Zaherk Posted October 21, 2012 Share Posted October 21, 2012 Hi Everybody, Maybe one of you guys had a similar experience, when we start No 4 eng from No 3, No 3 shuts down. Even when we start No 2, 1, 3 and then 4, No 3 shuts down on its own. She would not shutdown if we open the throttle to flight idle and then start No 4 or start No 4 first. She is like that since she went for rainbow fittings and a wing change in Malaysia. We've tried everything. Presumably there must be something wrong with wiring somewhere. Any suggestions would be appreciated. Regards Quote Link to comment Share on other sites More sharing options...
n1dp Posted October 21, 2012 Share Posted October 21, 2012 Just a quick stab; have you tried closing the bleed air to No. 3 after the start? It could be electrical, but can't seem to reason why the left side would have an effect. Quote Link to comment Share on other sites More sharing options...
NATOPS1 Posted October 22, 2012 Share Posted October 22, 2012 When does the No 3 engine "shutdown? After the other engine 4,1 or 2 is started and "on speed"? What is your GTC/APU bleed air check time? Sounds like you may have a bad Engine bleed air check valve which is allowing higher pressure air from your other engines to enter the combustion section of No. 3 Eng. Quote Link to comment Share on other sites More sharing options...
Ronc Posted October 22, 2012 Share Posted October 22, 2012 This shutdown is there any possibility it happens when you shut off the hydraulics to check the pumps. I have heard of depot swapping cannon plugs accidentally (fuel shutoff and hydraulic shutoff) and when the hydraulic switch is turned off the engine flames out, just a thought. Ron Quote Link to comment Share on other sites More sharing options...
Zaherk Posted October 26, 2012 Author Share Posted October 26, 2012 We started no 2 eng, went high speed, started No 1, shutdown the gtc, started no 3 and then started No 4, at about 50-55% on No 4, No 3 shutdown. If we start No 3 first, and then start no 4 using No 3 the same happens. The Eng was changed in the No 3 position for another problem and the snag is still the same, nothing changed. Quote Link to comment Share on other sites More sharing options...
kersey9502 Posted October 26, 2012 Share Posted October 26, 2012 What are all your engine indications reading at the time of shutdown? Is number three shutting down at the same time every time? And also, has number 4 reached parallel or has the secondary pump light illuminated yet? Quote Link to comment Share on other sites More sharing options...
Zaherk Posted October 26, 2012 Author Share Posted October 26, 2012 No 3 shuts down when RPM is between 50-55% on No 4, thats before starter release on No 4. It looks like a normal start cycle on No 4 except we loose bleed from No 3 because of No 3's auto shutdown. If you start the other eng's from No 3 there is no problem, only when you start No 4 from 3 there is a problem. If we got time before our next flight I get the crew and guys to look at both eng's when starting to look for more clues or something out of the ordinary. We're in Christchurch at the moment doing Antartic trips with this baby. Once she's started there is no problem, as long as the sequence is right. Quote Link to comment Share on other sites More sharing options...
tusker Posted October 26, 2012 Share Posted October 26, 2012 could there be a link somewhere between the/4 eng starting system wiring and the /3 eng condition lever wiring(for fuel cutoff Quote Link to comment Share on other sites More sharing options...
kersey9502 Posted October 27, 2012 Share Posted October 27, 2012 It could very well be linked to the ground stop circuit of number three. The question to be revealed is what is actually going on a 50-55% on number 4. Sometimes you will not get paralell until around that time. If the wires are shorted from that circuit to the ground stop circuit of number three, it could possibly happen. As far as number three and number four going through a common place such as terminal board or cannon plug is not likely. checking all the prints i dont see where they are in a common area except wire bundels. It will very interesting to see what other symptoms are going to surface when paying more close attention to the indications of that number four engine. Quote Link to comment Share on other sites More sharing options...
Lkuest Posted October 27, 2012 Share Posted October 27, 2012 Does this same thing happen with #3 bleed closed, but all other conditions the same? Also, remember there is enough fuel in the engine to maintain operation for a short while, so if fuel is being cut off from outside the motor, such as the fuel shutoff valve in the wing, the engine will not shut off immediately after the valve closes. There is nothing electrically that happens in the start circuit during 55% RPM that doesn't also happen at 16%. To test this, you might actuate #4 engine anti-icing during #4 engine start and see what RPM the malfunction occurs. If the RPM is the same, the problem may be electical, but I'm not sure how. If the problem occurs at the same moment (i.e. 30 seconds into start with or without anti-icing), it may be related to the fuel fire shutoff valve. Quote Link to comment Share on other sites More sharing options...
Zaherk Posted October 27, 2012 Author Share Posted October 27, 2012 So far the weather looking good for tomorrow, will look closer at both eng's 3+4 starts tomorrow and let you Gents know what happened. Thanks Quote Link to comment Share on other sites More sharing options...
Zaherk Posted November 1, 2012 Author Share Posted November 1, 2012 Hi Gents Sorry to have taken so long, started No 3 and then No 4 and it was a normal start with no auto shutdown at about 11 deg C, speculated that the previous auto shutdowns were temp and height above sea level related. It still does not make sense after the eng change. Suppose we'll still find out about it on our return trip in about a months time to RSA as it gets hotter and JHB is 5500 ft above sea level. Thanks for all your suggestions and inputs, will definately let you know if we find anything that explain this weirdness. Regards. Quote Link to comment Share on other sites More sharing options...
Zaherk Posted September 27, 2013 Author Share Posted September 27, 2013 About two months ago they found two wires swopped around in the leading edge when rainbow fittings and wing chance was done. Quote Link to comment Share on other sites More sharing options...
Lkuest Posted September 27, 2013 Share Posted September 27, 2013 I would be interested to figure out which two wires it was. It might explain the strangeness of the flameout timing, as well as why there wasn't another discrepancy associated with the wiring problem. Quote Link to comment Share on other sites More sharing options...
tinyclark Posted September 28, 2013 Share Posted September 28, 2013 I have seen many problems caused by corrosion in the outer wing disconnect panel. there was a depot level TCTO to replace all connectors at that junction. I came up with a diagram showing all wiring functions at the connectors. This was all good several years ago, but things change. You might check all connectors for corrosion. Quote Link to comment Share on other sites More sharing options...
Zaherk Posted October 21, 2013 Author Share Posted October 21, 2013 Hi Gents, The hyd pump shut-off valve from nr 3 eng caused nr 4 to shutdown, on the first start of the day when the shutoff valve was checked on start by FO, it shut the fuel on 4(Geneva lock). Technicians found the fault by playing with the switches on an eng ground run. Must have been wrongly wired when the wing change was done. Luckily never had an inflight EDP failure on no 3, what a suprise it would have been when nr 4 shutdown when switching the pump off on nr 3. Thanks for all your inputs and suggestions. Quote Link to comment Share on other sites More sharing options...
Zaherk Posted October 21, 2013 Author Share Posted October 21, 2013 Sorry Gents After posting and reading my post I confused myself. The FO switch nr 3 Hyd pump vlv off when starting nr 4 to check the Hyd pump press on 4, nr 3 eng then shuts down.It happened after a wing change when the rainbow fittings was done, do not know where they stuffed the wiring. In other words, when switching nr 3 hyd pump vlv off, nr 3 shutting down, closing the geneva lock. The eng was changed for a another defect but the snag remained. That's why the eng only auto shutdown on the first start of the day, when the individual pump pressures were checked. Regards Quote Link to comment Share on other sites More sharing options...
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