B737 classic QUESTIONS AFTER RECURRENT TRAINING
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I am remembering back 20 years or so since I first did the 737-200 course but my recollection was that the rear outflow valve modulates to smoothly control the cabin presssure whereas the forward valve is either open or closed, as indicated by the light
On descent if the forward valve was open then the rear valve would be modulating pretty much at the closed position due to the reduced airflow at idle power which would give surges on the cabin altitude.
The forward valve therefore fully closes on descent as the throttles close and the rear valve opens to a more central position to give better control. The forward hold may get some heat from the electrics but their is no airlfow through the hold.
I think that is why on the -200 Big airways used the rear hold for freight with legs, but as I say it was a long time ago, and I think it may have been different on the 400 series and later.
On descent if the forward valve was open then the rear valve would be modulating pretty much at the closed position due to the reduced airflow at idle power which would give surges on the cabin altitude.
The forward valve therefore fully closes on descent as the throttles close and the rear valve opens to a more central position to give better control. The forward hold may get some heat from the electrics but their is no airlfow through the hold.
I think that is why on the -200 Big airways used the rear hold for freight with legs, but as I say it was a long time ago, and I think it may have been different on the 400 series and later.
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Hi Centaurus,
QRH speeds depend on density altitude and actual weight, plus runway slope and wind corrections. I don't get the point of your question. Maybe you are talking about QRH speeds and Runway tables speeds, that only depend on actual or assumed OAT. If you consider a very light B733 such as a ferry flight or a test flight you will get very low QRH speeds, probably V1mcg, a small Vr and a small V2. If you check your runway tables for you actual OAT (full takeoff thrust let's say) you will get much higher values. But you will also see that these speeds are calculated for the performance limited weight taken into account, that can be a field limit, obstacle, etc.. this weight will be obviously much higher than you actual TOW. So why using speeds that are calculated for a much higher weight and that do not consider density altitude ?
QRH speeds depend on density altitude and actual weight, plus runway slope and wind corrections. I don't get the point of your question. Maybe you are talking about QRH speeds and Runway tables speeds, that only depend on actual or assumed OAT. If you consider a very light B733 such as a ferry flight or a test flight you will get very low QRH speeds, probably V1mcg, a small Vr and a small V2. If you check your runway tables for you actual OAT (full takeoff thrust let's say) you will get much higher values. But you will also see that these speeds are calculated for the performance limited weight taken into account, that can be a field limit, obstacle, etc.. this weight will be obviously much higher than you actual TOW. So why using speeds that are calculated for a much higher weight and that do not consider density altitude ?
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Gday Centaurus,
I have had this argument recently. I too beleive that it is incorrect to use the speeds associated with the actual OAT. You are in effect performing an "improved climb" take off with out the certified "imp clmb" data.
Further, certification data for the second segment is predicated at V2, which is entirely related to Vs, not assumed or actual OAT.
In my view, if you go rated thrust then you must use the speeds for the weight.
Any others care to comment??
Cheers,
Contract Con
P.s If it does say in the preamble in your RTOW, as written by the boffin that came up with all the numbers, to use the speeds for the actual OAT, then you may have no choice, regardless of opinion. The RTOW is an official certified doc. approved by your states regulator. If you go outside of what is written, you may end up in a sticky situation,in court with some smart ass lawyer, after it all goes bad one afternoon
I have had this argument recently. I too beleive that it is incorrect to use the speeds associated with the actual OAT. You are in effect performing an "improved climb" take off with out the certified "imp clmb" data.
Further, certification data for the second segment is predicated at V2, which is entirely related to Vs, not assumed or actual OAT.
In my view, if you go rated thrust then you must use the speeds for the weight.
Any others care to comment??
Cheers,
Contract Con
P.s If it does say in the preamble in your RTOW, as written by the boffin that came up with all the numbers, to use the speeds for the actual OAT, then you may have no choice, regardless of opinion. The RTOW is an official certified doc. approved by your states regulator. If you go outside of what is written, you may end up in a sticky situation,in court with some smart ass lawyer, after it all goes bad one afternoon
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Centaurus...on myboeingfleet site there is a chapter called something like 'performance engineering training'..
There it says ,that you should use actual weight take-off speeds,even if you do reduce.The same that you said.
The V1 will be much lower,sometimes more than 10 kts,for low weights when you do a reduce take-off.
I had the same argument with an engineer,and I had to ask around.
The engineer told me that the inertia will be smaller with lower weight,but I also told him that the braking force will reduce with lower mass.....so 1 to 1
so,I take boeing word in this case:use actual weight speeds.It seems the normal thing to do.Use REDUCED power,with higher speeds (for higher than actual weights) ,this doesn't seem right.
maybe for some engineer,but let him answer in case of eventual overrun...with 20 kts higher V1.
