 (by 10 and 4 ft. respectively) but even the -100 can take at least more row of seats than the DC-9-10 at equivalent pitch, and of course has signficantly higher total seating than the DC-9-10 due to the 6-abreast fuselage width.
 
Blackbird
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RE: Question About The 737-100 Design

Mon Jul 28, 2008 3:48 am



Quote:
You are exactly correct. After the four 727 accidents in 1965-66 involving deep stalls, UA approaching ORD over Lake Michigan, UA at SLC, AA at CVG and AK, Beoing was done with placing the engines in the rear. Also placing an engine there, meant running fuel lines through the rear of the fuselage.

Huh? From what I remember, the first couple of crashes involving the B-727 did not involve deep stalls to the best of my knowledge.

IIRC, the first accident involved an UAL approaching into ORD at night. The airplane drifted below the glide-path due to the pilot apparently using too little thrust while conducting the approach with full-flaps. The plane slowed down and dropped like a rock and crashed into Lake Michigan killing everybody onboard

The second and third accidents (not sure which order) occured in which a UAL 727 was making an approach into Salt-Lake City at night and apparently the pilot got the plane into a high sink-rate, probably for the same reason as the first accident and crashed (The pilot of this airplane, Gale Kehmaier (47), had been a pilot with UAL since he was 23 and a captain since he was 25, but throughout all that time flew propeller planes, once trying to transition to DC-8's. He failed, and went back to propellers which he had a greater knack for than jets. He finally managed to get a jet-command, had very little time on the plane) killing all aboard from what I remember.
American 383 was the other one -- The plane took off out of LGA en route to CVG. The plane was a check-ride with the Captain finishing his IOE off (although he had 14,400 hrs experience, and been a captain for about 7 or 8 years with AA, he had no jet-experience other than the upgrade training and the IOE flights), due to the rapidly deteriorating weather in CVG, both pilots seemed to be beelining it, trying to beat the weather into Cincinnati; they entered the pattern at a high-rate of speed and with the Captain not as experienced in slowing a jet from 350 kts to a reasonable approach speed, simply idled the engines out (He didn't seem to use much brake and didn't extend the gears which would have helped a lot) and waited until the speed dropped enough to get the flaps out, and just kept extending them as fast as he could. The Check Captain had a great degree of confidence in Capt O'Neill (O'Neill had a great deal of experience and apparently was highly skilled) and didn't seem to monitor him as much as he should have. The position of the lights at the airport produced an optical illusion causing the crew to believe they were much higher than they were, which was only aggrevated by the altimeter set-up. The crew were using low power through out almost the whole approach and had taken on a high-descent rate which was corrected, however by now they were too low and had actually drifted into the Ohio River Valley and was below the elevation of the airport. The flaps were at 25-degrees and gears were still up when it struck the ground. All but 4 died.


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SEPilot
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RE: Question About The 737-100 Design

Mon Jul 28, 2008 10:48 pm



Quoting BI601BN (Reply 7):
Joe Sutter's book "747: Creating the World's First Jumbo Jet and Other Adventures from a Life in Aviation" has a bit on the "why" of the 737 design.

In fact, Joe Sutter was the one who determined that putting the engines on the wings would result in a lighter, shorter plane with one more row of seats than the T-tailed configuration. From my reading of the book this was the determining factor in Boeing going that way. Sutter also devised the engine placement so that the compressor was behind the main spar, so in the event of a catastrophic failure the fuel tanks would be protected by the spar.

Quoting UltimateDelta (Reply 8):
And that was the whole premise of the 737. That's why the engines were attached directly to the wings without real pylons.

Actually, according to Sutter, this was more because they wanted to keep the 737 as low to the ground as possible, aiding quick turnarounds. They wanted to be able to load and unload baggage without any lifts or conveyors. Sutter determined that by having the intake extended in front of the wing and the exhaust behind it there was little aerodynamic penalty; Boeing had determined on the B-47 that the optimal design for wing mounted jet engines was to hang the engine below and in front of the wing so that there was sufficient space between them for adequate airflow. This is still the best arrangement, and most airliners still use it. The 737 and 777 are the most notable exceptions; both of them have the top of the engine pretty much even with the upper surface of the wing; I believe it works because the engines are almost completely in front of the wing instead of partly below it.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
474218
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RE: Question About The 737-100 Design

Mon Jul 28, 2008 11:16 pm



Quoting Milesrich (Reply 6):
You are exactly correct. After the four 727 accidents in 1965-66 involving deep stalls, UA approaching ORD over Lake Michigan, UA at SLC, AA at CVG and AK, Beoing was done with placing the engines in the rear. Also placing an engine there, meant running fuel lines through the rear of the fuselage.

They still had to run a fuel line through the aft fuselage to the APU, so I don't think that was the reason.
 
tdscanuck
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RE: Question About The 737-100 Design

Tue Jul 29, 2008 12:03 am



Quoting SEPilot (Reply 14):
Sutter also devised the engine placement so that the compressor was behind the main spar, so in the event of a catastrophic failure the fuel tanks would be protected by the spar.

