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pilottj

Aft Cargo Heat temp question

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Hey guys,

Quick question about the aft cargo heat, what temp is it supposed to maintain?  I thought with the last QOS it was around 60-65F or whatever the C equivalent was.  With QOS II, I can't seem to warm up the aft cargo hold.  I have packs on, aft heat on.  Am I missing something?  There doesn't appear to be a magenta thermostat setting in the aft cargo deck on the ECS page.

 

Can anyone else confirm aft cargo heat working or not?  Don't want Fido to freeze his paws off.

 

BTW I checked the FCOM but couldn't find the right info there either.

 

Thanks

TJ

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At all altitudes and exterior temperatures?

 

There is a limit to how much heat the system can pump into the plane.  At high pressure altitudes and/or low temperatures, it will not always keep up with the losses.

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From United's manual : The aft compartment uses hot air directly from the cargo bleed air duct through thermostatically controlled valves. An aft cargo heat switch on the air conditioning panel provides on/off control and overheat warning for the bleed air supply to the aft cargo compartment.

 

So basically, it's not meant to maintain any set temp like the forward compartment is. Hope this helps.

 

Cheers,

Rob

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There doesn't seem to be any temp control indication on the ECS page.  The lower deck controls seem to have no effect either.  (There is no magenta thermostat indicator) as with the main deck and upper decks.  

 

Currently I am on the ground (OAT ~ 35F) testing with the ERF with doors closed, APU and engines running at idle, packs on, cargo heat on, lower deck temps set to 'auto'.  The main deck temps are set to auto as well, ~ 63F is the thermostat setting.  Again no magenta thermostat indicators on ECS page for the lower decks.

 

Cheers

TJ


Here is a screenshot

https://drive.google.com/file/d/0B-7nGfv-Xq0nMXo4ajVObkhsdzg/view?usp=sharing

 

Again, its on the ground with OAT ~ 35F, doors closed, Engines/APU on, Packs on, Aft Cargo ht on.  Since it is an ERF model, it has temp controls for all zones.  Shouldn't there be a magenta thermostat indicator for the lower decks?

 

Cheers

TJ

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Tejon,

There are no temperature selectors for the lower cargo bays. The forward compartment is heated by the equipment cooling air exhaust from the flight deck and main equipment rack bay. It also has a few electric aux. heaters that try and maintain approximately 40°F. Up at altitude when it's negative -30°C outside it can vary a bit. But it's at least controlled automatically. See my above post for how the aft cargo bay is heated. Bottom line is, you cannot control them precisely like the main and upper decks.

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In the ERF and standard F models there are indeed zone control dials for upper, main, and lower decks, see the screenshot above.  

 

I understand the Pax version, the cargo decks are not as precise as the passenger deck, but I understand it is still supposed to be at a level that is bearable for pets.  

 

There would be a lot of frozen dogs and cats if the aft cargo heat didn't work lol.

 

Cheers

TJ

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My pax version is showing 45 for the front and 46 and 48 respectively for the rear cargo.  I do agree, that seems too chilly for pets.  I will say, for my first flight I forgot to turn on the cargo heat and the rear was like -1/2 respectively and my rear pax zone would not warm up above 60.  I thought it was interesting how the cold air was coming through the floor of the rear compartment. 

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On the synoptic you show for the ERF, the lower lobe cargo should show the selected temperature for forward and aft compartments in magenta, but these appear to be missing.

 

The lower (that is, below the main deck) cargo compartments have separate bleed air supply, and can be heated, or not.

 

There should be a selector on the upper maintenance panel for selecting the compartment(s) to direct bleed air to, and at what rate (high/low) but this appears to be missing.

 

Currently, it would seem the lower cargo compartments are UNHEATED (selector OFF, if it was fitted).

 

Best regards,

Rob Smith.

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Question, then should the PAX version have magenta indicator(indicating the temp it is trying to maintain) for the lower forward cargo compartment, even it it is less precisely controlled?

 

 

Speaking of cargo deck heating, didn't Boeing propose a lounge area (ala 377)back in the early 747 days?  I think it was going to be called the Tiger Lounge or something, but that proposal never attracted the interest of the airlines.  I can't remember if the Tiger Lounge was set in the fore or aft cargo area.

 

Cheers

TJ

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Question, then should the PAX version have magenta indicator(indicating the temp it is trying to maintain) for the lower forward cargo compartment, even it it is less precisely controlled?

 

No. In this case, the conditioned air extracted from the cockpit, via the equipment bay, is then exhausted into the forward cargo hold. On the ground, it is then expelled overboard (otherwise the valve closes and the air is recirculated back into the equipment bay). The cargo hold will be above ambient temp, but not controllable. On longer flights, it can become quite cold.

 

Best regards,

Rob Smith.

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Ok thanks for the info, I coulda sworn QOTS 1 had a magenta indicator for the forward cargo bay temp on it's ECS page.  Maybe I am confusing it for the QOTS 1 Freighter, its been a long time since I've flown it lol.  

 

Cheers

TJ

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Boeing provide optional Lower Lobe Cargo airconditioning (front and aft). There is a control knob on the overhead maintenance panel so you can select which lower lobe areas are conditioned. Here is an example:

 

FreighterCargoFlowRate.jpg

 

Obviously, if your aircraft is only fitted with one airconditioned cargo zone, the switch is much simpler.

 

 

If you select airconditioning on in the forward cargo area, the magenta target temperature will appear for that area. If you select both aft and fwd lower lobe cargo areas to be conditioned, there will be magenta targets for both zones.

 

If you select the airconditioning off for the lower lobe cargo areas, these areas will be heated by the normal heating systems:

Forward cargo: equipment cooling recycled air with supplementary electric heaters inline with the ducting), and

Aft and bulk cargo: cargo heat system using bleed air.

 

Here's where it gets tricky. Some aircraft have a unique valve for the bulk cargo. Other aircraft just send the same heated air to both zones. There is a switch near the bulk cargo door which can be selected to two different temperatures. The hotter one is for pets. If there is no independent control of the bulk cargo, then this switch will affect the whole aft cargo.

 

The supplemental heaters for the forward cargo are powered by AC Bus #3 (and DC Bus 2 for control) and are active when there is at least one engine running on each wing. And when you're down to Standby Power only... There's not a lot you can do... :Tounge:

 

StbyPwrECSsynoptic2.jpg

 

Of course, there will be variations to this... It's Boeing :Tounge:

 

Cheers

John H Watson

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P.S. I forgot the optional overhead heating vents in the bulk cargo. This is a fan/heater system.

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Thanks for the great info John, Rob, and Robert.

Yes, so many options, probably one the many of hundreds of 747 customer options.  There are probably so many ECS options that PMDG simply didn't have time to model it all.  I am sure PMDG could spend years modelling every little customer option lol.  

 

It's not a big deal, tho after flying A2A's COTS, I've been a bit more mindful of 'pleasing' the passengers, and their pets.  We don't want Scooby Doo to freeze, otherwise we have to send him Hot Rum Toddys with his Scooby snacks...Ruh Roh!  :lol:   Sadly IRL quite a few pets have died on flights because the Crew wasn't informed there were pets onboard, and thus never turned on the Aft Cargo Heat.    

 

But yeah, ~40-45F is a bit cold for pets, especially on a long haul flight.  A more reasonable temp for pets is ~60-65F and if I recall right that was about the temp QOS v1 ran with Aft Cargo Heat on.   Again, virtually speaking, it's not a big deal, PMDG has already given us so much good stuff with the Queen, but I am sure there are a lot of pet owners on Avsim who want their little friends to be comfortable, even virtually. :smile:

 

Cheers

TJ

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