jgore
Posts: 518
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Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 1:25 pm

I always liked those new 737 NG engines, but never asked myself why the engine's intake is not completely round, just because I didn't pay attention.


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Now that I do, I ask to myself and you guys:
This kind of intake isn't inefficient ?. What do you think this shape would be intended for ?

Thanks.

Jgore  Smile
 
covert
Posts: 1500
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 1:29 pm

Same as why it isn't round on the -300......

Do you want the bottom to scrape the ground?
none
 
jgore
Posts: 518
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 1:33 pm

"Do you want the bottom to scrape the ground?"

Mmmmm, I'm afraid that's not the reason. According to what you say, it would happend with the GE90s also.

Just guessing, don't know though.


Jgore  Smile
 
ndege
Posts: 201
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 1:39 pm

Everything I've ever heard or read says it's because of ground clearance with possible wing flexing. The 777 has a little more clearance than a 737. I've wondered why Boeing didn't extend the gear struts a little more, but I'm sure as I'm not an engineer and definitely not paid to come up with these questions and excuses for them, there's probably a very valid reason for it.

BL
 
IMissPiedmont
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 1:49 pm

If you look closely you will see that the 737NG does indedd have a rounder inlet that the -300 through -600. The reason is that the gear is slightly longer.

"The 777 has a little more clearance than a 737." A little? Maybe 6 feet or so.
The day you stop learning is the day you should die.
 
cdfmxtech
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 2:04 pm

The 737-300 shares a common airframe with the earlier 737s. The CFMs are obviously bigger than the Pratss, so the design of the engine with the "flat bottom" was necessary. Accessories were located to the side instead of the bottom.
There is no effect on efficiency. The powerplant itself is just as round as any other. Its the Cowling (Nose, Fan and Core - TRs) that is oval. The accessories on ths side gives the engine its overall oval shape.

P.S. - U r aware that the 2 aircraft that u have pictured are not Next Gen 737s??
 
ha763
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 2:32 pm

Boeing did not extend the 737 struts on the -300/-400/-500 and only slightly on the NG's to keep the airplane low enough to not need any ground equipment for fueling, cargo loading, engine maintenace. This and the larger size of the CFM engines compared to the P&W, meant there had to be a flattened bottom to ensure that there was enough clearance.
 
ndege
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 3:31 pm

"The 777 has a little more clearance than a 737." A little? Maybe 6 feet or so.

I was using some strange lingual instrument to downplay the extremity of the difference. What do you call that one again?

BL
 
sudden
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 9:30 pm

I was a little lost on this topic to begin with, cause the easiest way to differ a the older from the NG up front is the engines. The NG don't have the oval shape.

Aim for the sky.
Sudden
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doug_or
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 07, 2003 10:33 pm

Reading an AW&ST article a good while ago re: stage IV noise requirements Boeing basicaly said that further extending the gear (in this case to make room for larger, higher bypass engines) would not be worth it. The amount of redesign necesary for the wing and central fues would be extensive. I guess its already packed pretty tight in there.
When in doubt, one B pump off
 
garuda
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RE: Why Not Round Engines Intake On 737 NG's?

Sat Mar 08, 2003 12:33 am

Just an addition... Extending the gear also mean adding more weight, reducing payload/range.
 
cdfmxtech
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RE: Why Not Round Engines Intake On 737 NG's?

Sat Mar 08, 2003 1:51 am

The Next Gens are still oval. It just isn't as pronounced as it is on the Classic B7373s
 
Klaus
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RE: Why Not Round Engines Intake On 737 NG's?

Sat Mar 08, 2003 2:17 am

Some knowledgeable forum member once mentioned that the asymmetrical inlet form does indeed reduce the efficiency of the engines by a few percent. But as had been said, this loss was deemed acceptable when considering the overall cost/benefit relation.
 
brons2
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RE: Why Not Round Engines Intake On 737 NG's?

Sat Mar 08, 2003 3:07 am

Mmmmm, I'm afraid that's not the reason

Mmmmmm, afraid that *IS* the reason.

Read up on your 737 history at the Boeing web site...

The Boeing 737-300

The Boeing 737-300 program was launched in March 1981. The market requirements for this derivative airplane became clear during the late 1970s in an environment of airline deregulation and the fierce competition that followed.

As a result of increased competition, there were changes in the way air routes were served at that time. Airplanes flew into airports operated as hubs, then dispersed into a spoke configuration, often to short distance destinations. The 737 proved ideal for airlines operating frequent short-to-medium-range routes.

