Taxiing out with #2 and #4 - 748

[Heffron 29]

1 hour ago, windshearDK said:

wow interesting thank you! But usually when you turn on the hydraulic systems you put 1 or 2 in AUX and not on... Is it the right to left logic with simply some in the AUX position

This procedure was for the 777. For the 747, during the Before Start Procedure, you would put HYD 4 in AUX first, then 3, 2, and 1 in AUTO. Or if the aircraft is equipped with an auxiliary pump on system 1 and 4 it would be 4 to AUX, then 1 to AUX then 3 and 2 to AUTO. For shutdown you would put selectors 1, 2 and 3 in OFF and 4 in AUX. When the chocks are in place you can release the parking brake and then also select 4 to OFF. Or else, if parking brake will remain set you would keep 4 in AUX for 30 seconds after parking brake set, and then select #4 to off, to prevent excessive pump wear.

[vc10man 732]

That now explains to me why FS2Crew's PNF/FO does that. Had wondered why. Enlightened, indeed.

[kevinh 409]

On 1/27/2019 at 9:50 PM, berts said:

Maybe so, but the real danger of climbing to a higher altitude is that you are more likely to be climbing into even colder air, so that when you level off and resume your normal cruising speed the potential fuel icing problem will not have gone away, but could possibly become far more serious in a shorter time period.  Normally the rate of cooling can be in the order of 3C per hour but in extreme conditions it has been known to be up to 12C per hour and it can take up to an hour for the fuel temperature to stabilise in warmer conditions.

Inflight conditions are of course different for every flight and so I accept this decision could involve a climb as you say if the air is known to be warmer higher up, but the fuel flow can also be increased by flying faster at the same or a lower altitude and the increase in speed should help to slow down the 'cold soak effect'.  Keeping an eye on the Total Air Temperature is key to anticipating the potential risk of the remaining fuel in the tanks starting to wax as ice crystals, which incidentally can occur below the freeze point of the fuel. Unfortunately, the amount of fuel reserves being carried these days is often the minimum required for the flight and this commercial pressure can sometimes have an adverse impact on the possible options available to the crew, i.e. deviating to a warmer air mass;  or descending and flying faster (which I suggest is normally the preferred option).   

All that is true but the reason Boeing now don’t recommend VS for step climbs is as I said. See the report into the BA38 incident. 

[Jetlinker 13]

8 hours ago, kevinh said:

All that is true but the reason Boeing now don’t recommend VS for step climbs is as I said. See the report into the BA38 incident. 

In addition to this using VS to climb at higher altitudes is never a good idea as it has no low speed protection. There are certain instances that may warrant its use, such as trying to get down to intercept a glide slope if you’re slightly above it.. but generally speaking it is preferred to use other modes than VS for a typical climb or descent. Like with THR, the VS button is one that usually has some dust on it as it is seldomly used. At least that’s how I was trained. 

Edited January 30, 2019 by Jetlinker

[berts 97]

On 1/28/2019 at 9:53 AM, windshearDK said:

Guess there are things you don't know..

I am the first to agree with you, because there are lots of things I don't know about the B747 or the -8 and never will - and neither do you if you are equally honest.   Probably very few people do, except for Boeing's original Chief Engineer, Joe Sutter, and a few on the aircraft's current design and engineering teams.  

8 hours ago, kevinh said:

All that is true but the reason Boeing now don’t recommend VS for step climbs is as I said.

I agree the use of V/S to climb the aircraft is not normal practice, mainly because speed protection is not fully available during Altitude capture.  However, Step Climbs can be carried out in the B744 using V/S where there is no risk of conflicting traffic; for example over Australia.  Provided ATC has granted permission for an altitude 'block', the aircraft can then cruise climb slowly to the higher Flight Level.  Fuel icing isn't a problem in this case, but the speed should be monitored closely during Altiutude capture because there is always the potential danger it could decrease if, for example, an engine fails at this point or if the aircraft does not have sufficient energy to maintain the capture profile.

[sloppysmusic 256]

34 minutes ago, Jetlinker said:

In addition to this using VS to climb at higher altitudes is never a good idea as it has no low speed protection. There are certain instances that may warrant its use, such as trying to get down to intercept a glide slope if you’re slightly above it.. but generally speaking it is preferred to use other modes than VS for a typical climb or descent. Like with THR, the VS button is one that usually has some dust on it as it is seldomly used. At least that’s how I was trained. 

I've been working through the fcoms while practicing flying the plane using manual NAV only with VORS. During cruise yesterday at 37500 I actually read the fcom paragraphs about cold fuel and noticed my fuel was at - 12c. I followed the guide and used flc chg with clm thrust to initiate a climb to 38000 but then thought why am I climbing to lower fuel temp. OK a 10000 ft climb at clmb thrust is a lot of friction but at cruise I don't have much altitude to gain and then coffin corner is getting smaller.. 

Sure enough after leveling off at 38000 the temp was now at - 15c so they fcom wasn't the best I've seen so far! Flight was KIDA to KPSP btw so real world weather is affecting sim flying now. 

I presume a better action would be to descend 10000 feet then initiate a climb back to the same altitude which would waste a lot of fuel but definitely warm it up in the process? Flight still had an hour to go before descent so descending early and staying low would have burnt up too much fuel. 

 

I'm using the 777 by the way for clarification. 

Edited January 30, 2019 by sloppysmusic

[skelsey 765]

1 minute ago, sloppysmusic said:

I've been working through the fcoms while practicing flying the plane using manual NAV only with VORS. During cruise yesterday at 37500 I actually read the fcom paragraphs about cold fuel and noticed my fuel was at - 12c. I followed the guide and used flc chg with clm thrust to initiate a climb to 38000 but then thought why am I climbing to lower fuel temp. OK a 10000 ft climb at clmb thrust is a lot of friction but at cruise I don't have much altitude to gain and then coffin corner is getting smaller.. 

