B737 classic QUESTIONS AFTER RECURRENT TRAINING

[LEM]

Hi all!

I've spent a few days on a recurrent training, and it's amazing as new questions always arise while talking to other people, even when you thought you knew something, maybe an instructor seems to be ABSOLUTELY convinced of what he's telling :rolleyes:

So here's a short list of questions, some are interesting details, some are close to rubbish, but when some people seem to be so sure, you wonder if the earth is flat or round...

Let's see who can score more points!



1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?

Aren't they all supposed to be 1.3 VS??



2) On the ground you notice a difference of 7° degrees between the two IRS headings.
Can the airplane be dispatched?


3) Why is there a dead band on the elevators cables, and not on the ailerons cables?



4) Is it true the engine fire extinguisher does NOT reach the gearbox?



5) Once for all: is it necessary or not to put the Standby Power switch to BAT in order to REALLY check if the Inverter is capable of producing current?



6) Why in the Brake cooling Schedule table in the QRH the upper right data are missing?

I mean: is it not possible to abort at 140 knots at 60 tons at an elevation of 2000ft?
Yes, me thinks!



7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).



8) If we lose the Battery Bus inflight, do the Pack valves remain open?



9) On airplanes that have a DCPCS, is it true there are THREE motors on the main outflow valve instead of two?



10) Discussing the ABORTED ENGINE START Recall Items, I've heard some people stating we do have to motor the engine after a shutdown due to NO OIL PRESSURE INDICATION by the time the engine is stabilized at idle!!!!
Can you believe that? :mad:



11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?



12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
I'm absolutely convinced NOT, but someone is absolutely convinced YES, so it's a lot of fun, you know...:mad:



13) Is the ignition spark more intense in the FLT position?
I don't think so. It's just activated on both igniters.
Or...



;)



LEM

[Cardinal]

Glad to see my airline isn't the only one full of oddities and pedantry :)

[Old Smokey]

LEM, an attempt at Questions 1 and 11, the others are about 6 aeroplane conversions in my past.

1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Vref is 1.3 Vs, Vls is 1.3 G (or 1.2 G in some jurisdictions)
Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
No, it will read correct Radio Altitude, the emission is over quite a large non-directional area, and will provide you a Radio Altitude for the first pulses to be returned to the aircraft. (A severely banked turn MAY give the results that you suggest).

Regards,

Old Smokey

[stator vane]

by doing the checklist, you may ruin a few bearings, but if you don't motor the engine and get the heat and fire out of there, you may melt quite a few blades and other components, not to mention the possible need to use the fire bottle soon thereafter.

more later, if i can remember those things

regarding your number 5-

how else would you check it, unless you came to a dark aircraft and started the APU etc?

if you come to the gate and it has ground power, and then start the APU whilst still with ground power, i think you will only have a few milli seconds between the switch over from ground power to APU power to check if the standby bus is working otherwise.

and then again, the old rule that never dies, you do what the man/woman with the ink pen and your checkride form says!

[Red Comet]

The dog will not freeze to death in the rear hold. (tried it)

[alexban]

Dog won't freeze ,the aft cargo hold is heated by air from the passanger cabin.It's not so warm as fwd cargo hold,which is heated directly by airflow from electronics..

13. in flt ,both igniters activated.The spark is the same,as far as I know.

2 From the DDPG the airplane can be dispatched under some conditions (day VMC,...) with only one IRS operative.
But ,I guess your question about difference between headings fits somewhere else.

7 Maybe it's night and I'm tired ,but Lem,where is the window heat off NNC?

4 The gearbox is placed on the 'outside' of the engine ,that's the reason for the particular shape of the 737 nacelle,and indeed the fire extinguisher does not reach the gearbox.

[Denti]

Regarding point 9), yes its true you have 3 DC motors at the outflow valve, one for each automatic controller (they're interchangeable) and a different one for manual mode.

[FCS Explorer]

4) Is it true the engine fire extinguisher does NOT reach the gearbox?

why should it?



7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).

g00d question. i dunno.




11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?

i -think- its built in fixed to the z-axis of the plane near the MLG.


12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
I'm absolutely convinced NOT, but someone is absolutely convinced YES, so it's a lot of fun, you know...

just put a bottle of water in a bag an see if it freezes - no, it doesn't.



13) Is the ignition spark more intense in the FLT position?
I don't think so. It's just activated on both igniters.
Or...

well, both spark plugs are now working instead of only one when in CONT

[LEM]

With the engine that I currently operate (RR Trent), the recommendation following aborted start due to no oil pressure is to still carry out a motoring cycle.

Hi Old Smokey!
This is taken from another thread, but applies to point 10) here.

Could you elaborate a bit?

I still find it hard to conceive such a procedure...:confused:

Thanks LEM

[Old Smokey]

Hi LEM,

The old thinking was that engine start was aborted if there was no oil pressure indication by light up. That part of the procedure still remains.

Previous thinking was to never operate an engine in ANY manner without oil pressure (one that I happily accepted). Current thinking is that the 'blow out' cycle is important, and, with roller bearings, little damage is likely to arise at the very low RPM. Allied with this, the torque supplied by the starter motor would in all likelyhood be insufficient to overcome excessive friction in an 'oilless environment', and would therefore be self regulating in protecting significant damage.

Personally, I don't like it too much, but there you go.

Regards,

Old Smokey

[despegue]

About the dog...

A captain in our airline tried it once on a flight to PMI... the dog came out severely undercooled and they had to put him to "eternal sleep"... So it is NOT heated enough to put any AVI in there. The heat from the pax. cabin is simply insufficient.
The forward cargo bay is the only one to put any live animals in.

Greetz,

Despegue

[BOAC]

A captain in our airline tried it once on a flight to PMI... the dog came out severely undercooled and they had to put him to "eternal sleep"... So it is NOT heated enough to put any AVI in there. The heat from the pax. cabin is simply insufficient.

Well, we ex DanAir's TRIED to tell BA this in 1992 (DA loaded front), but it is their 'procedure' to load AVI in the rear hold on the 737 - or at least was up until 2004 - and of course, we was WRONG 'cos we was 'charter piluts'. Many's the time I've been on a walk-round and stopped to try and comfort the poor frightened animal/animals who were sitting, deafened under the APU. Mind you, I was never aware of arriving with one less soul on board.:ok:

[Old Smokey]

Be assured that a cold compartment is certain death for day old chicks.

Tried it - 100% hit rate!:rolleyes:

Regards,

Old Smokey

[LEM]

Regarding the rear cargo hold, my assumption is quite simple: if the temperature was to fall below zero celsius, the passengers would collect frozen baggage at the end of the flight.
Imagine all the liquids in beauty cases and stuff like that...

But sure the chicks need a warmer welcome to this world in order to survive ;)

[Piltdown Man]

RadAlts give a reasonable indication of height during normal banked turn where the straight line distance along the "normal axis" from the plane to ground is greatly increased. Therfore, they are not directional.

[CaptainSandL]

LEM, great questions, sorry I was late into the thread.


Q1) Why the top of the yellow bar on the speed tape (the minimum maneuver speed ) is not coincident with the VREF and the green dot (flaps up maneuvering )?
Aren't they all supposed to be 1.3 VS??
A1) No, they are two different things. With flaps retracted, yellow bar indicates 0.3g manoeuvre margin. Green dot indicates flaps up manoeuvring speed based upon actual weight (ie stall speed) rather than standard block speed (eg 210kts).


Q2) On the ground you notice a difference of 7° degrees between the two IRS headings.
Can the airplane be dispatched?
A2) One IRS will be in error (unless both are 3.5 degrees out!), find out which one and if you can’t get it fixed, switch it off and you may be able to despatch with the serviceable one. See MEL for details on this.


Q3) Why is there a dead band on the elevators cables, and not on the ailerons cables?
A3) I am fairly sure that is because of the manual reversion mode where the elevator PCU (without power) is used as a link to the elevator tab rods. The dead band is always about 1.5 inches during manual reversion because of this, so I think it is this slack not being fully taken up when the PCU is powered.


