Cabin Superchargers Inlet Switches Operation

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WB_FlashOver
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Cabin Superchargers Inlet Switches Operation

Post WB_FlashOver »

Hello all,
I have been controlling the aircraft fully for a long time now, except for the pressurization. I may be up to kicking the FE out the door fully in the near future :wink:

I've searched and read several posts on the function of the cabin supercharger switches and how the superchargers function in relation to cabin heating/cooling and pressurization. From what I can gather the Cabin Supercharger Inlet switches merely open valves to allow air pressure from the engine superchargers to be use for cabin heating, cooling and pressurization. Is this a correct assessment?

My last few flights have been in central Africa with temps around 43C and keeping the cabin cool has been a real challenge. Watching the FE do this task prior I notice he seems to have the switches closed until airborne in more moderate climates. Would the cooling work better on ground if the switches were open?

Thanks
Roger
-- Fly Well, Be Nice, Have Fun ! ! !

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flapman
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Re: Cabin Superchargers Inlet Switches Operation

Post flapman »

WB_FlashOver wrote:I may be up to kicking the FE out the door fully in the near futur
My friend, you're missing out! Let him take a comfortable seat in first class on your next flight!
WB_FlashOver wrote:Is this a correct assessment?
Because those switches are labelled "Supercharger L.H./R.H. Inlet" my assumption is that they actually control the introduction of air into the #1 and #4 cabin superchargers. It might also be the case that they control outflow valves from the superchargers, but this might be redundant if there's not inlet air to pressurize. Actually the manual makes mention of both inlet and outlet valves, and they might be controlled by the same switch. It makes sense to isolate the pressurization/ventilation system in case of an oil leak in a supercharger, engine fire, or other problem...
This brings up a finer point which you might not have realized by now... the engine superchargers are separate from the cabin superchargers!
Image

These separate air compressors are engine accessories, which are bolted to the back of the engine next to other accessories such as generators, fuel pumps, vacuum pumps, and oil pumps.
WB_FlashOver wrote:Would the cooling work better on ground if the switches were open?
Yes, the manual states that supercharger inlets must be open so the superchargers can force conditioned air through the cabin/cockpit/equipment ventilation system. I leave them on all the time, and consider turning them off to be an abnormal procedure. I also use the "Cooler" switch as a ground blower, having it on on the ground only during warmer weather.

My pressurization tips are as thus: set your RATE OF CHANGE to .3(300fpm). Follow the placarded schedule during your climbs and descents. Set an appropriate cabin altitude after takeoff and monitor the system. During descent, reset the cabin altitude as placarded as you pass through the reference airplane altitudes. The FE sets 8,000' as landing because he doesn't really know what altitude you plan to land at. You the pilot can do better! Set landing altitude +100 or +200' for a nice ride all the way down, and to ensure the airplane is depressurized for landing.

Manual pressurization is fun!

Also, I've noticed that no matter what I do with the inlet switches, I see no change to the flow indicators at cruise altitdue :(

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WB_FlashOver
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Re: Cabin Superchargers Inlet Switches Operation

Post WB_FlashOver »

Thanks for the response flapman

I guess I got confused by the manual. Three places it talks about the cabin pressurization using the engine superchargers, quoted here;
Page 97
Cabin Pressurization Module driven by the dual speed superchargers

Page 103
Some people will notice some new gauges here when compared to our GA and Warbird aircraft, including a pressurization system that uses the pressurized air coming from the engine superchargers.

Page 103
The Constellation uses the higher air pressure generated by the engine superchargers to increase the cabin air pressure. This requires the superchargers to be running, especially as you fly into the very high, thin air up at higher altitudes.
But then under a section on the heating system it talks about there being separate cabin superchargers.
Page 135
Two Stewart Warner gasoline heaters located in the outboard nacelles: These heaters burn a small part of the fuel vapor from the engine induction system and exhaust back into the induction system. Each heater is equipped with one automatic and one manual igniter and an electric motor driven valve for control of the fuel flow. Warm air from the heaters is forced into the cabin by the cabin superchargers, therefore, the inflow and outflow manual valve controls must be in the BOTH OPEN (forward position) and the outboard engines must be operating to obtain heat.
There seems to be a contradiction here OR maybe the "cabin superchargers" are only for heating/cooling. Anyways, I will operate the inlet switches accordingly as you state.

