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What Are These Openings On The Belly Of The 757  
User currently offlinec5load From United States of America, joined Sep 2008, 917 posts, RR: 0
Posted (4 years 5 months 2 weeks 17 hours ago) and read 7037 times:

What are the two small doors on each side of the red beacon strobe on the belly of this a/c? If these were APU inlet doors, wouldn't they be closed prior to taking off?


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Photo © Adam Wright




"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
35 replies: All unread, showing first 25:
 
User currently offlineMaverick623 From United States of America, joined Nov 2006, 5592 posts, RR: 6
Reply 1, posted (4 years 5 months 2 weeks 16 hours ago) and read 7003 times:

Quoting c5load (Thread starter):
What are the two small doors on each side of the red beacon strobe on the belly of this a/c?

Bleed air pack exhausts. They're very nice to stand under on cold days.

Quoting c5load (Thread starter):
If these were APU inlet doors, wouldn't they be closed prior to taking off?

The APU inlet door is just below the right side of the vertical stabilizer (facing forward), and if you look closely you can see that it too is open.

The door only closes when the APU is not running.



"PHX is Phoenix, PDX is the other city" -777Way
User currently offlinejetlagged From United Kingdom, joined Jan 2005, 2546 posts, RR: 24
Reply 2, posted (4 years 5 months 2 weeks 16 hours ago) and read 6968 times:

Quoting Maverick623 (Reply 1):
Bleed air pack exhausts

The packs themselves "exhaust" into the cabin and so bleed air isn't dumped directly overboard. The ram air system which cools the packs has external exhausts though.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineCanadianNorth From Canada, joined Aug 2002, 3389 posts, RR: 9
Reply 3, posted (4 years 5 months 2 weeks 15 hours ago) and read 6947 times:

Looks like the air conditioning pack exhaust louvres to me as well (at least thats what they are called on the 737, I don't have any 757 experience but I would think it's reasonably similar.)

As said on pretty much every modern jetliner I can think of the APU inlet door can be found up near the empenage.


CanadianNorth



What could possibly go wrong?
User currently offlineMir From United States of America, joined Jan 2004, 21554 posts, RR: 55
Reply 4, posted (4 years 5 months 2 weeks 15 hours ago) and read 6944 times:

Quoting c5load (Thread starter):
If these were APU inlet doors, wouldn't they be closed prior to taking off?

Only if the APU wasn't running. If the APU is running, it needs to get air somehow, and that means an open inlet door.

But, as has already been mentioned, they are related to the bleed air system and the packs, not the APU.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineDL_Mech From United States of America, joined Feb 2000, 1933 posts, RR: 9
Reply 5, posted (4 years 5 months 2 weeks 13 hours ago) and read 6790 times:

Here's a good view of the APU inlet on this now scrapped aircraft....


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Photo © Agustin Anaya




This plane is built to withstand anything... except a bad pilot.
User currently offlinec5load From United States of America, joined Sep 2008, 917 posts, RR: 0
Reply 6, posted (4 years 5 months 2 weeks 12 hours ago) and read 6755 times:

Quoting Mir (Reply 4):
Only if the APU wasn't running. If the APU is running, it needs to get air somehow, and that means an open inlet door

You guys don't turn the APU off once engines are started? Isn't that kind of a waste of fuel? Once the engines are going, they will provide all the bleed air and a/c systems.



"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
User currently offlineflybaurLAX From United States of America, joined Oct 2008, 638 posts, RR: 0
Reply 7, posted (4 years 5 months 2 weeks 11 hours ago) and read 6725 times:

Quoting c5load (Reply 6):
You guys don't turn the APU off once engines are started? Isn't that kind of a waste of fuel? Once the engines are going, they will provide all the bleed air and a/c systems.

Most of the time they will turn the APU off during taxi, but some flights, such as ETOPS flights require the APU to be on until the aircraft are within a certain distance of their destination, or suitable alternates.



Boilerup! Go Purdue!
User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 8, posted (4 years 5 months 2 weeks 10 hours ago) and read 6700 times:

Quoting jetlagged (Reply 2):
Quoting Maverick623 (Reply 1):
Bleed air pack exhausts

The packs themselves "exhaust" into the cabin and so bleed air isn't dumped directly overboard. The ram air system which cools the packs has external exhausts though.