Q4) Is it true the engine fire extinguisher does NOT reach the gearbox?
A4) Yes


Q5) Once for all: is it necessary or not to put the Standby Power switch to BAT in order to REALLY check if the Inverter is capable of producing current?
A5) I think so, unless anybody knows another way.


Q6) Why in the Brake cooling Schedule table in the QRH the upper right data are missing?
I mean: is it not possible to abort at 140 knots at 60 tons at an elevation of 2000ft?
Yes, me thinks!
A7) Yes it is possible to abort at those conditions – and faster, heavier & higher. The reference brake energy in the missing upper right area is probably not quantifiable thus we have to assume the worst nearest case ie approx 30 million foot pounds in my 22K -300 QRH. As it was an RTO it is not factored for head/tailwind so this puts you firmly into the fuse plug melt zone on the brake cooling schedule page.


Q7) Why in the WINDOW HEAT OFF non normal cklist we don't have to pull the Windshiels air controls, while we do have to do it in the WINDOW OVERHEAT nncklist?
(The condition is the same, in both cases the windshields will not be heated).
A7) I don’t have a WINDOW HEAT OFF nnc, but perhaps the reason is that heat has been removed due to the window being up to temperature rather than a full overheat. Like what you get sitting on a hot apron in full sun when a green ON light extinguishes.


Q8) If we lose the Battery Bus inflight, do the Pack valves remain open?
A8) Don’t know, sounds like one for the next time you are in the simulator.


Q9) On airplanes that have a DCPCS, is it true there are THREE motors on the main outflow valve instead of two?
A9) Yes, one for each auto controller and one for manual controller.


Q10) Discussing the ABORTED ENGINE START Recall Items, I've heard some people stating we do have to motor the engine after a shutdown due to NO OIL PRESSURE INDICATION by the time the engine is stabilized at idle!!!!
Can you believe that?
A10) Yes I can, because it is what the QRH says that you must do, therefore we must do it. We cannot start inventing our own procedures because we think we know better. The manufacturers know more than us and have for a host of reasons come up with the QRH. We are on very thin ice if we go against it.


Q11) Is the radioaltimeter "directional"? I mean, does it read more if you are in a banked turn?
A11) Yes because the LRRA beams are directional – vertically down the z axis from the transmitter aerials. However the over-indication in a banked turn would be insignificant until the AoB was beyond 30 degrees (Cosine of 30 is 0.866). And you really should not be beyond 30 degrees AoB when below 2500ft RA.


Q12) Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?
A12) On a long flight possibly yes. There is some heating to the aft hold as the cabin air is circulated around it, but the front has extra heating from the E & E bay and should be used for AVI.


Q13) Is the ignition spark more intense in the FLT position?
A13) No, same intensity but both igniters are used.

[LEM]

Thanks for all the replies!

I still have some doubts:

2) What I meant was if there is some sort of official tolerance in indicating the heading.
The comparator will warn us for a difference in pitch or roll, but not for a difference in heading.
I tried to find out in the maintenance manual, but couldn't find until what difference in degrees is the IRS heading considered acceptable.
Of course for large deviations there is no problem, as one IRS will be obviously wrong thus US, but the doubt arises for small deviations, like 3° ....


5) So what voltage do we see when at the gate, ground power or APU on, we select INV on the Ac Meter Selector?


7) On some airplanes there are no green ON lights for the windshields (making it closer to a dark cockpit), but there are OFF amber lights.

The cecklist is WINDOW HEAT OFF, NNC.3.2., and it says:

Condition: A window heat OFF light illuminated indicates that the controller may have removed all heat to a window due to an excessive temperature.

WINDOW HEAT SWITCH..........................................OFF
Limit airspeed to 250 knots maximum below 10,000 feet.


Probably they forgot to address the subsequent fogging consequences as they did in the WINDOW OVERHEAT NNC.



10) You are right, the manufacturer made the cecklist like that.
It still seems at first sight a nonsense to motor the engine if we want to protect the bearings, but maybe the advantages of cooling the core after the starting EGT peak is greater than the quasi-null stress on the bearings at such low speed.

