737 Questions

[Olendirk]

Guys,

appreciate your opinion:

1. Flying a rnav-overlay departure according fmc with a beacon integrated, which is on test, so not working, am i allowed to fly this dep route when i have gps or not?


2.When do you switch on the ctr tank fuel pumps, how many kgs have to be in it. sometimes we get the low pressure lights on takeoff?


3.Aborting a takeoff, which is the critical temperature when the plugs melt?from the brakes?

Thanks so much!


OD

[Mshamba]

1. Yes you are allowed as it is a RNAV-Departure, so you will need RNAV-Equipment. If it is working you are legal. No raw data necessary, but according most SOP you will have to "crosscheck". But a NDB is mostly also defined by a radial and DME, so just crosscheck with these datas and you should be fine. Anyway: the answer is still yes.

2. Takeoff/climb: both pumps on if more than 2300 kgs in the centertank, when dropping below 960 kgs crossfeed selector open one centertank fuel pump off. If "low pressure light" on remaining centertank fuel pump starts to flacker switch it off and crossfeed selector close. Performing a takeoff with less than 2300 kgs fuel in the centertank the fuel pumps remain off, switch them on during climb (e.g. flap-check at FL100) or during cruise.

3. I only found this in the QRH:
BRAKE TEMPERATURE MONITOR SYSTEM INDICATION ON CDS
5.0 TO 7.5 CAUTION
7.5 & ABOVE FUSE PLUG MELT ZONE
and the numbers are EVENT ADJUSTED BRAKE ENERGY (MILLIONS OF FOOT POUNDS)
whatever it means - maybe a maintenance person can help by converting into degrees centigrade.

[CaptainSandL]

737 fuse plugs melt at approx 351F / 177C.

[Denti]

1) Yes, you are allowed if you are RNAV approved and can use that without the requirement for conventional navigation backup or if you can replace the required fix by other means of conventional navigation (VOR/DME aka radial and distance). Most classics are not approved to use RNAV without conventional navigation backup, on NGs that is normally not a problem if you have 2 GPS and 2 FMCs. However specifics are a question of the approval your company holds and the rules laid down by our local authority.

[Johnny F@rt Pants]

Mshamba

Not sure where you get the info re centre fuel tank pumps for take off.

I can't find the ref but I'm sure it states somewhere that the centre tank fuel pumps can be on if the fuel in the centre tank is 453kgs or above. However we leave them off if there's less than 1000kgs due to the possibility of a master caution on the take off roll due to both centre tank low press lights illuminating. Certainly don't take off with the x-feed open.

[Denti]

I guess he is working in an airline that hasn't yet modified all its 737 NGs according to AD 2002-24-51.

There are alternative procedures in use to comply with that AD, you have to switch on the Center Tank Fuel Pumps if more than 1000lbs (453kg) are in the center tanks on the ground, however that is only allowed if personnel is on the flight deck to observe the center tank low pressure lights.

Before starting taxi they have to be switched off again with less than 2300 kg of fuel in the center tank (5000lbs) to be off for take off. Above 10.000ft or when the pitch is reduced to accelerate to a climb speed of 250kias or greater both center tanks should be switched on if more than 2000 lbs (950kgs) are in the center tank.

Switch one pump off if the quantity reaches 2000 lbs (or 950kgs) and open the crossfeed during climb and cruise, switch off the remaining pump at the first flicker of the low pressure light and close the crossfeed valve.

During descent switch off one maintank fuel pump if less than 3000 lbs (1400kgs) of fuel remain in the center tank and open the crossfeed valve. Switch off the remaining fuel pump at the first flicker of the low pressure light, close the crossfeed valve.


This procedure of course is only applicable if your employer is too cheap to modify its airplanes according to the mentioned AD and rather raises the crew workload than spend a few bucks on safety, and it is only applicable to the NG series. Newer planes are modified of course and even newer ones have the NGS (Nitrogen Generation System) fittet as standard which generates nitrogen out of the bleed air stream and uses that as air-source for the center tank.

[Permafrost_ATPL]

You've had enough replies regarding the tanks, but regarding question 1...

B-RNAV or P-RNAV?

B-RNAV: no you cannot fly the departure without raw data, unless there is no turn below MSA (i.e. straight ahead departure climbing you above MSA, THEN using one or more navaids for the rest of the procedure)

P-RNAV: you don't need any navaids to fly them. You just need to have approval for it and the right equipment.

Cheers

P

[Jinkster]

Centre Pumps

I used to fly an NG around, some had modified pumps, some had non-modified pumps according to AD 2002-24-51

I now fly a -300 series around and all pumps appear to have been modified, I asked a few of the training guys and they had not heard of this mod before.

[Flight Detent]

Oh Boy....what a shambles of differing responses to that fuel management question...

The appropriate procedure for your model of 737NG will be provided in your personal copy of the FCOM Volume 1, Normal procedures.

Whatever is provided there is what you will do..

I've never heard such a confusing shambles of half-truths and second-hand rumours..

This is a very important aspect of your everyday operations, I'm completely gobsmacked each and every NG pilot doesn't know these backwards!!

'nuff said from me...

[Denti]

Nah, in areas where you normally never use the center fuel tank it isn't, it is just something you look up once you have to use it (about once a year for us).

[Johnny F@rt Pants]

Flight Detent

Where does it say that the question was about NG's, my answer was for the 300, which is the only 737 variant I've flown.

And my reply still stands.

[Navigator33]

I don't have a personal FCOM copy. Just a digital one