737NG low fuel QRH action
 

I asked this question on another thread (R&N), but no response. Capt S&L or someone please!

It appears that the 'LOW' indication is set at 907kg by Boeing (for ETOPS). It is changeable to 453kg by operators for non-ETOPS I understand.

The QRH calls for a drill at the 'LOW' indication, presumably to ensure adequate fuel flow to both engines. If this is 'necessary' at 907kg (un-modded), why can it be ignored on a modded a/c and only completed at 453kg, or is there a special instruction to carry it out at 907kg on those?:confused:

The QRH is only actioned when the light comes on irrespective of whether its 453 or 907 aside. Its triggered by a wing tank reaching one of those figures not a total amount although in practise 907 or 1814 will be the least you have when the first light comes on.

As to why its one thing for ETOPS and another for non ETOPS I can't tell you I'm afraid. No experience of ETOPS to draw on so I can't even hazard a guess. Maybe its something to do with reserves in order to be ETOPS at the time? as 907 very roughly equates to final reserve. What I can say is that below a set amount of fuel you have to switch the electric hydraulic pumps off on the ground, I think its 1400 there or there abouts, due to cooling and it does seem a touch odd that the low fuel warning is not set at or above this with a QRH ref to remind you to switch them off.

- that's what they pay us for - don't need a light!

Anyone know the answer?

BAOC I did actually answer part if not the main part of your question which is why I posted.

I hope you find the rest of your answer.

Hi BOAC,

Before I answer, for those that don’t know, 907kg & 453kg may appear to be precise but they equate to 2000lbs & 1000lbs. Read into these very round numbers what you will! See here for photos of these displays.

I asked Boeing about the origin of the 907kg back in 2003, their answer was as follows:
They went on to say:
The flight tests must have gone well because in June 2005 the 453kg/1000lb option became available with the introduction of CDS Block Point 04. A quick quote from the SL does not really give us the reason behind the change:

My guess is that operator demand for a lower LOW fuel threshold drove Boeing to review the 907/2000lb figure. During this flight testing it was found that at least one of the pumps would remain covered by fuel down to lower levels than previously thought necessary. Remember each engine has three pumps; a forward, an aft and an engine driven pump, any one of which will keep the engine running at MCT. Hence Boeing could persuade the FAA that the LOW fuel warning could be reduced. The higher ETOPS limit was probably retained because it was deemed that the warning should come on earlier as you may be further from a suitable airfield, but again that is just my guess.

Rgds

S&L

Thanks both. The query still remains unanswered, however . Why, non-ETOPS, is it necessary to action the QRH on un-modded a/c at 907?
- I guess they didn't bother?

I am surprised that they 'allow' operations with crossfeed closed and no restrictions on pitch/acceleration at 500kg a side, however. By then I would be walking on eggshells:eek: