for B737 Classic questions...PLEASE HELP ME!!

[snake80]

1- How you can test the standby electric system before flight?
2- during non prec APP ...Automatic G/A is able or not?..why?
3- how much fuel burn in hold?
4- How do you perform a diversion?

Thanks!!!!

[James W Pocock]

The normal check for the standby power is during the preflight cockpit prepartion. just as it says in the Boeing manual.

The check assumes that the Aircraft is powered by an A/C power source which is fed to the Essential A/C buss and via the T/R to the Essential D/C busses.

If the Battery master switch is placed to On and the Standby Power Switch is in Normal or Manual the Standby busses will be powered and the correct indication will be shown on the N1 and EGT indicators. All powered, all normal.

Howerver, if you want to induce a failure, ie outside of the system test requirements.

Either,
1. Prior to establishing A/C power , check that the Standby Power Green ON light illuminates when the Battery Switch is place to ON and the Standby Power Switch is placed to Normal or Manual ON.:)
or
2. If A/C power has been esstablished to the Essential A/C and hence to Essential DC busses via the Essential T/R, either by the engine or APU generator/s or External Power, then, if you have to, select the Essential A/C Bus Switch to OFF and Essential DC Bus Isolation Swtch to Open. This will induce a failure of both the Essential A/C and Essential DC bus bars.:eek:

However, this is not something that you would want to do in normal operations. Leave this to the simulator or the maintenance department. Nice to know, not nice to do.

[James W Pocock]

The normal check for the standby power is during the preflight cockpit prepartion. just as it says in the Boeing manual.

The check assumes that the Aircraft is powered by an A/C power source which is fed to the Essential A/C buss and via the T/R to the Essential D/C busses.

If the Battery master switch is placed to On and the Standby Power Switch is in Normal or Manual the Standby busses will be powered and the correct indication will be shown on the N1 and EGT indicators. All powered, all normal.

Howerver, if you want to induce a failure, ie outside of the system test requirements.

Either,
1. Prior to switching on the External A/C power or APU A/C power, check that the Standby Power Green ON light illuminates when the Battery Switch is place to ON and the Standby Power Switch is placed to Normal or Manual ON.:)
or
2. If A/C power is esstablished to the Essential A/C and hence to Essential DC busses via the Essential T/R, either by the engine or APU generator/s or External Power, then, if you have to, select the Essential A/C Buss Switch to OFF and Essential DC Bus Isolation Swtch to Open. This will induce a failure of both the Essential A/C and Essential DC buss bars.:eek:

However, this is not something that you would want to do in normal operations. Leave this to the simulator or the maintenance department. Nice to know, not nice to do.

[James W Pocock]

Forget all last reply not B737, all for B747 Classic

[Swedish Steve]

The B737 standby power check is quite complicated and best left to an engineer. When I looked after B737 we did this check every nightstop. It involves tripping CBs and turning off the ground power. Leave it alone.

[Empty Cruise]

OK, my 2 eurocents' worth - and for the 73CL :D

1) BAT on - check voltage - STANDBY POWER switch to BAT - check you have both BAT bus voltage, SBY DC voltage, SBY AC volts + freq and INV volts + freq. Then select STANDBY POWER switch back to AUTO and proceed with normal preparation, i.e. either do the firetest & start the APU or connect the GPU.

2) For the same reason that auto-go-around is not available during a single-channel CAT1-approach - there is only one channel engaged, and therefore Boeing doesn't seem to like the idea that just one auto-pilot flies away happily without another auto-pilot to compare & check what's going on...

3) Depends on mass (and therefore variant), have a look in the QRP or use the FMC HOLD-page to predict holding cabability. However, for the -300 typical approach masses, you can use 45 kg/min. or 2,7T/hr as a consevative guideline. Add 10% for LEDs extended and 50% for gear extended NB guidelines only - don't you & your lawyers come running if you run out of fuel ;)

4) It starts way before you go around @ your destination - if the WX looks as though it's gonna be tight & a diversion might need to be performed, you make a point of covering the following in your approach brief (along all the oter stuff, of course...):

a) WX at alternate must be good enough to allow a few margins - if you're no longer comfy with your alternate, nominate another one while you still have the fuel. If contamination might affect the usability of the alternate, remember to allow time for snow-clearing - or, preferably, find another one.

b) Minimum fuel for diversion - this one needs to be carved in stone, it's a contract between the 2 crewmembers that "When we hit (e.g.) 2200 kg - unless we have a runway visual in front of us and are cleared to land - we divert, no ifs, no buts, nomatter where we are in the approach!". Make sure your companys flightplans take the direction of the missed approach into account - e.g. LPA rwy 03 with alternate TFS using rwy 08 - if the plog says 600 kgs., you must go "Yeah, right...whatever...I'll call that 1200 kg.for comfort, thank you very much" (LPA 03 MAP goes to the NE by about 40 NM, TFS is WSW of LPA).

c) Taking b) into account - how much holding cabability do you have? Is it worth holding out till you need to divert, or if they come up with a tight EAT will you divert straight away? (and thus maybe be the first on the ground on the alternate, beating all the heroes who hold & hold till their eyes water and they need to go, right now!). There can be benefits in diverting early, especially if the wx appears to be improving - chances are everybody else is also using the same alternate, so you'll be first in the queue for ramp space, fuel & handling - that'll mean that you're first out again when your destination re-opens. Oh, and you won't be the last guy diverting, only to hear the words at the alternate "Ground is full, go away!" :E Also look at things like when the airport closes, when the firecover drops below the category you require, when the fuellers go home etc. etc. - all these might dictate that you divert while you still have plenty of fuel in the tanks.

