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Why is the S-duct intake on the Tu-154 uniquely oblong?

Where is the APU in the case of an S-duct (like the L-1011)?How do I estimate how much air flows through the intake due to engine suction?Does intake mass-flow rate vary linear proportional with turbine fan speed?Why does intake of turbofan engine have angle of attack?How does a subsonic jet engine intake design ensure correct air intake?What is this F-18 Hornet “air intake” for?How much lift can be generated by the intake lip of a duct?How do engines cope with various intake airflow speeds?What is this tube in a jet engine's air intake?Why was the Electra uniquely vulnerable to whirl-mode flutter?

17

$begingroup$

Is there an advantage to the oval/elliptical shape of the Tu-154's S-duct intake? It appears to be taller and an overall different shape than the side-mounted cowlings.

This doesn't appear to be a feature common to trijets or even on those with S-ducts.

EDIT: Upon further research, it appears the 727-100 had an oblong intake (Thanks Terry!), and the Hawker Siddeley Trident had an entirely unique shape. So my original premise of the Tu-154 being "unique" no longer holds. I am still curious about the implications of the different designs.

aircraft-design multi-engine inlet lockheed-tristar tu-154

share|improve this question

edited May 17 at 13:42

zymhan

asked May 16 at 18:07

zymhanzymhan

850219

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  So I tried looking up some 727 photos to compare, and it looks to me like this photo has an oblong intake: warbirdsnews.com/wp-content/uploads/727finalflight-678x381.png while this one does not: deltamuseum.org/images/site/history-aircraft/boeing-727/… which seems odd?
  $endgroup$
  – zymhan
  May 16 at 18:39
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  The 727-100 had an oval duct and the 727-200 had a round duct.
  $endgroup$
  – Sports Racer
  May 16 at 18:41
  

  
  
  
  

add a comment | 

17

$begingroup$

Is there an advantage to the oval/elliptical shape of the Tu-154's S-duct intake? It appears to be taller and an overall different shape than the side-mounted cowlings.

This doesn't appear to be a feature common to trijets or even on those with S-ducts.

EDIT: Upon further research, it appears the 727-100 had an oblong intake (Thanks Terry!), and the Hawker Siddeley Trident had an entirely unique shape. So my original premise of the Tu-154 being "unique" no longer holds. I am still curious about the implications of the different designs.

aircraft-design multi-engine inlet lockheed-tristar tu-154

share|improve this question

edited May 17 at 13:42

zymhan

asked May 16 at 18:07

zymhanzymhan

850219

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  So I tried looking up some 727 photos to compare, and it looks to me like this photo has an oblong intake: warbirdsnews.com/wp-content/uploads/727finalflight-678x381.png while this one does not: deltamuseum.org/images/site/history-aircraft/boeing-727/… which seems odd?
  $endgroup$
  – zymhan
  May 16 at 18:39
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  The 727-100 had an oval duct and the 727-200 had a round duct.
  $endgroup$
  – Sports Racer
  May 16 at 18:41
  

  
  
  
  

add a comment | 

$begingroup$

Is there an advantage to the oval/elliptical shape of the Tu-154's S-duct intake? It appears to be taller and an overall different shape than the side-mounted cowlings.

This doesn't appear to be a feature common to trijets or even on those with S-ducts.

EDIT: Upon further research, it appears the 727-100 had an oblong intake (Thanks Terry!), and the Hawker Siddeley Trident had an entirely unique shape. So my original premise of the Tu-154 being "unique" no longer holds. I am still curious about the implications of the different designs.

aircraft-design multi-engine inlet lockheed-tristar tu-154

share|improve this question

edited May 17 at 13:42

zymhan

asked May 16 at 18:07

zymhanzymhan

850219

$endgroup$

share|improve this question

edited May 17 at 13:42

zymhan

asked May 16 at 18:07

zymhanzymhan

850219

share|improve this question

edited May 17 at 13:42

zymhan

asked May 16 at 18:07

zymhanzymhan

850219

asked May 16 at 18:07

zymhanzymhan

850219

asked May 16 at 18:07

zymhanzymhan

850219

2 Answers
2

active

oldest

votes

11

$begingroup$

This doesn't fully answer the question, but the B727-100 also had an oval engine intake.