Indeed, the photo shows the AC pack cooling exhausts open (or nearly so) quite clearly.

Quoting c5load (Reply 6):
You guys don't turn the APU off once engines are started? Isn't that kind of a waste of fuel? Once the engines are going, they will provide all the bleed air and a/c systems.

Normally yes, however some MEL items require it to remain running throughout the flight (engine driven generator inop, for instance). If the APU is running, it's running for a reason.

Quoting flybaurLAX (Reply 7):
Quoting c5load (Reply 6):
You guys don't turn the APU off once engines are started? Isn't that kind of a waste of fuel? Once the engines are going, they will provide all the bleed air and a/c systems.


Most of the time they will turn the APU off during taxi, but some flights, such as ETOPS flights require the APU to be on until the aircraft are within a certain distance of their destination, or suitable alternates.

There are indeed times when the APU is required in flight, but we do not have to have the APU running during an ETOPS flight; it must be operational and available on ETOPS flights on the 757/767 however, and there is a program for starting the APUs in flight to test their cold-soaked starting capability in most ETOPS programs I have seen. As a very minor caveat, I have been told that at least one carrier has ETOPS 120 with the APU inop on the 767, but I have never seen that in print. If someone knows about that I'd be interested. I can definitively say that we don't keep the APU running across the ocean on ETOPS segments, however.


User currently offlinec5load From United States of America, joined Sep 2008, 917 posts, RR: 0
Reply 9, posted (4 years 5 months 2 weeks 10 hours ago) and read 6694 times:

Quoting PGNCS (Reply 8):
Normally yes, however some MEL items require it to remain running throughout the flight

So the APU inlet door I see in the photo above can withstand the air during flight? I would think it'd rip right off.



"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 10, posted (4 years 5 months 2 weeks 10 hours ago) and read 6692 times:

Quoting c5load (Reply 9):
Quoting PGNCS (Reply 8):
Normally yes, however some MEL items require it to remain running throughout the flight

So the APU inlet door I see in the photo above can withstand the air during flight? I would think it'd rip right off.

Yes it can.


User currently offlineMender From United Kingdom, joined Feb 2004, 240 posts, RR: 0
Reply 11, posted (4 years 5 months 2 weeks 10 hours ago) and read 6666 times:

Quoting c5load (Reply 6):
You guys don't turn the APU off once engines are started?

I can't tell from that picture if the aircraft is taking off or landing.

The flaps/slats appear to be configured for take off so maybe the aircraft has pushed back from the stand and is about to turn off the APU but it could have also just landed and the pilot has just turned on the APU and he is in the process of retracting the flaps and slat. I just can't tell.


User currently offlinestratosphere From United States of America, joined Sep 2007, 1651 posts, RR: 4
Reply 12, posted (4 years 5 months 2 weeks 6 hours ago) and read 6495 times:

Quoting PGNCS (Reply 8):
I have been told that at least one carrier has ETOPS 120 with the APU inop on the 767, but I have never seen that in print. If someone knows about that I'd be interested. I can definitively say that we don't keep the APU running across the ocean on ETOPS segments, however.

FX actually has a 180 ETOPS with an APU inop. They run their 777's ETOPS 207.



NWA THE TRUE EVIL EMPIRE
User currently offlineMax Q From United States of America, joined May 2001, 4437 posts, RR: 19
Reply 13, posted (4 years 5 months 2 weeks 6 hours ago) and read 6494 times:

Quoting flybaurLAX (Reply 7):
Most of the time they will turn the APU off during taxi, but some flights, such as ETOPS flights require the APU to be on until the aircraft are within a certain distance of their destination, or suitable alternates.

That is not the case. Unlike lesser Aircraft (737) the 757 has more than adequate redundancy to provide for ETOPS 180 without needing the APU to be running most of the flight !



The best contribution to safety is a competent Pilot.
User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 14, posted (4 years 5 months 2 weeks 5 hours ago) and read 6468 times:

Quoting stratosphere (Reply 12):
Quoting PGNCS (Reply 8):
I have been told that at least one carrier has ETOPS 120 with the APU inop on the 767, but I have never seen that in print. If someone knows about that I'd be interested. I can definitively say that we don't keep the APU running across the ocean on ETOPS segments, however.

