Run FCS BIT Test...when and why do you run it?

[fitness88]

I don't understand what the FCS BIT Test is about and what the difference is between it and the FCS reset on the left console.

Could someone please explain.

 

Thank you.

[Tholozor]

The FCS BIT runs the exerciser program that actuates all the individual control surfaces to check range of motion, also recommended during cold weather startups to warm up the hydraulic fluid.

 

The FCS Reset button resets the flight control computer. If there are temporary malfunctions, such as before startup when the flaps are in the FULL position due to lack of hydraulic pressure, FCS Reset will clear those malfunctions. Think of it as clearing a Master Caution, but only for the FCS. Resetting the FCS and checking the BLIN codes can help the pilot determine if there will be any addition problems that might occur with the FCS during flight, you can read more about it in the NATOPS.

Edited February 19, 2020 by Tholozor

[dobroDude]

The FCS BIT runs the exerciser program that actuates all the individual control surfaces to check range of motion, also recommended during cold weather startups to warm up the hydraulic fluid.

 

The FCS Reset button resets the flight control computer. If there are temporary malfunctions, such as before startup when the flaps are in the FULL position due to lack of hydraulic pressure, FCS Reset will clear those malfunctions. Think of it as clearing a Master Caution, but only for the FCS. Resetting the FCS and checking the BLIN codes can help the pilot determine if there will be any addition problems that might occur with the FCS during flight, you can read more about it in the NATOPS.

I think you’re combining the exerciser and the FCS BIT. BIT is consent switch + bit button on DDI and exerciser is consent switch + FCS reset button. BIT is NATOPS required after startup to test control surface deflections. Exerciser is to test hyds like in cold weather ops. But it sounds like you hit the nail on the head with FCS reset.

[fitness88]

Tholozor, thanks for the info it helped to clarify

Are the issues that get cleared up from running these commands modelled in the sim?

Is there a list that explains each BLIN code?

 

dobroDude I'll do some more reading on it as I didn't understand what your contradiction was about.

Edited February 19, 2020 by fitness88

[victorlima01]

I've looked for a detailed explanation of the blin codes, their meanings and what actions to take when you get one of these either in flight or on the ground. I failed to find the information however. There is a section covering it in natops but it is unsatisfyingly concise. Maybe its classified information...

[G B]

I've looked for a detailed explanation of the blin codes, their meanings and what actions to take when you get one of these either in flight or on the ground. I failed to find the information however. There is a section covering it in natops but it is unsatisfyingly concise. Maybe its classified information...

 

BLIN is BIT Logic Inspect. These are faults within the FCS. Anything from an aileron servo failure to a degraded NWS motor, to a broken ATC. Even having the wings folded will produce BLINs (not so in the Rhino however). After an FCS IBIT you should have GO on the BIT page and zero BLINs. If you have a BLIN, maintenance troubleshooting is then required. Examples of troubleshooting techniques include running Test Groups (TGs) on the BIT page as mini-IBITs, running the FCS exerciser, cycling the FCS circuit breakers, etc. however, if the BLIN doesn’t clear, the jet is almost certainly down. It is normal to have BLINs immediately after start before you do an FCS reset and IBIT.

[victorlima01]

BLIN is BIT Logic Inspect. These are faults within the FCS. Anything from an aileron servo failure to a degraded NWS motor, to a broken ATC. Even having the wings folded will produce BLINs (not so in the Rhino however). After an FCS IBIT you should have GO on the BIT page and zero BLINs. If you have a BLIN, maintenance troubleshooting is then required. Examples of troubleshooting techniques include running Test Groups (TGs) on the BIT page as mini-IBITs, running the FCS exerciser, cycling the FCS circuit breakers, etc. however, if the BLIN doesn’t clear, the jet is almost certainly down. It is normal to have BLINs immediately after start before you do an FCS reset and IBIT.

 

Thx GB

[fitness88]

BLIN is BIT Logic Inspect. These are faults within the FCS. Anything from an aileron servo failure to a degraded NWS motor, to a broken ATC. Even having the wings folded will produce BLINs (not so in the Rhino however). After an FCS IBIT you should have GO on the BIT page and zero BLINs. If you have a BLIN, maintenance troubleshooting is then required. Examples of troubleshooting techniques include running Test Groups (TGs) on the BIT page as mini-IBITs, running the FCS exerciser, cycling the FCS circuit breakers, etc. however, if the BLIN doesn’t clear, the jet is almost certainly down. It is normal to have BLINs immediately after start before you do an FCS reset and IBIT.

 

Very interesting, thanks.

[fitness88]

If both FCS tests should be run before a flight, which do you run first [bIT or RESET]?

[G B]

If both FCS tests should be run before a flight, which do you run first [bIT or RESET]?

 

The FCS reset happens before the IBIT. Realize the reset is not a test.

[JUICE-AWG]

The FCS reset happens before the IBIT. Realize the reset is not a test.

 

What he said! The RESET resets the FCS, but the Takeoff Trim RESET puts your basic T/O Trim at 12 degrees...and with flaps up, hold Y and hit the FCS BIT Test. Look outside and you'll see all the controls move during the test and you'll hear a sound alert when compete and status should be OK.