I typically start a flight in the FE seat to start engines and get her ready for flight. I tell the FE to sit in the step for the door and watch the pressurization while I take care of the rest. I then move to the pilot seat and stay there until at altitude at which time I crawl over the seat to the FE station. I fine tune the engines until I feel all is good. Then back to my seat and stay there. For normal operation I can see all I need to see of the FE station by simply looking over my shoulder. Sometimes there is the need to hop back there to manage fuel tanks and such. Not so with the lower panel of interest. I have taken control of the pressurization when landing at high altitude but that is a pain the caboose while on descent and approach playing musical chairs with descending (make adjustment) and leveling off (make adjustment), descend some more (make adjustment) and level off (make adjustment), etc, etc. If I was capable I would create a 2D panel to replicate the pressurization panel and take full control of all systems while staying in the pilot seat.

Thanks again Sir.
Roger
-- Fly Well, Be Nice, Have Fun ! ! !

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Zacke
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Re: Cabin Superchargers Inlet Switches Operation

Post Zacke »

Hey guys,

it seems to me the supercharger inlet switches don't have a simulated function at all.

I pulled out the Connie after some absence for doing some rtw and this morning I performend an excessive line of ground checks (not taking her to the air yet). I noticed with idling engines the air flow indicators show a pressure around 2 - 3 (from memory) and it doesn't matter if the switches are on or off.
As I remember the 377's air flow gauges did actually react on switches position and the cabin pressure dropped off shortly after one swichted that "cabin" superchargers off.

Regards,
Zacke

Barth56
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Re: Cabin Superchargers Inlet Switches Operation

Post Barth56 »

Hello,
I also wondered the same, as they seem to have no function, and I compared these with the B377 too...
Probably a forgotten function to add in the final L049 model before release?...
Ah... A2A will correct this in the upcoming L1049G! ...wait... ;)

Barth

Zacke
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Re: Cabin Superchargers Inlet Switches Operation

Post Zacke »

...dreaming... ;)

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WB_FlashOver
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Re: Cabin Superchargers Inlet Switches Operation

Post WB_FlashOver »

A friend put together a 2D climate control panel for me for the Connie. It has all the functions of the FE's station. With this I have been running everything on my own now. I have been noticing that, to the best of my interpretation, the cabin is easier to keep cool at lower altitudes (under 4,000) with the switches in the closed position. On approach the cabin temps start to rise, I close the switches and the temps will come back down after several minutes. Keeping them closed on the ground seems to help as well and then opening them around 3,000-4,000 feet on climb. As far as using the switches for pressurization, I have not closed them at higher altitudes. The advantage of doing all this myself is that I don't get crying kids anymore. Knowing what I plan to do is better than the AI FE trying to guess at my intentions and making drastic adjustments when none is needed.

I really need to play with this in static weather sometime. I rarely get the chance to fly anymore so when time permits I just go for a flight.

Image

Cheers
Roger
-- Fly Well, Be Nice, Have Fun ! ! !

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Zacke
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Re: Cabin Superchargers Inlet Switches Operation

Post Zacke »

Hello Roger and thank you for your very interesting input.

Yes, I always handle the pressurization myself for achieving optimum passenger comfort. ;)

Concerning your observation with the rising temperatures on approach: Are you sure this does not have to do with the need to switch from heating to cooling when descending into warmer air? If the FE is active with the cabin controls he does switch from body heaters to cooling system when the OAT and cabin temperature is appropriate (and vice versa in climb). If you control the system yourself you have to switch over yourself to keep the cabin temperature comfortable.

Is I understand the cooling system is pure electrical (other than expected in the manual or in the A2A promo video) and the "cabin" superchargers are only for pressurization purposes.

So far I can't see any simulated function of the switches.

Regards,
Zacke

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WB_FlashOver
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Re: Cabin Superchargers Inlet Switches Operation

Post WB_FlashOver »

Yes, I watch OAT and switch from heater to AC and back when needed. I'll keep watching and testing. I understood that the AC compressors are on engines 1 & 4 only. I need to look into it more to fully understand. :?:

Roger
-- Fly Well, Be Nice, Have Fun ! ! !

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Zacke
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Re: Cabin Superchargers Inlet Switches Operation

Post Zacke »

No, I don't think number 1 and 4 do have anything to do with the AC exclusively. That's stated in the A2A manual and was intended so originally. But in the sim in fact the AC is driven only by eletricity and therefore you need all four generators running for the AC to work.
Maybe number 1 and 4 do drive the superchargers that are needed for the pressurization system. But I don't have tested that yet.

Regards,
Zacke

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