737-400 Centre Fuel Tank Boost Pumps Off
Having personally flown all B-737 series from the -100 through the NG -800 for 16 years I have a good feel for probably what happened here. While I hasten to add that I have been out of the 737 series flying for over five years now, I nevertheless recall a few of the got-chas on the aircraft and strategies used to mitigate same with fuel. Since the aircraft was a classic aircraft (737-400), I will leave the NG (-800) stuff mostly out, but it is a factor as all Qantas 737 crews fly both -400 and -800 virtually every day they fly more than one sector which is most days.
1)The first exposure for the flight crew to the fuel system is during preflight of the overhead panel when the Captain verifies that the fuel in tanks was what was ordered preflight by referring to the numbers (usually written on his hand ;>). Then on the fuel panel, (in my day the Captain, but now) the F/O would select all boost pumps on (wings and center pumps – six in total) just prior to engine start. To my knowledge, Qantas aircraft did not have aux tanks operating in their 737 fleet in 2007. Also a couple of years ago Qantas procedures aligned with Boeing procedures changing areas of responsibility from the Captain to the F/O on the fuel panel before starting (As I recall it but I could be wrong here). Added to this, Boeing issued an AD that says to leave the fuel boost pumps off until just before starting the engines. This is a mitigating factor as in the past, all boost pumps were placed on when the fuel was correct in tanks. That Boeing AD, no doubt issued for a good reason, nevertheless, set this situation up to happen.
There is an exception to all boost pumps-on which is when there is no fuel in the centre tank, or less than 453 kg of fuel in the centre tank in the classic 737(-300-400). In this latter case the centre pump switches are left off. With 4700 kgs. in the center tank, this was the first missed opportunity by the F/O (monitored by the Captain) to turn the centre tank pumps on. Qantas procedures have changed making the preflight fuel panel an area of responsibility of the F/O, however, both are responsible for the fuel.
On the NG -800, fuel pumps are left off by Boeing procedure for less than 2300 kgs. in the centre tank until after takeoff. As you can see, there are several different procedures relating to fuel boost pumps with differing amounts of fuel on each of the -400 and NG -800. In most cases on most sectors, the centre tanks are in fact procedurally left off for takeoff. That was not the case for 4700 kgs in the centre tank on this sector. The centre tank pumps should have been selected on by the F/O before starting the engines.
2) During the reading of the Before Start Check lists, when it came to “Fuel”, the Captain would announce the fuel in tanks “12,300 kgs. and Pumps-On”. When I flew the 737, the response was "12,300 kgs and x pumps-on and we ordered 12,300". There was a clear cross check of the fuel quantity and fuel pumps selected on. Procedures changed and the pumps were missed. This was the second missed opportunity by the Captain, and by the F/O who was to place the fuel pumps on according to procedures and then read the check list. The F/O should also have verified that the responses were correct on the fuel panel from the Captain in agreement with the checklist and the aircraft configuration for the sector. Both the Captain and F/O missed the centre tank pumps off.
3) After take off and accelerating to climb speed was the first time airborne to check the fuel state and pumps on/off, particularly if you had intentionally left the pumps off prior to takeoff (see para. 1 above). The error could have been caught at this early stage but it was not.
4) After level off, there should have been a scan of the aircraft systems and automation to ensure that all is well. This was the best time to have caught the fact that the fuel pumps had been left off during preflight.
5) It was correctly pointed out earlier in this thread that with the center boost pumps off, the caution lights would have been off as well. Only seeing the switches in the off position and/or noticing the dwindling fuel content in the wing tanks while the centre tank quantity remained unchanged would tip off the crew that the centre pumps were selected off. The fuel caution lights only appear when one or both pumps are selected on and one or both pumps develop low pump output pressure (not low fuel quantity). In the -400 there are no other electronic warnings associated with low fuel in the wing tanks irrespective of the content of the centre tank. This was corrected in the NG series by Boeing.
6) To the crew’s credit, they did catch the error but it could have been even more embarrassing for them and Qantas if one or both of the engines had flamed out before the discovery of their oversight.
7) This incident was set up by the Boeing AD and pre-departure procedure changes in my opinion. In addition this was one crew's error on one sector on one day. It’s that simple. With thousands of considerations on every sector to deal with, stuff happens, pilots some times make mistakes, but hopefully, strategies are put into place over one’s career to mitigate such occurrences earlier, rather than later and certainly before its too late. Over the thousands of hours flown in a career we all have horror stories due to our own oversights or distractions. If you haven’t, then either you're not being honest with yourself or you just haven’t been flying very long. Pilots are humans and humans err. CRM and a host of procedures are designed to mitigate such errors from becoming incidents.
8) In this case, Boeing put a hole in the 'Swiss Cheese Model' with a fuel boost pump AD to leave the fuel pumps off to the last minute before the checklist, and changed procedures that changed the fuel panel from the Captain to the F/O. Like most incidents in aviation, there is almost never a single cause. In this case I firmly believe that the cause should be shared between the Boeing AD notice to leave fuel pumps off until starting engines, pre-start procedures and with the pilots error on the day. It is not all the pilots' fault. I am not bashing anyone here.
9) Its too simple to say that crossword puzzles were being done or newspapers being read without knowing the facts, tongue-in-cheek or otherwise. Obviously these sorts of things were not being done at every point mentioned above when the threat could have been discovered and corrected negating a potentially dangerous situation. Pilot error can have many causes.
10) Nevertheless, my 41 years of flying tells me that there was more involved in this incident than just what was on the surface of it. Knowing a little about Qantas and its reputation, the pilots involved would have been dealt with fairly but firmly after this incident and procedures put into place or existing ones reinforced to hopefully prevent it happening again. Nothing is ever procedurally perfect nor pilot-proof as we all know too well. Having said that, aviation is our business and we love it (or most of us do).
Others may have differing views and they are entitled to them. Best regards, Magnet77
Last edited by Magnet77; 31st Jul 2008 at 13:53.