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A320 Why do lot of pilots start chrono while starting engines?

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A320 Why do lot of pilots start chrono while starting engines?

Old 10th Apr 2016, 10:32
  #21 (permalink)  
 
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Yep, after two hours, 5 min warmup req for V2500.
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Old 10th Apr 2016, 11:40
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Since we're here.

IAE warm up less than two hours is 2 minutes. I just heard a theory that it isn't really for the warmup but to ensure the center tanks pump check is complete after second engine start and before take off. Any body else hear this?

(BTW, I just had this happen, last week. At the gate told FO to shut down #2, he does, it does't shut down! What do I do - what any Captain would do, try it again with the engine master, the third time I figured there was a problem and referenced the non-normal. I had to use the ENG Fire switch to shut the damn thing down, so yes that can happen)
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Old 10th Apr 2016, 12:34
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The IAE warm up is for thermal equalisation and to prevent shaft bowing.
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Old 10th Apr 2016, 13:12
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Common when the DC ESS BUS has a hiccup, ENG MSTR SW is gone burger, or the Engines fuel HP valve isn't interested either.

ENG FIRE P/B (no bottle). All associated valves will reset once the switch is pushed back in. Aside from the engineering questions prior to resetting, of course.

Does anyone know if the accessory gearbox is still turning below 18% N2?

Last edited by Bula; 10th Apr 2016 at 14:10.
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Old 10th Apr 2016, 16:06
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Tubby's post is basically correct except for the fact that shaft bowing has probably already occurred by the engine sitting without the shafts turning. Think of a dumbbell with heavy weights on both ends (fan & booster ---- LPT).

Although the engine dynamics are even more complex, here is a simple explanation of the IAE situation. Shortly after engine shutdown, heat begins to build up in the top portion of the engine due to the heat retained in the engine components and lack of venting for this trapped heat. This so-called "chimney effect" can deflect (bow) the low and high-pressure shafts due to the diametral temperature gradient. The maximum deflection generally occurs between 1 to 2 hours after engine shutdown. Therefore, if an aircraft's engines are restarted during that period, a bowed rotor start can occur that could create a rub condition along with rotor dynamic issues. Bowed rotor starts have been known to actually lockup the low-pressure shaft due to the LPT blade interference with the LPT shroud. By keeping the rotational speeds as low as possible for a period of time at idle speed, both the rotors and stationary components have a chance to stabilize which helps preserve clearances and therefore engine efficiency.

Hope this helps...
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Old 11th Apr 2016, 01:51
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It doesn't hurt.
Sure "it doesn't hurt." But where do you stop with that sort of philosophy? For instance you can conduct a walk-around pre-flight inspection while whistling Dixie. It doesn't hurt
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Old 11th Apr 2016, 09:09
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CaptainMongo
(BTW, I just had this happen, last week. At the gate told FO to shut down #2, he does, it does't shut down! What do I do - what any Captain would do, try it again with the engine master, the third time I figured there was a problem and referenced the non-normal. I had to use the ENG Fire switch to shut the damn thing down, so yes that can happen)
AFAIR after the Qantas A380's uncontained failure of #2, after they landed #1 wouldn't stop until the fire people drowned it with water and foam.
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Old 11th Apr 2016, 12:01
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What do I do - what any Captain would do, try it again with the engine master, the third time I figured there was a problem and referenced the non-normal. I had to use the ENG Fire switch to shut the damn thing down, so yes that can happen)
Ah, no not every Captain. I hope you had a look at what position the LP valve was in before you reached for the fire switch!
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Old 11th Apr 2016, 12:46
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Lookleft, interesting point, however the advice I have is 4-7 minutes before the engine shuts down in that scenario.

Curious as to why one shouldn't use ENG FIRE P/B in this scenario because honestly, I can't think of a reason one wouldn't. Of course this doesn't mean there isn't.
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Old 12th Apr 2016, 06:23
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Because the Supp Proc in FCOM tells you to only shut down using the ENG FIRE pb if the LP fuel valve is not closed. By using the ENG FIRE you have now disconnected a whole bunch of other systems including FADEC. Now engineering will need to attend the aircraft,which if you are not at an engineering port becomes an issue that could have been avoided if the engine was allowed to shut down normally albeit a little bit longer than normal.
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Old 12th Apr 2016, 07:12
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Still, better than sucking a loadie through it.
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Old 12th Apr 2016, 07:54
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The loadies should know that if I am parked at the gate with the beacon on then they shouldn't be anywhere near where they can be sucked into the intake. Its not much of an excuse when the CP asks me why I didn't follow FCOM.
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Old 12th Apr 2016, 08:30
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Should, yes. Always do, no.

