Engine start procedure on different engine types

[gnomegemini 7]

Hi there,

 

I read over the FCOM 1 procedures and FCOM 2 engine pages but didn't found anything. Deep in the dark cornor of my brain I barely remember that the engines had different procedures to startup: the GE is started eng 3+4 at the same time and 1&2 at the same time. At least that's what the lufthansa's do. The PW was started 3-4-2-1 I think and the RR 1&4 and 2&3 at the same time.

 

Now my questions: Is this correct? And the second question: why? What's the technical reason and approach why you start GE per wing and RR not? Why is the PW started one after one?

 

Thanks,

Stefan

 

Edit: I love her!

[scandinavian13 5,192]

 

 

Now my questions: Is this correct?

 

Depends on the airline SOP, really.

 

 

 

And the second question: why?

 

Some people will just throw their cars from Drive into Park when they park. Others put their car into Neutral, set the parking brake, let off the foot brake, and then set it to Park. Which one is "right"?

 

 

 

What's the technical reason and approach why you start GE per wing and RR not? Why is the PW started one after one?

 

A question mainly for those who wrote the SOPs. It may also be related to the pressures required to start, and the pressure through each duct. I'm not sure though.

[gnomegemini 7]

Wow what a fast answer. Thanks Kyle. So no technical reason behind that? I'm wondering because normally you write SOP's on technical facts. At least that's what I thought.

 

Some people will just throw their cars from Drive into Park when they park. Others put their car into Neutral, set the parking brake, let off the foot brake, and then set it to Park. Which one is "right"?

 

 

Hehe in germany, at least on the most not this powerful cars, you'd switch from 1st or rev gear to neutral to release the clutch and apply parking brake after this. Manual transmission is more funny while driving! 

[scandinavian13 5,192]

 

 

I'm wondering because normally you write SOP's on technical facts.

 

This would make sense, but to many, there is a 'right' way for everything: when to turn lights on and off, the order in which the engines start, who does what, etc etc.

 

 

 

Hehe in germany, at least on the most not this powerful cars, you'd switch from 1st or rev gear to neutral to release the clutch and apply parking brake after this. Manual transmission is more funny while driving! 

 

Forgot how many people drive manual still. Mine car is manual, but the last time I was in Germany, I was pretty much forced into an auto by the rental company: "every car in this class is auto!" I booked PDMR, for the record (the M in that string means "manual"). The lady then said "you don't know how to drive automatic?" To which I responded "I do...I just don't want to."

[KORDATC 80]

I know United using the PW4056 starts the engines 1,4,3,2. Their flight manual states that it's a unique start sequence, but it doesn't mention why they choose to do it that way. It also mentions to save fuel, pilots are allowed to start the next engine as soon as the prior engine start valve closes at 50% N2.

[skelsey 765]

Wow what a fast answer. Thanks Kyle. So no technical reason behind that? I'm wondering because normally you write SOP's on technical facts. At least that's what I thought.

 

Technical facts play a part of course... but often just as important are the Chief Pilot's personal foibles, how the Chief Pilot's last airline did it, "how we've always done it", how the accountants think it should be done to minimise the bills and procedures that have been created/modified as a result of the airline's own experience of operating the type (e.g. things which it turns out are being frequently missed/done incorrectly etc).

 

Edit to add: the Big Airline start their RRs two at a time, 3+4 then 1+2, so no particular hard and fast rule in that regard.

[keight 26]

any chance to get the fcom for RR model? or at least 2 pages from it, engine start proc and takeoff proc.

[G-CIVA 62]

Think Hydraulic Systems,

 

Think Hydraulic Systems that have all Air Driven Demand Pumps,

 

Think Hydraulic Systems that have all Air Driven Demand Pumps & the load this would place on the Duct Pressure during ENG Start,

 

Think about how to reduce this load on the Duct Pressure (switch two Hydraulic Systems OFF before ENG Start).

 

Think about which two Hydraulic Systems provide the LEAST ESSENTIAL loads during push back ( 2 & 3), then think about which Hydraulic Systems MUST be ON or switched to AUX because they provide ESSENTIAL loads during push back (4 & 1).

 

That might give you a clue why UAL start their engines in a certain way. i.e 4, 1, 2, & finally 3.

 

UAL have 4 Air Driven Demand Hydraulic Demand Pumps fitted to their 744s with no AUTOSTART option; EVERY engine start is a manually controlled operation.

[Lairyliam 17]

I was going to say because maybe the first guy who wrote SOP's back in 68 (ish) did it on that way on his old propliner, so its the way its done... 

But Steve's outline above is waaaaaaaaay better than that! thanks for explaining!!