Sure enough after leveling off at 38000 the temp was now at - 15c so they fcom wasn't the best I've seen so far! Flight was KIDA to KPSP btw so real world weather is affecting sim flying now. 

I presume a better action would be to descend 10000 feet then initiate a climb back to the same altitude which would waste a lot of fuel but definitely warm it up in the process? Flight still had an hour to go before descent so descending early and staying low would have burnt up too much fuel. 

Russell,

I think you are misunderstanding the purpose of the Boeing guidance quoted above (applicable only AFAIK to the B777 with RR engines).

It's not an instruction to climb because the fuel is cold (and -12 is not very cold: Jet-A1 has a freeze point of -47C, so you don't really need to worry until it gets to about -44).

What it is saying is that if you are doing a step climb (ignoring the question of fuel temperature), they recommend you use FLCH or VNAV because the higher thrust (and hence fuel flow) is considered to be beneficial to prevent ice crystals accumulating in the fuel lines.

If you did have a fuel temperature issue then, as Bertie says, you would generally be looking to descend and/or speed up (as the air lower down will normally be warmer, and speeding up increases TAT).

If you don't have sufficient fuel to reach your destination with the required reserves at the lower level then you would need to consider diverting!

[sloppysmusic 256]

31 minutes ago, skelsey said:

Russell,

I think you are misunderstanding the purpose of the Boeing guidance quoted above (applicable only AFAIK to the B777 with RR engines).

It's not an instruction to climb because the fuel is cold (and -12 is not very cold: Jet-A1 has a freeze point of -47C, so you don't really need to worry until it gets to about -44).

What it is saying is that if you are doing a step climb (ignoring the question of fuel temperature), they recommend you use FLCH or VNAV because the higher thrust (and hence fuel flow) is considered to be beneficial to prevent ice crystals accumulating in the fuel lines.

If you did have a fuel temperature issue then, as Bertie says, you would generally be looking to descend and/or speed up (as the air lower down will normally be warmer, and speeding up increases TAT).

If you don't have sufficient fuel to reach your destination with the required reserves at the lower level then you would need to consider diverting!

Thanks for the info! The PMDG supplied FCOM quite definitely states that during cruise less than 2 hours before descent but not less than 15 mins if fuel temp is less than 10c then the step climb procedure is used specifically to rectify this. What you say is accurate for sure but this FCOM is very misleading I believe. I can't share the actual page here due to the EULA but give me a few moments (I was on a tablet) and I will quote the page number. Definitely states that the step climb is used to warm the fuel and for no other reason.

777 FCOM 1

Supplementary procedures Chapter SP Section 12 Fuel (SP.12.1)

Cold Fuel Operations

I'm paraphrasing here:

"Within 2 hours TDD but not less than15 before TD if fuel temp less than -10c

Either

1)Do a step climb using MCT or VNAV preferred (not option for me as manually controlling flight)

2) Select CLB THRUST and manually push throttles to maximum (didn't want to try this at 37400 feet as danger of overspeed?).

IF FT is warmer than -10c then no crew action is required. "

So yes with some 30C margin remaining away from actual fuel freezing the FCOM actually asks you to perform what surely must be non-normal procedures? i.e. full throttle in level flight!

Edited January 30, 2019 by sloppysmusic
Fixed mobile-speak autocorrections

[downscc 1,327]

2 hours ago, sloppysmusic said:

So yes with some 30C margin remaining away from actual fuel freezing the FCOM actually asks you to perform what surely must be non-normal procedures?

Not really.... do not use this procedure if temperatures do not warrant cold procedures.  This SP is designed to flush the filter in the event there is an accumulation of ice or wax.  In normal conditions this procedure achieves nothing for you.  The pilot uses judgement based on training and experience to recognize when cold fuel procedures should be implemented.  In my own very limited judgement, I would not be doing the non-normal procedure if SAT were warmer than -65C, TAT above -30C and fuel temperatures as low as the TAT.  In normal conditions, it takes a long time for fuel to chill to low TAT ranges so time spent cold also is a factor.  These cold conditions are not typically found unless long duration flight over Siberia, and some of the coldest SAT will be found above the equator.

[sloppysmusic 256]

2 hours ago, downscc said:

Not really.... do not use this procedure if temperatures do not warrant cold procedures.  This SP is designed to flush the filter in the event there is an accumulation of ice or wax.  In normal conditions this procedure achieves nothing for you.  The pilot uses judgement based on training and experience to recognize when cold fuel procedures should be implemented.  In my own very limited judgement, I would not be doing the non-normal procedure if SAT were warmer than -65C, TAT above -30C and fuel temperatures as low as the TAT.  In normal conditions, it takes a long time for fuel to chill to low TAT ranges so time spent cold also is a factor.  These cold conditions are not typically found unless long duration flight over Siberia, and some of the coldest SAT will be found above the equator.

There's some great info there thanks. My common sense told me it was plain wrong or ill advised but your background info and experience explains why. It's as if this particular FCOM was edited from the original and parts left out, as it says cold weather but not freezing which is actually the dangerous time. The filter is mentioned elsewhere. This is a small section isolated from all others grouped with fuel leak/imbalance. 

I read the whole of the 737 documentation and practiced it and it was 100% rock solid and in a sensible order. The 777 FCOM jumps all over the place we start with shutting the plane down then take offs/landings then starting the electrics up. It surely wasn't originally placed in this order? I understand the FCTM is the actual training doc and this a bunch of supplements but still. Generally fascinating stuff to read whatever order though! Just started FCOM 2 , will be reading in between tracking VORS later tonight.