FX actually has a 180 ETOPS with an APU inop. They run their 777's ETOPS 207.

On the 757? I'm not doubting you, I was just restricting my answers to 757/767 aircraft.


User currently offlineMir From United States of America, joined Jan 2004, 21554 posts, RR: 55
Reply 15, posted (4 years 5 months 2 weeks 5 hours ago) and read 6456 times:

Quoting c5load (Reply 6):
You guys don't turn the APU off once engines are started? Isn't that kind of a waste of fuel? Once the engines are going, they will provide all the bleed air and a/c systems.

Normal ops for most operators is to have the APU off once both engines are running. But there are a variety of situations where you'd want it on, so leaving it running for takeoff is hardly uncommon.

Quoting c5load (Reply 9):
So the APU inlet door I see in the photo above can withstand the air during flight? I would think it'd rip right off.

It can withstand it, yes. On some aircraft you may see an airspeed limitation when the door is open, but it's high enough that it doesn't really affect things too badly.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlinestratosphere From United States of America, joined Sep 2007, 1651 posts, RR: 4
Reply 16, posted (4 years 5 months 2 weeks 5 hours ago) and read 6454 times:

Quoting PGNCS (Reply 14):
On the 757? I'm not doubting you, I was just restricting my answers to 757/767 aircraft.

The only ETOPS A/C at FX are 777's...Sorry if this was only a 757/767 comparision

[Edited 2010-03-10 21:10:38]


NWA THE TRUE EVIL EMPIRE
User currently offlineflybaurLAX From United States of America, joined Oct 2008, 638 posts, RR: 0
Reply 17, posted (4 years 5 months 1 week 6 days 17 hours ago) and read 6297 times:

Quoting Max Q (Reply 13):

That is not the case. Unlike lesser Aircraft (737) the 757 has more than adequate redundancy to provide for ETOPS 180 without needing the APU to be running most of the flight !

I meant to specify for the 737. I only know about ETOPS requirements for AS 737s, as I sat in on an ETOPS class, but I know it varies from each carrier as to what the FAA requires.



Boilerup! Go Purdue!
User currently offlineHAWK21M From India, joined Jan 2001, 31676 posts, RR: 56
Reply 18, posted (4 years 5 months 1 week 6 days 16 hours ago) and read 6276 times:

Quoting Maverick623 (Reply 1):
The APU inlet door is just below the right side of the vertical stabilizer (facing forward), and if you look closely you can see that it too is open.

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Photo © Søren Geertsen


A Door on the RH Empennage side of the Vertical stablizer root.When closed its flush with the fuselage.

Quoting Maverick623 (Reply 1):

Bleed air pack exhausts.

Ram air Exhaust Louvers.

Quoting c5load (Reply 6):

You guys don't turn the APU off once engines are started? Isn't that kind of a waste of fuel? Once the engines are going, they will provide all the bleed air and a/c systems.

Depending on company SOP.The APU is also a extra source of Pneumatics & Electricals.

Quoting c5load (Reply 9):
So the APU inlet door I see in the photo above can withstand the air during flight? I would think it'd rip right off.

It can.....Also APU Pneumatics have height restrictions.

regds
MEL.

[Edited 2010-03-11 09:54:24]


Think of the brighter side!
User currently offlineFX772LRF From United States of America, joined Apr 2009, 675 posts, RR: 12
Reply 19, posted (4 years 5 months 1 week 6 days 12 hours ago) and read 6178 times:

There's also a takeoff method used by some pilots called the "bleeds off" method - they use the air from the APU for pressurization instead of engine bleed air, which lets the engines use their full power for takeoff. It's used in situations such as overloaded. Not completely sure if the 757 is capable of such a thing. I know that the A319 is capable of such a thing.

I actually learned this from one of HAL's trip reports when he was at American West. Good read from a trip report and a Tech/Ops standpoint.

America West Pilot Trip Report #5 (Pics) (by HAL Feb 11 2006 in Trip Reports)
Around the area of the departure from LAS to FLL.