So I swear from now on I'll make a motoring in this case also! :ok:



12) Regarding the dog... actually my question was too simplistic: it really depends...
Are they loading a SaintBernard or a Chihuaua?
Is it a one hour or a four hours flight?
Is the passengers compartment full or almost empty?

I'll try to put a bottle of water next time I fly to Sharm, but at present we only fly short range...

Probably a little dog might not survive, but I still think the story of finding it hard-frozen is an urban myth.

Thank you all!

LEM

[CaptainSandL]

Further to Q12) “Is the dog going to FREEZE TO DEATH if they load it by mistake in the REAR cargo hold?”

I found this in Boeing publication D6-76300-32, Detail Specification for a 737-300


Air Conditioning

21-27-00 CARGO AIR DISTRIBUTION

21-27-10 Forward Cargo Compartment

Forward cargo compartment stabilised air temperature shall be maintained above 40 degrees F everywhere at a distance more than 8 inches from the exterior walls and floor in flight up to maximum certified altitude. The cargo door area shall be excluded from this requirement.

21-27-20 Aft Cargo Compartment

Aft cargo compartment temperature shall be maintained above freezing (32 degrees F) when measured at least 8 inches from its exterior walls and floor. The door area shall be excluded from this requirement.

[I-2021]

tried to find out in the maintenance manual, but couldn't find until what difference in degrees is the IRS heading considered acceptable.

Hi,

beautiful :p Also waiting for some official answers, anyway I have never experienced Hdg differences greater than a couple of degrees... so maybe if they become greater there is a problem somewhere. No one wrote an "Instruments cross-check for dummies" yet ? :D

[Centaurus]

Request advice on this question: Departing very light weight on long runway (737) and perhaps for monitoring requirements, full thrust is used. The BRW is many tonnes less than even at the maximum assumed temp (say 55C).

Old Boeing manuals state that you should use V speeds for actual weight. On the other hand one performance engineer told me that is not so - that you use the V speeds for the actual OAT - even though they may be 20 knots or more higher than those for the actual weight. Seems a bit silly to me.

Why force the aircraft to stay on the runway longer than necessary. Also more chance of greater tyre wear and tear coupled with marginally greater risk of tyre failure at higher speeds?

[Seat1APlease]

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.

[I-2021]

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 ?

[Contract Con]

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:ok:

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:confused:

[alexban]

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 :confused:
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.

[Centaurus]

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?

[LEM]

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 :ok:

LEM

[LEM]

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????

[CaptainSandL]

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

[LEM]

Right! My apologies!:ok:

[LEM]

Anybody knows what does exactly indicates the red AUTOLAND warning light close to both recall panels in the Sabena 733 simulator in Bruxelles?

Thanks

[B737MRG]

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

[B737MRG]

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….

[LEM]

Thanks for the info, Pat, nice to know that.

[LEM]

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?

[The Red Max]

LEM
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

[LEM]

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 :confused:

[Terraplaneblues]

Q8 = Yes, mechanically latched

[AeroTech]

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.

[fly.net]

But the 35 knots thing is absolutely true. Try it, on a long taxyway, light weight, thrust levers at idle.


After reading your post, I have tried it this week, both on 737-CL and on 737-NG. I went up to 40 kts and thrust levers back in idle, but didn't see any AUTOBRAKE DISARM light.

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 ? :uhoh:

[Darkjet]

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........

[LEM]

Hi fly.net, no that's not a joke.
At least on the classic.
I'll try again, when feasible, we have 30 airplanes, I'll try to make a sort of statistic... :confused:

[Gary Lager]

I hope that the suggestion to regularly taxi commercial aircraft around at 35kts GS purely for the purposes of satisfying one's academic interest is only a joke! :bored:

Let's keep the interesting hypotheses on Tech Log or left to the Test Pilots, eh?

[Centaurus]

Re dead bands on the elevator in manual reversion. The FCTM states the ailerons also have a dead band. Quote:
"With both systems A and B inoperative, the ailerons and elevator are controlled manually. A noticeable dead band will be observed in both these controls".