d) The planned routing & requested level to the alternate, and a brief look at the expected arrival & approach (so they don't chatch you out, especially if the alternate is near the destination - the diversion might only be 10 min. flight from when you hit TOGA, so no time to be clueless).

e) If time allows, have PM call the approach unit at the alternate airport and ask "If we came by in 20 min. - what would the traffic be"? If the ATCO starts laughing and and says "Think of a number between 10 and 18" :{ - then you need a plan C, fast!

f) Get on to the company via ACARS or via the handling agent (or - if further afield - via HF phonepatch) and ask them for their preferences if more than one alternate might be usable. If they are alerted well in advance, a good ops will have the handling organised, have a new flightplan in the system, or have organised coaches, hotac, engineering support and all the other goodies you might need.

g) When it's chrunch-time, tell ATC a couple of minutes i advance that you're requesting clearance to XXX at FL NNN via XZY. Fly the last holding lap in HDG SEL and raw data while PM prepares the FMC. This is done by going to RTE page 1 and inserting you alternate as the new destination. From there on, you can select the arrivals & approaches as you normally do.

h) And finally - make the mental note that once you hit Final Reserve Fuel, you'll yell MAYDAY loud & clear & get that priority. Better advise ATC like, 5 minutes before it gets really critical - they don't mind-read (despite the fact it sometimes seems so :ok: ) When you reach the point where you have doubt that fuel remains for another approach - make sure to brief accordingly, it's way better to crash during a less-than-perfect autoland inside the fence than it is to glide to a random crash-site outside the fence.

I have without doubt forgotten a really important point, I'll leave it to the next posters to correct me.

Hope this helps - cheers fm
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[mimi737]

Hi Snake 80,

1-No autoland will be available during non precesion app. Second autopilot will not engage as long as approach mode ( on mcp ) is not pressed and this work only with valid ILS freq...

2-Check your QRH to get your fuel burn in holding or you may also check the performance volume.

Happy landings.:)

[mimi737]

Sorry i forgot the diversion=

1- In CDU: press the route page
2- change the destination 4 letters code
3- U will be then able to choose an app from arrival page.

Or request radar vectors:bored: ;-)))

best.

[LEM]

Empty Cruise, great post!

One little comment: there seems to be a common misconception about the increase in fuel burn with the gear down.

Is 50% really enough?

If you check the QRH and compare the Reference Fuel and Time Required at Check Point both for the All Engines and Gear Down cases, you'll notice you'll need amost twice fuel!

Example: 200 miles, at 20000ft: 1100 kg in 37 minutes, versus 1900 kg in 43 minutes with the gear down.

Be careful!

:ok: LEM

[Empty Cruise]

LEM,

yep, you're right with regard to cruise - when I read the QRP late at night, I need someone to explain to me exactly what "...per engine..." means. :O :{ My saving grace that I remembered the usual disclaimer...

For the holding, 5000 ft. PA/50 T, the -300 QRP gives 2340 kg/hr with flaps up/gear up and 3260 kg/hr with flaps up/gear down - so that's a factor of just shy of 1,4.

Thanks for the heads-up, my friend - stay safe ;)

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[Gufo]

This was a recent issue which popped out during our recurrent training: by checking the AC Standby Pwr voltage and current, what you're actually doing is reading the output of Transfer bus 1, since Standby AC is paralleled with XFER1.
The only way to really check if AC stdby would be available, in case of AC power loss, is making sure the static inverter is working normally, through the INV volts&current output.

Just 2 pennies :O

[Empty Cruise]

Hi Gufo,

Yep - that's why you have to do it without any AC power being applied - hence 1) Cold aircraft 2) BAT on 3) STANDBY POWER switch to BAT etc. etc. - that shoud pretty much guarantee that it's not XFER BUS 1 supplying the power ;) :ok:

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[Gufo]

Mmmh.. Erm.. I actually meant inflight conditions.. Sry, I misread :\

One pint paid, Empty Cruise! And that's good posting of yours, anyway :ok:

[Empty Cruise]

Gufo,

Actually, you're right - Snake doesn't say anything about weather he was looking for a pre-flt or in-flt check - so I must have ass-u-me-d...doh! :\

And I suppose removing all AC power in flt is rather impractical - so no need, keep the beer in the bank, I'll prolly need it to repay you another day :O

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[LEM]

Hi Guys, removing all AC is not really needed... just select Standby Pwr on Bat and the Standby busses will be fed from the Battery and Inverter.

Regarding the gear down case, it's true the fuel flow is 1,4 times greater, but in a diversion you'll have to maintain 220 knots instead of normal speeds, thus the almost twice total consumption.

Ciao, LEM :ok:

[Empty Cruise]

Hi LEM,

Of course - SBY PWR switch to BAT in flight will do the same. Re. the fuel consumption - it's quoted with regard to Snakes' 3rd question re. how much you burn while holding - so yes, for holding it's around 1,5 and for diversion about 2,0 ;)

Cheers,
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