 

I have had failures when I started Engine 1 first (Left) instead of the Right engine first.

 

Reminder, you always takeoff with 12 degrees shore base but on the carrier with CAT, you adjust the degrees with trim input based upon total aircraft weight. You won't be able to do this until you lower the flaps to half which is the takeoff position.

 

Hope this helped.

Edited February 19, 2020 by =JUICE=

[fitness88]

Thanks all:book:

[G B]

BLIN is BIT Logic Inspect. These are faults within the FCS. Anything from an aileron servo failure to a degraded NWS motor, to a broken ATC. Even having the wings folded will produce BLINs (not so in the Rhino however). After an FCS IBIT you should have GO on the BIT page and zero BLINs. If you have a BLIN, maintenance troubleshooting is then required. Examples of troubleshooting techniques include running Test Groups (TGs) on the BIT page as mini-IBITs, running the FCS exerciser, cycling the FCS circuit breakers, etc. however, if the BLIN doesn’t clear, the jet is almost certainly down. It is normal to have BLINs immediately after start before you do an FCS reset and IBIT.

 

For clarity I’ll add that if you have BLINs after the IBIT, it’s most likely accompanied by a DEGD instead of a GO after the IBIT is complete.

[Robin_Hood]

After the FCS Reset and before the BIT, there is also a FCS RESET + Paddle switch with flaps in AUTO, although I'm not sure what it does exactly compared to the simple RESET. Also, the FCS BIT is performed with HALF flaps, not AUTO. And FCS BIT should be done with NWS OFF. This is all from the NATOPS.

Oh, and in DCS you always get some BLINs that never go away, so I don't think it is really working at the moment (ust tested, I had 246, 270, 344, 375, 574, 604, 5005, 5037, with a GO for the BIT).

[G B]

After the FCS Reset and before the BIT, there is also a FCS RESET + Paddle switch with flaps in AUTO, although I'm not sure what it does exactly compared to the simple RESET. Also, the FCS BIT is performed with HALF flaps, not AUTO. And FCS BIT should be done with NWS OFF. This is all from the NATOPS.

Oh, and in DCS you always get some BLINs that never go away, so I don't think it is really working at the moment (ust tested, I had 246, 270, 344, 375, 574, 604, 5005, 5037, with a GO for the BIT).

 

Paddle Switch + Reset clears the BLINs to zero out. It doesn’t actually solve the problems. Fun fact, the IBIT is done in AUTO in the Super Hornet.

[randomTOTEN]

There's some very good insight into the FCS, G B.. thanks for sharing.

[Browny]

I'm ex-Aussie Air Force and I worked on Hornets for a few years.

 

We'd sometimes get a few FCS BLINs on startup and there's a few different extra tests that you can advise the pilot to do to help clear/isolate the fault. There's separate manuals for the FCS and Fault Isolation, that's when you'd use your BLINs. When I was running the flight line desk and launching jets it was procedure to have these 2 manuals opened and ready to access quickly.

 

As for the FCS exerciser, we would always try to fault find a jet with FCS problems as soon as possible after it had shut down. That way the FCS and Hyd fluid is still warm. The FCS exerciser was used if you had a cold jet and you needed to get everything warmed up to operating temperatures.

 

You could always expect FCS faults after the pilots had been doing BFM lol.

[Harker]

You could always expect FCS faults after the pilots had been doing BFM lol.

Why? How does BFM differ from normal flight, as far as the FCS is concerned? Does it have to do with the fact that the jet is operating in high AOA values, high Gs, weird bank angles etc? Is the FCS producing/accumulating faults because it's trying to keep the jet steady through all of this?

Thanks for sharing, btw!

[G B]

Why? How does BFM differ from normal flight, as far as the FCS is concerned? Does it have to do with the fact that the jet is operating in high AOA values, high Gs, weird bank angles etc? Is the FCS producing/accumulating faults because it's trying to keep the jet steady through all of this?

Thanks for sharing, btw!

 

I haven’t seen that happen after BFM in US Hornets.

[did]

I could talk for hours on why and how FCS get degraded. 20 years on first line desanging and 4+ years working on servo fix secound line

 

[normanleto]

BUT: is this all required in the sim? Are BITs and failures currently recreated?

[Repth]

They can be. Random failures are an option if one chooses to enable them. For the aircraft that have them you can even set the probability that the failure will occur. Even without them enabled, some people will still go thru the checklist and run checks because they like to simulate it. It's nice to see it work properly for those who decide to take the time to do so.

[oldcrusty]

Something for everyone. Switch flipping fanatics... let them have their switches, gamers or tactical folks... start on the runway. Realism freaks... follow the book from the time you get in the ready room.

I haven't done a cold start in months then sooner or later I'll catch the NATOPS fever and keep it open on every DCS session, until...

It's good to know though that most of the stuff is or will be modeled.

[dorianR666]

6 hours ago, normanleto said:

Are BITs and failures currently recreated?

no

hopefully one day BITs will actually be implemented

[Swift.]

12 hours ago, dorianR666 said:

no

hopefully one day BITs will actually be implemented

Some of the BITs work, they startup BIT behaviour is all goofed though. So for now all you can do is just manually run them and have fun.