Mr Spaceman From Canada, joined Mar 2001, 2786 posts, RR: 9 Posted (12 years 6 months 3 weeks 1 hour ago) and read 6047 times:
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.
JT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3 Reply 1, posted (12 years 6 months 3 weeks 1 hour ago) and read 5954 times:
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 From United States of America, joined Dec 2000, 423 posts, RR: 3 Reply 2, posted (12 years 6 months 3 weeks ago) and read 5944 times:
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 From Canada, joined Mar 2001, 2786 posts, RR: 9 Reply 3, posted (12 years 6 months 3 weeks ago) and read 5929 times:
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.
JT-8D From United States of America, joined Dec 2000, 423 posts, RR: 3 Reply 5, posted (12 years 6 months 3 weeks ago) and read 5917 times:
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
JETPILOT From United States of America, joined May 1999, 3130 posts, RR: 30 Reply 12, posted (12 years 6 months 2 weeks 6 days 18 hours ago) and read 5938 times:
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.