Does the FCOM cater for "idiot walking towards engine"?

Too many people have gone down an engine and have come out the back in tiny pieces. I think your CP would be OK with you shutting down an engine by any means possible to avoid another one.
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Old 12th Apr 2016, 10:17
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My CP would be ok with it if I observed or was told that the idiot was about to go in the blender but they would not be ok with me using non-FCOM procedures on the possibility that an idiot just might or I thought there might be a slight chance of an idiot going through the blender. There is only so far that the PIC can idiot proof his/her operation and still stay within the rules.
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Old 12th Apr 2016, 13:41
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Hi lookleft, thanks for the reply. Fair point. That why we are Captains. We sometimes make decision based on knowledge, and sometimes it is just experience and skill. Not all are in FCOM as you know, and the circumstance would always dictate as you say.

If the engine doesn't shutdown you will still need engineering to attend because the HP valve is stuck open/and or ENG MASTER S/W is Unservicable. One is not going anywhere
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Old 12th Apr 2016, 19:13
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Lookleft,


If you would have read my post, you would have read that I followed the non-normal procedure (Engine fails to shut down) after cycling the engine master. I think cycling the engine master was a reasonable response since I had in my right seat a pilot who just came out of our training center, was on his first flight and this was the first time he ever operated the engine master in the airplane. But hey, what do I know, I only have been doing this flying thing for 34 years.
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Old 12th Apr 2016, 19:24
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While we're at it, whilst transitioning to manual flight why do some people insist on frantically pressing the takeover PB to disconnect the AP? Surely once to disconnect then once to silence to Calvary charge is enough? Just two clicks is all you need. Some people I've seen literally press it 10/20 times. I thought this clock starting was all a hangover from the Boeing days.
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Old 12th Apr 2016, 20:35
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Chesty, serious question. Given the number of aircraft movements in a day/week/year across the globe, and the number of people who as you say have gone down the front of an engine and out the back in pieces, do you really think it is a risk worth inventing ad hoc procedures for?

I suspect that taking a couple of extra minutes to evaluate the system state, have a quick glance at the supp proc if necessary and then have a bit of a think about the ramifications of any subsequent action would be a wise investment.

I get the sense that we, as pilots, often tend to focus on things that we perceive to be significant threats that when reviewed in the cold hard light of day are very low probability events (even if they do have a significant consequence).

This is, in part, ingrained in us from the very beginning. When you think back to pretty much any training there is a big focus on engine failures, seizures, fires etc but if you did a training matrix based on real world threats you might shift the focus to things such as two engine go arounds, unstable approaches etc, particularly if you reviewed the statistics surrounding the number of movements vs number of engine failures/fires/severe damage and compared them to things like movements vs TCAS RA's, unstable approaches, cocked up two engine go arounds etc.

Just a thought and definitely not a criticism
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Old 12th Apr 2016, 21:22
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If you can't shut down an engine using the normal cut off procedure and you see a ground guy heading towards that engine, or even near it, giving you seconds to make a decision why would you not pull the fire handle?

It isn't a made up procedure it is a valid way of shutting down an engine.
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Old 12th Apr 2016, 22:55
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I followed the non-normal procedure (Engine fails to shut down) after cycling the engine master.
If you have a look at PRO-SUP-70 no you didn't! The procedure states that if the LP valve is closed-cross line amber then no crew action is required. Cycling the Eng master 3 times is not in the procedure!

I think cycling the engine master was a reasonable response since I had in my right seat a pilot who just came out of our training center, was on his first flight and this was the first time he ever operated the engine master in the airplane.
All you did was demonstrate what not to do when faced with a situation that Airbus has already covered in FCOM. What happens when young Bloggs comes up for his/her check ride and the Check Captain saids "What would we do if we set the eng master to off and the engine didn't shutdown?" Bloggs confident in his/her response would say,"I've seen this before, I would cycle the eng master 3 times then push the ENG Fire switch!" The Checkie would then say, "Wrong Bloggs, we would look at FCOM Sup Proc and do what Airbus tells us to do."

Bula- The ENG MASTER switch operates the LP valve. The FCOM procedure states that if the LP valve is amber cross line then no crew action is required. This means that the master switch has done its job and you are just waiting for the fuel in the lines to make its way through the engine. If the LP valve line is still green then the master has not done its job then you use the ENG FIRE pb to force the LP valve to close. According to FCOM the time delay can take up to 2min30s which can seem like an eternity when you are waiting for something to happen. It also states "Keep ground staff informed" which is a nicer way of saying don't let the idiots get near the blender.
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