falcon20driver
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737 no bleeds takeoff
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Boy, you're going to get some infantile responses to that one! Allow me to be the first!falcon20driver
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Thought that might get a couple laughs, the method is squeeze, spread, squeeze. You are opening both packs and have the isolation valve closed and the APU bleed on, but one of the instructors taught a different way, he gave an example of a 737 crew that had a pressurization problem after takeoff using the squeeze, spread, squeeze method.
I can't remember what the other method was, it had to do with going around the panel in the shape of a C, I think it might have been leaving the iso valve in auto and the rest of it the same, when you turn the engine bleeds on you have to make sure you get the APU bleed off before turning the #1 engine bleed on in order to not violate the law of the packs, I'm not sure if that's it or not.
Any help from 737 pilots would be appreciated.
I can't remember what the other method was, it had to do with going around the panel in the shape of a C, I think it might have been leaving the iso valve in auto and the rest of it the same, when you turn the engine bleeds on you have to make sure you get the APU bleed off before turning the #1 engine bleed on in order to not violate the law of the packs, I'm not sure if that's it or not.
Any help from 737 pilots would be appreciated.
Bleeds off
[/QUOTE]I can't remember what the other method was, it had to do with going around the panel in the shape of a C, I think it might have been leaving the iso valve in auto and the rest of it the same, when you turn the engine bleeds on you have to make sure you get the APU bleed off before turning the #1 engine bleed on in order to not violate the law of the packs, I'm not sure if that's it or not.
Any help from 737 pilots would be appreciated.[/QUOTE]
The "squeeze-spread-squeeze" is how the switches look when they are configured. When doing a bleeds-off take-off, you start at the #2 pack and leave it in auto - then work around in a "C" shape... Iso valve OFF, left pack auto, left bleed - OFF APU ON right bleed off. When reconfiguring after take-off you just do it in a reverse "C". (Start with the #2 engine bleed on - APU off and so on. This prevents accidently causing a dual bleed situation.
R8J
[/QUOTE]I can't remember what the other method was, it had to do with going around the panel in the shape of a C, I think it might have been leaving the iso valve in auto and the rest of it the same, when you turn the engine bleeds on you have to make sure you get the APU bleed off before turning the #1 engine bleed on in order to not violate the law of the packs, I'm not sure if that's it or not.
Any help from 737 pilots would be appreciated.[/QUOTE]
The "squeeze-spread-squeeze" is how the switches look when they are configured. When doing a bleeds-off take-off, you start at the #2 pack and leave it in auto - then work around in a "C" shape... Iso valve OFF, left pack auto, left bleed - OFF APU ON right bleed off. When reconfiguring after take-off you just do it in a reverse "C". (Start with the #2 engine bleed on - APU off and so on. This prevents accidently causing a dual bleed situation.
R8J
falcon20driver
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falcon20driver
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I'm guessing that if you use the squeze - spread - squeze method on the -200 and after takeoff you missed getting the engine bleeds on, and than the left pack trips with the Iso valve closed you will not pressurize, I can't remember if you leave the Iso valve in auto and the pack trips if the Iso valve will automatically open to allow APU air to the right pack, that's all I can figure, I'm not sure if it works that way or not.
That was the scenerio the Instructor talked about, a crew didn't get the engine bleeds on and got to 10,000 or whatever set the masks off and the pax got a surprise.
That was the scenerio the Instructor talked about, a crew didn't get the engine bleeds on and got to 10,000 or whatever set the masks off and the pax got a surprise.
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falcon20driver
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Set like that the APU will not pressurize the plane.Launchpad said:
Here is a picture of a -200 overhead if that helps http://www.airliners.net/open.file/341991/L/
I'm going to have to call that IP at HPA, this is bugging me, I should of took better notes.
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falcon20driver
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falcon20driver
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HI ,
I'm a 737-200,300 instructor, so here goes a try:
The "squeeze-spread-squeeze" phrase was coined on the 200, which as correctly noted earlier, has only two positions on the pack switchs, not three as on the 300. The phrase speaks only about the switchs proper position for a bleeds-off takeoff, NOT the correct order in which to get them there. Trouble is possible if using "s-s-s" as methodolgy for setting the switchs. The proper procedure for setting the switchs in the correct order is the "C" before take-off and the "reverse C" after acceleration altitude and climb power being set (to keep mandatory take-off power through segment three).
Done properly after takeoff, not only does the one bleed/one pack rule remain unviolated, it also checks the APU bleed and isolation valves by monitoring the manifold pressure gauge and confirming: 1- positive R pressure after turning the #2 engine bleed on, 2- the L goes to zero after turning the APU bleed off, and 3-noting the L rise when turning the #1 engine bleed on.
Hope that helps a little...
I'm a 737-200,300 instructor, so here goes a try:
The "squeeze-spread-squeeze" phrase was coined on the 200, which as correctly noted earlier, has only two positions on the pack switchs, not three as on the 300. The phrase speaks only about the switchs proper position for a bleeds-off takeoff, NOT the correct order in which to get them there. Trouble is possible if using "s-s-s" as methodolgy for setting the switchs. The proper procedure for setting the switchs in the correct order is the "C" before take-off and the "reverse C" after acceleration altitude and climb power being set (to keep mandatory take-off power through segment three).