AIRLINERS magazine Sept/Oct 99 edition:

"The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center engine inlet increased the thickness of the "boundry layer" of air on the fuselage forward of the inlet. This would have caused aerodynamic "blanking," or disruption of airflow into the center engine, without changes to the design. The circular inlet allowed a smooth flow of air into the engine, as it elevated the bottom of the inlet away from the fuselage boundry layer and into the air stream."

share|improve this answer

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  That's definitely a step in the right direction! On an unrelated note, I love that VP-BAP is one of the few privately owned 727s still operating in the US.
  $endgroup$
  – zymhan
  May 16 at 19:05
  

  
  
  
  

add a comment | 

0

$begingroup$

The vertical fin is tall and thin, so it makes sense that an inlet/duct mounted in the fin and configured for optimum streamlining might not be perfectly round.

share|improve this answer

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429

$endgroup$

add a comment | 

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11

$begingroup$

This doesn't fully answer the question, but the B727-100 also had an oval engine intake.

AIRLINERS magazine Sept/Oct 99 edition:

"The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center engine inlet increased the thickness of the "boundry layer" of air on the fuselage forward of the inlet. This would have caused aerodynamic "blanking," or disruption of airflow into the center engine, without changes to the design. The circular inlet allowed a smooth flow of air into the engine, as it elevated the bottom of the inlet away from the fuselage boundry layer and into the air stream."

share|improve this answer

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  That's definitely a step in the right direction! On an unrelated note, I love that VP-BAP is one of the few privately owned 727s still operating in the US.
  $endgroup$
  – zymhan
  May 16 at 19:05
  

  
  
  
  

add a comment | 

11

$begingroup$

This doesn't fully answer the question, but the B727-100 also had an oval engine intake.

AIRLINERS magazine Sept/Oct 99 edition:

"The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center engine inlet increased the thickness of the "boundry layer" of air on the fuselage forward of the inlet. This would have caused aerodynamic "blanking," or disruption of airflow into the center engine, without changes to the design. The circular inlet allowed a smooth flow of air into the engine, as it elevated the bottom of the inlet away from the fuselage boundry layer and into the air stream."

share|improve this answer

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  That's definitely a step in the right direction! On an unrelated note, I love that VP-BAP is one of the few privately owned 727s still operating in the US.
  $endgroup$
  – zymhan
  May 16 at 19:05
  

  
  
  
  

add a comment | 

$begingroup$

This doesn't fully answer the question, but the B727-100 also had an oval engine intake.

AIRLINERS magazine Sept/Oct 99 edition:

"The oval shape inlet on the 727-100 series was changed to a circular design on the stretched 727-200. This was a direct result of the new aircraft's longer fuselage. In flight, the increased lengths from the nose to the center engine inlet increased the thickness of the "boundry layer" of air on the fuselage forward of the inlet. This would have caused aerodynamic "blanking," or disruption of airflow into the center engine, without changes to the design. The circular inlet allowed a smooth flow of air into the engine, as it elevated the bottom of the inlet away from the fuselage boundry layer and into the air stream."

share|improve this answer

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

$endgroup$

share|improve this answer

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

answered May 16 at 18:48

Mike SowsunMike Sowsun

21.5k27089

0

$begingroup$

The vertical fin is tall and thin, so it makes sense that an inlet/duct mounted in the fin and configured for optimum streamlining might not be perfectly round.

share|improve this answer

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429

$endgroup$

add a comment | 

0

$begingroup$

The vertical fin is tall and thin, so it makes sense that an inlet/duct mounted in the fin and configured for optimum streamlining might not be perfectly round.

share|improve this answer

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429

$endgroup$

add a comment | 

$begingroup$

The vertical fin is tall and thin, so it makes sense that an inlet/duct mounted in the fin and configured for optimum streamlining might not be perfectly round.

share|improve this answer

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429

$endgroup$

share|improve this answer

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429

answered May 16 at 22:01

quiet flyerquiet flyer

2,003429