Search found 66 matches

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by aeroguy
Wed Sep 26, 2001 12:52 pm
Forum: Technical/Operations
Topic: Temperature And Airspeed
Replies: 19
Views: 2929

RE: Temperature And Airspeed

It seems that EssentialPowr and I are thinking along the same lines. I don't doubt that an airliner would use its INS to determine ground speed. That's all well and good but I don't see how that explains why ground speed would change with temperature. That's why I interpreted ground speed to be equi...

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by aeroguy
Wed Sep 26, 2001 7:30 am
Forum: Technical/Operations
Topic: Temperature And Airspeed
Replies: 19
Views: 2929

RE: Temperature And Airspeed

It has to do with how ground speed is calculated. Your ground speed is calculated using the pressure measured at altitude but ground level density. Since you put in a lower temperature for the ground, the ground density has now gone up. The velocity calculated by the instruments is inversely proport...

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by aeroguy
Sun Sep 23, 2001 10:39 am
Forum: Technical/Operations
Topic: Brayton Cycle
Replies: 1
Views: 1820

RE: Brayton Cycle

I don't think I've ever seen a Brayton Cycle P-V diagram where the air enters the engine at a pressure lower than ambient. The inlet acts as a diffuser, so I don't think it's possible to have a pressure drop. Perhaps the diagram you are looking at is using Sea Level pressure as the outside pressure....

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by aeroguy
Mon Sep 10, 2001 1:47 am
Forum: Technical/Operations
Topic: Do Engine Blades Touch The Surrounding Surface?
Replies: 19
Views: 6464

RE: Do Engine Blades Touch The Surrounding Surface

I'm not really sure how the active clearance control actually senses the clearance or not. I've worked with high pressure turbines, but not with the ACC, so the exact details are a little beyond my experience. Perhaps someone else can provide information on whether there is a clearance sensing syste...

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by aeroguy
Sun Sep 09, 2001 3:18 am
Forum: Technical/Operations
Topic: Do Engine Blades Touch The Surrounding Surface?
Replies: 19
Views: 6464

RE: Do Engine Blades Touch The Surrounding Surface

As far as turbine blade clearances are concerned, the FADEC has the ability to adjust the tip clearance using the rotor active clearance control. The active clearance control system uses "cool" bleed air from the compressor to cool the case around the turbine. The cooling air restricts the thermal g...

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by aeroguy
Sat Sep 08, 2001 8:19 am
Forum: Technical/Operations
Topic: Venturi's
Replies: 10
Views: 1458

RE: Venturi's

I would go with answer B (reduce pressure) as well. A vacuum implies a region of space in which no matter or mass is present. Since a venturi is explained by the principle of conservation of mass, you can't have an operating venturi that has a vacuum. WingScrubber, I think you made some typos in you...

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by aeroguy
Fri Sep 07, 2001 10:53 am
Forum: Technical/Operations
Topic: Do Engine Blades Touch The Surrounding Surface?
Replies: 19
Views: 6464

RE: Do Engine Blades Touch The Surrounding Surface?

The TF39 sort of has a 2 stage fan of sorts. It's sometimes referred to a 1 1/2 stage fan since the first stage has about half the span of the second. You have to see it to believe it, it's a truly unique design: <a href="http://aircraftenginedesign.com/pictures/TF39.gif" target=_blank>http://aircra...

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by aeroguy
Thu Sep 06, 2001 6:04 am
Forum: Technical/Operations
Topic: The Laws Of Combustion
Replies: 5
Views: 3097

RE: The Laws Of Combustion

As far as engines needing compressors, pure ramjets and scramjets are good examples of engines that don't have compressors. Of course, the compression process still takes place, it just isn't done by turbomachinery like in a gas turbine engine. I guess if you really really really wanted to you could...

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by aeroguy
Tue Sep 04, 2001 6:22 am
Forum: Civil Aviation
Topic: Why 4 Engines?
Replies: 29
Views: 1983

RE: Why 4 Engines?

You might also keep in mind span loading and structural considerations of 4 engines vs. 2. According to Airbus, the A330/A340 have virtually identical wings and there is only about 2% difference in structural content between the two aircraft. The 2 extra engines on the A340 greatly reduce the wing b...

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by aeroguy
Sun Sep 02, 2001 1:41 am
Forum: Military Aviation & Space Flight
Topic: V-22 Single Engine Ops
Replies: 4
Views: 3423

RE: V-22 Single Engine Ops

The V-22's engines are cross coupled by a shaft through the wing that allows one engine to provide power to both rotors. The V-22 would obviously have less power in single engine operation, but at least both proprotors would have some power. I've read that the V-22 also has some limited autorotation...

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by aeroguy
Thu Aug 30, 2001 11:20 am
Forum: Technical/Operations
Topic: High-bypass Fans At Altitude
Replies: 8
Views: 2974

RE: High-bypass Fans At Altitude

I hate to yank out an equation to make sense of all this but it might help. Here's a simplified equation for steady state rate of climb assuming constant airspeed: Rate of Climb = Velocity*(Thrust-Drag)/Weight or if you prefer (Power Available-Power Required)/Weight I would suspect the answer lies i...

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by aeroguy
Thu Aug 23, 2001 12:26 pm
Forum: Technical/Operations
Topic: V2500
Replies: 12
Views: 2882

RE: V2500

I've also heard that the V2500 is quieter than the CFM56. It seems that the V2500 is more fuel efficient: V2500 Cruise SFC: 0.575 CFM56-5B Cruise SFC: 0.596 However, as was said (and CFMI will quickly point out), the CFM56 has evidently been historically easier/cheaper to maintain, hence lower opera...

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by aeroguy
Tue Aug 21, 2001 1:19 am
Forum: Military Aviation & Space Flight
Topic: Glowing Rings Of Afterburners
Replies: 3
Views: 2257

RE: Glowing Rings Of Afterburners

Yes, those rings you are seeing are caused by a series of expansion waves and oblique shock waves within the exhaust jet. They are constantly reflected off the boundary surface (which is the interface between the high speed jet and the surrounding air). An oblique shock reflects off the boundary sur...

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by aeroguy
Mon Aug 20, 2001 12:18 pm
Forum: Technical/Operations
Topic: Runway Required For Takeoff
Replies: 5
Views: 2788

RE: Runway Required For Takeoff

You might want to check this section of Boeing's website: <a href="http://www.boeing.com/assocproducts/aircompat/#2" target=_blank>http://www.boeing.com/assocproducts/aircompat/#2</a> Under "Aircraft Planning Manuals and Product Brochures", there are documents for each of Boeing's airplanes. In sect...

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by aeroguy
Sat Aug 18, 2001 12:38 pm
Forum: Technical/Operations
Topic: The MD-90 And UHB Fans
Replies: 9
Views: 5870

RE: The MD-90 And UHB Fans

It's too bad about the UDF engines not having any commercial success, they were a really neat design. I guess the public is a little wary of engines that are or resemble turboprops though. I think the GE/NASA team actually received the Collier Trophy in 1987 for their work on UDF development. <br><c...

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by aeroguy
Wed Aug 15, 2001 1:45 am
Forum: Technical/Operations
Topic: 737-200 Engines.
Replies: 6
Views: 4856

RE: 737-200 Engines.

I just thought I'd throw some numbers out there for those debating high vs. low bypass engine airflow. Compare for yourselves: JT8D-200 18500-21000 lbs. thrust Fan diameter: 48 in. Bypass ratio: 1.77 Air flow: 488 lbs/sec CFM56-3 20000-23500 lbs. thrust Fan diameter: 60 in. Bypass ratio: 5.0 Air flo...

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