Something doesn't sound right about that...if the disks are behind the spar then the spar provides no protection. The spar is almost exactly in the plane of the disk anyway, so the chances of hitting the spare are quite low. He might have been going for protecting the passenger cabin using the wing structure (upper and lower skins).

Quoting SEPilot (Reply 14):
The 737 and 777 are the most notable exceptions; both of them have the top of the engine pretty much even with the upper surface of the wing; I believe it works because the engines are almost completely in front of the wing instead of partly below it.

It works because of extensive CFD modeling. There are lot of ways to design that particular arrangement badly.

Tom.
 
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Starlionblue
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RE: Question About The 737-100 Design

Tue Jul 29, 2008 12:37 am



Quoting 474218 (Reply 15):
They still had to run a fuel line through the aft fuselage to the APU, so I don't think that was the reason.

That fuel line (+ fuel pump) is much smaller than what would be required for engines.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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SEPilot
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RE: Question About The 737-100 Design

Tue Jul 29, 2008 10:02 am



Quoting Tdscanuck (Reply 16):
Something doesn't sound right about that...if the disks are behind the spar then the spar provides no protection.

Well, I'm working from memory; I know he made a point about having the disks behind the main spar, and I thought it was to protect the fuel tanks, but I could be wrong. But I believe it is academic; I do not know of any 737 Jurassic that ever had an uncontained engine failure.

Quoting Tdscanuck (Reply 16):

It works because of extensive CFD modeling. There are lot of ways to design that particular arrangement badly.

Yes, I'm sure there are. And when the original 737 was designed, to say nothing of the B-47 and 707, those tools were unavailable.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
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longhauler
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RE: Question About The 737-100 Design

Tue Jul 29, 2008 2:05 pm



Quoting SEPilot (Reply 18):
I do not know of any 737 Jurassic that ever had an uncontained engine failure.

http://en.wikipedia.org/wiki/Pacific_Western_Airlines_Flight_501



http://en.wikipedia.org/wiki/British_Airtours_Flight_28M
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
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SEPilot
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RE: Question About The 737-100 Design

Tue Jul 29, 2008 2:09 pm

The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
PGNCS
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RE: Question About The 737-100 Design

Sat Aug 02, 2008 3:02 am



Quoting SlamClick (Reply 11):
Wouldn't call this one (AA 383) either of the above. More of a CFIT. They were on a night 'visual' into 18 (now 18R) at KCVG.

It's now actually 18C, but I know what you meant!  Smile
 
SlamClick
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RE: Question About The 737-100 Design

Sat Aug 02, 2008 4:34 am



Quoting PGNCS (Reply 21):
It's now actually 18C, but I know what you meant!

Well, turn your back on an airport for nine years and they change it all around!  Smile
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Blackbird
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RE: Question About The 737-100 Design

Sun Aug 03, 2008 1:14 am

Well, all cases in which the early B727's crashed could be argued to be CFIT. However, the reason they crashed was because they took on too high a descent rate for one reason or another at night. In most if not all the cases, the crew were inexperienced on the type (if not just because the 727's were brand new).


Blackbird
 
SlamClick
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RE: Question About The 737-100 Design

Sun Aug 03, 2008 2:44 pm



Quoting Blackbird (Reply 23):
Well, all cases in which the early B727's crashed could be argued to be CFIT.

Not if you know that the first letter in that acronym stands for "controlled"

Set up a very high rate of sink, power off, close to the ground and then ram on a bunch of throttle to engines that are going to take more time to spool up than you have remaining before you hit the ground and you are not actually in control. Get the same very high sink rate going in a swept-wing airplane and pull the nose up and you are simply asking the plane to do something it cannot do; in other words you are not in control, Isaac Newton is. When you have maneuvered an airplane beyond its stable flight envelope you are no longer in control, you are a passenger with a very good view of the crash.

The CVG crash was CFIT because their problem wasn't so much that they had gotten an excessive sinker going but that, misled by a radio altimeter that was, up until two seconds before impact, reading the distance to the bottomland along the Ohio River, and loss of visual cues, they made a normal, if slightly steep descent to below terrain elevation. Classic CFIT only aggravated a bit by sink rate. They struck virtually the first tree on high ground once they cleared the bluffs above Stringtown Kentucky and they struck it in more or less level flight or just initiating a climb.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
Blackbird
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RE: Question About The 737-100 Design

Sun Aug 03, 2008 4:19 pm

Actually I just re-read the thing you're right. Their descent rate was pretty much okay in the last couple of seconds of flight. It was a bit high just before that, but they had corrected it.

However, the high rate of descent was attributable partially to the B-727's flap design... but the crew really should have been more careful about the whole thing. Captain Teelin (Check Captain / PIC) should have been more carefully monitoring Captain O'Neill (Pilot undergoing IOE), they shouldn't have entered the pattern at such a high-rate of speed, or should have employed the full air-braking capabilities of the plane: Use liberal use of speed-brakes, keep the descent rate low as you can (increase the attitude/AoA a bit) put the gears down at 270 kts (maximum safe gear extension speed), and the start lowing the flaps at the highest possible speed you can safely get away with (You can keep it on idle all the way until the flaps start coming out -- you *need* power after that) -- it definetly wouldn't be the most elegant approach, but they would have made it into CVG that night (Nov 8, 1965)


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