19AB67

[FSX] EQUIP COOLING/LOW FLOW: Real behaviour?

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Hi folks, 

I am just conducting 747F flight Cargolux CLX762 from ELLX/LUX to SBGL/GIG and loaded delicate freight into the forward lower lobe compartment. 

Due to the freight's nature (don't know what it is? .. mushrooms for Brasil? LOL)

- I set the AIR FLOW RATE to LOW-FWD and

- I turned the FWD TEMP selector down to 9 o'clock position. 

Without seeing the connection the EQUIP COOLING message popped up (EICAS) and EQUIP LOW FLOW (STATUS). 

According to QRH I set EQUIPMENT COOLING SELECTOR

- on ground to STBY

- in flight to OVRD

The latter eliminates the message in flight, however, due to the QRH advice to land at the nearest suitable airport I was in doubt regarding the flight to Rio. 

Another thread here in the forum Aft Cargo Heat temp question provided the following: 

On 03/02/2017 at 2:58 AM, KORDATC said:

The forward compartment is heated by the equipment cooling air exhaust from the flight deck and main equipment rack bay.

Playing on the FWD temperature selector the 'higher' 10°C notch (two show 10°C) and higher temperatures eliminates the CAUTION messages in the NORM selection as well. 

I checked the 747 FCOM, but found no information that the FWD lower lobe compartment shouldn't be cooled below 10°C. 

So, if the EQ compartment exhaust is used to heat the forward lower lobe compartment, it might be impossible to cool it below a certain value. 

Any thoughts? 

Is the real behaviour? (I think so...) 

Edited by 19AB67
Added 747F reference. Added two notch info.

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16 hours ago, 19AB67 said:

- I set the AIR FLOW RATE to LOW-FWD and

- I turned the FWD TEMP selector down to 9 o'clock position. 

Were all the packs turned on and the cargo doors closed?

I don't really know what's going on in your case. The forward cargo heating system is extremely complex, even on aircraft without the optional airconditioning in the forward cargo. On aircraft without cargo airconditioning, the temperature in the cargo (in flight) is a battle between atmospheric temperatures and equipment cooling heat. I have seen water leaks in the forward cargo area which have generated 6 inches (15cm) or more of ice on the cargo area floor, thanks to the coolness of the aircraft skin. If the equipment cooling heat is not warm enough to overcome these cold temperatures, additional inline duct electric heaters periodically add to the heat of the equipment cooling exhaust air (i.e. after it has passed through the equipment ). These heaters go on and off between 4C and 10C. Whether these heaters do stop the temperatures in the cargo on aircraft fitted with airconditioned cargo zones going too far below 10C, I'm not sure. In theory, the heaters shouldn't come on until 4C, but stay on until the cargo has reached 10C.

Regarding the optional forward cargo heating: The airconditioning system can put out some pretty cold air at times (even enough to generate small pieces of ice in the distribution ducts). Whether this pack coldness will override the heat from the equipment cooling and electric inline heaters, I'm not sure.

I can't explain the low flow problem, but switching to OVRD is just going to exhaust the equipment cooling air into the atmosphere. I guess this will deprive the forward cargo of any heat (unless perhaps the cargo airconditioning was turned on). I'd have to do some intensive re-reading of the maintenance manual to see what happens to the forward cargo airconditioning system when you put the equipment cooling to OVRD (if anything). :tongue:

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On 16/11/2017 at 7:08 AM, Qavion2 said:

I can't explain the low flow problem

Hi John, 

do your PMDG 747Fs behave the same way, ie.

starting with the lower 10°C notch and cooler settings of the FWD temperatur selector and lower lobe on (low/high flow), does the message EQIP COOLING message show up? Does it vanish starting with the higher 10°C and warmer settings? 

Thanks. 

Edited by 19AB67
grammar!

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I think this is the appropriate behavior. The relevant section of the FCOM is here (page 2.20.17):

Quote

Flight configuration depends on the position of the Lower Lobe Cargo
Conditioned Air Flow Rate selector and the temperature selected by the Forward
Lower Lobe Temperature selector. With temperature selected lower than 50°F
(10°C), the Lower Lobe Cargo Conditioned Air Flow Rate selector in FWD LOW,
BOTH LOW, or FWD HIGH, the inboard exhaust valve is closed and equipment
cooling air is recirculated in a closed loop mode. With higher selected
temperatures or all other positions of the Lower Lobe Cargo Conditioned Air Flow
Rate selector, the inboard exhaust valve is open and the warm equipment cooling
exhaust air discharges into the forward cargo compartment.

The "flight configuration" they're talking about is to allow cabin pressurization. The warning indicates equipment cooling is operating in alternate mode.

Marcel Durieux

  • Upvote 1

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On 19.11.2017 at 9:21 PM, durieux said:

FCOM is here (page 2.20.17):

Marcel, 

I had checked the FCOM, but couldn't find it ... shame on me. 

Chapeau to PMDG, who present 'every' line in the FCOM of the real thing! 

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