Done properly after takeoff, not only does the one bleed/one pack rule remain unviolated, it also checks the APU bleed and isolation valves by monitoring the manifold pressure gauge and confirming: 1- positive R pressure after turning the #2 engine bleed on, 2- the L goes to zero after turning the APU bleed off, and 3-noting the L rise when turning the #1 engine bleed on.
Hope that helps a little...
falcon20driver
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I understand the squeze-spread-squeze method, but one the instructors at HPA recommended using a different method, and this is what I am trying to remember, I think it's the same except you set the Iso valve to auto instead of closed.
The reason he was teaching the method is because of an incident a 737-200 crew had where for some reason they didn't get the panel reconfigured and left the engine bleeds off, and I believe it was a pack trip on the left and with the Iso valve closed the plane stopped pressurizing, and they didn't realize this until the masks fell into the pax laps.
I don't have my 737 manuals right now to research so I might have this wrong, but I believe he said that if the Iso valve would have been in the auto position that it would have opened when the pack tripped and the plane would never of lost pressure.
Does that sound right to you, or do I have it all wrong?
The reason he was teaching the method is because of an incident a 737-200 crew had where for some reason they didn't get the panel reconfigured and left the engine bleeds off, and I believe it was a pack trip on the left and with the Iso valve closed the plane stopped pressurizing, and they didn't realize this until the masks fell into the pax laps.
I don't have my 737 manuals right now to research so I might have this wrong, but I believe he said that if the Iso valve would have been in the auto position that it would have opened when the pack tripped and the plane would never of lost pressure.
Does that sound right to you, or do I have it all wrong?
AK737FO
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You got it right
You guys got it right. Squeeze-Spread-Squeeze or the "C" followed by "reverse C" gives you the same thing.
After start, configure to - R pack on, Iso closed, L pack on, #1 bleed off, APU bleed on, #2 bleed off. SSS or C, which ever you prefer.
After the Flaps 1, climb power, establish the bleeds call, do the reverse C.
#2 bleed on, pause and let the duct pressure come up, APU bleed off, #1 bleed on, Iso to Auto - and away you go.
Remember the "4 corners" or "The bed post"? When the Iso valve is in auto, if you put any of the 4 corner switches (bed posts) to off, the iso valve will open. So, while the iso valve is switched to closed, it will not open (duh) and you will not be using the APU to feed two packs. The APU will only feed the Left pack.
Our limititations section allows APU bleed air to 17,000. Never tried it, so I don't know what kind of cabin you will have up there. Now, we have a whole different proceedure for an unpressurized take off (APU inop and bleeds off needed for takeoff). Maybe that is what your instructor was talking about?
We do not use the APU to run two packs for cooling, but we do use the APU to run two packs for heating on the ground in the winter. It is a little difficult to keep the cabin warm in Barrow in January. To run both packs off the APU (again - on the ground for heat when it is nasty cold) just open the Iso valve. We also close the out flow valve to keep the water tank from freezing. That can be done two ways - manually close it, but make sure to keep it open just a crack to you don't pressurize if someone closed the doors, or just put the flight/ground switch to flight. Make sure to go back to ground before the doors are closed or your ears will feel a bump.
AK737FO
You guys got it right. Squeeze-Spread-Squeeze or the "C" followed by "reverse C" gives you the same thing.
After start, configure to - R pack on, Iso closed, L pack on, #1 bleed off, APU bleed on, #2 bleed off. SSS or C, which ever you prefer.
After the Flaps 1, climb power, establish the bleeds call, do the reverse C.
#2 bleed on, pause and let the duct pressure come up, APU bleed off, #1 bleed on, Iso to Auto - and away you go.
Remember the "4 corners" or "The bed post"? When the Iso valve is in auto, if you put any of the 4 corner switches (bed posts) to off, the iso valve will open. So, while the iso valve is switched to closed, it will not open (duh) and you will not be using the APU to feed two packs. The APU will only feed the Left pack.
Our limititations section allows APU bleed air to 17,000. Never tried it, so I don't know what kind of cabin you will have up there. Now, we have a whole different proceedure for an unpressurized take off (APU inop and bleeds off needed for takeoff). Maybe that is what your instructor was talking about?
We do not use the APU to run two packs for cooling, but we do use the APU to run two packs for heating on the ground in the winter. It is a little difficult to keep the cabin warm in Barrow in January. To run both packs off the APU (again - on the ground for heat when it is nasty cold) just open the Iso valve. We also close the out flow valve to keep the water tank from freezing. That can be done two ways - manually close it, but make sure to keep it open just a crack to you don't pressurize if someone closed the doors, or just put the flight/ground switch to flight. Make sure to go back to ground before the doors are closed or your ears will feel a bump.
AK737FO
falcon20,
I'm not sure what scenario your instructor was speaking of, but all the info you need to operate this system correctly has been discussed here. Just remember with the Isolation valve switch in auto,the valve position is determined by the POSITION of the "four-corner-switchs", NOT the position of valves the switchs control (ie. - a pack trip occurs, closing the pack SOV, but the switch is still on, ergo the isolation valve remains closed).
Great to see a discussion on something other than PFT or LCCs.
I'm not sure what scenario your instructor was speaking of, but all the info you need to operate this system correctly has been discussed here. Just remember with the Isolation valve switch in auto,the valve position is determined by the POSITION of the "four-corner-switchs", NOT the position of valves the switchs control (ie. - a pack trip occurs, closing the pack SOV, but the switch is still on, ergo the isolation valve remains closed).
Great to see a discussion on something other than PFT or LCCs.
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