[skelsey 765]

 

 

any chance to get the fcom for RR model? or at least 2 pages from it, engine start proc and takeoff proc.

 

Not really much to it.

 

Packs off, pull start switches 3 & 4, place fuel control switches 3 & 4 to run. Check the oil pressure rises, otherwise do the ABORTED ENGINE START checklist.

 

Repeat for 1 & 2.

 

Takeoff procedure -- set 1.2 EPR, wait for the engines to stabilise and press TOGA.

[keight 26]

Not really much to it.

 

Packs off, pull start switches 3 & 4, place fuel control switches 3 & 4 to run. Check the oil pressure rises, otherwise do the ABORTED ENGINE START checklist.

 

Repeat for 1 & 2.

 

Takeoff procedure -- set 1.2 EPR, wait for the engines to stabilise and press TOGA.

 

thank you very much for the info. and please couple words regarding manual start and timings for starter duty cycles.

[skelsey 765]

Manual start is rare -- only really required at high altitude airfields.

 

One at a time only in manual start as it is clearly not practical for a human to properly monitor two simultaneous starts.

 

Packs off, autostart switch off, pull the start switch. Wait for 25% N3 or max motoring if you can't get 25%, then select the fuel control switch to RUN. Verify the EGT increase and that the limits are respected.

 

In manual start there are obviously no automatic corrective actions so you have to watch for no EGT increase (within 30 secs of fuel on), no N1 rotation by idle N3, EGT increasing rapidly towards/beyond the limit, no N3 stabilisation at idle and/or no oil pressure increase.

 

Autostart switch goes off after the last engine you are manual starting is stabilised at idle.

 

For the starter, it's up to 3 minutes then run down to zero N3, followed by up to a further 3 minutes then run down to zero N3, followed by up to a further 1 minute then run down to zero N3 and allow to cool for 30 minutes.

 

Alternatively you can run for 5 minutes and then cool for 30 minutes.

[keight 26]

appreciated.

 

packs off - all three or like on GE two are enough?

 

did not get about 'Autostart switch goes off after the last engine you are manual starting is stabilised at idle.'

it has already been switched off before.

[G-CIVA 62]

Much of this is all good stuff, but, as I pointed out earlier up the thread, the type of Hydraulic System fit appertaining to your particular aircraft type should have a large influence on the method of engine start you implement.

 

If the aircraft is fitted with a Hydraulic System that has Air Driven Demand Pumps on all four Hydraulic Systems this will have an effect the Duct Pressure & it this effect will become detrimental as the density altitude or the SAT increases.

 

Of course if the aircraft is not equipped with an Autostart Switch at all this will require a full manual start of each engine.

 

For example the original Cathay Pacific fleet of RB211 equipped 744 & 744F fleet were equipped with an all Air Driven Hydraulic Demand Pump Systems & no Autostart System for the engines.  All of these aircraft have now been retired, scrapped or sold to other operators, if their liveries have been modelled I wonder if these features have been correctly replicated??

 

Just like I quoted earlier, their Engine Start sequence was in individual order, 4, 1, 2 then 3.

 

4 first because Hyd Sys #4 powers Normal Brakes & it is obviously important to get that engine running first.

 

1 second because Hyd Sys #1 powers Alternate Brakes & it is obviously important to get that engine running next.

 

Now, 744s which are fitted with AC driven Hydraulic Demand Pump Systems on # 2 & #3 do not suffer from such a venerability since once these systems are switched on BEFORE engine start because the Normal Brakes are also powered by HYD Sys #3 & the Alternate Brakes are also powered by HYD Sys #2 - such is the redundancy built into the B747-400!.

 

Thus there is more back up availability & less demand on the Duct Pressure & the APU which is required for Engine Start.

 

This venerability is the reason why there is an AC Auxilliary Pump fitted to HYD Sys #4, indeed there is a customer option to have one fitted to HYD Sys #1, which many cutomers do opt for in real life.

 

Thus if you are 'starting' an aircraft with a 'mix of Air Driven & AC Driven Hydraulic Demand Pumps the 'norm' is 4,3,2 & 1.  

 

Not all 744s are the same, just like the many variations of a basic model of a motor car.

 

If you then have Autostart you can comfortably start 2 together - the 'ususal' configuration is to leave Pack 1 'ON' with Packs 2 & 3 OFF although some airlines like BAW start their engines with all Packs 'OFF' as they believe it prolongs the life of the APU.  Others carrier SOPs vary.

[KORDATC 80]

4 first because Hyd Sys #4 powers Normal Brakes & it is obviously important to get that engine running first.

 

Any reason why United would start 1,4,3,2?