-Noah  wave 

[Edited 2010-03-11 13:52:33]


Cleared to IAH via CLL 076 radial/BAZBL/RIICE3, up to 3k, 7k in 10, departure on 134.3, squawk 4676, Colgan 9581.
User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 20, posted (4 years 5 months 1 week 6 days 12 hours ago) and read 6166 times:

Quoting stratosphere (Reply 16):
Quoting PGNCS (Reply 14):
On the 757? I'm not doubting you, I was just restricting my answers to 757/767 aircraft.

The only ETOPS A/C at FX are 777's...Sorry if this was only a 757/767 comparision

No don't apologize! I am glad for the info; I am pretty familiar with 757/767 ETOPS at several carriers, and did it a lot myself in the past. I was just wanting to clarify what airplane we were talking about. Thanks for the information!  


User currently offlinePGNCS From United States of America, joined Apr 2007, 2821 posts, RR: 45
Reply 21, posted (4 years 5 months 1 week 6 days 12 hours ago) and read 6158 times:

Quoting Mir (Reply 15):
Quoting c5load (Reply 9):
So the APU inlet door I see in the photo above can withstand the air during flight? I would think it'd rip right off.

It can withstand it, yes. On some aircraft you may see an airspeed limitation when the door is open, but it's high enough that it doesn't really affect things too badly.

And on other aircraft the APU is not available in flight at all (e.g. B-744, B-727), but 757/767's all have APUs capable of inflight operation.


User currently offlineHAWK21M From India, joined Jan 2001, 31676 posts, RR: 56
Reply 22, posted (4 years 5 months 1 week 6 days 4 hours ago) and read 6028 times:

Quoting jetlagged, reply=2] cotizando Maverick623 (contestaci
[quote=PGNCS
(Reply 21):
but 757/767's all have APUs capable of inflight operation.

On the B757s.....Pneumatic usage height restrictions exist.
regds
MEL.



Think of the brighter side!
User currently offlineAirPortugal310 From Palau, joined Apr 2004, 3608 posts, RR: 2
Reply 23, posted (4 years 5 months 1 week 5 days 17 hours ago) and read 5939 times:

Quoting FX772LRF (Reply 19):
It's used in situations such as overloaded

Not too be technical or anything, but I doubt anyone is taking off overloaded. At max weight perhaps?



I sell airplanes and airplane accessories
User currently offlineFX772LRF From United States of America, joined Apr 2009, 675 posts, RR: 12
Reply 24, posted (4 years 5 months 1 week 5 days 13 hours ago) and read 5893 times:

Quoting AirPortugal310 (Reply 23):
Not too be technical or anything, but I doubt anyone is taking off overloaded. At max weight perhaps?

Yes, that's what I meant. I was thinking along the lines of overloaded for typical takeoff thrust configurations.

Thanks for that.  

-Noah   



Cleared to IAH via CLL 076 radial/BAZBL/RIICE3, up to 3k, 7k in 10, departure on 134.3, squawk 4676, Colgan 9581.
25 PGNCS : True.
26 XFSUgimpLB41X : In most situations we use just a "packs off" takeoff if we need a bit of extra performance out of the engines with a wider temperature margin. The ca
27 Post contains images FlyASAGuy2005 : I may be way off but is this sort of the reason why the CR2 takes off with the APU running (if it's even working )
28 XFSUgimpLB41X : The 14th stage bleeds (used for anti-ice and thrust reverse) are always open on the CRJ-200, but not necessarily drawn. The 10th stage are used for a
29 DC8FriendShip : There are shutoff valves for 14th stage same as tenth stage. Remember, T/R's won't work on a 200 if 14th stage is turned off.
30 Post contains links and images 787luvr : I don't mean to veer off topic or hijack the thread but.. If you take a look at the first photo of the 787 on the far right you can see what I assume
31 Post contains images XFSUgimpLB41X : That's what I meant when I said the valves are always selected open but not necessarily utilized.
32 tdscanuck : It's not an exhaust port, it's a FOD deflector. That's the cabin air compressor inlet; the door prevents FOD from getting sucked in when you're on th
33 FlyASAGuy2005 : Are there any non mock-up photos of the Dreamliner flightdeck?
34 Post contains images 787luvr : Thanks Tom! That never even crossed my mind...
35 Post contains links tdscanuck : There were some non-mockup shots from a 777 customer that got a tour in Everett that got linked from a.net a few days ago, but they got taken down. I
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