There it says ,that you should use actual weight take-off speeds,even if you do reduce.The same that you said.
The V1 will be much lower,sometimes more than 10 kts,for low weights when you do a reduce take-off.
I had the same argument with an engineer,and I had to ask around.
The engineer told me that the inertia will be smaller with lower weight,but I also told him that the braking force will reduce with lower mass.....so 1 to 1
so,I take boeing word in this case:use actual weight speeds.It seems the normal thing to do.Use REDUCED power,with higher speeds (for higher than actual weights) ,this doesn't seem right.
maybe for some engineer,but let him answer in case of eventual overrun...with 20 kts higher V1.
Had a look at the B737-200ADV Boeing Flight Planning and Performance Manual (April 06, 2001) under the sub heading Takeoff Speeds, and it states:
"The speeds presented in the Takeoff Speeds table can be used for all performance conditions except where adjustments must be made to V1 for clearway, stopway, anti-skid inoperative, improved climb, contaminated runway situations, brake energy limits or tire speed limits. These speeds may be used for weights less than or equal to the performance limited weight".
On another subject: I recall once seeing a Boeing statement which I think came from a Boeing 737 Operators Symposium way back in the Eighties that said that a 10 knot decrease in VR equated to 7% less wear and tear on tyres due reduced tyre speed. Has anyone seen similar figures quoted elsewhere?
"The speeds presented in the Takeoff Speeds table can be used for all performance conditions except where adjustments must be made to V1 for clearway, stopway, anti-skid inoperative, improved climb, contaminated runway situations, brake energy limits or tire speed limits. These speeds may be used for weights less than or equal to the performance limited weight".
On another subject: I recall once seeing a Boeing statement which I think came from a Boeing 737 Operators Symposium way back in the Eighties that said that a 10 knot decrease in VR equated to 7% less wear and tear on tyres due reduced tyre speed. Has anyone seen similar figures quoted elsewhere?
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Hi Seat1APlease, the cargo holds are NOT supposed to be ventilated.
That's the only precaution we have against cargo fires, except on newer airplanes with smoke detectors.
Hi Chris, thanks a lot for the info, at last something official and useful
LEM
That's the only precaution we have against cargo fires, except on newer airplanes with smoke detectors.
Hi Chris, thanks a lot for the info, at last something official and useful
LEM
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I'll post this new question here:
Doing the EIS test (the one with a pen) some days ago, I had an "ERF" code on the fuel used display.
What does that mean????
Doing the EIS test (the one with a pen) some days ago, I had an "ERF" code on the fuel used display.
What does that mean????
LEM,
Full list of all the codes has been on http://www.b737.org.uk/powerplant.htm for a while.
You should know where to look for this stuff by now!
S&L
Full list of all the codes has been on http://www.b737.org.uk/powerplant.htm for a while.
You should know where to look for this stuff by now!
S&L
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new question
Anybody knows what does exactly indicates the red AUTOLAND warning light close to both recall panels in the Sabena 733 simulator in Bruxelles?
Thanks
Thanks
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Hi LEM,
this simulator is my home base simulator since 17 years now. Don't know "exactly" what the red light stands for, but it is some kind of NO CONTINUE autoland when the pilot is using the HUD (which in the mean is removed from the sim, but the red light is still there)
The light was installed for pilots from Aero Postale France
Pat
this simulator is my home base simulator since 17 years now. Don't know "exactly" what the red light stands for, but it is some kind of NO CONTINUE autoland when the pilot is using the HUD (which in the mean is removed from the sim, but the red light is still there)
The light was installed for pilots from Aero Postale France
Pat
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I received this additional information from an instructor at SFA :
This light is specific to French companies, especially Air france. It covers a certain warning, (illumination of those lights when the RA’s fails in dual ch appr, or loss of valid Loc or GS info…. This is a requirement from the DGAC and is only functioning when the sim is loaded in SEA version. Note that I saw exactly the same lights in Casablanca on RAM simulator….
This light is specific to French companies, especially Air france. It covers a certain warning, (illumination of those lights when the RA’s fails in dual ch appr, or loss of valid Loc or GS info…. This is a requirement from the DGAC and is only functioning when the sim is loaded in SEA version. Note that I saw exactly the same lights in Casablanca on RAM simulator….
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ANOTHER NEW QUESTION
Hi Guys, I've been demonstrated that what I thought was a glitch is instead part of the autobrake design:
If you taxi too fast, with the thrust levers at idle, and you reach 35 kts, the RTO will disarm.
