Mr Spaceman
Topic Author
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Joined: Thu Mar 15, 2001 5:09 am

DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 3:58 am

Hi guys. Can someone please tell me what the "Air Intakes" on the nose of these aircraft [DC-8, DC-10, L-1011], are used for? Do they provide air for the same reason, on all 3 types?

The first possibilities that come to my mind are to do with Cabin Pressurization, or perhaps Air Conditioning. However, I suspect that I'm wrong.

I've noticed that each Intake Scoop also seems to have a Exhaust Vent directly behind it. What is this vents' function?

Finally, why has this feature dissapeared from the more modern Airline Jets [you don't see these intakes on an Airbus or Boeing 757, 767, 777, etc.], is it Old Technology? Actually, you don't see these intakes on a lot of Older airliners either. I've spotted them on just a few.


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Photo © Allan Rossmore



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Photo © Lawrence Feir



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Photo © Don Boyd



Thanks,
Chris

"Just a minute while I re-invent myself"
 
JT-8D
Posts: 423
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RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 4:06 am

To be brief, they air air inlets for the airconditioning system. The dc-8 used a freon aircon system, the other two use air cycle. Both need a source of air for pressurizing the cabin, or in the later two, cooling the heat exchangers. Need more, just ask..Jt
 
JT-8D
Posts: 423
Joined: Sun Dec 31, 2000 11:34 pm

RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 5:21 am

All airplanes of this type will have inlets and exhaust. They just hide them better on newer planes. On the 737, the inlets are below the root of the wing, on the fuselage side, on the 757, they are on the bottom. I dont even remember where on the 747. On the dc-9 series, you will see a hole at the base of the vertical stabilizer. That is the ram inlet for both a/c systems on that model..JT
 
Mr Spaceman
Topic Author
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

RE: JT-8D

Wed May 23, 2001 5:22 am

Thanks for the info JT-8D. Wow! I was actually on the right track about the Intakes being part of the Air Conditioning system. I wasn't sure though, because I was wondering about the lack of airflow into the scoops while the aircraft was sitting in a line of jets on a taxi-way, on a hot day.

Chris
"Just a minute while I re-invent myself"
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 5:30 am

The air entering the inlets on the air cycle sytems is not entering the cabin, it is just the cooling medium for cooling the engine bleed air that is used for in the cabin.
 
JT-8D
Posts: 423
Joined: Sun Dec 31, 2000 11:34 pm

RE: JT-8D

Wed May 23, 2001 5:32 am

You had another good thought. The air is forced through the heat exchangers by electric fans on older planes (727, dc-9, maybe even 717 too). Newer use an air driven fan, called a turbofan. Any time the airconditioning package (known as a pack) is on, the air runs the turbofan at the same time. Interesting note: the old dc-8 used turbofans also, but with the old freon a/c system. Later a/c used the electric fans, then back to the turbofans on the newer planes. 757 uses a fan attached to the acm (air cyle machine) so they combined a few components as well. The new 737 does this too, I think, but Im not sure..Jt
 
JT-8D
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Joined: Sun Dec 31, 2000 11:34 pm

RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 6:42 am

On the old freon systems, the air did enter the cabin, after being compressed in the turbocompressor. On more modern planes, it is used to cool the heat exchangers only..JT
 
Mr Spaceman
Topic Author
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

RE: B-747 Ram Air Inlet Location.

Wed May 23, 2001 6:42 am

Hi guys. Well, thanks for explaining to me how the Air Conditioning system on an Airliner Jet "basically" works. Now when I'm watching them, I will know what those Air Inlets are for.

JT-8D, I did a quick photo search of the B-747, and I'm sure that the location of the Ram Air inlets are the Triangle shaped intakes that you can see on the wing root's front fairing in this photo.


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Photo © Andrew Hunt




Chris
"Just a minute while I re-invent myself"
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 6:48 am

The DC10, Airbus a/c & 747 uses a fan driven by the ACM. The fan is only required when there is low ram air flow.
 
JT-8D
Posts: 423
Joined: Sun Dec 31, 2000 11:34 pm

RE: B-747 Ram Air Inlet Location.

Wed May 23, 2001 6:51 am

Your right space. I havnt worked on aircon on a 747 in about 10 yrs. Last thing I did was figure out why the capt power seat didnt work. And that was 6 yrs ago. Its so easy to forget--lol..JT
 
dc10hound
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RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 8:10 am

The Pack fans are primarily used during periods of low flow, i.e.,on the ground or on approach.
"Eagles soar. But weasels never get sucked into jet intakes.."
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 9:03 am

Dc10hound

That's what I said wasn't it ?
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: DC-8, DC-10, L-1011 Nose "Air Intake"?

Wed May 23, 2001 11:23 am

The inlets on the front of the DC8 are for the 4 turbocompressors used to pressurixe the cabin.

The top and bottom inlets visible in the bifurcated inlet feed the turbocompressors. The upper turbocompressor access door is visible just aft of the inlet.

The bleed air from the engines which is used to spin the turbocompressors exhausts overboard from the vent located on the side of the fusealge just aft of the access door. The bottom TC exhaust is just foward of the hose connection.

The area in between the two TC's in the bifurcated duct feeds heat exhangers to cool the compressed air from the TC's.

The only planes to my knowledge that used TC's for pressurization are the 707 and the DC8.

The TC's on the DC8 were extremely noisy in the cockpit, and had a tendency to have uncontained failures which scared the shit out of you as the pieces had a tendency to rip into the cockpit on occasion.

To find the condition of a TC on the preflight one only had to look at the TC exhaust duct and find how much oil from the bearing case had leaked past the seal and run all over the fuselage. I never saw a TC that didn't leak.

They also made strange noises notifying you of their impending doom.

Most of the TC's were replaced with the NASI system on aircraft not receiving the 70 series conversion which did away with the TC and used direct bleed air from the engines.

Plugs were installed in the TC ducts but left the heat exchanger duct open.

These ducts are in no relation to the DC10, or L1011 inlets as they had no TC's.

Here is a photo of the plugs blocking the TC inlets on an Emery 71.


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Photo © Andy Martin



The scoops on the L1011 and the DC10 are for PACK cooling.

JET

 
dc10hound
Posts: 460
Joined: Fri Dec 15, 2000 4:18 pm

RE: DC-8, DC-10, L-1011 Nose

Thu May 24, 2001 5:47 am

VC-10
Yes it is, I was just agreeing with you.  Yeah sure
Actually, I must of skipped over your post when I entered mine. Sorry.
"Eagles soar. But weasels never get sucked into jet intakes.."

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