gaab

Falcon 50 autopilot

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Hello,

I need more explanations on the functioning of the autopilot altitude management.

I am obviously doing something wrong : it looks like AltSel does not work if VS is not active 🙂

Quote

g) The ALT/SEL mode is used to level off at the preselected altitude on the altitude set unit when the
autopilot is engaged in any pitch mode.

Also on the Autopilot panel,

Quote

The AP XFR
switch off/white tracks the NAV 1 signal and when on/green enables the autopilot to track the NAV 2
signal

Should not this allow to switch the HSI source ?

Thanks for this great plane and your help..

Gérard

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Posted (edited)
43 minutes ago, gaab said:

it looks like AltSel does not work if VS is not active

AltSel works with either VS or IAS so you can climb or descend to a preselected altitude at either a constant IAS (or MACH) or Vertical Speed. It is best to use IAS for climbs and VS for descents. If you climb or descend with IAS or VS but AltSel off, you must 'manually' level off at your desired altitude.

Additional info here on the AP IAS mode that may be helpful:

https://www.avsim.com/forums/topic/551823-lear-35-spd-mode/

Regarding the HSIs, Nav1 drives HSI#1 (pilot), Nav2 drives HSI#2 (copilot).

Al

Edited by ark

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Posted (edited)

Thanks for the clarification.

I had seen before the recommandation of climb + IAS / versus descent + VS, but I was missing the information that IAS was compatible with ALTSEL.
And just discovered that speed "reference marker" was not used for the AP.

Still a lot to learn 🙂

Another unrelated question, if I may : trying to stick to the checklist,

- I was not able to find the Emergency Battery SW (after start checklist)
- I don't understand the Cabin Pressure system (selector, controler, how one should select the cabin altitude - #30 and #34 of the Main Panel Information picture)

As this has been obviously simulated with great care, I would love to learn how to use them...

Gérard

Edited by gaab

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Posted (edited)
4 hours ago, gaab said:

Thanks for the clarification.

I had seen before the recommandation of climb + IAS / versus descent + VS, but I was missing the information that IAS was compatible with ALTSEL.
And just discovered that speed "reference marker" was not used for the AP.

Still a lot to learn 🙂

Another unrelated question, if I may : trying to stick to the checklist,

- I was not able to find the Emergency Battery SW (after start checklist)
- I don't understand the Cabin Pressure system (selector, controler, how one should select the cabin altitude - #30 and #34 of the Main Panel Information picture)

As this has been obviously simulated with great care, I would love to learn how to use them...

Gérard

The Emergency Power switch is on the overhead panel just to the right of the Generator3 switch.

The general idea of the cabin pressure system is to maintain the 'effective' altitude of the cabin lower than the aircraft's actual altitude. For example, if the a/c is at 30, 000ft you would like the cabin's effective altitude to be something like 10,000ft or below so passengers do not have to wear oxygen masks. So you can set what you want the cabin's altitude to be, and the rate at which it reaches that altitude. Pressure drops as altitude increases, so if the a/c is at 30,000ft and the cabin altitude at 10,000ft, the pressure inside the aircraft is greater than outside the aircraft -- the difference is the differential pressure. For example, on a standard day at 30,000ft the pressure is about 4.4 psi (pounds per square inch). At 10,000ft it is about 10.1 psi. Therefore, to have a cabin altitude of 10,000ft when the aircraft is at 30,000ft requires a cabin differential pressure of 10.1- 4.4 =  5.7 psi. The a/c bleed air system is used to provide this pressure differential through the cabin pressure control system. The rate info has to do with how fast the cabin reaches its 10,000ft altitude. The a/c may be climbing to 30,000ft at an average VS of 3000ft/min (just to pick a convenient value). So if you wanted the cabin to reach 10,000ft just as the a/c reaches 30,000ft, you would want the cabin altitude to climb at a rate of 1000ft/min. When descending from 30,000ft the general overall process is reversed. Note if you are landing at an airport that is at a 4000ft altitude, you want the cabin altitude to be about the same before you 'pop open' the cabin door.

So that's the 'big picture'. Simulating cabin pressure is not something that particularly interests me so I haven't played with the Falcon's cabin pressure control system. There are some very knowledgeable folks on this forum who I'm sure can give you the pressurization specifics for the Falcon.

Al

Edited by ark

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Thank for these detailed explanation, as usual.

I have read a lot of your interventions here which have always be very helpful for me.

Gérard

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Posted (edited)
15 hours ago, ark said:

The Emergency Power switch is on the overhead panel just to the right of the Generator3 switch.

I looks like it is the test button to check voltage, not the actual switch.. anyway not that important 😉

Gérard

Edited by gaab

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43 minutes ago, gaab said:

I looks like it is the test button to check voltage, not the actual switch.. anyway not that important 😉

Gérard

As far as I know, that E Batt PWR test switch, and the HRZN STBY PWR test switch to the left of the Generator 1 switch (for the backup AI), are all there is as far as emergency power switches go in this Falcon 50 simulation. 

Al

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20 hours ago, ark said:

As far as I know, that E Batt PWR test switch, and the HRZN STBY PWR test switch to the left of the Generator 1 switch (for the backup AI), are all there is as far as emergency power switches go in this Falcon 50 simulation. 

Al

The switches on the overhead panel are indeed there only to check the voltage of the emergency batteries. The standby horizon battery has no “on/off control. The battery comes on line automatically if primary aircraft power fails when the aircraft is in air mode (weight off wheels). This can be a “gotcha” during maintenance. If the aircraft is placed on jacks, the WOW sensors will be in air mode. If the aircraft is powered up with a GPU while in this condition, then power is subsequently switched off, the emergency battery will come on to power the standby horizon, which will eventually deplete it if this is not noticed. For this reason, the maintenance manual requires the emergency battery to be disconnected whenever the aircraft is on jacks.

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Posted (edited)
1 hour ago, JRBarrett said:

The switches on the overhead panel are indeed there only to check the voltage of the emergency batteries. The standby horizon battery has no “on/off control. The battery comes on line automatically if primary aircraft power fails when the aircraft is in air mode (weight off wheels). This can be a “gotcha” during maintenance. If the aircraft is placed on jacks, the WOW sensors will be in air mode. If the aircraft is powered up with a GPU while in this condition, then power is subsequently switched off, the emergency battery will come on to power the standby horizon, which will eventually deplete it if this is not noticed. For this reason, the maintenance manual requires the emergency battery to be disconnected whenever the aircraft is on jacks.

Thanks Jim, that's super info and interesting insight as always.

Al

Edited by ark

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