I can't find any reference in the manuals, nor in the maintenance manual.
Did you know that?
If you taxi too fast, with the thrust levers at idle, and you reach 35 kts, the RTO will disarm.
I can't find any reference in the manuals, nor in the maintenance manual.
Did you know that?
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LEM
This is my understanding of RTO;
This is my understanding of RTO;
- Below 60 kts RTO remains armed when throttles retarded
- 60 to 90 kts RTO disarms when throttles retarded
- 90 kts and above RTO activated when throttles retarded
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That's what the book says.
That's what I knew.
But the 35 knots thing is absolutely true. Try it, on a long taxyway, light weight, thrust levers at idle.
This feature is not documented...
I wonder if some old chap knew that
That's what I knew.
But the 35 knots thing is absolutely true. Try it, on a long taxyway, light weight, thrust levers at idle.
This feature is not documented...
I wonder if some old chap knew that
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Hi,
4) Is it true the engine fire extinguisher does NOT reach the gearbox?
I think it is not true (just a guess). If the engine fire extinguisher does not reach the gearbox, why there are 4 overheat and fire detectors in the fan case (the gearbox is installed on the fan case)?
In addition the engine fire extinguisher ports are at the top, therefore the fire extinguisher will reach the gearbox (on the side of the fan case) which is no that far from the fire extinguisher ports. The fan cowls (when closed) will facilitate the fire extinction because they can keep or hold the fire extinguisher around the fan case. During engine run-up with fan cowls open, the presence of a ground fire extinguisher is required and necessary.
The gearbox contains oil and many accessories are installed on it: EDP, IDG fuel pump & HMU..... These components and their hoses still contain fuel, hydraulic, and oil which are flamable even tough the engine fire switch is pulled.
I have some questions regarding engine and APU fire:
-If there is one engine fire on trijet or quadjet, is the fire considered as emergency and the pilot must land ASAP?
-Is the APU fire considered as emergency, assuming the APU was operating at flight (for some raisons)?(on a twin, tri, or quad).
Feedback appreciated. Thank you.
Best regards.
4) Is it true the engine fire extinguisher does NOT reach the gearbox?
I think it is not true (just a guess). If the engine fire extinguisher does not reach the gearbox, why there are 4 overheat and fire detectors in the fan case (the gearbox is installed on the fan case)?
In addition the engine fire extinguisher ports are at the top, therefore the fire extinguisher will reach the gearbox (on the side of the fan case) which is no that far from the fire extinguisher ports. The fan cowls (when closed) will facilitate the fire extinction because they can keep or hold the fire extinguisher around the fan case. During engine run-up with fan cowls open, the presence of a ground fire extinguisher is required and necessary.
The gearbox contains oil and many accessories are installed on it: EDP, IDG fuel pump & HMU..... These components and their hoses still contain fuel, hydraulic, and oil which are flamable even tough the engine fire switch is pulled.
I have some questions regarding engine and APU fire:
-If there is one engine fire on trijet or quadjet, is the fire considered as emergency and the pilot must land ASAP?
-Is the APU fire considered as emergency, assuming the APU was operating at flight (for some raisons)?(on a twin, tri, or quad).
Feedback appreciated. Thank you.
Best regards.
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Originally Posted by LEM
But the 35 knots thing is absolutely true. Try it, on a long taxyway, light weight, thrust levers at idle.
The only light that illuminated was the blue CALL light from the cabin chief asking me why I was taxiing like a fool...
Now, is this a joke ? Is it a glitch in your fleet ? Can anyone else confirm this ?
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Hi all,
I had the Autobrake Disarm light quite a few times during taxi (on the 737 classic), last was 2 days ago at exactly 33 kts .
Aerotech : personnaly I would consider any kind of fire (engine, APU, cargo..),
in any kind of airplane as an serious emergency situation !!!!
From a previous post, you should always use vspeeds according to your actual TOW, even if doing a full thrust on a very light A/C out of a very long runway, unless applying a approved improved climb method . If the lowest weight on your RTOW is still much higher than your actual TOW use your QRH speeds (actaul OAT & actual TOW).
Bye........
I had the Autobrake Disarm light quite a few times during taxi (on the 737 classic), last was 2 days ago at exactly 33 kts .
Aerotech : personnaly I would consider any kind of fire (engine, APU, cargo..),
in any kind of airplane as an serious emergency situation !!!!
From a previous post, you should always use vspeeds according to your actual TOW, even if doing a full thrust on a very light A/C out of a very long runway, unless applying a approved improved climb method . If the lowest weight on your RTOW is still much higher than your actual TOW use your QRH speeds (actaul OAT & actual TOW).
Bye........