A fuselage extension of 104 inches (2.6 m) allowed the 737-300 to accommodate seats for up to 20 more passengers than its predecessor, the 737-200 model. In mixed-class service with 36/32-inch pitch (91/81 cm), the -300 seats 128 passengers; in an all-tourist arrangement at 32-inch pitch (81 cm), seating is 140. For inclusive-tour charter service (30-inch pitch, or 76 cm), a maximum of 149 passengers can be carried.

From the outset, one of the main objectives of the 737-300 program was to maintain commonality with the existing fleet. The airplane would use new and larger CFM56-3 engines, an advanced-technology flight deck and a common airframe. These features afforded airlines a lower investment in spares, interchangeable flight crews, and less ground support equipment and maintenance training. New aluminum alloys and composites were used to reduce the airplane's weight and aerodynamic improvements were adapted from the 757 and 767 airplanes.

Unlike its predecessor, the 737-200, which was powered by Pratt & Whitney JT8D engines mounted against the underside of the wing in long, thin nacelles, the power plants for the 737-300 -- as well as all subsequent versions of the 737 -- are mounted forward of the wing on struts. The ground-clearance problem created by the larger engines was solved by relocating engine accessories from the bottom of the engine to the side and flattening the bottom of the inlet lip. In addition, the nose wheel unit was attached five inches lower on the fuselage.

The 737-300 also received a new flight deck that makes use of digital technology like that of the 757 and 767. These electronics systems provide concise flight information, allowing increased fuel efficiency and improving the airplane's ability to land in bad weather.

The 737-300 also borrowed the 757-200's interior appointments, which include large enclosed bins, galleys and lavatories located fore and aft; and a wider cabin that allows airlines to choose a larger aisle or more window-seat headroom.

The first 737-300 rolled out of the Boeing Renton, Wash., plant Jan. 17, 1984, and made its initial flight Feb. 24, 1984. That began a nine-month flight test program, during which a fleet of three 737-300s logged nearly 1,300 hours in the air.

Certification of the 737-300 by the U.S. Federal Aviation Administration was awarded Nov. 14, 1984. First deliveries of the new aircraft occurred Nov. 28, 1984, to USAir and Nov. 30, 1984, to Southwest Airlines. Both carriers put their new aircraft into revenue service during December 1984. The British Civil Aviation Authority granted certification Jan. 29, 1985, the same day that Orion Airways of Great Britain became the first non-U.S. customer to take delivery of a 737-300.

The world's airlines ordered 1,112 737-300s over the 18 year period from 1981 through 1998. The last 737-300 is scheduled for delivery in December 1999, completing the production transition to its successor, the Next-Generation 737-700. The 737-300 holds a very special place in aviation history as the most popular model of the best-selling jetliner family.
Firings, if well done, are good for employee morale.
 
mandargb
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RE: Why Not Round Engines Intake On 737 NG's?

Sat Mar 08, 2003 11:53 am

What I recollect from the book "Boeing Airplanes" (I dont recollect the author now)

737: called as FLUF (Fat Little Ugly Fellow) !
Its mentioned that "flattening the engines not only solved the ground clearance problem but actually slightly improved the performance"

Its not mentioned how much and what kind of performance improvement was achieved.

But primarily it was done to get the better ground clearance.
 
IMissPiedmont
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Ndege

Sat Mar 08, 2003 1:44 pm

Sorry, I missed the fact that your tongue was firmly embedded in cheek when you wrote that the 777 is slightly taller than the 737.  Laugh out loud
The day you stop learning is the day you should die.
 
ndege
Posts: 201
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RE: Why Not Round Engines Intake On 737 NG's?

Sat Mar 08, 2003 2:01 pm

I suppose I'll let it slide just this once  Innocent
 
FLY777UAL
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RE: Why Not Round Engines Intake On 737 NG's?

Fri Mar 14, 2003 3:43 am

I'm still confused as to whether or not, as Cdfmxtech stated, you're aware that those pictures are of 737 classic and not NG aircraft...

F L Y 7 7 7 U A L
 
cloudy
Posts: 1613
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RE: Why Not Round Engines Intake On 737 NG's?

Mon Mar 17, 2003 2:33 pm

Its mentioned that "flattening the engines not only solved the ground clearance problem but actually slightly improved the performance"

----

I have seen this also, but in different sources. But this does not neccesarily contradict earlier comments from Klaus and others. My guess would be that it depends on exactly what kind of performance one is talking about.

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